Direct disposal concepts of spent mixed oxide fuel from light water reactors based on heat transfer calculations

Abe, Takumi ; Nishihara, Kenji  

Methods of direct disposal of mixed oxide spent fuel (MOXSF) consumed in light water reactors were investigated via heat transfer calculation. The temperature of the buffer material surrounding the waste is the most stringent limitation on the direct disposal of MOXSF. Therefore, the effects on the maximum temperature of the buffer material were examined by changing the occupied area, cooling term of MOXSF, and other parameters considering the direct disposal of uranium spent fuel. The results showed that it is necessary to change the cooling term and disposal depth in addition to the change of the occupied area. Accordingly, some disposal concepts that satisfy the limitation of the maximum buffer material temperature were derived, and estimates revealed that the occupied area per unit waste of the MOXSF is three to five times that of uranium spent fuel.