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EP0206921B1 - Heat exchanger with coaxial u-tubes and intermediate circulation of neutral gas, and fast neutron reactor comprising such a heat exchanger - Google Patents

Heat exchanger with coaxial u-tubes and intermediate circulation of neutral gas, and fast neutron reactor comprising such a heat exchanger Download PDF

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Publication number
EP0206921B1
EP0206921B1 EP19860401303 EP86401303A EP0206921B1 EP 0206921 B1 EP0206921 B1 EP 0206921B1 EP 19860401303 EP19860401303 EP 19860401303 EP 86401303 A EP86401303 A EP 86401303A EP 0206921 B1 EP0206921 B1 EP 0206921B1
Authority
EP
European Patent Office
Prior art keywords
fluid
heat
tubes
heat exchanger
transfer fluid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19860401303
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German (de)
French (fr)
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EP0206921A1 (en
Inventor
Zéphyr Tilliette
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Original Assignee
Commissariat a lEnergie Atomique CEA
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Publication of EP0206921A1 publication Critical patent/EP0206921A1/en
Application granted granted Critical
Publication of EP0206921B1 publication Critical patent/EP0206921B1/en
Expired legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
    • F28D7/10—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged one within the other, e.g. concentrically
    • F28D7/14—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged one within the other, e.g. concentrically both tubes being bent
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
    • F22B1/06—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being molten; Use of molten metal, e.g. zinc, as heat transfer medium
    • F22B1/063—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being molten; Use of molten metal, e.g. zinc, as heat transfer medium for metal cooled nuclear reactors
    • F22B1/066—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being molten; Use of molten metal, e.g. zinc, as heat transfer medium for metal cooled nuclear reactors with double-wall tubes having a third fluid between these walls, e.g. helium for leak detection
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
    • F28D7/06—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits having a single U-bend
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F1/00—Tubular elements; Assemblies of tubular elements
    • F28F1/003—Multiple wall conduits, e.g. for leak detection
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
    • F28F9/005—Other auxiliary members within casings, e.g. internal filling means or sealing means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
    • F28D2021/0019—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for
    • F28D2021/0054—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for for nuclear applications

