Regarding the accident of Fukushima Daiichi Nuclear Power Station caused
by the Tohoku-Chihou-Taiheiyou-Oki Earthquake which occurred on March 11,
2011, we, Tokyo Electric Power Company, have been developing the immediate
roadmap to restore the situation, and have taken all measures for this
purpose at the moment.
Along with these efforts, we have been organizing the past work progress
record as well as the plant data after the earthquake.
In this task, we have decided to conduct the analysis of the reactor core
status based on the currently available records and on the hypothesis led
from such records.
 
As a result, we estimate that "regarding the Unit 1, nuclear fuel pellets
have melted, falling to the bottom of the reactor pressure vessel at a
relatively early stage after the tsunami reached the station."
 
Meanwhile, regarding the reactor core status of Unit 1, because the fuel
has been cooled stably by water injection, we believe that there would not
be likely the further situation transition, e.g. to the situation where
we need to release a large amount of radioactive materials.
 
Because the current analyses are not always able to utilize every
necessary information, which means that the analyses result are
provisional, we will make effort to have more accurate status of the
reactor core through further investigation.
 
For the Unit 2 and 3, we will also conduct the similar analyses. 

Attachment:Tokyo Electric Power Company: Reactor Core Status of Fukushima 
           Daiichi Nuclear Power Station Unit 1 (PDF 92.6KB)