OUTLINE OF FRESH MOX FUEL TRANSPORTATION IN JAPAN AND DEVELOPMENT STATUS OF TRANSPORTATION CASK FOR LWR

In Japan, the operation of JNFL (Japan Nuclear Fuel Ltd.) MOX fuel fabrication plant for LWR (JMOX plant) will be started in March 2016, and the preparatory work by JNFL is proceeding with steady steps. The introduction of the MOX fuel into the LWRs in Japan is aimed from the viewpoint of the policy on nuclear energy, and it is in progress certainly. MOX fuels are transported from J-MOX plant in Rokkasho to the LWR plants in Japan. The transportation cask is type B(M) package. The transportation cask for JNFL MOX fuel (J-MOX cask) is designed to increase the volume of contents as much as possible within the handling restriction of the cask in J-MOX plant. J-MOX casks consists of two types designed for BWR and PWR fuels, which are of about 6m in length × about 2.4m in diameter including the shock absorber, and of about 24 tons in weight including the contents. The capacity of the J-MOX cask for BWR is 12 MOX fuel assemblies; 8×8 type or 9×9 type, and J-MOX cask for PWR is 4 MOX fuel assemblies; 17×17 type. BWR fuel is loaded in the fuel holder with fuel tightening function before loaded into the cask. On the other hand, the fuel holder is not necessary for PWR because the cask tightens the fuel directly. As characteristics of J-MOX cask, multistage cylindrically shaped shock absorbers are used to absorb impact from all direction. Propylene Glycol water solution is used as a neutron shielding material in the lateral of the cask. Helium gas is filled inside the cask to improve conductivity of decay heat during transportation. Safety analysis is performed by a proven analysis code for B(M) package licensing. It is scheduled to apply for design approval by the Japanese Authority in the near future, and the transportation test using the dummy fuel will be executed before actual transportation.