Canned motor pump and nuclear reactor comprising such a pump

Abstract

The invention relates to a canned motor pump comprising: - a bowl (3) with a fluid inlet (5) and a fluid outlet (7); - a pump wheel (9) arranged inside the bowl (3); - a motor casing (11) rigidly attached to the bowl (3) and internally defining a chamber (13) in fluid communication with the bowl (3); - a motor (15) comprising a rotor (17) and a stator (19), arranged inside the chamber (13); - a shaft (21) to which the pump wheel (9) is attached, the shaft (21) being rotated about an axis of rotation by the rotor (17); - a heat exchanger (41) arranged inside the chamber (13), with a first side (43) through which the fluid flows and a second side (45) through which a heat transfer fluid flows; - a circuit for cooling the motor (47) with the fluid, wherein a cooling passage (49) through which the fluid flows is in thermal contact with the motor (15), and wherein the first side (43) of the heat exchanger (41) forms part of the cooling circuit (47) and is arranged downstream of the cooling passage (49).

Description

[0001] DESCRIPTION

[0002] TITLE: Wet motor pump and nuclear reactor comprising such a pump

[0003] The invention generally relates to pumps with a submerged motor.

[0004] An SMR (Small Modular Reactor) type nuclear reactor can be equipped with a primary pump with a flooded motor, intended to circulate the primary fluid in the reactor vessel.

[0005] When such a primary pump is arranged in the lower part of the nuclear reactor, specific constraints must be respected regarding the maximum authorized flow rate in the event of a leak.

[0006] In particular, for the primary fluid circulation pipes, there must not be any breakable pipes in the pump with a diameter greater than 4 mm.

[0007] In a wet-motor primary pump, the heat released by the electric motor and the mechanical losses due to the rotating parts in the water are removed by circulating the primary fluid inside the external casing in which the motor is housed. This primary fluid must itself be cooled by circulation in a heat exchanger. In the heat exchanger, the heated primary fluid is brought into contact with a heat transfer fluid.

[0008] In such a primary pump, it is possible to arrange the heat exchanger around the outer casing. In this case, the primary fluid circulation side of the heat exchanger is connected to the outer casing by pipes with an internal diameter of approximately 20 mm. These pipes are welded onto the outer casing of the pump and are therefore classified as breakable elements.

[0009] Such an arrangement therefore does not comply with the safety constraints to be observed for primary pumps located in the lower part of the nuclear reactor.

[0010] In this context, the invention aims to propose a pump which does not have the above defect.

[0011] To this end, the invention relates to a submerged motor pump for a fluid, comprising:

[0012] - a bowl with a fluid inlet and a fluid outlet;

[0013] - a pump wheel, arranged inside the bowl;

[0014] - a motor casing, integral with the bowl and internally delimiting a chamber in fluid communication with the bowl; - a motor comprising a rotor and a stator, arranged inside the chamber;

[0015] - a shaft on which the pump wheel is fixed, the shaft being driven in rotation around an axis of rotation by the rotor;

[0016] - a heat exchanger arranged inside the chamber, with a first side in which the fluid circulates and a second side in which a heat transfer fluid circulates;

[0017] - a fluid cooling circuit for the engine, with a cooling passage along which the fluid circulates in thermal contact with the engine, the first side of the heat exchanger being part of the cooling circuit and being arranged downstream of the cooling passage.

[0018] Because the heat exchanger is arranged inside the chamber delimited by the engine casing, there is no duct outside the engine casing for the circulation of fluid between the exchanger and said chamber. The circulation of fluid for cooling the engine takes place entirely inside the engine casing. This casing is a non-rupture element. This therefore makes it possible to meet the constraint on the maximum leakage flow rate.

[0019] The submerged motor pump may also have one or more of the following characteristics, considered individually or in all technically possible combinations:

[0020] - the engine casing comprises a shell placed around the engine, the heat exchanger being arranged radially between the engine and the shell;

[0021] - the heat exchanger comprises a cylindrical membrane having a proximal end axially towards the pump wheel and a distal end axially opposite the pump wheel, the cylindrical membrane having an external passage for the heat transfer fluid on a radially external face and an internal passage for the fluid on a radially internal face;

[0022] - the external passage comprises at least one external helical groove hollowed out in the radially external face, and / or the internal passage comprises at least one internal helical groove hollowed out in the radially internal face;

[0023] - the proximal end and the distal end of the cylindrical membrane are welded to an internal surface of the motor housing to fluidically isolate the external passage from the internal passage;

[0024] - the pump comprises a stator casing, with a cylindrical metal jacket interposed radially between the radially internal face of the cylindrical membrane and the stator, and closing the internal passage on one radially internal side;

[0025] - the stator frame comprises a proximal support ring and a distal support ring arranged axially on either side of the motor, rigidly fixed to two opposite ends of the metal sleeve, a slice of the proximal support ring and a slice of the distal support ring being pressed against the radially internal face of the cylindrical membrane respectively at the proximal end and the distal end;

