Abstract: An electromagnet comprises a plurality of nested freestanding electrically insulating former layers, and electrically conductive wire wrapped around the outsides of the freestanding electrically insulating former layers to define a multilayer electrical coil in which adjacent layers of the multilayer electrical coil are spaced apart by intervening freestanding electrically insulating former layers. Electrically energizing the multilayer electrical coil generates a magnetic field inside the multilayer electrical coil. In some embodiments the electrically conductive wire is bare wire not having electrical insulation. In some embodiments the former layers comprise a ceramic material. In some such embodiments the electromagnet further comprises a ferromagnetic core disposed inside the multilayer electrical coil. An electric motor employing such an electromagnet as a stator pole is also disclosed.

Abstract: A stable startup system includes a reactor vessel containing coolant, a reactor core submerged in the coolant, and a heat exchanger configured to remove heat from the coolant. The stable startup system further includes one or more heaters configured to add heat to the coolant during a startup operation and prior to the reactor core going critical.

Abstract: A nuclear reactor module includes a reactor vessel containing coolant, a reactor core submerged in the coolant, and a heat exchanger configured to remove heat from the coolant. The nuclear reactor module further includes one or more heaters configured to add heat to the coolant during a startup operation and prior to the reactor core going critical.

Abstract: The present invention relates to a nuclear reactor, in particular a pool-type nuclear reactor cooled with liquid metal (for example, a heavy metal such as lead or lead-bismuth eutectic) or with sodium or molten salts, having a core formed by a bundle of fuel elements and immersed in a primary fluid circulating between the core and at least one heat exchanger; the fuel elements extend along respective parallel longitudinal axes and have respective bottom active parts immersed in the primary fluid to constitute the core, and respective service parts that extend at the top from the active parts and emerge from the primary fluid; the fuel elements are mechanically supported via respective top end heads anchored to supporting structures and can be operated via handling machines.

Abstract: Nuclear reactor systems and methods are described having many unique features tailored to address the special conditions and needs of emerging markets. The fast neutron spectrum nuclear reactor system may include a reactor having a reactor tank. A reactor core may be located within the reactor tank. The reactor core may include a fuel column of metal or cermet fuel using liquid sodium as a heat transfer medium. A pump may circulate the liquid sodium through a heat exchanger. The system may include a balance of plant with no nuclear safety function. The reactor may be modular, and may produce approximately 100 MWe.

Abstract: A nuclear reactor includes a pressure vessel and a nuclear reactor core disposed in the pressure vessel. A subterranean containment structure contains the nuclear reactor. An ultimate heat sink (UHS) pool is disposed at grade level, and an upper portion of the subterranean containment structure defines at least a portion of the bottom of the UHS pool. In some embodiments, the upper portion of the subterranean containment structure comprises an upper dome, which may protrude above the surface of the UHS pool to define an island surrounded by the UHS pool. In some embodiments, a condenser comprising a heat exchanger including hot and cold flow paths is disposed inside the subterranean containment structure; and cooling water lines operatively connect the condenser with the UHS pool.

Abstract: A nuclear reactor in which a primary coolant is contained, the primary coolant moves upwardly from the core by an operation thereof. An annular steam generator is arranged in an upper side of the core into which the upwardly moving primary coolant flows and transfers heat in the primary coolant into water therein to generate a steam. A passage structure defines a coolant passage for the primary coolant to an outside of the core. The heat-transferred primary coolant in the annular steam generator flows downwardly in the coolant passage so as to flow into the core, thereby moving upwardly. A reactor vessel is arranged to surround the coolant passage so as to contain the core, the annular steam generator and the passage means therein.

Abstract: The invention relates to an assembly for exchanging heat between first and second fluids, the assembly comprising a central manifold communicating with one of the inlet and the outlet for the first fluid; an annular manifold disposed around the central manifold and communicating with the other one of the inlet and the outlet for the first fluid; a plurality of heat exchangers interposed radially interposed between the central manifold and the annular manifold; and a plurality of axial inlet manifolds communicating with the inlet for the second fluid, and a plurality of axial outlet manifolds communicating with the outlet for the second fluid, the axial inlet and outlet manifolds being interposed circumferentially between the heat exchangers. According to the invention, the assembly has an inlet chamber disposed at a first axial end of the heat exchangers and putting the inlet(s) for the second fluid into communication with at least a plurality of axial inlet manifolds.

