INVESTIGATION OF HYDROGEN PRODUCTION IN ACCIDENT SCENARIOS OF VVER-1200 REACTOR COMPARING ZIRCONIUM-BASED CLADDING WITH ACCIDENT TOLERANT FUEL USING SERPENT MONTE CARLO CODE

Hydrogen production in severe nuclear accidents poses a significant threat to reactor safety, as exemplified by the Fukushima Daiichi disaster. This study investigates hydrogen generation in the VVER-1200 reactor under accident conditions, focusing on the zirconium-steam reaction responsible for hydrogen release in Zircaloy cladding. Using the SERPENT Monte Carlo simulation code, we model the reaction rates and hydrogen production volumes at elevated temperatures (1200°C), simulating a loss-of-coolant accident (LOCA). Results show substantial hydrogen production from the zirconium-steam reaction, with rates escalating with increasing burnup due to thermal and neutron flux effects. Conversely, Accident Tolerant Fuel (ATF) cladding materials such as SiC composites and FeCrAl alloys exhibit negligible hydrogen production, as they do not react with steam under similar conditions. The findings highlight ATF’s superiority in mitigating hydrogen-related risks, ensuring reactor integrity, and preventing potential explosions. This comparative analysis highlights the clear advantages of ATF cladding materials in reducing oxidation kinetics, minimizing hydrogen evolution, and enhancing reactor safety margins. The findings underscore the critical importance of incorporating ATF into the design and operation of VVER-1200 reactors and other advanced nuclear systems to mitigate hydrogen-related risks, prevent explosions, and ensure reactor integrity during severe accidents.