KK-1 Moves Closer to Restart
On May 11 Niigata Prefecture's technical committee on safety control of nuclear power plants endorsed the restart of the Kashiwazaki-Kariwa (KK) Unit 1 (BWR, 1100MW). KK-1 was shaken most (680 Gal*) and incurred the most damage (695 cases) of all the seven KK units during the Chuetsu-oki Earthquake in July 2007. It is also the oldest unit, having operated for 22 years at the time of the earthquake. However, before it can be restarted, a meeting must be held to explain the situation to the Niigata public. Also, the governor of Niigata Prefecture and the mayors of Kashiwazaki City and Kariwa Village must give their approval.
The central government's Nuclear Safety Commission gave its blessing on April 15, saying that in regard to equipment integrity and earthquake resistance there were no safety problems. However, at the time, serious issues were still being debated by a subcommittee of Niigata Prefecture's technical committee. The subcommittee was established after the earthquake to consider equipment integrity and earthquake resistance and safety.
The two main points of contention were as follows. First, some subcommittee members pointed out that, if there was a large earthquake, important machinery and equipment could incur strain in excess of their design basis. Tokyo Electric Power Company (TEPCO) only provided partial data in response to this concern. The other issue related to the safety margin in the event of another large earthquake. Would the control rods, which control the reactivity of the core, be inserted within the specified time? TEPCO only gave vague responses to this question.
These issues still had not been resolved when a 60 cm-long penetrating crack was found in a reinforced concrete wall in Unit 5. Naturally, local residents asked whether there were not similar cracks in Unit 1. Three more penetrating cracks were found in Unit 5 on April 27, one of which penetrated a wall that was 90 cm thick.
However, with opinions still divided and questions unresolved, the subcommittee submitted a summary of the issues discussed to the technical committee. Meanwhile, the central government was pressuring Niigata Prefecture's nuclear safety office to quickly convene a meeting of the technical committee, for which it provides the secretariat.
At the same time, the nuclear safety office was receiving lots of questions from local residents and people throughout the prefecture. In the brief period from April 30 to May 9, 82 questions were submitted. In the midst of all this came the revelation of over 500 inspection oversights at Chugoku Electric's Shimane Nuclear Power Station (see page 5 of this issue of NIT). The questions submitted to Niigata Prefecture's nuclear safety office suggest that citizens have suspicions of similar oversights by TEPCO. The questions submitted can be classified under the following 13 categories:
1. Cracks in the steel reinforced concrete walls (16 questions)
2. The concrete strength used in the safety assessment (9 questions)
3. Seismic reinforcement work (7 questions)
4. Insertion of control rods (6 questions)
5. Plastic deformation (1 question)
6. Equipment integrity (7 questions)
7. Ground condition (8 questions)
8. Tsunamis (1 question)
9. Inspection oversights at Shimane (2 questions)
10. The overall assessment (2 questions)
11. Niigata Prefecture's technical committee (8 questions)
12 Concerning questions from the public (2 questions)
13. Other (13 questions)
The questions were all very reasonable. Most of them were critical of the attitude of the Prefecture and its technical committee.
At the technical committee's May 11 meeting, Niigata University Professor Kenji Suzuki was elected to replace the outgoing chair. Reports were received from both subcommittees, one looking into "equipment integrity and earthquake resistance and safety" and the other looking into "the Chuetsu-oki Earthquake and ground condition". Some supplementary explanation was also given. An engineer specializing in seismic resistance gave a one-sided presentation on why the penetrating cracks have no particular impact on safety. Members of the general public in the audience seemed to be skeptical. The committee concluded that there were no problems regarding insertion of control rods and, with virtually no substantive questions from the committee members, start-up testing of KK Unit 1 was endorsed.
The people in the audience were very disappointed. They wondered what was the point of having such a technical committee. In particular, those who had followed the earnest deliberations in the subcommittees had a feeling of futility.
The next steps of the prefecture and its nuclear safety office are under question. Are they capable of holding a public hearing with any substance? There is no clear basis for a judgment by the governor.
Yukio Yamaguchi (CNIC Co-Director)
*1 Gal = 0.01 m/s2.
Return to NIT 136 contents