2022.06.17

2021 (Ju) 342

Minshu Vol. 76, No. 5

Judgment concerning the case in which the court determined that the State is not considered to assume the responsibility to compensate loss or damage under Article 1, paragraph (1) of the State Redress Act on the grounds of its failure to exercise the regulatory authority under Article 40 of the Electricity Business Act (prior to amendment by Act No. 47 of 2012) for the purpose of preventing an accident at a nuclear power plant due to a tsunami

Case seeking restoration, etc.

Judgment of the Second Petty Bench, quashed and decided by the Supreme Court

Sendai High Court, Judgment of September 30, 2020

In the case where as a result of a tsunami associated with an earthquake that arrived at the site of the buildings related to the nuclear reactors of a nuclear power plant that were installed and operated by an electric power company, seawater entered the aforementioned buildings and nuclear reactor facilities related to the aforementioned nuclear reactors lost their power source, thus causing the occurrence of a nuclear accident in which a large amount of radioactive materials was released from the aforementioned nuclear reactor facilities, under the circumstances held in this judgment, including those mentioned in (1) to (6) below, it cannot be found that there is a causal relationship in which if the Minister of Economy, Trade and Industry had exercised the regulatory authority under Article 40 of the Electricity Business Act (prior to amendment by Act No. 47 of 2012) on the premise of a document on the long-term assessment of seismic activities in the sea area including the offing of the aforementioned power plant and had obliged the aforementioned electric power company to take appropriate measures to prevent the aforementioned nuclear power plant accident that was caused by a tsunami, the nuclear power plant accident or an accident similar thereto would not have occurred, and it cannot be said that the State assumes the responsibility to compensate loss or damage under Article 1, paragraph (1) of the State Redress Act for persons whose places of residence of the time were contaminated by radioactive materials released due to the aforementioned nuclear accident on the grounds that the Minister of Economy, Trade and Industry did not exercise the aforementioned regulatory authority.

(1) Measures against tsunamis for nuclear reactor facilities in Japan prior to the aforementioned nuclear accident were based on the idea of assuming that the sites of nuclear reactor facilities where safety facilities, etc. are installed might be flooded due to a tsunami, and were intended to prevent seawater from entering the sites in such cases by way of installing structures, such as a seawall and breakwater.

(2) It does not appear that the following idea was dominant before the aforementioned nuclear accident: if a site as mentioned above is assumed to be flooded due to a tsunami, installation of structures, such as a seawall and breakwater, which are designed to prevent the site from being flooded due to an assumed tsunami is insufficient as a measure for preventing the site from being flooded. There is no other circumstance where the aforementioned measure should be considered to have been insufficient as a measure against tsunamis for nuclear reactor facilities based on knowledge before the aforementioned nuclear accident.

(3) The estimation of a tsunami that may arrive at the aforementioned power plant, which was made based on the aforementioned document through entrustment by the aforementioned electric power company before the aforementioned nuclear accident, was a reasonable estimation that had a margin with sufficient attention to safety, corresponding to the worst scenario imaginable of the time.

(4) While the tsunami magnitude of an earthquake that was expected to occur in the future in the aforementioned document, was around 8.2, that of the earthquake that actually occurred was 9.1.

(5) While the depth of flooding due to the aforementioned estimated tsunami near the aforementioned buildings was assumed to be about 2.6 m or less, the depth of flooding due to the tsunami that actually arrived near the buildings reached up to about 5.5 m.

(6) Although the height of the aforementioned estimated tsunami exceeded the height of the site of the aforementioned buildings on the southeast front of the site, it never exceeded the height of the site on the east front thereof. It was thus not assumed that seawater would enter the site from the east side of the site even in the case where a tsunami with the same size as the aforementioned tsunami arrived at the aforementioned power plant. However, in fact, with the arrival of the tsunami, a large volume of seawater entered the site not only from the southeast side of the site but also from the east side thereof.

(There are concurring opinions and a dissenting opinion.)

Article 1, paragraph (1) of the State Redress Act and Article 39, paragraph (1) and Article 40 of the Electricity Business Act (prior to amendment by Act No. 47 of 2012)

State Redress Act
Article 1(1)　When a public employee who exercises the public authority of the State or of a public entity has, in the course of their duties, unlawfully caused loss or damage to another person intentionally or negligently, the State or public entity assumes the responsibility to compensate therefor.

Electricity Business Act
(Maintenance of Electric Facilities for Business Use)
Article 39(1)　A person who installs Electric Facilities for Business Use must maintain the Electric Facilities for Business Use to ensure that they conform to the technical standards established by Ordinance of the Ministry of Economy, Trade and Industry.

(Order for Conformity to Technical Standards)
Article 40　The Minister of Economy, Trade and Industry may, when they find that Electric Facilities for Business Use do not conform to the technical standards established by Ordinance of the Ministry of Economy, Trade and Industry under paragraph (1) of the preceding Article, order the person who installs the Electric Facilities for Business Use to repair or alter the Electric Facilities for Business Use to ensure conformity to the technical standards, or order the person to relocate the facilities or suspend the use of them, or restrict the person from using the facilities.

1. Of the judgment in prior instance, the part concerning claims for compensation for loss or damage made by the appellees of final appeal stated in List of Appellees 1 attached to this judgment against the appellant of final appeal is quashed, and the judgment in first instance is revoked with regard to the same part.

2. All the actions filed by the appellees stated in List of Appellees 1 attached to this judgment regarding the part revoked in the preceding paragraph are dismissed without prejudice.

3. Of the judgment in prior instance, the part against the appellant is quashed with regard to the claims against the appellant made by the appellees stated in Lists of Appellees 2 to 6 attached to this judgment.

4. With regard to the part stated in the preceding paragraph, of the judgment in first instance, the part against the appellant regarding the claims of the appellees stated in Lists of Appellees 2 to 4 attached to this judgment is revoked, and all the claims of the same appellees regarding the same part are dismissed with prejudice on the merits.

5. With regard to the part stated in paragraph 3, the appeals to the court of second instance filed by the appellees stated in Lists of Appellees 2, 3, 5, and 6 attached to this judgment are dismissed with prejudice on the merits.

6. With regard to the part stated in paragraph 3, all additional claims made in prior instance by the appellees stated in Lists of Appellees 2 and 5 attached to this judgment are dismissed with prejudice on the merits.

7. The total court costs shall be borne by the appellees.

No. 1 Outline of the case

1. The appellees are persons who argue that their places of residence of the time were contaminated by radioactive materials that were released due to an accident (hereinafter referred to as the "Accident") at the Fukushima Daiichi Nuclear Power Station (hereinafter referred to as the "Power Station") of Tokyo Electric Power Company Holdings, Inc. (the trade name of the time was Tokyo Electric Power Company, Inc.; hereinafter referred to as "TEPCO") in association with the occurrence of the 2011 off the Pacific Coast of Tohoku Earthquake (hereinafter referred to as the "Earthquake") on March 11, 2011 or the successors of these persons. In this case, the appellees argue that the appellant failed to exercise the regulatory authority under the Electricity Business Act (prior to amendment by Act No. 47 of 2012; the same applies hereinafter) to prevent the occurrence of an accident at the Power Station due to a tsunami and that this failure is illegal and appellees suffered loss or damage due to this failure. Based on this argument, the appellees claim compensation for loss or damage against the appellant under Article 1, paragraph (1) of the State Redress Act, and also demand that the space radiation dose rate at their places of residence of the time of the Accident be reduced to 0.04 μSv or less per hour as a claim for restoration based on the moral right or under the same paragraph.

2. The outline of facts lawfully determined by the court of prior instance is as follows.

(1) Outline of the Power Station

A. The Power Station is a nuclear power plant installed and operated by TEPCO, and it is located in area spanning Futaba-machi and Okuma-machi in Futaba-gun, Fukushima Prefecture.

B. Six nuclear reactors, Units 1 to 6, whose operation was started in sequence during the period from 1971 and 1979, are installed at the Power Station, and all the nuclear reactors are boiling light-water reactors. The nuclear reactor facilities of the Power Station consist of nuclear reactor buildings that house nuclear reactor containment vessels, turbine buildings that house steam turbines, etc.

C. All main buildings (hereinafter referred to as the "main buildings") pertaining to the nuclear reactors, Units 1 to 4, of the Power Station (hereinafter collectively referred to as the "Nuclear Reactors"), such as nuclear reactor buildings and turbine buildings, are located on flat land 10 m above sea level (hereinafter height above sea level is based on the datum level for construction at Onahama Port), and the Nuclear Reactors, Units 1 to 4, are installed in line in ascending order from north to south (hereinafter the site of the main buildings is referred to as the "Site"). The east and southeast sides of the Site face the sea across a section 4 m above sea level where pumps for lifting seawater and other facilities are installed.

D. Although electricity generated through operation of nuclear reactors and electricity supplied from external substations was used at the nuclear reactor facilities related to the Nuclear Reactors (hereinafter referred to as the "Nuclear Reactor Facilities"), in case all of these kinds of electricity is unavailable, emergency diesel generators and electric facilities for supplying electricity generated thereby to other facilities (hereinafter collectively referred to as the "Emergency Power Systems") were installed in the main buildings.

(2) Preparation of a report on the method of assessing the water level of a design tsunami for nuclear power plants

In February 2002, the Tsunami Evaluation Subcommittee, which was established under the Nuclear Civil Engineering Committee of the Japan Society of Civil Engineers, prepared a report titled "Tsunami Assessment Method for Nuclear Power Plants in Japan" (hereinafter referred to as the "2002 Tsunami Assessment Method") as a document that indicates the method of assessing the water level of a design tsunami for nuclear power plants. In the 2002 Tsunami Assessment Method, regarding tsunamis associated with plate boundary earthquakes, a previous tsunami considered to have had the most impact on the target site was selected, a standard fault model was set based on a fault model by which the watermark height of the previous tsunami on the coast could be best explained. Then, numerous numerical calculations were carried out while changing various conditions of the standard fault model within a range considered reasonable in order to reflect the uncertainties of a scenario tsunami on the water level of the design tsunami, and the water level of the design tsunami was thereby obtained based on the tsunami that would have the most impact on the target site.

(3) Publication of a document summarizing the long-term assessment of seismic activities in the area from the offing of Sanriku to the offing of Boso

The Earthquake Research Committee of the Headquarters for Earthquake Research Promotion is an organization established in the Ministry of Education, Culture, Sports, Science and Technology based on the Act on Special Measures concerning Earthquake Disaster Management, and it consists of members who are appointed by the Minister of Education, Culture, Sports, Science and Technology from the employees of relevant administrative organs and persons with relevant expertise. In July 2002, the committee published a document titled "Long-Term Assessment of Seismic Activities in the Area from the Offing of Sanriku to the Offing of Boso" (hereinafter referred to as the "Long-Term Assessment") as a document summarizing assessments on the possibility of occurrence of earthquakes in the area along the Japan Trench extending from the offing of Sanriku to the offing of Boso from a long-term perspective and the topography of the source area, etc. The Long-Term Assessment contained the following: the possibility that an earthquake similar to the Meiji Sanriku Earthquake that occurred in 1896 may occur anywhere within the area that is elongated from north to south near the Japan Trench extending from the north part of the offing of Sanriku to the offing of Boso in the aforementioned area along the Japan Trench; the possibility of occurrence of a large magnitude 8-class interplate earthquake (tsunami earthquake) in the aforementioned area with a probability of around 20% within the next 30 years, and with a probability of around 30% within the next 50 years; and the earthquake being estimated to be of a size accompanied by a tsunami magnitude of around 8.2.

(4) Formulation of the Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities

A. In September 2006, the Nuclear Safety Commission formulated the "Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities" with the aim of showing a basis for determining the adequacy of seismic design policies from the standpoint of ensuring seismic safety within safety review pertaining to applications for permission for installation of light-water nuclear power reactors and applications for permission for change thereof. The aforementioned guide stated that light-water nuclear power reactor facilities must be designed with sufficient consideration given to ensure that their safety functions are not likely to be significantly affected by a tsunami that is appropriately assumed to be likely to occur in the operational period of the facilities though its occurrence is supposed to be extremely rare.

B. In September 2006, the Nuclear and Industrial Safety Agency instructed persons who had installed nuclear power reactor facilities: including TEPCO, to conduct assessment of the seismic safety of existing nuclear power reactor facilities, etc. in light of the aforementioned guide.

(5) Estimation of a tsunami based on the Long-Term Assessment

A. In response to the aforementioned instruction, TEPCO entrusted its affiliated company to assess a tsunami that would be likely to arrive at the Power Station based on the Long-Term Assessment and received a report on the results of the assessment around April 2008. The content of the report was as follows: a fault model of the Meiji Sanriku Earthquake was set in the area near the Japan Trench from the offing of Fukushima Prefecture to the offing of Boso based on the Long-Term Assessment, and a tsunami was estimated by carrying out numerous numerical calculations while changing various conditions of the fault model within a range considered reasonable in accordance with the method of assessing the water level of a design tsunami indicated in the 2002 Tsunami Assessment Method; as a result, a tsunami whose wave was the highest in the east and southeast fronts of the Site facing the sea was up to 15.707 m above sea level in the southeast front of the Site but did not exceed the height of the Site (10 m above sea level) in the east front of the Site; the depth of flooding near the main buildings was about 2.6 m near the nuclear reactor building of Unit 4 and about 2.0 m near the turbine building of Unit 4 (hereinafter this estimation is referred to as the "Estimation," and this estimated tsunami is referred to as the "Estimated Tsunami").

B. After that, TEPCO examined measures, etc. against a tsunami with the same size as the Estimated Tsunami. However, it ended the examination during the examination period by deciding not to immediately take measures but to entrust research on the Long-Term Assessment to the Japan Society of Civil Engineers.

(6) The Earthquake and the Accident associated with it

A. On March 11, 2011, the Earthquake occurred with its seismic source at a spot about 130 km east-southeast of the Oshika Peninsula and about 24 km in depth. The Earthquake occurred as a result of the interlocking of multiple seismic sources, and its source area extended about 450 km in length from north to south and about 200 km in width from east to west, and its maximum slippage was 50 m or more. Regarding the size of the Earthquake, its magnitude and tsunami magnitude were the largest ever recorded in Japan, specifically, 9.0 and 9.1.

B. Due to the Earthquake, all the Nuclear Reactors, except for Unit 4 that was being shut down for regular inspection, were automatically shut down, and electricity supply from external substations was also stopped due to equipment failure, etc. caused by the Earthquake.

After that, a tsunami associated with the Earthquake (hereinafter referred to as the "Tsunami") arrived at the Power Station, and a large amount of seawater entered the Site from multiple directions on the east and southeast sides of the Site facing the sea. Thereby, almost the entire area of the Site was flooded. The depth of flooding reached up to about 5.5 m near the main buildings, and seawater entered the main buildings. As a result, all the Emergency Power Systems were flooded and lost their functions, which caused the complete loss of AC power sources.

The Nuclear Reactor Facilities had DC power systems with storage batteries. However, at the nuclear reactor facilities pertaining to the nuclear reactors, except for Unit 3, the aforementioned power systems were also flooded and lost their functions, and all the power sources, including DC power sources, were lost. At the nuclear reactor facility of Unit 3, DC power from the aforementioned storage battery was temporarily supplied to the emergency core cooling system. However, the emergency core cooling system stopped, and it became impossible to restart the system due to insufficient level of the remaining life of the storage battery.

