Abstract: A method for heating primary coolant in a nuclear reactor system during system start-up. A primary coolant loop fluidly couples together a reactor vessel and a steam generating vessel. The primary coolant loop is filled with primary coolant. A portion of the primary coolant is taken from the primary coolant loop and placed into a start-up sub-system. The portion is heated while in the sub-system to form a heated portion of the primary coolant. The heated portion is returned into the primary coolant loop. The method allows for the primary coolant to be heated to a no-load operating temperature.

Abstract: A nuclear reactor is designed to couple the load path of control elements with the reactor core, thus reducing opportunity for differential movement between the control elements and the reactor core. A core barrel can be fabricated in a manufacturing facility to include the reactor core, control element supports, and control element drive system. The core barrel can be mounted to a reactor vessel head. Movement, such as through seismic forces, transmits an equal direction and magnitude to the control elements and the reactor core, thus inhibiting the opportunity for differential movement.

Abstract: A nuclear reactor is designed to couple the load path of the control elements with the reactor core, thus reducing the opportunity for differential movement between the control elements and the reactor core. A cartridge core barrel can be fabricated in a manufacturing facility to include the reactor core, control element supports, and control element drive system. The cartridge core barrel can be mounted to a reactor vessel head, and any movement, such as through seismic forces, transmits an equal direction and magnitude to the control elements and the reactor core, thus inhibiting the opportunity for differential movement.

Abstract: The present invention relates to a connecting apparatus for a steam generator disposed between a steam generator and a flow mixing header to fasten the steam generator to the flow mixing header in a sealed manner, and an integral reactor including the same. Fastening the steam generator to the flow mixing header in a sealing manner includes: a base plate mounted on the flow mixing header having a through hole formed at the center thereof; and a steam generator connecting portion protruding along the circumference of the through hole in the base plate allowing an outlet of the steam generator to be inserted and fastened thereto. Since the connection for the steam generator is tightly fastened to the flow mixing header, leakage of a coolant therebetween is prevented, and since the steam generator is horizontally disposed in the flow mixing header, structural stabilization may be achieved.

Abstract: A nuclear island includes a nuclear reactor, a lateral seismic restraint, and a reactor core retention cooling system. The lateral seismic restraint includes a vertically oriented pin attached to one of the bottom of the lower vessel head and the floor underneath the nuclear reactor, and a mating pin socket is attached to the other of the bottom of the lower vessel head and the floor. The reactor core retention cooling system includes one or more baffles, optionally thermally insulating material, disposed alongside the exterior surface of a lower portion of the reactor pressure vessel including at least the lower vessel head. A plenum is defined between the one or more baffles and the exterior surface of a lower portion of the reactor pressure vessel. The one or more baffles may define a lower plenum inlet surrounding the lateral seismic restraint.

Abstract: A nuclear steam supply system includes an elongated reactor vessel having an internal cavity with a central axis, a reactor core having nuclear fuel disposed within the internal cavity, and a steam generating vessel having at least one heat exchanger section, the steam generating vessel being fluidicly coupled to the reactor vessel. The reactor vessel includes a shell having an upper flange portion and a head having a head flange portion. The upper flange portion is coupled to the head flange portion, wherein the upper flange portion extends into the internal cavity, and the head flange portion extends outward from the internal cavity. The flanges have a space saving design which are configured to minimize outward extension from the cavity while still providing desired leak protection at the interface between the shell and the head.

Abstract: An alignment plate that is attached to a core barrel of a pressurized water reactor and fits within slots within a top plate of a lower core shroud and upper core plate to maintain lateral alignment of the reactor internals. The alignment plate is connected to the core barrel through two vertically-spaced dowel pins that extend from the outside surface of the core barrel through a reinforcement pad and into corresponding holes in the alignment plate. Additionally, threaded fasteners are inserted around the perimeter of the reinforcement pad and into the alignment plate to further secure the alignment plate to the core barrel. A fillet weld also is deposited around the perimeter of the reinforcement pad. To accommodate thermal growth between the alignment plate and the core barrel, a gap is left above, below and at both sides of one of the dowel pins in the alignment plate holes through which the dowel pins pass.

