We, Tokyo Electric Power Company, recognize ourselves as the main party involved in the nuclear accident triggered by the Tohoku-Chihou-Taiheiyo-Oki Earthquake on March 11, 2011. We have established the "Fukushima Nuclear Accidents Investigation Committee" and "Nuclear Safety and Quality Assurance Meeting Accident Investigation Verification Committee" comprised of external experts, and have been engaging in a thorough investigation of the accident. On December 2, 2011, an interim report including a summary of investigation/verification results and recurrence prevention measures was released. (Press release issued on December 2, 2011.)

Today, we would like to announce the release of the Accidents Investigation Report, which reports the summarized results of the investigation/ verification that have been done so far. After releasing the interim report, we have continued our efforts in learning as much as possible, especially important lessons learned, from the accident through a number of site investigations, reviewing documents and records, collecting information from parties involved in the accident, etc. Further investigation and verification were done through objective analysis by verifying the assessed results of the event progress using analyses based on the collected information. Additional topics such as support provided for the nuclear stations right after the accident, information disclosure, radiation control status and evaluation of the release of radioactive materials are covered in the report (these were not mentioned in the interim report).

This report was summarized with an eye on what is necessary for ensuring nuclear safety, and the important lessons learned will be incorporated into our future business operation. Once again, we keenly feel the responsibility for the accident and are determined to engage in business operation with safety on the top priority to prevent future recurrence. At the same time, we will continue implementing our mid to long term measures toward decommissioning of the reactors at Fukushima Daiichi Nuclear Power Station.

< Attachment >
-Fukushima Nuclear Accidents Investigation Report: Main body (Summary) (PDF 750KB)
-Fukushima Nuclear Accidents Investigation Report: Main body (Summary, Attachment) (PDF 131KB)
-Fukushima Nuclear Accidents Investigation Report: Main body (PDF 10.3MB)
-Fukushima Nuclear Accidents Investigation Report (Appendix-1) Statement of the Prime Minister's Office regarding decommissioning (PDF 158KB)
-Fukushima Nuclear Accidents Investigation Report (Appendix-2) Schedule(Time series) (PDF 1.98MB)
-Fukushima Nuclear Accidents Investigation Report (Attachment) (PDF 28.1MB)
-Major changes made on the interim report issued on December 2, 2011 (PDF 764KB)*

*English translations of the reports and the appendixes are now being developed and it takes a while to complete them.
We will post the translations one by one when it is prepared.
(The documents written in Japanese below will be replaced by English translations.)
We apologize for this inconvenience caused.