4th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 59, Number 10
Tuesday–Saturday, October 7–11, 2014;
Waikoloa, Hawaii
Session AA2: Pleanary Talk II
11:00 AM–12:30 PM,
Wednesday, October 8, 2014
Room: Monarchy Ballroom
Chair: Takaharu Otsuka, University of Tokyo
Abstract ID: BAPS.2014.HAW.AA2.2
Abstract: AA2.00002 : Fukushima Daiichi Nuclear Accident; based on the Final Report of Atomic Energy Society of Japan
11:45 AM–12:30 PM
Preview Abstract
Abstract
Author:
Naoto Sekimura
(Department of Nuclear Engineering and Management, The University of Tokyo)
The Atomic Energy Society of Japan (AESJ) published the Final Report of the
AESJ Investigation Committee on Fukushima Daiichi NPS Accident in March
2014. The AESJ is responsible to identify the underlying root causes of the
accident through technical surveys and analyses, and to offer solutions for
nuclear safety.
At the Fukushima Daiichi, Units 1 to 3, which were under operation, were
automatically shut down at 14:46 on March 11, 2011 by the Tohoku
District-off the Pacific Ocean Earthquake. About 50 minutes later, the
tsunami flooded and destroyed the emergency diesel generators, the seawater
cooling pumps, the electric wiring system and the DC power for Units 1, 2
and 4, resulting in loss of all power except for an air-cooled emergency
diesel generator at Unit 6. Unit 3 lost all AC power, and later lost DC
before dawn of March 13. Cooling the reactors and monitoring the results
were heavily dependent on electricity for high-pressure water injection,
depressurizing the reactor, low pressure water injection, and following
continuous cooling. In Unit 3, for example, recent re-evaluation in August
2014 by TEPCO shows that no cooling water was injected into the reactor core
region after 8PM on March 12, leading to the fuel melting from 5:30AM on
March 13. Even though seawater was injected from fire engines afterwards,
the rupture of pressure vessel was caused and the majority of melted fuel
dropped into the containment vessel of Unit 3. The estimation of amount of
radioactive materials such as Xe-133, I-131, Cs-137 and Cs-134, emitted to
the environment from Units 1 to 3 is discussed in the presentation.
Direct causes of the accident identified in the AESJ Report were, 1)
inadequate tsunami measures, 2) inadequate severe accident management
measures and 3) inadequate emergency response, post-accident
management/mitigation, and recovery measures. These were caused by the
following underlying factors, i.e., a) lack of awareness on the roles and
responsibilities by experts, b) shortfalls in establishing safety measures
and fostering safety awareness by utilities, c) lack of safety awareness by
the regulatory body, d) inadequacies in attitude of learning from efforts
and collaborations in the international community, and e) shortage of
qualified personnel to ensure safety and inadequacies in organization and
management framework.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.HAW.AA2.2