Evaluation of dose rate variation during very long term storage of RBMK-1500 reactor used fuel

Abstract

The duration of dry storage of RBMK-1500 used fuel in casks is foreseen to be 50years. It is expected that a deep geological repository will be implemented in Lithuania after this storage period. Research activities on used nuclear fuel disposal in a deep geological repository have lasted for several decades and are still ongoing in different countries. However, until now there is no such repository in operation worldwide. Therefore, there is a possibility that due to the various reasons the deep geological repository cannot be constructed in the planned time. In such a case, an option of used fuel storage beyond 50years needs to be considered. Various nuclear research centres in different countries are already performing investigations on subjects related to extension of the used fuel storage period. This paper presents modelling results of the total dose rates for CASTOR®RBMK-1500 and CONSTOR®RBMK-1500 casks during long-term storage (up to 300years). Also, contributions of neutron and gamma doses to the total dose rate, variations of the neutron and gamma doses and influence of different gamma and neutron energy groups on dose rates during long-term storage are analysed.