EP1902266A1

EP1902266A1 - Heat exchanger assembly which is intended, in particular, for a high-temperature nuclear reactor

Info

Publication number: EP1902266A1
Application number: EP06778635A
Authority: EP
Inventors: Alain Cros
Original assignee: Areva NP SAS
Current assignee: Areva NP SAS
Priority date: 2005-06-27
Filing date: 2006-06-22
Publication date: 2008-03-26
Anticipated expiration: 2026-06-22
Also published as: EP1902266B1; ATE413577T1; CN101208577A; FR2887618A1; RU2414661C2; KR101329537B1; JP2008546985A; CN100559108C; US20100038062A1; JP4714267B2; RU2008102989A; ZA200710875B; DE602006003562D1; WO2007000507A1; US8081729B2; KR20080025694A; FR2887618B1

Abstract

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

Description

Heat exchange assembly, especially for high temperature nuclear reactor

The invention generally relates to heat exchangers, in particular for high temperature (HTR) or very high temperature (VHTR) nuclear reactor.

More specifically, the invention relates to a heat exchange assembly between a first and a second fluid, of the type comprising:

an outer enclosure having a central axis and provided with at least one inlet and one outlet of the first fluid and at least one inlet and one outlet of the second fluid,

a central collector extending along the central axis and communicating with one of the inlet and the outlet of the first fluid,

an annular collector disposed around the central collector and communicating with the other of the inlet and the outlet of the first fluid,

a plurality of heat exchangers distributed around the central axis and radially interposed between the central collector and the annular collector,

a plurality of axial input collectors communicating with the inlet of the second fluid, and a plurality of axial output collectors communicating with the outlet of the second fluid, the axial input and output collectors being interposed circumferentially between the exchangers, each exchanger comprising a plurality of circulation channels of the first fluid between the central and annular collectors, and a plurality of circulation channels of the second fluid from at least one inlet manifold to at least one outlet collector.

Sets of this type are known from JP-2004/144242, which discloses a heat exchange assembly provided with a secondary fluid inlet for each input axial manifold. In such an assembly, each input is generally connected to the corresponding input axial collector by a welded pipe. In operation, the connection between the pipe and the manifold is highly thermomechanically stressed. It therefore presents a risk of premature rupture. In this context, the invention aims to provide a heat exchange assembly where the risk of such breaks is greatly reduced, both in normal operation and in an accident situation.

For this purpose, the invention relates to an assembly of the above-mentioned type, characterized in that it comprises an inlet chamber provided with a first axial side of the exchangers, placing the inlet (s) of the second fluid in communication with minus several axial input collectors.

The assembly may also have one or more of the following characteristics, considered individually or in any technically feasible combination:

the inlet chamber has an annular shape and surrounds the central collector;

it comprises an outlet chamber provided with a second axial side of the exchangers opposite to the first, placing the second fluid outlet (s) in communication with at least several of the axial outlet manifolds;

- It comprises a visiting channel extending the central collector axially of the second side and isolated therefrom by a removable hatch, the outlet chamber having an annular shape and surrounding the inspection channel; at least the exchangers, the inlet and outlet chambers, and the axial inlet and outlet manifolds are assembled in a mechanical subassembly that can be extracted in one piece from the enclosure;

- The enclosure is vertical central axis, the enclosure comprising a vessel inside which is disposed the subassembly and having upwardly an extraction opening of said subassembly, and a removable closure cover tight of the opening of the tank;

- The vessel comprises a cylindrical shell coaxial with the central axis in which are formed the inlet and outlet of the second fluid, the inlet and outlet chambers being sealingly connected to the inlet and outlet of the second fluid by cuffs. removable, retractable inside the rooms;

- the cuffs are likely to be dismounted from inside the rooms; - The enclosure comprises several inputs and several outputs of the second fluid, these inputs and outputs being collected on the same circumferential half of the ferrule;

- The subassembly comprises a cylindrical outer envelope coaxial with the central axis delimiting radially outwardly the outlet chamber and the annular collector;

the assembly comprises lower coaxial inlet and outlet collectors communicating respectively with the inlet and the outlet of the first fluid and arranged under the subassembly, the latter being delimited in the lower part by a convergent frustoconical envelope from of the cylindrical envelope, this frustoconical envelope surrounding the central collector and defining therewith the annular collector, the lower manifolds ending upwardly by flanges capable of sealingly receiving the lower free ends of the central collector and the frustoconical envelope by simple interlocking;

- The central collector has a manhole closed by a removable door, communicating with the inlet chamber and the inspection channel has an opening communicating with the outlet chamber;

the enclosure has a lower bottom, and in that the assembly comprises a circulation member fixed to the lower bottom adapted to suck the first fluid leaving the annular channel or the central channel and to push it towards the outlet of the first fluid;

the axial inlet and outlet manifolds, the central collector and the annular collector have passage sections sufficient to allow an operator to intervene directly on the exchangers;

the inlet and the outlet of the first fluid are coaxial;

the exchangers are arranged regularly spaced in a circle around the central axis, each axial collector being delimited inwards and outwards by inner and outer circumferential plates welded to the two exchangers between which said collector extends; ;

- The annular collector is delimited inward by the exchangers and the outer plates; - The central collector is defined by the exchangers and the inner sheets;

each heat exchanger comprises a plurality of heat exchange modules stacked axially; the modules present perpendicularly to the central axis a rectangular section and have machined angles over the entire axial height of the exchanger, the latter further comprising forged and / or machined metal bars arranged in machined angles and on which are welded modules; and the bars each have a wing projecting circumferentially with respect to the modules towards the adjacent axial collector, on which is welded the inner or outer plate delimiting said axial collector.

