Abstract: A replacement thermal sleeve with a flange for a reactor vessel closure head penetration adapter housing. By altering a diameter of the flange, a replacement thermal sleeve can be installed through the narrow diameter of the penetration adapter housing opening from under the reactor vessel head. The flange can be compressible or expandable or the tubular wall of the thermal sleeve can be inserted in longitudinal sections, one at a time, into an opening in the underside of the penetration head adapter and reformed within the opening when fully inserted.

Abstract: Described herein is a clamp for repairing a site of at least one damaged nozzle on a pipe for carrying liquid, such as a sparger nozzle in a header pipe in a boiling water reactor of a nuclear power plant. The clamp in general includes a housing configured for mounting over the site on a surface the pipe, wherein the housing has a front, sides, top, and back. The housing may include an opening, or the clamp may include an orifice plate having an opening and being positioned on the front side of the housing such that liquid exiting the pipe flows through one or both the opening in the housing and opening in the orifice plate. The clamp also includes a bottom surface which, together with the housing and orifice plate, when included, defines an interior chamber. The bottom plate has an opening for alignment, upon installation, with the site, and at least one member, for example, wedges for securing one of the damaged nozzle or support rings for stabilizing a replacement nozzle in position within the housing.

Abstract: A support clamp assembly for mechanically securing a thermal sleeve to an elbow conduit in a jet pump of a nuclear reactor vessel, the support clamp assembly including: a tension shaft having a first end extendable through an opening in a sidewall of the elbow conduit and an opposite end with a head; a cruciform assembly having a base with an opening to receive the tension shaft and to abut the head of the shaft, wherein the cruciform assembly seats in the thermal sleeve; a boss slidable over the first end of the tension shaft and having a curved surface seating an outside surface of the elbow conduit, and a coupling device engaging the first end of the tension shaft and abutting the boss, wherein the coupling device places the tension shaft under tension to secure the cruciform assembly to the thermal sleeve and the boss to the elbow conduit.

Abstract: A tertiary shutdown system for a liquid metal reactor that eliminates the need for considering an ATWS in setting the thermal power limits of the reactor. The shutdown system includes a reservoir of neutron absorber material that is sealed by a valve that may actively dispense the absorber upon operator command, into a stagnant pool of sodium in the core that is confined to prevent the absorber material from entering the coolant flowing through the core. Additionally, the valve may be passively open to release the absorber material into the stagnant pool of sodium when the temperature at the valve exceeds a predetermined limit.

Abstract: Disclosed is a method for removing a thermal sleeve from a cold leg of a reactor coolant system, which enables removal of an unintentionally separated thermal sleeve without implementation of a pipe cutting operation, preventing invasion of impurities into pipes and securing reliability in repetitious welding of the pipes. In particular, the method enables a remote operation and an underwater operation using wire ropes, thus being capable of minimizing a negative effect on workers due to radiation exposure.

Abstract: Disclosed is an apparatus for removing a thermal sleeve from a cold leg of a reactor coolant system, which removes an unintentionally separated thermal sleeve without pipe cutting, preventing invasion of impurities into pipes and achieving reliable pipe re-welding. The apparatus includes a sleeve removal tool including a corn head formed at a shaft, a pressure plate below the corn head to maximize hydraulic pressure inside a safety injection pipe, a spring connected to the pressure plate to keep the pressure plate unfolded, and a guide wheel to guide the sleeve removal tool into the safety injection pipe, a horizontal movement carrier including bodies connected to each other by a link, a seating rod for seating of the sleeve removal tool, and moving wheels for movement of the horizontal movement carrier, and a vertical movement carrier including first and second anti-separation bars to prevent separation of the horizontal movement carrier.

Abstract: Example embodiments are directed to core spray sparger T-box repairs, specifically, to universal core spray sparger T-box weldless clamps having remote-friendly operation and methods of using universal core spray sparger T-box weldless clamps. Example embodiment clamps may be secured without welding to a variety of upper and lower sparger T-box configurations. Example embodiment clamps may be configured to simultaneously engage a sparger T-box in multiple dimensions to allow a universal fit. Further, example embodiment clamps may be accessed, installed, or removed by interacting only with a front side of the example embodiment clamps, thus potentially reducing difficulty and cost in remote access repairs to example clamps.

