Abstract: Disclosed herein is a fully passive decay heat removal system utilizing a partially immersed heat exchanger, the system comprising: a hot pool; an intermediate heat exchanger which heat-exchanges with the sodium of the hot pool; a cold pool; a support barrel extending vertically through the boundary between the hot pool and the cold pool; a sodium-sodium decay heat exchanger received in the support barrel; a sodium-air heat exchanger provided at a position higher than the sodium-sodium decay heat exchanger; an intermediate sodium loop connecting the sodium-sodium decay heat exchanger with the sodium-air heat exchanger; and a primary pump, wherein a portion of the effective heat transfer tube of the sodium-sodium decay heat exchanger is immersed in the cold pool, particularly in a normal operating state, and the surface of the lower end of a shroud for the sodium-sodium decay heat exchanger, the lower end being immersed in the sodium of the cold pool, has perforated holes.

Abstract: Disclosed herein is a decay heat removal system, including: a decay heat exchanger that absorbs decay heat generated by a nuclear reactor; a heat pipe heat exchanger that receives the decay heat from the decay heat exchanger through a sodium loop for heat removal and then discharges the decay heat to the outside; and a sodium-air heat exchanger that is connected to the heat pipe heat exchanger through the sodium loop and discharges the decay heat transferred thereto through the sodium loop to the outside. According to the decay heat removal system, a heat removal capability can be realized by the heat pipe heat exchanger at such a high temperature at which the safety of a nuclear reactor is under threat, and a cooling effect can be obtained through the sodium-air heat exchanger at a temperature lower than that temperature.

Abstract: A fast reactor has: a reactor vessel containing a coolant; a reactor core housed in the reactor vessel; a core supporting plate; a reflector; a partition arranged to surround the reflector on the side of the reactor vessel, for forming a passage of the coolant; a thermal shield arranged to cover at least one of the core side and the reactor vessel side of the partition; and a neutron shield. The thermal shield is mounted on the partition. The thermal shield includes a metallic thermal shield plate and a heat insulator mounted in the thermal shield plate, and has its inside filled with an inert gas. By the thermal shield, the thermal insulation of the partition can be improved to suppress the heat exchange between primary coolants on the core side and on the side of the reactor vessel of the partition.

Abstract: Exemplary embodiments provide automated nuclear fission reactors and methods for their operation. Exemplary embodiments and aspects include, without limitation, re-use of nuclear fission fuel, alternate fuels and fuel geometries, modular fuel cores, fast fluid cooling, variable burn-up, programmable nuclear thermostats, fast flux irradiation, temperature-driven surface area/volume ratio neutron absorption, low coolant temperature cores, refueling, and the like.

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: A direct pool cooling type passive safety grade decay heat removal method and system for removing core decay heat in a pool type liquid metal reactor when a normal heat removal system breaks down. In the liquid metal reactor comprising a reactor vessel, the interior of which is partitioned into a hot pool above a core and a cold pool around the core so that liquid level difference between the hot pool and the cold pool is maintained by a primary pumping head under normal steady-state conditions, is disposed at least one circular vertical tube in such a manner that the sodium in the circular vertical tube is maintained with the same liquid level as the liquid level of the sodium in the cold pool.

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: 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 liquid metal nuclear reactor is described. The reactor includes a concrete reactor silo, and at least one primary vessel located in the reactor silo and coupled to a reactor shield deck. Each primary vessel is substantially surrounded by a containment vessel in a spaced apart relationship. The reactor also includes a heat removal system which includes a guard vessel substantially surrounding each containment vessel in a spaced apart relationship, at least one inlet conduit in fluid communication with the ambient atmosphere outside the nuclear reactor, and at least one outlet conduit in fluid communication with the ambient atmosphere outside the nuclear reactor. A fluid flow heat transferring flowpath is formed by the inlet conduits, the space intermediate the guard vessel of each primary vessel and the containment vessel of each primary vessel and the outlet conduits.