According to a second aspect, the invention relates to the use of the assembly having the characteristics described above: with a first fluid mainly comprising helium and a second fluid mainly comprising helium and / or nitrogen;

with a first fluid mainly comprising helium and a second fluid mainly comprising water, the second fluid being vaporized in the exchanger assembly; with first and second fluids mainly comprising water, the second fluid being vaporized in the exchanger assembly; and

one of the first or the second fluid comes from a nuclear reactor. Other characteristics and advantages of the invention will emerge from the description which is given below, by way of indication and in no way limitative, with reference to the appended figures among which:

- Figure 1 is a perspective view of the heat exchange assembly of the invention, with a cutaway revealing the internal parts of the assembly;

- Figure 2 is an axial sectional view of the assembly of Figure 1 taken along the sectional plane M-II of Figure 3;

- Figure 3 is a sectional view of the assembly of Figure 2, perpendicular to its axis taken along the plane III-III of Figure 2; - Figure 4 is a sectional view of the assembly of Figure 2, perpendicular to its axis taken along the plane IV-IV of Figure 2;

FIG. 5 is a sectional view of the assembly of FIG. 2, perpendicular to its axis taken along the plane V-V of FIG. 2, showing the arrangement of the heat exchangers;

FIGS. 6A and 6B are diagrammatic representations showing the flow direction respectively of the first and second fluids through the heat exchangers of FIG. 5, and FIG. 6C is an exploded view of the plates of an exchanger of FIG. 5. FIG. 7 is a perspective view of a module of a heat exchanger of FIGS. 1 and 2;

FIGS. 8A and 8B are enlarged views from above of parts VIIIA and VIIIB of FIG. 7;

FIG. 9 is a partial exploded view of the assembly of FIG. 1, showing the removable mechanical subassembly comprising the heat exchangers and the collectors, uncoupled from the lower part of the enclosure, this enclosure being partially torn off;

FIGS. 10A and 10B are enlarged views of parts XA and XB of FIG. 2; Fig. 11 is an enlarged view of portion X1 of Fig. 2;

FIG. 12 is an enlarged view of part XII of FIG. 2; and

- Figure 13 is a block diagram illustrating the means implemented in a nuclear reactor to remove the mechanical subassembly of Figure 10 of the outer enclosure. The assembly 1 shown in FIGS. 1 and 2 is intended to be used in a high temperature or very high temperature nuclear reactor (HTR / VHTR), to achieve a heat exchange between a first fluid and a second fluid.

The first fluid is the primary fluid of the nuclear reactor, and circulates in a closed loop therein. It crosses the heart of the nuclear reactor (not shown), then crosses the assembly 1 and finally returns to the entrance of the heart. The primary fluid is heated in the reactor core, and leaves it for example at a temperature of approximately 850 ^° C. It yields a portion of its heat secondary fluid in the assembly 1, and leaves it for example at a temperature of 450 ⁰ C. The primary fluid is typically substantially pure helium gas.

The second fluid is the secondary fluid of the nuclear reactor, and circulates in a closed loop therein. It passes through the assembly 1, then passes into a gas turbine driving an electric generator and returns to the input of the assembly 1. The secondary fluid enters the assembly 1, for example at a temperature of 405. About ⁰ C and comes out for example at

About 805 ^° C. The secondary fluid is a gas comprising mainly helium and nitrogen.

Set 1 includes:

an outer enclosure 2 having a substantially vertical central axis X, provided with an inlet 4 and a primary fluid outlet 6, four inlets 8 and four outlets 10 of the secondary fluid; - Eight heat exchangers 12 disposed in the chamber 2, in which are carried out the heat exchange between the primary and secondary fluids;

collectors 14 and 16 for circulating the primary fluid inside the chamber 2; - Collectors 18 and 20 of secondary fluid circulation inside the chamber 2;

an inlet chamber 22 distributing the secondary fluid in the collectors 18, and an outlet chamber 24 collecting the secondary fluid at the outlet of the collectors 20; lower internal equipment 26 channeling the primary fluid between the collectors 14 and 16, on the one hand, and the inlet 4 and the outlet 6 of the primary fluid, on the other hand; and

a fan 28 for circulating the primary fluid fixed on the chamber 2. The chamber 2 comprises a tank 30 inside which the exchangers 12 and the collectors 14, 16, 18, 20, presenting upwards, are arranged. an opening 32, and a cover 34 for sealing the opening 32 of the tank 30. The tank 30 comprises a cylindrical top ferrule 36, coaxial with the X axis, a cylindrical lower ferrule 38, coaxial with the X axis, disposed under the upper ferrule 36, of slightly reduced diameter with respect to the ferrule 36, a frustoconical ferrule 40 interposed between the ferrules 36 and 38, and a bottom curved bottom 42, closing the ferrule 38 downwards.

The upper free edge of the ferrule 36 surrounds the opening 32 and forms a flange 44.

The lid 34 is curved upwards, and has a free edge forming a flange 46 complementary to the flange 44 of the tank 30. The lid 34 has an upper bottom section substantially in elliptical portion in a plane containing the X axis.

As can be seen in FIG. 11, the lid 34 is capable of being rigidly fixed to the tank 30 by means of eighty tie rods 50 engaged in holes 52 formed on the flange 46, and screwed into orifices. these threads 54 formed on the flange 44. The flange 46 carries a high seal metal seal 55, for example of the type sold under the trade name "HELICOFLEX", sealing between the lid 34 and the tank 30 when they are fixed to each other.

The inputs 8 of the secondary fluid are provided at the bottom of the ferrule 36, on the same circumference thereof. They are arranged all four on the same half of the shell 36, as shown in Figure 4.

These inputs are circular, and have axes arranged at 42 ° from each other.

The outputs of the secondary fluid 10 are provided at the top of the upper vi- rector 36, and are arranged on the same circumference of this ferrule (Figure 3). They are located on the same half of the shell 36 as the inputs 8. As for the inputs, these outlets 10 are circular and their axes are spaced 42 °.

The lower shell 38 comprises a single stitching through which are formed the inlet 4 and the outlet 6 of the primary fluid. The input 4 and the output 6 are coaxial, as shown in FIG. 2, the output 6 surrounding the input 4.