Definitions

  • the present invention relates to a heat exchanger comprising coaxial U-shaped tubes between which a neutral gas such as helium flows.
  • the invention also relates to the application of such an exchanger, in the form of steam generators, to different types of fast neutron nuclear reactors cooled by a heat transfer fluid which may be liquid sodium.
  • sodium / water vapor generators are "critical" components, due to the violent chemical reaction that can occur if sodium and water come into contact and the severity of the exchanges. sodium / water-steam thermal.
  • Document GB-A-768 264 describes a heat exchanger comprising a bundle of double U-shaped tubes placed in an enclosure containing a heating liquid. An intermediate fluid transmits the heat carried by the heating liquid to the heated fluid circulating in the interior tubes.
  • this exchanger is not designed to be placed in a nuclear reactor vessel.
  • the present invention specifically relates to a sodium / water heat exchanger having both a mechanical reliability and a functional reliability high enough that one can fearlessly consider the possible establishment of this heat exchanger, in the form of a steam generator, directly in the tank of an integrated type fast neutron nuclear reactor.
  • the application of the heat exchanger according to the invention is however not limited to reactors of this type and can in particular extend to fast neutron reactors of the loop type, in which the steam generators are placed in tanks separate from the main tank containing the reactor core.
  • this heat exchanger is characterized by its great simplicity and by the absence of a rigid connection between the internal tubes and the external tubes of the bundle of U-shaped tubes. This provides high mechanical reliability since the stresses due to differential expansions are avoided.
  • the ferrules surrounding the vertical branches of the bundle have main sodium entry windows placed above a normal level of sodium in the tank and auxiliary entry windows of sodium placed below a minimum level of sodium in the tank, each ferrule being provided with a bell fixed above the main entry windows and immersed in sodium to a level below said minimum level, to constitute a sodium supply siphon for this shell.
  • the outer tubes are smooth, the inner tubes being provided on their outer surface with centering pins and, in the ascending branch of the bundle, longitudinal or helical fins ensuring both an increase in heat exchange in this branch in order to compensate for the decrease in the temperature difference between heating and heated fluids and to distribute the boiling of water between the two branches and the maintenance of the inner tubes in the outer tubes.
  • the water inlet and outlet chambers are placed laterally with respect to the gas inlet and outlet chambers and separated from the latter by plates with water tubes / substantially vertical gases, the ends of the inner tubes fixed to these water / gas tube plates comprising horizontal parts, the gas inlet and outlet chambers being closed at their upper end by removable covers and the inlet chambers and water outlet being closed by removable covers placed opposite the water / gas tube plates.
  • the heat exchanger according to the invention comprises at least one tube opening into the water inlet chamber and at least one tube opening into the water outlet chamber, these tubes being able to be connected to a circuit. of external water by means of closing means making it possible to isolate the exchanger with respect to this circuit and comprising means for injecting a drain gas capable of driving the water out of the exchanger.
  • the gas / sodium tube plates are preferably fixed on a horizontal support piece surrounding said ferrules, this support piece being suitable to rest on a slab closing the tank, to ensure the support of the exchanger. r.
  • a subject of the invention is also the application of such a heat exchanger, in the form of a steam generator, to a fast-type nuclear reactor of integrated type and to a fast-type neutron reactor of the loop type.
  • the heat exchanger 10 shown in FIG. 1 comprises a bundle of double U-shaped tubes 12, only one of these double tubes being shown on a larger scale.
  • Each of the double U-shaped tubes 12 comprises an inner tube 14 inside which circulates water, then steam, and an outer tube 16 delimiting with the inner tube 14 an annular space 18 in which circulates a neutral gas such than helium.
  • the appreciable play existing between the interior and exterior tubes and the absence of concentricity requirement allows the bending of these double tubes.
  • Each of the double tubes 12 of the bundle comprises a vertical branch with descending heated fluid 12a, a vertical branch with ascending heated fluid 12b and a lower curved part 12c joining the vertical branches.
  • the upper ends of the descending and ascending branches of the outer tubes 16 are tightly fixed on two horizontal tube plates 20a and 20b, called gas / sodium tube plates, located side by side and at the same level.
  • These tube plates 20a and 20b rest on a horizontal support plate 22, respectively by means of two skirts 24a and 24b.
  • the support plate 22 rests itself, by means of a part 26, on a closing slab 28 of a tank 30, in which the double tubes 12 plunge. More precisely, the part 26 rests on the slab 28 at the periphery an opening 32 formed therein and through which the double tubes 12 of the exchanger plunge into the liquid sodium 34 contained in the tank 30.
  • the tube plates 20a and 20b constitute the lower walls of a gas inlet chamber 36a and a gas outlet chamber 36b respectively.
  • a gas inlet pipe 38a and a gas outlet pipe 38b open into the chambers 36a and 36b respectively.
  • each of the chambers 36a and 36b is closed by a removable cover 40a and 40b respectively. The dismantling of these covers makes it possible to inspect the tube plates 20a and 20b.
  • the upper ends of the descending and ascending branches of the inner tubes 14 freely pass through the tube plates 20a and 20b and are folded at 90 ° inside the chambers 36a and 36b, to end in substantially horizontal parts 14a and 14b.
  • the ends of these horizontal parts 14a and 14b of the inner tubes 14 are tightly fixed on vertical tube plates 42a and 42b, called water / gas tube plates, constituting a part of the side wall of the chambers 36a and 36b respectively.
  • the inner tubes 14 open respectively into a water inlet chamber 44a and into a water-vapor outlet chamber44b.
  • a water inlet pipe 46a equipped with a valve 48a opens into the chamber 44a.
  • a water-vapor outlet pipe 46b equipped with a valve 48b opens into the steam outlet chamber 44b.
  • Pipes 50a and 50b are connected to the pipes 46a and 46b, between the valves 48a and 48b and the chambers 44a and 44b respectively. These pipes 50a and 50b are used to connect the steam generator to a circuit making it possible to inject a drain gas into the interior tubes 14.
  • Each of the chambers 44a and 44b is closed off by a removable cover 52a and 52b respectively, placed opposite the corresponding tube plate 42a, 42b.
  • each of the ferrules 54a and 54b comprises main entry windows 56a and 56b. These windows are placed at a level as close as possible to the tube plates 20a and 20b, so that the heat exchange between the liquid sodium circulating around the bundle of double tubes 12 and the steam water circulating in the internal tubes 14 s' performs over as large an area as possible.
  • the windows 56a and 56b are placed just below an adapter piece 58 surrounding the ferrules 54a and 54b at the level of the slab 28, this piece 58 being suspended from the support plate 22.
  • the rise of liquid sodium 34 to the main entrance windows 56a and 56b is obtained by creating around each of the ferrules 54a and 54b a siphon effect, by means of two bells 60a and 60b respectively fixed to the ferrules 54a and 54b just above windows 56a and 56b.
  • the bells 60a and 60b immerse in the liquid sodium 34 to a level below the minimum level N 2 of the sodium in the tank.
  • each of the ferrules 54a and 54b further comprises auxiliary calibrated entry windows 62a and 62b allowing downward circulation of sodium inside the ferrules by natural convection if the circulation pumps stop.
  • the ferrules 54a and 54b are open at their lower ends, which are situated at the junction of the vertical branches 12a and 12b of the double tubes with the curved lower part 12c.
  • the ferrules 54a and 54b are tightly fixed on a transition piece 64.
  • the periphery of this piece 64 cooperates by a system of tightness 66 with a gas bell with a step 68 separating inside the tank 30 the hot sodium admitted into the exchanger 10 through the inlet windows 56a and 56b from the cold sodium exiting through the lower end of the ferrules 54a and 54b.
  • the double tubes 12 easily absorb the consequences of small temperature differences between the descending and ascending branches.
  • the temperatures of the tubes 12 of each branch are indeed very close due to the moderate exchange coefficient by gas convection.
  • the outer tubes 16 are smooth and expand freely in the vertical direction from the tube plates 20a and 20b.
  • the descending branches and the curved lower parts of the inner tubes 14 are also smooth, and only have spaced centering lugs 70 which allow the inner tubes to be held correctly in the outer tubes.
  • the inner tubes 14 can also be smooth and provided with centering lugs on their outer faces. However, they preferably have on their external faces longitudinal or helical fins 72 simultaneously ensuring the centering of the inner tubes in the outer tubes and a more efficient heat exchange, in order to balance the heat powers exchanged and to distribute the boiling of the 'water on both branches.
  • the inner tubes 14 are of small diameter and moderate thickness, which gives them good flexibility. This flexibility as well as the annular space which they have inside the external tubes also allows them to escape the transverse or horizontal stresses of expansion.
  • the vertical differential expansion between the branches of the inner tubes is absorbed by the horizontal parts 14a and 14b of the inner tubes 14.
  • the positioning of the double tubes 12 of the bundle is conventionally ensured by horizontal grids 74.
  • the grids 74 located at the bottom of the ferrules 54a and 54b provide guidance lateral of the tubes 12, while allowing a certain transverse flexibility of the tubes, that is to say a deformation of the latter in the plane passing through the axes of the descending 12a and rising 12b branches of the tubes 12. This configuration allows take into account possible differences in transverse expansion between the branches of the tubes at the bottom of the exchanger.
  • one or more devices 76 are provided inside the tank 30 for guiding the ferrules 54a and 54b, that is to say preventing their horizontal displacement, while allowing the vertical expansion of these ferrules by compared to the tank.
  • the sodium 34 circulates from bottom to top inside the ferrules 54a and 54b, between the inlet windows 56a and the lower ends. Ferrules. It enters at a temperature of around 550 ° C and comes out at a temperature of around 400 ° C.
  • the water constituting the secondary fluid of the generator enters the internal tubes 14 through the inlet chamber (s) 44a, to exit through the chambers 44b in the vapor state.
  • the inlet and outlet temperatures of water and steam are approximately 250 ° C and approximately 500 ° C, respectively.
  • the water / vapor pressure is also slightly lower than that of helium, so that the inner tubes are only stressed by a very small pressure difference. This characteristic virtually eliminates any possibility of water / vapor leakage to sodium and therefore constitutes a guarantee of high functional reliability.
  • the helium of the intermediate circuit enters the inter-tube space 18 through the chamber 36a at a temperature close to 250 ° C, to exit through the chamber 36b at a temperature of about 520 ° C. Its pressure is moderate and is limited to approximately 7 MPa. The flow of helium is therefore in the same direction as that of water.
  • the heat exchange between water and sodium is therefore carried out cocurrently in the descending branches 12a of the tubes and countercurrently in the ascending branches 12b.
  • the presence of the intermediate gas makes it possible to admit much greater temperature differences than in two-fluid heat exchangers since the intermediate gas then serves as a thermal buffer.
  • the helium circulating in the inter-tube space 18 constitutes an effective means of controlling the tubes of the bundle, all the more so since its volume is low due to a possible concept of a loop. compact helium located near the reactor and associated with each steam generator.
  • the arrangement of the chambers 44a and 44b laterally with respect to the whole of the heat exchanger avoids the presence of a large volume of water directly above the bundle of tubes, which is more satisfactory from a safety point of view.
  • the water inlet and outlet chambers could be placed immediately above the helium inlet and outlet chambers, by fitting these chambers with access covers placed laterally.
  • the inner tubes 14 should have a helical shape in the gas inlet and outlet chambers, in order to compensate for the vertical differential expansions.
  • heat exchange modules such as the module described above with reference to FIG. 1 can be placed side by side to constitute the exchanger itself.
  • the sodium / water exchanger with double U-tubes described above with reference to FIGS. 1 and 2 can in particular be used as a steam generator and placed either in a satellite tank of the main tank of a fast neutron nuclear reactor of the type loop, either directly in the main reactor vessel. This latter use simplifies the installation and makes it more compact.
  • FIG. 3 The installation of a steam generator of the type described above with reference to FIGS. 1 and 2 directly in the main tank of an integrated type fast neutron nuclear reactor is illustrated in FIG. 3.
  • the vessel 30 constitutes the main vessel of an integrated type fast neutron nuclear reactor.
  • the core 78 of the reactor, the primary pumps 82 and the heat exchangers constituted here by steam generators 10 produced in accordance with the invention are placed directly inside the vessel 30.
  • the latter is also filled with liquid sodium 34 and closed at its upper end by the closing plate 28 to which the steam generators 10 are suspended.
  • the core 78 of the reactor rests in a known manner on the bottom of the tank 30 by a supply and support base 80.
  • the seal between the collectors 34a and 34b is obtained at the steam generators 10 by transition pieces 64 fixed in leaktight manner around the ferrules 54a and 54b and cooperating with the internal tank 68 by gas bell sealing systems 66.
  • At least one device 76 is provided in the vicinity of the lower end of each of the steam generators, for horizontally holding the ferrules 54a and 54b, while leaving them free to expand vertically.
  • the sodium 34 crosses from bottom to top the core 78 of the reactor, to take part of the heat released by the fission reaction.
  • the sodium thus reheated enters the steam generators 10 through the inlet windows 56a and 56b (FIGS. 1 and 2) and circulates from bottom to top inside the ferrules 54a and 54b, around the double tubes of the bundle.
  • the cooled sodium exits into the cold collector 34b through the lower end of the ferrules 54a and 54b, before being taken up by the pumps, which discharge it into the supply bed 80 by pipes 84.
  • Each steam generator 10 can be in the form of separate modules, or in groups of two modules, which makes it possible to make the crossings of the slab 28 circular.
  • auxiliary inlet windows 62a and 62b (FIGS. 1 and 2) on the steam generators 10 enables them to perform the functions of cooling exchangers of the reactor when stopped, which allows to do without the specialized loops usually used.
  • the reduction in reactor cost brought about by the elimination of the sodium intermediate circuit is further increased by this disappearance.
  • FIG. 4 represents another application of the heat exchanger described above with reference to FIGS. 1 and 2, in the case where it constitutes a steam generator 10 placed in an annex tank 30 ′ distinct from the main tank (not shown) containing the core of a fast neutron nuclear reactor.
  • the tank 30 ' is suspended from a slab 28 on which the steam generator 10 also rests. More precisely, the slab 28 has an opening 32 at the periphery of which bears an annular piece 26 to which the tank 30 is suspended '.
  • the plate 22 of the steam generator rests directly on the part 26.
  • the transition piece 64 is tightly connected to the vertical wall of the tank 30, by means of a gas bell sealing system 66.
  • a sodium inlet pipe 90 coming from the main tank of the reactor opens into the tank 30 above the transition piece 64 and a return pipe 92 opens into the tank 30 below the transition piece, to bring the sodium back to the main tank, under the action of a pump (not shown).
  • connecting pipes 86 pass through the plate 22 to open into the atmosphere of neutral gas overhanging the sodium inside the tank 30 '. These pipes 86 allow this atmosphere to be controlled.
  • a drain pipe 88 can also be provided at the bottom of the tank 30 '.
  • At least one guide device 76 is fixed to the wall of the tank 30 'to horizontally hold the lower part of the ferrules 54a and 54b.

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  • Thermal Sciences (AREA)
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  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
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  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Description

La présente invention a pour objet un échangeur de chaleur comprenant des tubes en U coaxiaux entre lesquels circule un gaz neutre tel que de l'hélium. L'invention concerne également l'application d'un tel échangeur, sous la forme de générateurs de vapeur, à différents types de réacteurs nucléaires à neutrons rapides refroidis par un fluide caloporteur qui peut être du sodium liquide.The present invention relates to a heat exchanger comprising coaxial U-shaped tubes between which a neutral gas such as helium flows. The invention also relates to the application of such an exchanger, in the form of steam generators, to different types of fast neutron nuclear reactors cooled by a heat transfer fluid which may be liquid sodium.

Dans les réacteurs nucléaires à neutrons rapides, les générateurs de vapeur sodium/eau constituent des composants « critiques •, en raison de la réaction chimique violente qui risque de se produire si le sodium et l'eau viennent en contact et de la sévérité des échanges thermiques sodium/eau-vapeur.In fast neutron nuclear reactors, sodium / water vapor generators are "critical" components, due to the violent chemical reaction that can occur if sodium and water come into contact and the severity of the exchanges. sodium / water-steam thermal.

