The Niigata-Chuetsu-Oki earthquake occurred in Niigata Prefecture on July
16 at 10:13 a.m. led to automatic scram of units 2, 3, 4 and 7 of
Kashiwazaki-Kariwa Nuclear Power Station. Since the occurrence of the
earthquake, we have examined both indoor and outdoor facilities of all
seven units including units 1, 5 and 6, which were offline for periodic
outage at the time of the earthquake. The findings from the examination
as of today are as follows:
- Four units--K-2, K-3, K-4, and K-7--that scrammed automatically on July
16 are currently in a stable cold shutdown condition.
- Two incidents regarding the leak of radioactive materials were identified:
(1) Water leakage containing radioactive materials into the Japan Sea (K-6.)
The amount of radioactivity released to the sea is about 9 x 104 Bq
(equivalent to an exposure of about 2 x 10-9 mSv.) It is presumed that
water spilled over from the spent fuel pool to the reactor building
refueling floor (controlled area) subsequently dripped down to the
uncontrolled area via cable and conduit of the refueling machine. Detailed
investigation on the cause is underway.
(2) Detection of iodine and particulate radioactive materials at the monitor
of main exhaust stack (K-7.)
The amount of radioactivity released from the stack to date is about
4 x 108 Bq (equivalent to an exposure of about 2 x 10-7 mSv.).
Note: Regulatory limit of annual exposure for an ordinary person is 1 mSv.
Ordinary people are exposed to natural radiation of 2.4 mSv per annum.
- We have completed visual examination of both indoor and outdoor facilities
and identified issues as shown in the attached sheet.
We will put together inspection plan for important facilities including
reactor internals and execute in-depth inspection based on the plan. We will
also adequately restore numerous damages found in facilities that are not
related to nuclear safety.
Appendix:Plant Status of Kashiwazaki-Kariwa NPP after the Niigata Earthquake