[0026] - the or each external helical groove has a first external depth in an axially central portion of the cylindrical membrane and a second external depth less than the first external depth at the proximal end and at the distal end of the cylindrical membrane; and / or the or each internal helical groove has a first internal depth in an axially central portion of the cylindrical membrane and a second internal depth less than the first internal depth at the proximal end and at the distal end of the cylindrical membrane;

[0027] - a distal volume is delimited between the distal support ring and a distal bottom of the motor casing, the distal support ring comprising at its periphery a plurality of orifices fluidly connecting the distal volume with the internal passage;

[0028] - the pump includes a member for circulating the fluid along the engine cooling circuit, secured to the shaft and housed in the distal volume;

[0029] - the pump includes:

[0030] * a proximal bearing with a proximal fixed ring mounted on the proximal support ring and a proximal rotating ring secured to the shaft;

[0031] * a distal bearing with a distal fixed ring mounted on the distal support ring and a distal rotating ring secured to the shaft, the cooling passage comprising a proximal volume located axially between the proximal support ring and a proximal bottom of the motor housing, a proximal intermediate volume located axially between the proximal bearing and the rotor, an air gap between the rotor and the stator, a distal intermediate volume located between the rotor and the distal bearing, and the distal volume;

[0032] - the proximal fixed ring and / or the proximal rotating ring comprise passages for the circulation of fluid from the proximal volume to the proximal intermediate volume, the distal fixed ring and / or the distal rotating ring comprising passages for the circulation of fluid from the distal intermediate volume to the distal volume;

[0033] - the pump comprises a heat transfer fluid inlet and a heat transfer fluid outlet fluidly connected to the second side of the heat exchanger, the heat transfer fluid inlet being provided to be connected to a heat transfer fluid supply conduit, the heat transfer fluid outlet being provided to be connected to a heat transfer fluid discharge conduit, the pump comprising an inlet cut-off member configured to selectively isolate or connect the heat transfer fluid inlet and the heat transfer fluid supply conduit and / or an outlet cut-off member configured to selectively isolate or connect the heat transfer fluid outlet and the heat transfer fluid discharge conduit.

[0034] According to a second aspect, the invention relates to a nuclear reactor comprising:

[0035] - a core, comprising nuclear fuel assemblies;

[0036] - a pressure vessel, containing the core, the pressure vessel being filled with a primary heat transfer fluid up to a nominal level;

[0037] - at least one primary pump having the above characteristics, arranged to circulate the primary heat transfer fluid in the core, mounted at a level lower than or equal to said nominal level.

[0038] The nuclear reactor may also have one or more of the following characteristics, considered individually or in all technically possible combinations:

[0039] - the primary pump is mounted on the pressure vessel, the shell being placed outside the pressure vessel, the pump impeller being placed inside the pressure vessel.

[0040] Other characteristics and advantages of the invention will emerge from the detailed description given below, for information purposes only and in no way limiting, with reference to the appended figures, among which:

[0041] - Figure 1 is an axial sectional view of the submerged motor pump of the invention;

[0042] - Figures 2 and 3 are enlarged views of two details II and III of figure 1;

[0043] - Figure 4 is an exploded perspective view of the submerged motor pump of Figure 1; and

[0044] - Figure 5 is a schematic representation, in axial section, of a nuclear reactor equipped with primary pumps according to Figures 1 to 4.

[0045] The wet-motor pump in Figure 1 is intended to set a fluid in motion.

[0046] In an exemplary embodiment, the flooded motor pump is intended to circulate the primary fluid of an SMR type nuclear reactor.

[0047] The primary fluid is circulated by the wet motor pump 1 inside the pressure vessel, in which the nuclear reactor core is located. The primary fluid passes through the nuclear reactor core, then passes through a steam generator, and then arrives at the suction of the wet motor pump 1. The wet motor pump 1 delivers the primary fluid into the nuclear reactor pressure vessel. The wet motor pump is, for example, placed in the lower part of the nuclear reactor, i.e., at the same level as the nuclear reactor pressure vessel or at a lower level. For example, it is mounted below the nominal primary fluid level of the pressure vessel.

[0048] The wet-motor pump is used to circulate a fluid that is not the primary fluid of the nuclear reactor. In another variant, it is used in a nuclear reactor of a type other than SM R reactors, or is used in any other industrial installation that is not a nuclear reactor.

[0049] As seen in Figure 1, the wet motor pump 1 comprises a bowl 3 with a fluid inlet 5 and a fluid outlet 7, and a pump impeller 9 arranged inside the bowl 3. The fluid inlet constitutes the suction of the pump and the fluid outlet 7 corresponds to the discharge of the pump.

[0050] The wet motor pump 1 is advantageously of the centrifugal type, the fluid inlet 5 being axial and the fluid outlet 7 being radial.

[0051] The pump 1 also comprises a motor casing 11, secured to the bowl 3 and internally delimiting a chamber 13 in fluid communication with the bowl 3.

