{"id":8803,"date":"2025-12-21T15:11:40","date_gmt":"2025-12-21T06:11:40","guid":{"rendered":"https:\/\/cnic.jp\/english\/?p=8803"},"modified":"2025-12-22T18:09:24","modified_gmt":"2025-12-22T09:09:24","slug":"questioning-the-obsolescence-of-nuclear-power-plants-part-1-lawsuit-to-revoke-the-permits-for-operating-lifetime-extensions-for-takahama-units-1-2-and-mihama-unit-3-an-unjust-verdict-unable","status":"publish","type":"post","link":"https:\/\/cnic.jp\/english\/?p=8803","title":{"rendered":"Questioning the Obsolescence of Nuclear Power Plants – Part 1. Lawsuit to Revoke the Permits for Operating Lifetime Extensions for Takahama Units 1 & 2 and Mihama Unit 3: An unjust verdict unable to grasp the warnings about brittle failure"},"content":{"rendered":"\n

By Shibayama Yasuko (The Group of Citizens\u2019 Seeking a Court Decision Ordering the Decommissioning of Nuclear Plants Over 40 years Old)<\/p>\n

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Lawsuit to Decommission Aging Nuclear Reactors at 40 Years: An administrative lawsuit seeking the revocation of licenses and permits for extending the operating periods of Units 1 and 2 at the Takahama Nuclear Power Plant and Unit 3 at the Mihama Nuclear Power Plant, all of which have been in operation for more than 40 years. The national government (Nuclear Regulation Authority) is the defendant, and Kansai Electric Power Company is an intervener in the lawsuit. There are four main issues: (1) Aging (neutron irradiation embrittlement of reactor vessels, electrical cables), (2) Earthquakes, (3) Volcanoes, and (4) Others, including the absence of a review of the storage of spent nuclear fuel and the securing of final disposal sites for nuclear waste. The results of the examination of witnesses on neutron irradiation embrittlement were reported in CNIC Tsushin No.604 (2024\/10\/1). The judgment and statement of grounds for appeal are posted on the website toold-40-takahama.com<\/a>.<\/em><\/span><\/p>\n

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Just as I thought. [The judge] was already thinking about the plot of the verdict during the examination of witnesses…. The content of the judge\u2019s questions I had been concerned about during the examination of witnesses appeared time and time again in the text of the verdict.<\/p>\n

In the lawsuit to revoke the permits for operating lifetime extensions for Kansai Electric Power Company\u2019s (Kanden\u2019s) Takahama Units 1 & 2 and Mihama Unit 3, the Civil Case Section 9 (Special Section for Administrative Lawsuits) of Nagoya District Court failed to face up to the realities of the serious damage brought about by the nuclear accident at Fukushima Daiichi Nuclear Power Station (FDNPS) and handed down an unjust verdict that merely confirmed the sloppy and irresponsible licenses and permits handed out by the Nuclear Regulation Authority (NRA), which differ little from those of the time before accident. With content that looked as if it was simply copied outright from the claims of defendant, the government (in the form of the NRA), the verdict even went so far as to state regarding the nuclear fuel cycle that \u201cefforts are continuing, and thus it cannot be said that that the nuclear fuel cycle has failed.\u201d This was therefore a verdict that exhibited nothing more than blind faith in the government\u2019s policies. We will, naturally, appeal, and the Nagoya High Court proceedings have already begun.<\/p>\n

\u00a0<\/p>\n

The verdict was unable to face up to the realities of the damage caused by the nuclear accident<\/strong><\/p>\n

The tremendous and serious damage caused by the FDNPS nuclear accident were brought up many times during the lawsuit, and we appealed strongly to the judge that nuclear regulation and judicial decisions must prevent this kind of accident from ever occurring again.<\/p>\n

In the roughly 380 pages of the text of the verdict (Takahama case), however, a mere one page was given to statements about the FDNPS accident. Moreover, only an overview of the accident was given, with no statement at all about the damage. The overview of the accident in the verdict did not touch upon the reality that, even so, this accident was not the worst possible accident that could have been assumed, a point that we emphasized during the trial.<\/p>\n

In the accident, cooling of the Unit 4 spent fuel pool, to which cooling water could not be supplied, had been possible at an early stage because it appears that, due to a delay in work, water had flowed into the pool through a gap that had somehow formed in the partition with the well in the adjacent reactor, which had been filled with water. As a result of this incredible coincidence, the annihilation of eastern Japan (the so-called \u201cworst-case scenario\u201d of Kondou Shunsuke, NRA Chairperson at the time of the accident) was avoided, but this was ignored by the verdict.<\/p>\n

\u00a0<\/p>\n

A verdict unable to look directly at the realities of the failed nuclear fuel cycle<\/strong><\/p>\n