As mentioned above, as a result of the Nuclear Reactor Facilities having lost all power sources, regarding the nuclear reactors Units 1 to 3, which were in operation at the time of occurrence of the Earthquake, it became impossible to cool the cores that continued to produce heat even after the shut-down of the reactors. Fuel that reached a high temperature was badly damaged, and the nuclear reactor buildings, etc. were damaged by explosions of hydrogen gas generated thereby. This led to the occurrence of an accident in which a large amount of radioactive material was released from the Nuclear Reactor Facilities (the Accident).

(7) Measures against tsunamis for nuclear reactor facilities in Japan before the Accident

Measures against tsunamis for nuclear reactor facilities in Japan before the Accident were based on the idea of preventing the sites of nuclear reactor facilities where safety facilities, etc. are installed from being flooded by such means as locating those sites at places higher than the water levels of tsunamis that are assumed to occur. The basis of the measures was to prevent seawater from entering the aforementioned sites by installing structures, such as a seawall and breakwater (hereinafter referred to as a "seawall, etc.") if the sites were assumed to be flooded due to a tsunami.

(8) Provisions of relevant laws and regulations

Article 39, paragraph (1) of the Electricity Business Act provides that a person that installs electric facilities for business use must maintain the facilities to ensure that they conform to the technical standards established by Order of the Ministry of Economy, Trade and Industry. Article 40 of the same Act provides that if the Minister of Economy, Trade and Industry finds that electric facilities for business use do not conform to the aforementioned technical standards, the Minister may order the person that installs the electric facilities for business use to repair or alter the facilities to ensure conformity to the technical standards, or order the person to relocate the facilities or suspend their use, or restrict the person from using the facilities.

In response to these provisions, Article 4, paragraph (1) of the Ministerial Order to Provide Technical Standards for Nuclear Facilities for Power Generation prior to amendment by Order of the Ministry of Economy, Trade and Industry No. 68 of 2005 provides that if a nuclear reactor facility, etc. is likely to be damaged by a tsunami, etc., it is necessary to take appropriate measures, such as installation of protection facilities. The same paragraph after the aforementioned amendment provides that if safety of a nuclear reactor is likely to be impaired due to a natural phenomenon: such as a tsunami that is assumed to occur, it is necessary to take appropriate measures, such as protective measures.

(9) The appellees' arguments in this action

In this action, the appellees argue as follows: after the publication of the Long-Term Assessment, the Minister of Economy, Trade and Industry could have foreseen that a tsunami with a height exceeding the height of the Site might arrive at the Power Station by estimating a tsunami based on the Long-Term Assessment on a timely basis; therefore, the Minister should have exercised the regulatory authority under Article 40 of the Electricity Business Act and obliged TEPCO to take appropriate measures to prevent the occurrence of an accident at the Power Station due to a tsunami; if the Minister had done so, an accident causing the release of a large amount of radioactive materials from the Nuclear Reactor Facilities in the same manner as the Accident would not have occurred.

3. Based on the aforementioned factual relationships, the court of prior instance determined as summarized below and ruled that the whole or part of the appellees' claims for compensation for loss or damage against the appellant should be upheld.

After the publication of the Long-Term Assessment, the Minister of Economy, Trade and Industry could have foreseen that a tsunami with a height exceeding the height of the Site might arrive at the Power Station by the end of 2002 at the latest by estimating a tsunami based on the Long-Term Assessment through guidance to TEPCO or by other means. Then, while the appellees argued and proved measures to prevent accidents that were concretely specified to a certain extent with regard to a tsunami that the Minister of Economy, Trade and Industry could have foreseen, the appellant has neither argued nor proven facts, such as that the occurrence of an accident similar to the Accident could not have been avoided even if measures argued and proven by the appellees had been taken, based on reasonable grounds and materials. Then, it should be said that in this case, existence of a relation in which if the Minister of Economy, Trade and Industry had exercised the regulatory authority under Article 40 of the Electricity Business Act and obliged TEPCO to take appropriate measures to prevent the occurrence of an accident at the Power Station due to a tsunami, an accident similar to the Accident would not have occurred is virtually recognized through presumption. Taking these circumstances, etc. into account, the Minister of Economy, Trade and Industry should have exercised the aforementioned regulatory authority by the end of 2006 at the latest, and the minister's failure to exercise the regulatory authority at the end of 2006 and thereafter is illegal in terms of the application of Article 1, paragraph (1) of the State Redress Act, and a causal relationship is also recognized between this failure to exercise the regulatory authority and the Accident. Therefore, the appellant is not exempted from the responsibility to compensate loss or damage under the same paragraph.

No. 2 Consideration by the court's authority

According to the case records, in 2013, the appellees stated in List of Appellees 1 attached to this judgment filed an action to seek compensation for loss or damage due to the Accident (hereinafter referred to as the "separate action") against the appellant with the Niigata District Court under Article 1, paragraph (1) of the State Redress Act. The separate action had already been pending before the aforementioned court at the time when the aforementioned appellees filed this action, and in this action, the part pertaining to the aforementioned appellees' claims for compensation for loss or damage against the appellant is found to overlap with the separate action. Then, the appellees' action pertaining to the aforementioned claims is unlawful (Article 142 of the Code of Civil Procedure) and should be dismissed without prejudice. The judgment in prior instance that made a determination on the merits in relation to the aforementioned claims differing from the above contains a violation of laws and regulations that has clearly influenced the judgment.

Therefore, of the judgment in prior instance, the part concerning the aforementioned claims should inevitably be quashed, and regarding the same part, the judgment in first instance shall be revoked and the aforementioned appellees' action shall be dismissed without prejudice with regard to the same part.

No. 3 Concerning the reasons for a petition for acceptance of final appeal stated by the counsel for final appeal, MUKASA Keiji, et al. (except for the reasons excluded)

1. The determination of the court of prior instance stated in No. 1, 3. above cannot be upheld for the following reasons.

(1) If a failure to exercise the regulatory authority by a public employee of the State or a public entity is found to go beyond the permissible limits and be extremely unreasonable under specific circumstances in light of the purport and purpose of laws and regulations that provide for the authority and the nature, etc. of the authority, it is reasonable to consider that the failure to exercise is illegal in terms of the application of Article 1, paragraph (1) of the State Redress Act in relation to persons who suffered damage from the failure to exercise (see 2001 (Ju) 1760, the judgment of the Third Petty Bench of the Supreme Court of April 27, 2004, Minshu Vol. 58, No. 4, at 1032, 2018 (Ju) 1447, 1448, 1449, 1451, and 1452, the judgment of the First Petty Bench of the Supreme Court of May 17, 2021, Minshu Vol. 75, No. 5, at 1359, etc.). Then, in order to say that the State or a public entity assumes the responsibility to compensate loss or damage under the same paragraph on the grounds of the aforementioned public employee's failure to exercise the regulatory authority, a relationship in which if the public employee had exercised the regulatory authority, the aforementioned persons would not have suffered damage must be found. Therefore, this point is examined.

(2) According to the aforementioned factual relationships, measures against tsunamis for nuclear reactor facilities in Japan before the Accident were based on the idea of preventing seawater from entering the sites of nuclear reactor facilities wherein safety facilities, etc. are installed by installing a seawall, etc. if the sites are assumed to be at risk of being flooded due to a tsunami. Therefore, it can be said that if the Minister of Economy, Trade and Industry had exercised the regulatory authority under Article 40 of the Electricity Business Act and obliged TEPCO to take appropriate measures to prevent the occurrence of an accident at the Power Station due to a tsunami on the premise of the Long-Term Assessment, it can be said to be highly probable that TEPCO would have taken a measure, specifically, installation of a seawall, etc. that was designed to prevent seawater from entering the Site even in the event of the arrival of the maximum tsunami that was assumed based on the Long-Term Assessment. In the Estimation, a tsunami with the highest height in the east and southeast fronts of the Site facing the sea was estimated by setting the fault model of the Meiji Sanriku Earthquake: for which the Long-Term Assessment concluded that a similar earthquake might occur in the future, in the area close to the Japan Trench in the offing of Fukushima Prefecture, etc., and carrying numerous numerical calculations in accordance with the method of assessing the water level of a design tsunami indicated in the 2002 Tsunami Assessment Method while changing various conditions of the fault model within a range considered reasonable. The Estimation can be considered to be a reasonable estimation that had a margin with sufficient attention to safety, corresponding to the worst scenario imaginable of the time.

Then, it can be said that if the Minister of Economy, Trade and Industry had exercised the aforementioned regulatory authority, a measure, specifically, installation of a seawall, etc. that was designed to prevent seawater from entering the Site due to a tsunami with the same size as the Estimated Tsunami would have probably been taken.

On the other hand, it does not appear that the following idea was dominant before the Accident: in the case where a site of nuclear reactor facilities wherein safety facilities, etc. are installed is assumed to be flooded due to a tsunami, it is not sufficient as a countermeasure to merely install a seawall, etc. that is designed to prevent the site from being flooded due to a tsunami that is assumed to occur. There is no other circumstance where the aforementioned measure should be considered to have been insufficient as a measure against tsunamis for nuclear reactor facilities based on knowledge before the Accident. Therefore, it cannot be said that if the Minister of Economy, Trade and Industry had exercised the aforementioned regulatory authority before the Accident, other measures would have probably been taken in addition to installation of a seawall, etc. that was designed to prevent the Site from being flooded due to a tsunami with the same size as the Estimated Tsunami or that such measures would have had to be taken.

(3) However, while the size of an earthquake which the Long-Term Assessment considered to be likely to occur in the future was around tsunami magnitude 8.2, the size of the Earthquake was tsunami magnitude 9.1, and the Earthquake was far larger in size than the earthquake that was assumed to occur based on the Long-Term Assessment. In addition, while the depth of flooding near the main buildings due to the Estimated Tsunami was about 2.6 m or less, the depth of flooding near the main buildings due to the Tsunami reached up to about 5.5 m. Then, the height of the Estimated Tsunami exceeded the height of the Site in the southeast front thereof but never exceeded the height of the Site in the east front thereof, and it was not assumed that seawater would enter the Site from the east side of the Site even in the event of a tsunami with the same size as the Estimated Tsunami. However, in fact, with the arrival of the Tsunami, a large volume of seawater entered the Site not only from the southeast side of the Site but also from the east side thereof.

In light of these circumstances, it must be said that a seawall, etc. that was designed to have a structure to prevent seawater from entering the Site due to a tsunami with the same size as the Estimated Tsunami was likely to be one with the focus placed on preventing seawater from entering the Site from the southeast side thereof and was unlikely to one that could prevent a large amount of seawater from entering the Site in association with the arrival of the Tsunami even in consideration of the fact that it would be designed to have a certain margin.

(4) For the reasons described above, even if the Minister of Economy, Trade and Industry had exercised the regulatory authority under Article 40 of the Electricity Business Act and obliged TEPCO to take appropriate measures to prevent the occurrence of an accident at the Power Station due to a tsunami on the premise of the Long-Term Assessment and TEPCO had performed that obligation, it would have been highly likely to be impossible to avoid a large amount of seawater entering the Site in association with the arrival of the Tsunami, and it must be said that there is a considerable possibility that an accident similar to the Accident would have occurred as a result of the Nuclear Reactor Facilities having lost power sources due to loss of functions of the Emergency Power Systems due to flooding caused by the entry of a large amount of seawater into the main buildings.

Then, based on the facts of this case, it is impossible to find a relationship where if the Minister of Economy, Trade and Industry had exercised the aforementioned regulatory authority, the Accident or an accident similar thereto would not have occurred.

(5) On the other hand, the court of prior instance states that existence of the aforementioned relationship is virtually recognized through presumption in this case, but it is impossible to say so based on the factual relationships of this case as explained above.

(6) Therefore, it cannot be said that the appellant assumes the responsibility to compensate loss or damage under Article 1, paragraph (1) of the State Redress Act in relation to the appellees on the grounds that the Minister of Economy, Trade and Industry did not oblige TEPCO to take appropriate measures to prevent the occurrence of an accident at the Power Station due to a tsunami by exercising the regulatory authority under Article 40 of the Electricity Business Act.

2. The determination of the court of prior instance that differs from the above contains a violation of laws and regulations that has clearly influenced the judgment. The counsel's arguments are well-grounded, and of the judgment in prior instance, the part against the appellant regarding the claims against the appellant for compensation for loss or damage of the appellees stated in Lists of Appellees 2 to 6 attached to this judgment should inevitably be quashed. Then, according to the explanation above, the aforementioned claims are groundless, and therefore, regarding the aforementioned quashed part, of the judgment in first instance, the part against the appellant regarding the claims of the appellees stated in Lists of Appellees 2 to 4 attached to this judgment should be revoked, and all the claims of the same appellees regarding the same part should be dismissed with prejudice on the merits. The appeals to the court of second instance filed by the appellees stated in Lists of Appellees 2, 3, 5, and 6 attached to this judgment should be dismissed with prejudice on the merits, and all the additional claims made in prior instance by the appellees stated in Lists of Appellees 2 and 5 attached to this judgment should be dismissed with prejudice on the merits.

Accordingly, the Court unanimously decides as set forth in the main text of the judgment, except for the dissenting opinion stated by Justice MIURA Mamoru regarding No. 3 in the holding. Incidentally, there are concurring opinions stated by Justice KANNO Hiroyuki and Justice KUSANO Koichi, respectively, regarding No. 3 in the holding.

The concurring opinion stated by Justice KANNO Hiroyuki is as follows.

I would like to state my concurring opinion with regard to the purport based on which I reached the conclusion of the majority opinion.

1. The 2011 off the Pacific Coast of Tohoku Earthquake occurred at 2:46 p.m. on March 11, 2011 with its seismic source at a spot about 130 km east-southeast of the Oshika Peninsula. The magnitude and tsunami magnitude of the earthquake reached 9.0 and 9.1, and the earthquake was a sort of super great earthquake. The Tsunami triggered by the Earthquake caused a major disaster that should be considered to be the worst in the postwar period and brought unprecedented damage, caused quite a lot of people to die or go missing, and produced many tragic disaster victims mainly in Iwate Prefecture, Miyagi Prefecture, and Fukushima Prefecture. The Tsunami also hit the Fukushima Daiichi Nuclear Power Station installed and operated by TEPCO and caused the occurrence of a major accident that Japan had never experienced, in which a large amount of radioactive material was released from Units 1 to 4 of the Power Station. Although there has been no report of death of a resident due to radiation exposure, a huge number of residents were forced to evacuate, and not a few disaster victims lost their lives during the evacuation. In addition, psychological damage and property loss or damage, including loss of a house and job, destruction of livelihood, and loss of ties to a school, community, etc., due to the evacuation have become enormous to an unprecedented extent in Japan, and relief therefor is still a big issue.

2. The issue of this case is compensation for the aforementioned loss or damage due to the Accident. However, I basically think as follows: although nuclear power generation involves a risk, it has been promoted by the whole nation as being essential for energy policy, science and technology promotion policy, etc.; each electric power company has obtained permission for installation of nuclear power reactors, built nuclear power plants in accordance with various standards set by the State, and maintained nuclear power reactors in accordance with the State's policy under relevant laws and regulations (the Atomic Energy Basic Act, the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors, the Electricity Business Act, the Ministerial Order to Provide Technical Standards for Nuclear Facilities for Power Generation, etc.); therefore, if a large-scale disaster like the Accident occurs, the State should bear the consequences thereof to a greater extent than electric power companies; originally, the State should assume the greatest share of responsibility for relief for victims, regardless of negligence, etc.; as long as nuclear power generation business has been conducted under laws and regulations as the State's policy, regarding large-scale disasters caused thereby, specific persons who became victims should not be left to bear the burden alone, but the State should assume the responsibility for compensation in accordance with the idea of compensation for loss; and this eventually leads to the sharing of compensation by the people in general who are the beneficiaries of electric power and who form the substance of the State.

