Abstract: The outer tubular shroud (14) of the measuring pipe (10) comprises a plurality of internally machined spacers (30), each intended to receive a set of measuring devices (32). The spacers (30) are connected by successive lengths of flexible tubing. The outer shroud (14) is open at its end part which emerges into the reactor core and comprises openings (27) in its side wall. This shroud is thus placed under equal pressure and the measuring devices (32) are in direct contact with the reactor coolant fluid.

Abstract: An arrangement for temporarily sealing the space between two substantially parallel, adjacent plates in which a flexible, partially inflatable seal is located between the plates to effect primary and secondary sealing interfaces along the upper and lower edges of the plates, respectively. The seal has a wedge-shaped upper portion, a tubular lower portion and a substantially solid intermediate shank. The tubular end of the seal is inflated so that it expands into contact with the lower edges of the plates, drawing the wedge-shaped upper portion of the seal toward the tubular portion, thereby forming primary sealing interfaces between the wedged-shaped portion and the upper edges of the plates. The contact of the inflated tubular portion with the lower edges of the plates forms secondary seal interfaces. The effectiveness of the seal can be tested by measuring the pressure in the chambers formed between each set of primary and secondary sealing interfaces.

Abstract: A nuclear reactor containment arrangement has a permanent cavity ring seal extending across an annular expansion gap between a reactor pressure vessel and a containment wall to provide a water tight seal therebetween. The annular ring seal has a support ring with an inner downwardly extending cylindrical section resting on the reactor flange and an outer downwardly extending cylindrical section resting on a shelf in the containment wall. A vertically extending, L-shaped, seal extends between an inner end of the support ring while a vertically extending, L-shaped, seal extends between the outer cylindrical section and the containment wall shelf. Neutron shielding material is suspended, by support rods, within the annular expansion gap while thermal insulation is provided therebelow. Manways and ports in the support ring are sealed by hatches and provide access to the annular expansion gap and, while open, provide for flow of cooling air from the annular expansion gap through the support ring.

Abstract: An annular seal ring between a reactor pressure vessel and a containment wall is disposed in an annular expansion gap therebetween, having a support ring and inner and outer upwardly extending cylindrical sections. The inner cylindrical section is disposed below a flange on the reactor and has a flexible seal therebetween, while the outer cylindrical section terminates substantially parallel and spaced from a shelf in the containment wall with a flexible seal therebetween. The annular seal ring is supported by radial support beams, while support rods depending from the support ring position neutron shielding material in the annular expansion gap. Manways and ports provide access to the gap and thermal insulation is provided below the neutron shielding material to direct cooling air from the annular gap up through opened manway and port.

Abstract: In order to place in sealed communication two reactor containments provided with openings capable of having a displacement between their axes, an assembly (12) is placed between the flanges (B.sub.1, B.sub.2) delimiting these openings, said assembly comprising two mobile linking parts (30a, 30b) according to a common axis, these parts bearing lip seals (36a, 36b) coming to take sealed support on the flanges under the action of a control (52) and springs (44) mechanism. Two double doors (14a, 14b) can be placed inside the openings and the linking parts in order to ensure separation of the containments. These double doors are formed of doors (16a, 18a, 16b, 18b) interconnected by means of magnets (62a, 64a, 62b, 64b) authorizing a certain relative sliding.

Abstract: In a nuclear boiling water reactor, an improved lower tie-plate and fuel channel interface for a boiling water reactor fuel bundle is disclosed. The fuel bundle has a lower tie-plate for supporting fuel rods and permitting the introduction of fluid interior of the fuel bundle. An upper tie-plate maintains the lower tie-plate supported rods in side-by-side relation and has apertures for discharging a mixture of water and steam. The fuel rods extend between the tie-plates for the generation of steam with some of the fuel rods forming a threaded connection fastening the tie-plates together. A polygon sectioned channel, preferably square, surrounds the tie-plates and fuel rods for the confining of fluid flow between the tie-plates interior of the bundle. The interface of the channel as it surrounds the lower tie-plate is reconfigured.