In the lawsuit, based on the risks of spent fuel pools and spent nuclear fuel, which became a reality during the FDNPS accident, we pursued the illegality of the fact that there had been no deliberations on storage safety, treatment or disposal when the extension of the operating lifetime of the plant for a huge 20 years had been approved. The reality is that remaining storage space in the spent fuel pools at Kanden\u2019s nuclear power plants (NPPs) is reaching its limits, with only three years left before the spent fuel pool at Takahama becomes full. For many years, Kanden has been promising Fukui Prefecture that it will transport its spent nuclear fuel outside the prefecture, but there is as yet no prospect of an interim storage facility being constructed outside the prefecture, and with the nuclear fuel cycle having collapsed, Kanden is gradually attempting to construct dry storage facilities on the grounds of its NPPs.<\/p>\n

The Nagoya District Court, however, judged that even though the fast breeder reactor Monju has been decommissioned, the nuclear fuel cycle has not collapsed and that a policy for the appropriate management of spent nuclear fuel has been discussed.<\/p>\n

We strongly protest the decision to support the reckless and foolhardy policy of a nuclear renaissance that attempts to use aging NPPs for as long as possible despite there being no place for spent nuclear fuel to go!<\/p>\n

In the statement of grounds for appeal, we have strengthened the arguments regarding the problems of the failure of the nuclear cycle and the lack of disposal sites for spent nuclear fuel.<\/p>\n

\u00a0<\/p>\n

We wanted the court to recognize the revocation of permission for Takahama Unit 1, where the fear of brittle failure is rising<\/strong><\/p>\n

When we think that in cases where there are specific circumstances that do not impact other NPPs it is easy for judges to revoke licenses and permits of NPPs, or issue injunctions to block their operations, we were hopeful that we could at least possibly win the case on the basis of the severe embrittlement of the Takahama Unit 1 reactor vessel and the problem of the extreme proximity of a hypocenter (seismic center) to Mihama Unit 3.<\/p>\n

The steel in the heart of an NPP, the steel reactor vessel that contains the nuclear fuel, becomes brittle after many years of neutron bombardment. This is known as neutron irradiation embrittlement<\/em>.<\/p>\n

Takahama Unit 1 (now 51 years since its start of operation) has the highest value for neutron irradiation embrittlement of the reactor vessel of all NPPs in Japan.<\/p>\n

To monitor progress in neutron irradiation embrittlement, monitoring test specimens made from the same steel material as the reactor vessel are placed inside the reactor and are removed once every ten years or so for inspections. Regulations stipulate that from the results of the inspection and by use of a prediction formula, a predictive assessment is to be drawn up stating how brittle the reactor vessel will become if operation is continued in the future. Why does this need to be done? In the case of coolant water not reaching the reactor vessel due to rupturing of piping in an earthquake, the emergency core cooling system (ECCS) will activate, and the reactor vessel will contract when it is cooled very rapidly with coolant water. A strong tensile stress will then occur due to the temperature difference between the inner and outer surfaces of the reactor vessel. If there are fissures on the inner surface, the stress will widen the fissures, and if the reactor vessel has become brittle, this will result in brittle failure.<\/p>\n

For the assessment method of the future prediction of embrittlement, NRA has adopted the standard created by the Japan Electric Association, but this assessment method has various problems that lead to underestimations. Even using the current method, the embrittlement prediction for 60 years from the start of operation for Takahama Unit 1 is quite severe, approaching closely to the brittle failure danger line. Assessing more appropriately on the conservative (safer) side, the reactor vessel had already entered the brittle failure area at the time of the 50th year assessment (at the end of 2022), a fact that we made abundantly clear during the lawsuit.<\/p>\n

However, the judge, based on the claims of the defendant, decided that the assessment method was not unreasonable.<\/p>\n

* Assessment for Pressurized Thermal Shock Events Required under the Regulatory Standards<\/em><\/span><\/span>
When the Emergency Core Cooling System (ECCS) activates in the case of ruptured piping, etc., the nuclear reactor vessel contracts as it is rapidly cooled by coolant water, setting up strong tensile stress between the inner and outer surfaces of the reactor vessel due to temperature difference. This is termed pressurized thermal shock (PTS) and is indicated by the curve that curves upward and then downward from the bottom right toward the left of Fig. 1.<\/em><\/span><\/p>\n

\"\"<\/a>

Fig.1. The Two Curves of the PTS Assessment*<\/span><\/p><\/div>\n

If there are fissures on the inner surface, these fissures will be subject to a force that expands them. The curve that assesses the toughness of the reactor vessel steel to withstand this force is termed the fracture toughness transition curve, which is indicated as a curve that rises from left to right in Fig. 1. As the reactor vessel becomes brittle due to neutron irradiation embrittlement, the fracture toughness transition curve shifts to the right. Assuming that there are fissures in the reactor vessel, an assessment is conducted to predict whether or not the PTS will exceed the toughness of the reactor vessel (whether or not a dead cross will occur). A dead cross signifies brittle failure of the reactor vessel.<\/em><\/span><\/p>\n

\"\"<\/a>

Fig. 2. Takahama Unit 1 PTS Assessment \u2013 Absolutely no remaining margin**<\/span><\/p><\/div>\n