Abstract: A core spray sparger T-box attachment assembly for a nuclear reactor pressure vessel, wherein the pressure vessel includes a shroud, a sparger T-box penetrating the shroud, a plurality of sparger distribution header pipes coupled to the sparger T-box, and a downcomer pipe. The sparger header pipes may include at least one sparger nozzle, and the sparger T-box attachment assembly may include a downcomer pipe coupling and a sparger T-box clamp. The sparger T-box clamp may include an anchor plate having a draw bolt opening to receive a draw bolt, a first clamp block substantially aligned at one end of the anchor plate, and a second clamp block substantially aligned at the other end of the anchor plate.

Abstract: Marking of the cuts which have to be made, cutting of the section at two ends, removal of the section which has to be replaced, bevelling of the joint ends of the parts remaining after the section has been cut out from the pipe, adjustment of a new or replacement section for length and bevelling of its joining ends and positioning and narrow bevel welding of the ends joining the replacement section to the ends of the remaining parts of the pipe are performed outside the pipe. Within the pipe operations of machining and inspecting an internal part of the joining ends welded together are performed by remote control in a programmed way by introducing and positioning means for working within the pipe from a component of the primary circuit.

Abstract: In a method for sealing a hollow, elongate member within a reactor pressure vessel of a nuclear reactor, a section of the elongate member may be removed to separate the elongate member into an upper portion and a lower portion with an opening there between. The lower portion may be attached to a surface of the reactor pressure vessel in-situ, so as to seal off a potential leakage path through the elongate member.

Abstract: A core spray T-box attachment assembly for a core spray nozzle includes a primary cruciform wedge and a secondary cruciform wedge in contact with the primary cruciform wedge to form a cruciform wedge subassembly adapted for insertion within a bore of the core spray nozzle to sealingly engage an interior converging portion of a safe end of the core spray nozzle. The assembly includes a spider in contact with the cruciform wedge subassembly, and a draw bolt engaging an axial bore of a center portion of the cruciform wedge subassembly and the spider to the T-box.

Abstract: Marking of the cuts which have to be made, cutting of the section at two ends, removal of the section which has to be replaced, bevelling of the joint ends of the parts remaining after the section has been cut out from the pipe, adjustment of a new or replacement section for length and bevelling of its joining ends and positioning and narrow bevel welding of the ends joining the replacement section to the ends of the remaining parts of the pipe are performed outside the pipe. Within the pipe operations of machining and inspecting an internal part of the joining ends welded together are performed by remote control in a programmed way by introducing and positioning means for working within the pipe from a component of the primary circuit.

Abstract: The method facilitates sealing a control rod drive (CRD) housing to a stub tube in a reactor pressure vessel of a nuclear reactor, if any cracks develop proximate a heat affected zone of the stub tube at a CRD housing re-attachment weld. The method includes cutting the CRD housing to separate an upper portion of the CRD housing from a lower portion of the CRD housing. The lower portion remains in place and in substantial alignment with the upper portion of the CRD housing. A lower portion member, which may be the lower portion that was cut, is re-attached to the reactor vessel by a re-attachment weld at a location below potential differential leakage paths along the CRD housing. The heat affected zone (e.g., at the re-attachment weld) is covered with a corrosion resistant material to prevent future leaking, and to protect the weld from inter-granular stress corrosion cracking (IGSCC).

Abstract: A T-box assembly includes a T-box housing, a thermal sleeve coupled to the T-box housing, a cruciform wedge, a spider threadedly engaging the thermal sleeve, and a draw bolt coupling the cruciform wedge and the spider. At least one spring washer is located between the end of the thermal sleeve and the end of a core spray nozzle safe end. The T-box housing includes a cover opening having a plurality of breach lock lugs extending into the cover opening. A T-box cover plate includes a head portion and an insertion portion. A plurality of breach lock lugs extend from the periphery of the insertion portion. A plurality of ratchet teeth extend around the periphery of the head portion. A lock spring includes an engagement portion having a plurality of ratchet teeth sized to mesh with cover plate ratchet teeth.

Abstract: A T-box/thermal sleeve assembly replaces a damaged T-box/thermal sleeve in a core spray nozzle of a nuclear reactor. To replace the parts, the T-box and a portion of the extant thermal sleeve are removed from a location within the reactor vessel wall. The end of the thermal sleeve remnant is smoothed and a groove is formed along its interior surface. A replacement T-box/thermal sleeve and collet assembly are inserted into the nozzle bore from the interior of the vessel wall. The collet has axially projecting fingers with radial flanges for engaging in the groove to form a mechanical connection between the thermal sleeve remnant and the T-box/thermal sleeve replacement. A Belleville spring washer is interposed between the assembly and thermal sleeve remnant to place both parts in compression. A retention sleeve is screwthreaded within the replacement thermal sleeve to lock the fingers from radial movement.