Abstract: Clamps and clamping systems for sealing the interface between two generally tubular conduits are disclosed. The clamps of the present invention are especially well adapted for use in nuclear reactor systems, especially as clamps for the instrument port interfaces of nuclear reactors. The clamps are comprised of articulated members pivotally joined by link plates such that the clamp may be opened in jaw like fashion so as to allow easy assembly around the conduits to be sealed. The open ends of the clamps contain datum surfaces which are brought into intimate contact when the clamp is fully assembled. The datum surfaces preload the clamp so as to exert the proper axial pressure on the conduit interface. In one embodiment, the interior surface of the clamp contains a generally flat sloped surface which is used to exert the appropriate axial pressure on the interface between the conduits.

Abstract: A liquid metal nuclear reactor has a sodium tank, having a closed arcuate bottom and upstanding cylindrical wall for containing a reactor core in a pool of liquid metal coolant, which is disposed in a guard tank having a bottom and upwardly extending cylindrical shell, and a support inside the guard tank adjacent the closed bottom of the sodium tank to support the two tanks in spaced relationship to each other. The sodium tank has an open top spaced from an overlying closure deck, with the cylindrical shell of the guard tank secured to the closure deck. The support is preferably an inner ledge. Support legs are also provided about the bottom periphery of the guard tank adapted to rest on a base mat of a reactor cavity.

Abstract: An auxiliary seal for preparing a reactor coolant pump for vacuum degasification of the reactor coolant system includes at least a pair of sealing segments. The sealing segments are composed of metal and have semicircular shaped bodies with attaching ears and an anchoring flange fixed thereon. The attaching ears extend radially outward from opposite ends of the sealing segment bodies. The ears on one segment body when aligned with and attached by fasteners to the ears on the other segment body draw the sealing segments together in releasably attached relation to one another and in sealing and clamping engagement about a shaft of the pump. The segment bodies also have interior and exterior circumferential recesses with O-rings therein which seal respectively with a portion of the pump shaft and a portion of a housing of the pump. The annular flange extends radially outward from the sealing segment bodies and is attachable to the housing portion for anchoring the seal segments thereto.

Abstract: A reactor cavity seal and shielding system for a PWR that protects personnel from radiation during full power operation and shutdown conditions, and allows the refueling canal to be flooded while allowing access to the lower portions of the reactor well. An integral annular seal and shield is sealed to the pressure vessel and to the primary shield. The seal preferably extends horizontally from a flange on the reactor pressure vessel to an inwardly extending ledge on the primary shield, and carries a generally coextensive body of solid neutron-absorbing material. The seal may be fabricated from stainless steel, and preferably incorporates a bellows seal to accommodate thermal expansion. The shield may be silicone rubber, refractory concrete, or any solid neutron absorber.

Abstract: A gas-cooled high temperature reactor having a core filled with spherical fuel elements is provided comprising a graphite side reflector including at least one nose-like projection comprised of a plurality of graphite nose stones stacked one upon the other, said nose stones each including at least one vertically disposed continuous cavity aligned with at least one vertically disposed continuous cavity in adjacent nose stones, said cavity adapted to receive discrete absorber material elements introduced into the reactor core, said nose stones further including at least one vertically aligned continuous gap which extends into said nose stones from a front portion thereof and is aligned with a corresponding continuous gap in adjacent nose stones, communication between said continuous gap and said cavity being prevented, said nose stones also comprising in top and bottom surfaces thereof sealing means which enable adjacent nose stones to be stacked in a manner sufficient to seal said at least one cavity in a gas-

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 reactor stud hole plug unit having a mandrel with a central stem having a threaded upper portion, a longitudinal passageway extending therethrough and a mandrel plate attached to the lower end. The mandrel plate has threads on its periphery which engage internal threads on a stud hole in a nuclear reactor, and an annular stop is located at the upper end of the threads on the mandrel plate which engages a shoulder on the cavity when the mandrel plate is in position in a stud hole. A compression plate with a central opening having a diameter slightly larger than the diameter of the upper portion of the mandrel stem fits over the mandrel stem, and an annular sealing ring is positioned around the periphery of the mandrel plate above the annular shoulder and in contact with the compression plate when the compression plate is positioned over the mandrel stem.