The bottom 42 is curved downwards, and has a central, round opening, centered on the X axis, in which the fan 28 is fixed. As can be seen in FIG. 5, the eight heat exchangers 12 are arranged in a circle about the X axis, and regularly distributed around it.

The exchangers 12 are plate type heat exchangers. Each exchanger 12 comprises eight modules 56 stacked vertically, identical to each other.

As shown in Figure 7, each module 56 has a parallelepiped shape. Each module 56 comprises an outer casing 58 in which are machined inlet and outlet ports 60 and 62 of the primary fluid and inlet and outlet ports 64 and 66 of the secondary fluid, and a plurality of plates 67 arranged at inside the casing 58, stacked axially.

The lights 60 and 62 are arranged on two opposite faces of the envelope 58, turned respectively inwardly and outwardly of the assembly 1. The lights 64 and 66 are formed on two substantially radial and opposite sides. of the envelope 58 (FIGS. 6A to 6C).

The stacked plates 67 define between them a plurality of primary fluid flow channels extending radially from the lumen 60 to the lumen 62.

The plates 67 also define between them a plurality of secondary fluid circulation channels, extending substantially circumferentially, from the lumen 64 to the lumen 66. It will be appreciated that the lumen 64 is radially outwardly displaced by relative to the light 66, so that the secondary fluid circulates Z in the module 56, as shown in Figure 6B. The circulation channels of the primary and secondary fluids are superimposed alternately in the module 56, so as to improve the efficiency of the heat exchange between the fluids.

The radial circulation channels of the primary fluid do not open along the two radial faces of the module 56, so that the secondary fluid can not penetrate these channels through the slots 64 and

66. Similarly, the substantially circumferential circulation channels of the secondary fluid do not open along the inner and outer faces. module 56 so that the primary fluid can not enter these channels through the lumens 60 and 62.

As shown in FIG. 7, the parallelepipedal modules 56 have machined angles over the entire axial height of the exchanger 12. This exchanger 12 also comprises forged and machined metal bars 68 arranged in the machined angles of the modules 56. bars 68 extend over the entire axial height of the exchanger 12. The modules 56 are welded to each other by their respective envelopes 58, and are also welded to the metal bars 68. The bars 68 comprise a main portion 70 of section perpendicular to the X axis, disposed in the machined portions of the modules 56, and a flange 72 projecting circumferentially with respect to the modules 56.

The main portion 70 is welded to the modules 56 along two axial weld lines 74 and 76, visible in Figures 7, 8A and 8B. The line 74 extends along radial faces of the modules 56, and the line 76 extends along the inner faces or along the outer faces of the modules 56, depending on the case.

It will be noted that axial empty channels 78 are machined in the modules 56 and in the bars 68, behind the weld lines 74 and 76, and over the entire length thereof. The presence of these empty channels 78 makes it possible to carry out quality control of the welds 74 and 76 by ultrasound.

It will be noted that the wings 72 are connected to the radial faces of the modules 56 according to a predetermined radius of curvature R, calculated so as to reduce the stresses in the bars 68.

The modules 56 are also welded to one another along the weld lines 79. These weld lines 79 follow the edges delimiting the radial, inner and outer faces of the modules 56, downwards and upwards.

The assembly 1 comprises four axial inlet manifolds 18 communicating with the inlet 8 of the secondary fluid via the inlet chamber 22, and four axial output channels 20 communicating with each other. with the outlet 10 of the secondary fluid via the outlet chamber 24.

The collectors 18 and 20 are circumferentially interposed between the exchangers 12, as shown in FIG. 5. The axial inlet and outlet manifolds 18 are distributed alternately around the central axis X, so that successively, rotating about the central axis X ₁ an exchanger 12, an axial inlet manifold 18, an exchanger 12, an axial outlet manifold 20, an exchanger 12, an axial inlet manifold 18, etc. . The axial collectors 18 and 20 each have a section perpendicular to the axis X in ring sector, delimited inwards and outwards by circumferential plates respectively 80 and 82, and on the sides by the radial faces of the exchangers 12 between which extends said collector. The inner and outer plates 80 and 82 of an axial collector 18 or

20 are welded edge to edge on the wings 72 of the bars 68 of the two adjacent exchangers 12 of the collector. The shape of the wings 72 is determined such that these wings are in the continuity of the inner or outer plates 80 or 82 (Figures 8A and 8B). The modules 56 are oriented such that the input window 64 opens into an axial input channel 18, and the output window 66 opens into an axial output channel 20.

The assembly 1 further comprises a central collector 14 extending along the axis X and communicating with the inlet 4 of the primary fluid, and an annular channel 16 communicating with the outlet 6 of the primary fluid.

The central collector 14 extends radially inside the exchangers 12 and is delimited by the inner faces of the modules 56 and the inner plates 80. It has substantially a circular section perpendicular to the axis X. The windows 60 open into the central collector 14.

The annular collector 16 extends around the exchangers 12, radially outwardly with respect thereto. It is bounded inwards by the outer plates 82 and the outer faces of the modules 56. The windows 62 open into the annular collector 16.

The inlet and outlet chambers 22 and 24 of the secondary fluid are respectively located under the exchangers 12 and above these exchangers 12 (FIGS. 1 and 2).

The central collector 14 is axially extended downwards by an intermediate cylindrical section 84 arranged under the exchangers 12. Similarly, the annular collector 16 is extended axially downwardly by an intermediate annular section 86 surrounding the intermediate cylindrical section 84.

The inlet chamber 22 has an annular shape and is located axially at the inputs 8 of the secondary fluid. It surrounds the intermediate cylindrical section 84 and extends radially inside the intermediate annular section 86. The inlet chamber 22 is delimited radially outwards by a cylindrical wall 85.

