R&D activities at Nuclear Safety Research Center in JAEA for safety decommissioning of various nuclear facilities

Mukai, Masayuki ; Shimada, Taro ; Tanaka, Tadao ; Sukegawa, Takenori; Nakayama, Shinichi 

Nuclear Safety Research Center in JAEA has been conducting R&D activities to support national safety regulatory systems. (1) Research on safety assessment for decommissioning of nuclear fuel cycle facilities: A prototype computer code for fuel cycle facilities was developed by improving the code previously developed for nuclear reactor facilities. (2) Research on dose evaluation during dismantling: Values on evaluation parameters were obtained through the cutting test using actual contaminated pipes. Observed values for dispersion ratio of Co-60 and filtration efficiency indicated that existing recommendation values were conservative for safety assessment. (3) Research on site release on termination of decommissioning: A computer code was developed to calculate remaining radionuclide concentrations as site release criteria, and improved by adding practical settings for external and internal exposed doses. Preliminary calculations were conducted on typical land reuse scenario.