Heat exchanger module having plates with channels having fluid supply and distribution zones formed by studs, and fast neutron nuclear reactor incorporating such an exchanger module

Abstract

The invention relates to a heat exchanger module (21) having plates (201, 220) with channels (213) having fluid supply and distribution zones formed by studs (14), and to a loop-type fast neutron nuclear reactor (10) incorporating at least one such exchanger module. The invention relates to a heat exchanger module between primary and secondary circuits, in at least one of which a liquid metal circulates, for a liquid-metal-cooled fast neutron nuclear reactor of high power, typically of the order of 1000 MWth, or of lower power, typically between 50 and 400 MWe, which implements, respectively, a Rankine cycle or a Brayton cycle.

Description

Description Title of the invention: Heat exchanger module, with channel plates with fluid supply and distribution zones formed by pads, Fast neutron nuclear reactor incorporating such a heat exchanger module. technical field

[0001] The present invention relates to the field of so-called fast neutron nuclear reactors.

[0002] It relates in particular to a fast neutron nuclear reactor cooled with liquid metal, in particular liquid sodium known as SFR-Na or SFR (English acronym for "Sodium Fast Reactor"), lead or with a lead alloy, or generally known as EMBFR (English acronym for "Equid Metal Breeder Fast Reactor"), and which is part of the family of so-called fourth generation reactors (GEN IV).

[0003] The invention relates even more particularly to the aforementioned loop-type reactor, that is to say, one in which the heat exchangers and the means for pumping the primary fluid, such as sodium, are located outside the reactor vessel.

[0004] The invention is preferably applicable to SMR reactors (acronym for "Small Modular Reactor"), of small or medium power typically with an operating power between 50 and 400 MWe or of high power, typically with an operating power of 1000Wth.

[0005] For the purposes of this invention, "SMR reactor" means the usual technological meaning, namely a nuclear fission reactor, smaller in size and power than conventional modular REE reactors, whose reactor blocks are manufactured in a factory and transported to a nuclear site for installation.

[0006] By "reactor block", we mean here and within the framework of the invention, the vessel, called reactor vessel as well as all the components and part of the fluidic circuit, in particular the reactor core producing heat by nuclear fission reactions, which is housed inside the reactor vessel.

[0007] More specifically, the invention relates to a new design of a heat exchanger for a liquid coolant fast neutron loop reactor.

[0008] The main application targeted by an exchanger according to the invention is the exchange of heat between a liquid metal, such as liquid sodium, of the primary loop and a liquid metal, such as liquid sodium of the secondary loop of a fast neutron reactor cooled with the liquid metal, such as liquid sodium called RNR-Naou SFR (English acronym for "Sodium Fast Reactor") and which is part of the family of so-called fourth generation reactors.

[0009] A heat exchanger according to the invention can also be implemented in any other application requiring an exchange between two fluids, such as a liquid and a liquid, preferably when it is necessary to have a compact exchanger with high thermal power.

[0010] For the purposes of this invention, "primary fluid" means the usual meaning in thermal engineering, namely the hot fluid which transfers its heat to the secondary fluid which is the cold fluid.

[0011] Conversely, "secondary fluid" in the context of the invention means the usual meaning in thermal engineering, namely the cold fluid to which heat is transferred from the primary fluid.

[0012] In the main application, the primary fluid is sodium which circulates in the so-called primary loop of the thermal conversion cycle of a Na-FRI reactor, while the secondary fluid is also sodium which circulates in the secondary loop of said cycle. Previous technique

[0013] The currently known sodium-cooled fast neutron reactors (SFRs) can be classified into two types:

[0014] - The most common type is called integrated because the primary liquid sodium circuit, including pumping equipment and heat exchangers, is entirely contained within a single primary vessel. An integrated reactor also includes secondary liquid sodium circuits (piping, pumps and steam generators) installed outside the primary vessel and a tertiary water / steam circuit which is associated with a steam turbine for electricity production;

[0015] The other type is called a loop reactor because the primary sodium circuit is installed in several tanks with intermediate heat exchangers and pumping equipment out of the primary tank. A loop reactor also includes secondary liquid sodium circuits (piping, pumps, and steam generators) and a tertiary water / steam circuit that is connected to a steam turbine for electricity generation.

[0016] These two types of reactors have architectures that lead to a large volume of components as well as a large footprint and buildings.

[0017] As part of the studies for the prototype liquid sodium cooled fast neutron nuclear reactor called ASTRID, an energy conversion circuit between liquid sodium and a gas, nitrogen, was considered.

[0018] A design solution for a heat exchanger between liquid sodium and a gas has been proposed, which uses compact plate heat exchanger modules. This solution is described, for example, in publication [1].

[0019] EP3039373B1 describes a compact heat exchanger which employs a sealed enclosure within which several plate exchanger modules as described in [1] are arranged.