Furthermore, the assembly 1 comprises a visiting channel 88 extending the collector 14 axially upwards beyond the exchangers 12. This channel 88 is isolated from the central collector 14 by a removable door 90. It is also closed to the top by another detachable inspection hatch 92.

The outlet chamber 24 also has an annular shape and surrounds the visit channel 88.

The axial inlet channels 18 are open downwards and communicate with the inlet chamber 22. They are closed upwards and isolated from the outlet chamber 24. Conversely, the axial outlet channels 20 are closed downwards. and isolated from the inlet chamber 22, and are open upwards and communicate with the outlet chamber 24.

The annular collector 16 is closed upwards and does not communicate with the outlet chamber 24. According to another important aspect of the invention, the heat exchangers 12, the inlet and outlet chambers 22 and the collectors 14 , 16, 18 and 20 are assembled in a mechanical subassembly 94 extrac- This subassembly is shown in FIG. 9.

The subassembly 94 has a generally cylindrical shape, of axis X. The subassembly 94 is delimited upwards by a plane circular plate 96, radially outwardly by a cylindrical envelope 98, and downwardly by a frustoconical casing 100 extending the cylindrical casing 98 downwards and converging therefrom. The upper plate 96 defines the outlet chamber 24 upwards (Figures 1 and 2). The survey channel 88 extends upwardly projecting above the plate 96 and forms a grasping head 102 of the subassembly 94. The trap 92 is located at the top plate 96.

The subassembly 94 further comprises an engagement ring 104 surrounding the upper plate 96 (FIG. 9), projecting radially outwards with respect to the envelope 98. This ring 96 forms a bearing surface downwards. 106. The flange 44 comprises, on a radially internal side, a complementary bearing surface 108, on which the bearing surface 106 rests when the subassembly 94 is disposed inside the vessel 30.

The subassembly 94 further comprises four stiffeners 108 extending radially from the mushroom 102 to the crown 104.

The outer casing 98 delimits radially outwardly the outlet chamber 24 and the annular collector 16, in particular the intermediate section 86 of this collector. It is pierced with four circular holes 110 in the upper part and four circular holes 112 in the lower part, arranged in the extension respectively of the outputs 10 of the secondary fluid and the inputs 8 of the secondary fluid when the subassembly 94 is disposed in the enclosure 2.

The subassembly 94 also comprises a horizontal annular floor 114 (FIGS. 1 and 2) delimiting the inlet chamber 22 downwards and extending between the respective sections 84 and 86 of the central and annular collectors 14 and 16. Furthermore, the central collector 14 extends under the section 84 by a lower cylindrical section 116 of X axis, ending downwardly with a free edge 118 (Figure 2).

The frustoconical envelope 100 surrounds the lower section 116, and ends downwards by a cylindrical rim 120, of axis X. The annular section 86 of the annular collector 16 opens downwards between the lower section 116 and the frustoconical envelope 100.

FIG. 1 shows that the subassembly 94 comprises a stiffening collar 122, perforated to allow the circulation of the primary fluid, arranged around the lower section 116. This lower collar 122 is welded up on the floor 114 and below on the frustoconical shell 100. Radial stiffeners 124 are welded to both the floor 114 on the frustoconical shell 100 and the lower shell 122, and increase the stiffness of the subassembly 94 in the lower part. An outer cylindrical shell 126 (FIG. 12) is welded under the frustoconical shell 100. It extends close to the frustoconical shell 40 of the tank 30. This outer shell is reinforced by six radial stiffeners 128 welded on both sides. the frustoconical shell 100 and the outer shell 126. These stiffeners 128 carry three keys 130, shown in Figure 12, cooperating with axial grooves 132 formed on the shell 40 of the tank 30. The keys 130 and grooves 132 are arranged at 120 ° from each other about the X axis and make it possible to index the subassembly 94 in rotation about the X axis.

The outlet chamber 24 is sealingly connected to the outlets 10 of the second fluid by external 140 and internal 142 cuffs, visible in FIG. 10A. The outer sleeve 140 is screwed onto an annular piece 144 welded into the outlet 10. It has a tubular shape and extends from the outlet 10 inwards, so that it is engaged in the hole 110 of the outer casing 98. The fixing screws 146 are accessible from the inside of the outlet chamber 24.

The hole 110 is surrounded by an edge 148 raised towards the inside of the outlet chamber 24 from the casing 98. The internal cuff 142 has a tubular shape and is interposed between the outer sleeve 140 and the erected edge 148. It is fixed by screws 150 on the free end of the erected edge 148.

High-sealing metal seals of known type, sold under the trade name "HELICOFLEX", are interposed between the outer sleeve 140 and the crown piece 144, on the one hand, and between the inner sleeve 142 and the upright edge 148, on the other hand.

In addition, a tubular bellows 154 connects the sleeves 140 and 142 to one another in a sealed manner. The sleeves 140 and 142 are free to slide relative to each other in a direction radial to the X axis, the seal being maintained by the bellows 144.

Insulation blocks 156 isolate the bellows 154 and the screws 146 of the secondary fluid flowing from the outlet chamber 24 to the outlet 10. The inlet chamber 22 is sealingly connected to the inlets 8 by external sleeves 158 and internal 160 similar to the outer and inner sleeves 140 and 142 described above (Figure 10B). Note, however, that the erected edge 148 extends, in this case, from the outer casing 98 beyond the cylindrical wall 85 to the inside of the inlet chamber 22. The cylindrical wall 85 is welded on the erected edge 148. The erected edge 148 thus ensures a sealed passage from the inlet chamber 22 through the annular intermediate portion 86 of the collector 16, to the outer casing 98. Furthermore, note that the outer and inner cuffs 158 and 160 and the bellows 154 are not heat insulated due to the moderate temperature of the secondary gas at the inlet of the assembly 1. The inspection channel 88 includes a wide opening (163) which provides access to the disconnection systems of the outlet chamber 24. The intermediate portion 84 of the manifold 14 comprises a visit hole 164 communicating with the inlet chamber 22 (Figure 2). This manhole 164 is closed sealingly by a removable hatch. A manhole (not shown) provided with a removable hatch makes it possible to access the annular channel 16 from one of the axial outlet channels 20.

