Method for replacing cracked core spray supply piping in a boiling water reactor

Abstract

A method for replacing cracked core spray supply piping in a boiling water reactor vessel includes removal of all or part of the core spray supply piping inside the reactor vessel and replacement of the piping with new piping components configured to couple with one another or any remaining core spray supply piping without being welded. In accordance with one aspect of the invention, a lower elbow of the core spray supply piping is removed and replaced with an elbow assembly configured to mechanically couple with an existing feed-through assembly at the core shroud, for example by use of friction fit, bias members, and/or bolts. A vertical section of the core spray supply piping feeding into the elbow can also be removed and replaced with a new piping section configured to mechanically couple with the replacement lower elbow assembly, for example using pins, clamps and sealing members such as piston rings. In accordance with another aspect of the invention, the vertical piping section is removed along with an upper elbow, horizontal core spray supply arms and the flow divider or T-box and replaced with a new T-box assembly and piping. The T-box assembly can be connected to the piping using any of the disclosed joints and can carry replacement thermal sleeves which fully replace or supplement existing thermal sleeves. Various biasing and detent mechanisms are disclosed for mechanically coupling the new T-box assembly with the existing safe end assembly.