[0020] Besides avoiding any presence of water in the reactor building and thus any risk of interaction with sodium, such a sodium / gas exchanger has the major advantages of being able to be integrated into the reactor building and of eliminating the intermediate sodium circuits as in known loop reactors and thus of being able to greatly reduce the cost of the reactor.

[0021] That being said, the sealed enclosure heat exchanger is not simple to manufacture and its qualification as nuclear equipment is not immediate.

[0022] In addition, to finalize the heat exchange loop, assembly with other components (pump and piping) is required, which takes time and can be costly.

[0023] This is why the applicant proposed in the patent applications filed on January 9, 2025 under numbers FR2500219 and FR2500220 entitled respectively "Compact liquid metal cooled fast neutron nuclear reactor, loop type" and "Compact heat transfer module, between gas and liquid metal for liquid metal cooled fast neutron nuclear reactor, loop type", a liquid sodium cooled fast neutron nuclear reactor, with a heat transfer module which by itself forms an exchange loop between the primary liquid sodium circuit and a secondary gas circuit, such as nitrogen which is a closed Brayton cycle.

[0024] Such a reactor with one of its heat transfer modules is illustrated in [Fig.1]. We have represented in [Fig.1], a liquid sodium cooled nuclear reactor power plant SNR-Na of the loop type, globally designated by the reference 1.

[0025] This nuclear power plant 1 comprises, firstly, at least one SMR-type reactor block 10, including a reactor vessel 11 with a central axis X, inside which is arranged a core 12 in which the heat is released as a result of the nuclear reactions. Typically, the core 12 is of low power, for example, on the order of 300 MWth.

[0026] The tank 11 may be closed by a plug called the primary tank closure plug, which includes, among other things, the instrumentation necessary for the control and proper functioning of the nuclear reactions.

[0027] Core 12 consists of fuel assemblies. Advantageously, these assemblies are devoid of a box or hexagonal tube around the needles which constitute them, and made as described and claimed in the patent application filed by the applicant on November 19, 2024 under number FR2412649 and entitled "Fuel assembly for a nuclear reactor, of type SFR-Na, devoid of a box, comprising a bundle of fuel needles held laterally by honeycomb grids and longitudinally by stiffening rods, passing through the grids".

[0028] The circulation of liquid sodium within reactor block 10, in normal reactor operation, is advantageously as described in the patent application filed by the applicant on December 6, 2024 under number FR2413618 and entitled "Fast neutron nuclear reactor, in particular liquid metal cooled, with reactivity control system arranged on the periphery of the nuclear core".

[0029] As illustrated, the reactor architecture has primary / secondary exchange loops 2 allowing to achieve a high level of compactness of the reactor vessel 11, whose external diameter can be equal to 2.5m.

[0030] This reactor vessel 11 can typically be replaced every 35 years.

[0031] In [Fig. 1], only a primary / secondary heat exchange loop 2 is shown. This exchange loop 2 is advantageously constituted by a heat transfer module M described in detail below, which includes a heat exchanger 21.

[0032] The reactor includes an energy conversion system 3 comprising a closed Brayton cycle that directly constitutes the reactor's secondary circuit. In other words, in the reactor according to the invention, this closed Brayton cycle 3, combined with the heat exchanger of module M, eliminates the need for an intermediate heat transfer fluid loop between the liquid sodium primary circuit and the energy conversion system 3.

[0033] This closed Brayton cycle 3 preferably operates with nitrogen. It includes an outlet fluid branch 30 and an outlet fluid branch 31 connected respectively to the outlet manifold 222 and the inlet manifold 221 of the gas circuit of the exchanger 21 of module M.

[0034] The SCE system comprises a gas turbine 32 coupled to an alternator to produce electricity and heat exchangers 33 to produce high-temperature waste heat. In other words, the nuclear reactor 1 with its closed Brayton cycle 3 makes it possible to produce both electricity and high-temperature waste heat by adapting to energy demand, without consuming water.

[0035] Various isolation valves 34, 36 and 35, 37 can be installed respectively on the inlet fluid branch 30, i.e., the cold gas branch, and on the outlet fluid branch 31, i.e., the hot gas branch. As shown in [Fig. 1], compressors 320 driven by the shaft line of the gas turbine allow the gas, such as nitrogen, to circulate in the Brayton cycle 3.

[0036] In the illustrated example, for a 300 MWth reactor, the hot sodium exits reactor block 10 at a temperature of 550°C and the cold sodium entering reactor block 10 is at a temperature of approximately 400°C. In this primary circuit, the sodium can circulate at a very low pressure, typically on the order of 1 bar.

[0037] Cold nitrogen enters the heat exchanger 21 of module M at a temperature of approximately 380°C and hot nitrogen exits the heat exchanger 21 at a temperature of approximately 530°C. In the closed Brayton cycle secondary circuit 3, nitrogen can circulate at a high pressure, typically on the order of 180 bar.

