JP7079263B2 - Reactor pump - Google Patents

Description

The present invention generally relates to a nuclear reactor pump for operating the primary fluid of a nuclear reactor, particularly a primary pump.

More specifically, according to the first aspect, the present invention relates to a fluid pump for a nuclear reactor. This pump
-Still structure and
-A pump shaft that can rotate around a rotating shaft with respect to a stationary structure,
-With a pump wheel firmly fixed to the pump shaft,
-A guide structure for a fluid that is fixed to a stationary structure and driven by a pump wheel, the guide structure having a tubular section installed around the pump axis, and the guide structure for the fluid in which the pump wheel is installed. A guide structure that defines the inside of the circulation chamber,
-A heat barrier radially interposed between the tubular portion and the pump shaft, which is axially interposed along the pump shaft between the heat barrier body and the heat barrier body and the pump wheel. With a heat barrier cover, the heat barrier comprises a heat exchanger installed in a housing defined by the heat barrier cover, with a heat barrier,
-Provides a heat shield, which is radially interposed between the heat barrier and the tubular portion of the guide structure.

Such pumps typically include a diffuser that forms a tubular portion. It is possible to fix the heat shield to the tubular part. In that case, there is a gap between the heat shield and the heat barrier body.

Such pumps generally include a dynamic fluid resistant device with injection of sealing fluid along the pump shaft. This sealing fluid flows in the fluid resistant device, flows along the pump shaft, flows into the housing that receives the heat exchanger, then flows into the chamber above the wheel of the pump, and finally the primary. It flows into the fluid.

If the dynamic fluid resistant device fails, the hot primary fluid rises from the circulation chamber along the axis into the housing that receives the heat exchanger. The primary fluid flows into the dynamic fluid resistant device. In parallel with this mainstream, recirculation of the high temperature primary fluid occurs in the gap between the heat shield and the heat barrier body.

The heat from the primary fluid spreads through the thermal barrier body to the fluid resistant gasket placed around the pump shaft.

The heat output of the primary fluid rising through the exchanger is partially extracted by the exchanger. The main fluid recirculation between the shield and the heat barrier not cooled by the heat exchanger provides the heat output directly to the top of the heat barrier body and by diffusion to the cavity upstream of the fluid resistant body. .. Therefore, the temperature of the dynamic fluid resistant device is higher than that during operation of the pump with injection.

Nevertheless, the temperature of the seal must always be kept below 90 ° C for the pump to operate effectively.

The heat flow diffused through the heat barrier body is difficult to obtain this result.

In this regard, it is an object of the present invention to propose a pump in which it is easier to keep the fluid resistant gasket of the pump shaft below its maximum certified temperature.

For that purpose, the present invention has a heat shield inserted radially between the heat barrier body and the tubular portion and an upper heat shield inserted radially between the thermal barrier body and the tubular portion. The present invention relates to the above type of pump, characterized in that it is provided with an upper heat shield. The upper heat shield is pressed against the heat barrier body and the lower heat shield is pressed against the tubular portion.

Since the upper heat shield is pressed against the heat barrier, there is only a very thin gap between the body and the upper heat shield. There may actually be no fluid circulation between the heat barrier body and the upper heat shield. The heat flow diffused through the heat barrier body towards the seal of the pump shaft is reduced.

