Tokyo, May 8, 2009
After months of intense pressure from Tokyo Electric Power Company (TEPCO) and the central government, the Governor of Niigata Prefecture (Hirohiko Izumida) and the Mayors of Kashiwazaki City (Hiroshi Aida) and Kariwa Village (Hiroo Shinada) today gave their permission to TEPCO to restart Unit 7 of the Kashiwazaki-Kariwa Nuclear Power Plant (KK) for the first time since the 16 July 2007 Chuetsu-oki Earthquake. In doing so, they are gambling with the safety of the people of Niigata Prefecture and beyond.
Their decision flies in the face of scientific arguments presented in two subcommittees established by Niigata Prefecture to investigate the impact of the earthquake on the plant. Neither of these subcommittees has resolved crucial questions about the nature of the earthquake, the impact of the earthquake on the plant, or the future safety of the plant. In the end, pressure from TEPCO and the central government have prevailed over sound science.
In particular, the following issues have not been resolved.
(1) 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. (By comparison, the Chuetsu-Oki Earthquake was M6.8 on the Japanese scale.) However, some scientists assert that a M7.5 earthquake should be chosen. They have provided clear scientific evidence, but their arguments have been ignored.1
(2) Unstable Ground
The ground beneath the buildings is moving. 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. In addition, boring carried out by independent scientists contradicts TEPCO's results.2 The seismic safety guidelines in force when the plant was constructed required that nuclear power plants be constructed on firm ground, but the construction of KK violated these guidelines.
(3) Seismic Safety of Equipment in Doubt
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. Even for a M7 earthquake, the casing of the recirculation pumps is near the limit of the seismic design standard.3
Important technical questions under the following three broad headings have not been answered:
- "What magnitude earthquake should the plant be designed to withstand?"
- "Why does the ground continue to move?"
- "Can the plant withstand the next earthquake?"
As long as scientific answers to these questions are not found, there can be no basis for confidence in the safety of the plant.
TEPCO, the central government and the prefectural and local governments are making the same mistakes that have been repeated throughout the history of KK. As in the past, once again they have decided to sacrifice sound science and public safety for the sake of national policy.4
Citizens' Nuclear Information Center (CNIC) demands that both of Niigata Prefecture's subcommittees be convened and that straight answers be provided to technical questions related to the abovementioned issues. It is grossly improper that permission to restart KK-7 has been given when crucial questions remain unanswered.
1. There are questions about the seismic fault plane that caused the Chuetsu-Oki Earthquake and the form of the marine terrace running from Kashiwazaki to Niigata. Some scientists 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.
2. At the beginning of March a research team, including Dr Masaaki Tateishi of Niigata University, carried out a second boring near the plant. Results show that there is a difference of 20 meters between the research 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.
3. 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. 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.
4. See the following article for a detailed discussion:
Philip White and Yukio Yamaguchi, Seismic Design of the Kashiwazaki-Kariwa Nuclear Power Plant: a Historical Perspective, Citizens' Nuclear Information Center, April 6, 2009.
Philip White (CNIC International Liaison Officer)
Yukio Yamaguchi (CNIC Co-Director)
Phone: +81-3-3357-3800 Email: firstname.lastname@example.org
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