Spring lock washer for tie rod nuts

Abstract

In a nuclear fuel bundle, an improved lock washer is disclosed for permitting ease of remote removal of hex nuts on tie rods for the remote submerged disassembly of fuel bundles after use in a reactor. The improved lock washer includes two spaced apart and interconnected tie rods surrounding washer members, each of these tie rod washer members having radially inwardly extending keys. These keys register to corresponding keyways in the threaded ends of the tie rods to prevent tie rod rotation and threaded disengagement from the lower tie plate. Each washer member is manufactured from a spring material and includes at least one and preferably two radially protruding tangs T. These tangs are elongate and bent in an inverted U-shaped configuration. The inverted U-shaped configuration commences at the washer member and extends upwardly and outwardly away from the hex bolt to be locked. Reversal of the spring member occurs at the end of the U with the spring member returning angularly back towards the tie rod. In the return toward the tie rod, a gradual inward slope defining a gathering surface between the tie rod and bolt on one hand and the U-shaped tang on the other hand is defined that the U-shaped tang. From the end of the gathering surface, the tang extends vertically downward in a position of spring interference with one of the flat sides of the hexagonal bolt holding the tie rod in place. When the tie rod washer is in place with the nut fastened, the tang prevents the bolt from turning responsive to vibration and upward force on the upper tie plate due to outflowing water and steam. In remote disassembly of the fuel bundle, the gathering surface permits the tang to be biased away from the sides of the bolt by a specialized socket that penetrates interstitially between the lock washer and nut and captures the nut when it is unscrewed. The lock washer because of its spring action returns to its initial shape after the socket and nut are removed. In contrast to the prior art lock washer, the lock washer tangs strains and deformations are elastic. The possibility of tang breakage is eliminated and the lock washers can be reused.