Abstract: A seismically isolated liquid metal reactor power block is described. In one embodiment, the liquid metal reactor power block is a substantially rectangular nuclear plant with two nuclear islands and a common liquid metal service facility commonly supported on a seismic isolation platform near grade level. The seismic isolation platform supports the nuclear islands in a mirror-symmetric arrangement on opposite sides of a shared liquid metal service facility. A containment pressure suppression system connects the primary pressure relief volumes of the containment structures of each nuclear island to that of the other and also to a common pressure relief volume in the liquid metal service facility, thereby reducing the pressure load on each individual containment structure.

Abstract: An in-vessel structure for a top-entry type fast reactor wherein a core is positioned in the interior of a reactor vessel, an upper core structure being provided above the core, a coolant passing through a cold leg piping inserted from an upper portion of the reactor vessel thereinto and reaching the core, in which the coolant is heated, the coolant then flowing out to an upper plenum, the resultant coolant passing through a hot leg piping, which is inserted from an upper portion of the reaction vessel thereinto, and reaching the outside of the reactor vessel. A plurality of annular fins are fixed horizontally in an axially spaced manner to both the portions of an outer circumferential surface of the upper core structure and the opposite portions of an inner circumferential surface of the reactor vessel, these portions being under the free liquid surface during a rated operation of the reactor.

Abstract: A nuclear reactor, in particular a pressurized water reactor, has a containment, a containment shell surrounding the containment and a concrete construction of a reactor building surrounding the containment shell. A heat dissipation system for the nuclear reactor includes a sump volume disposed in a lower region of the containment shell for receiving coolant. A sump cooler is disposed inside the sump volume, has cooling tubes with a primary side and a secondary side and has feed and return lines. The primary side of the cooling tubes is covered at least when the sump volume is largely filled with coolant. An intermediate cooler has a tertiary side and is connected through the feed and return lines of the sump cooler to the secondary side of the cooling tubes. A heat sink is disposed outside the reactor building and is connected to the intermediate cooler on the tertiary side.

Abstract: An enhanced decay heat removal system for removing heat from the inert gas-filled gap space between the reactor vessel and the containment vessel of a liquid metal-cooled nuclear reactor. Multiple cooling ducts in flow communication with the inert gas-filled gap space are incorporated to provide multiple flow paths for the inert gas to circulate to heat exchangers which remove heat from the inert gas, thereby introducing natural convection flows in the inert gas. The inert gas in turn absorbs heat directly from the reactor vessel by natural convection heat transfer.

Abstract: A passive and inherent shutdown heat removal method with a backup air flow path which allows decay heat removal following a postulated double vessel leak event in a liquid metal-cooled nuclear reactor. The improved reactor design incorporates the following features: (1) isolation capability of the reactor cavity environment in the event that simultaneous leaks develop in both the reactor and containment vessels; (2) a reactor silo liner tank which insulates the concrete silo from the leaked sodium, thereby preserving the silo's structural integrity; and (3) a second, independent air cooling flow path via tubes submerged in the leaked sodium which will maintain shutdown heat removal after the normal flow path has been isolated.

Abstract: The nuclear reactor includes a fuel core (5) inside a vessel (2) and a system (1) for cooling the core (5), in which a liquid metal circulates and on which is placed at least one steam generator (15). The steam generator includes a casing (15a) in which the liquid metal circulates, water-feed means (16) and means for heat exchange between the liquid metal and the feed water. The liquid metal is caused to circulate in the cooling system (1), the steam generator (15) not being fed with water and the liquid metal circulating in the steam generator (15) is cooled by the flow of a gas in contact with the casing (15a) of the steam generator (15). The cooling device includes a tubular element (25) placed around the casing (15a) of the steam generator and defining an annular space for a cooling gas to flow around the casing (15a).

Abstract: The remote manipulation arm includes rigid sections (12, 14, 16) kept at a temperature adapted to their operation by a device comprising a vessel (37, 38, 39) surrounding each rigid section (12, 14, 16) and connected to a high-pressure coolant gas source. The vessel comprises two chambers (92, 94), respectively at high and low pressure, connected together by a discharge hole (102) for the gas. The rigid sections (12, 14, 16) are linked together by joints surrounded by bellows seals (40, 42) supplied by coolant gas from the low-pressure chamber (94) of a vessel (37, 38, 39) adjacent to the bellows seal. The gas circulates in a closed circuit comprising the chambers (92, 94) and the bellows seals (40, 42), absorbing the heat propagated through the remote manipulation arm.