Abstract: A T-box assembly to facilitate attaching a core spray line to a reactor core spray nozzle safe end without welding is described. In one embodiment, the T-box assembly includes a T-box housing, a cruciform wedge, and a draw bolt. The T-box housing is configured to be positioned so that a first end is located inside a core spray nozzle and engages the core spray nozzle safe end. Two other ends are configured to be in substantial alignment and configured to couple to core spray line header pipes. The T-box housing also includes a cover opening configured to receive a T-box cover plate. The T-box cover plate includes a draw bolt opening configured to receive the draw bolt. The first end of the T-box also includes a plurality of positioning lugs configured to engage the core spray nozzle to center the T-box housing in the nozzle bore. The cruciform wedge includes four web members extending from a central member and configured so as to form an X shaped configuration.

Abstract: A spacer for maintaining a pressure tube in spaced relation with a caland tube of a nuclear reactor. The spacer comprising a split ring adapted to be disposed about the outer surface of said pressure tube. The ring has a central annular body portion with a raised bearing surface thereon adapted to contact the inner surface of said calandria tube and prevent contact between said outer surface and said inner surface. An annular land projecting from each side of said central body portion is adapted to receive a collar thereon effective create an interference fit between said ring and said pressure tube and thereby constrain axial movement of said spacer on said pressure tube. The spacer of the present invention maintains its location on the pressure tube and does not suffer the axial movement which characterizes some conventional spacers. The bearing surface can have a coating to reduce wear and heat transfer.

Abstract: A method for sealing cracks adjacent stub tube attachment welds in a reactor pressure vessel of a nuclear reactor is described. The reactor pressure vessel includes at least one stub tube through which a control rod housing extends. The control rod housing is attached to one end of the stub tube with an upper stub tube attachment weld. A sidewall of a control rod drive housing is cut at a location below the upper stub tube attachment weld to separate an upper portion of the control rod housing from a lower portion of the control rod housing. The lower portion of the control rod drive housing is removed from the bottom head opening, and a replacement lower portion is positioned in the bottom head opening proximate to the remaining upper portion. The replacement lower portion then is secured to the reactor pressure vessel without securing the replacement lower portion to the remaining upper portion of the control rod drive housing.

Abstract: A protective sleeve includes an outer member and an inner member slidable within the outer member. The outer member has a tubular portion with a first end and a second end, and an attachment assembly is located at the first end of the tubular portion. The outer member further includes a plurality of spring plungers secured to an inner wall of the outer member. The attachment assembly includes a collar and a drip skirt secured to the collar. The attachment assembly is threadedly engaged to the first end of the outer member tubular portion. The inner member includes a first end positioned within the outer member and a second end. At least a portion of the inner member extends from the second end of the outer member. The inner member is movable relative to the outer member. A plurality of spring plungers are secured to an outer wall of the inner member. The spring plungers extend between the outer member and the inner member.

Abstract: A tight crossing to ensure a high efficiency seal between the interior (1) and the exterior (2) of a high activity cell. The crossing comprises a sleeve (6) placed in the wall (3), a guide tube (11) placed within the sleeve (6) and a support flange (12) placed between the sleeve (6) and the guide tube (11) on its outer end. A joint holder flange or ring (15) is placed in the cell interior (1) and is secured against the cell skin (4), the guide tube (11) and the sleeve (6) by means of captive bolts (18).

Abstract: The present invention relates to a miniaturized nuclear utilizing improved pressure tube structural members. More particularly, the present invention relates to a new miniaturized nuclear reactor utilizing novel structural members that are used to support the loads and stresses of multiple nuclear reactor fuel channel pressure tubes and calandria tubes in a moderator.

Abstract: A method and apparatus for repairing nuclear reactor core shrouds includes applying vertical compressive forces to the shroud in situ to urge opposed ends of the shroud toward one another using a plurality of tie-rods, each including a plurality of coaxial longitudinal members separated by a radial gap filled with reactor coolant or some other damping fluid. One of the longitudinal members is secured to upper and lower portions of the shroud for maintaining a sufficient preload to hold the shroud together and is coupled with one or more other longitudinal members in a manner to transmit axial loads thereto upon extending a predetermined axial distance. A plurality of radial spacers can also be positioned at longitudinally spaced locations along the length of the tie-rod to assure control rod insertion by limiting lateral movement of the shroud and can reduce the preload required for preventing the formation of new cracks and stabilizing existing cracks.

