Method of operating a nuclear reactor which maintains a substantially

Abstract

This invention provides a method of operating a nuclear reactor with the object of maintaining a substantially symmetric axial xenon distribution during normal power operation including load follow. Variations in the xenon distribution are controlled by maintaining a substantially symmetric axial power distribution. Procedures are described for maintaining the axial offset value of the core, as an indicia of the axial power distribution, substantially equal to a target value, which is modified periodically to account for core burnup. In one embodiment a neutron absorbing element within the core coolant, or moderator, is employed to assist control of reactivity changes associated with changes in power with the full length control rods mainly employed to adjust variations in the axial power distribution, while the part length rods remain completely withdrawn from the fuel region of the core. In a second embodiment reactivity changes associated with changes in power are controlled by the full length rods, while the part length rods are used to adjust the axial power distribution and the neutron absorbing element within the core coolant or moderator is used to compensate for xenon buildup or depletion.