[0038] As illustrated in [Fig.1], the primary / secondary exchange loops 2 are all arranged inside a sealed enclosure 4 of axisymmetric shape around the X axis of the reactor vessel 11. This sealed enclosure 4 constitutes a third containment barrier, with the fuel assemblies and the reactor vessel constituting the first and second containment barriers respectively.

[0039] Reactor block 10 and containment building 4 are arranged inside reactor building 5, which consists of an underground concrete structure and performs various functions, including contributing to the containment safety function. Thus, reactor building 5 constitutes a fourth containment barrier.

[0040] Typically, the building envelope of reactor 5 can consist of several layers. As illustrated in [Fig. 1], the envelope can be a non-prestressed concrete wall, serving as the interface with the outside.

[0041] As also illustrated in [Fig.1], reactor building 5 can be buried entirely in soil S.

[0042] This power plant configuration 1 is perfectly suited to provide medium power outputs, typically in the order of 300MWth per reactor block 10.

[0043] In addition to small or medium power markets or typically with an operating power between 50 and 400 MWe, the applicant seeks to address higher power markets, typically in the order of 1000Wth for a power plant.

[0044] For high power values, the Na / gas Brayon cycle as an energy conversion system is no longer suitable.

[0045] It is indeed necessary to implement a Rankine cycle and to add an intermediate sodium heat exchange circuit, also as a secondary fluid.

[0046] Sodium-to-sodium heat exchangers typically consist of tubes and two plates. Sodium circulates both inside and outside the tubes. Their main drawback is their bulk, and they can present thermodynamic challenges because the tubes are constrained and the metal plates used are thick.

[0047] There is therefore a need to further improve heat exchangers with two fluid circuits, at least one of which is liquid sodium, more generally liquid metal, particularly for fast neutron nuclear reactors, especially those cooled with liquid metal, of the loop type.

[0048] The aim of the invention is to meet at least part of this need. Description of the invention

[0049] To this end, the invention relates, in one of its aspects, to a heat exchanger module with at least two fluid circuits, at least one of which is made of liquid metal, the longitudinal axis module (XI) comprising a stack of plates defining the two fluid circuits, at least a portion of the plates comprising fluid circulation channels, the channels of each of the two circuits, having:

[0050] - at least one fluid supply and distribution zone from outside the stack, forming a fluid pre-collector, in which the channels are delimited by solid studs distributed over the plate surface;

[0051] - a continuous exchange zone with the pre-collector in which the channels are each delimited by a groove separated from each other by a rib and extend along the longitudinal axis (XI);

[0052] - at least at one of the longitudinal ends of the stack, a fluid collector opening onto a lateral base of the stack onto which the channels of the pre-collector of the first circuit open but not those of the pre-collector of the second circuit, and preferably comprising at one of the longitudinal ends, a fluid collector forming the inlet manifold of the first circuit and at the other of the longitudinal ends, a fluid collector forming the outlet manifold of the first circuit,

[0053] - at least at one of the longitudinal ends of the stack, a fluid collector opening onto a lateral base of the stack on which the channels of the pre-collector of the second circuit but not on those of the first circuit, and preferably comprising at one of the longitudinal ends, a fluid collector forming the inlet manifold of the second circuit and a fluid collector forming the outlet manifold of the second circuit.

[0054] According to an advantageous embodiment, the module comprises two pre-collectors of the first circuit, each arranged at one of the longitudinal ends of the stack, one of the two pre-collectors forming a fluid inlet pre-collector, the other forming a fluid outlet pre-collector.

[0055] According to another advantageous embodiment, the module comprises two pre-collectors of the second circuit, each arranged at one of the longitudinal ends of the stack, one of the two pre-collectors forming a fluid inlet pre-collector, the other forming a fluid outlet pre-collector.

[0056] Preferably, the studs are evenly distributed in a staggered pattern on the pre-collector plate surface according to a triangular pattern or the studs are evenly distributed on the pre-collector plate surface according to a rectangular or square pattern.

[0057] Preferably, the posts are generally cylindrical in shape.

[0058] According to one embodiment, the channels of the exchange zone of the first circuit and the second circuit are straight, parallel to each other and extend parallel to the longitudinal axis (XI).

[0059] According to an advantageous embodiment, the stack consists of metal plates assembled together either by hot isostatic compression (HIC), or by hot uniaxial compression (HUC) so as to obtain diffusion welding between the metal plates, or by brazing, or achieved by additive manufacturing.

[0060] According to an advantageous configuration, a plate of the first circuit is intercalated between two plates of the second circuit at least in the central part of the stack.

