Uranium refining and conversion plant decommissioning project

ウラン製錬転換施設のデコミッショニングプロジェクト

在間 直樹; 森本 靖之; 杉杖 典岳; 門 一実

Zaima, Naoki; Morimoto, Yasuyuki; Sugitsue, Noritake; Kado, Kazumi

The uranium refining and conversion plant at Ningyo-toge (URCP) was constructed in 1981 for the purpose of demonstration on refining and conversion processes from yellow cakes to UF via UF. Through 20 years, 385 tons of natural uranium of UF and 336 tons of reprocessed uranium of UF had been conducted. The basic policies are the optimization of the labor costs and the minimization of the radioactive wastes. The procedures are followings; (1) monitoring by high sensitivity surveymeters and identificating nuclide by ray spectrometry, (2) estimating uranium mass inventory, (3) planning workers distributions including of radiation control staffs, (4) deciding dismantling methods and decontaminating schematically if required, (5) measuring and classifying doserate and contamination level, (6) managing for radioactive waste container, (7) control for personal exposures. Through two years and half, almost all equipment had been dismantled except building decontamination. Several hundreds tons of dismantled wastes had accumulated in 200 litter drums. In addition, the secondary wastes had also been generated. Several thousands day of working time had spent totally. Simultaneously we are now developing for waste measuring systems with better accuracy. The further tasks imposed us summarized the followings; (1) dismantling method for higher doserate area, (2) reduction of radioactive wastes volume, (3) decontamination for the buildings, (4) waste disposal.