Thermal hydraulic analysis and estimation of hydrogen generation in severe accidents in WWER1000

Severe Accidents Management (SAM) in nuclear power plants is an important safety issue. SAMs require assessing the thermal-hydraulic conditions of the nuclear reactor during the accident. This paper investigates three accident scenarios, Station Black-Out (SBO), SBO with Large Break Loss of Coolant Accident (LBLOCA), and SBO with Small Break Loss of Coolant Accident (SBLOCA) in the WWER1000/V446 reactor using the MELCOR1.8.6 code. The RELAP3.2-SCDAP code is also used to evaluate the accuracy of the reactor pressure vessel parameters.  The purpose of this study was to determine the operating conditions of the reactor during the accident scenarios with emphasis on hydrogen production. The results showed that the SBO has the highest hydrogen production (2150 kg) compared to other accidents and the maximum fuel temperature occurred sooner than the other SAs (11800 seconds). The results obtained by the two codes and the Final Safety Analysis Report (FSAR) of the WWER1000/V446 reactor showed good agreement. The results of this analysis help make the appropriate decision in SAM.