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.
                                    (Previously announced on May 18, 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 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. 


Attachment 1: Fukushima Daiichi Nuclear Power Station Unit No. 2 report on 
              earthquake response analysis of the reactor building, 
              important equipment and piping system for earthquake-resistant 
              safety using observed seismic data during the Tohoku-Taiheiyou 
              -Oki Earthquake in the year 2011 (Summary)(PDF 121KB) 
Attachment 2: Fukushima Daiichi Nuclear Power Station Unit No. 4 Report on 
              earthquake response analysis of the reactor building, 
              important equipment and piping system for earthquake-resistant  
              safety using observed seismic data during the Tohoku-Taiheiyou 
              -Oki Earthquake in the year 2011 (Summary)(PDF 111KB) 
Attachment 3: Report regarding survey and result of modification of the 
              malfunctions of seismometers (Recording device) confirmed 
              during the Tohoku-Taiheiyou-Oki Earthquake occurred on 
              2011 (Digest)(PDF 9.36KB) 



* 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