Abstract: In a liquid-metal cooled nuclear reactor using liquid metal as a coolant and having vessels and pipings for accommodating the liquid metal coolant, at least pat of the region surrounding a coolant pressure boundary defined at outer wall surfaces of the vessels and piping is occupied by a mass of a solidified liquid metal. The solid mass (e.g. sodium) actually forms the coolant pressure boundary so that it is not so necessary to ensure the soundness of the steel walls of the vessels and pipings which accommodate the liquid metal coolant.

Abstract: A sodium cooled fast ractor comprises a reactor vessel in which a liquid metal coolant is accommodated, a core disposed substantially a lower central portion of the reactor vessel in an installed state, a core support structure secured to the reactor vessel for supporting the core, the core support structure dividing an interior of the reactor vessel into a high-pressure plenum below the core and a low-pressure plenum above the high-pressure plenum, a circulation pump unit for applying a discharge pressure to the liquid metal coolant and circulating the same, and an intermediate heat exchanger for performing a heat exchanging operation of the coolant in the reactor vessel. The circulation pump unit is composed of an electromagnetic circulation pump provided with a discharge port and a closed gas space, which is filled up with a closed gas, defined above and communicated with the discharge port.

Abstract: A liquid metal cooled nuclear fission reactor plant having a passive auxiliary safety cooling system for removing residual heat resulting from fuel decay during reactor shutdown, or heat produced during a mishap. This reactor plant is enhanced by a backup or secondary passive safety cooling system which augments the primary passive auxiliary cooling system when in operation, and replaces the primary system when rendered inoperable.

Abstract: A liquid metal cooled nuclear reactor having a passive cooling system for removing residual heat resulting for fuel decay during reactor shutdown, or heat produced during a mishap. The reactor system is enhanced with sealing means for excluding external air from contact with the liquid metal coolant leaking from the reactor vessel during an accident. The invention also includes a silo structure which resists attack by leaking liquid metal coolant, and an added unique cooling means.

Abstract: A liquid metal cooled nuclear reactor having a passive cooling system for removing residual heat resulting from fuel decay during reactor shutdown. The passive cooling system comprises a plurality of cooling medium flow circuits which cooperate to remove and carry heat away from the fuel core upon loss of the normal cooling flow circuit to areas external thereto.

Abstract: The internal shell (6) of the nuclear reactor comprises at least one cylindrical sleeve (10) with a vertical axis. An annular enclosure (20) is arranged on the internal periphery of the cylindrical sleeve (10), at the top part thereof. The enclosure (20) is open upwards and delimited by a cylindrical secondary sleeve (21) arranged coaxially and inside the cylindrical sleeve (10) of the internal shell. The top end of the secondary sleeve (21) is located below the high level (14a) of the liquid metal inside the internal shell (6). An annular base (22) is fixed to the bottom end of the secondary sleeve (21) and onto the internal surface of the cylindrical sleeve (10) of the internal shell (6), below the low level (14b) of the liquid metal.

Abstract: In order to ensure the cooling of the support ferrule of a vessel, such as the cylindrical internal vessel (14) of a fast neutron nuclear reactor, between said ferrule and an internal wall (20) containing a liquid metal at high temperature is placed a thermal protection apparatus (29). The latter comprises sealed collecting tanks (30) supplied with relatively cold, pressurized liquid metal by means of pipes (32), connected e.g. to the reactor bearing structure (16). This liquid metal is sprayed onto the ferrule by sprayers formed in the collecting tanks. On the side turned towards the wall (20), said tanks support elements (38) of a passive thermal protection structure.

Abstract: In a liquid metal cooled fast neutron nuclear reactor plant, surfaces (12) which are immersed in the flowing liquid metal and are vulnerable to liquid metal temperature fluctuations are provided with fins (20) defining cavities (22) for at least temporarily trapping the liquid metal to produce a thin layer of the liquid metal on the surface and thereby attenuate the effect of temperatures fluctuations occurring in the liquid metal flow.

