November 2011 – INPO – Special Report on Fukushima Daiichi Nuclear Accident

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Special Report on the Nuclear Accident at the Fukushima Daiichi Nuclear Power Station

November 2011


This report provides a narrative overview and timeline for the earthquake, tsunami, and subsequent nuclear accident at Tokyo Electric Power Company’s (TEPCO) Fukushima Daiichi Nuclear Power Station on March 11, 2011. The purpose of this report is to provide an accurate, consolidated source of information regarding the sequence of events that occurred in the first days of the accident.

The information contained in this report may be used for determining future U.S. and international industry corrective actions.

Although INPO describes certain events and actions taken, those descriptions are not intended to reflect any analysis or assessment of the decisions made by any individual or entity. This report does not assess or analyze the effectiveness of plant workers or others involved in response to the event.

This report reflects the best available information, most of which was obtained from direct and ongoing interaction with TEPCO. It focuses on the first days of the event for units 1, 2, and 3 and includes some information on units 4, 5, and 6 as well as the spent fuel pools. Because of the extensive damage at the site, some details of the event remain unknown or have not been confirmed. All times are provided as Japan Standard Time (JST).

This report includes the following sections:

Executive Summary – high-level description of event milestones
Overview of Event – short description of key event factors
Event Progression – unit-specific narrative of event progression
Radiological Effects – radiological information, including radiological releases
Additional Information – station design information, drawings, and supporting data

This report was created from information provided by TEPCO, the Japanese government, the International Atomic Energy Agency (IAEA), and several Japanese nuclear and safety organizations. Some of the data included logs from the TEPCO Emergency Response Center, unit-specific parameter values and chart recorder indications, and personal accounts of the accident and plant conditions.

In some cases, specific questions were addressed through INPO employees working in the INPO Emergency Response Center in Atlanta or in the TEPCO offices in Tokyo. Specific sources used to gather information are provided in the reference section of this report.

TEPCO personnel have reviewed the content of this report for accuracy, based on their current understanding of the event. Furthermore, TEPCO assisted in developing the unit-specific timelines, provided in Section 8.0, as well as the design basis information in sections 7.1 and 7.2.

TEPCO openly shared information with INPO, responded to questions in a timely manner, and provided resources when available to support the generation of this report.

The utility is working to share the facts of this event with the industry and with the Japanese public. Without TEPCO’s assistance, this report would not have been possible.

This report is based on information available to INPO as of November 1, 2011. INPO has verified as much information as possible, but it makes no warranties as to the accuracy or reliability of the information. The information in this report has not been verified through independent or on-site observations.

The values provided, such as reactor parameters and seismic intensity, are preliminary and may be revised as more information becomes available. The effects containment conditions may have had on these indications have not been validated. Numerical values that include tenths of a unit are not intended to imply accuracy or precision, but rather are a result of the conversion from metric to U.S. units.

This report has been designated as “open distribution” and is available to the general public. The information contained herein was provided to INPO without the expectation of confidentiality, and the report does not contain INPO proprietary information. INPO members and participants may reproduce this document for business use. This report is copyrighted, and written permission is needed for organizations other than INPO members and participants to reproduce the information.

Copies of this report have been provided to TEPCO, the World Association of Nuclear Operators (WANO), and the United States Nuclear Regulatory Commission.

ML11347A454 – Special Report on the Nuclear Accident at the Fukushima Daiichi Nuclear Power Station INPO

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