C'est pour cette raison que dans les réacteurs nucléaires à neutrons rapides de type intégré, dans lesquels l'ensemble du circuit primaire est disposé à l'intérieur d'une même cuve, on a recours à un circuit intermédiaire de sodium placé entre des échangeurs sodium/sodium internes à la cuve et des générateurs de vapeur sodium/eau placés à l'extérieur de cette dernière. Cette disposition a pour but d'éviter qu'une éventuelle réaction sodium/eau à l'intérieur des générateurs de vapeur ne se répercute jusqu'au coeur du réacteur. Il est certain que la présence d'un tel circuit intermédiaire de sodium est pénalisante à la fois du point de vue du coût de l'installation et du point de vue de l'efficacité thermodynamique du réacteur.It is for this reason that in fast integrated neutron nuclear reactors, in which the entire primary circuit is placed inside the same vessel, an intermediate sodium circuit is used placed between sodium / sodium exchangers internal to the tank and sodium / water steam generators placed outside the latter. The purpose of this arrangement is to prevent a possible sodium / water reaction inside the steam generators from passing through to the reactor core. It is certain that the presence of such an intermediate sodium circuit is penalizing both from the point of view of the cost of the installation and from the point of view of the thermodynamic efficiency of the reactor.

En conséquence, l'existence d'un échangeur de chaleur sodium/eau pouvant le cas échéant être implanté directement dans la cuve du réacteur grâce à une grande fiabilité mécanique et fonctionnelle éliminant pratiquement toute possibilité de fuite de l'eau ou de la vapeur vers le sodium, permettrait de diminuer de façon sensible le coût de ces réacteurs et d'en améliorer l'efficacité thermodynamique.Consequently, the existence of a sodium / water heat exchanger which can if necessary be installed directly in the reactor vessel thanks to a high mechanical and functional reliability eliminating practically any possibility of leakage of water or steam to sodium would significantly reduce the cost of these reactors and improve their thermodynamic efficiency.

Le document GB-A-768 264 décrit un échangeur de chaleur comportant un faisceau de doubles tubes en U placés dans une enceinte contenant un liquide chauffant. Un fluide intermédiaire transmet au fluide chauffé circulant dans les tubes intérieurs la chaleur véhiculée par le liquide chauffant. Cependant, cet échangeur n'est pas conçu pour être placé dans une cuve de réacteur nucléaire.Document GB-A-768 264 describes a heat exchanger comprising a bundle of double U-shaped tubes placed in an enclosure containing a heating liquid. An intermediate fluid transmits the heat carried by the heating liquid to the heated fluid circulating in the interior tubes. However, this exchanger is not designed to be placed in a nuclear reactor vessel.

La présente invention a précisément pour objet un échangeur de chaleur sodium/eau présentant à la fois une fiabilité mécanique et une fiabilité fonctionnelle assez élevées pour qu'on puisse envisager sans crainte l'implantation éventuelle de cet échangeur de chaleur, sous la forme d'un générateur de vapeur, directement dans la cuve d'un réacteur nucléaire à neutrons rapides de type intégré. L'application de l'échangeur de chaleur selon l'invention n'est toutefois pas limitée aux réacteurs de ce type et peut notamment s'étendre aux réacteurs à neutrons rapides du type à boucles, dans lesquels les générateurs de vapeur sont placés dans des cuves distinctes de la cuve principale contenant le coeur du réacteur.The present invention specifically relates to a sodium / water heat exchanger having both a mechanical reliability and a functional reliability high enough that one can fearlessly consider the possible establishment of this heat exchanger, in the form of a steam generator, directly in the tank of an integrated type fast neutron nuclear reactor. The application of the heat exchanger according to the invention is however not limited to reactors of this type and can in particular extend to fast neutron reactors of the loop type, in which the steam generators are placed in tanks separate from the main tank containing the reactor core.

Conformément à l'invention, ce résultat est obtenu au moyen d'un échangeur de chaleur à circulation intermédiaire d'un premier fluide, comprenant :

  • - un faisceau de doubles tubes en U baignant dans un fluide caloporteur liquide chauffant, ce faisceau étant constitué de tubes intérieurs et de tubes extérieurs, et comportant deux branches rectilignes reliées par une partie inférieure cintrée ;
  • - une chambre d'entrée du premier fluide et une chambre de sortie du premier fluide, ces chambres étant délimitées à leur extrémité inférieure par une plaque à tubes premier fluide/sodium sur laquelle sont fixées de façon étanche les extrémités correspondantes des tubes extérieurs ;
  • - au moins une chambre d'entrée d'un fluide chauffé, tel que de l'eau et au moins une chambre de sortie dudit fluide chauffé séparées respectivement de la chambre d'entrée du premier fluide et de la chambre de sortie du premier fluide par une plaque à tubes fluide chauffé/premier fluide sur laquelle sont fixées de façon étanche les extrémités correspondantes des tubes intérieurs ;
According to the invention, this result is obtained by means of a heat exchanger with intermediate circulation of a first fluid, comprising:
  • - A bundle of double U-shaped tubes bathed in a heating liquid coolant, this bundle being made up of inner tubes and outer tubes, and comprising two rectilinear branches connected by a curved lower part;
  • - an inlet chamber for the first fluid and an outlet chamber for the first fluid, these chambers being delimited at their lower end by a plate of first fluid / sodium tubes to which the corresponding ends of the outer tubes are fixed in leaktight fashion;
  • - at least one inlet chamber for a heated fluid, such as water and at least one outlet chamber for said heated fluid, separated respectively from the inlet chamber of the first fluid and from the outlet chamber of the first fluid by a heated fluid / first fluid tube plate on which the corresponding ends of the inner tubes are fixed in a sealed manner;

caractérisé en ce que le premier fluide est un gaz, l'échangeur étant apte à être monté dans une cuve contenant le fluide caloporteur, de telle sorte que les tubes en U plongent dans ce fluide et présentent chacun une branche verticale à fluide chauffé descendant et une branche verticale à flùide chauffé ascendant ;

  • - deux viroles entourant respectivement chacune des branches verticales du faisceau, ces viroles étant fixées aux plaques à tubes gaz/fluide caloporteur, ouvertes à leurs extrémités inférieures et munies de fenêtres d'entrée de fluide caloporteur à leurs extrémités supérieures ;
  • - une pièce de transition fixée aux viroles en dessous des fenêtres d'entrée de fluide caloporteur, pour séparer dans ladite cuve le fluide caloporteur entrant dans l'échangeur par les fenêtres d'entrée du fluide caloporteur sortant par les extrémités inférieures des viroles.
characterized in that the first fluid is a gas, the exchanger being able to be mounted in a tank containing the heat transfer fluid, so that the U-shaped tubes plunge into this fluid and each have a vertical branch with heated fluid descending and a vertical branch with rising heated fluid;
  • - Two ferrules respectively surrounding each of the vertical branches of the bundle, these ferrules being fixed to the gas / heat transfer fluid tube plates, open at their lower ends and provided with heat transfer fluid inlet windows at their upper ends;
  • - A transition piece fixed to the ferrules below the heat transfer fluid inlet windows, for separating into said tank the heat transfer fluid entering the exchanger through the inlet windows of the heat transfer fluid exiting through the lower ends of the ferrules.

La structure de cet échangeur de chaleur se caractérise par sa grande simplicité et par l'absence de liaison rigide entre les tubes internes et les tubes externes du faisceau des tubes en U. On obtient ainsi une haute fiabilité mécanique puisque les sollicitations dues aux dilatations différentielles sont évitées.The structure of this heat exchanger is characterized by its great simplicity and by the absence of a rigid connection between the internal tubes and the external tubes of the bundle of U-shaped tubes. This provides high mechanical reliability since the stresses due to differential expansions are avoided.

De plus, la circulation intermédiaire d'un gaz chimiquement neutre tel que l'hélium, qui présente une bonne efficacité thermique et des effets réduits sur les structures, permet d'assurer une séparation dynamique entre l'eau et le sodium tout en assurant le transfert thermique entre ces deux fluides. Ainsi, dans le cas d'une fuite éventuelle d'eau ou de vapeur, celle-ci est fortement diluée et entraînée par le gaz, ce qui permet son élimination par un dispositif extérieur de traitement et de séchage. De ce point de vue, l'adoption d'une pression dans le circuit eau/vapeur légèrement inférieure à celle de l'hélium élimine pratiquement toutes possibilités de fuites de l'eau ou de la vapeur vers le sodium.In addition, the intermediate circulation of a chemically neutral gas such as helium, which has good thermal efficiency and reduced effects on the structures, makes it possible to ensure a dynamic separation between water and sodium while ensuring the heat transfer between these two fluids. Thus, in the event of a possible leak of water or vapor, this is strongly diluted and entrained by the gas, which allows its elimination by an external treatment and drying device. From this point of view, the adoption of a pressure in the water / vapor circuit slightly lower than that of helium virtually eliminates any possibility of leakage of water or steam to sodium.

Il faut encore noter que la grande longueur d'échange permise par la configuration en U des tubes de l'échangeur selon l'invention permet d'avoir recours à un débit de gaz intermédiaire relativement faible qui peut être obtenu au moyen d'un circuit compact. De ce fait, les conséquences d'une éventuelle fuite importante vers le sodium se trouvent limitées en raison du faible volume de gaz intermédiaire concerné.It should also be noted that the long exchange length allowed by the U-shaped configuration of the tubes of the exchanger according to the invention makes it possible to have recourse to a relatively low intermediate gas flow rate which can be obtained by means of a circuit. compact. Therefore, the consequences of a possible significant leak to sodium are limited due to the small volume of intermediate gas concerned.