For that reason, the Act on Compensation for Nuclear Damage (hereinafter referred to as the "Nuclear Compensation Act") was established as a mechanism similar to the concept above. Regarding nuclear damage, with the idea that it is sometimes difficult to prove the fulfillment of requirements for a tort, the Nuclear Compensation Act provides for nuclear operators' strict liability, etc. in Article 3, obliges nuclear operators to take measures to compensate nuclear damage, such as conclusion of a liability insurance contract and deposit with an official depository (120 billion yen per place of business) in Article 6 and thereafter, and also establishes provisions, such as those stipulating that if the amount for which a nuclear operator assumes the responsibility to compensate loss or damage exceeds the amount of the aforementioned insurance, etc. and it is found necessary to achieve the purpose of the Nuclear Compensation Act, the State is to provide the nuclear operator with necessary assistance to compensate loss or damage, in Article 16 and thereafter. After the Accident, the Nuclear Damage Compensation Facilitation Corporation (the current name is the "Nuclear Damage Compensation and Decommissioning Facilitation Corporation") was established, and through the same corporation, the State already provided financial assistance amounting to about 10 trillion yen to TEPCO, and payments, etc. to victims were implemented thereby. In addition, the State has promoted efforts for the reconstruction of disaster-stricken areas by such means as establishing the Reconstruction Agency.

3. However, a determination under the State Redress Act, which is the issue of this case, is an issue that is different from relief for disaster victims deriving from the Nuclear Compensation Act, etc. as mentioned above. The State Redress Act provides that the State is also to assume tort liability, or to put it simply, the State Redress Act has the State compensate loss or damage that has arisen from an act that is prohibited in light of laws and regulations, standards, circumstances, etc. of the time (in the case of inaction, a failure to conduct an act that must be conducted) in the same manner as ordinary tort law.

When this is applied to this case, at present, responses to tsunamis not only depend on the idea of not allowing sites to be flooded by means of securing the height of the sites and installing a seawall, breakwater, etc. (dry site concept) but also include various efforts, such as considering multi-layered protection, including protective measures in anticipation of flooding, such as water-tightening of facilities, and considering severe accident measures for tsunamis. However, these efforts are as the result of the change and development of regulatory levels and technical levels using the Accident as a lesson. Before the Accident, as reasonable and assured measures against tsunamis, it was considered to be a proper technical level to prevent sites from being flooded by installing a seawall, breakwater, etc. based on the aforementioned dry site concept. Although a tsunami that was assumed to occur based on the Long-Term Assessment was of a considerably large size, there was no circumstance hinting that that size of tsunami might not be coped with through installing a seawall, etc. as mentioned above, and it is clear from the holding of the majority opinion that it is difficult to find that there was a protective measure that was considered to be more certain than installation of a seawall, etc. based on knowledge before the Accident. Therefore, it cannot be said that protective measures other than installation of a seawall, etc. needed to have been taken as measures against tsunamis on the premise of the Long-Term Assessment and that there is a probability that such protective measures would have been taken.

Incidentally, regarding the argument that other protective measures should have been taken in addition to installation of a seawall, etc. with emphasis on the difficulty in predicting tsunamis that will occur in the future and the uncertainties involved in measures against tsunamis, it does not appear that there were any experts, etc. who had seriously made such argument before the Accident, and thus, the argument must be considered to be one that is based on the current knowledge that developed after the Accident. In addition, some may insist that it is not permissible to leave vulnerability of the facilities to flooding as it is until a seawall, etc. is completed and that it was probably necessary to take a water-tightening measure for the facilities during this period. However, it does not appear that there was expert knowledge before the Accident that a water-tightening measure for facilities can be a reliable measure against tsunamis. Therefore, it is difficult to say that such measure should have been taken or was probably taken though it is not determined that such measure will surely eliminate the aforementioned vulnerability. As responses to the aforementioned vulnerability, suspension of the operation of nuclear reactors until a seawall, etc. is completed and acceleration of construction for installation of a seawall, etc. will be considered.

Certainly, the Accident caused serious and enormous damage. However, even if damage is serious and enormous, it is not reasonable to elicit the determination that the State is found to assume the responsibility to compensate loss or damage because it was possible to prevent the Accident if the State had taken the measure, based on the assumption of a protective measure that had never been adopted as a main measure against tsunamis and had been hardly discussed before the Accident.

In a more familiar example, the logic mentioned above can be explained as follows: even if a medical accident or railway accident, etc. that caused a disastrous consequence occurred and verification after the accident revealed the probability that the accident would not have occurred if a specific medical measure or safety equipment had been available, if there were neither grounds under laws and regulations nor medical or technical standards for such medical measure or safety equipment (for example, cases such as where that measure has not been taken at other hospitals and where other railway companies have yet to install that safety equipment) at the time of the accident on the premise of relevant persons and circumstances, it is impossible to raise the issue of tort liability. Needless to say, the technical level, etc. required is increased and the safety margin is increased according to the size of risk. However, it is impossible to make light of the basic idea as mentioned above from the perspective of the principle of liability for negligence that is adopted in the national compensation system under current law.

4. Incidentally, in light of the time course from publication of the Long-Term Assessment in 2002 to the occurrence of the Earthquake in 2011, it is hard not to feel that both TEPCO and the appellant were excessively slow at verification of accuracy, importance, etc. of the Long-Term Assessment and consideration of protective measures against tsunamis based thereon. Some may consider that it is unreasonable that it is impossible to raise the issue of state responsibility for compensation in relation to the appellant.

However, to be brief, the reason that state responsibility for compensation cannot be found in this case is that as the Earthquake was too large and the Tsunami was too large, even if actions had been taken on the premise of the Long-Term Assessment, it is too unreasonable to determine that the Accident could have been avoided.

Regarding the water level of a design tsunami that was assumed at the time of the construction of the Power Station, its maximum wave height was less than half the height of the ground level of the site of the main buildings. The Long-Term Assessment that became a big issue in this action stated that a magnitude 8-class earthquake similar to the Meiji Sanriku Earthquake that occurred in 1896 might occur and that in this case, the tsunami magnitude of a large interplate earthquake would be around 8.2 and its seismic source would be 200 km long and 50 km wide along the Japan Trench. The Long-Term Assessment indicated the possibility of occurrence of a tsunami whose wave is far higher than the aforementioned water level of a design tsunami. However, the magnitude and tsunami magnitude of the Earthquake that actually occurred were 9.0 and 9.1 (the energy of an earthquake increases about thirty-fold if its magnitude increases by one, and the energy of the Earthquake is thus equivalent to over 20 times greater than the earthquake that was assumed in the Long-Term Assessment). The Earthquake was the largest earthquake ever recorded in Japan and was also the fourth largest ever recorded in the world. In addition, the Earthquake occurred as a result of interlocking of multiple seismic sources, and its area extended about 450 km long and about 200 km wide extending from the offing of Iwate Prefecture to the offing of Ibaraki Prefecture. The fault slippage related to the size of a tsunami reached over 50 m and is considered to have reached around five times as much as that of the Meiji Sanriku Earthquake, which was used as an assumption in the Long-Term Assessment. It is considered that not only the wave of the Tsunami at the front of the Site was higher than that of the tsunami assumed based on the Long-Term Assessment but also the Tsunami surged over a more extensive area and the duration of flooding was longer than the assumed tsunami as the size of the Earthquake significantly differed from the assumed earthquake. As it can be said that the 2002 Tsunami Assessment Method had been a technical level for the method of assessing the water level of a design tsunami for nuclear power plants before the Accident, a seawall, etc. installed as a measure against tsunamis on the premise of the Long-Term Assessment was to be designed based on a tsunami calculated in accordance with the assessment method indicated in the 2002 Tsunami Assessment Method based on the Long-Term Assessment, that is, the Estimated Tsunami. Even though a seawall, etc. is designed with a certain margin, as the Estimation was made with a margin in consideration of safety as well as in anticipation of the worst case, installation of a seawall, etc. is to be examined in relation to the scope for which measures against the Estimated Tsunami are required. However, the Tsunami that actually hit the Power Station was far larger in size and more extensive than the Estimated Tsunami as mentioned above, and it must be said that their differences in size, etc. could not at all be covered by a margin that should be taken into consideration in terms of design. As held in the majority opinion, it must be said that it was highly likely to be impossible to avoid a large amount of seawater entering the Site in association with the attack of the Tsunami even if a seawall, etc. had been installed.

As the Earthquake was too large as mentioned above, it is difficult to find a probability that the Accident due to the Tsunami could have been avoided. Therefore, it is impossible to raise the issue of state responsibility for compensation.

Incidentally, even so in terms of logic, there may be a view that it is unjust that the appellant did not exercise the regulatory authority at all with knowledge of the Long-Term Assessment and that this fact should not be overlooked. However, even trying to adopt such view, what can be considered to have been foreseeable for the appellant are within the limits of the tsunami assumed based on the Long-Term Assessment. Therefore, I must say that it is still unreasonable to raise the issue of state responsibility for compensation in relation to the consequence of the Tsunami that was far larger in size than the assumed tsunami and differed from the assumed tsunami in the direction of attack.

5. As mentioned above, it is clear that the prompt and appropriate recovery of damage due to the Accident is necessary and important, but I think that it is not the issue of state responsibility for compensation.

The concurring opinion stated by Justice KUSANO Koichi is as follows.

I agree with the majority opinion but I would like to state my concurring opinion with regard to the purport based on which I reached that conclusion.

1. The points that I consider especially important in the reasons stated in the majority opinion are summarized as follows: even if the Minister of Economy, Trade and Industry had exercised the regulatory authority under Article 40 of the Electricity Business Act (hereinafter referred to as the "Regulatory Authority") on the premise of the Long-Term Assessment and obliged TEPCO to take appropriate measures to prevent the occurrence of an accident at the Power Station due to a tsunami and TEPCO had performed that obligation, there was a considerable possibility that an accident similar to the Accident would have occurred; therefore, it is impossible to find a "relationship in which if the Minister of Economy, Trade and Industry had exercised the Regulatory Authority, the Accident or an accident similar thereto would not have occurred" (incidentally, how to position the aforementioned relation as a requirement for state responsibility for compensation due to a failure to exercise the regulatory authority is not made clear in detail in the majority opinion but I think this is an issue of a causal relationship). This logic is based on a traditional principle relating to a causal relationship between an inaction and its consequence, and this principle still cannot be ignored even in consideration of the seriousness of the disaster caused by the Accident. However, the issue of whether there is a causal relationship finally leads to a normative issue of how to interpret a "word indicating a reason" in the text of the relevant provisions (in this case, Article 1, paragraph (1) of the State Redress Act). Therefore, there is no need to consider that the responsibility to compensate loss or damage of a person who assumes the obligation to take an action cannot be found under any circumstances unless a causal relationship can be affirmed based on the aforementioned principle. As far as this case is concerned, the tsunami that was assumed in the Long-Term Assessment and the Tsunami certainly significantly differ in size, but they are the same in nature in being a tsunami derived from a large interplate earthquake in the area close to the Japan Trench. Therefore, the idea that the appellant's responsibility to compensate loss or damage is affirmed to the extent of damage suffered by the appellees if there is a high probability that an accident similar to the Accident would have occurred even on the assumption that the Earthquake was of the size assumed in the Long-Term Assessment (hereinafter referred to as the "Assumption") and that the appellees would have suffered damage (as long as the failure to exercise the Regulatory Authority can be found to be the appellant's violation of the obligation to take an action) (this idea can be considered as an idea that finds a "constructive causal relationship" between a failure to exercise the Regulatory Authority and relevant damage) is at least worthy of close consideration in light of the philosophy of equity. Thus, a causal relationship that can be found between a failure to exercise the Regulatory Authority and the aforementioned damage in line with the aforementioned idea is to be referred to as the "Constructive Causal Relationship," and in the next section, I will consider whether there is the Constructive Causal Relationship.

2. As argued in the majority opinion, the major reason for the occurrence of the Accident is that both electricity supplied from external substations to the Power Station (hereinafter this power supply source is referred to as "external power source") and electricity planned to be supplied to the Nuclear Reactor Facilities (this term is hereinafter used to mean nuclear reactor facilities including those of Units 5 and 6) by the Emergency Power Systems in emergency situations (hereinafter this power supply source is referred to as "emergency power source") (except for the emergency power source for Unit 6) became unavailable due to the Earthquake and the Tsunami. Consequently, Units 1 to 3 could not continue cooling the cores and the cores were damaged. Therefore, in determining whether the Constructive Causal Relationship exists, the urgent issue is whether both the external power source and emergency power source had been lost at the Nuclear Reactor Facilities under the Assumption.

Incidentally, for the following reason, it is possible to recognize through presumption that under the Assumption, external power source facilities would not be damaged by earthquake motion and the external power source would be available at least until the arrival of a tsunami, unlike the case of the Accident: the earthquake assumed in the Long-Term Assessment is just an earthquake with the same size as the Meiji Sanriku Earthquake, and the intensity of the Meiji Sanriku Earthquake in various parts of eastern Japan is regarded as 4 at a maximum; therefore, it is difficult to think that damage that can pose obstacles to the aforementioned power transmission will occur in external power source facilities due to an earthquake with a seismic intensity of 4 (at the time of the Earthquake, a quake with a seismic intensity of 6 upper was observed in Okuma-machi and Futaba-machi in Futaba-gun, Fukushima Prefecture, where the Power Station is located, and this earthquake motion caused serious damage to external power source facilities, which is considered to have become the major cause of the loss of external power source). Then, it is reasonable to consider that the tsunami assumed to arrive at the Power Station under the Assumption is the same as the Estimated Tsunami. When examining the impact of this tsunami (hereinafter referred to as the "Assumed Tsunami") on the Nuclear Reactor Facilities based on the status of flow of the Assumed Tsunami to the site, the status of layout of the Nuclear Reactor Facilities, and the status of operation thereof, etc., it is considered that it was possible to continue to use external power source at the Nuclear Reactor Facilities even after the arrival of the Assumed Tsunami or otherwise, there is a considerable possibility that an accident similar to the Accident would not have occurred. This point is explained in detail below (incidentally, regarding the emergency power source, emergency water-cooled diesel generators might lose their functions in association with the arrival of the Assumed Tsunami due to flooding of the coolant pumps that are installed in the seaward area 4 m above sea level, and emergency air-cooled diesel generators (except for that of Unit 6) are highly likely to lose their functions due to flooding of the auxiliary high-voltage power panels that are installed in the basement of a shared facility for assisting operation (shared pool) near the place from which the Assumed Tsunami flows in the Site; therefore, all the Nuclear Reactor Facilities, except for those of Unit 6, are highly likely to lose the emergency power source).

