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NKS Programme Area:NKS-R
Research Area:Risk analysis and probabilistic methods
Report Number:NKS-349
Report Title:MC3D simulations of ex-vessel steam explosions in IDPSA framework
Activity Acronym:DPSA
Authors:Taneli Silvonen,
Abstract:This study aims to supplement previous work performed in [1] by providing more detailed analysis on ex-vessel steam explosion loads posed to containment structure of a BWR reactor. The analyses are conducted with MC3D code, which is a multidimensional numerical tool devoted to analysis of FCI phenomena. Results can be reflected to steam explosion modelling implemented in a level 2 PRA model developed last year, and the analysis can thus be regarded to be an application of IDPSA methodology. Focus of this study is on safety considerations and complex physics and mathematical modelling are given less (if any) attention. The analysis cases are studied for two different vessel failure modes and by using two fragmentation models. The basis case is a single large central hole in the reactor pressure vessel lower head, and the second melt ejection mode is a result from multiple simultaneous failures of vessel penetrations, representing instrumentation and control rod guide tube failures. Limited sensitivity analyses are performed for fragmentation model parameters and for explosion triggering time. Results showed generally quite large pressures and impulses in comparison to e.g. results obtained in OECD’s SERENA program [2], and for multiple melt jets the pressure loads were even higher than for single jet case. Throughout the analyses there were difficulties to trigger explosions and to compare different cases thus became more complicated. Although it is difficult to validate results and more detailed modelling would be necessary in order to draw more credible conclusions, this study produced useful information e.g. from IDPSA perspective and also enhanced modelling capabilities at VTT.
Keywords:IDPSA, PSA, FCI, Ex-vessel steam explosions, Level 2 PRA, MC3D
Publication date:27 Aug 2015
ISBN:ISBN 978-87-7893-433-8
Number of downloads:933
Download:pdf NKS-349.pdf
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