Abstract: The leaf springs mounted in the upper nozzle of a prior art fuel assembly, which are compressed by the upper core plate to restrain the upward movement of the fuel assembly under the pressure of upwardly-flowing coolant, as dispensed with. Instead the fuel assembly is permitted to rise in a controlled manner into engagement with the upper core-support plate. The lower nozzle is provided with snubbers which engage, and exert low pressure, as required by the specifications governing a reactor, on the lower core plates when the fuel assembly is raised into engagement with the upper core plate by the force of the flowing coolant. In addition springs are provided between the pins extending from the upper and lower core plates and the walls of the holes in the upper and lower nozzles to suppress vibration under the transverse forces impressed by the flowing coolant.

Abstract: A tension loaded energy dissipating support member includes multiple successively longer metal straps all connected at each end to an end connector with the longer straps, and preferably the shortest strap, bowing outward laterally such that as the tensile load increases, the straps, beginning with the shortest, successively plastically deform to dissipate shock energy. The initial bowing, type of material, and relative dimensions of the straps can be varied to obtain the desired load supporting and energy dissipating characteristics.

Abstract: A tubular cluster guide for use in a nuclear reactor having upper internals comprising a lower plate formed with flow openings is fixed to an upper plate of the intervals and provided with a device for guiding and centering its lower part in the lower core plate. The centering device has a plurality of rigid blades carried by the lower part of the guide, spaced apart angularly about the axis of the guide and engagable in an opening of the lower plate with a radial clearance and a plurality of flexible blades between the rigid blades. The flexible blades bear on the edge of the opening and exert a radially directed force thereon. Bridges may be formed in the lower plate to retain a broken resilient blade.

Abstract: A nuclear component horizontal seismic restraint. Small gaps limit horizontal displacement of components during a seismic occurrence and therefore reduce dynamic loadings on the free lower end. The reactor vessel and reactor guard vessel use thicker section roll-forged rings welded between the vessel straight shell sections and the bottom hemispherical head sections. The inside of the reactor guard vessel ring forging contains local vertical dovetail slots and upper ledge pockets to mount and retain field fitted and installed blocks. As an option, the horizontal displacement of the reactor vessel core support cone can be limited by including shop fitted/installed local blocks in opposing alignment with the reactor vessel forged ring.

Abstract: Spacer grids for a nuclear fuel assembly are arranged in superadjacent groups having grid springs and opposing dimples which contact a fuel rod passing through a cell of the spacer grid with a selected spring force. As fabricated, the lowermost grid exerts the greatest initial spring force on the rod; intermediate grids exert a smaller spring force; and the uppermost grid exerts yet a lower spring force. The fuel rod is supported laterally while it is permitted to age expand axially with little axial compression resulting from the spring forces of the springs and dimples, whereby bowing of the rod is diminished.

Abstract: Antiseismic support structure for the pile block of a fast neutron nuclear reactor.It comprises a concrete covering slab resting on the reactor building structure. The vessel and components of the pile block are suspended on said slab in a well of said structure. The building rests on the ground by means of two superimposed floors, namely an upper floor and a lower floor. The two floors are separated from one another by elastic supports, permitting a horizontal oscillatory displacement with respect to one another with a view of filtering the horizontal components of the earthquake with respect to the vessel. These elastic supports are in particular fretted elastomer supports.

Abstract: A vibration arrestor for use in combination with the support structure for the upper ends of rod guides disposed in parallel axial relationship in an inner barrel assembly of a pressurized water reactor vessel, the rod guides being supported between a first, lower plate and a second, upper plate with their respective top ends disposed adjacent the second plate. At least for a selected type of rod guides and associated top plates, apertures provided in the top plates receive therein corresponding extensions which depend from the second plate.

Abstract: A steam generator for nuclear power plant applications. U-shaped heat exchanger tubes within said steam generator are provided with compliant antivibration bars at the U-shaped portion of the tubes. Flexible plates located at opposite sides of the antivibration bars are placed in contact with the opposite sides of the rows of tubes. Support ribs spaced along the length of the compliant bars limit the deflection of the flexible plates and establish the effective length of the flexible plates. The ribs in successive columns of antivibration bars are located between the ribs of the bars of each preceding and following row.