Abstract: A decay heat removal system for a liquid metal reactor in which a decay heat exchanger (DHX) is installed concentrically with an intermediate heat exchanger (IHX) in the same cylinder which separates the DHX and IHX from the reactor pool fluid, and serves to remove the reactor core decay heat. The cylinder surrounds the IHX and DHX, and has an open top portion protruding out of the level of the fluid in a hot pool, a bottom portion connected to a cold pool and a guide pipe for allowing the passage of the fluid from the hot pool into the IHX. The decay heat removal system can remove decay heat immediately after occurrence of an accident, thereby improving the safety of a nuclear plant.

Abstract: A decay heat removal system for a liquid metal reactor, in which a decay heat exchanger (DHX) is installed concentrically with an intermediate heat-exchanger (IHX) in the same cylinder which separates the DHX and IHX from the reactor pool fluid, and serves to remove the reactor core decay heat. The cylinder surrounds the IHX and the DHX, and has an opened top portion protruded out of the level of the fluid in a hot pool, a bottom portion connected to a cold pool and a guide pipe for allowing the passage of the fluid from the hot pool into the IHX. The decay heat removal system can remove decay heat immediately after occurrence of an accident, thereby improves the safety of a nuclear plant.

Abstract: A variable-voltage variable-frequency power source for an electric motor that drives a re-circulation pump for a boiling water nuclear reactor. The power source has a semiconductor electric power converter and a speed controller for controlling the semiconductor electric power converter. When a part of the semiconductor electric power converter comes into an inoperative state, that part is electrically disconnected, and the variable-voltage variable-frequency power source temporarily stops outputting power, thereby idling the re-circulation pump. Thereafter, the power source re-starts outputting power before the re-circulation pump completely stops. Thus, the re-circulation pump keeps operating, without stopping.

Abstract: A support plate for retaining tube array spacing within a heat exchanger tube and shell structure. The support plate having a plurality of individual tube receiving apertures formed therein. Each aperture has at least three inwardly protruding members and bights are formed therebetween when the tube associated therewith is lodged in place to establish secondary fluid flow through the support plate. The inwardly protruding members terminate in flat lands that restrain but do not all contact the outer surface of the respective tube. These flat lands minimize fretting wear and eliminate potential gouging of the outer wall of the tube. The plate wall forming each aperture has an hourglass configuration which, inter alia, reduces pressure drop, turbulence and local deposition of magnetite and other particulates on the support plates.

Abstract: A support plate for retaining tube array spacing within a heat exchanger tube and shell structure. The support plate having a plurality of individual tube receiving aperture formed therein. Each apertures has at least three inwardly protruding members and bights are formed therebetween when the tube associated therewith is lodged in place to establish secondary fluid flow through the support plate. The inwardly protruding members terminate in flat lands that restrain but do not all contact the outer surface of the respective tube. These flat lands minimize fretting wear and eliminate potential gouging of the outer wall of the tube. The plate wall forming each aperture has an hourglass configuration which, inter alia, reduces pressure drop, turbulence and local deposition of magnetite and other particulates on the support plates.

Abstract: Passive emergency cooling in response to a loss of coolant accident (LOCA) in a PWR, having an integral reactor pressure vessel incorporating the steam generators and housed in a small high pressure containment vessel, is provided by circulating cooling water through the steam generators and heat exchangers in an external tank to cool the reactor vessel at a rate sufficient to lower the pressure in the reactor vessel below that in containment to reverse mass flow out of the reactor vessel and keep the reactor core covered without the addition of makeup water. Suppression tanks inside the small high pressure containment structure limit peak blowdown pressure in containment and provide flood-up water and gravity fed makeup water to cool the core. Diverse cooling is provided by natural circulation of air, and if needed, water, over the spherical containment structure.

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 support plate for retaining tube array spacing within a heat exchanger tube and shell structure. The support plate having a plurality of individual tube receiving apertures formed therein. Each apertures has at least three inwardly protruding members and bights are formed therebetween when the tube associated therewith is lodged in place to establish secondary fluid flow through the support plate. The inwardly protruding members terminate in flat lands that restrain but do not all contact the outer surface of the respective tube. These flat lands minimize fretting wear and eliminate potential gouging of the outer wall of the tube. The plate wall forming each aperture has an hourglass configuration which, inter alia, reduces pressure drop, turbulence and local deposition of magnetite and other particulates on the support plates.

