Abstract: The reactor vessel thread protector is a metal cover that is placed over the exposed stud, nut and washer projecting above the closure head to protect the threads from accidental corrosive leakage impingement emitted from mechanical seals on the top of the reactor vessel head. The stud protector includes a drip pan to collect any such fluid being emitted from the reactor vessel. Additionally, the reactor vessel stud thread protector will provide protection from accidental deformation to a stud due to operator maintenance around adjacent studs. The reactor vessel stud thread protector can be in the form of a cylinder which would cover a single stud bolt or a curved box having a rectangular cross-section that would cover a plurality of stud bolts.

Abstract: A thimble guide extender for use in a nuclear power plant shields the thimble from turbulence and absorbs vibration from it to reduce wear. The extender includes an extension element which is secured to the thimble guide, a spring bushing which is attached to the extension element and which contacts the thimble, and a cap. In one embodiment the cap clamps the spring bushing, and in other embodiments it simply shields the bushing from turbulence. In one embodiment the spring bushing is an element having a cylindrical portion on one side and dimpled spring legs on the other, in another embodiment the spring bushing is an element having bent spring legs on either side, and in another embodiment the spring bushing is provided by dimpled spring legs that are integral with the extension element. The extension element is provided with locking fingers which secure the extension element to the thimble guide.

Abstract: An upwardly convex resilient annular strainer, fixed to the secondary core support base plate in a PWR, bends to remain in contact with the lower hemispherical head section of the pressure vessel as the gap between the internals and the lower hemispherical head section varies in size with reactor temperature to prevent debris from lodging in the gap where it could lead to reactor damage.

Abstract: A thimble guide extender for use in a nuclear power plant provides a shielded passage beteewn the guide and the bottom nozzle of a fuel assembly to protect the thimble from turbulence. The extender includes a hollow element having an upper portion which contacts the bottom nozzle, a lower portion which extends around the sides of the thimble guide, and a thimble passage through which the thimble movably extends. In one embodiment the thimble passage is aligned with a channel in the thimble guide by being permanently attached to the bottom nozzle of the fuel assembly. For this purpose the hollow element is provided with locking fingers which extend into flow openings in the bottom nozzle. In another embodiment the thimble passage of the hollow element is aligned with the channel of the thimble guide by being operatively mounted on the thimble guide, with spring fingers having enlarged regions or with locking balls fitting into an annular groove in the thimble guide.

Abstract: A method for extracting debris from the bottom of a water-filled nuclear reactor vessel. The method includes steps of removing the vessel closure head, upper internals and at least some fuel assemblies from the reactor vessel to expose a flow hole which is contained in the lower core plate and which has a perimeter, wherein imaginary vertical projection lines extending from the perimeter define an obstructed volume between the lower core plate and the bottom of the vessel, lowering a pipe having an open free end into the vessel so that the pipe extends through the exposed flow hole in the lower core plate and has its free end in close proximity to the bottom of the vessel, applying suction to the end of the pipe remote from the open free end to withdraw water and debris from the bottom of the vessel through the pipe, and removing the debris from the water withdrawn from the vessel and discharging the debris-free water into a reservoir.