Abstract: A steam generator with a heating gas duct which in an approximately horizontal heating gas direction is exposed to throughflow of a heating medium is provided to ensure a reliable absorption of the mentioned loads, especially of the additional loads which are produced as a result of the design dependent internal pressure of the heating gas. The heating gas duct is enclosed by a plurality of support frames which are arranged one behind the other in the heating gas direction, wherein at least two of the support frames are interconnected via a plurality of horizontal batten plates.

Abstract: A nuclear reactor vessel structure includes an inner peripheral tube-shaped steel plate, an outer peripheral tube-shaped steel plate, and an intermediate tube-shaped steel plate disposed between the inner and outer peripheral tube-shaped steel plates, and is configured to support a nuclear reactor vessel on the inner peripheral side of a tube-shaped structure with concrete placed between the steel plates. The nuclear reactor vessel structure includes a support having a tube-shaped plate disposed on the inner peripheral side of the intermediate tube-shaped steel plate, and an annular plate which protrudes to the inner peripheral side of the tube-shaped plate and to which a connection section is affixed. The support is affixed to the concrete, which is placed between the inner peripheral and the intermediate tube-shaped steel plates, by first bar members, and the support is also affixed to the inner peripheral tube-shaped steel plate by second bar members.

Abstract: Provided is a sliding support and a system using the sliding support unit. The sliding support unit may include a fulcrum capture configured to attach to a support flange, a fulcrum support configured to attach to the fulcrum capture, and a baseplate block configured to support the fulcrum support. The system using the sliding support unit may include a pressure vessel, a pedestal bracket, and a plurality of sliding support units.

Abstract: A buckstay system is described comprising horizontal buckstays for the walls of a steam generator, for example in plural vertically space assemblies tied with vertical buckstays, in which a buckstay extends generally horizontally across each wall such as to form a connected pair with an adjacent buckstay at each corner; an elongate tie bar formation extends across each wall such as to form a fixedly mounted pair with an adjacent tie bar formation at each corner; an anchor assembly associated with each buckstay and providing engagement means by which each buckstay engages with a respective tie bar; and each horizontal buckstay is split to comprise at least two rigid elongate buckstay elements mounted together to be relatively slideable in a buckstay longitudinal direction.

Abstract: To provide a lower foundation 30 provided on a ground 7 and an upper foundation 31 provided above the lower foundation 30 via a seismic isolator 32. A machine room S in which a machine K can be arranged is provided in the upper foundation 31. A foundation-side hull structure unit that is configured in a reticular pattern by horizontal reinforcing ribs extended in one direction and vertical reinforcing ribs extended to cross the horizontal reinforcing ribs is provided in the upper foundation 31, and the machine room S is provided in a space in the foundation separated by the horizontal reinforcing ribs and the vertical reinforcing ribs.

Abstract: An embodiment of the present invention takes the form of an apparatus or system that may reduce the level of vibration experienced by an inlet riser or other similar object within a reactor pressure vessel. An embodiment of the present invention may eliminate the need for welding the riser brace to the inlet riser. An embodiment of the present invention provides at least one riser brace clamp that generally clamps the riser brace to the inlet riser. After installation, the riser brace clamp may lower the amplitude of, and/or change the frequency of, the vibration experienced by the inlet riser.

Abstract: Example embodiment damping devices may include a housing capturing a piston. The housing may be filled and/or able to be filled with a damping fluid compatible with the nuclear reactor coolant, so that a leak from the housing or coolant passing into the housing does not damage the reactor or example embodiment devices. Example embodiments may further include one or more springs that provide an elastic force opposing movement between the piston and housing. A shaft of the piston and an end of the housing may be connected to two nuclear reactor components with relative motion or vibration to be damped. Example methods may use example embodiment damping devices to reduce and/or prevent relative motion and vibration among components of a nuclear reactor.

