It is now almost 22 months since the Kashiwazaki-Kariwa nuclear power plant was struck by the Chuetsu-oki Earthquake. The Japanese government and Tokyo Electric Power Company want to restart Unit 7. But currently, debate over three serious problems has not been resolved, one of them being the irregular movement of reactor and turbine buildings. Will science be sacrificed for the sake of national policy?
Of the seven reactors at the Kashiwazaki-Kariwa Nuclear Power Plant (KK), all of which have been shut down since the Chuetsu-Oki Earthquake in July 2007, Unit 7 (ABWR, 1356 MW) is said to have suffered least damage. On February 18 the Nuclear Safety Commission (located within the Cabinet Office) approved the restart of this reactor. The following day Tokyo Electric Power Company (TEPCO) applied to Kashiwazaki City, Kariwa Village and Niigata Prefecture for permission to restart the reactor. It appeared that it wanted all the necessary approvals in place by March 31, the end of the fiscal year.
However, things are not going as TEPCO planned. A fire in Unit 1 on March 5 increased the concerns of the local residents. This is the eighth fire since TEPCO began work in preparation for restart. The cause on this occasion was that workers had not received training about the danger of inflammable vapor in the area. Residents are very critical of TEPCO. They say that TEPCO's claim that it places top priority on safety is an empty slogan and that it is not qualified to operate nuclear reactors. On March 11 Niigata Governor, Hirohiko Izumida, said that he would not give his approval for restart of KK Unit 7 until the appropriateness of TEPCO's plan to revise its fire prevention system is accepted. He indicated that he did not think public understanding for restart had been obtained. Kashiwazaki Mayor, Hiroshi Aida, and Kariwa Mayor, Hiroo Shinada expressed similar sentiments.
2. Jumping the gun
On March 8 Niigata Prefecture's technical committee on safety control of nuclear power plants held its third meeting since the Chuetsu Oki Earthquake. It agreed that a chairman's opinion supporting restart should be presented at the next meeting, scheduled for March 18. However, the March 8 meeting was sadly lacking in scientific and technical debate and failed to answer scientifically based questions raised by committee members opposed to restarting KK-7. The reason for the unscientific nature of the discussion was that it was based on a sloppy summary of issues debated in two technical subcommittees, when the deliberations of these subcommittees have not even been concluded.
3. Unresolved problems
At this stage, debate over three serious problems has not been resolved.
(1) KK's seismic safety
TEPCO, the Nuclear and Industrial Safety Agency (NISA) and the Nuclear Safety Commission (NSC) argue that it is sufficient to set the magnitude of the design-basis earthquake at M7.0. NISA and NSC approved restart of Unit 7 on this basis. (By comparison, the Chuetsu-Oki Earthquake was M6.8 on the Japanese scale.) However, some scientists have said that this is inadequate. They believe a M7.5 earthquake should be chosen. Although they have provided clear scientific evidence, their arguments have been ignored.
The issue relates to questions about the seismic fault plane that caused the Chuetsu-Oki Earthquake and the form of the marine terrace running from Kashiwazaki to Niigata. The critics claim that the F-B fault was not the source of the Chuetsu-Oki Earthquake. They say the source was the much longer Eastern Boundary Fault of Sado Basin. Historically, this fault has moved repeatedly and it has had a fundamental influence on the form of the marine terrace in the region. There is no scientific basis for refuting this argument.
The basic earthquake ground motion was set at 2,300 Gal for Units 1~4 and 1,209 Gal for Units 5~7 on the basis of a M7.0 earthquake, but these levels are clearly inadequate.
(2) Irregular movement of reactor and turbine buildings
The ground level has been measured on three occasions since the earthquake, but each time the direction and size of the inclination of the buildings was different. This shows that the plant was not built on firm ground. The fact is that the ground beneath the buildings is moving [see box].
Building on tofu?
An issue relevant to the work of both sub-committees is how to interpret the fact that the reactor and turbine buildings have continued to move since the earthquake. TEPCO has measured the elevation of the buildings on three occasions since the earthquake - immediately after the earthquake, in February 2008 and again in August 2008. There are suspicions that the continued movement could be because the bedrock has broken up, or for some other similar cause. Alternatively, it could be related to the Madogasaka Fault, which NSC claims is not active.
During the December 23 meeting in Kariwa Village hosted by the Niigata Prefecture sub-committees, the chair of the subcommittee into equipment integrity and earthquake resistance and safety, Haruo Yamazaki, responded to a question with an example of a nuclear power plant floating on a cup of starch. When construction of the Kashiwazaki-Kariwa Nuclear Power Plant was first planned, people said it was like building a nuclear power plant on tofu. Now it looks like the ground on which the plant is built is no more solid than a cup of starch.
