Abstract: A method of decommissioning a nuclear reactor is provided in which radiation exposure is minimized. The method includes the steps of encapsulating portions of the reactor vessel and reactor internals into a solid reactor capsule and then converting this reactor capsule into a plurality of decommissioned segments. The encapsulating step preferably includes the step of forming a matrix within the chamber which integrally attaches to the vessel and integrally embeds the reactor internals to create a solid reactor capsule. Such a reactor capsule has an outer shell which is formed from the vessel and which substantially encases the matrix and thus the reactor internals. More particularly, this encapsulating is preferably accomplished by providing a fluidized matrix-creating material, preferably concrete, which may be predictably solidified and which functions as a radioactive shield in its solid state.

Abstract: A method for replacing a vessel in a piping system utilizes a template to determine the relative spatial positions of the pipe connections to the vessel in the existing system. The template is then removed from the existing system and reassembled on the new vessel in a remote location to determine the relative spatial position of the new pipe connections to the new vessel to ascertain if alignment will exist between those new pipe connections and the existing pipes in the system. If not, the pipe connections on the new vessel are initially reworked in the remote location to achieve alignment within connection tolerances. The pipes are then cut at their respective connections to the old vessel, the old vessel is removed, the new vessel is put in place in the system and the cut ends of the pipes are connected to new connections on the new vessel to complete the installation of the new vessel in the piping system.

Abstract: The control element assembly in a nuclear reactor is connected to its extension shaft by spring collet structure whose sections are locked to the extension shaft by a plunger actuated by a spring which is also a part of the buffer mechanism of the assembly.