[0052] The wet motor pump 1 further comprises a motor 15 with a rotor 17 and a stator 19, arranged inside the chamber 13.

[0053] The wet motor pump 1 also comprises a shaft 21 on which the pump wheel 9 is fixed, the shaft 21 being driven in rotation about an axis of rotation X by the rotor 17.

[0054] The pump wheel 9 is rigidly fixed to a proximal end 23 of the shaft 21.

[0055] The proximal end 23 projects axially outside the motor casing 11, and is housed inside the bowl 3.

[0056] The rotor 17 is directly fixed on the shaft 21.

[0057] The stator 19 is arranged around the rotor 17, an air gap 25 separating the stator from the rotor.

[0058] The rotor 17 and the stator 19 are cylindrical in shape, and are coaxial with the axis of rotation X.

[0059] The motor casing 11 is designed to take the weight of the motor 15 and to transmit this weight to the structure supporting this motor. It has a rigidity suitable for these functions.

[0060] The motor casing 11 directly delimits the internal volume in which the motor 15, the shaft 21 and the shaft support bearings 21 are housed. The internal volume corresponds to the chamber 13.

[0061] The motor casing 11 comprises a ferrule 27 placed around the motor 15. The ferrule is cylindrical, coaxial with the axis X. The motor casing 11 also comprises a distal bottom 29, closing in a fluid-tight manner a distal end of the ferrule 27. The distal end corresponds to the end located, axially, opposite the pump wheel 9.

[0062] The motor casing 11 comprises an extension 31, extending the ferrule 27 axially towards the pump wheel 9. The extension 31 comprises a flange 33 for fixing to the proximal end of the ferrule 27. The extension 31 is tubular, coaxial with the axis X.

[0063] The motor casing 11 also comprises a proximal bottom 35 closing the extension 31 axially towards the pump wheel 9.

[0064] The bowl 3 is secured to the proximal bottom 35. The shaft 21 exits the chamber 13 through an opening 37 provided in the center of the proximal bottom 35. The chamber 13 is in fluid communication with the bowl 3 through the opening 37. The fluid can circulate along the shaft 21 between the interior of the bowl 3 and the interior of the chamber 13.

[0065] The pressures inside bowl 3 and inside chamber 13 are substantially equal.

[0066] A thermal barrier 39 is arranged in the chamber 13 along the section of the shaft 21 adjoining the opening 37. The thermal barrier 39 occupies one end of the extension 31.

[0067] The submerged motor pump 1 also comprises a heat exchanger 41 arranged inside the chamber 13, with a first side 43 in which the fluid circulates and a second side 45 in which a heat transfer fluid circulates.

[0068] The fluid circulating on the first side 43 and the heat transfer fluid circulating on the second side 45 are in thermal contact with each other through the wall of the exchanger 41.

[0069] The submerged motor pump 1 also comprises a circuit for cooling the motor 47 by the fluid, with a cooling passage 49 along which the fluid circulates in thermal contact with the motor 15.

[0070] The first side 43 of the heat exchanger is part of the engine cooling circuit 47, and is arranged downstream of the cooling passage 49.

[0071] The cooling circuit of the engine 47 is entirely housed inside the chamber 13, that is to say the engine casing 11.

[0072] The fluid circulating along the engine cooling circuit 47 rotates in a closed circuit inside the engine casing 11, without any outlet to the outside of this casing.

[0073] The heat exchanger 41 is arranged radially between the motor 15 and the shell 27.

[0074] More specifically, the heat exchanger 41 comprises a cylindrical membrane 51 having an external passage for the heat transfer fluid on a radially external face 53, and an internal passage for the fluid on a radially internal face 55. The cylindrical membrane 51 is coaxial with the axis X. It is made of a metal that conducts heat well, for example stainless steel.

[0075] It has a proximal end 57 facing axially towards the pump wheel 9, and a distal end 59 axially opposite the pump wheel 9.

[0076] The inner passage constitutes the first side 43 of the heat exchanger. The outer passage constitutes the second side 45 of the heat exchanger.

[0077] The external passage comprises at least one external helical groove 61 hollowed out in the radially external face 53 of the cylindrical membrane.

[0078] Typically, it comprises a plurality of external helical grooves 61 arranged parallel to each other in the radially external face 53. In the example shown, the external passage comprises twelve external helical grooves 61.

[0079] The or each external helical groove 61 wraps around the axis X, and extends over the entire axial length of the cylindrical membrane 51, from the proximal end 57 to the distal end 59.

[0080] Similarly, the internal passage comprises at least one internal helical groove 63 hollowed out in the radially internal face 55.

[0081] Preferably, the internal passage comprises a plurality of internal helical grooves 63, arranged parallel to each other. In the example shown, the internal passage comprises twelve internal helical grooves 63.

[0082] The or each internal helical groove 63 wraps around the axis X, and extends over the entire axial length of the cylindrical membrane 51, from the proximal end 57 to the distal end 59.