Conformément à un mode de réalisation préféré de l'invention, les viroles entourant les branches verticales du faisceau présentent des fenêtres d'entrée principales de sodium placées au-dessus d'un niveau normal du sodium dans la cuve et des fenêtres d'entrée auxiliaires de sodium placées en dessous d'un niveau minimal du sodium dans la cuve, chaque virole étant munie d'une cloche fixée au-dessus des fenêtres d'entrée principales et plongeant dans le sodium jusqu'à un niveau inférieur audit niveau minimal, pour constituer un siphon d'alimentation en sodium de cette virole.In accordance with a preferred embodiment of the invention, the ferrules surrounding the vertical branches of the bundle have main sodium entry windows placed above a normal level of sodium in the tank and auxiliary entry windows of sodium placed below a minimum level of sodium in the tank, each ferrule being provided with a bell fixed above the main entry windows and immersed in sodium to a level below said minimum level, to constitute a sodium supply siphon for this shell.

De préférence, les tubes extérieurs sont lisses, les tubes intérieurs étant munis sur leur surface extérieure d'ergots de centrage et, dans la branche ascendante du faisceau, d'ailettes longitudinales ou hélicoïdales assurant à la fois une augmentation de l'échange thermique dans cette branche afin de compenser la diminution de l'écart de température entre fluides chauffant et chauffé et de répartir l'ébullition de l'eau entre les deux branches et le maintien des tubes intérieurs dans les tubes extérieurs.Preferably, the outer tubes are smooth, the inner tubes being provided on their outer surface with centering pins and, in the ascending branch of the bundle, longitudinal or helical fins ensuring both an increase in heat exchange in this branch in order to compensate for the decrease in the temperature difference between heating and heated fluids and to distribute the boiling of water between the two branches and the maintenance of the inner tubes in the outer tubes.

Toujours selon un mode de réalisation préféré de l'invention, les chambres d'entrée et de sortie d'eau sont placées latéralement par rapport aux chambres d'entrée et de sortie de gaz et séparées de ces dernières par des plaques à tubes eau/gaz sensiblement verticales, les extrémités des tubes intérieurs fixées sur ces plaques à tubes eau/gaz comportant des parties horizontales, les chambres d'entrée et de sortie de gaz étant obturées à leur extrémité supérieure par des couvercles amovibles et les chambres d'entrée et de sortie d'eau étant obturées par des couvercles amovibles placés en vis-à-vis des plaques à tubes eau/gaz.Still according to a preferred embodiment of the invention, the water inlet and outlet chambers are placed laterally with respect to the gas inlet and outlet chambers and separated from the latter by plates with water tubes / substantially vertical gases, the ends of the inner tubes fixed to these water / gas tube plates comprising horizontal parts, the gas inlet and outlet chambers being closed at their upper end by removable covers and the inlet chambers and water outlet being closed by removable covers placed opposite the water / gas tube plates.

De préférence, l'échangeur de chaleur selon l'invention comprend au moins une tubulure débouchant dans la chambre d'entrée d'eau et au moins une tubulure débouchant dans la chambre de sortie d'eau, ces tubulures pouvant être raccordées à un circuit d'eau externe par l'intermédiaire de moyens de fermeture permettant d'isoler l'échangeur par rapport à ce circuit et comprenant des moyens pour injecter un gaz de vidange apte à chasser l'eau hors de l'échangeur.Preferably, the heat exchanger according to the invention comprises at least one tube opening into the water inlet chamber and at least one tube opening into the water outlet chamber, these tubes being able to be connected to a circuit. of external water by means of closing means making it possible to isolate the exchanger with respect to this circuit and comprising means for injecting a drain gas capable of driving the water out of the exchanger.

De façon à permettre l'implantation de l'échangeur de chaleur à partir du haut à l'intérieur de la cuve, les plaques à tubes gaz/sodium sont fixées de préférence sur une pièce support horizontale entourant lesdites viroles, cette pièce support étant apte à reposer sur une dalle de fermeture de la cuve, pour assurer le supportage de l'échangeur. r.In order to allow the installation of the heat exchanger from the top inside the tank, the gas / sodium tube plates are preferably fixed on a horizontal support piece surrounding said ferrules, this support piece being suitable to rest on a slab closing the tank, to ensure the support of the exchanger. r.

L'invention a également pour objet l'application d'un tel échangeur de chaleur, sous la forme d'un générateur de vapeur, à un réacteur nucléaire à neutrons rapides de type intégré et à un réacteur à neutrons rapides du type à boucles.A subject of the invention is also the application of such a heat exchanger, in the form of a steam generator, to a fast-type nuclear reactor of integrated type and to a fast-type neutron reactor of the loop type.

On décrira maintenant, à titre d'exemple non limitatif, un mode de réalisation préféré d'un échangeur de chaleur conforme à l'invention ainsi que deux applications de cet échangeur dans des réacteurs nucléaires à neutrons rapides de types différents, en se référant aux dessins annexés dans lesquels :

  • - la figure 1 est une vue de face, en coupe longitudinale schématique, d'un échangeur de chaleur conforme à l'invention, sur laquelle un seul double tube du faisceau de tubes en U a été représenté à plus grande échelle, pour faciliter la . compréhension ;
  • - la figure 2 est une vue en coupe longitudinale à plus grande échelle de la partie supérieure de l'échangeur de chaleur de la figure 1 ;
  • - la figure 3 est une vue en coupe verticale schématique de la cuve d'un réacteur nucléaire à neutrons rapides de type intégré dans laquelle est placé un générateur de vapeur conforme à l'invention, et
  • - la figure 4 représente une cuve autonome contenant un générateur de vapeur conforme à l'invention et prévue pour être reliée à la cuve principale d'un réacteur nucléaire à neutrons rapides du type à boucles.
We will now describe, by way of nonlimiting example, a preferred embodiment of a heat exchanger according to the invention as well as two applications of this exchanger in fast neutron nuclear reactors of different types, with reference to annexed drawings in which:
  • - Figure 1 is a front view, in schematic longitudinal section, of a heat exchanger according to the invention, on which a single double tube of the U-shaped tube bundle has been shown on a larger scale, to facilitate the . comprehension ;
  • - Figure 2 is a longitudinal sectional view on a larger scale of the upper part of the heat exchanger of Figure 1;
  • FIG. 3 is a schematic vertical sectional view of the vessel of an integrated type fast neutron nuclear reactor in which a steam generator according to the invention is placed, and
  • - Figure 4 shows a self-contained tank containing a steam generator according to the invention and intended to be connected to the main tank of a fast neutron nuclear reactor of the loop type.

Conformément à l'invention, l'échangeur de chaleur 10 représenté sur la figure 1 comprend un faisceau de doubles tubes en U 12, un seul de ces doubles tubes étant représenté à plus grande échelle. Chacun des doubles tubes en U 12 comprend un tube intérieur 14 à l'intérieur duquel circule de l'eau, puis de la vapeur, et un tube extérieur 16 délimitant avec le tube intérieur 14 un espace annulaire 18 dans lequel circule un gaz neutre tel que de l'hélium. Le jeu appréciable existant entre les tubes intérieur et extérieur et l'absence d'exigence de concentricité permet le cintrage de ces doubles tubes.According to the invention, the heat exchanger 10 shown in FIG. 1 comprises a bundle of double U-shaped tubes 12, only one of these double tubes being shown on a larger scale. Each of the double U-shaped tubes 12 comprises an inner tube 14 inside which circulates water, then steam, and an outer tube 16 delimiting with the inner tube 14 an annular space 18 in which circulates a neutral gas such than helium. The appreciable play existing between the interior and exterior tubes and the absence of concentricity requirement allows the bending of these double tubes.

Chacun des doubles tubes 12 du faisceau comprend une branche verticale à fluide chauffé descendant 12a, une branche verticale à fluide chauffé ascendant 12b et une partie cintrée inférieure 12c joignant les branches verticales.Each of the double tubes 12 of the bundle comprises a vertical branch with descending heated fluid 12a, a vertical branch with ascending heated fluid 12b and a lower curved part 12c joining the vertical branches.

Les extrémités supérieures des branches descendante et ascendante des tubes extérieurs 16 sont fixées de façon étanche sur deux plaques à tubes horizontales 20a et 20b, dites plaques à tubes gaz/sodium, situées côte à côte et au même niveau. Ces plaques à tubes 20a et 20b reposent sur une plaque horizontale de supportage 22, respectivement par l'intermédiaire de deux jupes 24a et 24b. La plaque de supportage 22 repose elle-même, par l'intermédiaire d'une pièce 26, sur une dalle de fermeture 28 d'une cuve 30, dans laquelle plongent les doubles tubes 12. De façon plus précise, la pièce 26 repose sur la dalle 28 à la périphérie d'une ouverture 32 formée dans celle-ci et par laquelle les doubles tubes 12 de l'échangeur plongent dans le sodium liquide 34 contenu dans la cuve 30.The upper ends of the descending and ascending branches of the outer tubes 16 are tightly fixed on two horizontal tube plates 20a and 20b, called gas / sodium tube plates, located side by side and at the same level. These tube plates 20a and 20b rest on a horizontal support plate 22, respectively by means of two skirts 24a and 24b. The support plate 22 rests itself, by means of a part 26, on a closing slab 28 of a tank 30, in which the double tubes 12 plunge. More precisely, the part 26 rests on the slab 28 at the periphery an opening 32 formed therein and through which the double tubes 12 of the exchanger plunge into the liquid sodium 34 contained in the tank 30.

