TEPCO compiled a record of observed seismic data collected at Fukushima
Daiichi Nuclear Power Station and Fukushima Daini Nuclear Power Station
when the Tohoku-Taiheiyou-Oki Earthquake occurred at 2:46pm on March 11,
2011, and reported it to NISA.
(Previously announced on April 1 and May 16, 2011)
Subsequently, we received an instruction document* from NISA. Following the
instruction, we were meant to conduct detailed evaluation of the impact
from the earthquake shake and implementation of countermeasures for
malfunctions of seismometers, and to report the results to NISA. We have
already compiled reports on the results of earthquake response analysis of
reactor buildings, facilities and pipes important to earthquake safety in
Unit 2 and 4 and the results of survey on the malfunctions of seismometers
and their modifications made following the survey, and submitted them to
NISA.
(Previously announced on May 18 and June 17, 2011)
We'd like to notify here that we compiled reports on the results of
earthquake response analysis of reactor buildings, facilities and pipes
important to earthquake safety in Unit 1 and 3, and submitted them to NISA.
END
Attachment 1: Report on results of earthquake response analysis of reactor
building, facilities and pipes important to earthquake safety
in Unit 1 at Fukushima Daiichi Nuclear Power Station using
observed seismic data during the Tohoku-Taiheiyou-Oki
Earthquake (Summary) (PDF 88.3KB)
Attachment 2: Report on results of earthquake response analysis of reactor
building, facilities and pipes important to earthquake safety
in Unit 3 at Fukushima Daiichi Nuclear Power Station using
observed seismic data during the Tohoku-Taiheiyou-Oki
Earthquake (Summary) (PDF 96.1KB)
Attachment 3: Fukushima Daiichi Nuclear Power Station Unit No.1 Report on
Earthquake Response Analysis of the Reactor Building,
Important Equipment and Piping System for Seismic Safety
using Recorded Seismic Data of the Tohoku-Chihou-Taiheiyo-Oki
Earthquake in the Year 2011 (PDF 1.85MB)
Attachment 4: Fukushima Daiichi Nuclear Power Station Unit No.3 Report on
Earthquake Response Analysis of the Reactor Building,
Important Equipment and Piping System for Seismic Safety
using Recorded Seismic Data of the Tohoku-Chihou-Taiheiyo-Oki
Earthquake in the Year 2011 (PDF 1.77MB)
*Actions following the analysis of seismic data collected at Fukushima
Daiichi nuclear power station and Fukushima Daini nuclear power station
during the Tohoku-Taiheiyou-Oki Earthquake (Instruction)
NISA No.6, 2011 May 16
On May 16, NISA received TEPCO's report of analysis of observed seismic
data collected at Fukushima Daiichi nuclear power station and Fukushima
Daini nuclear power station during the Tohoku-Taiheiyou-Oki Earthquake.
According to the report, acceleration response spectra of observed seismic
data observed at free foundation point in the reactor buildings in
Fukushima Daiichi nuclear power station was mostly below the acceleration
response spectra for evaluation of basic earthquake ground motion Ss in
most periods, however, spectra collected in Unit 2, 3, and 5 exceeded
spectra for evaluation by 30% at maximum during 0.2 to 0.3 seconds.
Based on TEPCO's analysis above, NISA considers that it is extremely
important to evaluate the impacts from the earthquake on reactor buildings,
turbine buildings, and major facilities and pipes from earthquake
resistance perspective in Fukushima Daiichi and Daini nuclear power station
in order to confirm the status of safety function of those facilities at
the time of earthquake and following period.
The report also states that data recording was interrupted in several
voluntary located seismometers during 130 to 150 seconds after the
initiation of recoding due to the malfunction of recording devices.
The reason of malfunction was analyzed that 1) the program was coded to
finish the recording once the seismometer detects the shake below threshold
even if it detects the shake above such threshold afterwards, 2) while the
recording device was meant to restart the recording when the shake exceeds
threshold even after the recording was interrupted, program didn't restart
the recording due to the malfunction of recognition of recording material.
NISA accordingly requests TEPCO to report following matters by the
following due date.
1.Fukushima Daiichi and Diani nuclear power station
(1) Result of combining seismic response analysis of the impact from the
shake of the earthquake on reactor building and their important facilities
including PCV and RPV in Unit 2 and 4 of Fukushima Daiichi nuclear power
station.
Due date: June 17, 2011
(2) Result of combining seismic response analysis of the impact from the
shake of the earthquake on reactor building and their important facilities
including PCV and RPV in Unit 1 and 3 of Fukushima Daiichi nuclear power
station.
Due date: July 29, 2011
(3) Result of combining seismic response analysis of the impact from the
shake of the earthquake on reactor building and their important facilities
including PCV and RPV in Unit 5 and 6 of Fukushima Daiichi nuclear power
station and in all units of Fukushima Daini nuclear power station and
result of seismic response analysis of turbine buildings and major
facilities and pipes from earthquake resistance perspective in both nuclear
power station regarding the impact from the shake of the earthquake.
Due date: August 17, 2011
2.Recording device allocated to collect seismic data
Survey of the malfunction revealed in the report regarding the recording
devices of all kinds of voluntary located seismometers in TEPCO's all
nuclear power station and result of modification made following the survey.
Due date: June 17, 2011
