Abstract
The relevance of this research is associated with the need to analyze subcriticality under all regulated and accidental storage scenarios during the long-term storage of spent nuclear fuel (SNF) from the BN-350 reactor. Although all necessary calculations and studies were performed during the development and design of the storage facility, updated calculations are required to confirm the safe storage of BN-350 SNF as a real and aging facility. The objective of this work was to assess container storage from the standpoint of nuclear safety, ensuring guaranteed subcriticality under certain accident conditions The results of the storage cask system (SCS) containing eight fuel canisters show that when the SCS with SNF is in either mechanically intact or damaged condition, and even when surrounded by a group of SCS units, the effective multiplication factor k eff changes insignificantly. However, it begins to increase when water appears in the calculated configurations. The most critical situation occurs when a steam–water mixture forms in the cavities of the container and canisters, which may occur due to degradation of protective barriers