Infinite multiplication factor of low-enriched UO-concrete system

Izawa, Kazuhiko ; Uchida, Yuriko; Okubo, Kiyoshi; Totsuka, Masayoshi; Sono, Hiroki ; Tonoike, Kotaro 

Possibility of criticality of fuel debris in a form of UO-concrete mixture is evaluated by calculating infinite multiplication factor () for a study of criticality control on the fuel debris generated through the molten core concrete interaction (MCCI) in a severe accident of a light water reactor (LWR). 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 have efficient slowing-down capability of neutron and points out the necessity of further investigations on the criticality of low-enriched UO-concrete system for actual handling of fuel debris.