Method of injecting liquid neutron absorber

Purpose: To improve the reliability by shortening the time delay for the injection of neutron absorber. Method: A pipeway from a container containing liquid neutron absorber (aqueous boric acid) is connected by way of a valve to the intake side of a pump in a coolant cleanup system connected to a pressure vessel of a reactor. A pipeway for by-passing the coolant cleanup system is disposed between the exhaust side of the pump and the pressure vessel. With this structure, aqueous boric acid is injected, upon failure of control rod insertion, to the container under the ON-OFF operation of the valve through the following route: aqueous boric acid container → pump for coolant cleanup system → by-pass pipeway → pressure vessel. The use of the normally operated pump for the injection of liquid neutron absorber, decreases the operation delay in the boric acid injection, eliminates the need of explosion valve, simplifies the structure and facilitates the inspection. (Ikeda, J.)