Study on Estimating Leak-tightness on Dual-Purpose Metal Cask after Long-Term Storage

Spent fuel from nuclear power plants (NPP) is designated as useful recycled resources and shall be properly stored until reprocessing according to the policy of Japan. Recently, the quantity of spent fuels stored at each NPP site is increasing due to, for example, delay of domestic reprocessing project. The long-term interim dry storage facilities of spent fuels, which is away from the reactors and adopt dual-purpose metal cask system, are expected to be early realized. For cask for interium storage, its lid will not open until it is received at reprocessing facility, even before shipping, since restricing occpational radiation exposrue risk as low as possible, for example. And then, it is impotant to confirm the integrity of casks experienced long term storage during tranport. NUPEC has been conducting the dual-purpose metal cask verification test project since1999 Japanese fiscal year (JFY) under sponsorship of the Ministry of Economic, Trade and Industry (METI).