[0083] The or each external helical groove 61 has a first external depth in an axially central portion of the cylindrical membrane 51, and a second external depth less than the first external depth at the proximal end 57 and at the distal end 59.

[0084] The first depth is greater than 50% of the thickness of the cylindrical membrane 51, preferably greater than 75% of the thickness of the cylindrical membrane.

[0085] At the proximal end and distal end of the cylindrical membrane, the depth of the outer helical groove 61 gradually reduces. Thus, the last turn of the outer helical groove 61 is very shallow, the penultimate turn is a little deeper, etc.

[0086] Similarly, the internal helical groove 63 has a first internal depth in an axially central portion of the cylindrical membrane 51 and a second internal depth less than the first internal depth at the proximal end 57 and at the distal end 59 of the cylindrical membrane 51.

[0087] As seen in Figures 2 and 3, the first internal depth is greater than 50% of the thickness of the cylindrical membrane 51, preferably greater than 75% of the thickness of the cylindrical membrane 51.

[0088] The internal helical groove 63 at the proximal end 57 and at the distal end 59 has a depth which gradually reduces.

[0089] As seen in Figure 3, at the distal end 59, the last turn of the internal helical groove 63 has a very shallow depth. The penultimate turn has a slightly greater depth, etc.

[0090] At the proximal end 57, the depth of the internal helical groove 63 decreases only slightly, and remains for example greater than 50% of the thickness of the cylindrical membrane 51 at the level of the last turn (figure 2).

[0091] Thus, in its central portion, the cylindrical membrane 51 considered in section in a plane containing the X axis has a sinuous shape, of constant wall thickness. Each turn of an internal helical groove 63 is framed by two turns belonging to external helical grooves 61 (see figures 2 and 3). This makes it possible to obtain excellent heat exchange coefficients in the heat exchanger between the fluid and the heat transfer fluid.

[0092] The proximal end 57 and the distal end 59 of the cylindrical membrane 51 are welded to the inner surface of the motor housing 11 to fluidically isolate the outer passage from the inner passage.

[0093] More precisely, and as illustrated in FIG. 2, a lip 65 is formed on the radially external face 53 of the cylindrical membrane 51. This lip 65 is welded by a non-visible weld bead to a complementary lip 67, formed on the internal surface of the casing 11. The two lips 65, 67 are substantially cylindrical, the lip 67 being placed radially around the lip 65.

[0094] At the distal end 59, a lip 69 is provided on a radially internal face 55 of the cylindrical membrane 51. It is welded by a weld bead 71 to a complementary lip 73 provided on the internal surface of the casing. The lips 69 and 73 are substantially annular. The lip 73 axially adjoins the lip 69.

[0095] The pump 1 also comprises a stator casing 75, with a cylindrical metal jacket 77 interposed radially between the radially internal face 55 of the cylindrical membrane 51 and the stator 19.

[0096] The metal jacket 77 is made of a material having a good coefficient of heat transfer by conduction, for example stainless steel. The central portion of the cylindrical membrane 51 corresponds to the part of the cylindrical membrane 51 pressed against the jacket 77. It covers at least 70% of the axial length of the cylindrical membrane, preferably at least 80% of the axial length of the cylindrical membrane.

[0097] The stator frame 75 also comprises a proximal support ring 79 and a distal support ring 81 arranged axially on either side of the motor 15, rigidly fixed to two opposite axial ends of the metal sleeve 77.

[0098] A slice of the proximal support ring 79 is pressed against the radially inner face 55 of the cylindrical membrane 51 at the proximal end 57. In the same way, a slice of the distal support ring 81 is pressed against the radially inner face 55 of the cylindrical membrane 51 at the distal end 59.

[0099] Thus, the edges of the support rings 79, 81 are pressed against areas of the radially internal surface 55 in which the internal helical groove(s) 63 are of lesser depth. These areas therefore have a higher mechanical resistance than in the central portion.

[0100] The stator frame 75 further comprises two closing sheets 83, arranged on radially inner edges of the proximal support ring 79 and the distal support ring 81. The sheets 83 close on a radially inner side the volume located between the ring 79 and the stator 19 and the volume located between the stator 19 and the ring 81.

[0101] The stator coils 84 are housed in these volumes, and are isolated from the fluid by the closing plates 83, the support rings 79, 81, and by the metal jacket 77.

[0102] As can be seen in particular in FIG. 3, a distal volume 85 is delimited between the distal support ring 81 and the distal bottom 29 of the motor casing 11.

[0103] Figure 4 shows that the distal support ring 81 comprises at its periphery a plurality of orifices 87 fluidly connecting the distal volume 85 with the internal passage.

[0104] The orifices 87 are distributed over the periphery of the distal support ring 81. They are hollowed out on the edge, that is to say on the radially external surface, of the ring 81. They are open axially at one end so as to open into the distal volume 85. They are closed axially at the opposite end. They are open radially outwards so as to communicate with the internal helical groove(s) 63.

