Bradwell latch ring assembly removal

Latch ring assemblies (LRAs) were fitted at each control rod standpipe at Bradwell Power Station to prevent the inadvertent lifting of the lower section of the control rod assembly when the upper section was being lifted. In time oxidation of the mild steel components in the carbon dioxide reactor coolant gas led to the possibility of oxide jacking causing failure of retaining bolts with the consequent likelihood of debris entering fuel channels. As a consequence of a change to operating procedures LRAs were rendered redundant and this permitted their removal from the reactor. An electro-hydraulic manipulator was designed to enter a standpipe and engage with the latch ring before removing the retaining bolts by over-tightening. The LRA could then be lowered into a support cradle and reduced in size by plasma cutting, the parts being stored in a debris container and removed from the reactor. (UK)