Patent Number: 
Section: claims

1. A fast reactor controlled with a reflector comprising:a reactor vessel accommodating therein a coolant;a reactor core disposed in the reactor vessel and immersed in the coolant; anda reflector that vertically moves for adjusting leakage of neutrons generated from the reactor core to control a reactivity of the reactor core, the reflector including a neutron reflecting part disposed on an outside of the reactor core in a vertically movable manner, and a cavity part positioned above the neutron reflecting part, the cavity part having a neutron reflecting ability lower than that of the coolant, said cavity part includes a frame, and a plurality of sealable containers of a box shape that are held in the frame;wherein the neutron reflecting part is formed of a plurality of metal plates that are stacked on each other,each of the metal plates has a plurality of coolant channels through which the coolant flows,and the number of the coolant channels in each of the metal plates per unit area increases from a side of the reactor vessel to a corresponding side of the reactor core. 2. The fast reactor controlled with the reflector according to claim 1, whereinthe frame is formed of a plurality of frame units, andthe respective frame units are connected to each other by a bolt. 3. The fast reactor controlled with the reflector according to claim 1, whereinthe respective sealable containers are fitted to the adjacent sealable containers to be vertically connected to each other, or are fitted in an intermediate rib of the frame to be vertically connected to each other. 4. The fast reactor controlled with the reflector according to claim 1, whereina resilient member(s) is (are) disposed between an upper end of the uppermost sealable container in the frame and an upper end of the frame, and/or between a lower end of the lowermost sealable container in the frame and a lower end of the frame. 5. The fast reactor controlled with the reflector according to claim 1, whereina reflector drive unit is connected to an upper portion of the cavity part via a universal joint and a drive shaft, andthe neutron reflecting part is connected to the cavity part via a universal joint. 6. The fast reactor controlled with the reflector according to claim 1, whereina gap is formed between the neutron reflecting part and the cavity part. 7. The fast reactor controlled with the reflector according to claim 1, whereina volume of the neutron reflecting part excluding the coolant channels is between 80% and 95% of a total volume of the neutron reflecting part. 8. The fast reactor controlled with the reflector according to claim 1, whereina volume of a structural member constituting the cavity part is not less than 10% of a total volume of the cavity part.