Seismic motion that exceeds the design-basis level was observed at the
Kashiwazaki-Kariwa Nuclear Power Station during the Niigata-Chuetsu-oki
Earthquake in 2007. Accordingly, separately from the seismic safety
assessment, our company has decided to conduct a study on potential
impact on safety-significant equipment representing functions of
"shut-down", "cooling" and "containment", by comparing the observed
seismic data of the above earthquake on the foundation mat of the reactor
building of the Kashiwazaki-Kariwa Nuclear Power Station with the data of
design-basis seismic motions of the Fukushima-Daiichi Nuclear Power Station
and the Fukushima-Daini Nuclear Power Station.
As we have completed a summary report on a general study made in light
of the Niigata-Chuetsu-oki Earthquake in 2007, we are now pleased to
inform you about it. On the basis of the results of the above study,
we consider that safety functions can be maintained with safety-significant
equipment representing "shut-down", "cooling" and "containment" at the
Fukushima-Daiichi and Fukushima-Daini Nuclear Power Stations.
The study results(not attached here) were reported to the Ministry of
Economy, Trade and Industry today.
Our company will implement seismic safety assessment at the Fukushima-Daiichi
Nuclear Power Station and the Fukushima-Daini Nuclear Power Station according
to the seismic safety assessment implementation plan* which was reviewed on
Also, at the Kashiwazaki-Kariwa Nuclear Power Station, while we will continue
with geological surveys based on the subject earthquake, we will be proceeding
with assessment of seismic safety including analyses of earthquake data observed.
* Seismic safety assessment implementation plan
The above represents a summary of the seismic safety assessment plan to be
implemented in line with the earthquake resistant design review guidelines
concerning the power reactor facilities as revised in September 2006. With
respect to the procedure for assessment, a certain standard seismic ground
motion is to be established on the basis of geological and seismic survey
results, and seismic resistance assessment of the equipment and piping
systems is to be carried out from the seismic response analysis of the
equipment and buildings, etc, to the said standard seismic ground motion.
Appendix: A summary of the "Report on the results of a general study of potential
seismic impact on the main facilities of the nuclear power stations made
on the basis of the observational data at the Kashiwazaki-Kariwa Nuclear