Nuke Info Tokyo 128, Jan/Febr. 2009
The seismic safety guidelines in force when the plant was constructed (the old guidelines) required that nuclear power plants be constructed on firm ground. The construction of KK violated these guidelines. The excuse is given that the inclination is within the permitted limits and will not interfere with insertion of the control rods, but this avoids the real issue. Can the plant withstand the next earthquake? Why does the ground continue to move in this irregular way? As long as scientific answers to these questions are not found, residents will not have confidence in the safety of the plant.
At the beginning of March a research team from Niigata University carried out a second boring near the plant. Results have just come in and there is a difference of 20 meters between the Niigata University team's measurement and TEPCO's measurement of the Nishiyama stratum. This suggests fault activity contrary to the analysis of the ground structure around the KK plant carried out by TEPCO and accepted by the government. My view is that this is because KK is indeed "a nuclear power plant floating on a cup of starch".
(3) Can the casing of the reactor coolant recirculation pump motor survive the next earthquake?
KK-6&7 are Advanced Boiling Water Reactors (ABWR). This type of reactor has internal recirculation pumps. ABWR reactors have 10 recirculation pumps, which are welded onto the bottom of the wall of the reactor vessel. There are concerns that during an earthquake in excess of M7 the casing within which the recirculation pump motors are contained could buckle and break.
The stress applied by a M7 earthquake is calculated to be 195 megapascals. By comparison, the design standard is 207 megapascals. That means there is a leeway of just 6%, suggesting that the casing would not withstand a M7.5 earthquake. There is a danger that it could break off. In such a case, the reactor coolant would drain out leading to a major accident.
Considering the abovementioned unresolved issues, TEPCO should not be allowed to restart KK Unit 7. To restart the reactor would be a huge gamble. It would fly in the face of the safety-first principle.
4. Radioactive pine needles
Measurements commissioned by CNIC of radioactive carbon-14 in the needles of pine trees growing by the Kashiwazaki-Kariwa Nuclear Power Plant raise questions about how much radioactivity was actually released during the Chuetsu-Oki Earthquake. Pine needles which grew in 2007, the year of the Chuetsu-Oki Earthquake, on trees in TEPCO's public relations center had elevated specific activity of carbon 14 (294.8 mBq/gC from 2007 pine needles compared to 251.2 mBq/gC for 2008 pine needles). This suggests that more radioactivity was released during the earthquake than TEPCO claimed. It is unclear where the carbon 14 came from, but it is conceivable that it could have leaked from damaged fuel assemblies. This is further evidence that the full effects of the earthquake are still not properly understood.
TEPCO failed to carry out measurements of environmental samples to assess radioactivity released during the earthquake. As it happened, CNIC already had a project to measure radioactivity around Rokkasho, so we decided to measure carbon 14 in pine needles from KK at the same time.
April: Another fire; more delays
Meanwhile, on April 17, the central government and the mayors of Kashiwazaki City and Kariwa Town had given their approval for the restart of KK Unit 7. Only the approval of the governor of Niigata Prefecture remains.
Governor Izumida said recently that he wanted an explanation to be provided to the Prefectural Assembly before making his final decision. It was expected that the explanation would be provided on April 21, but the date was postponed after yet another fire at the plant. The fire, which arose in a storehouse on April 11, was the ninth fire at the plant since the earthquake. Tokyo Electric Power Company's inability to develop an effective fire control system has severely damaged its credibility in safety management.
Nevertheless, there is tremendous pressure on the governor to approve restart of reactor 7. The local movement against restart of the plant is fighting valiantly, but it will be difficult to prevent restart of the reactor for much longer. There are no immediate signs that any of the other reactors will be restarted soon.
Under these circumstances, people might be interested in material to help them refute the propaganda that is likely to accompany the restart of Unit 7. CNIC recently added to its website a report on the history of the seismic design of KK. This report shows how politics has always been prioritized over seismic safety in the design and operation of KK. We hope the report will be useful for people trying to stop nuclear power plants in other earthquake prone regions.
The April 6, 2009 report “Seismic Design of the Kashiwazaki-Kariwa Nuclear Power Plant: a Historical Perspective”, by Philip White and Yukio Yamaguchi can be found at: http://cnic.jp/english/topics/safety/earthquake/kkdesignhistory6ap09.html
Source: Nuke Info Tokyo 129, March/April 2009 & update CNIC, 17 April 2009
Contact: Philip White at Citizens' Nuclear Information Center (CNIC). Akebonobashi Co-op 2F-B, 8-5 Sumiyoshi-cho, Shinjuku-ku, Tokyo, 162-0065, Japan
Tel: + 81-3-3357-3800
Latest: Restart KK-7 May 8?
As stated in the article, there is “tremendous pressure on the governor to approve restart” of Kashiwazaki-Kariwa reactor 7, and it is “difficult to prevent restart (…) for much longer”. And indeed, on May 6, Reuters reports that the restart is imminent and the reactor may begin a trial-run as soon as May 8, expecting the approval of the governor on May 7.
Reuters, 6 May 2009