Lessons learned from the process focusing on achieving the state of cold shutdown of Fukushima Daiichi Nuclear Power Plant Accident

Yoshizawa, Atsufumi*; Oba, Kyoko; Kitamura, Masaharu*

Ningen Kogaku, 54(3), p.124 - 134, 2018/06

Fukushima Daiichi Nuclear Power Plant caused a severe accident which released a large amount of radioactivity triggered by the Great East Japan Earthquake. The existing investigation reports of the accident prepared by several institutions pay attention only to the process which caused the accident but not much to the accident mitigation or the recovery process. This study focused on Unit 3 of Fukushima Daiichi Nuclear Power Plant, including its recovery process from the accident. Based on the public data, the time sequences for the recovery process between the accident occurrence and the state of cold shutdown were classified. Then, the groups of actions were sorted out in terms of ergonomics viewpoint. The important responses in the recovery process were identified and analyzed referring to the m-SHEL model. As a result, new lessons were learned from the accident case regarding the actions required for recovering from the accident.

Report of Examination of the Sample from Core Shrouds (K3-H7a) at Kashiwazaki-Kariwa Nuclear Power Station Unit-3 (Contract research)

The Working Team for Examination of the Sample from Core Shrouds and Primary Loop Recirculation Pipi

JAERI-Tech 2004-002, 58 Pages, 2004/02

JAERI-Tech-2004-002.pdf:15.44MB

no abstracts in English

A Plant data evaluation for Fukushima-Daiichi NPP Unit 3

Sato, Ikken

no journal, , 

The PCV pressure measurement of Fukushima-Daiichi NPP Unit 3 showed cyclic pressure up and down. Although some early pressure changes of them can be regarded as consequence of venting actions, later changes are not likely due to venting nor significant leakage through the PCV boundary. In this study, preliminary correction for pressure measurement data was applied based on assumed consistency among different pressure measurement data. With this correction, subtle pressure differences among RPV, D/W and S/C became visible and information related to accident progression was obtained. With this knowledge, possible mechanism of PCV pressure decrease by itself will be reported.

Inverse analysis of steam and hydrogen generation history of Fukushima Daiichi Nuclear Power

Yoshikawa, Shinji; Sato, Ikken

no journal, , 

Steam and hydrogen generation history and leakage scale from RPV of Fukushima Daiichi Nuclear Power Plant unit 3 to reproduce the measured pressure history of RPV and PCV were inversely analyzed using a thermal hydraulic code GOTHIC. The leakage area from RPV to reproduce the measured decrease behavior of RPV pressure is evaluated to be around 1 cm, regardless of the assumed leakage paths. Since some of SRVs are supposed to have been open at the time of the major slumping (~12:00 of March 13), provided that the leakage area was kept ~1cm, its effect on PCV pressure would have been negligible. In this case, the gas flow at the time of the main slumping would have been through S/C, where vapor condensation was effective, thus certain contribution of non-condensable gases like hydrogen seems necessary to explain the observed D/W and S/C pressure increase.