Key member and its application for insertion or removal of fuel rods and dis- assembling of nuclear fuel assembly

摘要

A key member 1 for the retraction of grid cell springs 5b during fuel rod insertion or removal from the grid comprises an elongate key body having first projections 3 on one side of the body for engaging cut-outs 5a in the grid straps 5 at the corners of the cells and second projections 4 on the opposite side of the body for engaging the springs 5b. During disassembly of a fuel assembly, the key members are inserted into the grids G1 - 9 through apertures 16 in the grid outer straps before the fuel rods are removed from the grids. Before the key members can be inserted pipes A3 for the control rods and 83 for instrumentation must be removed from the vicinity of apertures 16. This can be achieved by cutting each pipe in the vicinity of each aperture 16 using an elongated internal rotary cutting tool (figure 9, not shown) having a cutting block (20j) pivoted about a transverse axis (20k) and urged by a cam (20c) into engagement with the pipe inner wall, the pipe pieces being subsequently subjected to a bulging operation to shorten them. Alternatively, an elongated internal reciprocating cutting tool (figure 10, not shown) having a pair of opposed pivoted blades (20p) cammed into engagement with the internal wall of the pipe may be used to provide four slots in each pipe at each section where the pipe is joined to a bulge fastening to a grid sleeve 51, 52, the slots allowing the bulged portions of the pipe to contact radially so that the pipe may be removed from the assembly altogether. IMAGE