Abstract: A reactor core includes an inner core region that extends in a vertical direction, and has a plurality of first fuel pins accommodating an inner core fuel; an outer core region that extends in the vertical direction, is arranged to surround the inner core region from an outer peripheral side, and has a plurality of second fuel pins accommodating an outer core fuel; and a sodium plenum provided above the inner core region and the outer core region, in which a dimension of the outer core fuel in the vertical direction is larger than a dimension of the inner core fuel in the vertical direction, and the position of a center of the outer core fuel in the vertical direction is higher than the position of a center of the inner core fuel in the vertical direction.

Abstract: A nuclear reactor includes a reflector and a flow path. The reflector reflects neutrons, contains graphite and a moderator having a smaller moderating power than the graphite, and is sectioned into plural parts along a direction of flow of fuel pebbles. The flow path is surrounded by the reflector, and the fuel pebbles flow through the flow path and undergo nuclear reaction to generate power. Volume ratio of the graphite to the moderator having a smaller moderating power than the graphite in each part of the reflector is determined based on a power distribution in the reactor core in the direction of flow of the fuel pebbles.

Abstract: A nuclear reactor includes a reflector and a flow path. The reflector reflects neutrons, contains graphite and a moderator having a smaller moderating power than the graphite, and is sectioned into plural parts along a direction of flow of fuel pebbles. The flow path is surrounded by the reflector, and the fuel pebbles flow through the flow path and undergo nuclear reaction to generate power. Volume ratio of the graphite to the moderator having a smaller moderating power than the graphite in each part of the reflector is determined based on a power distribution in the reactor core in the direction of flow of the fuel pebbles.

Abstract: A nuclear reactor includes a reflector and a flow path. The reflector reflects neutrons, contains graphite and a moderator having a smaller moderating power than the graphite, and is sectioned into plural parts along a direction of flow of fuel pebbles. The flow path is surrounded by the reflector, and the fuel pebbles flow through the flow path and undergo nuclear reaction to generate power. Volume ratio of the graphite to the moderator having a smaller moderating power than the graphite in each part of the reflector is determined based on a power distribution in the reactor core in the direction of flow of the fuel pebbles.

Abstract: A nuclear reactor includes a reflector and a flow path. The reflector reflects neutrons, contains graphite and a moderator having a smaller moderating power than the graphite, and is sectioned into plural parts along a direction of flow of fuel pebbles. The flow path is surrounded by the reflector, and the fuel pebbles flow through the flow path and undergo nuclear reaction to generate power. Volume ratio of the graphite to the moderator having a smaller moderating power than the graphite in each part of the reflector is determined based on a power distribution in the reactor core in the direction of flow of the fuel pebbles.