Method and apparatus for controlling power distribution in a reactor

Purpose: To control control rods, in-pile heavy water level and concentration of liquid poison in heavy water to achieve an optimum power distribution through burn-up. Constitution: Reading of neutron fluxes at in-pile points is transmitted from neutron instrumentation to a distribution computer and a power level computer. As a result, the control rod is driven, and variation in power level at that time adjusts the degree of valve opening of a helium adjusting valve to change a heavy water level for adjustment. In the event, however, the heavy water level is lowered to the fuel zone or elevated to the upper pipe plate, a poison pouring amount adjusting valve or a removing tower flow adjusting valve is actuated to effect pouring or removal of poison. Thus, the heavy water level is limited within the upper reflector zone and the power level is maintained constant. (Yoshihara, H.)