Accountability control system in plutonium fuel facility

More than 30 tons of plutonium-uranium mixed-oxide fuel have been manufactured at the Plutonium Facility in PNC for JOYO, FUGEN and DCA (Deuterium Critical Assembly) and for the purpose of irradiation tests. This report reviews the nuclear material accountability control system adopted in the Plutonium Facility. Initially, the main objective of the system was the criticality control of fissible materials at various stages of fuel manufacturing. The first part of this report describes the functions and the structure of the control system. A flow chart is provided to show the various stages of material flow and their associated computer files. The system is composed of the following three sub-systems: procedures of nuclear material transfer; PIT (Physical Inventory Taking); data retrieval, report preparation and file maintenance. OMR (Optical Mark Reader) sheets are used to record the nuclear material transfer. The MUF (Materials Unaccounted For) are evaluated by PIT every three months through computer processing based on the OMR sheets. The MUF ratio of Pu handled in the facility every year from 1966 to 1977 are presented by a curve, indicating that the MUF ratio was kept well under 0.5% for every project (JOYO, FUGEN, and DCA). As for the Pu safeguards, the MBA (Material Balance Area) and the KMP (Key Measurement Point) in the facility of PNC are illustrated. The general idea of the projected PINC (Plutonium Inventory Control) system in PNC is also shortly explained. (Aoki, K.)