Les plaques à tubes 20a et 20b constituent les parois inférieures d'une chambre d'entrée de gaz 36a et d'une chambre de sortie de gaz 36b respectivement. Une tubulure d'entrée de gaz 38a et une tubulure de sortie de gaz 38b débouchent respectivement dans les chambres 36a et 36b. A leur extrémité supérieure, chacune des chambres 36a et 36b est obturée par un couvercle amovible 40a et 40b respectivement. Le démontage de ces couvercles permet d'inspecter les plaques à tubes 20a et 20b.The tube plates 20a and 20b constitute the lower walls of a gas inlet chamber 36a and a gas outlet chamber 36b respectively. A gas inlet pipe 38a and a gas outlet pipe 38b open into the chambers 36a and 36b respectively. At their upper end, each of the chambers 36a and 36b is closed by a removable cover 40a and 40b respectively. The dismantling of these covers makes it possible to inspect the tube plates 20a and 20b.

Les extrémités supérieures des branches descendante et ascendante des tubes intérieurs 14 traversent librement les plaques à tubes 20a et 20b et sont repliées à 90° à l'intérieur des chambres 36a et 36b, pour se terminer par des parties sensiblement horizontales 14a et 14b. Les extrémités de ces parties horizontales 14a et 14b des tubes intérieurs 14 sont fixées de façon étanche sur des plaques à tubes verticales 42a et 42b, dites plaques à tubes eau/gaz, constituant une partie de la paroi latérale des chambres 36a et 36b respectivement.The upper ends of the descending and ascending branches of the inner tubes 14 freely pass through the tube plates 20a and 20b and are folded at 90 ° inside the chambers 36a and 36b, to end in substantially horizontal parts 14a and 14b. The ends of these horizontal parts 14a and 14b of the inner tubes 14 are tightly fixed on vertical tube plates 42a and 42b, called water / gas tube plates, constituting a part of the side wall of the chambers 36a and 36b respectively.

Derrière les plaques à tubes 42a et 42b, les tubes intérieurs 14 débouchent respectivement dans une chambre d'entrée d'eau 44a et dans une chambre de sortie d'eau-vapeur44b. Une tubulure d'entrée d'eau 46a équipée d'une vanne 48a débouche dans la chambre 44a. De façon comparable, une tubulure de sortie d'eau-vapeur 46b équipée d'une vanne 48b débouche dans la chambre de sortie de vapeur 44b.Behind the tube plates 42a and 42b, the inner tubes 14 open respectively into a water inlet chamber 44a and into a water-vapor outlet chamber44b. A water inlet pipe 46a equipped with a valve 48a opens into the chamber 44a. Similarly, a water-vapor outlet pipe 46b equipped with a valve 48b opens into the steam outlet chamber 44b.

Des tuyauteries 50a et 50b sont raccordées sur les tubulures 46a et 46b, entre les vannes 48a et 48b et les chambres 44a et 44b respectivement. Ces tuyauteries 50a et 50b servent à raccorder le générateur de vapeur à un circuit permettant d'injecter un gaz de vidange dans les tubes intérieurs 14.Pipes 50a and 50b are connected to the pipes 46a and 46b, between the valves 48a and 48b and the chambers 44a and 44b respectively. These pipes 50a and 50b are used to connect the steam generator to a circuit making it possible to inject a drain gas into the interior tubes 14.

Chacune des chambres 44a et 44b est obturée par un couvercle amovible 52a et 52b respectivement, placé en vis-à-vis de la plaque à tubes 42a, 42b correspondante.Each of the chambers 44a and 44b is closed off by a removable cover 52a and 52b respectively, placed opposite the corresponding tube plate 42a, 42b.

La circulation du sodium liquide 34 autour des branches descendantes 12a et des branches ascendantes 12b du faisceau de doubles tubes 12 est canalisée au moyen de deux viroles 54a et 54b fixées respectivement aux plaques à tubes 20a et 20b et entourant respectivement chacune des branches verticales du faisceau.The circulation of liquid sodium 34 around the descending branches 12a and the ascending branches 12b of the bundle of double tubes 12 is channeled by means of two ferrules 54a and 54b fixed respectively to the tube plates 20a and 20b and respectively surrounding each of the vertical branches of the bundle .

A un niveau supérieur au niveau normal N1 de sodium liquide 34 dans la cuve 30, chacune des viroles 54a et 54b comprend des fenêtres d'entrée principales 56a et 56b. Ces fenêtres sont placées à un niveau aussi proche que possible des plaques à tubes 20a et 20b, afin que l'échange thermique entre le sodium liquide circulant autour du faisceau de doubles tubes 12 et l'eau vapeur circulant dans les tubes internes 14 s'effectue sur une surface aussi grande que possible. Dans l'exemple représenté sur la figure, les fenêtres 56a et 56b sont placées juste en dessous d'une pièce d'adaptation 58 entourant les viroles 54a et 54b au niveau de la dalle 28, cette pièce 58 étant suspendue à la plaque de supportage 22.At a level higher than the normal level N 1 of liquid sodium 34 in the tank 30, each of the ferrules 54a and 54b comprises main entry windows 56a and 56b. These windows are placed at a level as close as possible to the tube plates 20a and 20b, so that the heat exchange between the liquid sodium circulating around the bundle of double tubes 12 and the steam water circulating in the internal tubes 14 s' performs over as large an area as possible. In the example shown in the figure, the windows 56a and 56b are placed just below an adapter piece 58 surrounding the ferrules 54a and 54b at the level of the slab 28, this piece 58 being suspended from the support plate 22.

La montée du sodium liquide 34 jusqu'aux fenêtres d'entrée principales 56a et 56b est obtenue en créant autour de chacune des viroles 54a et 54b un effet de siphon, au moyen de deux cloches 60a et 60b respectivement fixées aux viroles 54a et 54b juste au-dessus des fenêtres 56a et 56b. Les cloches 60a et 60b plongent dans le sodium liquide 34 jusqu'à un niveau inférieur au niveau minimal N2 du sodium dans la cuve.The rise of liquid sodium 34 to the main entrance windows 56a and 56b is obtained by creating around each of the ferrules 54a and 54b a siphon effect, by means of two bells 60a and 60b respectively fixed to the ferrules 54a and 54b just above windows 56a and 56b. The bells 60a and 60b immerse in the liquid sodium 34 to a level below the minimum level N 2 of the sodium in the tank.

De préférence, approximativement au même niveau que l'extrémité inférieure des cloches 60a et 60b, chacune des viroles 54a et 54b comprend de plus des fenêtres d'entrée auxiliaires calibrées 62a et 62b autorisant une circulation descendante de sodium à l'intérieur des viroles par convection naturelle en cas d'arrêt des pompes de circulation.Preferably, approximately at the same level as the lower end of the bells 60a and 60b, each of the ferrules 54a and 54b further comprises auxiliary calibrated entry windows 62a and 62b allowing downward circulation of sodium inside the ferrules by natural convection if the circulation pumps stop.

Les viroles 54a et 54b sont ouvertes à leurs extrémités inférieures, qui sont situées au niveau de la jonction des branches verticales 12a et 12b des doubles tubes avec la partie inférieure cintrée 12c.The ferrules 54a and 54b are open at their lower ends, which are situated at the junction of the vertical branches 12a and 12b of the double tubes with the curved lower part 12c.

Dans leur partie centrale, c'est-à-dire bien en dessous des fenêtres 62a et 62b, les viroles 54a et 54b sont fixées de façon étanche sur une pièce de transition 64. La périphérie de cette pièce 64 coopère par un système d'étanchéité 66 à cloche de gaz avec un redan 68 séparant à l'intérieur de la cuve 30 le sodium chaud admis dans l'échangeur 10 par les fenêtres d'entrée 56a et 56b du sodium froid sortant par l'extrémité inférieure des viroles 54a et 54b.In their central part, that is to say well below the windows 62a and 62b, the ferrules 54a and 54b are tightly fixed on a transition piece 64. The periphery of this piece 64 cooperates by a system of tightness 66 with a gas bell with a step 68 separating inside the tank 30 the hot sodium admitted into the exchanger 10 through the inlet windows 56a and 56b from the cold sodium exiting through the lower end of the ferrules 54a and 54b.

En raison de leur forme en U, les doubles tubes 12 absorbent facilement les conséquences de faibles différences de température entre les branches descendante et ascendante. Les températures des tubes 12 de chaque branche sont en effet très voisines en raison du coefficient d'échange modéré par convection de gaz.Due to their U-shape, the double tubes 12 easily absorb the consequences of small temperature differences between the descending and ascending branches. The temperatures of the tubes 12 of each branch are indeed very close due to the moderate exchange coefficient by gas convection.

Les tubes extérieurs 16 sont lisses et se dilatent librement dans le sens vertical à partir des plaques à tubes 20a et 20b.The outer tubes 16 are smooth and expand freely in the vertical direction from the tube plates 20a and 20b.