The lower internals 26 include coaxial X-axis lower input 170 and output 172 collectors communicating with each other. respectively with the inlet 4 and the outlet 6 of the primary fluid (Figure 2). The lower outlet manifold 172 surrounds the lower inlet manifold 170. The lower inlet manifold 172 is connected to the inlet 4 by a radial pipe 174, which passes through the lower outlet manifold 172. The manifold 172 is welded with sealed manner around the piping 174.

The lower inlet manifolds 170 and outlet 172 end one and the other upwards by flanges 176 capable of sealingly receiving the free edge 118 of the central collector 14 and the flange 120 of the frustoconical envelope 100 by simple interlocking. The flanges 176 have inward frustoconical bearing surfaces guiding the free edge 118 and the flange 120. Moreover, the latter carry outwardly metal seals providing a sealed contact with the inner face of the flanges 176.

The lower outlet manifold 172 is closed downward by a bottom 178 perpendicular to the X axis. The lower inlet manifold 170 comprises a cylindrical shell 180 of X axis extending to the bottom 178 and a bottom 182. perpendicular to the X axis closing the ferrule 180 at an intermediate level between the pipe 174 and the bottom 178.

The bottom 178 is pierced by a central opening 184 receiving the suction of the fan 28. Furthermore, the shell 180 has passage openings 186 under the bottom 182, thus creating a path for the primary fluid since the lower outlet manifold 172 through the openings 186 to the volume between the funds 178 and 182 and in the suction of the fan 28. In addition, the lower internal equipment 26 further comprises a frustoconical ferrule 188 converging upwards, including the large base is welded to the lower shell 38 of the tank 30 and whose small base is welded around the lower outlet manifold 172. The frustoconical shell 188 has passage openings 190. These openings connect the volume located under the lower inlet and outlet manifolds 170 and 172 with the volume located around these same lower manifolds. The outlet 6 of the primary fluid opens directly into the volume located around the lower collectors 170 and 172.

The fan 28 discharges the primary fluid through radial openings inside the curved lower bottom 42, the primary fluid being able to flow from there through the openings 190 upwards, and then through the outlet 6. .

Finally, the tank 30 comprises three support blocks 194, integrated and welded into the lower shell 38. The blocks 194 are arranged at 120 ° from each other about the X axis. As shown in FIG. 1 rests, through the blocks 194, on concrete masses 196 projecting from the walls of the cell 197 in which is disposed the assembly 1.

Flying buttresses 198, interposed between the walls of the cell and the upper ferrule 36 of the tank 30, stabilize the assembly 1 in the vertical position.

The hottest parts of the assembly 1 are insulated, for example by blocks comprising I ₂ O ₃ fibers or carbon fibers. These parts operate at temperatures close to or exceeding 800 ^° C. in nominal operation. These are the pipework 174, the lower inlet manifold 170, the central manifold 14, including its intermediate sections 84 and lower 116, the axial outlet manifolds 20, the outlet chamber 24, and the cuffs 140. and 142 connecting the outlet chamber 24 to the outlets 10 of the secondary fluid.

The enclosure 2 has a total height of about 27 m, and a diameter of about 7 m. The cylindrical envelope 98 has a diameter of about 6300 mm.

Each exchanger 12 has an axial height of about 4800 mm, a radial depth of about 1300 mm, and a circumferential width of about 560 mm. Each module 56 has a height of about 600 mm.

The diameter of the central collector 14 is about 2800 mm. It is determined so that the inner sheets 80 delimiting the axial collectors 18 and 20 have a circumferential developed length and a sufficient flexibility to recover the deformations imposed in a plane perpendicular to the X axis by the exchangers 12.

The radial depth of the annular collector 16 is about 500 mm. It is determined so that an operator can slip inside the annular collector 16, so as to perform checks and / or repairs on the outer face of the exchangers 12.

The secondary fluid inlets 8 have passage diameters of 850 mm minimum and the outputs 10 of the secondary fluid have passage diameters of 1 m minimum. The assembly 1 is dimensioned for example for a pressure of about 50 bars of the primary fluid, a flow rate of about 200 kg / s of the primary fluid, a flow rate of about 600 kg / s of the secondary fluid, and a difference of pressure between the primary and secondary fluids of about 5 bar in normal operation. We will now describe the circulation paths of the primary and secondary fluids through the assembly 1 (see Figure 1).

The primary fluid enters the assembly 1 through the inlet 4, passes into the pipe 174, into the lower inlet manifold 170 and into the central manifold 14. It is distributed from this central manifold 14 to the various exchangers 12 distributed around the central collector, which it passes radially to the annular collector 16, yielding part of its heat to the secondary fluid. The primary fluid then flows down the annular collector 16, its lower section 86, passes through the apertures of the perforated ferrule 122, then flows around the lower section 116 of the central collector 14, and then enters the lower collector 170 and the lower collector 172. The primary fluid then passes through the openings 186 of the collar 180, is sucked by the fan 28 and discharged radially down the tank 30. It then passes through the openings 190 of the ferrule frustoconical 188 and out of the assembly 1 by the outlet 6 formed around the inlet 4.

The secondary fluid enters the assembly 1 through the inlets 8, flows through the cuffs 158 and 160 to the inlet chamber 22, and is distributed, from the inlet chamber 22, in the different col- axial input readers 18. The secondary fluid passes through the exchangers 12 circumferentially and is collected in the axial outlet manifolds 20. It follows the collectors 20 axially to the outlet chamber 24, and is then distributed from the chamber 24 in the different outlets 10. The maintenance procedures of the set 1 will now be described.

