Infinite multiplication factor of low-enriched UO2–concrete system

The possibility of criticality of fuel debris in a form of uranium dioxide (UO2)-concrete mixture is evaluated by calculating the infinite multiplication factor (k(infinity)) for a study of criticality control on the fuel debris generated through the molten core concrete interaction in a severe accident of a light water reactor. The infinite multiplication factor can be greater than unity, which means that handling of the mixture is subject to criticality control. This paper shows that concrete provides efficient neutron moderation and points out the necessity of further investigations on the criticality of UO2-concrete system for actual handling of fuel debris.