Abstract: An improved plugging system for plugging chamfered flow ports of small diameters in the core barrel of a pressurized water nuclear reactor is disclosed herein. The system is comprised of improved core barrel plugs that are telescopically contractible to facilitate installation, as well as a handling tool having a compact hydraulic ram and plug-holding cradle that is easily manipulable in the limited access space between the core barrel and thermal shield of the reactor for inserting and expanding the plugs into sealing engagement with the core barrel flow ports. The plugs of the system are formed from a generally cylindrical plug body that is radially expandible, and a retaining ring that is telescopically engaged around the plug body which allows it to be slid toward the middle of the plug prior to installation in order to minimize the overall length of the plug prior to the insertion operation.

Abstract: The seal for turning valve bodies, in particular for valves in radioactive lants, is composed of a molded element of flexible graphite which is coated with a thin, flexible tantalum layer. The tantalum enclosure surrounds the graphite molded element, preferably all around. The tantalum layer is sufficiently thin so that it remains flexible.

Abstract: Clamps and clamping systems for sealing the interface between two generally tubular conduits are disclosed. The clamps of the present invention are especially well adapted for use in nuclear reactor systems, especially as clamps for the instrument port interfaces of nuclear reactors. The clamps are generally comprised of articulated members pivotally joined by link plates such that the clamp may be opened in jaw like fashion so as to allow easy assembly around the conduits to be sealed. The conduit seal assembly includes an upper positioner which has a frusto-conically shaped surface and a male flange with a frusto-conically shaped upper surface. These two surfaces create an annular wedge-like opening for accepting a wedge-shaped upper clamp. The upper articulated clamp when assembled thus provides the proper clamping force between the conduit seal and male flange.

Abstract: Apparatus for sealing the seam between two conduits which includes two cooperatively threaded members for applying relative axial clamping forces to the conduits. When the two cooperatively threaded members are relatively rotated, they apply relative axial force to the conduits thereby causing a sealing means to be disposed in tight contact between the conduits.

Abstract: A valve body 10 supports a rotary valve member 20 having a transfer port 22. Sealing between a port 17 of the valve and the member 20 is achieved by a sleeve 30 movable towards and away from the member 20. In a valve closed position seal means in a flat end of the sleeve engage a flat base of a recess in the member 20. The member 20 may be provided with a rotary scraper 41 and heaters located in channels 40 and in this construction the valve is suitable for transferring sodium-cooled nuclear fuel between various localities.

Abstract: An automatic safety rod for a nuclear reactor containing neutron absorbing material and designed to be inserted into a reactor core after a loss-of-core flow. Actuation is based upon either a sudden decrease in core pressure drop or the pressure drop decreases below a predetermined minimum value. The automatic control rod includes a pressure regulating device whereby a controlled decrease in operating pressure due to reduced coolant flow does not cause the rod to drop into the core.

Abstract: An end closure for a nuclear fuel flask in which the gate, which is movable between open and closed positions across an end of the flask, has first and second portions which are urged apart, conveniently by spring-loaded means. A door has upper and lower wedge-shaped members mounted on and releasably connected to the respective gate portions. In use, a displacement of the gate into or out of its fully closed position effects movement of one only of the gate portions and its associated door member. As the door members are wedge-shaped the other door member is urged into or out of sealing engagement with the end of the fuel flask.

Abstract: A pipe end sealing element for use in hydrotesting of plain end pipes, such as instrument tubes of a nuclear reactor, and a method of hydrotesting of such plain end pipes. The pipe sealing element comprises a hollow tubular member with a bevelled flange at one end and a threaded portion at the other end, a hollow conical bushing of decreasable interior diameter having a bevelled surface complementary to the bevelled surface of the tubular member, a sealing plug and threaded bolt engageable with the threaded portion of the hollow tubular member. The hollow tubular member is placed about the open end of the pipe, with the threaded portion thereof adjacent and beyond the pipe end, and inserting the conical bushing into the hollow tubular member about the pipe wall. The sealing plug is placed on the pipe end and the threaded bolt engaged with the threads of the hollow tubular member.

Abstract: A swing gate closure assembly for nuclear reactor tipoff assembly wherein the swing gate is cammed open by a fuel element or spacer but is reliably closed at a desired closing rate primarily by hydraulic forces in the absence of a fuel charge.