In the event of a minor intervention to be performed on the exchangers 12, for example blocking a circulation channel of the primary fluid or the secondary fluid, an operator intervenes directly on the exchangers 12, these remaining in place inside the pregnant 2.

For this purpose, the lid 34 of the external enclosure 2 is first removed. Then the operator opens the hatch 92 and gains the inspection channel 88. If the repair is to be carried out on one side of a 12-way exchanger to an axial outlet channel 20, the operator passes through the opening 163 (Figure 2), enters the outlet chamber 24, and descends into the appropriate axial outlet manifold from the chamber 24.

If the repair is to be performed on an outer face of an exchanger 12, the operator enters the annular manifold 16 from the chamber 24, via the axial outlet channel 20 having a manhole, and performs the repair to from the collector 16.

If the intervention is to be performed on an inner face of an exchanger 12, the operator opens the hatch 90 and passes from the inspection channel 88 to the central collector 14. It performs the repair from the central collector 14.

If the intervention is to be carried out on one side of an exchanger 12 facing an axial input manifold 18, the operator descends along the central manifold 14, to the intermediate section 84, opens the hatch 164, enters the inlet chamber 22, and goes back into the appropriate axial inlet manifold 18 from the chamber 22.

If a major repair is to be performed on the exchangers 12, for example replacing a module 56, the subassembly 94 must first be removed from the tank 30. For this purpose, a maintenance cell 200 (FIG.

13) is provided above the cell 197 in which is located the whole

1. The two cells communicate via an opening 202 closed by a mobile isolation trap 203 arranged above the assembly 1.

First, a sealing ring 204 is placed around the upper part of the assembly 1. Seals ensure the seal between the ring 204 and the flange 44 of the tank 30, on the one hand, and between the ring 204 and the peripheral edge of the flap 202. A vinyl sock 206 is disposed above the sealing ring 204, and is suspended from the lifter of the bridge 201 of the cell 200.

The cover 34 of the enclosure 2 is first removed by means of the bridge 201. The enclosure 2 is then isolated from the maintenance cell 200 by putting in place the trap 203 during the evacuation of the cover 34. replacement of the vinyl sleeve 206 and opening of the hatch 203, the operators enter the outlet chamber 24 through the hatch 92 and the opening 163. They remove the insulation blocks 156 protecting the hinges 140 and 142 then dismantle the screws 146 and 150 using suitable tools. Once the cuffs 140 and 142 have been released, the operators pull these cuffs (with specific tools) inside the outlet chamber 24. They thus proceed for the four secondary fluid outlets 10.

The operators then gain the inlet chamber 22 through the hatches 90 and 164. They release the cuffs 158 and 160 connecting the secondary fluid inlets 8 to the inlet chamber 22, and pull these cuffs (with specific tools) inside the room. They then leave the assembly 1. The crane of the bridge 201 then mates with the mushroom 102 of the subassembly 94. This subassembly is then lifted by raising the rudder of the bridge 201, out of the tank 30 and lifted through the hatch 202 to the cell 200. It is then inside the vinyl sock 206, isolation of the enclosure 1 by closing the hatch of 202. The overhead crane then moves inside of the maintenance cell 200, to come and deposit the subassembly 94 in a suitable receiving stool. The heavy maintenance operations are performed in this cell 200. The replacement of subassembly 94 inside the tank 30 is done according to a procedure exactly opposite to that just described above.

The subassembly 94 must be guided in rotation about the X axis when it is put back in place, so that the indexing keys 130 engage in the appropriate grooves 132.

Once the span 106 of the flange 104 rests on the complementary bearing surface 108 of the tank 30, the crossbar of the bridge 201 is uncoupled from the pickup head 102. The maintenance cell 200 may be common to several sets 1, serving the same nuclear reactor, or serving several different nuclear reactors.

The set described above has many advantages. The axial manifolds 18 and 20 open into the inlet and outlet chambers 22 and 24 and are not mechanically connected directly to the inputs and outputs 8 and 10 of the secondary fluid. This configuration is favorable vis-à-vis the differential expansions between the outlets 8 and 10 connected to the tank and the chambers 22 and 24 belonging to the subset of the exchanger 94 thus significantly limiting the thermomechanical stresses of these links.

The arrangement of the exchangers 12 and the axial inlet and outlet manifolds 18 and 20 makes it possible to give these collectors 18 and 20 a large passage section. The axial circulation velocity of the secondary fluid along these collectors is for example between 10 and 20 m / s. In other exchanger concepts, these speeds reached 60 m / s. These reduced speeds are favorable for maintaining a hydraulic balance between the inputs and the outputs 64 and 66 of the secondary fluid of each module 56, in normal operation. These reduced speeds also allow a distribution of the uniform secondary fluid to the different modules 56 stacked along the same axial collector 18, and are favorable, from a thermo-hydraulic point of view, in transient operation. The overall efficiency of the exchangers 12 is improved. The thermomechanical behavior of the collectors is also particularly favorable. The axial collectors 18 and 20 are delimited by inner circumferential plates 80 and outer 82 flexible, easily deformed under the effect of the constraints imposed by the exchangers 12. The exchangers 12 are in fact high rigidity blocks compared to the plates 80 and 82, which impose their deformation to these sheets. The sheets 80 and 82 are thin shells, large radii of curvature, which gives them great flexibility.

The entry and exit chambers 22 and 24 are large in size and not internally partitioned. As a result, the inlet chamber allows a distribution of the uniform secondary fluid in the different axial inlet manifolds 18. Moreover, because of their large passage sections, these chambers offer little resistance to the circulation of the secondary fluid. . They also make it easy to access the inputs 8 and the outputs 10, and thus to easily and quickly disconnect the cuffs 140, 142, 158 and 160 of the inputs 8 and the outputs 10.

Finally, the fact that the chambers are devoid of internal partitioning makes it possible to arrange the inlets 8 and the outlets 10 on one and the same side of the enclosure 2. It is thus possible to arrange the assembly 1 close to a wall of the cell 97, the inlet and outlet pipes of the secondary fluid extending all opposite the wall.