(1) Layout of the Nuclear Reactor Facilities and the status of flow of the Assumed Tsunami in the site

The main buildings of six nuclear reactors of the Power Station are installed in two sites, north and south sites, spanning a section 30 m above sea level where the main administrative building, etc. is located, etc. Of those sites, in the north site 13 m above sea level (hereinafter referred to as the "north site"), the major buildings of the two nuclear reactors, Units 6 and 5, are installed from north to south in this order. In the south site 10 m above sea level (the Site), the main buildings of four nuclear reactors, Unit 1 to 4, are installed from north to south in this order.

The Assumed Tsunami is assumed to arrive at the Power Station from the southeast, and it is assumed to flow into the Site located on the south side from near the turbine building of Unit 4 that is located most southerly out of the nuclear reactors and various facilities located far south (the southeast part of the Site). However, the Assumed Tsunami is not assumed to flow into the Site from the east side of the Site that is the front of the main buildings of Units 1 to 3 on the seaside. Seawater that flows in the Site is expected to head toward the northwest direction immediately after the inflow, then hit the turbine building of Unit 4 and the external walls, etc. of various facilities located on the south side thereof, and spread from south to north as a whole while running around these structures.

Regarding the north site, seawater is assumed to flow into the site from the northeast part of the site. However, the volume of the flow is extremely limited, and the area of flooding is assumed to be limited to a small area from the north end of the site to the area near the north external wall of the turbine building of Unit 6.

(2) Units 5 and 6

As stated above, as the flooding of the north site due to the Assumed Tsunami remains on a small scale, various electric facilities of Units 5 and 6 are unlikely to be damaged due to flooding and the external power source is highly likely to be continuously available at Units 5 and 6.

(3) Unit 1

The external power source of Unit 1 was received at the extra high voltage switching station for Units 1 and 2, was then stepped down by a start-up transformer for Unit 1, and after that, was connected to electric facilities, such as high-voltage power panels and low-voltage power panels, etc. for Unit 1. Out of these facilities, the extra high voltage switching station for Units 1 and 2 was installed on a hill located behind the Site when seen from the sea. Therefore, it is difficult to consider that its function would be damaged by the Assumed Tsunami. Next, as the start-up transformer was installed outside in the rear of the turbine building of Unit 1 (transformer yard), the possibility that the transformer will be flooded if the Assumed Tsunami flows into the Site cannot be immediately denied. However, the area near the transformer yead of Unit 1 is located far away from the southeast part of the Site from which the Assumed Tsunami flows into the Site, and in the Estimation, the maximum depth of flooding near the aforementioned transformer was estimated to be basically less than 1 m on the premise that no building exists in the Site (hereinafter, the values of the maximum depth of flooding in the Site in the Estimation are those read from a distribution map of the maximum depth of flooding attached to a report pertaining to the Estimation). Incidentally, the start-up transformer is a facility that is originally installed outside on the premise that it is exposed to rain and wind. At both Units 5 and 6, where the maximum depth of flooding around the buildings was around 0.5 to 1.5 m at the time of the Tsunami, the start-up transformers installed in the transformer yards did not lose their functions. Therefore, even if the Assumed Tsunami arrives at the site, the start-up transformer of Unit 1 is unlikely to lose its function. At last, when considering electric facilities, such as high-voltage power panels and low-voltage power panels, which were installed in the turbine building of Unit 1 (hereinafter collectively referred to as the "electric facilities"), if seawater reached the opening sections of the turbine building, the possibility that part of the seawater will enter the turbine building cannot be denied. However, in the Estimation, the maximum depth of flooding near the opening sections of the turbine building is basically less than 1 m on the premise of not taking account of existence of buildings, etc. Incidentally, all the aforementioned opening sections are located at places that are hidden behind the main buildings of Units 2 to 4 when seen from the place from which the Assumed Tsunami flows in the Site, and in addition, there are reversing valve pits about 6 m in depth in front of the opening sections. In consideration of these various facts, seawater that flows in the Site in association with the arrival of the Assumed Tsunami is unlikely to arrive at the opening sections of the turbine building of Unit 1. Even if it arrives at the sections, the volume of flooding in the turbine building is highly likely to be very limited. Therefore, at Unit 1, all or most electric facilities are likely to be spared from loss of function, and the external power source is likely to be continuously available.

(4) Unit 2

Unit 2 is adjacent to Unit 1, and the structures and layout of its various facilities (excluding the inside of the buildings) are also similar to those of Unit 1. Therefore, what I explained about Unit 1 also basically applies to Unit 2. However, the facilities of Unit 2 are supposed to be more affected by the Assumed Tsunami as they are closer to the place from which the Assumed Tsunami flows in the Site than those of Unit 1. In the Estimation, the maximum depth of flooding near the turbine building of Unit 2 is also estimated to be basically around 1 m on the premise of not taking account the existence of buildings, etc., but it is also recognized as exceeding 1.5 m in some places. Therefore, it can be said that the possibility that some of the electric facilities installed in the turbine building of Unit 2 will be damaged is slightly higher than the case of Unit 1. Even so, the possibility that all or a major part of these electric facilities will be spared from loss of function is not small at all, and furthermore, Unit 2 had a structure that enables the mutual accommodation of electric power with Unit 1. Therefore, even if Unit 2 loses the external power source, it is much likely to be able to recover a power source early by accommodation of electric power from Unit 1 (incidentally, four low-voltage power panels of Unit 2 that are installed in the area different from the area where other electric facilities are installed maintained their functions even at the time of the Accident; therefore, even if the turbine building is flooded due to the Assumed Tsunami, these four low-voltage power panels are highly likely to maintain their functions, and accommodation of electric power from the low-voltage power panels of Unit 1 to those of Unit 2 is highly likely to be realized early). Then, external power source is continuously available at Unit 2 or otherwise, Unit 2 is highly likely to reach recovery of the power source owing to accommodation of electric power from Unit 1.

(5) Unit 3

Unit 3 usually received power supply from external power source via the extra high voltage switching station for Units 3 and 4. The extra high voltage switching station for Units 3 and 4 was located in the Site 10 m above sea level, and in the Estimation, the maximum depth of flooding near the same station was estimated to be over 3.5 m. Therefore, the brakers, disconnectors, etc. located in the station are highly likely to go under water and lose their functions due to entry of a large amount of seawater in the extra high voltage switching station for Units 3 and 4 in association with the arrival of the Assumed Tsunami. However, at Unit 3, the power receiving facilities pertaining to the external power source were under construction on the day of the Earthquake. Therefore, the high-voltage power panels of Unit 2 and those of Unit 3 were connected to each other, and Unit 3 was receiving power supply from the external power source via the high-voltage power panels of Unit 2. Then, the high-voltage power panels of Unit 2 are unlikely to lose their functions due to the Assumed Tsunami, as mentioned above. Thus, in the end, Unit 3 is unlikely to lose the external power source (in the Estimation, the maximum depth of flooding near the opening sections of the turbine building of Unit 3 is estimated to be around 1.5 m on the premise of absence of buildings, etc., and it is far shallower than the actual maximum depth of flooding due to the Tsunami (4 to 5 m). In addition, the opening sections of the turbine building of Unit 3 are located behind the turbine building of Unit 4 and the service buildings, etc. of Units 3 and 4 when seen from the place from which the Assumed Tsunami flows into the site, and there are also reversing valve pits about 6 m in depth in front of the opening sections; therefore, under the Assumption, the maximum depth of flooding around the opening sections of the turbine building is highly likely to be far shallower than 1.5 m; thus, the high-voltage power panels of Unit 3 are much likely to be able to maintain their functions). Furthermore, regarding Unit 3, the DC power panel with a battery was spared from flooding at the time of the Tsunami. Therefore, the core cooling system is considered to have worked with DC power supplied from this battery for around 35 hours up to the early hours of March 13, 2011, even after loss of all AC power sources. It is considered that the DC power panel was spared from flooding as it is installed in the middle basement of the turbine building and seawater that enters a building has the nature of falling directly toward the underground direction. In light of this, even under the Assumption, the DC power panel of Unit 3 is highly likely to be spared from flooding (the DC power panels of Units 5 and 6 that are installed in the middle basement in the same manner as above were also spared from flooding at the time of the Tsunami). Then, it is considered that it is sufficiently possible to lay a temporary cable connecting to Units 1 and 2 and receive accommodation of electric power or to recover AC power by connecting Unit 3 to a power source car if around 35 hours are left before loss of function (at the time of the Accident, workers and materials, etc. were devoted to recovery of power source, alternative pouring of water, and other works for Units 1 and 2, and commencement of work to recover AC power for Unit 3 by means of a power source car was significantly delayed). In light of the aforementioned various facts, even if the Assumed Tsunami arrives at the site, Unit 3 will not lose external power source, or if it temporarily loses the external power source, recovery of the power source is much likely to be completed while the DC power panel is functioning.

(6) Unit 4

As mentioned above, the extra high voltage switching station for Units 3 and 4, which is a power receiving facility pertaining to the external power source of Unit 4, is highly likely to lose its function due to the Assumed Tsunami. In addition, as Unit 4 was a nuclear reactor facility located closest to the place from which the Assumed Tsunami flows into the Site, a large amount of seawater is assumed to enter the main buildings of Unit 4 in association with the arrival of the Assumed Tsunami. Moreover, there was no special circumstance where the DC power panel with a battery was located in the middle basement of a building. Therefore, Unit 4 is likely to lose all power sources due to the Assumed Tsunami. However, on the day of the Earthquake, the nuclear reactor of Unit 4 was not in operation, and all fuel for it was stored in the spent fuel pool. Incidentally, at the time of the Accident, pouring of water into the spent fuel pool was suspended due to loss of all power sources of Unit 4, and no water was poured at all for over eight days until the Self-Defense Forces subsequently started releasing water toward the same pool from outside the building. Nevertheless, it is considered that fuel was not exposed from the water surface. As mentioned above, under the Assumption, the external power sources of Units 1 to 3 are not lost, or even if they are temporarily lost, they are much likely to be recovered early. In consideration of this point, under the Assumption, pouring of water in the spent fuel pool of Unit 4 is considered to be highly likely to be realized at a point far earlier than the passage of over 8 days mentioned above. Therefore, in the end, a serious situation, including damage to fuel, is also unlikely to occur at Unit 4.

For the reasons described above, under the Assumption, no fact that is sufficient to find the Constructive Causal Relationship can be found in relation to any of the Nuclear Reactor Facilities. Although I am filled with horror at the fact that the aforementioned facts include chance occurrences, such as that fuel of Unit 4 was transferred to the spent fuel pool on the very day of occurrence of the Earthquake and that on the same day, Unit 3 was receiving accommodation of electric power from Unit 2 (the fact that the DC power panel with a battery of Unit 3 was installed in the middle basement can also be considered as a chance occurrence in a sense), these facts are historical facts that are not affected by the Assumption. Therefore, these facts cannot be denied in determining whether the Constructive Causal Relationship exists (however, the fact that a ground for denying the existence of the Constructive Causal Relationship relies on such chance occurrences can be a potent ground for finding that the failure to exercise the Regulatory Authority constitutes the State's violation of the obligation to take an action). However, the possibility that a new fact may be generated as a result of the Assumption and that this may affect a determination concerning the existence of the Constructive Causal Relationship cannot be denied (to cite a case, under the Assumption, there is the possibility that electric power is continuously supplied from external power source to the Nuclear Reactor Facilities with some electric facilities flooded; it cannot be said that there is no possibility that a fire occurs due to a short of an internal wiring, etc. in a flooded electric facility in the aforementioned process). However, in order to infer the possibility of occurrence of such new fact, it is indispensable to indicate a specific fact that gives a basis for the inference, but no such specific fact can be found among the facts found by the court of prior instance.

3. In such manner, it was made clear that the Constructive Causal Relationship cannot be found. Putting this conclusion and the conclusion based on the traditional principle mentioned in 1. together, the following proposition can be derived. That is, as long as the Earthquake is of its actual size, there is a highly considerable possibility that occurrence of an accident similar to the Accident could not have been avoided even if the Regulatory Authority had been exercised. In addition, as long as the Earthquake is of the size assumed in the Long-Term Assessment, there is the highly considerable possibility that an accident similar to the Accident could have been avoided even if the Regulatory Authority had not been exercised. This proposition is sufficient to conclude that no causal relationship can be found between the failure to exercise the Regulatory Authority and the Accident no matter how widely a "causal relationship," which is a concept whose denotation is somewhat unclear, is understood. Therefore, I agree with the majority opinion.

The dissenting opinion stated by Justice MIURA Mamoru is as follows.

With regard to No. 3 in the holding, unlike the majority opinion, I think that the appellant assumes the responsibility to compensate loss or damage under Article 1, paragraph (1) of the State Redress Act in relation to the appellees stated in Lists of Appellees 2 to 6 attached to this judgment and that the final appeal should be dismissed with prejudice on the merits regarding the claims of the same appellees. The reasons are as follows.

1. As stated in the majority opinion, it is reasonable to consider that a failure to exercise the regulatory authority by the public employee of the State or a public entity is illegal in terms of the application of Article 1, paragraph (1) of the State Redress Act in relation to persons who suffered damage from the failure to exercise if it is found to go beyond the limits to which the failure to exercise is permitted and be extremely unreasonable under specific circumstances in light of the purport and purpose of laws and regulations that provide for the authority and the nature, etc. of the authority.

2. Purport, purpose, etc. of laws and regulations

(1) The Atomic Energy Basic Act (prior to amendment by Act No. 47 of 2012) provides that the research, development and utilization of nuclear energy is limited to peaceful purposes and is to aim at ensuring safety (Article 2). The Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors (prior to amendment by Act No. 47 of 2012; hereinafter this Act is merely referred to as the "Reactors Regulation Act" and the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors amended by Act No. 47 of 2012 is referred to as the "Reactors Regulation Act after the 2012 Amendment") was, in accordance with the spirit of the Atomic Energy Basic Act, enacted for the purpose of providing necessary regulations on installation and operation, etc. of reactors in order to ensure public safety by preventing hazards due to the use of nuclear source materials, nuclear fuel materials, and reactors and by protecting nuclear fuel materials (Article 1), and provides that any person who intends to install a commercial power reactor shall obtain the permission of the Minister of Economy, Trade and Industry and that in the case that an application for the permission is made, the Minister of Economy, Trade and Industry shall not grant the permission unless the minister finds that the application conforms with criteria, such as that the location, structure and equipment of the reactor facilities are such that they will not hinder the prevention of disasters resulting from nuclear fuel materials, materials contaminated by nuclear fuel materials or the reactors (Article 23, paragraph (1), item (i) and Article 24, paragraph (1)).

Then, it is provided that the design, construction method, and inspection, etc. of commercial power reactors are to be also regulated by the Electricity Business Act (Article 73 of the Reactors Regulation Act). The purpose of the Electricity Business Act includes assuring public safety and promoting environmental preservation by regulating the construction, maintenance, and operation of electric facilities (Article 1). The same Act provides that a person that installs electric facilities for business use must maintain the electric facilities for business use to ensure that they conform to the technical standards established by Order of the Ministry of Economy, Trade and Industry (Article 39, paragraph (1)) and that Order of the Ministry of Economy, Trade and Industry must be formulated in accordance with requirements, including that electric facilities for business use are not to pose a risk of inflicting bodily damage or damage to objects (paragraph (2), item (i) of the same Article). In addition, the same Act provides that if the Minister of Economy, Trade and Industry finds that electric facilities for business use do not conform to the technical standards established by this Order of the Ministry of Economy, Trade and Industry, the Minister may order the person who installs the electric facilities for business use to repair or alter the electric facilities for business use to ensure conformity to the technical standards, or order the person to relocate the facilities or suspend their use, or temporarily restrict the person from using the facilities (Article 40). The same Act has penal provisions, such as those stipulating that a person who violates such an order to conform to the technical standards is subject to imprisonment for not more than three years or a fine of not more than 3,000,000 yen, or both (Article 116, item (ii), etc. of the same Act).

