Device for controlling output distribution in a reactor

Object: To provide a heavy-water-moderated light water-cooled reactor having a core in which a plurality of moderators or coolant circulation loops are provided to flatten output distribution. Structure: The core is divided into several heavy water tanks, heavy water being supplied by a circulation pump from the tank to the heavy water tanks. The loop has another circulation pump, and B is added to the heavy water passing therethrough within a dissolver or B is conversely removed from the heavy water by a heat exchanger to thereby control B-contents within the heavy water. Neutron absorber B within the heavy water is adjusted for each of the heavy water tanks to flatten output distribution of the core. (Kamimura, M.)