Abstract: An axial power distribution control device includes an axial offset calculation unit 52, a parameter calculation unit 53, and an axial offset determining unit 55. The axial offset determining unit 55 predicts whether a core axial offset of the power distribution is increased or decreased after a current time, based on a major axis of an ellipse drawn by the xenon parameter and the iodine parameter calculated by the parameter calculation unit 53 and the xenon parameter and the iodine parameter at the current time. This makes it possible to predict a change of the axial offset of the power distribution of a reactor for suppressing a xenon oscillation in the reactor.

Abstract: [Problem to be Solved] To provide a fuel rod and a fuel assembly that can make thermal power uniform along an axial direction and lengthen an operation cycle. [Solution] In a first fuel rod 41 and a second fuel rod 42 each containing nuclear fuel and burnable poison for reducing a nuclear reaction of the nuclear fuel to be loaded in a pressurized water reactor, the gadolinium content rate of the first fuel rod 41 and the second fuel rod 42 is increased from both end portions toward a center portion in an axial direction. In a fuel assembly including the first fuel rod 41 and the second fuel rod 42, the first fuel rod 41 and the second fuel rod 42 are loaded in such a manner that a large percentage of the second fuel rod 42 that is a low-gadolinium fuel rod is arranged on an outer side than the first fuel rod 41 that is a high-gadolinium fuel rod.

Abstract: Parameters DAOPX (=AOP?AOX) and DAOIX (=AOI?AOX) are calculated based on axial offsets of the power distribution (AOX and AO1). A movement control of a control rod is then performed in such a manner that a plot point of a trajectory of the parameter DAOPX and the DAOIX is induced toward the major axis of an ellipse drawn by the trajectory, based on the parameters (DAOPX and DAOIX) and allowable ranges (DAOPX—L and DAOIX—L) obtained in advance. With this configuration, the xenon oscillation is suppressed by controlling the xenon oscillation in a simultaneous manner simply by controlling an axial power distribution in a reactor by a simple operation with a clear purpose.

Abstract: An axial power distribution control device includes an axial offset calculation unit 52, a parameter calculation unit 53, and an axial offset determining unit 55. The axial offset determining unit 55 predicts whether a core axial offset of the power distribution is increased or decreased after a current time, based on a major axis of an ellipse drawn by the xenon parameter and the iodine parameter calculated by the parameter calculation unit 53 and the xenon parameter and the iodine parameter at the current time. This makes it possible to predict a change of the axial offset of the power distribution of a reactor for suppressing a xenon oscillation in the reactor.