1,006,187. Controlling reactors. BELGE VULCAIN S.A. Feb. 1, 1963 [Feb. 13, 1962], No. 4166/63. Drawings to Specification. Heading G6C. In a nuclear reactor the poisoning (or reduction in reactivity) due to xenon 135 is compensated by controlling the concentration of neutron absorbers in the fluid moderator, coolant or reflector. In a pressurized water reactor incorporating spectral shift, boron, in the form of boric acid is introduced into the water in quantities controlled so as to maintain the total poisoning effect of the xenon 135 and boron at a required level. Automatic control of the boron injection may be effected in accordance with the temperature of the main coolant by thermocouple controlled valves.