Abstract: An annular plate is mounted on and sealed to the spaced apart pressure vessel flange and vessel containment structure of a nuclear reactor to form a leak-proof bottom for a refueling canal for the reactor. The sealing arrangement for the plate establishes redundant seals to each of the flange and containment structure, the seals being pneumatically expandable to enhance the integrity thereof.

Abstract: Disclosed is a method of installing a reversibly porous, air-diffusible, water-restrictive, polymer plug in a port that extends through the wall of a nuclear waste storage container. The plug is inserted a predetermined distance, for example, with the aid of a screwdriver applied to a slot in the plug's outer face. When inserted, the plug prevents the loss of nuclear waste through the port while the air-diffusible nature of the material allows gases to pass through the material. The resultant venting action of the plug prevents the creation of pressure differences between the interior of the container and the environment. Thus, the likelihood of the container becoming overpressurized and leaking is minimized. In addition, the water-restrictive nature of the plug material restricts the ingress and egress of water from the container, reducing the likelihood of groundwater contamination during storage.

Abstract: A facility for posting irradiated fuel from a preparation chamber of a dry storage complex into storage canisters within a clean chamber and for posting contaminated canisters from a closed bucket in the clean chamber into the preparation chamber. The facility comprises two coaxial tubular port members extending from the preparation chamber into the clean chamber, the port members having masking means for the canister and bucket closures and means for withdrawing them into the preparation chamber.

Abstract: An improvement in a reactor cavity pool seal which includes a seal plate between the reactor and the cavity wall and an inflatable annular seal, wherein the inflatable seal operates between a seal ring and bearing plate which are elements in addition to the seal plate and cavity wall, thereby eliminating problems of eccentricity and clearance.

Abstract: A gas cooled high temperature nuclear reactor utilizes an independent cooling system for the safety enclosure surrounding the reactor vessel. The cooling system comprises means for circulating cooling medium at least on the reactor side of a concrete safety enclosure shell and a separate closed cooling loop for circulation of separate cooling medium through a reservoir of the first cooling medium and to the outside of the entire nuclear reactor installation.

Abstract: A removable check valve for interconnecting the discharge duct of a pump and an inlet coolant duct of a reactor core in a pool-type nuclear reactor. A manifold assembly is provided having an outer periphery affixed to and in fluid communication with the discharge duct of the pump and has an inner periphery having at least one opening therethrough. A housing containing a check valve is located within the inner periphery of the manifold. The upper end of the housing has an opening in alignment with the opening in the manifold assembly, and seals are provided above and below the openings. The lower end of the housing is adapted for fluid communication with the inlet duct of the reactor core.

Abstract: A bolt and keeper secure nuclear steam generation isolation dam segments in assembled relation. The bolt is rotated into locked position with its handle in a slot as a transverse projection on the bolt end is moved along a ramp into a securing notch against the bias of a compressible rubber spring.

Abstract: Disclosed is a nuclear reactor employing a liquid metal and containing a reactor vessel, and at least one satellite vessel, and a hot and a cold leg connecting means which combine to form a continuous pathway for the flow of the liquid metal between the reactor vessel and the at least one satellite vessel. Each of the hot leg and cold leg connecting means contain a bellows assembly which are readily accessible for repair or replacement without draining the reactor vessel of the liquid metal.

Abstract: Sealing apparatus and method, comprising first and second surfaces or membranes, at least one of which surfaces is deformable, placed in proximity to one another. Urging means cause these surfaces to contact one another in a manner such that the deformable surface "deforms" to conform to the geometry of the other surface, thereby creating a seal. The seal is capable of undergoing multiple cycles of sealing and unsealing.

Abstract: A metal conduit assembly for interconnecting the discharge duct of the pump and the inlet coolant duct or reactor core in a pool-type nuclear reactor. The conduit assembly comprises an upper section for connection to the discharge of a reactor pump, a lower section for connection with the coolant inlet duct with reactor core and a third intermediate tubular section for interconnecting the other two sections. Joint means are provided for interconnecting one end of the intermediate section with an adjoining end at the upper section and an opposite end of the intermediate section with an adjoining end of the lower section. The joint means comprises a male portion having a ridge provided with a circumferential groove for receiving a seal means and an associated female portion having an inside diameter greater than that of the ridge for receiving said male portion and a seal means.