Abstract: A thermal barrier for a nuclear reactor coolant pump includes a stack of pancake cooling coils encircling the pump shaft where it enters the pump chamber. This stack of coiling coils has an irregular peripheral surface formed by axially extending, diametrically opposed, inlet and outlet tubes which are circumferentially indexed for each pancake coil. The inner surface of a cylindrical cover has a complimentary inner peripheral surface formed by two sets of diametrically opposed cascaded steps so that the volume of the annulus between the coil stack and cover is minimized to reduce stratification of cooling water injected into the cover. A collar around the pump shaft at the opening in the end wall of the cover extends axially into the coil stack to prevent vortices produced by the spinning shaft from flowing across the end wall of the cover, while circumferentially spaced holes in the collar prevent significant alteration of the thermal conditions of the pancake coiling coils.

Abstract: A reactor core coolant flow rate control system for a BWR type nuclear power plant in which electric power is generated by a turbine-driven generator driven by a steam turbine rotating under the work of a main steam generated from a cooling water recirculated through a boiling water reactor includes an internal pump driving unit comprised of an electric motor driven by an electric power generated by the turbine-driven generator, a fluid coupling for transmitting an output torque of the electric motor and a variable-frequency generator whose rotation number is changed in accordance with the torque transmitted by way of the fluid coupling, a fluid coupling control signal generating unit for generating a fluid coupling control signal for the fluid coupling in response to at least one of deviation in a load and a rotation speed of the turbine-driven generator and deviation in a rotation speed of the internal pumps, and a plurality of internal pumps for recirculating the cooling water.

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 tank type nuclear reactor comprises an outer shielding wall structure, a reactor vessel installed in the shielding wall structure and provided with an inner sealed space in which a primary liquid coolant circulates, a reactor core disposed in the reactor vessel and charged with a number of fuel assemblies, a core support structure disposed to a bottom of the reactor vessel, a partition wall structure disposed on the core support structure defining the inner space of the reactor vessel into a hot pool region and a cold pool region, intermediate heat exchangers disposed in the reactor vessel for carrying out heat exchanging operation between the liquid coolant flow from the hot pool region and a secondary side heat medium, and electromagnetic pumps disposed in the reactor vessel for feeding the primary coolant into the core. The partition wall structure has a vertically cylindrical wall structure including a lower portion constituting a core tank portion surrounding an outer periphery of the core.

Abstract: Stator coils for linear flow electromagnetic induction pumps for pumping liquid metal circulating through a hydraulic system are provided with advantageous deployments of coil power terminals and leads.

Abstract: A nuclear reactor coolant pump has a casing defining an inlet nozzle for receiving a reactor coolant fluid, an outlet nozzle for discharging the fluid, and a passage interconnecting the inlet and outlet nozzles through which the fluid can flow in a main stream from the inlet nozzle to outlet nozzle. The pump also has a central rotor with one end disposed adjacent the annular passage of the casing and opposite bearings rotatably mounting the rotor to the casing. A motor is disposed about the rotor and between the bearings and is operable for rotatably driving the central rotor. An impeller is mounted to the one end of the rotor in communication with the annular passage and the flow of fluid therethrough. The impeller rotates with the rotor to create a lower pressure at the inlet nozzle than at the outlet nozzle for drawing the reactor coolant fluid into the casing through the inlet nozzle and discharging the fluid from the casing through the outlet nozzle.

Abstract: A recirculation system is disclosed for driving reactor coolant water in an annular downcomer defined between a reactor vessel and a core shroud spaced radially inwardly therefrom. The system supplies feedwater to the vessel and to a turbopump disposed inside the downcomer. The turbopump in accordance with one embodiment of the present invention includes a stationary axle and a pump impeller rotatably joined thereto and having an inlet end for receiving the coolant water from the downcomer. An annular plenum surrounds the impeller for channeling feedwater to a plurality of turbine blades joined to the impeller for rotating the impeller for driving the coolant water. The impeller is lubricated solely by the feedwater upon rotation of the impeller about the axle.

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: A magnet pump has a magnet coupling for magnetically coupling an inner ring yoke and an outer ring yoke so as to magnetically transmit a torque from driving part to driven part of the pump to rotate the driven part. The magnet pump comprises magnetized magnet pieces bonded to the outer peripheral surface of the inner ring yoke and magnetized magnet pieces bonded to the inner peripheral surface of the outer ring yoke; non-magnetic cylindrical covers covering the surface of the inner ring yoke carrying the magnet pieces and the surface of the outer ring yoke carrying the magnet pieces, respectively; and mold resin parts filling the gap between the surface of the inner ring yoke and the associated non-magnetic cylindrical cover and the gap between the surface of the outer yoke ring and the associated non-magnetic cylindrical cover.

