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NKS Programme Area:NKS-R
Research Area:Risk analysis and probabilistic methods
Report Number:NKS-315
Report Title:Feasibility Study for Connection Between IDPSA and conventional PSA Approach to Analysis of Nordic type BWR’s
Activity Acronym:DPSA
Authors:Pavel Kudinov, Sergey Galushin, Sebastian Raub, Viet-Anh Phung, Kaspar Kööp, Ilkka Karanta, Taneli Silvonen, Yvonne Adolfsson, Ola Bäckström, Anders Enerholm, Pavel Krcal, Klas Sunnevik,
Abstract:This report summarizes the experience achieved within the NKS-DPSA project during 2013. The project is motivated by the discussions at the Workshop on Integrated Deterministic-Probabilistic Safety Analysis (IDPSA-2012). The aim of the project has been to: summarize the state of the art review of the probabilistic, deterministic and IDPSA analysis; and to carry out a feasibility study. The following areas are covered in this study: mapping, information collection and identification of areas of certain interest based on existing PSA; results of analysis of core relocation scenarios taking into account timing of PSA Level 1 events and possible recovery actions on the melt conditions in the lower head; results of feasibility study on connection between conventional PSA, DSA and IDPSA methods. There are three topics for the feasibility studies identified: a transient with complete or partial failure of the hydraulic scram; station black-out with varying degrees of safety system recovery; steam explosion. Experiences from performed studies are summarized in the report as well as suggestions of areas which need further investigations. The results from the IDPSA show that an increased number of thermohydraulic calculations, performed according to an intelligent algorithm, can improve the understanding of the sequences and therefore input to the PSA or to the deterministic safety analyses. There is a good potential for development of a mathematical model to represent the IDPSA results in form of a decision tree as input for the quantification of the PSA Level 2 structure. Steam explosion analyses exploiting IDPSA methodology would necessitate more detailed approach than VTT’s contribution presented here, with use of dedicated analysis codes for FCI phenomena and structural response of the containment. Nevertheless, joint use of MELCOR and SPSA for steam explosion analysis provided a good basis that can easily be refined further.
Keywords:IDPSA, PSA, SPSA, DSA, BWR, Severe accident, MELCOR, core degradation, steam explosion
Publication date:03 Jul 2014
ISBN:ISBN 978-87-7893-394-2
Number of downloads:3126
Download:pdf NKS-315.pdf
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