Modelling of RBMK-1500 SNF storage casks activation during very long term storage

Existing interim spent nuclear fuel storage facility (SNFSF) at Ignalina nuclear power plant in Lithuania is fully loaded with CASTOR^®RBMK-1500 and CONSTOR^®RBMK-1500 storage casks. The planned lifetime of these casks is 50 years and the first loaded cask was moved to the SNFSF in 1999. The start of operation of disposal facility in Lithuania is foreseen later than the planned interim storage ends. So, the possibilities to extend the storage period over 50 years should be considered. Therefore, the casks decommissioning issues should be taken into account, as due to prolonged neutron irradiation casks materials could became activated. This paper presents modelling results of storage casks neutron activation during 300 year storage period. Modelling results show, that after 50 years of storage, side-wall and bottom of CASTOR^®RBMK-1500 cask are activated above clearance criteria. However, for 100–300 year storage period all of the casks components could be free released. - Highlights: • Neutron activation modelling of RBMK-1500 SNF storage casks components during 300 years interim storage period is presented. • Induced activity in every component of CASTOR®RBMK-1500 cask is higher compared to the same component of CONSTOR^®RBMK-1500. • Main nuclides in the metal parts of both casks are: short-lived Fe-55, Co-60 Mn-54 and long-lived Ni-59, 63, Mo-93 and Nb-94. • For the concrete components of CONSTOR^®RBMK-1500 cask, long-lived Ca-41, Ba-133 and C-14 also appear.