Study on Dose-Equivalent Rate Evaluation System of LL W Packages

Japanese low level waste disposal facility is located at Rokkasho in Aomori Pref., northern part of Japan. This facility accepts only low level wastes from nuclear power stations. At present, the wastes are limited to the homogeneous wastes which are solidified in 200L open drums. Before the transport, some inspections on waste drums are executed such as the surface dose equivalent rate and an axial compressive strength, etc., in order to ensure that those are conformed to the acceptance criteria of the disposal. In the transport, waste drums are loaded to LL W packaging. 1be packages are classified to IP-2 package of IAEA regulation. The packages are transported using trucks from the power station storage facility to the harbor. Then the packages are loaded onto a dedicated vessel named Seiei-maru, and transported to Rokkasho Facility. Just before leaving power stations, the dose equivalent rate around the packages and trucks should be ensured to conform to the transport regulation. In this confirmation, maximum dose equivalent rate around packages and trucks are needed to compare to the standard value. If the confirmation is accomplished by actual dose rate measurement, many workers have to measure all around the packages and the trucks, and consequently the radiation exposure to the workers could not be ignored.