Safety Assessment of Disposal Container for Higher Activity Low Level Waste

As one of the studies on “yoyushindo disposal” whose concept is similar to an intermediate disposal, the development of a disposal container has been conducted by the Federation of Electric Power Companies of Japan. To assess a drop event of a waste package in which stored the radioactive wastes from nuclear power plants, the toughness of the disposal container was evaluated by drop tests using three specimens which have actual dimensions, drop analysis, fracture mechanics assessment and macroscopic tests. The three specimens for drop tests were manufactured in consideration of the design specifications and the manufacture operations in nuclear power plants. The lid plates of the specimens were welded to the body plates without pre- and post-weld heat treatment by using a remote automated welding machine. The drop tests showed that no penetration cracks or splash of its content occurred in the disposal container under conservative conditions such as the maximum weight and height in the handling. Drop analysis and the fracture mechanics assessment indicate that the strain induced by the drop impact did not exceed the fracture strain and an unstable fracture did not occur. And macroscopic tests showed that penetration cracks did not occur at 8m drop events. These tests and evaluations confirmed that the disposal container had sufficient toughness.