Abstract: A pressure control system for a pressurized water nuclear reactor and method for quickly closing the valves associated with the pressurizer thereof has a temperature detection device on the loop seal of each valve and a valve responsive thereto to change water to the loop seal upon a temperature rise therein and stop the flow of water to the loop seal upon a temperature drop therein. The rapid formation of water seals in the loop seals for the valves protects the valve seats from wear and degradation and prolongs the life thereof.

Abstract: A fuel assembly in a nuclear reactor has a spectral shift apparatus including a plurality of displacer rods for controlling reactivity in the assembly and an apparatus for refurbishing the displacer rods for reuse. Each displacer rod contains a quantity of water equivalent to a small fraction of the rod volume. Also, the spectral shift apparatus includes a manifold with a central plenum and a rupturable disk connected to the manifold. The manifold is connected in flow communication with the displacer rods. The disk which seals the displacer rods as well as the manifold plenum is rupturable at a given pressure differential thereacross so as to allow entry of the moderator/coolant liquid into the manifold and rods. Also, a screen adjacent the disk restricts it to rupturing in one direction only.

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: An electrical penetrator employs metal-sheathed insulated conductors that extend completely through and are sealed within a tubular housing. A filler block is disposed centrally within the housing and is surrounded by elastomeric material of a sealing member. Plugs are inserted into opposite ends of the housing so as to compress the elastomeric material and are sealed within the housing. Hollow end caps threaded into the opposite ends of the housing urge the plugs toward the elastomeric material. The metal-sheathed conductors extend through the hollow end caps and through longitudinal passages in the plugs and the sealing member. The conductors are sealed in the sealing member by the elastomeric material, are sealed in the plugs by tube fitting assemblies threaded into the plugs about the conductors, and are sealed in the hollow end caps by potting material.

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: 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 device for use in a nuclear reactor which includes a pressure vessel having a vessel head, a core in the vessel, elements for controlling the reactivity of the core, drive rods which pass through the vessel head for displacing the elements, and a plurality of head adapters which pass through the vessel head, each head adapter forming part of a drive rod housing enclosing a respective drive rod, each housing enclosing a region which communicates with the interior of the vessel and which is closed at the top. The drive is associated with a respective housing and constitutes a housing extension including a component for connecting the device to the head adapter forming part of the respective housing, and a component for forming, around the associated drive rod and within the associated housing, a fluid passage having a cross-sectional area not exceeding a selected value at least upon the occurrence of a leak in the respective housing.

Abstract: Apparatus comprising a seal connector is disclosed for sealingly connecting flow channels in the core support plate with flow channels in fuel assemblies for use in a spectral shift pressurized water nuclear reactor. Spectral shift is obtained by displacing a portion of the light water in the core with deuterium oxide or a combination of deuterium oxide and light water or various gases such as helium during the initial state of reactor operation to harden the nuclear spectrum and thereby reduce excess reactivity and increase the production of fissile materials. The seal connectors provide a sealed flow channel for introducing the deuterium oxide into the core during the early stages of reactor operation and for reintroducing the light water into the core during the later stages of reactor operation.

Abstract: A method of and apparatus for melting radioactive waste contained in a metal transport vessel and in which the transport vessel is introduced into a container which is closed by a laterally retractable cover and then inverted by rotation through 180.degree. about a horizontal axis to lie above the mouth of a furnace. The mouth of the furnace is provided with a horizontally retractable slider and the cover and the slider are independently retracted to allow discharge of the transport vessel and the radioactive waste contents thereof into the furnace for melting therein. The container and its cover thus form part of the gate allowing transfer of the radioactive waste into the furnace without a hot or radioactive cell shielding the entire unit from vagabond or wayward radioactivity.