Abstract: The upper part of the vessel (3) is cooled as a result of the circulation of cooled sodium (27). The cooled sodium coming form the lower part of the reactor core is introduced into a first collector (15) via pipes (17) and then overflows into a second collector (16). The second collector (16) or return collector is delimited by an overflow sleeve (18) and by an inner sleeve (21), the height of which is substantially less than the height of the overflow sleeve (18). The lower part of the inner sleeve (21) is connected to the overflow sleeve (18) by an annular plate (22) ensuring the stiffening of the sleeve (18). The height of the sleeve (21) is preferably between one-third and third of the height of the sleeve (18). This prevents vibrations from being generated during the circulation of the sodium.

Abstract: A novel liquid nuclear reactor is described which comprises a reactor vessel that is connected through upper and lower liquid conduit means to one or more satellite tanks that contain a heat exchanger means and pump means.

Abstract: The cover plug (4) comprises a cylindrical barrel (8), a support plate (10), a group of vertical tubes (12) for the control rods and for the instrumentation of the core, an apertured transverse plate (28) fixed to the lower end of the barrel (8) and a transverse deflection plate (32) located above the apertured plate (28). The transverse deflection plate (32) is suspended from the barrel (8) by substantially vertical elastically yieldable strips (34) evenly spaced apart on the periphery of the barrel (8). The strips (34) are welded to the barrel (8) by their upper end and to the edge of the deflection plate (32) by their lower end. They are located in the region of openings (35) in the barrel (8) which permit radial movement of the deflection plate. The deflection plate (32) is also integral with tubes (14b) receiving the control rods disposed in a single row coaxial with the barrel (8).

Abstract: A thermal barrier for use in a nuclear reactor facility is disclosed herein. Generally, the thermal barrier comprises a flexible, heat-resistant web mounted over the annular space between the reactor vessel and the guard vessel in order to prevent convection currents generated in the nitrogen atmosphere in this space from entering the relatively cooler atmosphere of the reactor cavity which surrounds these vessels. Preferably, the flexible web includes a blanket of heat-insulating material formed from fibers of a refractory material, such as alumina and silica, sandwiched between a heat-resistant, metallic cloth made from stainless steel wire. In use, the web is mounted between the upper edges of the guard vessel and the flange of a sealing ring which surrounds the reactor vessel with a sufficient enough slack to avoid being pulled taut as a result of thermal differential expansion between the two vessels.

Abstract: An improved reactor vessel auxiliary cooling system for a sodium cooled nuclear reactor is disclosed. The sodium cooled nuclear reactor is of the type having a reactor vessel liner separating the reactor hot pool on the upstream side of an intermediate heat exchanger and the reactor cold pool on the downstream side of the intermediate heat exchanger. The improvement includes a flow path across the reactor vessel liner flow gap which dissipates core heat across the reactor vessel and containment vessel responsive to a casualty including the loss of normal heat removal paths and associated shutdown of the main coolant liquid sodium pumps. In normal operation, the reactor vessel cold pool is inlet to the suction side of coolant liquid sodium pumps, these pumps being of the electromagnetic variety. The pumps discharge through the core into the reactor hot pool and then through an intermediate heat exchanger where the heat generated in the reactor core is discharged.

Abstract: A novel liquid nuclear reactor is described which comprises a reactor vessel that is connected through upper and lower liquid conduit means to one or more satellite tanks that contain a heat exchanger means and pump means.

Abstract: In a liquid metal-cooled fast neutron nuclear reactor which has a vessel sealed by a horizontal slab on which is suspended a core cover plug, the lower part of said plug comprises a deflecting grid, optionally duplicated by a thermal protection grid. Each of the grids is formed from a peripheral plate and modular plates defining between them passages for the liquid metal. The peripheral plates can be fixed to a perforated part of an external ferrule or can be suspended on a core cover plate by tie bolts and/or by certain of the control rod guidance sleeves. The modular plates are fixed to the other sleeves and traversed by sodium sampling tubes and tubes for housing thermocouples.

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: In a nuclear reactor of the type in which the vault has a roof in which inner and outer rotatable shields are mounted, coolant is supplied to the roof and shields via duct penetrations which extend in the plane of rotation and can be brought into alignment and connected together by slidable connectors when relative rotation between the shields and roof is not required. When such rotation is to be effected, the connectors can each be retracted into a respective duct so that rotation is not obstructed thereby.