[0105] The pump 1 also includes a member 89 for circulating the fluid along the cooling circuit of the engine 47.

[0106] This member 89 is integral with the shaft 21 and is housed in the distal volume 85. Thus, it is driven in rotation with the shaft 21. In the example shown, the member 89 is a disc having a plurality of radial bores 90R, opening at a radially external edge of the disc.

[0107] The member 89 also comprises a plurality of axial bores 90A, each opening at its two ends at the two large opposite faces of the disc. Each radial bore 90R opens, at an internal end opposite the radially external edge of the disc, into one of the axial bores 90A.

[0108] The member 89 thus ensures the pump function in the engine cooling circuit. The radial bores allow the pumping effect to be generated by communicating kinetic energy to the fluid. The axial bores are used to supply fluid to the radial bores.

[0109] Alternatively and / or additionally, the member 89 comprises, for example, blades of the type used for centrifugal pumps in order to improve hydraulic efficiency.

[0110] The circulation member 89 expels the fluid radially outwards, up to the orifices 87.

[0111] As seen in Figure 1, pump 1 also includes:

[0112] - a proximal bearing 91, with a proximal fixed ring 93 mounted on the proximal support ring 79 and a proximal rotating ring 95 secured to the shaft 21;

[0113] - a distal bearing 97, with a distal fixed ring 99 mounted on the distal support ring 81 and a distal rotating ring 101 secured to the shaft 21.

[0114] The motor 15 is located axially between the two bearings.

[0115] The cooling passage 49 comprises a proximal volume 103 located axially between the proximal support ring 79 and the proximal bottom 35 of the motor casing 11, a proximal intermediate volume 105 located axially between the proximal bearing 91 and the rotor 17, the air gap 25 between the rotor and the stator, and a distal intermediate volume 107 located between the rotor 17 and the distal bearing 97. The cooling passage 49 further comprises the distal volume 85.

[0116] The proximal volume 103 is delimited axially on one side by the proximal support ring 79 and the proximal bearing 91. It is delimited axially on the opposite side by the thermal barrier 39. It is located inside the extension 31.

[0117] In order to allow circulation between the volumes 103 and 105, the proximal fixed ring 93 and / or the proximal rotating ring 95 comprise passages 109 for the circulation of fluid from the proximal volume 103 to the proximal intermediate volume 105. In the same way, the fixed distal ring 99 and / or the rotating distal ring 101 comprise passages 111 for the circulation of fluid from the distal intermediate volume 107 to the distal volume 85.

[0118] The pump 1 also comprises a heat transfer fluid inlet 113 and a heat transfer fluid outlet 115 fluidically connected to the second side 45 of the heat exchanger 41. The inlet 113 and the outlet 115 are for example arranged in the motor casing 11.

[0119] The pump 1 also comprises an inlet manifold 117 and an outlet manifold 119 fluidly connected respectively to the inlet 113 and the outlet 115.

[0120] The inlet manifold 117 is a groove hollowed out in the internal surface of the ferrule 27. It is located opposite the proximal end 57 of the cylindrical membrane 51. The outlet manifold 119 is a groove hollowed out in the internal surface of the ferrule 27. It is located opposite the distal end 59 of the cylindrical membrane 51.

[0121] Alternatively, the inlet manifold is on the distal side of the cylindrical membrane, and the outlet manifold on the proximal side.

[0122] The radially external surface 53 of the cylindrical membrane 51 is pressed against the internal surface of the ferrule 27. The or each external helical groove 61 at one end therefore opens into the inlet groove 117. The or each external helical groove 61 at its opposite end opens into the outlet groove 119.

[0123] The radially inner surface of the ferrule 27 closes the external passage on one radially outer side, except at the level of the grooves 117 and 119.

[0124] The sleeve 77, for its part, closes the internal passage on a radially internal side.

[0125] More precisely, it closes the central part of the internal passage.

[0126] The edges of the proximal and distal support rings 79, 81 partially close the internal passage at the proximal end 57 and at the distal end 59 of the cylindrical membrane. At the proximal end 57, the internal passage communicates with the proximal volume 103, the last turns of the or each internal helical groove 63 extending beyond the proximal support ring 79 and therefore not being covered by the edge of this ring.

[0127] The heat transfer fluid inlet 113 is provided to be connected to a heat transfer fluid supply conduit 121. The heat transfer fluid outlet 115 is provided to be connected to a heat transfer fluid discharge conduit 123.

[0128] The pump further comprises an inlet cut-off member 125 configured to selectively isolate or place in communication the heat transfer fluid inlet 113 and the heat transfer fluid supply conduit 121, and / or an outlet cut-off member 127 configured to selectively isolate or place in communication the heat transfer fluid outlet 115 and the heat transfer fluid discharge conduit 123.

[0129] The input cut-off member 125 is for example an on / off valve.

[0130] The output cut-off member 127 is, for example, an on / off valve.

