We, Tokyo Electric Power Company, received an instruction document*1 from
the Nuclear and Industrial Safety Agency (NISA) of the Ministry of Economy,
Trade and Industry (NISA) on April 28. As a consequence of the occurrence
of Tohoku-Chihou-Taiheiyou-Oki Earthquake, after which a huge crustal
movement was observed, we have reviewed and summarized the Information
regarding fault, which is necessary to take into consideration in the
seismic design, which is necessary to review the possibility of eligibility
to take into consideration in the seismic design of nuclear power station,
for existing nuclear power station with existing survey and submitted to
NISA on May 31, 2011.
(Previously announced on April 29 and May 31, 2011)
On June 6, 2011, we received an additional instruction document*2 regarding
the above matter (Previously announced on June 6, 2011). Therefore, we
conducted investigations on the amount of crustal movements and occurrence
of earthquakes at the faults which we had evaluated that they need not to
be considered for the seismic design. At the same time, we conducted ground
reconnaissance and summarized a report regarding the faults of which we
cannot deny the possibility that they fall into the faults which need to be
considered for the seismic design and analyzed the influence upon the
standard ground motion. Today we reported the results of our analysis to
NISA.
(Previously announced on August 30)
Through the survey in relation to the report, we confirmed that a normal
type of earthquake fault appeared along Yunotake Fault which had not been
considered as an active fault in our seismic design. In order to survey the
past activities of Yunotake Fault and study the causes and mechanism by
which an earthquake fault appeared, we will start boring and trenching
survey from September 29.
END
Attachment:Overview of fault survey on Yunotake Fault(PDF 545KB)
*1 Instruction document
"Regarding the additional opinion of NISA for the analysis of reporting the
results of evaluation of earthquake-proof safety of existing reactor
facilities for power generation, referring to the new earthquake-proof
standards established based on the Tohoku-Chihou- Taiheiyo-Oki Earthquake,
2011 (Instruction)"
(April 28, 2011 NISA No.4)
*2 Additional instruction document
"Regarding the response to the addition of opinions upon considered by NISA
in relation to the report of the evaluation results on seismic safety of
existing nuclear power reactor facilities etc. in light of the new Seismic
Regulatory Guide based on the 2011 Tohoku District-Off the Pacific Ocean
Earthquake (additional instruction)"
(June 3, 2011 NISA No.1)
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We have provided a Japanese press release version of the instruction
document received from NISA. However, at this time we have reserved the
right to not provide an English version due to potential misunderstandings
that may arise from an inaccurate rendering of the original Japanese text.
We may provide the English translation that NISA releases in our press
releases. However, in principle we would advise you to visit the NISA
website for timely and accurate information.