Abstract: A nuclear reactor includes a reactor pressure vessel 12 and a core barrel 14, contained within the reactor pressure vessel 12. The reactor 10 further includes a single vertical support 16, for transmitting vertical load from the core barrel to the reactor pressure vessel. Further, lateral support means is provided at an elevation which is above that of the support 16 to provide lateral support to the core barrel 14. This arrangement will result in reduced stress arising from the temperature fluctuations.

Abstract: Provided is a sliding support and a system using the sliding support unit. The sliding support unit may include a fulcrum capture configured to attach to a support flange, a fulcrum support configured to attach to the fulcrum capture, and a baseplate block configured to support the fulcrum support. The system using the sliding support unit may include a pressure vessel, a pedestal bracket, and a plurality of sliding support units.

Abstract: A technical installation, especially a nuclear power plant, has a number of system components that are respectively supported by a number of beams, and a number of pressurized conduits. The technical installation is designed in such a way that secondary damage occurring in the surroundings of pressurized conduits are kept particularly low even if the pressurized conduits rupture. This is achieved in that at least one of the beams is embodied in a segmented manner in an area that is expected to be affected if a pressurized conduit ruptures, adjacent segments preferably being connected to each other via screw connections.

Abstract: Two transducers to be rotated around a circumferential location on a cylindrical body for structural testing of the body are carried on a mounting and drive apparatus including a magnetic attachment which can be manually brought up to a pipe from one side only for fixed connection to the pipe on that side at a position axially spaced from a weld. A collar shaped support for the pair of transducers is formed of a row of separate segments which wrap around the pipe from the one side and is rotated around the axis of the pipe to carry the transducer around the circumferential weld. The segments carry rollers to roll on the surface and are held against the pipe by magnets. The transducers are carried on the support in fixed angular position to track their position but in a manner which allows slight axial or radial movement relative to the pipe.

Abstract: A method is provided for removing radioactive internals structural members in the core of a reactor pressure vessel in a containment vessel. The method includes placing a first cask in a first internals assembly, detaching radioactive first internals structural members from second internals structural members in the first internals assembly, placing the detached first internals structural members in the first cask, placing the first internals assembly in a second cask, and removing the second cask containing the first internals assembly and containing the casked detached radioactive first internals members from the containment vessel. The first internal members may be radioactive baffle plates, and the second internals members may be former plates bolted to the radioactive baffle plates. Novel tooling, framework and fixtures facilitate disassembling, moving and storing the radioactive baffle plates.

Abstract: An alignment plate that is attached to a core barrel of a pressurized water reactor and fits within slots within a top plate of a lower core shroud and upper core plate to maintain lateral alignment of the reactor internals. The alignment plate is connected to the core barrel through two vertically-spaced dowel pins that extend from the outside surface of the core barrel through a reinforcement pad and into corresponding holes in the alignment plate. Additionally, threaded fasteners are inserted around the perimeter of the reinforcement pad and into the alignment plate to further secure the alignment plate to the core barrel. A fillet weld also is deposited around the perimeter of the reinforcement pad. To accommodate thermal growth between the alignment plate and the core barrel, a gap is left above, below and at both sides of one of the dowel pins in the alignment plate holes through which the dowel pins pass.

Abstract: A vertical spring wedge restores a tight fitup against an adjacent structure, such as between an inlet mixer and an adjacent restrainer bracket in a boiling water nuclear reactor jet pump. The vertical spring wedge includes a U-shaped bracket including a pair of guiding portions and a pair of bracket holes. A pair of wedge assemblies are coupled with the bracket, each of the wedge assemblies including a wedge segment attached to a spring-loaded guide rod. The guide rods are displaceable in the bracket holes between a retracted position and an extended position. The wedge segments engage the guiding portions, and a combination of the bracket and wedge assemblies have a first width when the guide rods are in the retracted position and have a second width wider than the first width when the guide rods are in the extended position.

