On April 30th, 2011, we received the instruction "Submission of report 
regarding the implementation of a measure to flood primary containment 
vessel to the upper area of fuel range in Unit 1 of Fukushima Daiichi 
Nuclear Power Station" from Nuclear and Industrial Safety Agency (NISA).
Therefore, we have confirmed that flooding the primary containment vessel 
to the upper area of fuel range in Unit 1 of Fukushima Daiichi Nuclear 
Power Station will have stable cooling effect on the reactor and that 
there will be no problematic issues regarding safety. We submitted the 
report to NISA today.
                           (Already announced on April 30th, May 5th,2011)

We hereby notify that we have received the instruction*2 "Implementation 
of a measure to flood the primary containment vessel to the upper area of 
fuel range in Unit 1 of Fukushima Daiichi Nuclear Power Station" on May 
5th, 2011.

In compliance with the implementation instructions from NISA, and ensuring 
safety, we will steadily implement "A measure to flood the primary 
containment vessel to the upper area of the fuel range in Unit 1 of 
Fukushima Daiichi Nuclear Power Station".

Attachment:
Report regarding the implementation of a measure to flood the primary 
containment vessel to the upper area of fuel range in Unit 1 of Fukushima 
Daiichi Nuclear Power Station (summary)(PDF 149KB)

*1 Instruction notice regarding report
Submission of the report regarding the implementation of a measure to 
flood the primary containment vessel to the upper area of the fuel range 
in Unit 1 of Fukushima Daiichi Nuclear Power Station

                                                      NISA no.1, 2011.4.30

NISA hereby instructs TEPCO to report the following matters in a timely 
manner based on article 67, clause 1 of the Act on the Regulation of 
Nuclear Source Material, Nuclear Fuel Material and Reactors in order to 
evaluate the appropriateness of an emergency measure planned by TEPCO. 

In case TEPCO disagrees with this instruction, it is entitled to make a 
formal objection in writing to the Minister of Economy, Trade, and 
Industry based on Administrative Appeal Act (law number 160, 1962) within 
60 days from the following day when the instruction was acknowledged. 
However, it is not entitled to do so after one year from the following day 
of the instruction even if within 60 days from the following day when it 
acknowledges the instruction.

After the treatment of a formal objection is determined, action to rescind 
the disposition can be made against the government (representative: 
ministry of law) based on Administrative Case Litigation Act (law number 
139, 1962) within 6 months from the next day when it recognizes the 
determination of treatment of a formal objection. However, it is not 
entitled to do so after one year from the next day of the determination 
even if within 6 months from the following day when it acknowledges the 
determination.

In case of the followings, TEPCO is entitled to take action to rescind the 
disposition without the determination of a treatment of a formal objection. 
1: treatment is not determined within 3-months from the following day when 
a formal objection is made. 2.there is an urgent need to avoid significant 
damage caused by disposal, execution of disposal and continuation of 
execution. 3.there are justifiable grounds for not having the 
determination of treatment. 

Submission of report regarding the effect to stable reactor cooling and 
the safety of a measure to flood the primary containment vessel to the 
upper area of the fuel range in Unit 1 of Fukushima Daiichi Nuclear Power 
Station.

1.impact on the structural strength and earthquake resistance qualities of 
  the reactor building and primary containment vessel from the water level 
  increase in the primary containment vessel
  * Result of the impact analysis on the structural strength of the 
  structure and facilities in the primary containment vessel including the 
  reactor building, dry well, and suppression chamber from the water level 
  increase in the primary containment vessel
  * Result of evaluation regarding whether the reactor building and 
  structure and facilities in the primary containment vessel can sustain 
  the designed seismic force. 
2.Impact from the pressure increase inside the primary containment vessel.
  * Estimation of the pressure increase inside the primary containment 
  vessel from the water level increase
  * Result of the analysis on the necessity of a countermeasure to reduce 
  the pressure inside the primary containment vessel in consideration of 
  the above estimation. 
3.impact from the increase of leaking water in the turbine building
  * Estimation of the amount of leaking water at present and in the future 
  and the possibility of leakage to the outside environment. 
4.Other issues relating to the safety evaluation regarding the 
  implementation of a measure to flood the primary containment vessel to 
  the upper area of the fuel range.

*2 Instruction notice regarding implementation
Implementation of a measure to flood the primary containment vessel to the 
upper area of fuel range in Unit 1 of Fukushima Daiichi Nuclear Power 
Station

                                                       NISA no.1, 2011.5.5

On April 30th, 2011, we instructed TEPCO to report the implementation of a 
measure to flood the primary containment vessel to the upper area of the 
fuel range in Unit 1 of Fukushima Daiichi Nuclear Power Station based on 
article 67, clause 1 of Act on the Regulation of Nuclear Source Material, 
Nuclear Fuel Material and Reactors.

Today, we have received a report and examined its contents. As a result, 
NISA has evaluated the measures as appropriate since there was no other 
effective option under such a dangerous circumstance. When implementing, 
we would like TEPCO to follow the instructions below with absolute 
accuracy to secure sufficient degree of safety.

1.Implement sufficient monitoring for the water level inside and leaking 
  water from the primary containment vessel. In addition, in an 
  appropriate manner, implement the countermeasures previously planned 
  such as controlling the amount of water being injected. 

2.Examine the seismic reinforcements to the already strained supporting 
  posts of the suppression chamber with improvements to the working 
  environment, since the continued occurrence of aftershocks is to be 
  expected.