Abstract: A fast breeder reactor has a nuclear reactor container filled with a liquid metal, a reactor core disposed within the nuclear reactor container, and a first supporting structural member which is mounted to the nuclear reactor container such as to support the reactor core. The fast breeder reactor is provided with a cylindrical structural member which surrounds the periphery of the reactor core such as to define an annular gap between the cylindrical structural member and the reactor core for allowing the liquid metal to exist therein, the cylindrical structural member being mounted to the nuclear reactor container by means of a second supporting structural member. The inertial resisting force produced when the liquid metal existing in the annular gap will flow out from the annular gap in response to the vibration of the reactor core acts such as to suppress the vibration of the reactor core, thereby allowing an improvement in the anti-vibration properties of the fast breeder reactor.

Abstract: The invention relates to a device for thermal protection of a component of a fast-neutron nuclear reactor consisting of at least one shell (10, 11) of a diameter smaller than the diameter of the passage (2) for the component (4) but greater than the diameter of the component (4). The length of the shell (10, 11) fixed under the flange (5) of the component (4) is greater than the slab thickness (1). Circulation of blanket gas (13) is established in the annular space (7) between the component (4) and the passage (2).The invention applies in particular to nuclear reactors cooled with liquid sodium whose upper level is under an argon blanket.

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: A fast neutron nuclear reactor, in which the main vessel and the slab for sealing said vessel are separately suspended on the upper part of the vessel shaft. An outer ferrule of the slab is directly anchored in the vessel shaft by tie rods and is supported by an annular ring embedded in the concrete. The upper edge of the main vessel is welded beneath the ring, the vessel being supported by a second annular ring embedded in the concrete. The upper faces of the slab and the vessel shaft are consequently at the same level, thereby reducing the heights of the vessel shaft and the safety vessel.

Abstract: A reactor core of a fast breeder reactor is supported by a core support within a reactor vessel. The reactor vessel is provided with a first or lower sodium chamber for accommodating low temperature sodium, a second or intermediate sodium chamber for accommodating low temperature sodium and a third or upper sodium chamber for accommodating high temperature sodium heated by passage of the low temperature sodium through the reactor core into the third sodium chamber. Low temperature sodium is introduced into the second sodium chamber arranged between the first and third sodium chamber for cooling the core support.

Abstract: In a liquid metal cooled nuclear reactor with a nuclear fuel assembly in a coolant-containing primary vessel housed within a concrete containment vault, there is thermal insulation to protect the concrete, the insulation being disposed between vessel and concrete and being hung from metal structure secured to and projecting from the concrete, the insulation consisting of a plurality of adjoining units each unit incorporating a pack of thermal insulating material and defining a contained void co-extensive with said pack and situated between pack and concrete, the void of each unit being connected to the voids of adjoining units so as to form continuous ducting for a fluid coolant.

Abstract: Cover-plug for the core of a fast neutron nuclear reactor, comprising a support-plate (6), a cylindrical shell (8) having a vertical axis fixed integrally to the support plate (6) and braces (14) which are transverse relative to the shell (8). Vertical tubes fixed to the support plate (6) at their upper part are joined to the braces (14), which consist of at least two conical webs (14) having their axes coincident with the axis of the shell (8). These conical webs have a top angle greater than 120.degree. and a diameter which is slightly smaller than the diameter of the shell (8), at their base. The brace (14a) situated in the lowest position in the shell (8) ensures the deflection of the reactor cooling fluid. The invention applies, in particular, to fast neutron nuclear reactors of the integrated type.

Abstract: A plenum separator system for separating the hot plenum from the cold plenum and from the reactor vessel wall in a pool-type nuclear reactor. One or more intermediate plena containing substantially stagnant and thermally stratified coolant provide axial separation of the hot and cold plena. A dual pass forced bypass flow through annuli at the upper portion of the reactor vessel wall, in conjunction with the intermediate plenum and an annular gas space adjacent the reactor vessel wall, provide radial separation of the hot plenum and the vessel wall.

