Abstract: A method of temporarily sealing a reactor pressure vessel during an outage permits the water level in the vessel to be drawn down to a level which enables the interior surfaces of associated structures and equipment in the primary coolant loop to be inspected while dry when the vessel is submerged in a pool of water. A reactor pressure vessel internals lifting rig is used to position a temporary reactor pressure vessel head having an elliptical shaped dome with a circumferential flange retaining a pair of spaced apart, circumferential seal rings onto a reactor pressure vessel circumferential flange without marking or damaging the reactor pressure vessel flange.

Abstract: A flux thimble removal tool includes two basic units: a lower pulling unit 20 and a cutting/storage unit 22 which sits atop the lower pulling unit. Pulling unit 20 houses a gripper unit 30a, drive motor 68, gears 32, 66, helix drive shaft 40a, guide bar 26a, slide bar 24a, and guide tube 36, all of which are adapted to gradually extract neutron flux thimbles 38 one at a time from the reactor vessel 74 of a nuclear reactor, and to feed each thimble to the cutting/storage unit 22. The cutting/storage unit 32 further extracts the thimble, then severs the further extracted portion. The operation is continued until the thimble is fully extracted from the reactor vessel and reduced to a pile of easily-disposable segments.

Abstract: A thimble which resists vibrations caused by turbulence in the coolant flow of a nuclear reactor includes a portion of preselected length with an increased outside diameter. The conventionally-sized thimble is sheathed with a tubing adapted for insertion within the reactor, the tubing at a leading end thereof being fixed to the conventionally-sized thimble and at a trailing end thereof being slidingly coupled to the conventionally-sized thimble. A bullet shaped member seals the leading end and facilitates its insertion.

Abstract: A sleeve-like sealing unit, particularly a thimble guide extender is adapted to be installed on and coaxially with a thimble guide mounted on a lower core plate of a nuclear reaction vessel and projects toward and terminates at a distance from an underface of a bottom nozzle forming part of a fuel assembly and supported on a top face of the lower core plate. The extender has a lower fitting adapted to surround the thimble guide at a bottom length portion thereof adjacent the top face of the lower core plate; and an upper fitting being axially displaceable relative to the lower fitting and being adapted to surround the thimble guide at a top length portion thereof. The upper fitting has an axial passage and a terminal opening defined by an outer annular radial face adapted to be in a face-to-face engagement with the underside of the bottom nozzle.

Abstract: A high pressure seal fitting with a built-in low pressure seal arrangement for sealing a space defined by an inner diameter of a pipe and a rod slidably disposed within the first pipe and extending beyond and end of the first pipe. The fitting includes a fitting body provided with an axial passage for slidably accommodating the rod and having a first end region constructed for engaging the end of the pipe for forming a high pressure seal between the pipe and the fitting body, and a second end region opposite the first end region and including an outer circumferential protrusion having the shape of a ferrule for cooperating with components utilized to form a compression seal to form a releasable high pressure seal. The fitting body further includes a low pressure sealing device disposed in the axial passage at the second end region of the fitting body for maintaining a low pressure seal between the fitting body and the rod when the releasable high pressure seal is disconnected.

Abstract: A thimble guide assembly for use in a nuclear reactor includes a lower element which can be screwed into a bore in a core plate and an upper element which can be screwed to the lower element. One of the screw-connections is right-handed while the other is left-handed. The length of the upper element is selected so that the exposed portion of a thimble tube, which extends through the thimble guide assembly and into a fuel assembly above it, is relatively modest, thereby minimizing the turbulence to which the thimble tube is exposed. The lower element of the thimble guide assembly is provided with a sleeve portion which extends through the bore in the core plate, and the tip of the upper element terminates in a planar, annular lip. Both elements are provided with surfaces for engagement by wrenches or other tools. The lower element has annular grooves for engagement by a lower spring clip which is welded to the core plate and an upper spring clip which is welded to the upper element.

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.