The pump may further comprise one or more of the following features, either individually considered or according to all technically possible combinations:
-The upper heat shield is firmly fixed to the heat barrier body.
-The upper heat shield has a lower axial end towards the lower heat shield, firmly secured to the tubular portion by fluid resistant peripheral welding.
-The upper heat shield is separated from the tubular portion by the upper gap, and the cavity between the upper heat shield and the lower heat shield fluidly connects the upper gap to the housing.
-The thermal barrier comprises at least one fluid pressure reducing device or fluid resistant device installed in the upper gap or cavity.
-The lower heat shield is firmly fixed to the tubular part.
-The lower heat shield is provided with an extension that engages the upper gap and is firmly secured to the tubular portion.
-The lower heat shield is separated from the heat barrier cover by a lower gap that communicates fluid with the housing.
-The lower heat shield and / or the upper heat shield comprises a box and a plurality of plates arranged parallel to each other within the box, the plates separated from each other by a liquid blade less than 1.5 mm thick.
-The thickness of each flat plate is less than 0.8 mm.
-Includes at least one shaft seal located around the pump shaft and a chamber radially located between the thermal barrier body and the pump shaft, the chamber being the pump shaft between the shaft seal and the housing. Arranged axially along, the pump further comprises a barrier fluid infusion device with an infusion circuit that injects the barrier fluid into the chamber, the barrier fluid flowing along the pump axis along the path from the chamber to the housing. Then flow from the housing to the fluid circulation chamber.
-The guide structure comprises a spiral portion that internally defines the circulation chamber and a diffuser that is disposed within the spiral portion and forms a tubular portion.
-The upper heat shield and the lower heat shield are two mutually independent structures.
-The heat barrier body and the heat barrier cover are two separate structures.
-The tubular section is radially inwardly defined by a substantially cylindrical surface coaxial with the axis of rotation, and the thermal barrier body is radially outwardly defined by a substantially cylindrical surface coaxial with the axis of rotation. The upper heat shield is installed between the surface of the tubular portion and the surface of the heat barrier body.

According to the second aspect, the present invention relates to a nuclear reactor including a container in which a nuclear fuel assembly is installed and a primary circuit. This container is equipped with a primary fluid inlet and a primary fluid outlet. The primary circuit comprises a pump having the above characteristics arranged to fluidly connect the primary fluid outlet to the primary fluid inlet and ensure circulation of the primary fluid from the container's primary fluid outlet to the primary fluid inlet.

Other features and advantages of the invention will be apparent from the detailed description provided below, but not exclusively for information, with reference to the accompanying drawings.
Partial view of the primary reactor pump according to the present invention. Enlarged view of the heat barrier and heat shield of the pump of FIG. Enlarged view of detail part III of FIG. Enlarged view of detail part IV of FIG.

The pump shown in FIG. 1 is for operating the fluid of the nuclear reactor. Typically, this pump is a primary pump for operating the primary fluid of a nuclear reactor.

In a pressurized water reactor (PWR), the reactor comprises a vessel containing a nuclear fuel assembly and a steam generator. The steam generator has a primary side and a secondary side, and the primary fluid and the secondary fluid circulate respectively, and the primary fluid applies a part of the heat energy to the secondary fluid in the steam generator. The reactor comprises a primary circuit connecting the primary fluid outlet of the vessel to the primary inlet of the steam generator and the primary outlet of the steam generator to the primary fluid inlet of the vessel. The pump is inserted into the primary circuit to ensure the circulation of the primary fluid in the primary circuit.

In a variant, the pump is a secondary pump that is inserted into the secondary circuit of a nuclear reactor. The secondary pump ensures the circulation of the secondary fluid between the secondary side of the steam generator and the steam turbine.

In a boiling water reactor (BWR), the primary circuit connects the reactor vessel directly to the steam turbine. In this case, the pump is inserted in the primary circuit between the turbine and the primary fluid inlet of the vessel.

In a variant, the pump is used in other circuits of the reactor to operate any type of fluid.

As shown in FIG. 1, the pump comprises a stationary structure 3 provided to be tightly connected to the civil engineering structure of the reactor by various devices not shown in FIG. The stationary structure 3 is only partially shown in FIG. The stationary structure 3 particularly includes a primary flange 5 and a motor support portion 7. Such parts are connected to each other by any suitable means.

The pump 1 further includes a pump shaft 9 that is rotatable with respect to the stationary structure 3 around the rotation shaft X. The axis of rotation X is typically substantially vertical.

The pump 1 typically comprises a motor (not shown) housed above the motor support 7. The motor drives the rotation of the pump shaft 9.