The subassembly 94, which contains all the exchangers as well as the main collectors for the circulation of the primary and secondary fluids, can be withdrawn in one piece from the outer enclosure 2. This operation is carried out particularly simple and convenient, using the bridge of the maintenance cell located above the heat exchanger assembly 1, after evacuation of the cover 34 and retraction of the sleeves 40 and 42 inside the chambers of input 22 and output 24. The retraction of cuffs 40 and 42 is achieved using tools adapted quickly and easily, so that the doses integrated by the operators are low. Once the cuffs 140 and 142 disassembled, the extraction of the subset 94 and reintroduction into the chamber 2 is by simple disengagement and interlocking.

The lower manifolds 170 and 172 have flanges 176 of a shape adapted to guide the lower portion of the subassembly 94 when it is put back in place. The sealed connection of the central collector 14 and the annular collector 16 with the lower collectors 170 and 172 is by simple interlocking in a vertical direction.

The heavy maintenance operations on the exchangers 12 are conveniently carried out in a special maintenance cell equipped with the appropriate equipment.

Moreover, small repairs can be performed on the exchangers 12 in situ, that is to say without removing the subassembly 94 of the enclosure 2. The central collector, the annular collector and the axial inlet collectors and output have sections of sufficiently large sizes for an operator to enter and work. The exchangers 12 are accessible on their four faces for repair.

The modules 56 constituting each exchanger 12 are welded to each other along the edges delimiting, upwards and downwards, the inner, outer and radial faces of these modules. The fillet welds are eliminated because of the presence of the bars 68 arranged in the machined angles of the modules 56.

The inner and outer circumferential plates 80 and 82 are welded to the flanges 72 of the bars 68. This weld is located at a distance from the modules 56 and can be conveniently controlled by radiography.

The critical zone C (see FIGS. 9A and 9B) in which the thermomechanical stresses are maximum is situated at the junction between the wing 72 and the main part 70 of the bar 68, and therefore extends into the mass of the bar 68. and not at the level of the weld. Finally, the wing 72 is connected to the radial faces of the modules 56 by a radius of curvature (R) optimized according to the thermomechanical stresses in the critical zone C. These different constructive arrangements make it possible to make the exchangers 12 particularly resistant to thermomechanical stresses.

The heat exchange assembly described above can have multiple variants.

Thus, for example, the exchangers 12 may not be plate type, but for example be heat exchangers tube and calender.

The fan 28 may not be arranged on the bottom of the tank 30, but rather be fixed to the cover 34. It is in this case necessary to modify the circulation of the primary fluid leaving the heat exchangers 12. The annular collector 16 is extended upwardly to the fan 28 and is partitioned to define an upward portion channeling the primary fluid to the blower 28 and a downward portion channeling the primary fluid from the blower 28 to the outlet 6.

The evacuation of the subassembly 94 is more complex in this case, since it is necessary to disassemble the fan 28 before removing the cover 34 from the enclosure 2.

The heat exchange assembly may comprise more or fewer than eight heat exchangers 12.

The secondary fluid inlets 8 may be disposed at the top of the upper shell 36, the secondary fluid outlets 10 being, in this case, disposed below the heat exchangers 12.

The primary fluid can flow from the inlet 4 to the heat exchangers 12 in the annular manifold 16, and return from the exchangers to the outlet 6 through the central manifold.

The primary fluid can flow from the inlet chamber 22 through the axial channels 18 and 20 to the outlet chamber 24, the secondary fluid circulating, in this case, in the central collector 14 and in the annular collector 16.

The primary fluid may not be substantially pure helium, but may be a mixture of helium and nitrogen. The primary fluid may also comprise mainly water. The secondary fluid may be substantially pure helium or a mixture of helium and nitrogen (for example 20% helium and 80% nitrogen or 40% helium and 60% nitrogen). The secondary fluid may also be mainly water, and vaporized in the heat exchange assembly. In this case, the heat exchange assembly acts as a steam generator.

It should be noted that the heat exchange assembly 1 described above has several original aspects that can be protected independently of one another. Thus, it is possible to provide that the assembly 1 comprises a mechanical subassembly extractable in one piece such as 94, while the axial manifolds 18 and 20 are connected to the inputs 8 and 10 outlets by connecting pipes and not by means of chambers such as 22 and 24. In this case, the terminal parts of the connecting pipes are capable of being disassembled manually inputs and outputs 8 and 10, for example from the free space between the cover 34 and the exchangers 12, and from the free space between the frustoconical casing 100 and the exchangers 12. These end parts are retracted inside the connection pipes, or completely separated from them and outputs manually from the enclosure 2 by the operators.

Similarly, it is possible to provide that the assembly 1 comprises exchangers 12 provided with bars 68 such as those described above while the axial collectors 18 and 20 are not connected to the inputs 8 and outputs 10 by chambers 22 and 24 and / or that the assembly 1 does not include a removable subassembly 94.

Claims

1. Heat exchange assembly (1) between a first and a second fluid, the assembly comprising:

an outer enclosure (2) having a central axis (X) and provided with at least one inlet (4) and an outlet (6) of the first fluid and at least one inlet (8) and an outlet (10) the second fluid,

a central collector (14) extending along the central axis (X) and communicating with one of the inlet (4) and the outlet (6) of the first fluid,

- an annular collector (16) disposed around the central collector (14) and communicating with the other of the inlet (4) and the outlet (6) of the first fluid,

a plurality of heat exchangers (12) distributed around the central axis (X) and radially interposed between the central collector (14) and the annular collector (16); a plurality of axial input collectors (18); ) communicating with the inlet (8) of the second fluid, and a plurality of axial outlet manifolds (20) communicating with the outlet (10) of the second fluid, the axial inlet and outlet manifolds (18, 20) being circumferentially interposed between the exchangers (12), - each exchanger (12) comprising a plurality of channels of circulation of the first fluid between the central (14) and annular (16) collectors, and a plurality of circulation channels of the second fluid since from at least one inlet manifold (18) to at least one outlet manifold (20), characterized in that it comprises an inlet chamber (22) provided on a first axial side of the exchangers (12), communicating the inlet (s) (8) of the second fluid with a at least several axial inlet manifolds (18).

