Evaluation of criticality safety measures for fuel storage of critical assemblies in STACY

Ishii, Junichi; Izawa, Kazuhiko ; Okubo, Takuya; Ogawa, Kazuhiko 

For compliance with the new regulatory requirements in Japan, the Static Critical Experiment Facility (STACY) has been remodeling the existing fuel storages. In the remodeling, the existing fuel storage spaces, to which shape and dimension management are applied, are designed to add a neutron absorber for the critical control, taking into account the case of shape and dimension collapse. In order to confirm the validity of the criticality safety design, subcritical calculations were performed. In the calculations, the Japanese Evaluated Nuclear Data Library, JENDL-3.2, was used to cross reference the data. The neutron multiplication factor was calculated using a continuous-energy Monte Carlo code, MVP, and PIJ code in the SRAC code system. It has been confirmed from the results that all fuel storages comply with the safety criteria required to ensure subcriticality.