Abstract: A nuclear reactor having a pressure vessel which is open at the top. The open top of the pressure vessel is closed by a steel dome. A containment, which is open at the top, extends upward from and is joined to the top of the pressure vessel and has an open containment head at the top thereof. The open top of the containment is closed by a steel dome, thereby forming a containment well bounded laterally by the containment, on the bottom by the vessel closure and on the top by the containment closure. The pressure vessel can be a steel-lined prestressed concrete vessel, while the containment is formed by an extension of the prestressed concrete vessel. Alternatively, the pressure vessel and the containment are parts of a unitary steel vessel. Isolation valves are installed on each penetration pipeline to isolate the system in the event of a loss-of-coolant accident.

Abstract: A supercritical water oxidation reactor includes a vessel with an interior urface, two cooling sections, a heat exchanger, an oxygenating section, a pump, and a trap. The interior surface of the vessel has a corrosion-resistant, artificial ceramic or diamond-like coating. The artificial diamond coating is thin and crystal-like in structure. The heat exchanger is located between the two cooling sections. The heat exchanger and the two cooling sections surround the exterior of the vessel. The oxygenating section comprises a porous cylindrical baffle positioned within the vessel. The porous baffle transfers oxygen, hydrogen peroxide, or other oxygenating substances to an aqueous hazardous waste introduced into the reactor.In accordance with another aspect of the invention, the oxygenating section includes a shaft having a helical extension. The shaft has a corrosion-resistant, artificial diamond or diamond-like coating on its outer surface.

Abstract: In order to provide a relatively inexpensive water-tight telescopic enclosure which can extend automatically upon demand, a tubular extension piece is reciprocally mounted on a container-like hook box structure. A tube seal which interconnects the hook box and the tubular extension provides a watertight connection between the two members and also provides an air space in a folded portion in which air can collect and produce buoyancy as the hook box is lowered into water. The tubular extension also has a larger cross-sectional area than the hook box and thus produces additional buoyancy. When the hook box is lowered into water the extension piece automatically floats upwardly to prevent the intrusion of water into the interior of the hook box and thus prevent contamination of pieces of apparatus enclosed therein.

Abstract: A nuclear reactor and emergency core cooling system. A nuclear reactor is provided with a cylinder around the core barrel that defines an annular channel therebetween. An injection nozzle is provided through the reactor vessel for delivery of emergency coolant to the defined channel. Emergency coolant is supplied during a LOCA to the injection nozzles sequentially from a high pressure tank, a low pressure tank, gravity feed tanks inside the reactor building, and from sumps that collect coolant in the reactor building. Check valves in the upper portion of the cylinder vent steam to the reactor inlet lines during a LOCA. Bores around the upper circumference of the cylinder break any siphoning action that might occur at the injection nozzle if there is a break in the emergency coolant lines from the emergency coolant sources.

Abstract: Vibration dampener for dampening vibration of a tubular member, such as an instrumentation tube of the type found in nuclear reactor pressure vessels. The instrumentation tube is received in an outer tubular member, such as a guide thimble tube. The vibration dampener comprises an annular sleeve which is attachable to the inside surface of the guide thimble tube and which is sized to surround the instrumentation tube. Dimples are attached to the interior wall of the sleeve for radially supporting the instrumentation tube. The wall of the sleeve has a flexible spring member, which is formed from the wall, disposed opposite the dimples for biasing the instrumentation tube into abutment with the dimples. Flow-induced vibration of the instrumentation tube will cause it to move out of contact with the dimples and further engage the spring member, which will flex a predetermined amount and exert a reactive force against the instrumentation tube to restrain its movement.

Abstract: Upper internals for a nuclear reactor comprise an upper core plate and a plate which supports cluster guides tubes connecting the two plates together. The cluster guides project above the support plate. A bottom wall of the support plate is situated at a level just higher than the outlet nozzles of the reactor vessel and each guide is supported by the bottom wall of the support plate by abutment of a shoulder formed in a passage of the bottom wall, in the lower half thereof.

Abstract: An instrument thimble tube shroud is disclosed which has a central cup surrounding an instrument thimble tube to prevent fluid flow about the thimble tube from causing excessive vibration and wear. A plurality of arms extend radially from the cup and have locking pads disposed at the end of each arm, springs extending from the pads engaging recesses in an adjacent fuel assembly nozzle to lock the shroud in position and prevent movement of the shroud or rotation due to aggressive fluid flow. Utilizing the inventive shroud prevents vibration and damage to the instrument thimble tube passing therethrough, enhancing life of the instrumentation and allowing continued observation of dynamics within a nuclear reactor.