2. An assembly according to claim 1, characterized in that the inlet chamber (22) has an annular shape and surrounds the central manifold (14).

3. An assembly according to claim 1 or 2, characterized in that it comprises an outlet chamber (24) provided with a second axial side of the exchangers (12) opposite to the first, placing in communication the outlets (10) of the second fluid with at least a plurality of axial outlet collectors (20).

4. The assembly of claim 3, characterized in that it comprises a visit channel (88) extending the central collector (14) axially second side and isolated therefrom by a removable door (92), the outlet chamber (24) having an annular shape and surrounding the inspection channel (88).

5. An assembly according to claim 4, characterized in that at least the exchangers (12), the inlet (22) and outlet (24) chambers, and the axial inlet (18) and outlet (20) are assembled in a mechanical subassembly (94) extractable in one piece from the enclosure (2).

6. An assembly according to claim 5, characterized in that the enclosure (2) is of vertical central axis, the enclosure (2) comprising a vessel (30) inside which is disposed the subassembly ( 94) and presenting upwardly an opening (32) for extracting said subassembly (94), and a cover (34) for sealing the opening (32) of the vessel (30).

7. The assembly of claim 6, characterized in that the vessel (30) comprises a cylindrical shell (36) coaxial with the central axis in which are formed the inlet (8) and outlet (10) of the second fluid, the chambers inlet (22) and outlet (24) being sealingly connected to the inlet (8) and outlet (10) of the second fluid by collapsible sleeves (140, 142, 158, 160) retractable within the rooms (22, 24).

8. The assembly of claim 7, characterized in that the sleeves (140, 142, 158, 160) are removable from the inside of the chambers (22, 24).

9. An assembly according to any one of claims 7 to 8, characterized in that the enclosure (2) comprises a plurality of inlets (8) and several outlets (10) of the second fluid, these inlets (8) and these outlets. (10) being gathered on the same circumferential half of the ferrule (36).

10. An assembly according to any one of claims 6 to 9, characterized in that the subassembly (94) comprises an outer shell (98) cylindrical coaxial with the central axis (X) ₁ delimiting radially outwardly the outlet chamber (24) and the annular manifold (16).

11. The assembly of claim 10, characterized in that it comprises lower inlet manifolds (170) and coaxial output (172) communicating respectively with the inlet (4) and the outlet (6) of the first fluid and arranged under the subassembly (94), the latter being delimited in the lower part by a frustoconical envelope (100) converging from the cylindrical envelope (98), this frustoconical envelope (100) surrounding the central collector (14) and defining therewith the annular manifold (16), the lower manifolds (170, 172) ending upwardly with flanges (176) capable of sealingly receiving the lower free ends of the central manifold (14) and the frustoconical envelope (100) by simple interlocking.

12. Assembly according to any one of claims 4 to 11, characterized in that the central collector (14) has a manhole (164) closed by a removable door, communicating with the inlet chamber (22) and the The inspection channel (88) has an opening (163) communicating with the outlet chamber (24).

13. Assembly according to any one of the preceding claims, characterized in that the enclosure (2) has a lower bottom (42), and in that the assembly (1) comprises a circulation member (28) fixed to the bottom bottom (42) adapted to suck the first fluid out of the annular channel (16) or the central channel (14) and to discharge to the outlet (6) of the first fluid.

An assembly according to any one of the preceding claims, characterized in that the axial inlet (18) and outlet (20) collectors, the central collector (14) and the annular collector (16) have passage sections. sufficient to allow an operator to intervene directly on the exchangers (22).

15. An assembly according to any one of the preceding claims, characterized in that the inlet (4) and the outlet (6) of the first fluid are coaxial.

16. An assembly according to any one of the preceding claims, characterized in that the exchangers (12) are arranged regularly spaced in a circle around the central axis (X), each axial collector (18, 20) being delimited towards the inner and outer circumferential sheets (80) and outer (82) welded to the two heat exchangers (12) between which said manifold extends.

17. The assembly of claim 16, characterized in that the annular collector (16) is delimited inwardly by the exchangers (12) and the outer plates (82).

18. An assembly according to claim 16 or 17, characterized in that the central collector (14) is delimited by the exchangers (12) and the inner plates (80).

19. An assembly according to any one of claims 16 to 18, characterized in that each heat exchanger (12) comprises a plurality of axially stacked heat exchange modules (56).

20. An assembly according to any one of claims 16 to 19, characterized in that the modules (56) have a rectangular cross section perpendicular to the central axis (X) and have machined angles over the entire axial height of the exchanger (12), the latter further comprising forged and / or machined metal bars (68) disposed in the machined corners and on which the modules (56) are welded.

21. The assembly of claim 20, characterized in that the bars (68) each have a flange (72) projecting circumferentially relative to the modules (56) to the adjacent axial collector (18, 20), on which is welded the inner sheet (80) or outer (82) defining said axial collector.

22. Use of the assembly according to any one of the preceding claims with a first fluid mainly comprising helium and a second fluid mainly comprising helium and / or nitrogen.

23. Use of the assembly according to any one of claims 1 to 21 with a first fluid mainly comprising helium and a second fluid mainly comprising water, the second fluid being vaporized in the exchanger assembly.

24. Use of the assembly according to any one of claims 1 to 21 with first and second fluids mainly comprising water, the second fluid being vaporized in the exchanger assembly.

25. Use according to any one of claims 22 to 24, characterized in that one of the first or the second fluid is from a nuclear reactor.