[0061] The invention also relates to a heat transfer module (M) for a liquid-metal-cooled loop-type fast neutron nuclear reactor, comprising: - a tank, called an expansion tank, inside which are delimited two separate compartments called hot and cold, intended to be pressurized by a common gas head, each of the two compartments comprising an inlet port and an outlet port, - at least one heat exchanger module as described above, defining two circuits, at least one of which is liquid metal, in particular liquid sodium, and an inlet manifold connected to the outlet port of the hot compartment of the expansion tank and an outlet manifold connected to the inlet port of the cold compartment of the expansion tank, - an electromagnetic pump, designed to circulate the liquid metal, and connected upstream to the outlet of the cold compartment of the expansion tank, - at least two fluid branches, one of which, upstream of the exchanger, is intended to be connected to a so-called hot manifold of the reactor block of the nuclear reactor and to the inlet port of the hot compartment of the expansion tank, and the other downstream of the exchanger, is intended to be connected to a so-called cold manifold of the reactor block and to the electromagnetic pump.

[0062] Within the framework of the invention, a fluidic branch can be constituted by a piping with at least one pipe.

[0063] Depending on the requirements, the electromagnetic pump can be arranged horizontally or vertically in a configuration installed in a nuclear reactor.

[0064] The invention also relates, in another aspect, to a liquid-metal cooled, loop-type fast neutron nuclear reactor, comprising:

[0065] - at least one heat transfer module as described above, forming a primary / secondary heat exchange loop,

[0066] - an energy conversion system (ECS) comprising a Rankine cycle or a Brayton cycle in which an inlet fluidic branch and an outlet fluidic branch are connected respectively to the outlet manifold and the inlet manifold of the secondary circuit of the module exchanger.

[0067] Advantageously, the pressurization gas for the gas head of the module's expansion tank is argon, preferably at very low pressure.

[0068] Advantageously still, the reactor includes at least one metallic sealing bellows arranged around each of the inlet and outlet manifolds and around the inlet fluid branch and the outlet fluid branch of the SCE system.

[0069] The invention also relates in another of its aspects to a method of operating the nuclear reactor described above, comprising circulating the liquid metal by the operating electromagnetic pump from the reactor block to within the heat transfer module and back to the reactor block.

[0070] Advantageously, the difference in liquid metal elevation between the two compartments within the expansion tank corresponds to the pressure drop induced by the module's heat exchanger. The expansion tank is sized to allow the free expansion of the liquid metal within the primary heat exchange loop during the transition from the reactor shutdown state, in which the liquid metal is at a so-called cold temperature, to the reactor's normal operating state, in which the liquid metal is at a so-called hot temperature, with a constant mass of gas in the common gas head.

[0071] Preferably, the difference in altimetric levels is between 60 and 100 cm.

[0072] When the liquid metal is liquid sodium, the cold temperature in the reactor shutdown state is preferably approximately 200°C and the hot temperature is approximately 550°C.

[0073] The gas pressure in the common gas sky is preferably between 50 and 100 mbar relative.

[0074] Thus, the invention essentially consists of proposing a heat exchanger module between primary and secondary circuits in which a liquid metal or a liquid metal and a gas can circulate for a liquid metal-cooled fast neutron nuclear reactor, respectively of high power, typically on the order of 1000 MWe, which implements a Rankine cycle or of small and medium power on the order of 400 MWe which implements a Brayton cycle.

[0075] The stacked plate exchanger module, or one made by additive manufacturing, includes pre-collectors of two fluid circuits made with studs distributed on the plate surface which delimit the channels in which the primary liquid metal and the secondary liquid metal or secondary gas, such as nitrogen or molten salt(s), respectively circulate before reaching their heat exchange zone.

[0076] These pads ensure that the plates remain under pressure while exhibiting low thermal inertia.

[0077] The pads ensure a homogeneous distribution of the liquid metal in each circuit, minimizing the addition of pressure losses, regardless of the geometry of the channels in the heat exchange zone.

[0078] The geometric shapes and distribution of the pads can be modified as desired to control the distribution of the liquid metal according to the intended application and its constraints, particularly temperature and pressure.

[0079] The density of studs in the pre-collector can also be varied.

[0080] Furthermore, with the pads according to the invention, an admission and an outlet of each of the two fluids at a longitudinal end of the module, from a lateral base of the stack of plates, makes it possible to obtain a very compact module.

[0081] In conclusion, a heat transfer module according to the invention offers numerous advantages, including:

[0082] - a very compact plate exchanger module perfectly suited for liquid metal / liquid metal exchange or liquid metal / gas exchange or liquid metal / molten salt(s) exchange in an NFR reactor, in particular Na / Na;

[0083] - the realization of a loop architecture with several modules integrating exchanger modules and a Rankine cycle for a Na-FRI reactor allowing to reach a high power, typically 1000Wth or a Brayton cycle for a small or medium power Na-FRI reactor.

[0084] All applications requiring heat exchangers can be considered with exchanger modules according to the invention, among which we can mention all types of SMR (English acronym for "Small Medium Reactor") nuclear reactors with liquid metal coolant, such as lead, at high operating temperature, typically 500°C.

