There were some misleading comments in the IAEA's August 17 report on the Kashiwazaki-Kariwa nuclear power plant (KK), as well as some sensible comments that the pro-nuclear lobby will try to ignore. Below is a response to some of the issues raised in the report.
1. "Expected" Damage
In its August 17 press release the IAEA states, "Earthquake damage to the Kashiwazaki-Kariwa nuclear power station on 16 July appears to be limited and less than expected."
Response: A similar comment made a few days earlier by the head of the "IAEA expert mission" has been quoted widely in the media. However it is a meaningless statement. It depends on what he expected. The comment is being used to diminish the seriousness of the problems.
2. Visible and Invisible Damage
The August 17 report states, "Safety related structures, systems and components of the plant seem to be in a general condition, much better than might be expected for such a strong earthquake, and there is no visible significant damage..."
Response 1: The key issue is the invisible damage. It is to be expected that the plant has been significantly weakened. Even if a visual inspection does not reveal any serious problems, the stresses and strains that the earthquake placed on equipment, pipes, etc. is likely to have caused invisible damage and general weakening. Practically speaking, it is impossible to confirm the extent of this damage and weakening.
The IAEA report acknowledges this issue as follows:
"Another consideration is the possibility that the long-term operation of components could be affected by hidden damage from the earthquake. Thus, the potential interaction between large seismic events and accelerated ageing may be an important topic to consider in future inspection programmes."
Response 2: The insides of the reactors have not been seen yet, so it is premature to pass judgment on the condition of the plant.
The IAEA report acknowledges this issue as follows:
"However, important components like the reactor vessels, the core internals and the fuel elements have not yet been examined and in-depth inspections are still to be performed."
3. Seismic risk
(i) Even if the plant withstood this earthquake, there is no guarantee that the plant, which has been weakened by the July 16 earthquake, will withstand the next earthquake. Furthermore, the next earthquake could be even bigger.
(ii) It now seems that the Kashiwazaki-Kariwa nuclear power plant is located directly above a seismic fault.
The IAEA August 17 press release acknowledges these issues as follows:
"In the IAEA report it is suggested that a re-evaluation of the seismic safety the Kashiwazaki-Kariwa NPP needs to be done taking into account the lessons learned from the Niigataken Chuetsu-Oki earthquake, using updated criteria and methods. In particular, detailed geophysical investigations are foreseen both on land and offshore in order to define the new seismic input to the plants. These investigations, it is stated in the report, should address the issue of the potential existence of active faults underneath the site."
4. Length of Shutdown
The media quoted the head of the "IAEA expert mission", Pilippe Jamet as saying that it would take "months or a year" to put the plant back into operation.
Response: Points 2 and 3 above are convincing reasons why the plant should never be operated again. There are no grounds for suggesting the plant can be restarted in a year's time. Nor are there any grounds for using the earthquake that hit the KK as evidence that nuclear power plants can withstand strong earthquakes.