Abstract: A clamp apparatus is provided which is designed to structurally replace a weld that attaches a riser brace assembly to a reactor pressure vessel wall, and a method for repairing the riser brace assembly. The riser brace assembly is designed to support a jet pump in the reactor pressure vessel. The riser brace assembly may include upper and lower riser brace leaves connected to a reactor pressure vessel pad on the wall. The clamp apparatus may include a first clamp component including a central extension portion, and a second clamp component including a slot portion. The central extension and slot portions may be engaged to provide alignment between the first and second clamp components between the upper and lower riser brace leaves of the riser brace assembly.

Abstract: A spacer for a fuel assembly for a light water nuclear reactor contains a plurality of intercrossed segments, which form a grid. The segments are formed from first and second metal strips which are assembled and provided with protruding parts or corrugations in such a way that the adjacent protruding parts are embodied in such a way that a flow component perpendicular to a vertical central plane which extends between the metal strips is applied to cold water running out from the flow sub-channel.

Abstract: The reactor vessel of a nuclear reactor installation which is suspended from the cold leg nozzles in a reactor cavity is provided with a lower thermal insulating barrier spaced from the reactor vessel that has a hemispherical lower section that increases in volume from the center line of the reactor to the outer extent of the diameter of tiie thermal insulating barrier and smoothly transitions up the side walls of the vessel. The space between the thermal insulating harrier and the reactor vessel forms a chamber which can be flooded with cooling water through passive valving to directly cool the reactor vessel in the event of a severe accident. The passive inlet valve for the cooling water includes a buoyant door that is normally maintained sealed under its own weight and floats open when the cavity is Hooded. Passively opening steam vents are also provided.

Abstract: A necessary size and number of modules each obtained by housing a member including heat exchanger tube panels each comprising a heat exchanger tube bundle and headers for the heat exchanger tube bundle, an upper casing of an exhaust heat recovery boiler (HRSG), provided above the heat exchanger tube panels, heat insulators, and heat exchanger tube panel support beams provided on the upper surface of the upper casing into a transportation frame, are prepared according to design specifications of the HRSG, and side casings and a bottom casing except for the ceiling part casing are constructed in advance at a construction site of the HRSG, and the modules are suspended from above between adjacent support beams of the ceiling part to dispose the heat exchanger tube panel support beams of the modules at the set heights of the ceiling part support beams, and the support beams and the ceiling part support beams are connected and fixed via connecting steel plates, whereby the respective modules are transported to the

Abstract: A core plate assembly for a nuclear reactor includes a plurality of support beams, a flat plate positioned on top of the support beams, a plurality of control rod guide tube openings arranged in staggered rows, and a plurality of fuel supports extending through the flat plate. Each guide tube opening has a cruciform shape defines four fuel bundle receiving areas. Each fuel support includes a coolant flow inlet, and a coolant flow outlet sized to receive a lower tie plate of a fuel bundle. The coolant flow inlet is offset from coolant flow outlet so that a centerline of the coolant flow inlet is parallel to a centerline of the coolant flow outlet. The coolant flow inlets are positioned adjacent a support beam, and the coolant flow outlets are positioned in a fuel bundle receiving area.

Abstract: The present invention is used to reduce thermal load itself, being the cause to generate stress, which develops near liquid surface in a nuclear reactor wall and to contribute to further improvement of safety. A partition member (5) is arranged above a coolant liquid surface (9) in an annulus space (3) between a reactor vessel (1) and a guard vessel (2), a low-temperature gas is circulated through the annulus space above the partition member to cool down, the gas is circulated through the annulus space from under the coolant liquid surface to the partition member, and the high-temperature gas heated under the coolant liquid surface is used to raise the temperature above the coolant liquid surface.

Abstract: A nuclear steam supply containment system employing prefabricated component supports that are surrounded by steel concrete forms and anchored to the floor liner of a nuclear containment. The prefabricated component supports extend through the concrete forms and a reinforce concrete slab cap to a support elevation for the component. A second inner steel concrete form can be employed to form an annular concrete channel through which the supports extend. The center of the inner form can be filled with a sand-like substance, radiation absorber material or concrete grout.

Abstract: An open-webbed cage support device providing support that enabling a mechanical device such as a thermal expansion tank to be suspended or mounted adjacent to the thermal water heating device without the need to improvise a “made in the field” support structure.