Les branches descendantes et les parties inférieures cintrées des tubes intérieurs 14 sont également lisses, et ne comportent que des ergots de centrage espacés 70 qui permettent un maintien correct des tubes intérieurs dans les tubes extérieurs. Dans la branche ascendante du faisceau, les tubes intérieurs 14 peuvent également être lisses et munis d'ergots de centrage sur leurs faces externes. Toutefois, ils comportent de préférence sur leurs faces externes des ailettes longitudinales ou hélicoïdales 72 assurant simultanément le centrage des tubes intérieurs dans les tubes extérieurs et un échange thermique plus efficace, afin d'équilibrer les puissances thermiques échangées et de répartir l'ébullition de l'eau sur les deux branches.The descending branches and the curved lower parts of the inner tubes 14 are also smooth, and only have spaced centering lugs 70 which allow the inner tubes to be held correctly in the outer tubes. In the ascending branch of the bundle, the inner tubes 14 can also be smooth and provided with centering lugs on their outer faces. However, they preferably have on their external faces longitudinal or helical fins 72 simultaneously ensuring the centering of the inner tubes in the outer tubes and a more efficient heat exchange, in order to balance the heat powers exchanged and to distribute the boiling of the 'water on both branches.

En outre, les tubes intérieurs 14 sont de faible diamètre et d'épaisseur modérée, ce qui leur confère une bonne souplesse. Cette souplesse ainsi que l'espace annulaire dont ils disposent à l'intérieur des tubes extérieurs leur permet également d'échapper aux contraintes transversales ou horizontales de dilatation. La dilatation différentielle verticale entre les branches des tubes intérieurs est absorbée quant à elle par les parties horizontales 14a et 14b des tubes internes 14.In addition, the inner tubes 14 are of small diameter and moderate thickness, which gives them good flexibility. This flexibility as well as the annular space which they have inside the external tubes also allows them to escape the transverse or horizontal stresses of expansion. The vertical differential expansion between the branches of the inner tubes is absorbed by the horizontal parts 14a and 14b of the inner tubes 14.

A l'intérieur des viroles 54a et 54b, le positionnement des doubles tubes 12 du faisceau est assuré de manière classique par des grilles horizontales 74. Il est à noter que les grilles 74 situées à la partie inférieure des viroles 54a et 54b assurent un guidage latéral des tubes 12, tout en autorisant une certaine souplesse transversale des tubes, c'est-à-dire une déformation de ceux- ci dans le plan passant par les axes des branches descendantes 12a et montantes 12b des tubes 12. Cette configuration permet de prendre en compte les possibles différences de dilatation transversale entre les branches des tubes à la partie inférieure de l'échangeur.Inside the ferrules 54a and 54b, the positioning of the double tubes 12 of the bundle is conventionally ensured by horizontal grids 74. It should be noted that the grids 74 located at the bottom of the ferrules 54a and 54b provide guidance lateral of the tubes 12, while allowing a certain transverse flexibility of the tubes, that is to say a deformation of the latter in the plane passing through the axes of the descending 12a and rising 12b branches of the tubes 12. This configuration allows take into account possible differences in transverse expansion between the branches of the tubes at the bottom of the exchanger.

De préférence, un ou plusieurs dispositifs 76 sont prévus à l'intérieur de la cuve 30 pour assurer le guidage des viroles 54a et 54b, c'est-à-dire empêcher leur déplacement horizontal, tout en permettant la dilatation verticale de ces viroles par rapport à la cuve.Preferably, one or more devices 76 are provided inside the tank 30 for guiding the ferrules 54a and 54b, that is to say preventing their horizontal displacement, while allowing the vertical expansion of these ferrules by compared to the tank.

Le fonctionnement de l'échangeur de chaleur qui vient d'être décrit en se référant aux figures 1 et 2 est le suivant.The operation of the heat exchanger which has just been described with reference to Figures 1 and 2 is as follows.

Sous l'effet des pompes équipant le circuit primaire du réacteur dans lequel est placé l'échangeur 10, le sodium 34 circule de bas en haut à l'intérieur des viroles 54a et 54b, entre les fenêtres d'entrée 56a et les extrémités inférieures des viroles. Il entre à une température d'environ 550 °C et ressort à une température voisine de 400 °C.Under the effect of the pumps fitted to the primary circuit of the reactor in which the exchanger 10 is placed, the sodium 34 circulates from bottom to top inside the ferrules 54a and 54b, between the inlet windows 56a and the lower ends. ferrules. It enters at a temperature of around 550 ° C and comes out at a temperature of around 400 ° C.

Simultanément, l'eau constituant le fluide secondaire du générateur pénètre dans les tubes internes 14 par la ou les chambres d'entrée 44a, pour ressortir par les chambres 44b à l'état de vapeur. Les températures d'entrée et de sortie de l'eau et de la vapeur sont respectivement d'environ 250 °C et d'environ 500 °C. La pression de l'eau/vapeur est en outre légèrement inférieure à celle de l'hélium, de sorte que les tubes intérieurs ne sont sollicités que par une très faible différence de pression. Cette caractéristique élimine pratiquement toute possibilité de fuite d'eau/vapeur vers le sodium et constitue donc un gage de haute fiabilité fonctionnelle.Simultaneously, the water constituting the secondary fluid of the generator enters the internal tubes 14 through the inlet chamber (s) 44a, to exit through the chambers 44b in the vapor state. The inlet and outlet temperatures of water and steam are approximately 250 ° C and approximately 500 ° C, respectively. The water / vapor pressure is also slightly lower than that of helium, so that the inner tubes are only stressed by a very small pressure difference. This characteristic virtually eliminates any possibility of water / vapor leakage to sodium and therefore constitutes a guarantee of high functional reliability.

Enfin, l'hélium du circuit intermédiaire pénètre dans l'espace inter-tubes 18 par la chambre 36a à une température voisine de 250 °C, pour ressortir par la chambre 36b à une température d'environ 520 °C. Sa pression est modérée et se limite à environ 7 MPa. L'écoulement de l'hélium se fait donc dans le même sens que celui de l'eau.Finally, the helium of the intermediate circuit enters the inter-tube space 18 through the chamber 36a at a temperature close to 250 ° C, to exit through the chamber 36b at a temperature of about 520 ° C. Its pressure is moderate and is limited to approximately 7 MPa. The flow of helium is therefore in the same direction as that of water.

L'échange thermique entre l'eau et le sodium s'effectue donc à co-courant dans les branches descendantes 12a des tubes et à contre-courant dans les branches ascendantes 12b.The heat exchange between water and sodium is therefore carried out cocurrently in the descending branches 12a of the tubes and countercurrently in the ascending branches 12b.

Dans le cas d'un générateur de vapeur, une partie de la vaporisation s'effectue dans la branche descendante des tubes, ce qui est contraire à la pratique courante mais correspond cependant à certaines réalisations. Toutefois, une bonne stabilité peut être obtenue en jouant sur différents facteurs parmi lesquels on citera notamment la présence d'un diaphragme à forte perte de charge à l'entrée de chaque tube intérieur 14, et la possibilité de contrôler l'échange thermique par l'hélium, indépendamment des régimes d'écoulement de l'eau et du sodium.In the case of a steam generator, part of the vaporization takes place in the downward branch of the tubes, which is contrary to current practice but nevertheless corresponds to certain embodiments. However, good stability can be obtained by playing on different factors, among which we will cite in particular the presence of a diaphragm with a high pressure drop at the inlet of each inner tube 14, and the possibility of controlling the heat exchange by the helium, independently of the water and sodium flow regimes.

Grâce à l'échangeur de chaleur décrit, un échange thermique satisfaisant peut être obtenu entre le sodium et l'eau/vapeur, en faisant circuler l'hélium à un débit relativement faible. Il est à noter que l'échange thermique par l'hélium en circulation permet à la structure d'absorber l'écart de température important existant entre le sodium et l'eau à l'entrée de la branche descendante et d'éviter que les plaques à tubes sodium-hélium 20a et 20b et les tubes 14 et 16 ne soient soumis à des sollicitations anormales.Thanks to the heat exchanger described, a satisfactory heat exchange can be obtained between sodium and water / vapor, by circulating the helium at a relatively low rate. It should be noted that the heat exchange by the circulating helium allows the structure to absorb the large temperature difference existing between the sodium and the water at the entry of the descending branch and to prevent the sodium-helium tube plates 20a and 20b and tubes 14 and 16 are not subjected to abnormal stresses.

De façon générale, la présence du gaz intermédiaire permet d'admettre des écarts de température beaucoup plus importants que dans les échangeurs de chaleur à deux fluides puisque le gaz intermédiaire sert alors de tampon thermique.In general, the presence of the intermediate gas makes it possible to admit much greater temperature differences than in two-fluid heat exchangers since the intermediate gas then serves as a thermal buffer.

En plus de ces différentes fonctions, l'hélium en circulation dans l'espace inter-tubes 18 constitue un moyen de contrôle efficace des tubes du faisceau d'autant plus que son volume est faible en raison d'un concept possible d'une boucle d'hélium compacte située à proximité du réacteur et associée à chaque générateur de vapeur.In addition to these different functions, the helium circulating in the inter-tube space 18 constitutes an effective means of controlling the tubes of the bundle, all the more so since its volume is low due to a possible concept of a loop. compact helium located near the reactor and associated with each steam generator.