In response to these provisions, as the aforementioned technical standards, Article 4, paragraph (1) of the Ministerial Order to Provide Technical Standards for Nuclear Facilities for Power Generation (prior to amendment by Order of the Ministry of Economy, Trade and Industry No. 68 of 2005; hereinafter this order is referred to as the "Ministerial Order prior to the 2005 Amendment" and the same Ministerial Order after the same amendment is referred to as the "Ministerial Order after the 2005 Amendment") provides that if a nuclear reactor facility, etc. is likely to be damaged by a landslide, fault, avalanche, flood, tsunami or storm surge, or uneven settling of the foundation ground, etc., it is necessary to install protection facilities, improve the foundation ground, and take other appropriate measures. The same paragraph of the Ministerial Order after the 2005 Amendment provides that if the safety of a nuclear reactor at a nuclear reactor facility, etc. is likely to be impaired due to an assumed natural disaster (meaning a landslide, fault, avalanche, flood, tsunami, storm surge, uneven settling of the foundation ground, etc.; however, excluding an earthquake), it is necessary to take protective measures, improve the foundation ground, and take other appropriate measures.

It is considered that the aforementioned provisions of laws and regulations were established in relation to technical standards for commercial power reactors to the following effect: nuclear reactors are devices that use nuclear fuel materials, which release high energy in the process of atomic fission, as fuel, and their operation generates a large amount of radioactive materials inside the nuclear reactors that are hazardous to the human body; if the safety of a nuclear reactor facility is not ensured, it is likely to cause serious disasters, such as significant harm to the lives and bodies of the employees of the nuclear reactor facility and residents, etc. living around the facility, as well as radioactive contamination of surrounding environment; in consideration of these facts, in order to ensure that such disasters would never occur, the provisions do not leave ensuring of safety after installation of nuclear reactors only to persons who install the nuclear reactors, but stipulate that the competent minister, the Minister of Economy, Trade and Industry, is to establish technical standards on a timely basis from scientific and expert technical perspectives so that nuclear reactor facilities are appropriately maintained and that if any nuclear reactor facilities do not conform to the technical standards, the Minister may order the person who installs the relevant nuclear reactor facilities to ensure that the nuclear reactor facilities conform to the technical standards as promptly as possible. In particular, ensuring of the safety of nuclear reactor facilities in such manner would be required to be conducted based on a wide-range of the latest scientific and expert technical knowledge. In addition, it was considered to be appropriate to leave the aforementioned exercise of the authority to the competent minister from the perspective of the need to respond to the latest science and technology standards instantly in light of the constant advancement and progress of science and technology, (see 1985 (Gyo-Tsu) 133, the judgement of the First Petty Bench of the Supreme Court of October 29, 1992, Minshu Vol. 46, No. 7, at 1174 (hereinafter referred to as the "1992 Judgment")).

Given the purposes of the aforementioned laws and regulations and the purport of the aforementioned provisions, it can be said that the Minister of Economy, Trade and Industry's regulatory authority under Article 40 of the Electricity Business Act should have been exercised on a timely basis and in an appropriate manner so that measures necessary to prevent even extremely rare disasters would be taken as promptly as possible based on the latest scientific and expert technical knowledge mainly for the purpose of preventing harm to the lives and bodies of the employees of nuclear reactor facilities and residents living around the facilities, etc.

(2) In this regard, the appellant argues that the Minister of Economy, Trade and Industry did not have the regulatory authority to rectify matters concerning the safety of the basic design or basic design policies of commercial power reactor facilities by means of issuing orders to conform to the technical standards under Article 40 of the Electricity Business Act.

Originally, it is one of the criteria for permitting installation of a nuclear reactor that the location, structure and equipment of a nuclear reactor facility are such that they will not hinder the prevention of disasters resulting from a nuclear reactor, etc. (Article 24, paragraph (1), item (iv) of the Reactors Regulation Act), and examination of conformity to the criteria requires comprehensive determination based on a wide-range of the latest scientific and expert technical knowledge. The purpose of providing that the Minister of Economy, Trade and Industry shall hear, in advance, the opinion of the Atomic Energy Commission with respect to the application of certain criteria in the case of granting permission for installation of a nuclear reactor (paragraph (2) of the same Article) is considered to leave determinations concerning conformity to the aforementioned criteria to the Minister of Economy, Trade and Industry's reasonable determinations that are to be made with respect for opinions based on scientific and expert technical knowledge of the Atomic Energy Commission that consists of persons with expertise, etc. in relevant areas. With regard to regulations concerning the installation, operation, etc. of nuclear reactors under the Reactors Regulation Act, etc., regulations, such as permission for installation, permission for change, approval of design and construction method, pre-operational inspection, approval of operational safety programs, and periodic inspection, are supposed to be enforced by stages, and it is considered that in the stage of granting permission for the installation of a nuclear reactor, only the safety of the basic design or basic design policy of the nuclear reactor is made subject to the regulation (see the 1992 judgement).

However, it is natural that in relation to a nuclear reactor facility for which installation of a nuclear reactor was permitted, the safety of the basic design or basic design policy of the nuclear reactor facility may be affected by natural phenomena, such as tsunamis, and the development of scientific and expert technical knowledge in various fields, etc. after the permission. Even in such case, it is, needless to say, necessary to ensure the safety of the nuclear reactor facility based on the latest knowledge. For that purpose, it is predetermined by the law that the Minister of Economy, Trade and Industry establishes appropriate technical standards on a timely basis, persons who install nuclear reactors assume the obligation to maintain nuclear reactor facilities to ensure that they conform to the technical standards, and the Minister of Economy, Trade and Industry has the regulatory authority to make rectification by issuing an order to conform to the technical standards. If in such case, it is considered that there is no other choice but to use administrative guidance unless the Minister of Economy, Trade and Industry rescinds or revokes permission for installation, such interpretation also goes against the idea shared in the entire legal system that nuclear power should be used while ensuring safety of nuclear reactors through regulations by stages. The text of the provisions that list tsunamis and other natural phenomena and then stipulate as the content of the technical standards that it is necessary to take appropriate measures, such as improvement of the foundation ground, is also considered to be premised on that idea. In issuing an order to conform to the technical standards, the Minister of Economy, Trade and Industry sometimes hears the opinion of the Atomic Energy Commission as needed, but it does not affect the aforementioned interpretation. Article 43-3-23 of the Reactors Regulation Act after the 2012 Amendment provides that the Nuclear Regulation Authority may order necessary operational safety measures to be taken not only when it finds that nuclear power reactor facilities do not conform to the technical criteria but also when it finds that they do not conform to the criteria for permission for installation, and this is considered to be based on the same purport as the interpretation of Article 40 of the Electricity Business Act.

Therefore, it is reasonable to consider that the Minister of Economy, Trade and Industry also had the regulatory authority to rectify matters concerning the safety of the basic design or basic design policies of commercial power reactor facilities by issuing orders to conform to the technical standards under Article 40 of the Electricity Business Act. I must say that the appellant had erred in the interpretation of laws and regulations in this regard since before the Accident.

3. Interpretation of the Technical Standards, etc.

(1) The requirement for the Minister of Economy, Trade and Industry to issue an order to conform to the technical standards under Article 40 of the Electricity Business Act is the Minister's finding that electric facilities for business use do not conform to the technical standards established by Order of the Ministry of Economy, Trade and Industry. The technical standards established by Article 4, paragraph (1) of the Ministerial Order prior to the 2005 Amendment (hereinafter referred to as the "Technical Standards") are to the effect that if a nuclear reactor facility, etc. is likely to be damaged by a tsunami, etc., it is necessary to install protection facilities, improve the foundation ground, and take other appropriate measures. Although the technical standards pertaining to Article 4, paragraph (1) of the Ministerial Order after the 2005 Amendment are also considered to have the same meaning as the Technical Standards, these technical standards overlap the following criteria for permitting installation or change of a nuclear reactor (Article 24, paragraph (1), item (iv) and Article 26, paragraph (4) of the Reactors Regulation Act): the location, structure and equipment of a nuclear reactor facility are such that they will not hinder the prevention of disasters resulting from a nuclear reactor, etc. Therefore, these standards and criteria must be interpreted in a consistent way.

(2) A. Since 1970, the predecessor of the Nuclear Safety Commission, the Atomic Energy Commission, had established a regulatory guide for evaluating the adequacy of the design policies of nuclear reactors in safety review pertaining to applications for permission for installation of nuclear reactors, etc. (hereinafter referred to as the "Former Safety Design Review Guide"). However, in August 1990, the Nuclear Safety Commission reviewed the aforementioned guide and formulated the "Regulatory Guide for Reviewing Safety Design of Light Water Nuclear Power Reactor Facilities" and partially revised it in March 2001 (hereinafter referred to as the "1990 Safety Design Review Guide"). Guide 2, paragraph (2) of the 1990 Safety Design Review Guide stated as follows: "structures, systems, and devices with safety functions are to be designed to ensure that the safety of nuclear reactor facilities is not damaged by assumable natural phenomena other than earthquakes"; "structures, systems, and devices with safety functions that are especially important are to be designed in consideration of a condition that is considered to be the most demanding among predictable natural phenomena or a case where accident load is appropriately combined with natural force." Then, in a commentary in the guide, it was stated that a "condition that is considered to be the most demanding among predictable natural phenomena" "means a demanding condition that at least does not fall below natural phenomena recorded in the past in consideration of the reliability of past records in response to subject natural phenomena and that is deemed to be statistically appropriate." Although natural phenomena assumed in this guide are not limited to those that are the largest ever, the guide did not specifically indicate how to assume and protect against such natural phenomena.

B. On the other hand, disaster control measures in Japan: including measures against tsunamis, are based on the Basic Act on Disaster Management established in 1961. In the wake of damage to the Okushiri Island due to a tsunami in the southwest-off Hokkaido earthquake in 1993, etc., the necessity of strengthening measures against tsunamis in local disaster management plans under the same Act was recognized, and in March 1997, seven ministries and agencies including the National Land Agency formulated the "Guide for Strengthening Measures against Tsunamis in Local Disaster Management Plans" (Guide of Seven Ministries and Agencies) based on knowledge of persons with relevant expertise, etc. The same guide stated as follows: the largest ever tsunami is basically used as the subject tsunami that serves as a precondition for the formulation of a tsunami disaster management plan; with regard to the coastal area for which the possibility of occurrence of an earthquake accompanied by a tsunami has been pointed out by the results of recent earthquake observation and research, etc., the largest assumable earthquake tsunami is examined separately in comparison with the largest ever tsunami, and then, the subject tsunami is to be set from the perspective of safety.

In addition, the Great Hanshin-Awaji Earthquake in 1995 led to the establishment of the Act on Special Measures concerning Earthquake Disaster Management in 1995 for the purpose of promoting strengthening of earthquake disaster management measures, etc. In the Act, the Headquarters for Earthquake Research Promotion (hereinafter referred to as the "Earthquake Headquarters") was established in the Prime Minister's Office (subsequently, in the Ministry of Education, Culture, Sports, Science and Technology) as an organization that conducts the planning, etc. of comprehensive and basic measures for the promotion of earthquake observation, measurement, survey, and research in order to address the problem of the past system in which earthquake survey and research findings were not sufficiently communicated to and utilized by the people and organizations in charge of disaster management (Article 7, paragraph (1) of the same Act). Furthermore, under the Earthquake Headquarters, the Earthquake Research Committee consisting of members appointed by the Minister of Education, Culture, Sports, Science and Technology out of the employees of relevant administrative organs and persons with relevant expertise was established for the purpose of collecting, organizing, analyzing, and comprehensively evaluating earthquake survey results, etc. (Article 10 of the same Act).

After that, the Subcommittee for Long-term Evaluations was established under the Earthquake Research Committee with the aim of assessing the possibility of occurrence of earthquakes in the future, and also with the aim of clarifying the regional characteristics of seismic activities in order to create the Probabilistic Seismic Hazard Maps Covering the Whole Japan. The Trench Type Subcommittee was also established under the Subcommittee for Long-term Evaluations in order to examine long-term assessments of earthquakes that will occur in the sea area. The long-term assessments of seismic activities in various sea areas were published one after another based on surveys and deliberations in the Trench Type Subcommittee with the approval of the Subcommittee for Long-term Evaluations and the Earthquake Research Committee. In July 2002, the Long-Term Assessment was published as a long-term assessment of seismic activities in the area extending from the offing of Sanriku to the offing of Boso.

C. In this manner, while the State's measures and surveys and researches, etc. pertaining to tsunami disaster management measures were making progress after 1993 or 1995, the 1990 Safety Design Review Guide was not revised in that regard.

On the other hand, since 1978, the Atomic Energy Commission and the Nuclear Safety Commission had established the "Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities" as a regulatory guide for evaluating the adequacy of seismic design policies in safety review pertaining to applications for permission for installation of nuclear reactors, etc. However, in September 2006, the Nuclear Safety Commission reviewed this guide and formulated a new guide (hereinafter referred to as the "2006 Seismic Design Review Guide"). This guide reflected accumulation of new knowledge on seismology, etc. and progress of seismic design technology, etc. Regarding tsunamis, the guide also stated as follows as a consideration to phenomena associated with earthquakes: "safety functions of facilities are not likely to be significantly affected by a tsunami that is appropriately assumed to be likely to occur within the operational period of the facilities though its occurrence is supposed to be extremely rare." This statement is considered to indicate that a tsunami should be assumed based on the latest scientific and expert technical knowledge on the premise that the assumed tsunami is not limited to the largest ever tsunami. However, the guide did not indicate any more specific guide for the method of assuming and protecting against tsunamis, unlike the detailed guide for the standard earthquake motion, etc. in relation to seismic safety.

Then, in September 2006, with regard to the assessment and confirmation of the seismic safety of existing nuclear power reactor facilities, etc. in light of the 2006 Seismic Design Review Guide (hereinafter referred to as the "anti-seismic backcheck"), the Nuclear and Industrial Safety Agency (hereinafter referred to as the "Safety Agency") formulated an assessment method and confirmation standards (hereinafter referred to as the "anti-seismic backcheck rules"). The Safety Agency also instructed TEPCO and other electric power companies, etc. to implement the anti-seismic backcheck on their nuclear power reactor facilities that were in operation or under construction and report the results thereof. However, the anti-seismic backcheck rules cited safety against tsunamis as one of the assessment items and stated as follows as an assessment method: "in making assessment on tsunamis, a tsunami that is likely to occur in the operational period of facilities though its occurrence is supposed to be extremely rare is to be assumed in consideration of the status of occurrence of previous tsunamis, the status of distribution of active faults, the latest knowledge, etc., and assessment should basically be made by numerical simulation."

(3) Taking into account the aforementioned purport, etc. of Article 40 of the Electricity Business Act based on the developments, etc. as mentioned above, in the Technical Standards, the "case where a nuclear reactor facility, etc. is likely to be damaged by a tsunami" means the case where the safety functions of a nuclear reactor facility, etc. are likely to be damaged by a tsunami in consideration of a condition, etc. that is considered to be the most demanding among assumable tsunamis. In assuming a tsunami, it is considered to be necessary to appropriately assess a tsunami that is likely to occur within the operational period of the facilities though its occurrence is supposed to be extremely rare by means of numerical calculation, etc. based on the latest scientific and expert technical knowledge while conservatively (on the safe side) taking into account uncertainties of various factors.