The pump 1 further comprises a pump wheel 11 firmly fixed to the pump shaft 9.

In the illustrated example, the pump wheel 11 is firmly fixed to the lower end 13 of the pump shaft 9.

Further, the pump 1 comprises a guide structure 15 for the fluid driven by the pump wheel 11. The guide structure 15 internally defines a fluid circulation chamber 17 in which the pump wheel 11 is located.

In FIG. 1, it can be seen that the guide structure 15 includes a tubular portion 19 arranged around the pump shaft. The tubular portion 19 is coaxial with the axis X.

More specifically, the guide structure 15 includes a spiral portion 21 that internally defines the circulation chamber 17. The spiral portion 21 is firmly fixed to the stationary structure 3, more specifically, the main flange 5.

In the illustrated example, the pump 1 is spiral centrifugal and the spiral portion 21 has a fluid inlet 23 located below the pump wheel 11 at its extension along the axis X. A fluid outlet (not shown) is arranged in the spiral portion 21 along the radial direction with respect to the axis X.

Further, the guide structure 15 includes a diffuser 25 arranged inside the spiral portion 21. Advantageously, the diffuser 25 forms a tubular portion 19. The diffuser 25 is also firmly fixed to the stationary structure 3 by any suitable means.

The diffuser 25 typically comprises a fluid guide 27 that extends the tubular portion 19 downwards. The guide portion 27 is arranged in an extension of the pump wheel 11 and has an internal passage 29 that guides the fluid discharged by the pump wheel toward the chamber 17.

The spiral portion 21 has an upper portion 31 that forms a flange 31 that is firmly fixed to the main flange 5.

The tubular portion 19 includes an upper segment 33 that forms a flange disposed inside the flange 31. The tubular portion 19 also includes an intermediate segment 35 that connects the upper segment 33 to the lower guide portion 27.

The tubular portion 19 is a pipe for passing through the pump shaft 19 and internally defines a pipe for accommodating various devices described later.

The pump 1 further comprises a thermal barrier 37 inserted radially between the tubular portion 19 and the pump shaft 9.

The heat barrier 37 includes a heat barrier main body 39 and a heat barrier cover 41.

The heat barrier body 39 is tubular and surrounds the pump shaft 9. The thermal barrier body 39 is substantially located along the axis X in the flange forming upper segment 33.

The cover 41 is axially inserted along the pump shaft 9 between the heat barrier body 39 and the pump wheel 11.

The cover 41 and the heat barrier body 39 are two separate structures.

The cover 41 is fixed to the heat barrier body 39 on its lower surface. The cover 41 is substantially located in the upper segment 33 and the intermediate segment 35.

More specifically, in FIG. 1, it can be seen that the tubular portion 19 defines an annular volume accommodating the heat barrier 37 between the pump shaft 9 and the tubular portion 19. This annular volume is axially closed towards the pump wheel 11 by a ring-shaped wall 43 that forms part of the diffuser 25. This annular volume is radially outwardly defined by segments 33 and 35. This annular volume is radially inwardly defined by the pump shaft 9.

The heat barrier 37 further comprises a heat exchanger 45 disposed within the housing 47 defined by the heat barrier cover 41. The housing 47 is cylindrical and completely surrounds the pump shaft 9. The housing 47 is axially closed toward the pump wheel 11 by the annular wall 49 of the thermal barrier cover. The housing 47 is radially outwardly closed by the cylindrical wall 51 of the thermal barrier cover. The housing 47 is axially closed on the opposite side of the pump wheel by the thermal barrier cover 39. The housing 47 is radially inwardly closed by a labyrinth ring 53 fixed to the thermal barrier body.

The heat barrier 37 further includes a coolant supply unit 55. The heat barrier 37 is connected to the heat exchanger 45 and circulates the cooling agent inside the heat exchanger 37.

Further, the heat shield 57 is inserted radially between the heat barrier 37 and the tubular portion 19. The heat shield 57 will be described in detail below.

