Abstract: A self-aligning seal system for facilitating the repair or replacement of components of recirculation pump assemblies which penetrate the bottom head of the reactor pressure vessel of a boiling water reactor. The self-aligning seal system enables an operator to block off stub openings in the bottom portion of a water-filled reactor pressure vessel while performing maintenance in an underlying dry field without draining the coolant water from the reactor pressure vessel. To prevent leakage due to misalignment of the seal relative to the open end of the stub, the seal system is provided with a self-alignment guide member which centers the sealing unit relative to a diffuser opening coaxial with the stub as the sealing unit is lowered onto the stub.

Abstract: A self-aligning seal system for use in carrying out maintenance services in a nuclear fission reactor plant is disclosed. The self-aligning seal system enables an operator to block off openings in the lower portion of a water filled reactor pressure vessel for maintenance service in an underlying dry field without draining the coolant water from the reactor pressure vessel.