Effect of new drywell cooler application for venting start time during severe accidents

Nuclear power plants are equipped with a hardened containment venting system and a filtered containment venting system to avoid a primary containment vessel (PCV) break by over-pressurization. Considering the gas release from these venting systems, it is desirable to delay venting start time or to a...

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Autores principales:	Naoyuki ISHIDA, Yasunori NAGATA, Ryusuke KIMURA, Koji ANDO
Formato:	article
Lenguaje:	EN
Publicado:	The Japan Society of Mechanical Engineers 2020
Materias:	severe accident drywell cooler condensation non-condensable gas downward flow external water injection internal water circulation Mechanical engineering and machinery TJ1-1570
Acceso en línea:	https://doaj.org/article/0485e160feb0480096e176d9db69833e
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spelling	oai:doaj.org-article:0485e160feb0480096e176d9db69833e2021-11-29T05:56:30ZEffect of new drywell cooler application for venting start time during severe accidents2187-974510.1299/mej.19-00550https://doaj.org/article/0485e160feb0480096e176d9db69833e2020-03-01T00:00:00Zhttps://www.jstage.jst.go.jp/article/mej/7/3/7_19-00550/_pdf/-char/enhttps://doaj.org/toc/2187-9745Nuclear power plants are equipped with a hardened containment venting system and a filtered containment venting system to avoid a primary containment vessel (PCV) break by over-pressurization. Considering the gas release from these venting systems, it is desirable to delay venting start time or to avoid operation of the systems by ensuring sufficient PCV cooling in view of the time needed to evacuate residents and the half-life of the radioactive materials. We have been developing a new drywell cooler specialized for severe accidents (DWC_SA) as one additional PCV cooling method. The DWC_SA can cool the PCV by continuous steam condensation using downward flow induced by natural force without any electrical devices in the PCV. We have already conducted element tests using a small tube bundle to confirm the occurrence of continuous downward flow with the DWC_SA configuration and to measure heat transfer rate of condensation with non-condensable gas (NCG). The heat transfer model was validated using the element test data. Here, to estimate plant performance of a representative advanced boiling water reactor (ABWR) applying the DWC_SA, we carried out a severe accident analysis using the MAAP code. We originally installed the heat transfer rate map of the DWC_SA as a function of pressure and NCG ratio in the code. The velocities using in the heat transfer model were estimated from CFD analysis. According to the severe accident analysis results, the DWC_SA can extend venting start time sufficiently to allow evacuation of residents in the accident scenario (LOCA with large pipe failure + ECCS failure + SBO) with the external water injection into the PCV and it can avoid operation of the containment venting systems in the case of internal water circulation in the PCV.Naoyuki ISHIDAYasunori NAGATARyusuke KIMURAKoji ANDOThe Japan Society of Mechanical Engineersarticlesevere accidentdrywell coolercondensationnon-condensable gasdownward flowexternal water injectioninternal water circulationMechanical engineering and machineryTJ1-1570ENMechanical Engineering Journal, Vol 7, Iss 3, Pp 19-00550-19-00550 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	severe accident drywell cooler condensation non-condensable gas downward flow external water injection internal water circulation Mechanical engineering and machinery TJ1-1570
spellingShingle	severe accident drywell cooler condensation non-condensable gas downward flow external water injection internal water circulation Mechanical engineering and machinery TJ1-1570 Naoyuki ISHIDA Yasunori NAGATA Ryusuke KIMURA Koji ANDO Effect of new drywell cooler application for venting start time during severe accidents
description	Nuclear power plants are equipped with a hardened containment venting system and a filtered containment venting system to avoid a primary containment vessel (PCV) break by over-pressurization. Considering the gas release from these venting systems, it is desirable to delay venting start time or to avoid operation of the systems by ensuring sufficient PCV cooling in view of the time needed to evacuate residents and the half-life of the radioactive materials. We have been developing a new drywell cooler specialized for severe accidents (DWC_SA) as one additional PCV cooling method. The DWC_SA can cool the PCV by continuous steam condensation using downward flow induced by natural force without any electrical devices in the PCV. We have already conducted element tests using a small tube bundle to confirm the occurrence of continuous downward flow with the DWC_SA configuration and to measure heat transfer rate of condensation with non-condensable gas (NCG). The heat transfer model was validated using the element test data. Here, to estimate plant performance of a representative advanced boiling water reactor (ABWR) applying the DWC_SA, we carried out a severe accident analysis using the MAAP code. We originally installed the heat transfer rate map of the DWC_SA as a function of pressure and NCG ratio in the code. The velocities using in the heat transfer model were estimated from CFD analysis. According to the severe accident analysis results, the DWC_SA can extend venting start time sufficiently to allow evacuation of residents in the accident scenario (LOCA with large pipe failure + ECCS failure + SBO) with the external water injection into the PCV and it can avoid operation of the containment venting systems in the case of internal water circulation in the PCV.
format	article
author	Naoyuki ISHIDA Yasunori NAGATA Ryusuke KIMURA Koji ANDO
author_facet	Naoyuki ISHIDA Yasunori NAGATA Ryusuke KIMURA Koji ANDO
author_sort	Naoyuki ISHIDA
title	Effect of new drywell cooler application for venting start time during severe accidents
title_short	Effect of new drywell cooler application for venting start time during severe accidents
title_full	Effect of new drywell cooler application for venting start time during severe accidents
title_fullStr	Effect of new drywell cooler application for venting start time during severe accidents
title_full_unstemmed	Effect of new drywell cooler application for venting start time during severe accidents
title_sort	effect of new drywell cooler application for venting start time during severe accidents
publisher	The Japan Society of Mechanical Engineers
publishDate	2020
url	https://doaj.org/article/0485e160feb0480096e176d9db69833e
work_keys_str_mv	AT naoyukiishida effectofnewdrywellcoolerapplicationforventingstarttimeduringsevereaccidents AT yasunorinagata effectofnewdrywellcoolerapplicationforventingstarttimeduringsevereaccidents AT ryusukekimura effectofnewdrywellcoolerapplicationforventingstarttimeduringsevereaccidents AT kojiando effectofnewdrywellcoolerapplicationforventingstarttimeduringsevereaccidents
_version_	1718407566346682368

Effect of new drywell cooler application for venting start time during severe accidents

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