The pump 1 typically comprises one or several shaft seals installed around the pump shaft 9. In the illustrated example, the pump comprises three shaft seals 59, 61, 63 mounted axially behind each other. In addition to the bearing 65, such a seal is axially separated from the pump wheel 11 by a thermal barrier 37. The exchanger built into the thermal barrier 37 makes it possible to thermally protect the shaft seal in the event of loss of barrier fluid supply.

The bearing 65 provides rotation guidance for the pump shaft 9. The bearing 65 is housed in a chamber 66 radially defined between the thermal barrier body 39 and the pump shaft 9. The bearing 65 is radially fixed to the lower portion of the thermal barrier body 39.

The chamber 66 is axially located along the pump shaft 9 between the shaft seal 59 and the thermal barrier housing 47. The chamber 66 is arranged radially between the heat barrier body 39 and the pump shaft 9.

Typically, the pump 1 further comprises a device 67 for injecting a barrier fluid. The barrier fluid helps prevent the fluid from rising through the pump assembly to the shaft seal devices 59, 61, 63.

The device 67 includes a circuit 69 provided for injecting a cold barrier fluid into the chamber 66. The cold barrier fluid circulates through the shaft seals 59, 61, 63 and towards the chamber 17 of the spiral portion 21.

The flow of the barrier fluid follows a path 71 from chamber 66 to housing 47 and then from housing 47 to circulation chamber 17 along the pump shaft 9.

As more specifically shown in FIG. 2, the heat shield 57 is provided between the upper heat shield 73 radially interposed between the heat barrier body 39 and the tubular portion 19, and between the heat barrier cover 41 and the tubular portion 19. It is provided with a lower heat shield 75 that is interposed in the radial direction.

The upper and lower heat shields are two independent structures. That is, they are not firmly fixed to each other.

The upper heat shield 73 is cylindrical and coaxial with the axis X. The upper heat shield 73 is arranged around the heat barrier main body 19.

The upper heat shield 73 is pressed against the heat barrier body 39. Here, "pressed" refers to the fact that the upper heat shield 73 is in contact with the heat barrier body or is separated from the heat barrier body by a very thin gap. This thickness is typically less than 2 mm, preferably less than 1 mm.

Conversely, the upper heat shield 73 is separated from the tubular portion 19 by an upper gap 76, which is more clearly visible in FIGS. 3 and 4 in detail. The gap 76 has a thickness of more than 3 mm, preferably more than 5 mm.

In FIG. 1, it can be clearly seen that the upper heat shield 73 is radially interposed between the heat barrier body 39 and the flange forming upper segment 33 of the tubular portion.

More specifically, the thermal barrier body 39 comprises a tubular portion 78 that defines the chamber 66 radially outward. The thermal barrier body 39 further comprises a flange 79 projecting radially outward from the upper end of the portion {79}. The flange 79 is axially sandwiched between the main flange 5 and the upper segment 33.

The thermal barrier body {79} further comprises a retracted portion 80 that extends the lower end of the tubular portion {79} inward in the radial direction and extends axially toward the pump wheel. The pull-in portion 80 separates the chamber 66 from the housing 47.

The upper heat shield 73 is firmly fixed to the heat barrier body 39.

More specifically, the upper heat shield 73 has a lower axial end 81 facing the lower heat shield 75 fixed to the heat barrier body 19.

The lower axial end portion 81 is fixed to the heat barrier main body 39 by the fluid resistant circumferential welded portion 82. The welded portion 82 extends over the entire circumference of the thermal barrier body {79}. Therefore, the gap between the heat barrier body 39 and the upper {screen} 73 is closed by the welded portion 82 and the lower part so as not to allow fluid to pass through, and the liquid between the upper heat shield 73 and the heat barrier body 39 Prevent any circulation.

The tubular portion 19 is radially inwardly defined by a substantially cylindrical surface 83 coaxial with the axis X. The thermal barrier body 39, and more specifically the cylindrical portion 79 of the body, is radially outwardly defined by a substantially cylindrical surface 84 coaxial with the axis X. The upper heat shield 73 is arranged between the surface 83 and the surface 84.

