Automatic Radiation Measurement System for Transport of LLW

In Japan there are 50 nuclear power plants in operation at 18 sites, generating 41 GW of electricity (Fig.l). Approximately 28,000 low-level waste (LLW) drums are annually generated from these plants and placed in containers of 8 drums each, and then loaded into a specially built ship for shipment to Mutsu-Ogawara Port. They are subsequently transferred overland to the ~W Disposal Center, located 9 km from the port. The annual shipment is approximately 2,500 containers corresponding to 20,000 drums. This takes 12 voyages, as the ship carries approximately 210 containers on average. As the ship usually stays 2 days at the port, unloading operations of LL W drums must be accomplished during this short period (Fig.2). In order to transport all the containers to the Disposal Center, 60 round trips of 2-container trucks are required for 1 day. Radiation levels around the container are measured and confirmed before shipment at the nuclear power plants. Although the radiation level is not thought to increase during the voyage, measurements of the dose-equivalent rate are carried out on all of the containers in order to ensure the safety of land transport. The Automatic Radiation Measurement System, which we call \"Gate Monitor\", has been developed to meet the requirements at the port.