TOOL AND METHOD FOR ADJUSTING SPRING FORCE OF SPACER SPRING

PROBLEM TO BE SOLVED: To provide a tool and a method for adjusting the spring force of a spacer spring by preparing a probe and a holder having an arm capable of displacing, inserting the probe in a spacer opening and displacing the arm and the spring when controlling the spring force of the spring in the spacer cell opening of the spacer for nuclear fuel bundle. SOLUTION: The adjusting tool has a probe, a head, an arm and a micrometer attached to the head. A micrometer handle is turned to a predetermined setting to slide the arm in the state that the probe is inserted in a spacer cell opening. The opposite end of the arm from the fitting between a micrometer drive head fits the spring of the pacer cell to displace and its spring force is adjusted. In the first state, the arm is contained in the probe, the micrometer drive head displaces the tip end of the arm outward, accordingly displaces the spring outward and reduces the spring force by this. For a spacer tool in another state, the arm is apart from the probe and its slide contact surface rides on the spring. By turning the micrometer handle to the predetermined setting, the drive head is moved and as the results the spring is displaced inward the spacer cell opening to increase the spacer spring force.