The upper heat shield 73 is defined inward in the radial direction by the inner surface 85. The surface 85 is typically substantially cylindrical and coaxial with the axis X.

The inner surface 85 is pressed against the surface 84 of the heat barrier body 39.

Typically, the axially lower zone of the surface 85 is in direct contact with the facing zone of the surface 84 or is separated from the facing zone by a gap less than 1 mm thick, eg, 0.5 mm thick. The rest of the surface 85 is separated from the surface 84 by a slightly larger thickness, eg, a gap of 0.5-1.5 mm.

As described above, the lower heat shield 75 is pressed against the tubular portion 19. The lower heat shield 75 is firmly fixed to the radial inner surface 83 by welding. The lower heat shield 75 is pressed against the intermediate segment 35 of the tubular portion 19. The lower heat shield 75 is cylindrical and coaxial with the axis X.

The lower heat shield 75 is separated from the heat barrier cover 41 by the lower gap 86 and communicates with the housing 47 in fluid communication. As shown, the lower heat shield 75 is inserted between the wall 51 of the heat barrier cover and the tubular portion 19. The wall 51 is radially outwardly defined by a substantially cylindrical surface 87. The lower gap 86 is defined inward in the radial direction by the surface 87 and outward in the radial direction by the lower heat shield 75.

In particular, as shown in FIGS. 2 and 3, there is a cavity 88 between the upper heat shield and the lower heat shield. The volume of the cavity 88 depends on the connection between the heat barrier cover 39 and the heat barrier body, the design of the lower and upper heat shields, their fixation, as well as their respective deformations of the pump during various operating conditions. The volume of the cavity 88 will be minimized to limit the thermal bridge between the chamber 17 and the thermal barrier 37.

In other words, the upper heat shield 73 and the lower heat shield 75 are slightly axially separated from each other. However, this spacing should be maintained above the minimum value, for example 1.5 mm.

The lower gap 86 also communicates with the cavity 88 in fluid. A gap 89 is arranged between the heat barrier body 39 and the heat barrier cover 41 (FIG. 3) to fluidly connect the cavity 88 and the housing 47.

As seen in FIGS. 3 and 4, the lower heat shield 75 includes an extension 91 that engages the upper gap 76 and is firmly secured to the tubular portion 19. The extension 91 has a cylindrical shape. The extension 91 extends the radial outer wall of the lower heat shield 75. The extension 91 extends over the entire axial height of the upper heat shield 73. The upper edge 93 of the extension 91 is welded to the tubular portion 19 by the weld bead 95 visible in FIG.

This extension allows the lower heat shield to be conveniently secured to the tubular portion 19. The extension 91 actually rises to the height of the flange forming upper segment 33 and can be easily welded.

In particular, as seen in FIGS. 2 and 3, the thermal barrier 37 advantageously comprises at least one fluid pressure reducing device or fluid resistant device 97 installed in the upper gap 76 or cavity 88. This device is provided to limit or prevent the circulation of fluid in the upper clearance 76, particularly the primary fluid rising from the housing 47 in the absence of the dynamic fluid resistant device 67. In the illustrated example, the device 97 is inserted between the upper heat shield 73 and the extension 91.

In one modification, the device 97 is inserted between the upper heat shield 75 and the lower heat shield 73 in the cavity 88. The device 97 is of all types such as metal blades, braids, labyrinth seals, fluid resistant gaskets, segments and the like.

In the example shown in FIGS. 2 and 3, the device 97 is fixed to the lower end of the upper heat shield. In one variant, the device 97 is mounted differently and is compressed between, for example, two screens.

