Abstract: The fissile inventory required in operating a negative power coefficient nuclear reactor in an electric power generating system is reduced by cycling the load imposed on the system when 100% power can no longer be maintained at equilibrium due to xenon poisoning in order to induce an oscillation in the xenon concentration which is in antiphase wtih the power requirements so that 100% power can be maintained at least during part of the day. The load can be progressively reduced by a preset amount each night or a xenon suppression controller which forecasts the xenon reactivity at the time selected for a return to full power as a function reactor history, current reactor flux and an arbitrary load schedule can be used to determine the maximum reduced power level that will permit operation at full power at the selected time.