Extension of core life-time in fast breeder reactor by introducing inner blanket and doping minor actinides

Highlights: → Effect of a fertile material of MA which transmuted to 238Pu in a FBR was studied. → The radial inner blanket was arranged at the center of the FBR core. → If MA is doped into the inner blanket, the long-life core can be achieved. → The main fission reaction zone is shifted from the active core to the inner blanket. → 238Pu worked as a fissile material enabled the long-life core. - Abstract: In order to achieve a longer-life Fast Breeder Reactor (FBR) compared with conventional one, the feasibility study based on proto-type large scale sodium cooled FBR has been performed by utilizing a characteristic of a fertile material of minor actinides (MA) and an inner blanket arranged radially at the center of the core. The analytical results showed that the long-life core without the inner blanket could be achieved by doping MA into an active core because 238Pu transmuted from MA worked as the fissile material. In case of the core with the inner blanket, it was found that if MA is doped into the inner blanket, the longer-life core also could be achieved by shifting of the main fission reaction zone geometrically from the active core to the inner core due to producing of 238Pu in the inner blanket. It was also found that if MA is doped into both the inner blanket and the active core, the core life can be extended further. As for the safety characteristics, it has been confirmed that the sodium loss reactivity is improved in case of introducing the inner blanket due to the enhancement of neutron leakage. It has also been confirmed that the sodium loss reactivity is largely affected if the region of high neutron flux, that is the region of main fission reaction is voided.