As seen in FIGS. 3 and 4, the upper heat shield 73 and the lower heat shield 75 typically have the same structure. Each of the two heat shields preferably comprises a cylindrical box 99 and a plurality of flat plates 101 arranged parallel to each other in the box 99. The box 99 and the flat plate 101 are typically made of metal. Each of the flat plates 101 has a cylindrical shape and is installed in parallel in a concentric circle with each other. The flat plate 101 has a thickness of, for example, less than 0.8 mm, typically 0.4 mm.

The flat plates are advantageously separated from each other by a liquid blade 103 having a thickness of less than 1.5 mm. The thickness of the liquid blade is, for example, 1 mm. Each screen comprises a large number of flat plates, preferably at least 30 flat plates 101, and even more preferably at least 40 flat plates 101.

By choosing to provide a thin liquid blade and thus a large number of plates, convection of liquid between the plates can be restricted.

The spacer 105 makes it possible to maintain the separation between the flat plates 101. In the example shown in FIG. 3, the spacer 105 is fixed to the top cover 107 of the box.

Orifices such as the orifice 109 allow the upper shield to be emptied during pump hydraulic maintenance work.

During normal operation, the supply unit 55 injects the coolant into the heat exchanger 45. Further, the device 67 injects the barrier fluid into the chamber 66, and the barrier fluid flows into the housing 47 along the circulation path 71 as well as the fluid resistant gaskets 59, 61, 63, and then from the housing 47 to the circulation chamber 17. Inflow to. Therefore, this barrier fluid fills the chamber 47, the cavity 88 and the upper gap 76 and the lower gap 86. The upper heat shield 73 and the lower heat shield 75 are also filled with a fluid, such as a barrier fluid. This barrier fluid is typically water.

By injecting the barrier fluid, the primary fluid does not rise along the pump shaft 9 and the seals 59, 61, 63 and is thus maintained at their respective nominal temperatures.

Further, heat conduction from the circulation chamber 17 through the diffuser 25 to the seals 59, 61, 63 is limited by the presence of the cold barrier fluid 67 injector, heat exchanger 47, upper heat shield 73 and lower heat shield 75. To.

If the dynamic fluid resistant device fails due to the injection of the barrier fluid, the barrier fluid will not circulate any further along the pump shaft 9. The pressurized primary fluid that fills the circulation chamber 17 then rises along the axis to the housing 47 and is partially cooled by the heat exchanger 45. Recirculation occurs between the housing 47 and the gap 86 defined between the heat barrier cover 41 and the lower heat shield 73.

The fluid pressure reducing device or the fluid resistant device 97 limits the recirculation of the upper gap 76. Conversely, the primary fluid cannot circulate between the heat barrier body 39 and the upper heat shield 73. The contribution of heat output caused by the recirculation that may occur at the top is eliminated. Therefore, heat transfer by conduction through the heat barrier body 39 is limited. As a result, in addition to the seal 59, the temperature rise of the seals 61 and 63 is also restricted.

Conversely, the fact that the lower gap 86 always communicates with the housing 47 makes it possible to obtain a uniform temperature within the thermal barrier cover 41. This becomes an advantage over time for the mechanical strength of this cover.

Claims (15)