[0131] The operation of the pump described above will now be detailed.

[0132] When the pump is in operation, the chamber 13 delimited by the motor casing is filled with the fluid. This is in pressure equilibrium with the internal volume of the bowl 3.

[0133] When the rotor 17 drives the pump wheel 9 into rotation, the circulation member 89 is also set into rotation. It causes the circulation of the fluid inside the chamber 13 along the cooling circuit of the engine 47.

[0134] Fluid flows in the cooling passage 49 from the proximal volume 103 to the proximal intermediate volume 105, through the passages 109 and also between the rings 93 and 95.

[0135] From the proximal intermediate volume 105, the fluid flows to the distal intermediate volume 107 along the air gap 25. In doing so, it cools the rotor 17 and the stator 19.

[0136] Fluid flows from distal intermediate volume 107 to distal volume 85 through passages 111 and between rings 99 and 101.

[0137] Within the distal volume 85, the fluid flows into the channels of the circulation member 89 and is propelled to the orifices 87.

[0138] The fluid then enters the internal passage of the heat exchanger 41, i.e. the first side 43 of the heat exchanger. It flows from the distal end 59 to the proximal end 57 of the cylindrical membrane 51, following the internal helical channel(s) 63.

[0139] Having reached the proximal end 57 of the cylindrical membrane, it returns to the proximal volume 103.

[0140] During its passage through the internal helical channel(s) 63, the fluid is in thermal contact both with the jacket 77 and with the heat transfer fluid flowing from the second side 45 of the heat exchanger 41.

[0141] The heat transfer fluid enters the pump through the inlet 113, and is directed to the inlet groove 117. It flows from the inlet groove 117 into the external passage, and more precisely follows the external helical channel(s) 61. It is collected in the outlet groove 119 and flows from there to the fluid outlet 115.

[0142] The nuclear reactor 129 shown in Figure 5 comprises:

[0143] - a core 131, comprising nuclear fuel assemblies; - a pressure vessel 133, containing the core 131, the pressure vessel 133 being filled with a primary heat transfer fluid up to a nominal level;

[0144] - at least one primary pump 135, arranged to circulate the primary heat transfer fluid in the core 131.

[0145] Nuclear reactor 129 is an integrated type. For example, it is an SM R.

[0146] It comprises steam generators 137 housed in the pressure vessel 133.

[0147] The core 131 is placed in the lower part of the pressure vessel 133. The steam generators 137 are housed above the core 131.

[0148] The nuclear reactor 129 also includes a pressurizer 139 delimited inside the vessel cover 141.

[0149] The or each primary pump 135 is arranged to circulate the primary heat transfer fluid inside the pressure vessel 133, in a loop. The primary heat transfer fluid passes through the core 131, then circulates through the steam generators 137, then is returned by the or each primary pump 135 to the core 131.

[0150] In the example shown, the nuclear reactor comprises several primary pumps 135, for example six primary pumps.

[0151] The or each primary pump 135 is a flooded motor pump of the type described above.

[0152] The or each primary pump 135 is mounted at a level lower than or equal to said nominal level of primary heat transfer fluid of the pressure vessel 133.

[0153] The nominal level of primary heat transfer fluid of the pressure vessel 133 corresponds, for example, substantially to the level of the contact plane between the flange of the pressure vessel and the cover 141.

[0154] The or each primary pump 135 is preferably mounted, in the vertical direction, between the core 131 and the steam generators 137. The vertical direction corresponds substantially to the axis of the pressure vessel 133.

[0155] The or each primary pump 135 is mounted on the pressure vessel 133, the shell 27 being placed outside the pressure vessel 133, the pump wheel 9 being placed inside the pressure vessel 133.

[0156] The or each primary pump 135 is mounted with its axis of rotation horizontal. The axis of rotation is typically radial relative to the central axis of the pressure vessel.

[0157] A radially external fixing flange 143 is formed at the proximal end of the ferrule 27. It is directly fixed to the pressure vessel 133. The extension 31 is engaged in an opening provided in the pressure vessel 133.

[0158] The pump described above has multiple advantages. Arranging the heat exchanger radially between the motor and the shell of the motor casing makes it very convenient to house the heat exchanger in the motor casing. This arrangement provides a large contact surface between the fluid and the heat transfer fluid.

[0159] When the heat exchanger comprises a cylindrical membrane having an external passage for the heat transfer fluid on a radially external face and an internal passage for the fluid on a radially internal face, the heat exchange between the fluid and the heat transfer fluid is carried out through the cylindrical membrane. This is particularly convenient for housing the heat exchanger inside the motor casing and organizing the circulation of the fluids, without excessively increasing the size of the pump.

[0160] When the external passage comprises at least one external helical groove hollowed out in the radially external face and / or the internal passage comprises at least one internal helical groove hollowed out in the radially internal face, the external passage and the internal passage are produced in a particularly compact manner, the heat exchanges being particularly good between the two passages.

