The refueling of a nuclear power reactor, involving opening of the pressure vessel and associated plant maintenance, is characteristically planned to occur at a frequency on the order of a year or longer. The length of a boiling water reactor (BWR) operating cycle, the time between successive refueling shutdowns, may be extended several weeks to several months beyond normal “reactivity life” with proper planning. Reactivity for extended operation is available through the use of the negative moderator and fuel reactivity coefficient effects—especially the BWR void coefficient. The coastdown power reduction mode has been applied in 70% of recent cycles. Increased core flow and feedwater temperature reduction have also been used for cycle extension and to enhance operating maneuverability.