Neutron detector for instrumentation of outer shell in a reactor

Object: To mutually hold a neutron detector, a moderator block, a receiving vessel and a top cover through resilient members interposed between gaps to thereby increase quake resisting property. Structure: The impact force caused by earthquake or the like is absorbed by a resilient member (such as spring, rubber) between a neutron detector and left and right moderator blocks, resilient member between the lower moderator block and the upper cover, and a resilient member such as spring, washer or the like between the receiving vessel and the screw. (Seki, T.)