Abstract: A forged upper shroud section which may be machined from a single piece rectangular cross-section ring forging and includes a circular flange and a cylindrical shell is described. Openings and slots are machined into the flange to align and support the shroud head. A groove is machined along an inside surface of the cylinder section, and the groove may be used to support top guide grid (not shown). An end of the cylinder section is machined with a weld prep for attachment to the core section of the shroud.

Abstract: A nuclear power plant comprising a casing which encloses a primary space, a reactor vessel arranged in the primary space, and a reactor core provided in the reactor vessel. The plant further comprises an upper space provided above the casing. The reactor core is separated from the upper space by means of an openable cover arrangement. The casing is designed in such a manner that the primary space is completely closed against the environment to at least the level corresponding to the most highly located part of the reactor core. The upper space is arranged to house a volume of a liquid sufficiently large to permit the filling of the primary space with the liquid to a level located above the most highly located part of the reactor core.

Abstract: When carrying the large structure out through an aperture portion provided at a roof of a reactor building, a chamber for covering the aperture is provided at the roof so that work of providing the chamber for covering the aperture portion can be performed independent of other work performed in the reactor building, before at least a part of work of using a roof crane and at least a part work of handling fuel assemblies in the reactor building.

Abstract: An electrode discharge machining (EDM) apparatus for machining slots in a jet pump diffuser in a nuclear reactor pressure vessel is described. The apparatus is configured to machine a plurality of slots in the diffuser at positions behind the diffuser sensing line within the plane formed by the center of the diffuser and the sensing line. The apparatus includes a housing, a plurality of clamp assemblies, a hook assembly configured to engage the sensing line standoff so that the apparatus is positioned at an angle from a plane formed by the center of the diffuser and the sensing line, and a plurality of electrode assemblies. The EDM apparatus can be configured to be installed clockwise or counter-clockwise around the sensing line depending on the spacing available around given diffusers. The EDM apparatus is capable of burning a plurality of slots at the same time, thereby saving time and money.

Abstract: A primary containment vessel comprises an outer peripheral concrete wall surrounding a reactor pressure vessel, a pipe arrangement of a reactor water recirculation system and other reactor systems and equipments, a mat concrete wall positioned below the outer peripheral concrete wall, a reactor pressure vessel (RPV) pedestal supporting the reactor pressure vessel, a horizontal wall joining the outer peripheral concrete wall and the RPV pedestal, upper and lower dry wells, a wet well having a suppression pool in which water is stored, an isolation member for air-tightly isolating the upper dry well and the lower dry well at a position supporting the reactor pressure vessel, vent pipe arrangement used for the upper dry well communicating the upper dry well with the suppression pool, a high pressure gas inflow member used for the upper dry well located in a communicating hole formed to the RPV pedestal so as to communicate the vent pipe used for the upper dry well with a gas phase section of the wet well, anothe

Abstract: A seismic load suppressing system for a nuclear reactor that reduces the seismic input to the reactor and the internal components of the reactor including the fuel is described. The seismic load suppressing system includes, in one embodiment, a plurality of seismic isolators positioned circumferentially between the reactor pedestal and a lower pedestal and a plurality of displacement limiters coupled to a lower pedestal skirt and positioned adjacent the reactor pedestal. The seismic isolators include a plurality of alternating layers of a resilient material and steel plates bonded together. Each displacement limiter includes a cantilever beam. The beam includes a beam core and two steel plates laminated on opposing outer surfaces of the beam core. The steel plates are fabricated from carbon steel having a lower yield strength than the beam core.

Abstract: A shroud attachment assembly which provides both structural support for the shroud and a seal between the shroud and shroud support is described. In one specific embodiment, the shroud attachment assembly includes a shroud flange formed integral with the shroud, and a pump deck flange formed integral with the pump deck. The shroud flange extends over the pump deck flange, and a plurality of studs extend through aligned openings in the flanges. In addition, a plurality of wedges are secured to the shroud flange by studs, and the wedges extend between the shroud flange and the pump deck flange. Generally, the studs which extend through aligned openings in the shroud and pump deck flanges transfer vertical loads from the shroud to the pump deck, and the wedges transfer horizontal loads from the shroud to the pump deck.