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

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

Abstract: A cask for storing spent nuclear fuel after removal from a pool of water includes a container with a cylindrical cavity and a basket which is inserted into the container. The basket includes disk-like grid assemblies which provide spent fuel storage slots and which are coaxially mounted at spaced-apart positions, each grid assembly having a diameter that is slightly less than the one above it. If fuel assemblies are to be stored, hollow cells are affixed to one of the grid assemblies and positioned in the others by heat-conducting wedges which permit the basket and cells to expand at different rates. Rings which project slightly into the interior of the container are provided on the container walls, each ring being positioned to be in alignment with the periphery of a corresponding grid assembly after the basket is inserted into the container.

Abstract: A steam generator wrapper barrel/tube support plate connection assembly and method for assembling same which prevents interference due to thermal interaction between a wrapper barrel with a first coefficient to thermal expansion and a tube support plate with a second, relatively higher coefficient of thermal expansion. Interference is prevented by radially tuning the wrapper barrel, i.e., locally introducing preload via increased stud thread engagement in the jacking assembly to deform the wrapper barrel during assembly. During subsequent heat-up and operation the preload is relieved through outer shell expansion. In addition, heat and/or pressure dissolvable-surfaced or spring-surfaced shims or wedges are fit between the wrapper barrel and the tube support plate to further compensate for tube support plate thermal expansion.

Abstract: A support system for connection to an outer surface of a J-shaped steam generator for use with a nuclear reactor or other liquid metal cooled power source. The J-shaped steam generator is mounted with the bent portion at the bottom. An arrangement of elongated rod members provides both horizontal and vertical support for the steam generator. The rod members are interconnected to the steam generator assembly and a support structure in a manner which provides for thermal distortion of the steam generator without the transfer of bending moments to the support structure and in a like manner substantially minimizes forces being transferred between the support structure and the steam generator as a result of seismic disturbances.

Abstract: An improved liquid metal nuclear reactor construction has a reactor core and a generally cylindrical reactor vessel for holding a large pool of low pressure liquid metal coolant and housing the core within the pool. The reactor vessel has an open top end, a closed flat bottom end wall and a continuous cylindrical closed side wall interconnecting the top end and bottom end wall. The reactor also has a generally cylindrical concrete containment structure surrounding the reactor vessel and being formed by a cylindrical side wall spaced outwardly from the reactor vessel side wall and a flat base mat spaced below the reactor vessel bottom end wall. A central support pedestal is anchored to the containment structure base mat and extends upwardly therefrom to the reactor vessel and upwardly therefrom to the reactor core so as to support the bottom end wall of the reactor vessel and the lower end of the reactor core in spaced apart relationship above the containment structure base mat.

Abstract: An improved top nozzle includes leaf spring assemblies interposed between its movable upper hold-down plate and stationary lower adapter plate and arranged along respective peripheries thereof. The leaf spring assemblies bias the upper hold-down plate in an upward direction into contact with the upper core plate of the reactor and thereby impose a hold-down force on the fuel assembly via the lower adapter plate. In the preferred embodiment, each leaf spring assembly includes opposite lower and upper ends, with the lower end being attached to the lower adapter plate adjacent one of the corners on its periphery and the upper end being movably coupled in a groove on the upper hold-down plate adjacent a next one of the corners on its periphery. The leaf spring assemblies are arranged in a single file about the peripheries of the lower adapter plate and upper hold-down plate, with one assembly extending between each pair of succeeding corners on the respective peripheries of the lower and uper plates.

Abstract: A holddown spring retention assembly for use in a nuclear reactor having a pressure vessel, a core barrel having an upper outwardly extending flange, an inner barrel having an upper outwardly extending flange and an annular holddown spring, the barrels and the spring being installed in the pressure vessel during normal operation, with the inner barrel flange disposed above the core barrel flange and the holddown spring interposed between the core barrel flange and the inner barrel flange, the holddown spring retention assembly is composed of a plurality of assembly units disposed around the periphery of the holddown spring, each unit including a lift lug secured to the outer periphery of the spring and having at least one outwardly radially projecting portion and a hanger secured to the inner barrel flange and having a lower portion suspended below the inner barrel flange and below the radially projecting portion of the lift lug means; the lower portion being arranged to support the radially projecting portio

Abstract: The invention relates to a nuclear reactor cooled by a liquid metal comprising a vessel (12) containing the reactor core (24), a vessel shaft (18) and a sealing slab (14).The bottom (12a) of the vessel rests on the bottom (52) of the vessel shaft via supports (54) defining between the said two bottoms a space (56) in which circulates a cooling fluid such as air. A skirt (74) surrounds vessel (12) and rests on the vessel shaft bottom (52) for supporting slab (14).Application to the construction of simpler and less expensive fast neutron reactors than those hitherto known.