Abstract: The invention relates to a device for connecting a cylindrical or tubular submersible element to a tubular sleeve, inter alia a submersible heating element to the sleeve of a pressurizer basin, comprising a first flange associated with the sleeve, a second flange associated with the submersible element, a resilient metal joint interposed between the two flanges, two screwthreaded tubular members, one male, the other female, which cooperate with one another via their threads, the threaded male member acting on the first flange via the agency of two half-rings, the female screwthreaded member acting on the second flange, the screwing of the two screwthreaded tubular members causing the compression of the joint.

Abstract: A closure for an inclined duct having an open upper end and defining downwardly extending passageway. The closure includes a cap for sealing engagement with the open upper end of the duct. Associated with the cap are an array of vertically aligned plug members, each of which has a cross-sectional area substantially conforming to the cross-sectional area of the passageway at least adjacent the upper end of the passageway. The plug members are interconnected in a manner to provide for free movement only in the plane in which the duct is inclined. The uppermost plug member is attached to the cap means and the cap means is in turn connected to a hoist means which is located directly over the open end of the duct.

Abstract: A steam control value for a steam chest such as used in a nuclear plant with an improved muffler portion. The muffler portion includes window openings of predetermined dimensions. A ring portion is below the window opening having a plurality of pockets. Each pocket is aligned with one of the window openings. This design greatly reduces vibrations which may damage the valve.

Abstract: A sealoff device and method are disclosed for controlling the level of a fluid within first and second confined regions which are arranged in fluid communication with one another. In the preferred embodiment, the invention permits shielding of the tube bundle contained within the wrapper of a nuclear steam generator while controlling the level of the working fluid within the surrounding annular downcomer passage. A sealoff device constructed of a flexible hollow tube is provided in sealing engagement between the wrapper and outer shell forming the downcomer passage to provide a substantially fluid-tight seal thereat. The sealoff device permits the maintaining of a high water level inside the wrapper to shield the tube bundle which is emitting nuclear radiation while maintaining a low water level within the downcomer passage to permit greater accessibility for repair and maintenance of the steam generator in a dry environment and to permit greatly increased working time in a greatly reduced radiation field.

Abstract: A core barrel hole plug. A plug body sized to easily fit the hole to be plugged is slidably attached to a flange sized larger than the hole to limit the movement of the plug body into the hole. A rectangular bore at the inner end of the plug body has a pair of pawls pivotally mounted therein which are moveable between retracted and extended positions for releasing or locking the plug in position. An actuator screw is threadably engaged through a cylindrical bore in the plug body and in communication with the rectangular bore where a cam on the actuator screw causes movement of the pawls between the release and locking positions. The flange and screw are adapted to receive a remotely operated tool for remote operation of the assembly.

Abstract: A method and apparatus for extending the life of a core of a water moderated nuclear reactor by spectral shift comprising the displacement of a portion of the moderator in the core by a gas having a low neutron cross-section during the initial stage of the life of the core and displacing the gas and replacing it with moderator during the latter part of the life of the core.

Abstract: An emergency transfer tube closure for a nuclear reactor well comprising an elongated, vertically-extending, U-shaped guide laterally disposed on each side of the transfer tube, a closure plate vertically disposed between the guides having rollers thereon riding within the guides permitting movement of the closure plate downwardly into sealing engagement with the transfer tube under emergency conditions.

Abstract: A repair fixture for water-cooled nuclear reactors including an openable reactor pressure vessel having a wall, and conduits passing through the pressure vessel wall for flooding the pressure vessel, includes a sealing box disposed in the opened, flooded pressure vessel, a device connected to the sealing box for pressing the sealing box liquid-tightly against the pressure vessel wall enclosing at least some of the conduits, and a device connected to the sealing box for evacuating the conduits enclosed by the sealing box.

Abstract: A retaining assembly holds a nozzle seal in the nozzle of a nuclear steam generator vessel. The assembly includes two arcuate beams generally following the curvature of the vessel wall, one beam lying generally alongside the divider plate and the other extending diametrically across the nozzle seal and being coupled thereto. The outer ends of the beams are anchored to the outer edge of the tube sheet and have brace members which bear against the vessel wall. The inner walls of the beams are interconnected by a thrust assembly which bears against the divider plate and includes an adjustable jacking screw means for urging the beams against the tube sheet. The effective length of the beam coupled to the nozzle seal can be varied by selectively replaceable spacers.