De plus, dans la configuration décrite en se référant aux figures 1 et 2, une isolation de l'échangeur par rapport au reste du circuit secondaire peut être obtenue facilement en fermant les vannes 48a et 48b. En cas d'incident rapidement détecté par le contrôle de la pureté du gaz et de sa pression, un gaz sous pression peut alors être injecté par la canalisation 50a pour vidanger les tubes intérieurs 14. La conception des chambres d'entrée et de sortie d'eau et de gaz permet en outre d'accéder facilement aux plaques à tubes correspondantes lorsqu'une intervention est nécessaire.In addition, in the configuration described with reference to Figures 1 and 2, insulation of the exchanger from the rest of the secondary circuit can be easily obtained by closing the valves 48a and 48b. In the event of an incident quickly detected by checking the purity of the gas and its pressure, a pressurized gas can then be injected through the pipe 50a to drain the interior tubes 14. The design of the inlet and outlet chambers d Furthermore, water and gas allow easy access to the corresponding tube plates when intervention is necessary.

En outre, il est à remarquer que la disposition des chambres 44a et 44b latéralement par rapport à l'ensemble de l'échangeur de chaleur évite la présence d'un volume important d'eau directement au-dessus du faisceau de tubes, ce qui est plus satisfaisant du point de vue de la sûreté. On pourrait toutefois placer les chambres d'entrée et de sortie de l'eau immédiatement au-dessus des chambres .d'entrée et de sortie d'hélium, en équipant ces chambres de couvercles d'accès placés latéralement. Dans ce cas, les tubes intérieurs 14 devraient présenter une forme en hélice dans les chambres d'entrée et de sortie de gaz, afin de compenser les dilatations différentielles verticales.In addition, it should be noted that the arrangement of the chambers 44a and 44b laterally with respect to the whole of the heat exchanger avoids the presence of a large volume of water directly above the bundle of tubes, which is more satisfactory from a safety point of view. However, the water inlet and outlet chambers could be placed immediately above the helium inlet and outlet chambers, by fitting these chambers with access covers placed laterally. In this case, the inner tubes 14 should have a helical shape in the gas inlet and outlet chambers, in order to compensate for the vertical differential expansions.

Il est à noter que pluqieurs modules d'échange de chaleur tels que le module décrit précédemment en se référant à la figure 1 peuvent être placés côte à côte pour constituer l'échangeur proprement dit.It should be noted that several heat exchange modules such as the module described above with reference to FIG. 1 can be placed side by side to constitute the exchanger itself.

L'échangeur sodium/eau à doubles tubes en U décrit précédemment en se référant aux figures 1 et 2 peut notamment être utilisé comme générateur de vapeur et placé soit dans une cuve satellite de la cuve principale d'un réacteur nucléaire à neutrons rapides du type à boucles, soit directement dans la cuve principale du réacteur. Cette dernière utilisation permet de simplifier l'installation et de la rendre plus compacte.The sodium / water exchanger with double U-tubes described above with reference to FIGS. 1 and 2 can in particular be used as a steam generator and placed either in a satellite tank of the main tank of a fast neutron nuclear reactor of the type loop, either directly in the main reactor vessel. This latter use simplifies the installation and makes it more compact.

La mise en place d'un générateur de vapeur du type décrit précédemment en se référant aux figures 1 et 2 directement dans la cuve principale d'un réacteur nucléaire à neutrons rapides de type intégré est illustrée par la figure 3.The installation of a steam generator of the type described above with reference to FIGS. 1 and 2 directly in the main tank of an integrated type fast neutron nuclear reactor is illustrated in FIG. 3.

Sur cette figure, la cuve 30 constitue la cuve principale d'un réacteur nucléaire à neutrons rapides de type intégré. En d'autres termes, le coeur 78 du réacteur, les pompes primaires 82 et les échangeurs de chaleur constitués ici par des générateurs de vapeur 10 réalisés conformément à l'invention sont placés directement à l'intérieur de la cuve 30. Celle-ci est en outre remplie de sodium liquide 34 et obturée à son extrémité supérieure par la dalle de fermeture 28 à laquelle sont suspendus les générateurs de vapeur 10.In this figure, the vessel 30 constitutes the main vessel of an integrated type fast neutron nuclear reactor. In other words, the core 78 of the reactor, the primary pumps 82 and the heat exchangers constituted here by steam generators 10 produced in accordance with the invention are placed directly inside the vessel 30. The latter is also filled with liquid sodium 34 and closed at its upper end by the closing plate 28 to which the steam generators 10 are suspended.

Le coeur 78 du réacteur repose de façon connue sur le fond de la cuve 30 par un sommier d'alimentation et de supportage 80. Un redan 68 que traversent les générateurs de vapeur 10 et les pompes 82 délimite à l'intérieur de la cuve 30 un collecteur chaud 34a situé principalement au-dessus du coeur 78 et un collecteur annulaire froid 34b situé à la périphérie de celui-ci. Comme on l'a décrit précédemment en se référant à la figure 1, l'étanchéité entre les collecteurs 34a et 34b est obtenue au niveau des générateurs de vapeur 10 par des pièces de transition 64 fixées de façon étanche autour des viroles 54a et 54b et coopérant avec la cuve interne 68 par des systèmes d'étanchéité à cloches de gaz 66.The core 78 of the reactor rests in a known manner on the bottom of the tank 30 by a supply and support base 80. A step 68 through which the steam generators 10 and the pumps 82 delimits inside the tank 30 a hot collector 34a located mainly above the core 78 and a cold annular collector 34b located at the periphery thereof. As described above with reference to FIG. 1, the seal between the collectors 34a and 34b is obtained at the steam generators 10 by transition pieces 64 fixed in leaktight manner around the ferrules 54a and 54b and cooperating with the internal tank 68 by gas bell sealing systems 66.

Au moins un dispositif 76 est prévu au voisinage de l'extrémité inférieure de chacun des générateurs de vapeur, pour maintenir horizontalement les viroles 54a et 54b, tout en les laissant libres de se dilater verticalement.At least one device 76 is provided in the vicinity of the lower end of each of the steam generators, for horizontally holding the ferrules 54a and 54b, while leaving them free to expand vertically.

Sous l'action des pompes primaires 82, le sodium 34 traverse de bas en haut le coeur 78 du réacteur, pour prélever une partie de la chaleur dégagée par la réaction de fission. Le sodium ainsi réchauffé pénètre dans les générateurs de vapeur 10 par les fenêtres d'entrée 56a et 56b (figures 1 et 2) et circule de bas en haut à l'intérieur des viroles 54a et 54b, autour des doubles tubes du faisceau. Le sodium refroidi sort dans le collecteur froid 34b par l'extrémité inférieure des viroles 54a et 54b, avant d'être repris par les pompes, qui le refoulent dans le sommier d'alimentation 80 par des conduites 84.Under the action of the primary pumps 82, the sodium 34 crosses from bottom to top the core 78 of the reactor, to take part of the heat released by the fission reaction. The sodium thus reheated enters the steam generators 10 through the inlet windows 56a and 56b (FIGS. 1 and 2) and circulates from bottom to top inside the ferrules 54a and 54b, around the double tubes of the bundle. The cooled sodium exits into the cold collector 34b through the lower end of the ferrules 54a and 54b, before being taken up by the pumps, which discharge it into the supply bed 80 by pipes 84.

Chaque générateur de vapeur 10 peut se présenter sous la forme de modules séparés, ou par groupes de deux modules, ce qui permet de rendre les traversées de la dalle 28 circulaires.Each steam generator 10 can be in the form of separate modules, or in groups of two modules, which makes it possible to make the crossings of the slab 28 circular.

Il est à noter que la présence de fenêtres d'entrée auxiliaires 62a et 62b (figures 1 et 2) sur les générateurs de vapeur 10 leur permet d'assurer les fonctions d'échangeurs de refroidissement du réacteur à l'arrêt, ce qui permet de faire l'économie des boucles spécialisées utilisées habituellement. La réduction de coût du réacteur apportée par la suppression du circuit intermédiaire de sodium est encore accrue par cette disparition.It should be noted that the presence of auxiliary inlet windows 62a and 62b (FIGS. 1 and 2) on the steam generators 10 enables them to perform the functions of cooling exchangers of the reactor when stopped, which allows to do without the specialized loops usually used. The reduction in reactor cost brought about by the elimination of the sodium intermediate circuit is further increased by this disappearance.

La figure 4 représente une autre application de l'échangeur de chaleur décrit précédemment en se référant aux figures 1 et 2, dans le cas où celui-ci constitue un générateur de vapeur 10 placé dans une cuve annexe 30' distincte de la cuve principale (non représentée) contenant le coeur d'un réacteur nucléaire à neutrons rapides.FIG. 4 represents another application of the heat exchanger described above with reference to FIGS. 1 and 2, in the case where it constitutes a steam generator 10 placed in an annex tank 30 ′ distinct from the main tank ( not shown) containing the core of a fast neutron nuclear reactor.

La cuve 30' est suspendue à une dalle 28 sur laquelle repose également le générateur de vapeur 10. De façon plus précise, la dalle 28 présente une ouverture 32 à la périphérie de laquelle prend appui une pièce annulaire 26 à laquelle est suspendue la cuve 30'. La plaque 22 du générateur de vapeur repose directement sur la pièce 26.The tank 30 'is suspended from a slab 28 on which the steam generator 10 also rests. More precisely, the slab 28 has an opening 32 at the periphery of which bears an annular piece 26 to which the tank 30 is suspended '. The plate 22 of the steam generator rests directly on the part 26.

