Reactor

Purpose: To accommodate flow variable valves of the same number as those of guide pipes of control rods into a heavy water flow controller so that the valves may be opened and closed to change the distribution rate of the heavy water flow to thereby flatten the temperature of heavy water in a radial direction within the core, thus providing safety operation of the reactor. Constitution: Power distribution of the core is counted by an operator on the basis of process data of reactor such as control rod position and flow rate of core, and the flow distribution of heavy water, in which temperature distribution in a radial direction of a core outlet of heavy water is uniform, may be obtained by an operator device using the aforesaid distribution, and an electric signal for controlling the degree of opening of the flow variable valves in accordance with the heavy water flow distribution if generated. As a consequence, the flow distribution of heavy water may be varied and the temperature of heavy water is flattened to provide safety operation of the reactor. (Yoshino, Y.)