Application of a severe accident code to the sensitivity and uncertainty analysis of hydrogen production in the WWER1000/V446

Abstract An uncertainty analysis based on the Latin Hypercube Sampling (LHS) method and MELCOR code for hydrogen production during a SA in WWER1000 nuclear reactor is presented. Firstly, the total amount of the produced hydrogen during the SBO with Large Break Loss of Coolant Accident (SBO-LBLOCA), SBO with Small Break Loss of Coolant Accident (SBO-SBLOCA) and Station Black Out (SBO) is estimated by the MELCOR code and benchmarked with the RELAP-SCDAP. In addition, the uncertainty of the effective parameters on the hydrogen generation is analyzed during both in-vessel and ex-vessel phases of the SA. The results showed that the SBO produces more hydrogen compared to other accident scenarios. Also, the range of the produced hydrogen varies between 255 and 525 kg and 812–1820 kg during the in-vessel and ex-vessel phases of the SBO, respectively. The falling debris heat transfer coefficient and Zr melt release temperature have the greatest effect on the hydrogen generation.