Method of calculation for LLFP transmutation in a fast reactor

Jin, Tomoyuki*; Oki, Shigeo 

Transmutation of long-lived fission product (LLFP) using a fast reactor has been investigated in the framework of the feasibility study on commercialized fast reactor cycle systems in Japan. Neutron-moderating material is used in LLFP target subassembly for the sake of enhancing the transmutation efficiency, which causes the considerable changes of neutron distribution both in space and energy. At the present calculation the Monte Carlo method is employed for exact treatment of such a complicated system. Moreover the calculation method based on deterministic codes should be needed when we perform core design calculations and physical analysis. This study aimed at the establishment of a super cell modeling for LLFP target subassembly by using the general-purpose deterministic code system, SRAC95. In the fiscal year 2001, a super cell modeling has been worked out which appropriately deals with the incoming neutrons from the adjacent fuel region to the LLFP target, under the condition that the LLFP target is represented as homogeneous region.