Abstract: Liquid metal-cooled nuclear reactor incorporating a main vessel sealed by a slab and containing the reactor core, an inner vessel placed within the main vessel and defining in the latter a hot zone filled with relatively hot liquid metal and a cold zone filled with relatively cold liquid metal, at least one pump for circulating the liquid metal between the cold zone and the hot zone across the core and at least one heat exchanger disposed between the hot zone and the cold zone, wherein the inner vessel comprises two truncated cone-shaped ferrules opposed by their large bases and a small diameter cylindrical ferrule extending the small base of the upper truncated cone-shaped ferrule, the reactor core resting on the small base of the lower truncated cone-shaped ferrule by means of a support structure, the hot zone being formed within the inner vessel, while the cold zone is formed between the main vessel and the inner vessel.

Abstract: A device for providing protection against heat and radiation for an intermediate heat exchanger immersed in the vessel of a nuclear reactor. In its upper part, the exchanger has an inner sleeve (8a) inside which a liquid metal circulates, and an outer sleeve (8b), these sleeves being joined by a Y-shaped connector (25). A peripheral space is provided around the outer sleeve (8b), inside the passage (3) through the slab (2) covering the reactor vessel. The protection device comprises a sleeve (27) fixed under the flange (18) and carrying, in its lower part, a solid piece (30) occupying the greater part of the peripheral space around the sleeve (8b). In its upper part, under the flange (18), the sleeve (27) carries a heat insulation means (32) of annular shape. The Y-shaped connector (25) is located in the central part of the sleeve (27), between the solid piece (30) and the heat insulation means (32). The invention is applicable, in particular, to fast neutron nuclear reactors cooled by liquid sodium.

Abstract: The invention relates to a fast neutron nuclear reactor of the integrated type comprising a cylindrical inner vessel.The inner vessel comprises two concentric ferrules and the connection between the hot collector defined within this vessel and the inlet port of the exchangers is brought about by a hot structure forming a heat baffle and supported by the inner ferrule and by a cold structure surrounding the hot structure, supported by the outer ferrule and sealingly connected to the exchanger.Application to the generation of electric power in nuclear power stations.

Abstract: An improved passive cooling arrangement is disclosed for maintaining adjacent or related components of a nuclear reactor within specified temperature differences. Specifically, heat pipes are operatively interposed between the components, with the vaporizing section of the heat pipe proximate the hot component operable to cool it and the primary condensing section of the heat pipe proximate the other and cooler component operable to heat it. Each heat pipe further has a secondary condensing section that is located outwardly beyond the reactor confinement and in a secondary heat sink, such as air ambient the containment, that is cooler than the other reactor component. Means such as shrouding normally isolated the secondary condensing section from effective heat transfer with the heat sink, but a sensor responds to overheat conditions of the reactor to open the shrouding, which thereby increases the cooling capacity of the heat pipe.

Abstract: The annular space (19) delimited by the main vessel (3) and an internal shell (16) is in communication with the zone (15) of the reactor vessel, in which the cold primary liquid is located. The annular space (20) delimited by the shell (16) and by an internal shell (17) is in communication with the lower part of the core (7) via tubes (31). Thus, the cold primary liquid is injected into the space (20), where it circulates from bottom to top, and flows into the space (19), where it circulates from top to bottom while at the same time cooling the main vessel (3).The invention applies, in particular, to fast fission nuclear reactors cooled by liquid sodium.

Abstract: A nuclear reactor of the type which uses liquid metal as primary and secondary coolants, and wherein the reactor vessel contains a core and a plurality of vertically extending cylindrical intermediate heat exchangers for carrying out heat exchange between the primary and secondary coolants; primary coolant circulation pumps disposed outside of the reactor vessel; a pipe for conducting to the circulation pump the primary coolant which has passed through the intermediate heat exchangers after leaving the core; and a pipe for guiding the primary coolant discharged from the circulation pump to the core through the reactor vessel.

Abstract: The invention relates to a nuclear reactor cooled by a liquid metal contained in a vessel obturated by upper closing means, said latter essentially being constituted by a slab and rotating plugs. The upper closing means comprise at least one circuit for circulation of a cooling gas or liquid, this circuit being provided with means for maintaining the closing means at a homogeneous temperature at least equal to 100.degree. C. and preferably close to 120.degree. C. The invention is applicable to the production of less cumbersome and less expensive fast neutron nuclear reactors.

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: 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.