Abstract: A nuclear reactor plant includes a reactor pressure vessel having a core barrel supported on a cylindrical holding structure fixed in the reactor pressure vessel. The core barrel has a lower part with at least one elastically resilient segment. A projection disposed on the segment engages under the holding structure in such a way that a wedge-like gap is formed between a lower surface of the holding structure and the projection. A wedge is braced in the gap. A method is also provided for mounting the core barrel.

Abstract: A mid-shroud joint which improves the replaceability of the shroud is described. In one embodiment, the shroud includes a core shroud and a lower shroud. A core plate support flange is clamped between the core shroud and the lower shroud, and the core plate support flange supports a core plate. The mid-shroud joint is formed by a flange of the core shroud and a flange of the lower shroud. The core plate support flange is positioned between core shroud and lower shroud flanges, and openings in these flanges align so that bolts can be inserted through such aligned openings.

Abstract: Support assemblies for allowing RPV radial expansion while simultaneously limiting horizontal, vertical, and azimuthal movement of the RPV within a nuclear reactor are described. In one embodiment, the support assembly includes a support block and a guide block. The support block includes a first portion and a second portion, and the first portion is rigidly coupled to the RPV adjacent the first portion. The guide block is rigidly coupled to a reactor pressure vessel support structure and includes a channel sized to receive the second portion of the support block. The second portion of the support block is positioned in the guide block channel to movably couple the guide block to the support block.

Abstract: An apparatus and method are provided for replacing the existing lower internal components in a nuclear reactor vessel with new components. The alignment of the new lower internals to the pressure vessel and the existing upper internals is achieved by customizing the new lower internals on-site based on alignment measurements obtained by gages installed on the new core barrel and the existing upper core plate. The gages allow the custom machining of radial support keys on the lower portion of the new core barrel and the custom drilling of upper core plate alignment pin holes in the new core barrel.

Abstract: In a pressure vessel of a nuclear reactor containing a core assembly enclosed within a core shroud, the core shroud spaced radially inwardly of a pressure vessel wall, with an annular shroud support plate fixed to the pressure vessel wall, wherein a lower end of the shroud is seated on an upper edge of the support plate to create a joint interface further wherein, and a plurality of brackets are secured between the shroud and the shroud support plate, spanning the joint interface.

Abstract: In order to support a shroud against bending, shear, stress and torsion, straps which are preferably formed of the same material as the shroud, are placed in strategic positions with respect to cracks or the like type of weaknesses which have been detected, and fastened in place using a suitable fastening technique. In the preferred embodiments of the invention holes are formed using an EDM technique and bolt units which have an expanding portion are inserted into the holes, torqued and expanded in a manner which fastens the strap to the shroud. Welding and the like type of fastening techniques are not excluded and may used alternatively or in combination with the bolting technique as required.

Abstract: A method of entombing a nuclear reactor where the reactor with its bio-shield remains intact. An access shaft, several lateral adits, and several chambers below the reactor location are excavated to provide access at underground locations below the reactor. A main cavern is excavated and lined with a lower base, surrounding sidewall, and a roof structure which has thermal plate at its lower surface. Freeze/thaw pipes are erected vertically in the cavern, and these extend through the earth strata below the cavern into a lower operating chamber. The cavern is filled with water which is then frozen, and the earth strata immediately below the reactor and are isolated from the surrounding earth strata and structure. The upper surface of the ice block is melted by the thermal plate in a controlled manner to lower the reactor, after which concrete and other material is used to fill all of the man made cavities and thus entomb the reactor.