Abstract: A process for improving nozzles extending substantially vertically through openings in the head of a nuclear reactor and which are circumferentially welded to the head through a weld lying on an inner surface of the head and on the adjacent outer surface of the nozzle which comprises forming a coaxial, circumferential groove upwardly into at least a portion of the nozzle extending into the reactor and then filling the coaxial, circumferential groove with a weld material. The nuclear reactor head is also claimed.

Abstract: A watertight cover for the hook, hook block and cables of a crane comprises a hook box, of a size to receive the hook, fixed to a first cover member, which is of a size to receive the hook block. A second cover member is telescopically carried on the first cover member. Remotely controlled means are provided for displacing the second cover, relative to the first cover, as the hook is lowered into the water.

Abstract: In order to supply emergency coolant directly to the core inlet of a nuclear reactor, a separate and distinct channel is located within the reactor vessel. This channel flows downward along the perimeter of the core barrel and discharges its emergency coolant directly to the core inlet. Separate nozzles couple this channel to the supply of emergency coolant.

Abstract: A replacement heater sleeve for nuclear reactor coolant system pressurizer and method for replacing a damaged original heater nozzle. The original heater and heater nozzle are removed from the pressurizer and the original bore is enlarged. An outer sleeve is installed in the enlarged bore on the same center as the original heater nozzle and is substantially flush with the interior of the pressurizer. The outer sleeve is welded to the pressurizer on its interior and exterior surfaces. An inner sleeve is installed in the inner diameter of the outer sleeve and extends beyond the outer sleeve into the pressurizer. The inner sleeve is welded to the lower end of the outer sleeve and is provided with an inner diameter sized to receive a heater of the same size as that originally installed in the pressurizer. The inner sleeve also maintains the original heater alignment in the pressurizer.

Abstract: A cylindrical coffer dam assembly is described for use in temporary shielding personnel from nuclear reactor stored internals' radiation. The coffer dam is made up of substantially equal segments small enough to pass through the equipment hatch of the reactor containment building. The segments are pre-fabricated at a factory, transported to the plant, introduced individually into the containment building, and assembled together in sealing relation at the operating floor into a complete coffer dam. The coffer dam is moved to the reactor vessel and connected to the reactor vessel upper flange in sealing relation. The coffer dam can be disconnected, disassembled, removed and re-used at other nuclear reactors.

Abstract: A hydro-ball in-core instrumentation system employs detector strings each comprising a wire having radiation sensitive balls affixed diametrically at spaced positions therealong and opposite tip ends of which are transportable by fluid drag through interior passageways through which primary coolant is caused to flow selectively in first and second opposite directions for transporting the detector strings from stored positions in an exterior chamber to inserted positions within the instrumentation thimbles of the fuel rod assemblies of a pressure vessel, and for return. The coolant pressure within the detector passageways is the same as that within the vessel; face contact, disconnectable joints between sections of the interior passageways within the vessel facilitate assembly and disassembly of the vessel for refueling and routine maintenance operations.

Abstract: A wear-reduction-sleeve for in-core-instrumentation thimbles of a pressurized water nuclear reactor having bottom mounted instrumentation to curtail flow induced excitation and increase support contact area in the region of thimble length which extends through and defines an annulus with the core support plate and extends upwardly to and through the fuel assembly flow distribution plates. The wear-reduction-sleeve includes a hollow shank portion which gives a low wear coefficient when in contact with the chrome-plated thimble and is inserted into the annulus and below where it is radially expanded and secured to a thimble guide tube. An upper portion of the wear-reduction-sleeve between the core support plate and flow distribution plate has a flow collection chamber and radial flow exit slots which divert thimble flow substantially away from the hole in the fuel assembly flow distribution plate through which the thimble extends.

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: A wear-reduction-shield (40) for use between the core plate (24) and lower end fitting (26) of a pressurized water reactor (10) to reduce excessive wear of in-core-instrumentation thimbles (30) due to flow induced vibrations and resist fuel assembly tipping has a cylindrical body portion 42with core plate engaging lower end surface (44). At the opposite and upper end, a tapered internal end wall (46) assists upward threading of the monitor and cable. On the outside of the upper end symmetrical leg portions (52) and central land (54) surround a thimble (30) receiving opening (48). Smoothly tapering outer surface (56) minimizes turbulence in and beyond opening (34) in lower end fitting (26). Internal dimensions of shield (40) avoid structure such as sleeve (50) which may be present.

