Development of New PWR Type Transport Casks

NFT is doing the transport of radioactive materials such as spent fuels, low level radioactive wastes in commission by Japanese Utilities (JU) in Japan, and the design development and the manufacture of the transport casks for its purpose. In the development of the cask for the transport of spent fuels from domestic nuclear power plants to JNFL reprocessing plant at Rokkasho, NFT has developed 4 types of NFT-type casks made of forged steel for BWR fuels, and 2 types of NFT-type casks made of multi-layered-structure with lead for PWR fuels, with different loading capacity. Up to the present, NFT has manufactured 32 BWR-type casks, and 21 PWR-type casks. On the PWR-type cask, multi-layered-structure using lead with high gamma shielding capability has been adopted in order to contain large quantities of spent fuels with short cooling time on demand of JU. In the consideration of small storage capacity of spent fuels for some PWR Plants, the PWR-type cask has been developed as to be able to contain fuels with short cooling time. At the time of initial developing, it was judged that the production cost of the multi-layered-type cask would be almost same compared with forged steel type casks. However, in the recent procurement of casks, in fact, the cost of the multi-layered-type casks is higher than the cost of forged steel type casks. This is because that the multi-layered-type cask needs special pouring and cooling process of lead with keeping bonding lead to steel walls, which needs special technique and much experience, to obtain high performance for heat removal in order to contain fuels with short cooling time, with the result that only few manufacturers compete for the procurement of the multi-layered-type cask. Therefore, NFT has begun to develop forged type PWR casks, because which would lead low price by competition among many suppliers on the procurement.