Abstract: A vertical seismic isolation structure is capable of achieving vertical seismic isolation of nuclear reactor components connected to each other by primary pipings, while suppressing the relative displacement with respect to the primary pipings. A nuclear reactor vessel, circulating pumps and heat exchangers, all of which are connected to each other by primary pipings in which a coolant is circulated, are mounted on a common deck. Vertical seismic isolators each of which has laminated large coned disc springs and is capable of expanding and contracting in only the vertical direction are installed on the top of a concrete wall surrounding the respective nuclear reactor components. The common deck is placed on all the vertical seismic isolators so as to support the entire seismic isolation structure (the common deck, the nuclear reactor components, etc.).

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 nuclear power generation complex constructed on a stratum of rock overlain by soil deposits. All major structures in the power generation complex (i.e., reactor, turbine, radwaste and control buildings) are located on a common mat foundation that houses elastomeric bearings or seismic isolators. The foundation includes a concrete slab supported by a plurality of pedestals. Each of the pedestals is embedded in the rock. Preferably, each pedestal is a circular metal shell filled with underwater-type concrete, and the concrete slab is reinforced with steel bars. For example, a reactor building is supported by one set of seismic isolators mounted on the concrete slab, and a turbine building is supported by another set of seismic isolators mounted on the concrete slab. The isolators filter out a great deal of the seismic vibratory inputs. The common mat foundation eliminates differential movements between the buildings.

Abstract: A device for generating direct current by neutron activation of a plurality of series-connected beta-emitter (nuclear decay electron) cells, located in the out-of-core region of a light water nuclear reactor. The device can be used as either a current source, or preferably configured as a DC voltage source, capable of powering low-power, radiation-hardened, high-temperature integrated circuitry contained in the reactor vessel. As such, the device acts like a DC battery that is activated by (n, .gamma.) reactions, both thermal and epithermal (by resonance capture). The device is not operable until exposed to a substantial neutron flux, so it has unlimited shelf-life and is not radioactive during manufacture In the preferred embodiment, an isotope of the metallic rare-earth element dysprosium is configured in a "sandwich" geometry to generate sufficient current that a useful steady voltage can be generated by means of a simple voltage regulation circuit.

Abstract: In order to eliminate the need to weld, drill or otherwise machine a shroud structure which is used to surround a plurality of fuel assemblies in a nuclear reactor, a plurality of upper hanger rods interconnect a structure above the shroud to a support ring which is clamped about the upper periphery of the shroud. Lower hanger rods interconnect a lower edge or shoulder portion of the shroud with the support ring. Thus, through the upper and lower hanger rods and the support ring, the shroud can be supported within the RPV. The upper support ring is arranged to clamp the lower ends of the upper hanger rods against the upper outer peripheral portion of the shroud while the lower ends of the lower hanger rods are clamped against the lower peripheral wall portion of the shroud by a lower support ring.

Abstract: The vessel of the nuclear reactor includes at least three assemblies (22) distributed around the periphery of the core support plate (25), each comprising a key (26) fixed to the inner surface of the wall (21) of the vessel at the core support plate (25) and a cut-out (29) in the external edge of the core support plate (25) and open towards the outside in order to receive, with a clearance, an end part (30) of the key (26). The cut-out (29) includes an upper surface (29d) perpendicular to the axis of the wall (21) of the vessel and of the lower internals (23), which is machined in the core support plate (25) in order to retain the internals (23) in the event of a drop. A keyhole slot (28) is fixed inside the cut-out (29). In order to carry out the adjustment of the dimensions of the keyhole slot (28), a standard keyhole slot may be used, equipped with distance measurement sensors in order to obtain the desired clearances between the key (26) and the keyhole slot (28).

Abstract: In order to eliminate the need to weld, drill or otherwise machine a shroud structure which is used to surround a plurality of fuel assemblies in a nuclear reactor, a plurality of upper hanger rods interconnect a structure above the shroud to a support ring which is clamped about the upper periphery of the shroud. Lower hanger rods interconnect a lower edge or shoulder portion of the shroud with the support ring. Thus, through the upper and lower hanger rods and the support ring, the shroud can be supported within the RPV. The upper support ring is arranged to clamp the lower ends of the upper hanger rods against the upper outer peripheral portion of the shroud while the lower ends of the lower hanger rods are clamped against the lower peripheral wall portion of the shroud by a lower support ring.