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The Defence in Depth Concept Applied to the New Regulatory Requirements in Japan

Abstract

Full text: The new regulatory requirements based on lessons learnt from Fukushima Daiichi accident, which places emphasis on Defense-in-Depth concept, was put into effect in Japan on 8th July, 2013. It is required to prepare multi-layered protective measures. Each layer should achieve the objective only in that layer regardless of the measures in the other layers. The challenge is how to enhance independence of measures between layers. In the third layer, the current concept of design regarding safety relies on “single failure”, whose condition is elimination of common cause failure (CCF). To eliminate CCFs we introduced a more accurate approach in assessment of earthquake and tsunami, and introduction of measures against tsunami inundation. Redundancy of safety systems could not eliminate CCF by extreme natural hazards. Safety system should be designed by due consideration of diversity and independence including spatial dispersement. In the fourth layer, multi-layered protective measures are also applied for severe accidents, which consists of “prevention of core damage” under multiple failure, “prevention of containment failure”, and “prevention of large release, that is controlled release by venting”. In the fifth layer, we also require operators to prepare measures for “suppression of radioactive materials dispersion”. Of course, off-site emergency preparedness  More>>
Authors:
Yamagata, H., E-mail: hiroshi_yamagata@nsr.go.jp [1] 
  1. Nuclear Regulation Authority, Minato-ku, Tokyo (Japan)
Publication Date:
Oct 15, 2014
Product Type:
Conference
Report Number:
IAEA-TECDOC-CD-1749
Resource Relation:
Conference: 5. International Conference on Topical Issues in Nuclear Installation Safety: Defence in Depth - Advances and Challenges for Nuclear Installation Safety, Vienna (Austria), 21-24 Oct 2013; Other Information: Invited presentation; Related Information: In: International Conference on Topical Issues in Nuclear Installation Safety: Defence in Depth — Advances and Challenges for Nuclear Installation Safety. Proceedings of an International Conference held in Vienna, Austria, 21-24 October 2013| 353 p.
Subject:
22 GENERAL STUDIES OF NUCLEAR REACTORS; AIRCRAFT; CONTAINMENT; DAMAGE; EARTHQUAKES; ENGINEERED SAFETY SYSTEMS; FAILURES; FISSION PRODUCT RELEASE; JAPAN; RADIATION PROTECTION; RADIOACTIVE MATERIALS; REACTOR ACCIDENTS; REACTOR CORES; REACTOR OPERATORS; REACTOR SAFETY; REDUNDANCY; RISK ASSESSMENT; SAFETY STANDARDS; TSUNAMIS
OSTI ID:
22318503
Research Organizations:
International Atomic Energy Agency, Safety Assessment Section, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Other: ISBN 978-92-0-158214-0; ISSN 1684-2073; TRN: XA14M7019024700
Availability:
Available from INIS in electronic form. Also available on-line: http://www-pub.iaea.org/MTCD/publications/PDF/TE-1749_CD_web.pdf and on 1 CD-ROM from IAEA, Marketing and Sales Unit, Publishing Section, E-mail: sales.publications@iaea.org; Web site: http://www.iaea.org/books
Submitting Site:
INIS
Size:
page(s) 11
Announcement Date:
Mar 21, 2015

Citation Formats

Yamagata, H., E-mail: hiroshi_yamagata@nsr.go.jp. The Defence in Depth Concept Applied to the New Regulatory Requirements in Japan. IAEA: N. p., 2014. Web.
Yamagata, H., E-mail: hiroshi_yamagata@nsr.go.jp. The Defence in Depth Concept Applied to the New Regulatory Requirements in Japan. IAEA.
Yamagata, H., E-mail: hiroshi_yamagata@nsr.go.jp. 2014. "The Defence in Depth Concept Applied to the New Regulatory Requirements in Japan." IAEA.
@misc{etde_22318503,
title = {The Defence in Depth Concept Applied to the New Regulatory Requirements in Japan}
author = {Yamagata, H., E-mail: hiroshi_yamagata@nsr.go.jp}
abstractNote = {Full text: The new regulatory requirements based on lessons learnt from Fukushima Daiichi accident, which places emphasis on Defense-in-Depth concept, was put into effect in Japan on 8th July, 2013. It is required to prepare multi-layered protective measures. Each layer should achieve the objective only in that layer regardless of the measures in the other layers. The challenge is how to enhance independence of measures between layers. In the third layer, the current concept of design regarding safety relies on “single failure”, whose condition is elimination of common cause failure (CCF). To eliminate CCFs we introduced a more accurate approach in assessment of earthquake and tsunami, and introduction of measures against tsunami inundation. Redundancy of safety systems could not eliminate CCF by extreme natural hazards. Safety system should be designed by due consideration of diversity and independence including spatial dispersement. In the fourth layer, multi-layered protective measures are also applied for severe accidents, which consists of “prevention of core damage” under multiple failure, “prevention of containment failure”, and “prevention of large release, that is controlled release by venting”. In the fifth layer, we also require operators to prepare measures for “suppression of radioactive materials dispersion”. Of course, off-site emergency preparedness and response has been enhanced by introduction of PAZ and UPZ. Introduction of “Specialized Safety Facility” against intentional aircraft crash will contribute enhancement of some layers by providing electricity and water under extremely severe conditions. The new regulatory requirements are not our goal, just a first step. It is expected for regulator and operators to improve safety continuously by periodic comprehensive safety assessments including IPE, IPEEE, Margin test, and etc. We have to make an upward spiral of nuclear safety. (author)}
place = {IAEA}
year = {2014}
month = {Oct}
}