La pièce de transition 64 est raccordée de façon étanche à la paroi verticale de la cuve 30, par l'intermédiaire d'un système d'étanchéité à cloche de gaz 66. Une conduite d'arrivée de sodium 90 en provenance de la cuve principale du réacteur débouche dans la cuve 30 au-dessus de la pièce de transition 64 et une conduite retour 92 débouche dans la cuve 30 en dessous de la pièce de transition, pour ramener le sodium vers la cuve principale, sous l'action d'une pompe (non représentée).The transition piece 64 is tightly connected to the vertical wall of the tank 30, by means of a gas bell sealing system 66. A sodium inlet pipe 90 coming from the main tank of the reactor opens into the tank 30 above the transition piece 64 and a return pipe 92 opens into the tank 30 below the transition piece, to bring the sodium back to the main tank, under the action of a pump (not shown).

De préférence, des tubulures de liaison 86 traversent la plaque 22 pour déboucher dans l'atmosphère de gaz neutre surplombant le sodium à l'intérieur de la cuve 30'. Ces tubulures 86 permettent de contrôler cette atmosphère.Preferably, connecting pipes 86 pass through the plate 22 to open into the atmosphere of neutral gas overhanging the sodium inside the tank 30 '. These pipes 86 allow this atmosphere to be controlled.

Une tubulure de vidange 88 peut en outre être prévue au fond de la cuve 30'.A drain pipe 88 can also be provided at the bottom of the tank 30 '.

Comme dans l'application décrite précédemment, au moins un dispositif de guidage 76 est fixé sur la paroi de la cuve 30' pour maintenir horizontalement la partie inférieure des viroles 54a et 54b.As in the application described above, at least one guide device 76 is fixed to the wall of the tank 30 'to horizontally hold the lower part of the ferrules 54a and 54b.

Claims (11)

1. Heat exchanger with internal circulation of a first fluid, comprising
- a bundle of twin U tubes (12) immersed in a heating liquid heat-transfer fluid (34), this bundle consisting of inner tubes (14) and of outer tubes (16) delimiting an annular space in which the first fluid circulates, and comprising two straight branches (12a, 12b) connected by a curved lower part (12c) ;
- an entry chamber for the first fluid (36a) and an exit chamber for the first fluid (36b), these chambers being delimited at their lower end by a first fluid/heat-transfer fluid tube plate (20a, 20b) to which the corresponding ends of the outer tubes (16) are fastened in a leakproof manner ;
- at least one entry chamber for a heated fluid (44a) and at least one exit chamber for the said heated fluid (44b), which are separated from the entry chamber for the first fluid (36a) and from the exit chamber for the first fluid (36b), respectively, by a heated fluid/first fluid tube plate (42a, 42b), to which the corresponding ends of the inner tubes (14) are fastened in a leakproof manner ;
characterized in that the first fluid is a gas, the exchanger being suitable for being mounted in a vessel (30, 30') containing the heat-transfer fluid (34), so that the U tubes (12) are immersed in this fluid and each has a vertical leg (12a) with descending heated fluid and a vertical leg (12b) with ascending heated fluid ;
- two shells (54a, 54b) surrounding each of the vertical legs (12a, 12b) of the bundle respectively, these shells being fastened to the gas/heat-transfer fluid tube plates (20a, 20b), which are open at their lower ends and equipped with entry windows for the heat-transfer fluid (56a, 56b, 62a, 62b) at their upper ends ;
- a transition component (64) fastened to the shells (54a, 54b) below the entry windows for the heat-transfer fluid, to separate, in the said vessel, the heat-transfer fluid entering the exchanger through the entry windows from the heat-transfer fluid leaving through the lower ends of the shells.
2. Heat exchanger according to Claim 1, characterized in that the shells (54a, 54b) have main entry windows for the heat-transfer fluid (56a, 56b) which are placed above a normal level (N1) of the heat-transfer fluid in the vessel and calibrated auxiliary entry windows for the heat-transfer fluid (62a, 62b) which are placed below a minimum level (N2) of the heat-transfer fluid in the vessel, each shell being equipped with a bell (60a, 60b) fastened above the main entry windows (56a, 56b) and immersed in the heat-transfer fluid down to a level lower than the said minimum level (N2), to form a siphon for feeding this shell with heat-transfer fluid.
3. Heat exchanger according to either of Claims 1 and 2, characterized in that the outer tubes (16) are smooth, the inner tubes (14) being provided on their outer surface with centring spurs (70), and in the rising leg of the bundle, with lengthwise or helical fins (72).
4. Heat exchanger according to any one of Claims 1 to 3, characterized in that the entry (44a) and exit (44b) chambers for the heated fluid are placed laterally in relation to the entry (36a) and exit (36b) chambers for gas and are separated from the latter by substantially vertical heated fluid/gas tube plates (42a, 42b), the ends of the inner tubes fastened to these heated. fluid/gas tube plates comprising horizontal parts (14a, 14b), the gas entry and exit chambers being closed at their upper end by removable lids (40a, 40b) and the entry and exit chambers for the heated fluid being closed by removable lids (52a, 52b) placed facing the heated fluid/gas tube plates.
5. Heat exchanger according to any one of Claims 1 to 4, characterized in that it comprises at least one tube (46a) opening into the entry chamber for the heated fluid (44a) and at least one tube (46b) opening into the exit chamber for the heated fluid (44b), the said tubes being capable of being connected to an external heated fluid circuit by means of closing means (48a, 48b) permitting the exchanger to be isolated from this circuit and comprising means (50a, for injecting a purging gas capable of purging the heated fluid out of the exchanger.
6. Heat exchanger according to any one of the preceding claims, characterized in that the gas/heat-transfer fluid tube plates (20a, 20b) are fastened to a horizontal supporting component (22) surrounding the said shells (54a, 54b), this supporting component being capable of resting on a vessel closure slab (28), to be responsible for supporting the exchanger.
7. Heat exchanger according to any one of Claims 1 to 6, characterized in that the pressure of the gas circulating between the inner (14) and outer (16) tubes is slightly higher than the pressure of the heated fluid circulating in the inner tubes (14).
8. Heat exchanger according to any one of Claims 1 to 7 characterized in that the heat-transfer fluid is liquid sodium and the inert gas is helium.
9. Fast-neutron nuclear reactor comprising a main vessel (30) filled with a heating liquid heat-transfer fluid (34) and containing the reactor core (78), at least one heat exchanger (10) and at least one pump (82) capable of circulating the heat-transfer fluid between the reactor core and the heat exchanger, a vessel (68) internal to the said main vessel, separating the hot heat-transfer fluid leaving the reactor core from the cold heat-transfer fluid leaving the heat exchanger, characterized in that the said heat exchanger (10) is made in accordance with any one of the preceding claims and forms a steam generator which passes through the baffle (68) in a leakproof manner by means of a gas bell sealing system (66) inserted between the said transition component (64) and the inner vessel.
10. Fast-neutron nuclear reactor comprising a main vessel filled with heating liquid heat-transfer fluid and containing the reactor core, at least one secondary vessel (30') filled with heat-transfer fluid (34) and containing at least one heat exchanger (10), a forward duct (90) and a return duct (92) connecting the main vessel to the secondary vessel, and at least one pump capable of causing the heat-transfer fluid to circulate between the reactor core and the heat exchanger, characterized in that the said heat exchanger (10) is made in accordance with any one of Claims 1 to 8, and forms a steam generator, a gas bell sealing system (66) being inserted between the said transition component (64) and the secondary vessel (30'), at a level lower than the level at which the forward duct (90) opens into the secondary vessel and higher than the level at which the return duct (92) opens into the secondary vessel.
11. Nuclear reactor according to either of Claims 9 and 10, characterized in that the lower end of the said shells (54a, 54b) is supported laterally by guiding means (76).
EP19860401303 1985-06-19 1986-06-16 Heat exchanger with coaxial u-tubes and intermediate circulation of neutral gas, and fast neutron reactor comprising such a heat exchanger Expired EP0206921B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8509327A FR2583865B1 (en) 1985-06-19 1985-06-19 COAXIAL U TUBE HEAT EXCHANGER WITH NEUTRAL GAS INTERMEDIATE FLOW AND NUCLEAR FAST NEUTRON REACTOR COMPRISING EXCHANGERS OF THIS TYPE.
FR8509327 1985-06-19

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EP0206921A1 EP0206921A1 (en) 1986-12-30
EP0206921B1 true EP0206921B1 (en) 1988-12-21

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ITRM20110014A1 (en) * 2011-01-18 2012-07-19 S R S Servizi Di Ricerche E Svilup S R L MSU MODULAR SUB-ASSEMBLY FOR THE PROCESSING OF PROCESS HEAT EXCHANGERS AND STEAM GENERATORS AND RELATED ACCESSORIES
CN111623656A (en) * 2020-06-29 2020-09-04 福建龙净环保股份有限公司 Heat pipe and flue gas heat exchanger
CN113566611B (en) * 2021-08-12 2023-12-19 上海蓝滨石化设备有限责任公司 U-shaped tube three-flow heat exchanger

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FR2583865B1 (en) 1989-03-31
EP0206921A1 (en) 1986-12-30
FR2583865A1 (en) 1986-12-26

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