Abstract: An intermediate seismic support system (100) comprises substantially square-shaped seismic support base members (102) which are suspendingly supported from rod position indicator coil assemblies (48) so as to peripherally surround control rod drive mechanism latch housings (20) in order to restrain deflections of the control rod drive mechanisms (12) under seismic conditions. In addition to being remotely installed and removed as a result of being mounted upon the RPI assemblies (48), the seismic supports are also remotely adjustable relative to one another through means of radially movable adjustment blocks (126) which are caused to move radially by means of axially movable actuator blocks (130). The latter blocks (130) are controlled by means of vertically extending actuator rods (134).

Abstract: Apparatus for limiting the effect of axial hydraulic flow force exerted on the fuel assemblies by the hydraulic pressure of a coolant in a water-cooled nuclear reactor comprises slit cylindrical elastic sleeves positioned within recesses in cylindrical housings carried by the fuel assemblies, the sleeves receiving centering pins connected to upper and lower core plates of the reactor and exerting frictional force thereon so as to control the axial movements of the fuel assemblies during transient variations in hydraulic flow force.

Abstract: The lower end of a nuclear reactor core barrel (16) is laterally stabilized within the reactor pressure vessel (10) by four auxiliary support structures (100) equiangularly disposed about the periphery of the reactor lower hemispherical shell (12). The core barrel lower support plate (18) has keys (122) secured thereto for disposition within recesses (114) defined within crossbeams (102) of the structures (100) through which horizontal radial and tangential forces, as well as severe vertical loads, are transmitted from the core barrel (16) to the reactor vessel (10). Shock absorbers (120) interconnect the keys (122) and the crossbeams (102), and divergent brackets (104) serve to radially space the crossbeam (102) from the shell wall (12) so as to define a vertical coolant flow channel (108) through each structure (100).

Abstract: There is provided a shock absorber for containers for the transportation and/or storage of radioactive materials consisting of one or more radially or axially arranged chambers which are filled with shock absorbing material characterized by the shock absorber containing cup spring shaped sheets having a curvature directed away from the container.

Abstract: Device for the dismantlable fixing of a guide tube in a recess provided for this purpose in the end piece of a fuel assembly of a nuclear reactor, particularly of the water-cooled type, wherein the guide tube has an end fitting, whose ferrule-like end has an inner cylindrical profile slotted over its entire length into a certain number of flexible sectors which can be engaged in an annular recess, or on a bore having circular engagement threads on its surface, under the pressure of an internal cylindrical locking ring, means also being provided for braking the locking ring in axial translation with respect to the end piece and for remotely ensuring the dismantling of the ring.

Abstract: A restraint assembly for use in restraining lateral movement of a reactor core relative to a reactor vessel wherein a plurality of restraint assemblies are interposed between the reactor core and the reactor vessel in circumferentially spaced relation about the core. Each lateral restraint assembly includes a face plate urged against the outer periphery of the core by a plurality of compression springs which enable radial preloading of outer reflector blocks about the core and resist low-level lateral motion of the core. A fixed radial key member cooperates with each face plate in a manner enabling vertical movement of the face plate relative to the key member but restraining movement of the face plate transverse to the key member in a plane transverse to the center axis of the core.

Abstract: The invention comprises a core barrel plug capable of being remotely installed in a port of a core barrel of a pressurized water nuclear reactor for converting the reactor from a by-pass downflow configuration to a by-pass upflow configuration. The plug comprises a body having an expandable cylindrical portion with a movable mandrel disposed in the body. Remote fluid pressurization causes the mandrel to be advanced thus expanding the body into contact with the port. The plug also comprises a locking mechanism to prevent inadvertent release of the plug.

Abstract: A plunger element which slides axially in a bore in a dashpot element secured to the internals of a steam generator is biased against the shell of the pressure vessel by a series of Belleville springs. The plunger and dashpot element form a chamber having a volume which varies as the width of the gap between the pressure vessel shell and internals changes due to differential thermal expansion, and pressure expansion of the shell. A collapsible reservoir provides an incompressible fluid to the variable volume chamber under urging of the ambient pressure in the pressure vessel through a metering passageway to maintain the chamber full of fluid.