Abstract: Multi-layer compensator with spacers arranged between the layers and with the spacers having the shape of flat strips distributed parallel to the longitudinal axis of the compensator over the circumference, with a gap between spacers.

Abstract: A feedwater sparger assembly, and more particularly a thermal sleeve device, to prevent relatively cold feedwater from contacting the vulnerable surfaces of a feedwater nozzle in a boiling water nuclear reactor. Inner and outer concentric tubular thermal sleeve members (42,56) span the distance between the sparger (12) and a substantially cylindrical transition surface (34) machined into the feedwater nozzle (14) or pipe (22). At the first ends (46,64) of the tubular members, adjacent the transition surface (34), a packing means (50), is deformed against the transition surface (34). The second ends (60,62) of the tubular members are operatively connected to the sparger (12). One of the tubular members (42,56) is rigidly connected to the sparger (12) and the other tubular member is mounted on the sparger such that it can be longitudinally moved relative to the rigidly connected member.

Abstract: A joint between a pair of coaxial tubes which extend into a pressure vessel from a surface is sealed using a sleeve-like housing which surrounds the joint to be sealed. An upper fluid-tight seal is formed between the longer of the tubes and the housing. A lower fluid-tight seal is formed between the housing and the surface. An intermediate seal is also formed between the housing and the shorter tube. The upper and lower seals are independently preloaded through the use of spring washers. Primary loading of the lower seal to the surface is caused by fluid pressure in the vessel which acts on the housing.

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 nuclear power plant includes a concrete biological shield, a metallic reactor pressure vessel surrounded by the concrete biological shield, coolant connector pieces connected to the reactor pressure vessel, coolant lines connected to the coolant connector piece, and a support engaging the coolant connector pieces and holding the reactor pressure vessel. The support includes at least one supporting tube surrounding one of the coolant connector pieces, the supporting tube having an inner surface anchored on the one coolant connector piece and an outer surface anchored on the biological shield.

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: A multiple shell pressure vessel utilizes a number of spaced apart, concentrically disposed pressure vessel shells within and spaced apart from an outer pressure vessel shell, the spaces between each shell being filled with a low melting point, high boiling point material selected from the group, lead, tin, antimony, bismuth, or sodium and potassium, and mixtures thereof and subjected to a pressure whereby the innermost pressure vessel shell wall is maintained in compression while the main vessel is pressurized. Chemical compositions or compounds which contain boron or cadmium may also be added to the filler material. The vessel may include devices for keeping the pressure in the space between the innermost pressure vessel shell and the next innermost shell at a fixed predetermined multiple of the pressure within the innermost pressure vessel shell.

Abstract: In the device, over at least a portion of the length of the internal guide passage (5) of the tubular conduit (15) extends a retaining tube (16) exhibiting radial undulations (17) such that the cylinder having straight generatrices which is inscribed in the tube (16) corresponding to the free passage in a straight line, within this tube, has a diameter less than the diameter of the tubular conduit (15). In the case of a pressurized water nuclear reactor, the retaining tube (16) is preferably placed, at least in part, within the lower core plate (2).

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: A pipe loop arrangement for the closed primary system of a nuclear reactor. The heated reactor coolant flows through a horizontally positioned hot leg pipe while the return flow cooled reactor coolant flows through a cold leg pipe concentrically mounted within the hot leg pipe. A bell-mounted suction port and the high pressure discharge port of the reactor coolant pump are located within an outlet chamber with the steam generator. A transition piece slip fitted to an opening within the reactor vessel outlet flange connects the cold leg pipe to the inlet to the nuclear core. A flow shroud surrounding the pump discharge connects the pump discharge to the cold leg pipe, forms a volute for the pump discharge and separates the outlet chamber from the inlet chamber of the steam generator.

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: Piping of a nuclear reactor containment vessel comprises pipes passing through the containment vessel and, extending to the outside of the containment vessel, outer shut-off valves each provided at a portion of the pipe which is located at the outside of the containment vessel for closing the pipe and isolating vessels for covering at least outer surfaces of welded portions of the pipes each being located between an outer wall surface of the containment vessel and a portion including the outer shut-off valve and for isolating the covered portions of the pipes from atmosphere.