[0161] Welding the cylindrical membrane to the inner surface of the motor casing at both ends makes it possible to conveniently achieve fluid isolation between the outer passage and the inner passage.

[0162] When the pump has a stator casing with a cylindrical metal sleeve interposed radially between the radially inner face of the cylindrical membrane and the stator, and closing the internal passage on one radially inner side, the heat released by the stator is transmitted by conduction directly into the fluid circulating in the internal passage. This optimizes the cooling of the stator.

[0163] Because the stator frame comprises a proximal support ring and a distal support ring arranged axially on either side of the motor, rigidly fixed to two opposite ends of the metal sleeve, a slice of the proximal support ring and a slice of the distal support ring being pressed against the radially internal surface of the cylindrical membrane respectively at the proximal end and the distal end, the membrane is held in position by the support rings.

[0164] When the external helical groove has a first external depth in an axially central portion of the cylindrical membrane and a second external depth less than the first external depth at the proximal end and at the distal end of the cylindrical membrane, the cylindrical membrane is mechanically stronger at both ends and can withstand the pressure exerted by the support rings.

[0165] Similarly, when the internal helical groove has a first internal depth in an axially central portion of the cylindrical membrane and a second internal depth less than the first internal depth at the proximal end and at the distal end of the cylindrical membrane, the membrane is mechanically stronger at both ends and can withstand the pressure exerted by the support rings.

[0166] When the distal support ring has at its periphery a plurality of orifices fluidly connecting the distal volume with the internal passage, the communication of the distal volume with the internal passage is carried out in a simple and convenient manner.

[0167] When the pump has a device for circulating the fluid along the cooling circuit, integral with the shaft and housed in the distal volume, circulating the fluid along the motor cooling circuit is carried out particularly simply.

[0168] When the proximal bearing has a proximal fixed ring and / or a proximal rotating ring with passages for fluid circulation, fluid circulation along the cooling passage is promoted. Similarly, when the distal bearing has a distal fixed ring and / or a distal rotating ring with passages for fluid circulation, fluid circulation is promoted along the cooling passage.

[0169] When the pump comprises an inlet cut-off member configured to selectively isolate or connect the heat transfer fluid inlet and the heat transfer fluid supply conduit and / or an outlet cut-off member configured to selectively isolate or connect the heat transfer fluid outlet and the heat transfer fluid discharge conduit, in the event of a rupture of the heat exchanger, the breach may be isolated from the heat transfer fluid supply conduit and / or the heat transfer fluid discharge conduit. The cut-off members are designed to withstand the pressure of the primary fluid.

[0170] The pump can have multiple variations.

[0171] The pump is not necessarily of the centrifugal type, but can be of any suitable type.

[0172] The fluid inlet into the bowl is not necessarily axial and the fluid outlet is not necessarily radial. The bowl could be attached directly to the shell of the motor casing, without the interposition of an extension.

[0173] The rotor is not necessarily directly mounted on the shaft; the shaft may, for example, be driven by the rotor via a reducer.

[0174] The external passage may include non-helical grooves, of any other suitable shape: straight, sinuous, etc.

[0175] The external passage may be achieved by means other than one or more grooves cut into the cylindrical membrane. For example, one or more grooves may be cut into the inner surface of the shell. Ribs defining fluid circulation channels between them may be welded onto the outer surface of the cylindrical membrane.

[0176] Similarly, the internal passage may include non-helical grooves, of any other suitable shape: straight, sinuous, etc.

[0177] The internal passage may be achieved by means other than one or more grooves cut into the cylindrical membrane. For example, one or more grooves may be cut into the external surface of the stator sleeve. Ribs defining fluid circulation channels between them may be welded onto the internal surface of the cylindrical membrane.

[0178] The heat exchanger can also be made in the form of a thicker cylindrical membrane with axial holes. The fluid circulates in one part of the axial holes and the heat transfer fluid in another part of the axial holes.

Claims

CLAIMS 1. Wet motor pump for a fluid, comprising: - a bowl (3) with a fluid inlet (5) and a fluid outlet (7); - a pump wheel (9), arranged inside the bowl (3); - a motor casing (11), integral with the bowl (3) and internally delimiting a chamber (13) in fluid communication with the bowl (3); - a motor (15) comprising a rotor (17) and a stator (19), arranged inside the chamber (13); - a shaft (21) on which the pump wheel (9) is fixed, the shaft (21) being driven in rotation around an axis of rotation by the rotor (17); - a heat exchanger (41) arranged inside the chamber (13), with a first side (43) in which the fluid circulates and a second side (45) in which a heat transfer fluid circulates; - a cooling circuit for the engine (47) by the fluid, with a cooling passage (49) along which the fluid circulates in thermal contact with the engine (15), the first side (43) of the heat exchanger (41) being part of the cooling circuit (47) and being arranged downstream of the cooling passage (49).

2. Pump according to claim 1, wherein the motor casing (11) comprises a shell (27) placed around the motor (15), the heat exchanger (41) being arranged radially between the motor (15) and the shell (27).