Abstract: Hydraulic jacks are arranged radially both inside and outside the confinement chamber (EC), substantially on a level with the center of gravity of the boiler (BV, EA) disposed inside. The inside jacks transmit thrust to the boiler via an annular floor (20). The outside jacks transmit thrust to the walls (M) of the hall. The outside jacks are arranged as energy-absorbing dampers. The inside and outside jacks resist fast compression by means of calibrated fluid flow orifices, while they expand readily by means of one way valves and pressure accumulators. The boiler and the confinement chamber stand on a base that is resiliently movable in a horizontal direction relative to the raft (R) of the building. This ensures that the reactor is returned to its normal position once an earthquake is over.

Abstract: A device for partitioning off the core of a nuclear reactor, including transverse plates (17) attached to the envelope (8) of the core and arranged transversely with respect to the fuel assemblies (5), and second plates (19) extending in the longitudinal direction with respect to the fuel assemblies. The second plates (19) are arranged in gaps between the transverse plates (17) and slightly stepped back with respect to the assemblies (5). The transverse plates (17) are connected to the longitudinally extending plates (19) with a certain clearance in the longitudinal direction. The transverse plates (17) are in contact with the assemblies (5) arranged at the periphery of the core by way of a portion of their peripheral surfaces.

Abstract: End fitting for the fuel assembly of a nuclear reactor comprising in per se known manner a device for holding the fuel assembly against an upper or lower plate of the reactor core, wherein the maintaining device is constituted by a plurality of rigid levers, having a first end and a second end, each lever being articulated on an axis A, a closed recess provided in the sides of a frame of the end fitting for each lever and elastic means contained in the recesses and exerting a restoring torque on the corresponding lever.

Abstract: Constant or transient forces and displacements between a motion snubber and its associated load are detected and converted to an electrical signal. Electrical signals from the detection devices are transmitted to a receiving device which is electrically connected to a recording means. The signals from a plurality of detecting devices are encoded to identify the snubber having the detected force and displacement.

Abstract: A nuclear reactor fuel assembly having an improved top nozzle subassembly with a hold-down device incorporated therewithin to prevent the force of the upward coolant flow from lifting the fuel assembly into damaging contact with the upper core support plate, while allowing for changes in fuel assembly length due to core-induced thermal expansion. The construction of the fuel assembly is such that its top surface can be placed in direct contact with the upper core plate. Thermal expansion of the components of the fuel assembly in the upward direction are accommodated within the top nozzle subassembly.

Abstract: A concrete pressure vessel (1) for a nuclear reactor is formed with an arch (6) arranged above the cover (4) of the pressure vessel, said arch having a horizontally directed opening permitting horizontal transport of the cover. The cover (4) is retained by a plurality of compressive force transmitting elements (11) arranged between the cover and the arch (6).

Abstract: Reactor building structure comprising a ring building roof embedded in the cylindrical skirt of the confinement enclosure.The structure is constituted by a confinement enclosure comprising a cylindrical skirt and a dome, as well as by a ring building surrounding the confinement enclosure. The ring building comprises a cylindrical skirt and a roof, the confinement enclosure and the ring building being erected on a common general foundation raft or floor. The internal structures are positioned with the confinement enclosure. The roof of the ring building is toroidal or frustum-shaped, being embedded in the cylindrical skirt of the confinement enclosure. The internal structures are disengaged from the confinement enclosure.

Abstract: The present invention pertains to a means of connecting a primary pump (intended for sodium or the like) and the delivery pipe within a breeder reactor of the swimming-pool type, permitting limited movement of the pump and the pipe in relation to one another to occur, while also maintaining adequate sealing between low pressure areas and high pressure areas within said pump. The connecting component consists of a cylindrical sleeve (11) which, in a resting position, is situated along the same axis (1) as the delivery pipe for the pump. A cylindrical guide (3) which is fastened to the pump is fitted into the aforementioned pipe, and a sealing joint (13) is situated between the sleeve (11) and the guide (3). There is also a horizontal annular collar (12) which is fastened to the aforementioned sleeve (11), resting upon an annular rim (5) situated upon the upper flange (7) of the pipe (4).

Abstract: Seismic restraint means are provided for mounting an elongated, generally cylindrical nuclear radiation detector within a tubular thimble. The restraint means permits longitudinal movement of the restraint means and the radiation detector into and out of the thimble. The restraint means includes spring bias means and thimble constant means whereby the contact means engage the thimble with a constant predetermined force which minimizes seismic vibration action on the radiation detector.