Moreover, "(to install protection facilities, improve the foundation ground, and take other) appropriate measures" means necessary and appropriate measures to reliably prevent the safety functions of a nuclear reactor facility, etc. from being damaged by a tsunami under specific circumstances, and it is considered that the content of such measures should be reasonably determined in light of the purport and purpose of laws and regulations based on the latest scientific and expert technical knowledge while conservatively (on the safe side) taking into account uncertainties of various factors.

Regarding ensuring of safety against tsunamis as mentioned above, the 1990 Safety Design Review Guide and the 2006 Seismic Design Review Guide do not indicate any numerical guide, etc. However, in this regard, it is safe to pay attention to the fact that, as technical safety objectives, the Basic Safety Principles of the International Atomic Energy Agency (IAEA) state that the possibility of occurrence of severe core damage should be about one in ten thousand or less per reactor operating year in relation to existing nuclear reactors and one in one hundred thousand or less per reactor operating year in relation to future nuclear reactors (paragraph 27 of the Basic Safety Principles for Nuclear Power Plants 75-INSAG-3 Rev. 1 INSAG-12). The statement in the 1992 Judgment, "in order to ensure that such disasters would never occur," is probably to the same effect.

In addition, the Technical Standards have the aspect of constraining electricity supply and other business activities conducted by persons who install nuclear reactors, and such aspect also affects the interests of persons who receive electricity supply and can also be related to the maintenance and development of the people's lives and national economy. However, on the other hand, if safety of nuclear reactor facilities is not ensured, this would clearly lead to a serious situation, including severe damage to many people's lives and physical health and the basis of their livelihoods. The moral right that is based on survival is the most important value that is guaranteed under the Constitution. It is natural that persons who conduct business activities that can widely cause serious damage to the moral right assume the obligation to ensure an extremely high level of safety and that the State imposes necessary regulations to ensure the appropriate performance of that obligation. In the case where a nuclear reactor facility, etc. is likely to be damaged by a tsunami, a failure to take necessary measures is not justified on the grounds of circumstances, such as economic interests pertaining to electricity supply business and general interests, etc. of persons who receive electricity supply.

4. Predictability, etc.

(1) At the Nuclear Reactor Facilities, it is necessary to continue to cool the cores that continue to produce heat even after the nuclear reactors are automatically shut down at an abnormal time, such as the time of occurrence of an earthquake, and electricity is necessary to activate many water injection systems that were installed for that purpose. However, if electricity supplied from external substations becomes unavailable, electricity is to be supplied by the Emergency Power Systems. The Emergency Power Systems were installed on the first floor or the first basement level of the turbine buildings or shared facility for assisting operation (shared pool) of the Nuclear Reactors.

The outline of the Accident is as follows: in a situation where supply of electricity from external substations was stopped due to the Earthquake, the Tsunami arrived at the Power Station, the Site was flooded due to runup waves, and the Emergency Power Systems lost their functions; thereby, the nuclear reactors, Units 1 to 3, became unable to cool the cores after stoppage of their operations, and fuel that reached high temperatures was significantly damaged; as a result, a large amount of radioactive material was released from the Nuclear Reactor Facilities.

If loss of functions of the Emergency Power Systems, etc. occurs in a situation where the external power source is lost as mentioned above, it is highly likely to lead to a situation similar to the Accident. Therefore, when determining the illegality of the Minister of Economy, Trade and Industry's failure to exercise the regulatory authority in this case, it is necessary to take into account the issue of whether it can be said that it was foreseeable that a tsunami would arrive at the Power Station, that the Site would be flooded, and that the functions of the Emergency Power Systems would be lost. As this issue overlaps the requirement under the Technical Standards that a nuclear reactor facility, etc. is likely to be damaged by a tsunami, it should be examined on the premise of the interpretation mentioned in 3.

(2) A. The surface of the earth is covered by dozen small and large bedrocks that are called plates, and each of those plate moves differently in the horizontal direction at a speed of a few centimeters per year. Tensile force and compressive force caused by this movement of the plates cause accumulation of strain in the bedrocks. If such strain reaches a limit, the bedrocks will be rapidly destroyed along a certain surface (fault surface), which will cause occurrence of an earthquake. In the Japan Trench on the Pacific side of the Japanese archipelago, the plate on the sea side sinks below the plate on the land side, dragging the tip section of the plate on the land side. If strain at the place where these two plates have contact with each other reaches a limit, a fault motion in which the tip of the plate on the land side jumps will occur, which will cause occurrence of an interpolate earthquake.

The term "tsunami earthquake" generally refers to an earthquake in which a fault slips slower than usual and a tremor felt by people is small but a tsunami caused by the earthquake is larger in size. Such earthquake is characterized as an earthquake that does not repeatedly occur at the same place but is slow and low-frequency, unlike characteristic earthquakes that basically repeatedly occur with almost the same size at individual faults. It was known that earthquakes that have characteristics similar to tsunami earthquakes had frequently occurred near the trench. It was considered that such tsunami earthquakes would be likely to occur in the areas that appear to have the same structural features relating to seismic activities based on the status of occurrence of earthquakes in the past. However, the issue is how to separate such areas.

B. The positions and structures of the Earthquake Research Committee, etc. and the background to the publication of the Long-Term Assessment, etc. are as stated above. The Earthquake Research Committee was established in the government as a specialized organization that conducts comprehensive assessment, etc. of the results of surveys on earthquakes, etc. based on the provisions of laws that aim at promoting strengthening of earthquake disaster management measures. It can be said that the Long-Term Assessment was intended to be sufficiently communicated to and utilized by the people and organizations in charge of disaster management as earthquake survey and research findings in the same manner as the long-term assessments of seismic activities in other sea areas.

Then, the summary of the Long-Term Assessment is basically as stated in No. 1, 2. (3) in the holding. In the Long-Term Assessment, in assessing the location of occurrence of an earthquake and the form of its source area, an estimation was conducted in relation to the area extending from the north part of the offing of Sanriku to the offing of Boso in reference to the past source model, as well as survey and research findings concerning the estimation of the plate boundary surface based on microearthquakes, etc. and survey and research findings concerning the velocity structure of the area. In separating areas, the epicentral distribution of microearthquakes was referred to, and the distribution of the epicenters, wave source areas, and source models of past large earthquakes and research findings concerning back slip models were taken into consideration. Then, the following magnitude 8-class tsunami earthquakes occurred in the area close to the Japan Trench extending from the north part of the offing of Sanriku to the offing of Boso after the 17th century: the Keicho Sanriku Earthquake in 1611 and the Meiji Sanriku Earthquake in 1896 in the offing of Sanriku, and the Enpo Boso-oki Earthquake in 1677 in the offing of Boso. In addition, the plate on the sea side sinks below the plate on the land side at a similar incline and at a similar depth. Therefore, while handling this area as one area, it was assessed that a similar earthquake is highly likely to occur anywhere in that area though the source area cannot be identified.

In this manner, the Long-Term Assessment made an assessment on the occurrence of seismic activities in the area extending from the offing of Sanriku to the offing of Boso in the future as part of comprehensive assessment on earthquakes in order to promote strengthening of earthquake disaster management measures, etc. It can be said that the basic reliability of the Long-Term Assessment was secured in that the assessment was conducted by an appropriate method using scientific and expert technical knowledge obtained until that time.

C. On the other hand, although the Long-Term Assessment stated that the aforementioned three tsunami earthquakes occurred in the area close to the Japan Trench, a view that differs from the conclusion in the Long-Term Assessment had been indicated in relation to the Keicho Sanriku Earthquake and the Enpo Boso-oki Earthquake since the time when deliberation was being conducted on the Long-Term Assessment. Such view was also taken up by the Trench-Type Subcommittee, and the conclusion concerning the view was drawn after going through specific consideration and deliberation. The ground for the conclusion was also clearly indicated in the Long-Term Assessment.

Moreover, regarding the fact that the Long-Term Assessment handled the area close to the Japan Trench extending from the north part of the offing of Sanriku to the offing of Boso as one area, a view concerning specific areas or conditions (presence of an accretionary prism and a horst, etc.) that are preconditions for occurrence of a tsunami earthquake and a view concerning the difference between the north and south parts of the area along the Japan Trench had been indicated since the time when a deliberation was being conducted on the Long-Term Assessment and thereafter. However, tsunami earthquakes in trenches where no accretionary prism is formed, such as the Nicaragua Earthquake in 1992, had been known. In addition, even in terms of the difference between the north and south parts, the Enpo Boso-oki Earthquake that occurred in the south part where no accretionary prism was formed was also considered to be a tsunami earthquake. In this manner, it is difficult to say that the aforementioned views generally clarified relationships with the occurrence of a tsunami earthquake. In that regard, it is considered that the views do not necessarily deny the possibility of occurrence of a similar tsunami earthquake in the area of the south part along the Japan Trench. On the premise of existence of such views, the Long-Term Assessment states that tsunami earthquakes that occurred in the past cannot be considered as earthquakes that occur only a specific area: the offing of Sanriku, based on various survey and research findings, etc. and determined that such tsunami earthquake may also occur near the trench at the plate boundary that has the same structure. It is thus difficult to say that the aforementioned views impair the reasonableness of the Long-Term Assessment.

Although it is natural that various hypotheses and individuals' views are indicated in this kind of research, it can be said that the reliability of the Long-Term Assessment is increased by the fact that it was compiled by using the latest knowledge: including those hypotheses and views, with approval of many experts after going through specific consideration and deliberation.

Certainly, there are unexplained matters with regard to the occurrence of earthquakes and tsunamis, and there are also limits, such as the fact that materials on past earthquakes are limited to those after the 17th century. It is thus undeniable that the Long-Term Assessment also involves uncertainties. However, it is safe to say that it is rather natural that prediction of such natural phenomena is difficult and involves uncertainties. The Technical Standards that require "likelihood to be damaged by a tsunami" also cover tsunamis that are likely to occur though their occurrence is supposed to be extremely rare on the premise of such uncertainties based on the latest scientific and expert technical knowledge in order to reliably prevent the occurrence of serious disasters. In light of that purport, determinations under the Technical Standards are not limited to those on tsunamis that are reliably predicted based on established views and should be reasonably made from the perspective of prevention of serious disasters on the premise of uncertainties of various factors in the latest knowledge while conservatively (on the safe side) taking into account those uncertainties.

As mentioned above, in consideration of the positions and structures of the Earthquake Research Committee, etc. and the purpose, procedure, content, etc. of the Long-Term Assessment, the Long-Term Assessment does not lack reasonableness as a basis for making such determinations.

(3) A. The Japan Society of Civil Engineers aims at promoting the progress of civil engineering and the development of civil work, etc. In 1999, the Tsunami Evaluation Subcommittee was established under the Nuclear Civil Engineering Committee of the Japan Society of Civil Engineers for the purpose of considering the systematization and standardization of technologies for assessing safety against tsunamis for nuclear power plants. The same subcommittee consisted of members, including the researchers of TEPCO and other electric power companies, in addition to persons with relevant expertise.

The content of the 2002 Tsunami Assessment Method complied by the Tsunami Evaluation Subcommittee is as stated in No. 1, 2. (2) in the holding. The 2002 Tsunami Assessment Method states that the wave source of a tsunami associated with an earthquake that is assumed to occur near the plate boundary is to be set based on the knowledge of seismotectonics. On the premise of the Hagiwara Map, regarding a relatively large structural section in the Hagiwara Map, the 2002 Tsunami Assessment Method states that the wave source of the standard fault model can be set at a further sectionalized position that is considered reasonable in accordance with the form of occurrence of a tsunami based on seismological knowledge, such as the status of occurrence of past earthquakes. The 2002 Tsunami Assessment Method does not set any wave source in the area along the Japan Trench in the offing of Fukushima Prefecture.

B. In terms of the purpose of the Tsunami Evaluation Subcommittee, that is, the systematization and standardization of technologies for assessing safety against tsunamis, the main focus of the 2002 Tsunami Assessment Method is considered to exist in a general technology or method of setting the standard fault model based on previous tsunamis and calculating the water level of a design tsunami by means of numerical calculation, etc. On the other hand, sectionalization of areas for setting the wave source of the standard fault model is an issue that requires detailed consideration of each individual sea area based on various survey and research findings, etc., and it does not appear to have been taken up as a major issue.

In addition, when dividing areas into small sections with emphasis on the status of occurrence of tsunamis in the past while stating in the 2002 Tsunami Assessment Method that the wave source of a tsunami that is assumed to occur near the plate boundary is to be set based on the knowledge of seismotectonics, only previous tsunamis in narrow areas are assumed and the possibility of occurrence of a tsunami in areas where no tsunami has occurred in the past is overlooked. In this regard, the 2002 Tsunami Assessment Method points out differences in seismic activities between the north and south parts of the sea area along the Japan Trench and also cites documents and states that the documents suggest the locations of occurrence of a tsunami earthquake, etc. are limited. However, as mentioned above, it is considered that such views do not necessarily deny the possibility of occurrence of a similar tsunami earthquake in the area of the south part along the Japan Trench. In addition, it does not appear that the 2002 Tsunami Assessment Method also referred to various survey and research findings, etc. which were referred to in the Long-Term Assessment in considering the sectionalization of areas. This is significantly questionable in terms of the standard of reasonableness on which determinations under the Technical Standards should be based.

Furthermore, even in consideration of the position of the Japan Society of Civil Engineers and the structure, procedure, etc. of the Tsunami Evaluation Subcommittee, the way of thinking regarding areas in relation to the setting of a wave source in the 2002 Tsunami Assessment Method is not considered to impair the reasonableness of the Long-Term Assessment.

(4) In addition, when examining circumstances after publication of the Long-Term Assessment, first of all, "Reliability of Long-Term Assessment on Large Earthquakes Associated with Sinking of Plates" published by the Earthquake Research Committee in March 2003 evaluates a section titled "Large Interplate Earthquake (Tsunami Earthquake) near the Trench in the Area from the North Part of the Offing of Sanriku to the Offing of Boso" in the Long-Term Assessment as grade C (slightly low) in terms of both the reliability of assessment on the area of occurrence and the reliability of assessment on the probability of occurrence. However, these evaluations were based on the grounds of insufficient seismic data on the premise that an earthquake similar to the assumed earthquake is expected to occur anywhere in the area. Therefore, they do not affect the evaluation of the reasonableness of the Long-Term Assessment on the premise of the aforementioned uncertainties.

Moreover, among the "Probabilistic Seismic Hazard Maps Covering the Whole Japan" compiled by the Earthquake Research Committee in March 2005 based on previous long-term assessments, etc., the "Probabilistic Seismic Hazard Map for Specified Seismic Source Fault" using a deterministic method does not include tsunami earthquakes along the Japan Trench, which are indicated in the Long-Term Assessment. However, as the "Probabilistic Seismic Hazard Map for Specified Seismic Source Fault" is a map that focuses on a specific seismic source fault and indicates the strength of tremors the area around the fault will face if an earthquake occurs there, it can be considered natural in light of the purport thereof that tsunami earthquakes pertaining to the Long-Term Assessment are not included in the map.