Abstract: An autonomous, decentralized fast breeder reactor includes a single reactor main vessel which houses a plurality of small-size reactor subsystems each having a small-scale fast breeder reactor core, and a plurality steam generator subsystems. These subsystems function in an autonomous manner and are caused to undergo a heat transfer with one another by a coolant circulating naturally through the interior of the main vessel, thereby constructing a cooperatively operating system. Steam generated by the steam generators is introduced to a turbine system and utilized in generating electricity. The condensate from the turbines is cooled by a heat accumulating pool, and the heat is utilized in a separate system. The entire system is installed underground and use is made of the difference in elevation. Use also is made of solid bedrock to construct a housing facility for the reactor.

Abstract: Of the components making up the pump, one part including the bearing is removably assembled into the other part so that the bearing is received in the other part. This structure allows easy removal of the first part of the pump components from the second part for disassembly and for maintenance and inspection of the pump. The pump can also be reassembled with ease by inserting the first part into the other part.

Abstract: In a liquid metal cooled fast breeder nuclear reactor of the pool type, the hot and cold pools (13, 19) are separated by an intermediate plenum (24) which, under steady state conditions, encloses a volume of substantially stagnant liquid metal to form a thermal barrier between the hot and cold pools (13, 19). To avoid undesirably large temperature differentials developing for example in the event of large temperature excursions within the hot pool (13) as a result of a reactor trip, the intermediate plenum (24) is designed to permit, in such circumstances, rapid interchange of liquid metal coolant between the hot pool and the intermediate plenum, for example by way of a thermal siphon arrangement (30).

Abstract: A space-saving discharge collector 40 for the rotary pump 28 of a pool-type nuclear reactor 10. An annular collector 50 is located radially outboard for an impeller 44. The annular collector 50 as a closed outer periphery 52 for collecting the fluid from the impeller 44 and producing a uniform circumferential flow of the fluid. Turning means comprising a plurality of individual passageways 54 are located in an axial position relative to the annular collector 50 for receiving the fluid from the annular collector 50 and turning it into a substantially axial direction.

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

Abstract: In a known design of liquid metal cooled fast fission nuclear reactor, the primary pumps (22) plug into the outboard ends of the high pressure pipes (28), leading to the development of a vertical load which has to be supported by substantial additional structure to avoid subjecting the reactor diagrid (18) to significant bending moments. The invention resides in connecting the inboard ends of the high pressure pipes (28) to the diagrid (18) via spigot and socket joints (40) so that the pipes are not rigidly connected at either end. With this arrangement loads are developed at each end of the pipes which combine to produce radial reaction loads acting on smaller moment arms whereby the total moments imposed on the diagrid are reduced.

Abstract: The pump (8) comprises a vertical body (8a) and a discharge sphere (10) in its lower part. Discharge pipes (14) are connected to the sphere (10). The sphere (10) is suspended from the plating (4) of the reactor through a flexible metal strip (20). The sphere (10) is connected to the strip (20) in a region located below the region of connection between the strip (20) and the plating (4). The invention is in particular applicable to the primary pumps of fast neutron nuclear reactors of the integrated type.

Abstract: A liquid metal pump assembly is disclosed as being adapted to be disposed as one of a plurality of like pump assemblies in a continuous, closed array about a core of a nuclear reactor system. Each pump assembly comprises a pipe for receiving and directing a pumped, intermediate liquid metal through the pump assembly, and first and second duct modules disposed on either side of the pipe. Each duct module comprises primary ducts for receiving and directing a primary liquid metal in a first direction, and intermediate ducts in communication with the pipe for directing a first flow of the intermediate liquid metal therethrough in a second direction opposite to the first direction.

Abstract: A device for suspending a core cover from a sealing slab of a fast neutron nuclear reactor of the type comprising a vertically axed vessel structure filled with liquid metal, closed by the slab and containing the reactor core. The device comprises an upper row and a lower row of superimposed, generally flat, planar, metal plates enabling the rows to be joined to the slab and to the core cover, each row of plates defining a closed convex envelope. The plates are flexible in a direction radial relative to the envelope, while being rigid in a direction circumferential with respect to the envelope. The two rows of flexible plates are interconnected by a lattice of rigid bars in an "X" or "V" form. The upper row plates have upper edges rigidly fixed in position relative to the slab and lower edges rigidly fixed in position relative to the lattice. The lower row plates have upper edges rigidly fixed in position relative to the lattice and lower edges rigidly fixed in position relative to the core cover.

