Patent ID: 8126105

Claim:
A fast reactor having a reflector control system comprising: a reactor vessel which is filled with a liquid metal coolant; a reactor core including a fuel assembly, which is placed at a central position of the reactor vessel; and a neutron reflector provided outside the reactor core so as to be moved in a vertical direction in an installed state of the fast reactor for adjusting leakage of neutrons from the reactor core so as to control a reactivity thereof; wherein the neutron reflector is moved in an upward direction in accordance with a change in reactivity caused by burn-up of a fuel, and the neutron reflector has a high reflection region at least at a lower side thereof, the high reflection region having a high fast-neutron reflection ability as compared to that of the other region, wherein the reactor core further includes a neutron absorption assembly which is placed at a central position of the fuel assembly, wherein the neutron absorption assembly comprises a core shutdown rod and a fixed absorber, accommodated in a case member, and wherein a structure of the core shutdown rod placed at a central position of the case member is different from a structure of the fixed absorber disposed outside of the core shutdown rod.