Furthermore, in January 2006, the Expert Committee on Trench Type Earthquakes around the Japan Trench and the Chishima Trench of the Central Disaster Management Council selected earthquakes that should be covered by disaster management measures with a focus on the aforementioned trench type earthquakes and compiled basic matters such as measures against earthquakes, based on assumption of damage due to those earthquakes, in the report of the same committee. In the report, the committee covered large earthquakes that were confirmed to have occurred in the past as earthquakes for which disaster management measures are to be considered, but considered large earthquakes that had not been confirmed to have repeatedly occurred as earthquakes that will occur at a long interval and are unlikely to occur near future, and excluded interpolate earthquakes in the offing of Fukushima Prefecture and the offing of Ibaraki Prefecture, etc. from earthquakes to be examined. However, this selection of subject earthquakes by the committee included a policy determination pertaining to a system to legally oblige the State, local public entities, private business operators, etc. to formulate various disaster management plans, etc. based on the designation of areas by the Prime Minister, and it differs in nature and content from the Long-Term Assessment, which was conducted as part of comprehensive evaluation of research findings, etc. concerning earthquakes.

Therefore, none of these circumstances can be considered to affect the evaluation of the reasonableness of the Long-Term Assessment from scientific and expert technical perspectives.

(5) If the Safety Agency per se assumed or instructed TEPCO to assume a tsunami based on the latest scientific and expert technical knowledge in light of the Long-Term Assessment after publication thereof, as the Estimation can be considered to have been a reasonable estimation as mentioned in the majority opinion, it is considered that a runup of water due to a tsunami similar to the Estimated Tsunami was naturally assumed. Thus, runup waves up to 15.707 m above sea level were assumed to attack the Site, which is 10 m above sea level. Then, it was obvious that if the Site was flooded due to such runup waves in a situation where the external power source was lost, an accident similar to the Accident would be likely to occur due to loss of functions of the Emergency Power Systems, etc.

It is thus found that by around July 2003, one month after publication of the Long-Term Assessment, at the latest, the Minister of Economy, Trade and Industry could recognize that the Nuclear Reactor Facilities would be likely to be damaged by a tsunami and that it would be necessary to issue to TEPCO an order to conform to the technical standards under Article 40 of the Electricity Business Act, even in consideration of the fact that a certain period of time would be required for examining the reasonableness of the Long-Term Assessment and assuming a tsunami based thereon, etc.

5. Possibility of avoiding consequences, etc.

(1) In this case, in determining the illegality of the Minister of Economy, Trade and Industry's failure to exercise the regulatory authority, it is necessary to take into account the issue of whether it can be said that if the same regulatory authority had been exercised, damage due to the Accident or an accident similar thereto would not have occurred.

An order to conform to the technical standards pertaining to the Technical Standards is issued by the Minister of Economy, Trade and Industry to order a person who installs nuclear reactors to take appropriate measures to ensure that the nuclear reactor facilities, etc. conform to the Technical Standards, and it is considered unnecessary to specify the content of measures to be taken in the order. Regarding what measures to take, a person who installs nuclear reactors and received the order must carry forward necessary procedures after specifically considering necessary and appropriate measures to make the nuclear reactor facilities, etc. conform to the Technical Standards. However, it is considered that those measures should be those that are reasonably admitted as necessary and appropriate to reliably prevent the safety functions of the nuclear reactor facilities, etc. from being damaged under specific circumstances, in light of the purport and purpose of laws and regulations.

(2) The ensuring of safety against tsunamis for nuclear reactor facilities in Japan before publication of the Long-Term Assessment was based on the idea of preventing the sites of nuclear reactor facilities where safety facilities, etc. are installed from being flooded. As the Power Station was designed without presupposing that the Site is flooded, it was important, from the perspective of ensuring safety against tsunamis, to prevent runup waves that are assumed based on the Long-Term Assessment from reaching the Site, and it is considered that there was a need to newly install an appropriate seawall, etc. for that purpose.

Regarding such seawall, etc., the majority opinion states as follows: although the height of the Estimated Tsunami exceeded the height of the Site in the southeast front thereof, it never exceeded the height of the Site in the east front thereof; therefore, a seawall, etc. to be designed is highly likely to be one that focuses the most attention on preventing seawater from entering the Site from the southeast side thereof.

However, according to the Estimation, it appears to have been assumed that not only a tsunami well over 10 m above sea level may run up on the south and north sides of the existing breakwater, but a tsunami around 10 m above sea level may arrive at the positions of intake pumps (4 m above sea level) related to the nuclear reactors: Units 1 to 6, of the Power Station, and that a tsunami may also run up to the Site on the north side of Unit 1.

Then, although the parameters of the fault model in the Estimation are on the premise of the fault model of the Meiji Sanriku Earthquake, the model is only one of the models and the values of a fault in a tsunami earthquake that actually occurs do not necessarily correspond to these parameters. Even if uncertainties of the model are alleviated to some degree through parameter study, it is safe to say that it is impossible, in principle, to confirm that values at spots subject to assessment are scientifically accurate. Taking into account the fact that earthquakes and tsunamis change in a complex way according to various conditions and are natural phenomena that are difficult to predict and the fact that research and prediction technologies for them are in the process of development, various values of the Estimation should not be considered to be absolute in the assumption of tsunamis based on the Long-Term Assessment, and it is reasonable to consider that actual values are based on the Estimation but vary to a considerable degree.

Moreover, it is clear that if runup waves due to a tsunami reach the Site, the Emergency Power Systems installed on the first floor or the first basement level of the main buildings will be flooded and stop their functions, the cooling functions of the nuclear reactors will be lost, and this will lead to a serious situation. Therefore, it is necessary to make an assumption in consideration of a safety margin.

Then, it should rather be considered to be natural to assume the possibility of a runup of a tsunami not only from the southeast side of the Site but also from the east side thereof in applying the Technical Standards, taking into account the fact that the Estimation suggests the possibility that a tsunami around 10 m above sea level may reach within the bay of the aforementioned breakwater and part thereof may run up to the Site.

Therefore, if the Minister of Economy, Trade and Industry had issued an order to conform to the technical standards on the premise of the Long-Term Assessment, TEPCO would have had to promptly take measures to install an appropriate seawall, etc. in order to ensure that the tsunami would not run up from the east side of the Site, thereby preventing assumed runup waves from reaching the Site. There was no circumstance that would preclude TEPCO from implementing such measures. Thus, it can be said that there was a high probability that such measures would be implemented.

(3) A. Even if measures against assumed tsunamis based on the Long-Term Assessment were based on the installation of an appropriate seawall, etc., in implementing those measures, it was necessary to carefully consider whether it would be possible to prevent runup waves of tsunamis from reaching the Site by the measures, from scientific and expert technical perspectives. Up until then, it had been a principle to compare the height of assumed tsunamis and that of the site of installation of a nuclear reactor before installing a nuclear reactor. However, in this case, it subsequently became necessary to prevent runup waves from reaching the existing nuclear reactors by installing a seawall etc., and it was necessary to consider the location, height, structure, etc. of a seawall, etc. that should correspond to various conditions that affect wave heights, wave powers, etc. in detail according to the setting of a specific fault model based on the conditions of the ground, the conditions of the existing facilities and installations, etc. It is recognized through presumption that a considerable period of years was required to conduct and complete construction based on such consideration.

Then, until the construction is completed, the nuclear reactor facilities, etc. are likely to be damaged by a tsunami, and the nuclear reactor facilities, etc. will continue to be in the state of not conforming to the Technical Standards. In a situation where the nuclear reactors are operating based on a design that is not premised on the possibility that the Site may be flooded, the existence of the possibility that the Site may be flooded by over 5 m due to a tsunami is by no means an abstract risk but should be considered as a specific and serious risk. In order to prevent the occurrence and expansion of a serious disaster under such circumstances, it is necessary to consider various measures, including temporary shutdown of the nuclear reactors. In particular, in order to maintain the function to continue cooling of the cores or spent fuel pools, maintenance of the functions of the Emergency Power Systems is essential. It is also clear that the Emergency Power Systems are extremely vulnerable to flooding. It should be said that leaving such risk as it is until installation of a seawall, etc. is completed goes against the purport of laws and regulations, that is, ensuring that no serous disaster would occur by any chance.

In addition, as facilities that are especially important to ensure the safety of nuclear reactor facilities, emergency power systems are required to have a multi-layered design, etc. under Guide 9, paragraph (2) of the 1990 Safety Design Review Guide and under the technical standards pertaining to Article 8-2 of the Ministerial Order prior to the 2005 Amendment, and it was necessary to ensure that the functions of emergency power systems can be exerted under all assumable environmental conditions (see Article 8-2, paragraph (2) of the Ministerial Order after the 2005 Amendment). The fact that measures necessary to maintain the functions of the Emergency Power Systems had not been taken although flooding due to a tsunami was actually assumed can also be considered not to have confirmed to the technical standards in this regard, and there was a need to promptly take appropriate measures.

Then, the Emergency Power Systems were installed on the first floor or the first basement level of the main buildings. Therefore, it can be said that in order to maintain their functions against a tsunami, it was necessary to first identify sections where they are located, assume the range and volume of flooding due to a tsunami in relation to the relevant sections and buildings, identify routes through which they can be flooded and openings from which they are flooded (doors, opening sections, path-through slots, etc.), and take measures to prevent flooding, such as water-tightening.

It seems that measures, such as a certain level of water-tightening, had been taken at nuclear reactor facilities in Japan and abroad before that time, and it is considered that there was technical knowledge on prevention of flooding in relation to doors, opening sections, path-through slots etc. It is considered to have been sufficiently possible to take measures, such as water-tightening, by considering various conditions that affect wave heights, wave powers, etc. according to the setting of a specific fault model based on such knowledge and by examining performance, etc. of necessary and appropriate facilities while considering a safety margin in relation to uncertainties. In addition, it is easily recognized through presumption that such work for facilities could be completed sufficiently earlier than civil work, that is, the aforementioned installation of a seawall, etc.

B. The majority opinion states as follows: knowledge before the Accident does not suggest any circumstance where it should be considered that merely installing an appropriate seawall, etc. was insufficient as a measure against tsunamis in the case where the site of nuclear reactor facilities where safety facilities, etc. are installed was assumed to be flooded due to a tsunami; therefore, it cannot be said that other measures were probably taken.

However, regarding assessment of safety against tsunamis, both the Former Safety Design Review Guide and the 1990 Safety Design Review Guide have only set comprehensive and abstract guides for natural phenomena other than earthquakes for over 30 years and have not established any specific guide for the method of assuming occurrence and protecting against tsunamis. The majority opinion emphasizes that measures against tsunamis before the Accident were based on the idea of preventing seawater from entering the site by installing a seawall, etc. in the case where the site was assumed to be flooded due to a tsunami. However, there were no guides to such effect, as well as laws and regulations stipulating such idea. In addition, it does not appear that a permission for installation of a nuclear reactor, etc. had ever been given on the premise that flooding of the site is prevented by installation of a seawall, etc. before publication of the Long-Term Assessment. It should be said that measures assuming that flooding may occur due to a tsunami had not been sufficiently considered up to then based on the idea that safety would be ensured by installing the nuclear reactor facilities at a sufficiently high place where assumed runup waves would not reach. The fact that it subsequently became indispensable to install a seawall, etc. in order to prevent flooding due to a tsunami, which had not been assumed up to then, was just an unprecedented situation, and TEPCO came to assume the legal obligation to take appropriate measures to prevent even extremely rare disasters in immediate response to such situation. Measures to be taken in accordance with the Technical Standards should include those that are reasonably admitted as necessary and appropriate to reliably prevent such disasters under specific circumstances on the premise of the Long-Term Assessment, and there is no reason for excluding such measures from consideration of probability.

C. When considering this case from such perspective, first, there was no specific guide for evaluating the adequacy of a design policy in relation to an idea based on the prevention of flooding due to a tsunami of the site of nuclear reactor facilities where safety facilities, etc. are installed. However, in order to maintain a design that is not premised on flooding due to a tsunami as an adequate one, prevention of flooding must be at least reliable. However, originally, tsunamis are natural phenomena that are difficult to predict, and scientific technologies relating to them are also in the process of consistent development. Under such circumstances, even though a tsunami was assumed based on the latest knowledge, it is generally difficult to deny the possibility of occurrence of a tsunami exceeding the assumed tsunami. In addition, no specific guide for the method of assuming and protecting against tsunamis had been established over the years based on reliable grounds from scientific and expert technical perspectives, and this indicates the uncertainties of assessment of safety against tsunamis in comparison with detailed guides for the standard earthquake motion and seismic design, etc. in relation to seismic safety, and it was an important issue relating to evaluation of design policies.

Furthermore, an appropriate estimation based on the Long-Term Assessment led to the assumption of a tsunami that significantly exceeded the past assumptions, specifically, a tsunami with a height over five times the water level of the design tsunami (3.122 m above sea level) at the time of permission for installation, in relation to nuclear reactors that were in operation. It thus became clear that at the Power Station, flooding of the Site had not been reliably prevented by measures based on the assumptions of tsunamis based on the knowledge of the times for over 30 years and that the nuclear reactors had been continuously operated under extremely dangerous conditions. It is safe to say that this fact turns upside down the safety that had been considered to have been ensured until then and indicates that the safety was merely a "myth." Such serious risk associated with safety assessment is an issue that may shake the adequacy of the design policy, and it must be said that special consideration to alter the design policy was necessary in applying the Technical Standards.

Even based on a new assumption, the Long-Term Assessment and the Estimation are pieces of knowledge that should continue to be advanced and developed and are not spared from uncertainties though they were reasonable in light of the scientific and technical levels of the time. In fact, the Long-Term Assessment is premised on the compilation of information about earthquakes after the 17th century and does not deny the possibility of occurrence of a tsunami at longer intervals, etc. based on a scientific ground. In particular, in relation to the 869 Jogan Earthquake, it appears that many experts had been accumulating researches, including a survey on the traces of strata on the coast of the Tohoku region. In addition, from the perspective of various safety margins that should be taken into account in assessment of safety against tsunamis, no specific guide for design policies had been established over a long period of time. Moreover, there are no circumstances to consider that new estimates, etc. that might prevent the flooding could be found based on a reliable ground on the premise of the process of development of science and technology that brought about a change of five times in the size of the assumed tsunami under a situation where prevention of the flooding had not been ensured. It also does not appear that such new estimates , etc. were found even after the Estimation was obtained. Even if the Estimation had a certain level of conservativeness due to parameter study, it clearly does not affect the aforementioned points.

The risk of flooding indicated under such circumstances is a real issue that would cause serious harm to the lives, physical health, etc. of many people though it is rare. In light of the purport of laws and regulations, that is, to reliably prevent irreversible serious disasters, it had become difficult to find the reasonableness in maintaining a design that was not premised on flooding due to a tsunami without any change. It should be said that mere installation of a seawall, etc. on the premise of an assumed tsunami was not considered sufficient as measures to be taken in accordance with the Technical Standards and that multiple-layered protection also with preparation for the risk of flooding of the Site due to a tsunami should have been considered even though the risk would be very rare. Additionally, the Emergency Power Systems were installed on the first floor or the first basement level of the main buildings, and it was clear that all of their functions were highly likely to be lost due to a single factor, an attack of a tsunami that causes the flooding of the Site. Thus, the necessity of multi-layered protection of the Emergency Power Systems was especially high.