** In 2024, a pressurized thermal shock transition curve without cladding that Kanden had prepared in response to a court request was superimposed on the PTS assessment of the 50th year monitoring test result that Kanden had published for Takahama Unit 1. In the 50th year assessment, the fracture toughness transition curve and the pressurized thermal shock transition curve came extremely close to each other.<\/em><\/span>
As the cladding (a stainless steel lining welded to the inner surface of the reactor vessel by overlay welding) performs the role of insulating material, if the thermal conductivity analysis (temperature distribution analysis) of the cladding is considered, PTS is reduced. At the same time, as stainless steel (cladding) contracts more easily than carbon steel (the material of the reactor vessel) the stress is greater, and thus PTS rises.<\/em><\/span><\/p>\n

The plaintiffs claimed that since there was no mention of cladding in the regulations, the assessment should be conducted without taking cladding into consideration and assuming fissures on the inner surface.<\/p>\n

Kanden\u2019s assessment made use of the beneficial effect of cladding to reduce PTS by considering the thermal conductivity analysis of the cladding, but then failed to consider the stress analysis of the cladding (to avoid showing a rise in PTS).<\/p>\n

\u00a0<\/p>\n

\u201cWhen in doubt, err on the side of the operation of aging NPPs\u201d<\/strong><\/p>\n

Eight monitoring test specimen capsules have been inserted into the reactor vessels of Takahama Units 1 & 2 and Mihama Unit 3, each capsule containing 44 Charpy test specimens, four fracture toughness test specimens, and four tensile test specimens. Charpy test specimens and fracture toughness test specimens are used to conduct the embrittlement prediction. The Charpy test is a simple test in which absorbed energy is measured when test specimens are fractured by a falling pendulum. The fracture toughness test, in which test specimens are stretched by a machine to measure the toughness of the material, gives more accurate measurements, but as the fracture test specimens are large, only a few of them can be placed in each capsule. In embrittlement prediction, the data gained from the Charpy test specimens is used as an alternative and a method of shifting the prediction curve is employed. However, when it was claimed in this lawsuit that this method gives underestimations, this was backed up by data from an actual reactor vessel published by NRA in July 2023, becoming one of the main points of contention in the witness examinations in the first trial. *1<\/em><\/span><\/p>\n

While the verdict recognized to some extent this feature of the actual reactor vessel data, it stated that this did not constitute specialist knowledge that would serve to negate the current method. Despite the plaintiffs demonstrating the underestimation based on specialist knowledge, the witnesses for the defendant avoided any judgement concerning the data. The plaintiffs made the appeal that, at a time such as this, the judiciary should make decisions based on the notion of \u201cwhen in doubt, err on the side of safety,\u201d that is, they should make judgements that take into account conservative (safe) knowledge, or knowledge that warns of risks, but in fact judgements were based on \u201cwhen in doubt, err on the side of the operation of aging NPPs.\u201d<\/p>\n

*1 See the report on the examination of witnesses in CNIC Tsushin No.604 (2024\/10\/1) cnic.jp\/59821<\/a><\/em><\/span><\/p>\n

\u00a0<\/p>\n

The “conditions added to the technical assessment” which made the assessment method for future prediction of neutron irradiation embrittlement acceptable<\/strong><\/p>\n

At the end of the witness examination of the witness for the plaintiffs, Ino Hiromitsu (Professor Emeritus of the University of Tokyo, Metallugical Science), there were questions from Judge Sakuma Takashi, who appears to have been making a mental draft of the verdict. He asked several questions, which included, \u201cThe fracture toughness test specimens taken from the reactor are ones that have undergone future accelerated irradiation are they not? Test specimens that indicate a future state <\/u>which has received more radiation than the current amount of radiation can be taken out, can they not?\u201d \u201c(The Charpy test specimens may have the problem of insufficient shift, but since the fracture toughness test specimens do not have this problem) the future state can thus be confirmed, so is there any problem with taking out new ones and confirming the situation after 60 years?\u201d \u201cIs it possible for the specimens that have undergone 60 years\u2019 worth of accelerated fractionation to be taken out in the near future?\u201d<\/p>\n

The defendant claimed that there was no problem with the awareness that since the monitor test specimen capsule has been inserted in a position closer to the nuclear fuel than the reactor wall, it receives more radiation than the reactor wall, and thus by taking test specimens out and examining them, future embrittlement of the reactor wall can be forecast. Moreover, predictions further into the future could be made by taking out the next test specimens before the amount of radiation received by the removed test specimens had reached the reactor wall.<\/p>\n

The verdict contains several statements to the effect that there is no problem, since \u201cthere is the condition (hereafter \u201cthe condition added to the technical assessment\u201d) that new test specimens are taken out before the degree of neutron irradiation received by the monitoring test specimens taken from various nuclear reactor facilities exceeds the degree of neutron irradiation at the inner surface of the nuclear reactor pressure vessel, the related temperature is re-estimated at a specific point in time using additional data.\u201d Giving an overview of these statements:<\/p>\n