Fast reactor controlled with a reflector

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;
• and
• a 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.