[0085] Other advantages and features of the invention will become clearer upon reading the detailed description of examples of implementations of the invention given by way of illustration and not limitation with reference to the following figures. Brief description of the drawings

[0086] [Fig.1] [Fig.1] is a schematic view of a liquid sodium cooled nuclear reactor power plant, SNR-Na according to patent application FR2500219 with one of the exchange loops formed by a heat transfer module and a closed Brayton cycle energy conversion system.

[0087] [Fig.2] [Fig.2] is a view showing in detail the arrangement and fluidic connections of a heat transfer module with a heat exchanger module according to the invention as part of a primary / secondary exchange loop between a reactor block and a Rankine cycle.

[0088] [Fig.3] [Fig.3] is a perspective view of an exchanger module according to the invention.

[0089] [Fig.4] [Fig.4] is a side view of an exchanger module according to the invention.

[0090] [Fig.4A] [Fig.4A] is a longitudinal cross-sectional view of the exchanger module according to [Fig.4].

[0091] [Fig.5] [Fig.5] is another longitudinal cross-sectional view of the exchanger module according to [Fig.4].

[0092] [Fig.5A] [Fig.5A] is a detail view of [Fig.5].

[0093] [Fig.6] [Fig.6] is another longitudinal cross-sectional view of the exchanger module according to [Fig.4].

[0094] [Fig.7] [Fig.7] illustrates the circulation of the primary fluid in a circulation plate of the exchanger module according to the invention and the connection with a fluidic branch of the secondary circuit.

[0095] [Fig.8] [Fig.8] reproduces in detail part of [Fig.7].

[0096] [Fig.9] [Fig.9] illustrates the circulation of the secondary fluid from a circulation plate of the exchanger module according to the invention in a fluidic branch of the secondary circuit.

[0097] [Fig.9A], [Fig.9B] Figures 9A and 9B are cross-sectional views of [Fig.9] along A-A and BB. Detailed description

[0098] Throughout this application, the terms "horizontal", "vertical", "lower", "upper", "below" and "above" are to be understood by reference to a reactor vessel arranged vertically and to an arrangement in relation to the cold or hot zone.

[0099] Similarly, throughout this application, the terms "upstream" and "downstream" are to be understood with reference to the direction of sodium flow.

[0100] Figure 1 has already been described in the introduction. It will therefore not be discussed here.

[0101] Figure 2 illustrates part of a loop-type liquid sodium-cooled nuclear reactor (LSNR) power plant, generally designated by reference 1, dedicated to providing high power, typically on the order of 1000Wth per reactor block 10.

[0102] To provide such power, a heat transfer module M constitutes an exchange loop 2 between the primary circuit in liquid sodium and the secondary circuit also in liquid sodium which feeds a Rankine cycle as a thermal energy to electrical conversion system.

[0103] To perform this heat exchange, module M comprises a heat exchanger module 21 according to the invention, with a shell 210 defining the primary liquid sodium circuit and a coiled tube bundle 220 inside the shell, defining the secondary liquid sodium circuit. This module 21 is described below.

[0104] The M module includes an expansion tank 20 inside which are delimited two separate compartments 200, 201 called hot and cold, intended to be pressurized by a common gas head 202. The common gas head 202 can be pressurized with argon.

[0105] Each of the two compartments includes an inlet port and an outlet port.

[0106] An inlet manifold of the heat exchanger 21 is connected to the outlet port of the hot compartment 200 of the expansion tank 20 and an outlet manifold is connected to the inlet port of the cold compartment 201 of the expansion tank 20.

[0107] An electromagnetic pump 22, designed to circulate the primary liquid sodium during the operation of reactor 1, is connected to the outlet of the cold compartment 201 of the expansion tank 20. The electromagnetic pump 22 is compact and preferably operates with high flow rates, typically on the order of 1200 m³ / s 3 / h.

[0108] A fluid branch 23 connected upstream to a so-called hot collector of the reactor block 10, is connected upstream to the inlet port of the hot compartment 200 of the expansion tank 20, to bring the hot primary liquid sodium there.

[0109] A fluidic branch 24 connected downstream to a so-called cold collector of the reactor block 10, is connected downstream of the electromagnetic pump 22 to reinject the cold primary liquid sodium into the reactor block 10.

[0110] A fluidic branch can connect the hot compartment of the expansion tank 20 to the inlet manifold of the exchanger 21 to bring the hot liquid sodium there.

[0111] In the illustrated configuration where the electromagnetic pump 22 is vertical, a fluidic branch 26 connects the outlet manifold of the exchanger 21 to the cold compartment 201 of the expansion tank 20 to bring the cold primary liquid sodium there.

[0112] The reactor includes an unshown energy conversion system featuring a Rankine cycle that directly forms the secondary circuit of the reactor.

[0113] This Rankine cycle operates with liquid sodium as the secondary fluid. It includes an inlet fluid branch 70 and an outlet fluid branch 71 connected respectively to the outlet manifold 221 and the outlet manifold 222 of the secondary liquid sodium circuit of the exchanger 21 of module M.