Abstract: The present invention relates to a device for damping impacts caused by the fall of heavy objects. This device comprises a group of deformable mechanical members arranged perpendicularly to a first plate and a second plate, a supplementary plate having substantially the same weight as each mechanical member being placed between the latter and the second plate. The supplementary plates are contiguous and each mechanical member has at least one predeformation at its end adjacent to the second plate. Application to the protection of discharge ponds against the fall of caskets.

Abstract: A gas cooled, high temperature nuclear reactor is provided with a base plate arranged under the reactor core and over the bottom of the prestressed concrete pressure vessel serving as the bottom shield. The bottom shield comprises at least two plates arranged coaxially with respect to each other, one above the other. Each plate comprises several partially interconnected parts with the lower plate being placed at an axial and vertical distance from the bottom liner of the prestressed concrete pressure vessel and also from the upper plate.

Abstract: Reactor building comprising internal structures, whose stresses are independent of the deformations of the general floor and of the background effect due to the reference accident pressure, and process for producing the internal structures.This reactor building comprises a confinement enclosure (4), internal structures (14) constituted by a slab (22) peripherally locked against the frustum-shaped member (12) of confinement enclosure (4) and resting on the general floor (8) by a peripheral supporting ring (23), a compressible layer (32) being provided between the general floor (8) and slab (22).Application to the construction of the internal structures of a reactor building.

Abstract: A support structure for a nuclear power station having a prestressed cylindrical vessel comprising an annular ring of supports on a support wall and foundation wherein the prestressed cylindrical vessel rests on the ring of supports is disclosed. The supports, through their defined distances from each other, provide a constant cooling flow of the supports and a constant temperature over the entire operating period of the power station. This results in supports that are maintenance-free. The supports are constructed of plastic washers with steel inserts and are of sufficient height such that in the case of earthquakes, maximum vibrations of the reinforced concrete pressure vessel may be absorbed within an accurately set terminal boundary of the annular support wall.

Abstract: Reactor building comprising a vessel shaft anchored in a slab which is peripherally locked.This reactor building comprises a confinement enclosure (4) within which are positioned internal structures (14) constituted by an internal structure floor (16), a vessel shaft (18), a slab (22) being positioned between the general floor (8) and the internal structure floor (16), the vessel shaft (18) being anchored in the slab which is peripherally locked against the low part of the confinement enclosure skirt (12), a horizontal sliding joint (24) being positioned between slab (22) and internal structure floor (16).Application to the construction of the internal structures of a reactor building.

Abstract: An anti-earthquake support device arranged between an element of large mass and a fixed support, comprising roller elements arranged between support parts forming roller tracks inclined with respect to the horizontal plane. The roller elements are cylindrical rollers (14,15,17) arranged horizontally in two superposed sets of rollers with perpendicular axes. The support parts (4,10 and 11) are entirely independent of one another and are arranged above one of the sets of roller for the first (4), between the two sets of rollers for the second (10) and beneath the second set of rollers for the third (11). The corresponding roller tracks (9, 20, 21 and 24) are formed on either the lower, or the lower and upper, or the upper surfaces of the three support parts (4, 10 and 11), respectively. The invention is used for the support of a fuel assembly rack for a nuclear reactor on the bottom of the storage pool of such reactor.

Abstract: Apparatus for partitioning off the core of a nuclear reactor constituted by a set of boxes (8, 9, 10, 11) each comprising at least two plates (12-13, 14-15, 27-29, 28-30) rigidly assembled at right angles and disposed in the longitudinal direction of the assemblies, and a plurality of transverse plates (32) perpendicular to the longitudinal plates. The boxes are removably disposed side by side inside the core casing (1), and bearing thereon. The faces of the longitudinal plates directed towards the reactor core serve as bearing faces for the assemblies. Each of the boxes is fixed to at least one of the upper or lower plates of the core by a flexible coupling allowing longitudinal displacement.

Abstract: The present invention relates to a device providing anti-seismic support for an apparatus immersed in the bath of liquid alkali metal surrounding a fast neutron nuclear reactor, and abutting by a flange on a slab traversed by the apparatus and resistant to the load that it constitutes, wherein the flange for supporting the apparatus is connected to a sleeve for elastically taking up the horizontal displacements of its top part, independently of an inner envelope of the apparatus and on which a framework for supporting the apparatus whose bottom part is connected to the inner envelope, is fixed at a level determined as a function of the most dangerous earth tremor frequencies.

