TEPCO compiled and reported to NISA 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. 
                      (Previously announced on April 1 and May 16, 2011)

Subsequently, we received an instruction document* from NISA. Following 
the instructions, we were meant to conduct a detailed evaluation of the 
impact from the earthquake, implement countermeasures for seismometer 
malfunctions, and report the results to NISA. By August 17th, 2011, we 
had already compiled the following results of the earthquake response 
analysis at Fukushima Daiichi and Daini Nuclear Power Station and 
submitted them to NISA. 

·Results of the earthquake response analysis of the reactor building, 
 facilities and pipes important to earthquake safety at Units 1 to 6 at 
 Fukushima Daiichi Nuclear Power Station 
·Results of the earthquake response analysis of the reactor building, 
 facilities and pipes important to earthquake safety at Units 1 to 4 at 
 Fukushima Daini Nuclear Power Station 
·Results of the earthquake response analysis of all turbine buildings, 
 facilities and pipes important to earthquake safety at Fukushima Daiichi 
 and Daini Nuclear Power Station
           (Previously announced on June 17, July 28 and August 18, 2011)

Later, we discovered an error in the evaluation results of the main steam 
system piping arrangement of Unit 2 at Fukushima Daini Nuclear Power 
Station in the reports, and concluded that the error needed to be corrected. 
We also reported it to NISA. 
We have confirmed that the calculated value is lower than the evaluation 
standard value even in the results after making the correction and no other 
identical error exists at our other plants. 

                                                                       END

○ Attachment  
Partial correction of the report on results of earthquake response analysis  
of Unit 2 at Fukushima Daini Nuclear Power Station using observed seismic  
data during the Tohoku-Taiheiyou-Oki Earthquake (PDF 67.4KB)  
 
* 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!Ct 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