Abstract: The ORIGEN2 code is adopted to calculate the amount of hydrogen production in the core and sump region after LOCAL in PWR nuclear power plants,to reduce the conservatism for the design evaluation of the combustible gas control in the containment.The calculation model of radiolytic decomposition coolant and other related calculation model are used to calculate the amount of hydrogen production after LOCA in a 600MW PWR nuclear power plant,and the results show that over conservatism of the original evaluation,and there still exists abundant time to prepare and startup the hydrogen recombiners in the containment after LOCAL.