[0114] Different isolation valves can be installed respectively on the inlet fluid branch 70, i.e. the cold secondary sodium branch, and on the outlet fluid branch 71, i.e. the hot secondary sodium branch.

[0115] In the illustrated example, for a 1000Wth reactor, the hot sodium exits reactor block 10 at a temperature of 550°C and the cold sodium entering reactor block 10 is at a temperature of approximately 400°C. In this primary circuit, the sodium can circulate at a very low pressure, typically on the order of 1 bar.

[0116] Cold secondary liquid sodium enters the heat exchanger 21 of module M at a temperature of approximately 380°C, and hot secondary liquid sodium exits the heat exchanger 21 at a temperature of approximately 530°C. In the Rankine cycle secondary circuit, the secondary liquid sodium can circulate at a pressure typically on the order of 1 bar.

[0117] As illustrated in [Fig.2], the primary / secondary exchange loops 2 are all arranged inside a sealed enclosure 4 of axisymmetric shape around the central axis of the reactor block vessel 10. This sealed enclosure 4 constitutes a third containment barrier, with the fuel assemblies and the reactor vessel constituting the first and second containment barriers respectively.

[0118] Reactor block 10 and containment building 4 are arranged inside reactor building 5, which consists of an underground concrete structure and performs various functions, including contributing to the containment safety function. Thus, reactor building 5 constitutes a fourth containment barrier.

[0119] Typically, the building envelope of reactor 5 can consist of several layers. As illustrated in [Fig.2], the envelope can be a non-prestressed concrete wall, serving as the interface with the outside.

[0120] As also illustrated in [Fig.2], reactor building 5 can be fully buried in the ground.

[0121] Figures 3 to 6 show an advantageous example of a two-fluid-circuit heat exchanger module 21, which is implemented for the exchange between liquid sodium (Na) from the primary circuit and liquid sodium (Na) from the secondary Rankine cycle circuit.

[0122] Module 21 consists of an alternating stack of metal plates 210, 220 assembled together by diffusion welding preferably according to a CIC technique, or made by additive manufacturing.

[0123] As shown in Figures 3 to 6, the heat exchanger 21, which extends along a central axis (XI), incorporates two manifolds 211 and 212, respectively for the inlet and outlet of liquid sodium (Na). One manifold is arranged on the top of the exchanger along axis XI, and the other is also arranged along axis XI, but on the underside. Each of the manifolds 211 and 212 opens onto a lateral base of the plate stack, onto which the channels of the primary Na circuit open, but not those of the secondary Na circuit.

[0124] The heat exchanger 21 also includes two manifolds 221 and 222, respectively for the inlet and outlet of the secondary Na, one arranged at the bottom and the other at the top of the exchanger. Each of the inlet 221 and outlet 222 manifolds opens onto a lateral base of the plate stack, connecting to the channels of the secondary Na circuit but not to those of the primary Na circuit.

[0125] In such an exchanger 21, the circulation of fluids (primary Na, secondary Na) is therefore counter-current.

[0126] Figures 4 and 4A show the stacking and respectively the circulation within a primary Na circulation plate 210 and a secondary Na circulation plate 220, the arrows symbolizing the circulation of each of the fluids in each plate concerned.

[0127] Figures 5, 5A show a Na 210 circulation plate.

[0128] A plate 210 comprises two supply and distribution zones ZI, each forming a pre-collector of the fluid, arranged on either side of a heat exchange zone Z2.

[0129] According to the invention, the channels 213 of a pre-collector ZI are delimited by solid cylindrical studs 214 distributed over the plate surface. Preferably, as shown in Figures 5 and 5A, the solid cylindrical studs 14 are uniformly staggered over the plate surface of the pre-collector. More precisely, this staggered distribution follows an identical triangular pattern across the entire surface of the plates 210 of the pre-collector ZI. A triangular pattern distribution allows for better filling of the pre-collector volume by the studs 214 and is preferred to ensure the pressure resistance of the heat exchanger module.

[0130] The channels 213, delimited by the solid cylindrical studs 214, open into the channels 215 of the heat exchange zone Z2, which is continuous with the pre-collector. As shown, the channels 215 of the exchange zone are each delimited by a groove 215 separated from each other by a rib 216 and extend along the longitudinal axis (XI). Preferably, as shown, they are straight, parallel to each other, and extend parallel to the longitudinal axis (XI) of the module 21.

[0131] The lugs 214 can be of a height such that they bear directly against a plate 220. Alternatively, two adjacent plates 210 can be fitted with cylindrical lugs 214 whose height represents a portion of the height of a channel 213. Once the plates are joined together, these lugs define the total height of the channel. The same applies to the ribs 216. The arrangement of the lugs 214 ensures that the plates 210 can withstand pressure.