3. Pump according to claim 2, in which the heat exchanger (41) comprises a cylindrical membrane (51) having axially towards the pump wheel (9) a proximal end (57) and axially opposite the pump wheel (9) a distal end (59), the cylindrical membrane (51) having an external passage for the heat transfer fluid on a radially external face (53) and an internal passage for the fluid on a radially internal face (55).

4. Pump according to claim 3, in which the external passage comprises at least one external helical groove (61) hollowed out in the radially external face (53), and / or the internal passage comprises at least one internal helical groove (63) hollowed out in the radially internal face (55).

5. A pump according to claim 3 or 4, wherein the proximal end (57) and the distal end (59) of the cylindrical diaphragm (51) are welded to an inner surface of the motor housing (11) to fluidically isolate the outer passage from the inner passage.

6. Pump according to any one of claims 3 to 5, in which the pump (1) comprises a stator casing (75), with a cylindrical metal jacket (77) interposed radially between the radially internal face (55) of the cylindrical membrane (51) and the stator (19), and closing the internal passage on a radially internal side.

7. Pump according to claim 6, in which the stator frame (75) comprises a proximal support ring (79) and a distal support ring (81) arranged axially on either side of the motor (15), rigidly fixed to two opposite ends of the metal jacket (77), a slice of the proximal support ring (79) and a slice of the distal support ring (81) being pressed against the radially internal face (55) of the cylindrical membrane (51) respectively at the proximal end (57) and the distal end (59).

8. A pump according to claim 7 combined with claim 4, wherein the or each external helical groove (61) has a first external depth in an axially central portion of the cylindrical membrane (51) and a second external depth less than the first external depth at the proximal end (57) and at the distal end (59) of the cylindrical membrane (51); and / or the or each internal helical groove (63) has a first internal depth in an axially central portion of the cylindrical membrane (51) and a second internal depth less than the first internal depth at the proximal end (57) and at the distal end (59) of the cylindrical membrane (51).

9. Pump according to claim 7 or 8, in which a distal volume (85) is delimited between the distal support ring (81) and a distal bottom (29) of the motor casing (11), the distal support ring (81) comprising at its periphery a plurality of orifices (87) fluidly connecting the distal volume (81) with the internal passage.

10. Pump according to claim 9, in which the pump (1) comprises a member (89) for circulating the fluid along the cooling circuit of the motor (47), integral with the shaft (21) and housed in the distal volume (85).

11. Pump according to any one of claims 7 to 10, wherein the pump (1) comprises: - a proximal bearing (91) with a proximal fixed ring (93) mounted on the proximal support ring (79) and a proximal rotating ring (95) integral with the shaft (21); - a distal bearing (97) with a distal fixed ring (99) mounted on the distal support ring (81) and a distal rotating ring (101) secured to the shaft (21), the cooling passage (49) comprising a proximal volume (103) located axially between the proximal support ring (79) and a proximal bottom (35) of the motor casing (9), a proximal intermediate volume (105) located axially between the proximal bearing (91) and the rotor (17), an air gap (25) between the rotor (17) and the stator (19), a distal intermediate volume (107) located between the rotor (17) and the distal bearing (81), and the distal volume (85).

12. Pump according to claim 11, wherein the proximal fixed ring (93) and / or the proximal rotating ring (95) comprise passages (109) for the circulation of fluid from the proximal volume (103) to the proximal intermediate volume (105), the distal fixed ring (99) and / or the distal rotating ring (101) comprising passages (111) for the circulation of fluid from the distal intermediate volume (107) to the distal volume (85).

13. A pump according to any one of claims 1 to 12, wherein the pump comprises a heat transfer fluid inlet (113) and a heat transfer fluid outlet (115) fluidically connected to the second side (45) of the heat exchanger (41), the heat transfer fluid inlet (113) being adapted to be connected to a heat transfer fluid supply conduit (121), the heat transfer fluid outlet (115) being adapted to be connected to a heat transfer fluid discharge conduit (123), the pump comprising an inlet cut-off member (125) configured to selectively isolate or connect the heat transfer fluid inlet (113) and the heat transfer fluid supply conduit (121) and / or an outlet cut-off member (127) configured to selectively isolate or connect the heat transfer fluid outlet (115) and the heat transfer fluid discharge pipe (123).

14. Nuclear reactor (129) comprising: - a core (131), comprising nuclear fuel assemblies; - a pressure vessel (133), containing the core (131), the pressure vessel (133) being filled with a primary heat transfer fluid up to a nominal level; - at least one primary pump (135) according to any one of claims 1 to 13, arranged to circulate the primary heat transfer fluid in the core (1), mounted at a level lower than or equal to said nominal level.

15. Nuclear reactor according to claim 14, wherein the primary pump (135) is mounted on the pressure vessel (133), the shell (27) being placed outside the pressure vessel (33), the pump wheel (9) being placed inside the pressure vessel (133).

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