Putting these circumstances together, in relation to the application of the Technical Standards, it can be said that the aforementioned measures, such as water-tightening, were necessary and appropriate to maintain the functions of the Emergency Power Systems until the completion of the installation of a seawall, etc. and were also necessary and appropriate to promote the multi-layered protection of the Emergency Power Systems after the completion of the installation.

The necessity of multi-layered protection against such situation that goes beyond the scope of the assumption is reasonably recognized based on an appropriate estimation based on the Long-Term Assessment under specific circumstances where the safety that had been considered to have been ensured until then was turned upside down, without the need to wait for the occurrence of the Accident. It is thus considered that TEPCO and the Safety Agency were sufficiently able to recognize the necessity through sincere consideration in accordance with laws and regulations. In addition, it appears that such estimation had not been published before the Accident, and even if specific discussions by experts, etc. on the premise of the estimation were not widely seen in such situation, it rather makes sense and does not serve as a reason for denying the necessity of multi-layered protection, etc. as mentioned above.

Therefore, if the Minister of Education, Trade and Industry had issued an order to conform to the technical standards, TEPCO would have had to promptly take the aforementioned measures, such as water-tightening. There is also no circumstance that precludes TEPCO from implementing such measures. Therefore, it can be said that such measures probably would have been implemented.

D. In general, in relation to an accident associated with ordinary business activities, it is often difficult to find the duty of care to take safety measures, etc. that business operators have not been legally obliged to take and that many business operators have not taken. However, this case is not such case. Owing to publication of the Long-Term Assessment, it was possible to recognize over eight years before the Accident that the Nuclear Reactor Facilities did not conform to the Technical Standards under the laws and regulations of the time, and TEPCO had assumed the legal obligation to take appropriate measures to prevent even extremely rare disasters. Then, where TEPCO is required to certainly perform the obligation by an order to conform to the technical standards, the issue is what measures to take. Under unprecedented circumstances in relation to the basic method of safety assessment, such as where the fact that a long-standing serious risk associated with safety assessment became clear, it was necessary to examine not only measures taken and the design policy up until then but also the content required under the Technical Standard based on the purport of the aforementioned laws and regulations.

However, the appellant erred in the interpretation of the aforementioned laws and regulations concerning the regulatory authority pertaining to an order to conform to the technical standards, and in fact, the same order was never issued. In addition, both the Safety Agency and TEPCO did not promptly conduct examination of the assumption of tsunamis based on the Long-Term Assessment after publication thereof. Moreover, although TEPCO recognized the Estimation more than five years later, it did not promptly materialize necessary measures, including installation of a seawall, etc., and continued to operate the Nuclear Reactor Facilities until just before the Accident about three years later without reporting the Estimation to the Safety Agency. As seen above, it is clear that these relevant persons had not appropriately conducted examinations on the premise of performance of the aforementioned legal obligation until occurrence of the Accident, and there is no choice but to say that for this reason, incorrect safety assessment had been maintained as it was and that the aforementioned laws and regulations relating to the lives and daily living of residents living around the nuclear reactor facilities, etc. had been ignored.

The majority opinion denies the necessity and probability of the aforementioned measures, such as water-tightening, based on recognition and knowledge in such circumstances without mentioning the purport and interpretation of the aforementioned laws and regulations at all. This was on the premise of an idea that had not been appropriately considered by relevant persons based on safety assessment that had overlooked a serious risk over a long period of time, without any change, and it must be considered to have lacked consideration to reasonable recognition based on the interpretation and application of the aforementioned laws and regulations, etc. Insufficient recognition, etc. associated with inaction and negligence as mentioned above should not serve as a ground for denying the necessity, etc. of appropriate measures that are required under the Technical Standards.

(4) A. On the premise of the Long-Term Assessment and the idea that if the Minister of Education, Trade and Industry had issued an order to conform to the technical regulations, TEPCO would have probably taken measures, such as water-tightening, as well as installation of a seawall, etc., I consider whether it can be said that the Accident or an accident similar thereto would not have occurred due to loss of functions of the Emergency Power Systems as a result of flooding of the Site caused by the Tsunami.

B. First of all, as mentioned above, the Minister of Economy, Trade and Industry could recognize the necessity of issuing an order to conform to the technical standards to TEPCO by around July 2003. If the Minister had issued the order by around July 2003, there was a period of over seven years and six months before the Accident. Therefore, it is recognized through presumption that all the aforementioned measures would have been completed before the Accident.

C. When looking at the Earthquake and the development of the Accident in association with it based on the above, the outline thereof is as stated in No. 1, 2. (6) in the holding. It is found that loss of functions of all the Emergency Power Stations due to the Tsunami was caused by the entry of the Tsunami into the turbine buildings and the shared facility for assisting operation (shared pool) pertaining to the Nuclear Reactors, and the routes of the entry are considered to have been the entrances, opening sections, etc. of the buildings. Therefore, if measures, such as water-tightening, had been appropriately taken for important sections pertaining to the Emergency Power Systems and the buildings of the Emergency Power Systems, those measures would have brought about important effects in preventing the Emergency Power Systems from losing their functions due to the flooding.

On the other hand, the Earthquake was far larger in size than the earthquake assumed in the Long-Term Assessment, and the Tsunami was also observed in an extremely broad area centering on the Pacific side from the Tohoku region to the north part of the Kanto region. The issue here is whether it can be said that there was no possibility of occurrence of the Accident or an accident similar thereto due to the Tsunami based not on differences in the size, etc. of the earthquake or tsunami between the Tsunami and the tsunami assumed based on the Long-Term Assessment but on differences in the possibility of loss of functions of the Emergency Power Systems due to flooding. There is no sense of emphasizing the aforementioned differences in size, etc. apart from this point.

When considering this case from that perspective, the depth of flooding near the main buildings due to the Tsunami was 1.5 to 5.5 m. The estimated depth of flooding near the main buildings due to the Estimated Tsunami was about 2.0 to 2.6 m near the nuclear reactor building and turbine building of Unit 4. In addition, it seems that the depth of flooding near the shared facility for assisting operation (shared pool) installed on the southwest side of the nuclear building of Unit 4 was close to 5 m.

In addition, although the Tsunami also ran up from the east side of the Site, no significant damage due to the Tsunami was confirmed on the external walls, pillars, and other structural frames of the main buildings. In addition, almost no measures, such as water-tightening, had been taken at the turbine buildings of the Nuclear Reactors at the time of the Accident, and the entrance for carrying in large items facing the east side also had an extremely vulnerable structure. Nevertheless, the buildings seem to have fulfilled certain protection function against the entry of water of the Tsunami. Furthermore, although the air supply louvers of the emergency diesel generators were open on the ground, it is difficult to consider that the wave power, etc. of the Tsunami affected the entry of water from the louvers and the resulting pouring of water over the emergency diesel generators.

Then, if the aforementioned measures, such as water-tightening, are taken based on the Minister of Economy, Trade and Industry's order to conform to the technical standards, it is natural to make an appropriate design in consideration of a safety margin on the premise of various conditions, such as the maximum depth of flooding due to the Estimated Tsunami. Therefore, it is considered that if those measures, such as water-tightening, had been taken, measures could have also achieved the sufficient effect of protecting the Emergency Power Systems against the Tsunami.

Furthermore, if installation of a seawall, etc. had been completed, even if part of the Tsunami would have gone beyond the seawall, etc. and entered the Site, the volume of flooding would have been reduced to a considerable extent compared to the case of the Accident where no seawall, etc. had been installed. This clearly further assured the protective effect of measures, such as water-tightening.

D. Giving comprehensive consideration to these circumstances, it can be said that if the Minister of Economy, Trade and Industry had issued to TEPCO an order to conform to the technical standards under Article 40 of the Electricity Business Act on the premise of the Long-Term Assessment, the Accident or an accident similar thereto would probably have not occurred.

Although the Long-Term Assessment did not assume the occurrence of a super great earthquake due to interlocking of multiple areas like the Earthquake, the entire assumption is not considered to have never existed by the word "beyond the scope of the assumption." If the Safety Agency and TEPCO conducted sincere examinations in accordance with laws and regulations in immediate response to a situation on the premise of the Long-Term Assessment, they could have taken appropriate actions and were likely to have avoided the Accident thereby. We must not lose sight of the issue due to obsession with the size, etc. of the Earthquake and the Tsunami.

6. Status of actions taken by the Safety Agency, etc.

(1) Taking into account the fact that there are unexplained points in natural phenomena relating to earthquakes and tsunamis and that various research and prediction technologies therefor are constantly advancing and developing, the Minister of Economy, Trade and Industry must always precisely understand the status of progress of such knowledge and utilize it in order to appropriately exercise the regulatory authority under Article 40 of the Electricity Business Act. The situation where nuclear reactor facilities in operation are found to be likely to be damaged by a tsunami is actually a situation involving a specific risk though the risk is extremely rare. Therefore, it was necessary for the Minister to exercise the aforementioned authority appropriately on a timely basis by determining the fulfillment of relevant requirements as promptly as possible in immediate response to the latest scientific and technical levels.

(2) A. After publication of the Long-Term Assessment, the Safety Agency requested TEPCO to explain about the safety, etc. of the Power Station. However, in early August 2002, the Safety Agency received the following explanation from TEPCO: no tsunami earthquake has occurred in the offing of Fukushima Prefecture since the beginning of recorded history; and tsunami earthquakes are extremely special earthquakes that occur only in specific areas and under specific conditions. Therefore, the Safety Agency instructed TEPCO to confirm on what grounds the Earthquake Headquarters indicated the Long-Term Assessment.

After that, TEPCO heard the opinion of one of the members of the Trench Type Subcommittee and gave the following explanations to the Safety Agency in late August 2002: the same member said that he/she raised an objection at the Trench Type Subcommittee but that the subcommittee reached the conclusion that tsunami earthquakes can occur anywhere; according to a deterministic consideration based on the method adopted by the Japan Society of Civil Engineers, tsunami earthquakes cannot be assumed to occur in the area from the offing of Fukushima Prefecture to the offing of Ibaraki Prefecture; and the issue of tsunami earthquakes can be handled based on probability theory, so TEPCO intends to deal with the issue that way. The Safety Agency accepted these explanations.

B. In light of the reasonableness of the Long-Term Assessment, etc., it is clear that such explanations by TEPCO are not based on appropriate grounds. Thus, the Safety Agency is considered to have just accepted the explanations without sufficiently confirming and considering this point by itself.

The Earthquake Research Committee was established in the government under the provisions of laws as a specialized organization that conducts comprehensive evaluation, etc. of the results of surveys on earthquakes, etc. in order to promote strengthening of earthquake disaster management measures, etc. The Earthquake Research Committee compiled the Long-Term Assessment as part of the aforementioned comprehensive evaluation in order to promote strengthening of earthquake disaster management measures. Therefore, it was necessary for the Safety Agency to sufficiently consider the reasonableness of the Long-Term Assessment and the assumption of a tsunami based thereon, etc. as promptly as possible and to also strongly request TEPCO to do so.

The Safety Agency's actions immediately after publication of the Long-Term Assessment were far from those taken with the attitude of voluntarily understanding the latest knowledge, determining the fulfillment of the requirements under the Technical Standards, etc. based thereon as promptly as possible, and fulfilling its own obligations relating to the exercise of the legal authority.

(3) After that, the Safety Agency received reports on the circumstances of flooding accidents due to tsunamis, etc. at overseas nuclear power plants and the results of examinations on flooding due to a tsunami at the Power Station at the Safety Information Conference and the Overflow Water Workshop, which it established in collaboration with the Japan Nuclear Energy Safety Organization. Accordingly, the Safety Agency could sufficiently recognize that the risk of flooding due to a tsunami is a real issue, and the necessity of considering the Long-Term Assessment and taking actions therefor thus became clearer. Nevertheless, the Safety Agency postponed such measures in the form of leaving them to the anti-seismic backcheck.

The anti-seismic backcheck was conducted by the Safety Agency as an administrative guidance to persons who install nuclear reactors in order to assess and confirm safety based on the 2006 Seismic Design Review Guide, and it is difficult to say that the backcheck was intended to have TEPCO take necessary measures based on the Long-Term Assessment to ensure that the nuclear reactor facilities, etc. conform to the Technical Standards. In addition, TEPCO had not submitted the final report pertaining to the Power Station even after about four years and six months passed from the Safety Agency's instruction. Under such circumstances, the Accident occurred.

(4) As mentioned above, the appellant erred in the interpretation of Article 40 of the Electricity Business Act, and the Safety Agency also does not seem to have specifically considered the fulfillment of the requirements under the Technical Standards, etc. and have made a determination thereon at any time after publication of the Long-Term Assessment. This is equivalent to the situation that there was practically no organization that should take charge of the exercise of the regulatory authority under law.

7. Illegality of the Minister of Economy, Trade and Industry's failure to exercise the regulatory authority

Comprehensively considering the aforementioned circumstances, the Minister of Economy, Trade and Industry should have found, by around July 2003, that the Nuclear Reactor Facilities might be damaged by a tsunami and that they did not confirm to the Technical Standards as no appropriate measures had been taken, and should have issued to TEPCO an order to conform to the technical standards by exercising the regulatory authority under Article 40 of the Electricity Business Act. The Minister's failure to exercise the aforementioned regulatory authority after around July 2003 is extremely unreasonable in relation to residents living around the nuclear reactor facilities, etc. in light of the purport and purpose of laws and regulations and the nature, etc. of the authority, and it should be considered to be illegal in terms of the application of Article 1, paragraph (1) of the State Redress Act.

8. Conclusion

As mentioned above, the Minister of Economy, Trade and Industry's failure to exercise the regulatory authority in this case is illegal in terms of the application of Article 1, paragraph (1) of the State Redress Act after around July 2003. In addition, at this time, the Minister of Economy, Trade and Industry's negligence is also found, and a cause-and-effect relationship is also found between the aforementioned failure to exercise and the Accident. Therefore, the appellant is not exempted from the responsibility to compensate loss or damage under the same paragraph.

It is, needless to say, TEPCO that primarily assumes the responsibility for the safety management of the Power Station, and in that regard, the appellant's responsibility can be considered to be secondary. However, the installation and operation of nuclear power plants are based on an energy policy that is essential for the maintenance and development of the people's daily lives and national economy as part of use of nuclear power, and ensuring of the safety of nuclear power plants has also been based on the assumption that the appellant takes all possible measures to prevent the occurrence of serious disasters through regulations at the stage of permission for installation and subsequent stages. Taking into account the fact that the Minister of Economy, Trade and Industry's order to conform to the technical standards in this case is also part of the important regulatory authority granted to ensure the safety of nuclear reactor facilities in operation for the purpose of preventing harm to the lives and physical health of residents living around the facilities, etc., there is no reason for limiting the scope of the appellant's responsibility to part of damage pertaining to the appellees stated in in Lists of Appellees 2 to 6 attached to this judgment.

Therefore, it is reasonable to consider that the appellant and TEPCO assume the responsibility for the entire damage pertaining to the same appellees, respectively, and that the appellant and TEPCO have the relationship of non-authentic joint and several obligation.

For the reasons described above, the determination of the court of prior instance that affirmed the aforementioned responsibility to compensate loss or damage of the appellant can be accepted. The counsel's arguments are not acceptable.

Justice KANNO Hiroyuki

Justice MIURA Mamoru

Justice KUSANO Koichi

Justice OKAMURA Kazumi