The pump (1) is a fluid pump for a nuclear reactor.
-Still structure (3) and
-A pump shaft (9) rotatable around the rotation shaft (X) with respect to the stationary structure (3),
-With the pump wheel (11) firmly fixed to the pump shaft (9),
-A fluid guide structure (15) fixed to the stationary structure (3) and driven by the pump wheel (11), wherein the guide structure (15) is around the pump shaft (9). A guide structure (15) comprising an installed tubular portion (19), wherein the guide structure (15) internally defines a fluid circulation chamber in which the pump wheel (11) is installed.
-A heat barrier (37) radially interposed between the tubular portion (19) and the pump shaft (9), wherein the heat barrier (37) is a heat barrier body (39) and the heat. A heat barrier cover (41) is provided between the barrier body (39) and the pump wheel (11) in the axial direction along the pump shaft (9), and the heat barrier (37) is the heat. A heat barrier (37) comprising a heat exchanger (45) installed in a housing (47) defined by a barrier cover (41).
-The heat shield (57) in a pump comprising a heat shield (57) radially interposed between the heat barrier (37) and the tubular portion (19) of the guide structure (15). The upper heat shield (73) inserted radially between the heat barrier body (39) and the tubular portion (19), and the heat barrier cover (41) and the tubular portion (19). With a lower heat shield (75) inserted radially between them, the upper heat shield (73) is pressed against the heat barrier body (39), and the lower heat shield (75) is the tubular portion (19). ) ,
By pressing the upper heat shield (73) against the heat barrier body (39), the recirculation of the primary fluid between the upper heat shield (73) and the heat barrier body (39) is restricted . A featured pump. The pump according to claim 1, wherein the upper heat shield (73) is firmly fixed to the heat barrier body (39). The upper heat shield (73) has a lower axial end (81) facing the lower heat shield (75), and the lower axial end (81) is welded around fluid resistant (82). Fixed to the heat barrier body (39),
2. The pump according to claim 2 . The upper heat shield (73) is separated from the tubular portion (19) by an upper gap (76), and a cavity (88) between the upper heat shield (73) and the lower heat shield (75) is formed. The pump according to any one of claims 1 to 3, wherein the upper gap (76) is fluidly connected to the housing (47). The thermal barrier (37) is characterized by comprising at least one fluid pressure reducing device or fluid resistant device (97) installed in the upper gap (76) or the cavity (88). 4. The pump according to 4. The pump according to any one of claims 1 to 5, wherein the lower heat shield (75) is firmly fixed to the tubular portion (19). The lower heat shield (75) comprises an extension (91) firmly fixed to the tubular portion (19), the extension (91 ) adjacent to the upper gap (76) and said. The pump according to claim 6 , wherein the lower heat shield (75) is firmly fixed to the tubular portion (19) . One of claims 1 to 7, wherein the lower heat shield (75) is separated from the heat barrier cover (41) by a lower gap (86) that communicates with the housing (47). The pump described in the section. The lower heat shield (75) and / or the upper heat shield (73) comprises a box (99) and a plurality of flat plates (101) arranged parallel to each other in the box (99). The pump according to any one of claims 1 to 8, wherein the flat plate (101) is separated from each other by a liquid blade (103) having a thickness of less than 1.5 mm. The pump according to claim 9, wherein each flat plate (101) has a thickness of less than 0.8 mm. At least one shaft seal (59, 61, 63) arranged around the pump shaft (9) and a radially arranged chamber between the thermal barrier body (39) and the pump shaft (9). (66), the chamber (66) is axially disposed along the pump shaft (9) between the shaft seals (59, 61, 63) and the housing (47). The pump further comprises a barrier fluid injection device (67) comprising an injection circuit (69) for injecting the barrier fluid into the chamber (66), the barrier fluid from the chamber (66) to the housing (47). ), Which flowes along the pump shaft (9) and then flows from the housing (47) to the fluid circulation chamber (17), according to any of claims 1-10. The pump according to item 1. The guide structure (15) has a spiral portion (21) that defines the circulation chamber (17) inward, and a diffuser that is arranged in the spiral portion (21) to form the tubular portion (19). (25) The pump according to any one of claims 1 to 11, characterized in that the pump comprises the above. The pump according to any one of claims 1 to 12, wherein the upper heat shield (73) and the lower heat shield (75) are two mutually independent structures. The pump according to any one of claims 1 to 13, wherein the heat barrier body (39) and the heat barrier cover (41) are two separate structures. The tubular portion (19) is radially inwardly defined by a substantially cylindrical surface (83) coaxial with the axis of rotation (X), and the thermal barrier body (39) is the axis of rotation (X). Defined radially outward by a substantially cylindrical surface (84) coaxial with the tubular portion (19), the upper thermal shield (73) is the surface (83) of the tubular portion (19) and the thermal barrier body (39). 14. The pump according to claim 14, wherein the pump is installed between the surface (84) and the surface of the pump.

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