[0132] With such a plate 210, as illustrated in part in Figures 5 and 5A, the primary liquid sodium is fed from the tubular inlet manifold 211 to be distributed from the inlet, to a lateral base of the stack of plates 210, 220, to the channels 213 delimited by the pads 214. The primary liquid sodium flows in the channels 213 around the pads 214 of the inlet pre-manifold, to reach the channels 215 of the heat exchange zone Z2 and then flows around the pads 14 of the outlet pre-manifold to be discharged through the outlet, to the other lateral base of the stack of plates 210, 220, of the channels 213 and then recovered by the outlet manifold 212.

[0133] Figures 9 and 9A show a 220 secondary Na circulation plate, made in a manner analogous to a 210 primary Na circulation plate.

[0134] Thus, a 220 plate comprises two supply and distribution zones Z1H, each forming a pre-collector of the fluid, arranged on either side of a heat exchange zone Z2.

[0135] The channels 223 of a ZI pre-collector are delimited by solid cylindrical studs 24 distributed across the plate surface. Preferably, the solid cylindrical studs 24 are uniformly staggered across the plate surface of the pre-collector. Again, this staggered distribution follows an identical triangular pattern across the entire surface of the plates 220 of the ZI pre-collector. A triangular pattern distribution allows for better filling of the pre-collector volume by the studs 224 and is preferred to ensure the pressure resistance of the heat exchanger module.

[0136] The channels 223, delimited by the solid cylindrical studs 224, open into the channels 225 of the heat exchange zone Z2, which is continuous with the pre-collector. As shown, the channels 225 of the exchange zone are each delimited by a groove 225 separated from each other by a rib 226 and extend along the longitudinal axis (XI). Preferably, as shown, they are straight, parallel to each other, and extend parallel to the longitudinal axis (XI) of the module 21.

[0137] The lugs 224 can be of a height such that they bear directly against a plate 210. Alternatively, two adjacent plates 220 can be fitted with cylindrical lugs 224 whose height represents a portion of the height of a channel 223. Once the plates are joined together, these lugs define the total height of the channel. The same applies to the ribs 226. The arrangement of the lugs 224 ensures that the plates 220 can withstand pressure.

[0138] With such a plate 220, as illustrated in part in [Fig.9], the secondary liquid sodium is fed from the inlet tubular manifold 221 to be distributed into the inlet channels, to a lateral base of the plate stack 210, 220, and then into the channels 223 delimited by the pads 224. The secondary liquid sodium then flows around the pads 224 of the inlet pre-manifold, to reach the channels 225 of the heat exchange zone Z2 and then flows into the channels 223 around the pads 224 of the outlet pre-manifold to be discharged through the outlet channels, to the other lateral base of the plate stack 210, 220 and then recovered by the outlet manifold 222.

[0139] Thus, according to the invention, the pads 214 and 224 ensure a homogeneous distribution of each of the fluids, i.e., the primary and secondary liquid sodium respectively, regardless of the geometry of the channels 215 and 225 in their heat exchange zone Z2, while exhibiting low thermal inertia and minimizing added pressure losses. Furthermore, as already mentioned, the pads 214 and 224 are dimensioned to guarantee pressure resistance.

[0140] As illustrated, the pads 214, 224 of the plates 210, 220 of the two fluid circuits (primary Na, secondary Na) are aligned, that is to say that the axis of revolution of a pad 214 is aligned with that of a pad 224.

[0141] One can also consider offsetting the studs, in other words, offsetting them laterally on the surface of the plates. This offset allows for studs with through holes. This offset is accompanied by a change in the stud distribution, resulting in a triangular pattern as illustrated in the previous alternative to a rectangular or square pattern.

[0142] Such an exchanger 21 implemented for the exchange between primary liquid sodium and secondary liquid sodium, whose thermal conductivity at high temperature is very high, allows the module M to exchange a very high unit power, typically on the order of 70 MWth.

[0143] Figures 7 to 9B illustrate the arrangement of metal sealing bellows 80, 81 both around the primary Na inlet manifolds 211; 222 respectively and the secondary Na outlet manifolds 221; 212 respectively.

[0144] As shown, these sealing bellows 80, 81 also surround the inlet 70 and outlet 71 pipes of the secondary Na, also forming a sealed passage through the metallic shell 4 of the reactor.

[0145] Different isolation valves 91 can be installed respectively on the inlet fluid branch 70, i.e. the cold secondary Na branch and on the outlet fluid branch 71, i.e. the hot secondary Na branch.

[0146] The invention is not limited to the examples just described; in particular, features of the illustrated examples can be combined in unillustrated variants.

[0147] Other variations and improvements can be considered without going outside the scope of the invention.