Abstract: A support structure for the core of a gas cooled high temperature reactor utilizes a plurality of compression members arranged in an annular space between a plurality of graphite blocks forming the roof, bottom and cylindrical side walls of a reflector surrounding the reactor core and a thermal shield surrounding the reflector. Each compression member comprises a compression body, a first bolt part having the configuration of a threaded rod, a threaded area on the inner surface of the compression body for receiving the threaded bolt part, a second bolt part having the configuration of a piston, a sliding area on the inner surface of the compression body for receiving the piston bolt part, and means for producing a compressive force between the piston bolt part and the compression body. The plurality of compression members are attached to the reflector and thermal shield by way of a plurality of ball-and-socket joints.

Abstract: A storage device for nuclear plants for storing spent fuel elements in such a way as to preclude relative movement between the walls of the element storing chamber and the fuel element. The invention contemplates storing chambers whose cross-section is square and fuel elements in the shape of four sided prisms. At least two opposite guide surfaces are arranged obliquely to the longitudinal axis of the storing chamber and to the longitudinal axis of the fuel element to be stored therein. These guide or guiding surfaces are positioned near the bottom of the storing chamber. The guiding surfaces are adapted to engage the lower edge of the fuel element placed in the storage chamber and to impart a rotary motion to the former so that its four longitudinal edges engage the wall of the storage chamber. In this position no impact between the walls of the storage chamber and the spent fuel element can occur.

Abstract: Thermal insulation device for insulating the upper area of the annular space separating the main vessel and safety vessel of a fast neutron nuclear reactor, said two vessels having a common vertical axis and are sealed in their upper part by a horizontal slab which is also responsible for the suspension of the two vessels, wherein the said device comprises a lower thermal insulation ring having a generally annular shape defining an inner peripheral edge spaced from the main vessel and fixed to the lower end of an inner thermal insulation baffle whose upper end is fixed to the main vessel, and an outer peripheral edge spaced from the safety vessel and fixed to the lower end of an outer thermal insulation baffle whose upper end is fixed to the safety vessel, each of the thermal insulation baffles being deformable so as to compensate any differential expansion or deformation of the vessels.

Abstract: In this type of nozzle penetration, the nozzle (6) consists of a material different than that of the closure (1). In addition, closure (1) is provided with an inside plating. In order to avoid heat stresses on the tension coupling (15) between nozzle (6) and closure (1), a compensating ring (8) is provided between the shoulder (9) of nozzle (6) and contact surface (7) of closure (1). The height "h" of the compensating ring (8) and its material are selected in such a way that the change in elongation resulting from heat expansion of the nozzle and closure materials is compensated in the region of the distance extending from shoulder (9) to tension coupling (15). The material and height "h" can be selected in such a way that a predictable difference in stress is created in the area of the tension coupling upon heating.

Abstract: An improved pressurized fluid reactor system having a fluid cooled reactor core in which the coolant pump for delivering fluid to the reactor core is driven by a pump motor through a unidirectional drive means which enables the pump to operate at a greater speed than the pump motor in the pumping direction only. A preferred unidirectional drive means in the form of a ratchet means is disclosed.

Abstract: A liquid metal reactor comprising a vessel containing the core and liquid metal, at least one heat exchanger ensuring a heat-exchange between said liquid metal and a second fluid, a first duct connecting said vessel with the inlet of said exchanger and a second duct connecting said vessel with the outlet of said exchanger. Means are provided for restricting the movement of said exchanger in two directions perpendicular to the direction of said first duct.

Abstract: A pool type nuclear reactor including a number of reactor components located within a vertically extending cavity which is located under a reactor deck arrangement and which is defined by a circumferential cavity wall assembly is disclosed herein. The reactor also includes a reactor vessel separate and distinct from the deck arrangement and the cavity wall assembly for containing the reactor components just recited. This vessel includes a main body located within the cavity and an upper circumferential rim forming a support flange located and interlocked between the deck arrangement and an upper section of the cavity wall assembly whereby to support the vessel body in place.

Abstract: Improved thermal insulation for a nuclear reactor deck comprising many helical coil springs disposed in generally parallel, side-by-side laterally overlapping or interfitted relationship to one another so as to define a three-dimensional composite having both metal and voids between the metal, and enclosure means for holding the composite to the underside of the deck.