Method of increasing reactor power

Purpose: To increase the reactor power at a constant increasing rate by incorporating two types of fluid poisons of different neutron absorption cross section in heavy water moderators and varying the ratio of concentrations between the fluid poisons during reactor power increase. Method: Gadolinium has 46,000 barn of neutron absorption cross section which is 34 times as great as 1,350 barn of boron 10B. Considering that gadolinium has a much faster burning velocity and the inclusion thereof in an appropriate amount in heavy water automatically increases the reactor power by its burning effect, boron and gadolinium are used as the liquid poisons. The reactor power is increased at a constant velocity of 0.3%/hr up to 50% - 100% power by the burning of gadolinium, when calculated on a heavy water moderated reactor whose neutron flux level at the rated power is about 1 x 1014 n/cm2 sec. (Seki, T.)