[0148] The exchanger module 21 which has just been described is implemented to carry out the exchange between primary liquid sodium and secondary liquid sodium, it can very well be used for an exchange between liquid sodium, and more generally liquid metal and another liquid metal or a gas, in particular nitrogen or molten salt(s). List of cited references:

[0149] [1]: “Innovative power conversion system for the French SFR prototype, ASTRID”, L. Cachon and al. Proceeding of ICAPP' 12, Chicago, USA, June 24-28, 2012, Paper 12300.

Claims

Demands

1. Heat exchanger module (21) having at least two fluid circuits, at least one of which is liquid metal, the longitudinal axis module (XI) comprising a stack of plates (210; 220) defining the two fluid circuits, at least a portion of the plates comprising each of the fluid circulation channels, the channels of each of the two circuits, having: - at least one fluid supply and distribution zone (Zi) from outside the stack, forming a fluid pre-collector, in which the channels (213; 223) are delimited by solid studs (214; 224) distributed over the plate surface; - an exchange zone (Z2) continuous with the pre-collector in which the channels are delimited each by a groove (215; 225) separated from each other by a rib (216; 226) and extend along the longitudinal axis (XI); - at least at one of the longitudinal ends of the stack, a fluid collector (211, 212) opening onto a lateral base of the stack onto which the channels of the pre-collector of the first circuit open but not those of the pre-collector of the second circuit, and preferably comprising at one of the longitudinal ends, a fluid collector forming the inlet collector (211) of the first circuit and at the other of the longitudinal ends, a fluid collector forming the outlet collector (212) of the first circuit, - at least at one of the longitudinal ends of the stack, a fluid collector (221, 222) opening onto a lateral base of the stack on which the channels of the pre-collector of the second circuit but not on those of the first circuit, and preferably comprising at one of the longitudinal ends, a fluid collector forming the inlet collector (221) of the second circuit and a fluid collector forming the outlet collector (222) of the second circuit.

2. Heat exchanger module according to claim 1, comprising two pre-collectors of the first circuit, each arranged at one of the longitudinal ends of the stack, one of the two pre-collectors forming a fluid inlet pre-collector, the other forming a fluid outlet pre-collector.

3. Heat exchanger module according to claim 1 or 2, comprising two pre-collectors of the second circuit, each arranged at one of the longitudinal ends of the stack, one of the two pre-collectors forming a fluid inlet pre-collector, the other forming a fluid outlet pre-collector.

4. Exchanger module according to any one of the preceding claims, the studs being uniformly distributed in a staggered pattern on the pre-collector plate surface in a triangular pattern or the studs being uniformly distributed on the pre-collector plate surface in a rectangular or square pattern.

5. Exchanger module according to any one of the preceding claims, the pads being generally cylindrical in shape.

6. Exchanger module according to any one of the preceding claims, the channels (215; 225) of the exchange zone of the first circuit and the second circuit being straight, parallel to each other and extending parallel to the longitudinal axis (XI).

7. Heat exchanger module according to any one of the preceding claims, the stack being made up of metal plates assembled together either by hot isostatic compression (HIC), or by hot uniaxial compression (HUC) so as to obtain diffusion welding between the metal plates, or by brazing, or achieved by additive manufacturing.

8. Exchanger module according to any one of the preceding claims, wherein a plate of the first circuit is intercalated between two plates of the second circuit at least in the central part of the stack.

9. Heat transfer module (M) for nuclear reactor (1) a liquid metal-cooled, loop-type fast neutron reactor comprising: - a tank (20) called the expansion tank inside which are delimited two separate compartments called hot and cold, intended to be pressurized by a common gas head, each of the two compartments comprising an inlet orifice and an outlet orifice, - at least one heat exchanger module (21) according to any one of the preceding claims, defining two circuits, at least one of which is liquid metal, and an inlet manifold connected to the outlet port of the hot compartment of the expansion tank and an outlet manifold connected to the inlet port of the cold compartment of the expansion tank, - an electromagnetic pump (22), intended to circulate the liquid metal, and connected upstream to the outlet of the cold compartment of the expansion tank, - at least two fluid branches (23, 24), one of which (23), upstream of the exchanger, is intended to be connected to a so-called hot manifold of the reactor block (10) of the nuclear reactor and to the inlet of the hot compartment of the expansion tank, and the other (24) downstream of the exchanger, is intended to be connected to a so-called cold manifold of the reactor block and to the electromagnetic pump.

10. Liquid-metal cooled, loop-type fast neutron nuclear reactor (1), comprising: - at least one heat transfer module according to claim 9, forming a primary / secondary heat exchange loop, - an energy conversion system (ECS) comprising a Rankine cycle or a Brayton cycle of which an inlet fluidic branch and an outlet fluidic branch are connected respectively to the outlet manifold and the inlet manifold of the secondary circuit of the module's exchanger.

11. Nuclear reactor (1) according to claim 10, comprising at least one metallic sealing bellows (80; 81) arranged around each of the inlet and outlet manifolds and around the inlet fluidic branch and the outlet fluidic branch of the SCE system.

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