Analyses of an Unmitigated Station Blackout Transient in a Generic PWR–900 with ASTEC, MAAP and MELCOR Codes (NUREG/IA-0515)

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Publication Information

Manuscript Completed: March 2019
Date Published: September 2019

Prepared by:
F. Mascari*, J. C. De La Rosa Blul**, M. Sangiorgi**, G. Bandini*

Via Martiri di Monte Sole 4
40129, Bologna, Italy

** European Commission JRC, Westerduinweg 3,
1755 LE Petten, The Netherlands

H. Esmaili, NRC Project Manager

Division of Systems Analysis
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Prepared as part of:
The Agreement on Research Participation and Technical Exchange
Under the Cooperative Severe Accident Research Program (CSARP)

Published by:
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Availability Notice


The aim of the work presented in this report, jointly developed by ENEA and the European Commission JRC within the Code for European Severe Accident Management (CESAM) project funded by the 7th Framework Programme of the European Commission, is focused on the analysis of an unmitigated SBO accident in a generic Western three-loop PWR 900 MWe, until RPV failure, with MAAP 5.02 and MELCOR 2.1 code to benchmark ASTEC 2.1 code, in the field of severe accident sequence application, considering selected figures of merit as a basis for comparison. The main thermal-hydraulic and in-vessel degradation phenomena, as simulated by the three severe accident codes, have been analyzed. A detailed quantitative analysis of the core energy balance, of the core degradation and relocation, corium physical and chemical composition together with the influence played by natural circulation flows between the core, upper plenum and steam generators predicted by the three codes is not presented here but it is planned for future research activity.

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