Kashiwazaki-Kariwa Units 1 and 5 Rushing to restart while important safety questions remain unanswered Nuke Info Tokyo No. 137
It is three years since the Chuetsu-oki Earthquake struck the Kashiwazaki-Kariwa Nuclear Power Plant (KK). (See CNIC statement on page 5.) Since then two reactors (Units 6 & 7) have resumed commercial operations and Unit 1, which began start up tests on May 21 and reached full power on June 15, is set to become the third.
On July 7, Niigata Prefecture’s subcommittee looking into equipment integrity and earthquake resistance and safety held its 41st meeting. The subcommittee, which was established under Niigata Prefecture’s technical committee, discussed a report submitted by Tokyo Electric Power Company (TEPCO) about the state of implementation of functional tests at KK-1. TEPCO submitted the report to the Nuclear and Industrial Safety Agency (NISA) on the same day.
The subcommittee also considered five open questions relating to four penetrating cracks in the reinforced concrete wall of the turbine building of KK-5. The questions were submitted by eight groups from Niigata Prefecture. It was the first time that the subcommittee had officially considered questions submitted by citizens.
TEPCO claims that all 83 irregularities identified in KK-1 are minor and that they were not caused by the earthquake.
Two problems arose on May 22, the day after start up tests began. There were problems with humidification control by the dehumidification cooler in the off-gas treatment system, and there was also a fault in the reactor feedwater pump bypass valve. Then on May 28, an oil leak from the MG set oil filter in the recirculation system of the reactor cooling system was discovered. TEPCO fixed these problems by May 30 and increased power in steps to 20%, 50% and 75%, finally achieving full power on June 15.
However, on June 28, problems arose in the steam shutoff valve in the reactor isolation cooling system and in the turbine trip function. Reduced function of the steam shutoff valve was caused by a tiny amount of crud, which wore away the surface of the valve seat, causing an imperfect seal. The problem with the turbine trip function was due to a loss of control from the control room. TEPCO assessed that neither of these problems was caused by the earthquake. It completed measures in response to these incidents on July 4.
From around June 3, there was a rise in discharge pressure from a pump in the residual heat removal system. This was also caused by a leak from a valve seat. Measures in response to this problem were completed on July 5. Again, TEPCO assessed that the problem was not caused by the earthquake.
Even if TEPCO claims that the above problems were not caused by the earthquake, the key issue is whether or not valves and other equipment will work properly if there is another earthquake. The subcommittee discussed this question in detail. Committee member Motoe Suzuki submitted questions in advance, so TEPCO came prepared with documentation to back up its response. However it based its explanation on data published in March 1983. That data came from a research project carried out jointly by electric power companies. It shows the results of tests including vibration tests, function tests and pressure tests, but committee members pointed out that the conditions were too far removed from reality and questioned whether this very dated experiment is still valid after the Chuetsu-oki Earthquake. It was decided that TEPCO should provide more answers.
As can be seen from the above account, deliberations concerning KK-1 have not yet finished. At its July 21 meeting, Niigata Prefecture’s technical committee requested TEPCO to provide more information. However, it chose to give its blessing for commercial operations without waiting for TEPCO’s responses. Now only the approvals of the Nuclear Safety Commission, the governor of Niigata and the mayors of Kashiwazaki City and Kariwa Village remain.
There has been intense debate about Unit 5 in the subcommittee.
The steering committee submitted a draft report on the debate within the subcommittee, but committee member Kotaro Kuroda stated that it was unacceptable. He presented a submission of his own in which he expressed his opposition to the draft.
Kuroda stated that the steering committee’s report effectively regurgitates TEPCO’s account, which concludes that there are no problems, and that it does not accurately reflect the debate within the subcommittee. He also pointed out that Niigata Prefecture’s technical committee has at no stage held deliberations of its own about TEPCO’s account, that it is unlikely to read the record of the subcommittee’s discussions before it debates the matter, and that each member of the subcommittee should, therefore, submit his own opinions to the technical committee as material for the technical committee’s deliberations.
The Chair of the subcommittee, Masaharu Kitamura, expressed his opposition to Kuroda’s suggestion, saying that it was very regrettable, but Masahiro Koiwa and Motoe Suzuki expressed their support. The other three members did not express an opinion, so only two completely conflicting views were presented. Kuroda demonstrated that he was serious by stating that he would have to consider whether he was able to continue as a member of a committee that operates in this manner. Thus, there is total confusion about when Niigata Prefecture’s technical committee will convene to consider Unit 5.
TEPCO’s responses to the five questions submitted by groups representing residents of Niigata Prefecture were very vague. There were some comments from committee members, but all in all the debate was totally inadequate. The discussion will continue and TEPCO has been requested to respond in writing.
Although important safety questions remain answered, the approval process for the resumption of commercial operations at KK-1 has been steamrolled. Meanwhile, the situation regarding KK-5 is still totally unclear.
By Yukio Yamaguchi (CNIC Co-Director)