Development of probabilistic risk assessment methodology of decay heat removal function against combination hazard of low temperature and snow for sodium-cooled fast reactors

A probabilistic risk assessment (PRA) should be performed not only for earthquake and tsunami which are major natural events in Japan but also for other natural external hazards. However, PRA methodologies for other external hazards and their combination have not been sufficiently developed. This st...

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Autores principales:	Hiroyuki NISHINO, Hidemasa YAMANO, Kenichi KURISAKA
Formato:	article
Lenguaje:	EN
Publicado:	The Japan Society of Mechanical Engineers 2018
Materias:	probabilistic risk assessment combination hazard decay heat removal system core damage frequency dominant core damage sequence Mechanical engineering and machinery TJ1-1570
Acceso en línea:	https://doaj.org/article/587838137ba7491891b6e43ae2036533
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spelling	oai:doaj.org-article:587838137ba7491891b6e43ae20365332021-11-26T07:21:52ZDevelopment of probabilistic risk assessment methodology of decay heat removal function against combination hazard of low temperature and snow for sodium-cooled fast reactors2187-974510.1299/mej.18-00079https://doaj.org/article/587838137ba7491891b6e43ae20365332018-06-01T00:00:00Zhttps://www.jstage.jst.go.jp/article/mej/5/4/5_18-00079/_pdf/-char/enhttps://doaj.org/toc/2187-9745A probabilistic risk assessment (PRA) should be performed not only for earthquake and tsunami which are major natural events in Japan but also for other natural external hazards. However, PRA methodologies for other external hazards and their combination have not been sufficiently developed. This study is aimed at developing a PRA methodology for the combination of low temperature and snow for a sodium-cooled fast reactor which uses the ambient air as its ultimate heat sink to remove decay heat under accident conditions. The annual exceedance probabilities of low temperature and of snow can be statistically estimated based on the meteorological records of temperature, snow depth and daily snowfall depth. To identify core damage sequence, an event tree was developed by considering the impact of low temperature and snow on decay heat removal systems (DHRSs), e.g., a clogged intake and/or outtake for a DHRS and for an emergency diesel generator, an unopenable door on necessary access routes due to accumulated snow, failure of intake filters due to accumulated snow, and possibility of water freezing in cooling circuits. Recovery actions (i.e., snow removal and filter replacement) to prevent loss of DHRS function were also considered in developing the event tree. Furthermore, considering that a dominant contributor to snow risk can be failure of snow removal around intakes and outtakes caused by loss of the access routes, this study has investigated effects of electric heaters installed around the intakes and outtakes as an additional countermeasure. By using the annual exceedance probabilities and failure probabilities, the event tree was quantified. The result showed that a dominant core damage sequence caused by a snow and low temperature combination hazard is the failure of the electric heaters and the loss of the access routes for snow removal due to low temperature and snowfall which last for a day, and daily snowfall depth of 2 m/day.Hiroyuki NISHINOHidemasa YAMANOKenichi KURISAKAThe Japan Society of Mechanical Engineersarticleprobabilistic risk assessmentcombination hazarddecay heat removal systemcore damage frequencydominant core damage sequenceMechanical engineering and machineryTJ1-1570ENMechanical Engineering Journal, Vol 5, Iss 4, Pp 18-00079-18-00079 (2018)
institution	DOAJ
collection	DOAJ
language	EN
topic	probabilistic risk assessment combination hazard decay heat removal system core damage frequency dominant core damage sequence Mechanical engineering and machinery TJ1-1570
spellingShingle	probabilistic risk assessment combination hazard decay heat removal system core damage frequency dominant core damage sequence Mechanical engineering and machinery TJ1-1570 Hiroyuki NISHINO Hidemasa YAMANO Kenichi KURISAKA Development of probabilistic risk assessment methodology of decay heat removal function against combination hazard of low temperature and snow for sodium-cooled fast reactors
description	A probabilistic risk assessment (PRA) should be performed not only for earthquake and tsunami which are major natural events in Japan but also for other natural external hazards. However, PRA methodologies for other external hazards and their combination have not been sufficiently developed. This study is aimed at developing a PRA methodology for the combination of low temperature and snow for a sodium-cooled fast reactor which uses the ambient air as its ultimate heat sink to remove decay heat under accident conditions. The annual exceedance probabilities of low temperature and of snow can be statistically estimated based on the meteorological records of temperature, snow depth and daily snowfall depth. To identify core damage sequence, an event tree was developed by considering the impact of low temperature and snow on decay heat removal systems (DHRSs), e.g., a clogged intake and/or outtake for a DHRS and for an emergency diesel generator, an unopenable door on necessary access routes due to accumulated snow, failure of intake filters due to accumulated snow, and possibility of water freezing in cooling circuits. Recovery actions (i.e., snow removal and filter replacement) to prevent loss of DHRS function were also considered in developing the event tree. Furthermore, considering that a dominant contributor to snow risk can be failure of snow removal around intakes and outtakes caused by loss of the access routes, this study has investigated effects of electric heaters installed around the intakes and outtakes as an additional countermeasure. By using the annual exceedance probabilities and failure probabilities, the event tree was quantified. The result showed that a dominant core damage sequence caused by a snow and low temperature combination hazard is the failure of the electric heaters and the loss of the access routes for snow removal due to low temperature and snowfall which last for a day, and daily snowfall depth of 2 m/day.
format	article
author	Hiroyuki NISHINO Hidemasa YAMANO Kenichi KURISAKA
author_facet	Hiroyuki NISHINO Hidemasa YAMANO Kenichi KURISAKA
author_sort	Hiroyuki NISHINO
title	Development of probabilistic risk assessment methodology of decay heat removal function against combination hazard of low temperature and snow for sodium-cooled fast reactors
title_short	Development of probabilistic risk assessment methodology of decay heat removal function against combination hazard of low temperature and snow for sodium-cooled fast reactors
title_full	Development of probabilistic risk assessment methodology of decay heat removal function against combination hazard of low temperature and snow for sodium-cooled fast reactors
title_fullStr	Development of probabilistic risk assessment methodology of decay heat removal function against combination hazard of low temperature and snow for sodium-cooled fast reactors
title_full_unstemmed	Development of probabilistic risk assessment methodology of decay heat removal function against combination hazard of low temperature and snow for sodium-cooled fast reactors
title_sort	development of probabilistic risk assessment methodology of decay heat removal function against combination hazard of low temperature and snow for sodium-cooled fast reactors
publisher	The Japan Society of Mechanical Engineers
publishDate	2018
url	https://doaj.org/article/587838137ba7491891b6e43ae2036533
work_keys_str_mv	AT hiroyukinishino developmentofprobabilisticriskassessmentmethodologyofdecayheatremovalfunctionagainstcombinationhazardoflowtemperatureandsnowforsodiumcooledfastreactors AT hidemasayamano developmentofprobabilisticriskassessmentmethodologyofdecayheatremovalfunctionagainstcombinationhazardoflowtemperatureandsnowforsodiumcooledfastreactors AT kenichikurisaka developmentofprobabilisticriskassessmentmethodologyofdecayheatremovalfunctionagainstcombinationhazardoflowtemperatureandsnowforsodiumcooledfastreactors
_version_	1718409657256509440

Development of probabilistic risk assessment methodology of decay heat removal function against combination hazard of low temperature and snow for sodium-cooled fast reactors

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