Abstract: An improved shut-down heat removal system for a liquid metal nuclear reactor of the type having a vessel for holding hot and cold pools of liquid sodium is disclosed herein. Generally, the improved system comprises a redan or barrier within the reactor vessel which allows an auxiliary heat exchanger to become immersed in liquid sodium from the hot pool whenever the reactor pump fails to generate a metal-circulating pressure differential between the hot and cold pools of sodium. This redan also defines an alternative circulation path between the hot and cold pools of sodium in order to equilibrate the distribution of the decay heat from the reactor core. The invention may take the form of a redan or barrier that circumscribes the inner wall of the reactor vessel, thereby defining an annular space therebetween.

Abstract: A liquid metal circulation system is disclosed which is suitable for use in connection with a nuclear reactor. The circulation system of the invention includes an electromagnetic pump having a central core body featuring a helically configured, six pole magnet, optionally directing flow to one or a series of flow couplers, which generates sufficient liquid metal flow to be used as the primary circulation means for the nuclear reactor. The increased safety, design simplicity, and efficiency of such circulation system overcomes many of the drawbacks of conventional circulation systems.

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: A system of generating electricity is disclosed. The system employs a new kind of swimming pool type nuclear reactor which is safe and can be made operable unattended but at the same time raises the mean pool temperature by forcing moderator-coolant-shield circulation. When the reactor is combined with an organic Rankine cycle engine, a significant improvement in efficiency of electricity generation can be obtained, making very small nuclear/electricity units economically viable.

Abstract: A pump assembly is disclosed for transferring the internal energy from a second or intermediate liquid metal to a first or primary liquid metal. The pump assembly comprises a pump duct for receiving the first liquid metal and a primary generator duct for receiving a first flow of the pumped, intermediate liquid metal. A first or main means in the illustrative form of a plurality of field coils generates and applies a main magnetic field through the pump and the primary generator ducts, whereby a first current flow is established through the pump and primary generator ducts and the primary liquid metal is pumped. An auxiliary generator duct receives a second flow of the pumped, intermediate liquid metal.

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

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

Abstract: 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: 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: Fast neutron nuclear reactor, which comprises a vessel containing a liquid cooling metal, a core immersed in this metal, the vessel having a flooring on which rests a structure for the core, said core being constituted by a juxtapositioning of assemblies fixed into the structure, the liquid cooling metal circulating in an upwards manner in the core, the liquid metal being called "cold liquid metal" before its circulation in the core and "hot liquid metal" after it has passed into the latter, wherein it comprises a fuel element storage structure, which is independent of the core structure and is arranged concentrically with respect to the latter and rests on the flooring, a circulation of cold liquid metal being ensured in the assembly by recovering leaks of the core structure.

Abstract: For holding the reactor core in the confining reactor vessel, a support is disclosed that is structurally independent of the vessel, that is dimensionally accurate and stable, and that comprises tandem tension linkages that act redundantly of one another to maintain stabilized core support even in the unlikely event of the complete failure of one of the linkages. The core support has a mounting platform for the reactor core, and unitary structure including a flange overlying the top edge of the reactor vessels, and a skirt and box beams between the flange and platform for establishing one of the linkages. A plurality of tension rods connect between the deck closing the reactor vessel and the platform for establishing the redundant linkage. Loaded Belleville springs flexibly hold the tension rods at the deck and separable bayonet-type connections hold the tension rods at the platform.

Abstract: A double tank type fast breeder reactor including a reactor vessel, and a tank of a secondary cooling system located outside the reactor vessel. The reactor vessel contains a core and installations of a primary cooling system, and the tank contains circulation pumps of the secondary cooling system and steam generators alternately located in the tank, and a body of sodium serving as a secondary coolant located at outer peripheries of the circulation pumps and steam generators. The tank includes an annular portion defined in the tank between walls of the tank and reactor vessel serving as a path of circulation of the secondary coolant.

Abstract: The present invention is intended to reduce thermosiphon effects within the annular space (6) situated between the pump casing (1) and the vertical wall (9) of an opening situated within the slab (3) covering the vessel for a nuclear reactor immersed in liquid sodium (4), with an inert gas (15) filling the space situated between the surface of the sodium and the bottom portion of said slab (3).The device to which the present invention pertains consists of a floating ring (7) placed around the pump casing (1) and a disc (8) which is integral with the vertical wall (9) of the opening situated within the slab (3). The shape of the aforementioned ring (7) and the shape of the aforementioned disc (8) are complementary with one another.Nuclear plants application.