A device for holding two elements together, particularly in a compact nuclear reactor.

Abstract

A device for retaining two elements attached one to the other, particularly in a compact nuclear reactor. The retaining device (10) comprises a fixing screw (16), including a screw head (16a) and a screw body (16b), and a threaded portion (18) for receiving the screw body (16b), the threaded portion (18) being integral with the first element (12), and a tubular retaining sleeve (24), including a central passage (26) for the screw (16). The retaining sleeve (24) has at least one portion (32) projecting radially outwards, intended to be inserted into a recess (34) formed in the second element (14). The retaining sleeve (24) has, at a proximal end, a portion (36) deformable between a screw (16) passage configuration and a screw head (16a) retention configuration. Figure for the abbreviation: Figure 2

Description

Title of the invention: Device for holding two elements attached to each other, in particular in a compact nuclear reactor

[0001] The present invention relates to a device for holding two elements attached to one another, in particular in a compact nuclear reactor.

[0002] Such a holding device is for example intended for holding a flow separation shell on a steam generator tube plate in a compact nuclear reactor, allowing the shell and the tube plate to be handled together during their assembly or disassembly in the compact nuclear reactor.

[0003] In such a compact nuclear reactor, in particular of type K, water from a primary circuit is heated in the vessel of a nuclear reactor, containing the nuclear fuel rods and circulates in pipes passing into a steam generator receiving the water from the secondary circuit in order to allow a heat exchange between the water circulating in the primary circuit and the water from the secondary circuit. At the end of this exchange, the water from the primary circuit cooled in the pipes returns to the vessel where it is heated again. In a known manner, the part of the primary circuit containing the hot water is called the hot leg and the part of the primary circuit containing the cold water is called the cold leg. At the level of the passage from the vessel to the steam generator, it is known to separate the hot leg from the cold leg in a sealed manner by a flow separation shell.

[0004] The flow separation shell is fixed to the tube plate of the steam generator, by fixing means known per se. A holding device is provided to hold the flow separation shell on the tube plate without handling the assembly during assembly or disassembly. Such a holding device comprises screws.

[0005] The present invention aims to propose a holding device preventing the screw heads from falling in the event of their breaking, in order to avoid the presence of a migrating body in the primary circuit. In the context where the holding device is dedicated to holding the flow separation shell relative to the tube plate of the steam generator, it must be able to be dismantled during maintenance, with the constraints that this implies in terms of accessibility and radiation protection.

[0006] To this end, the invention relates to a device for holding a first element with a second element, comprising at least one fixing screw, comprising a screw head and a screw body, and, for each fixing screw:

[0007] - a threaded part for receiving the screw body, the threaded part being integral with the first element,

[0008] - a holding sleeve, of generally tubular shape, comprising a passage central for the screw, the central passage being delimited by an inner wall, the inner wall comprising a radially inwardly projecting annular part intended to be clamped longitudinally between the screw head and the threaded part,

[0009] characterized in that:

[0010] - the holding sleeve comprises at least one radially projecting part towards the exterior, intended to be inserted into a housing provided in the second element,

[0011] - the holding sleeve comprises, at a proximal end, a deformable part between a screw passage configuration, and a screw head holding configuration.

[0012] In the event of the screw head breaking, the latter would remain held by the retaining sleeve, in particular by its deformable part, the retaining sleeve remaining held to the second element by the part projecting radially outwards.

[0013] According to other advantageous aspects of the invention, the fixing device comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

[0014] - The tapped part is formed by a pin integral with the first element.

[0015] - The pin is welded to the first element, preferably in a receiving cavity of this pawn.

[0016] - The second element comprises a through opening opposite the part threaded, the through opening being delimited by an internal wall of general shape of revolution around a longitudinal axis, the internal wall comprising an annular shoulder, arranged, in the longitudinal direction, between the pin and the screw head, and the socket also comprising a facing said annular shoulder.

[0017] - The protruding part is formed by a foldable tab.

[0018] - The receiving housing of the radially projecting part is delimited on the one hand by the second element and on the other hand by the first element.

[0019] - The deformable part is formed by a thin part of the socket.

[0020] The invention also relates to a nuclear reactor comprising a plate and a flow separation shell, characterized in that it comprises a holding device as defined above, in which the first element is formed by the plate and the second element is formed by the flow separation shell.

[0021] The invention finally relates to a method of mounting a holding device as defined above, characterized in that it comprises the following steps:

[0022] - arrangement of the socket in an opening of the second element,

[0023] - arrangement of the radial part in the housing,

[0024] - arrangement of the second element on the first element by placing each opening opposite the corresponding tapped part,

[0025] - inserting the screw by screwing it into the tapped hole, and

[0026] - deformation of the deformable part towards its configuration for holding the head of screw.

[0027] The invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0028] [Fig-1] [Fig. 1] is an axial sectional view of a compact nuclear reactor comprising a holding device according to an exemplary embodiment of the invention;

[0029] [Fig.2] [Fig.2] is an axial sectional view of said holding device.

[0030] [Fig. 2] shows a device 10 for holding a first element 12 with a second element 14, according to an exemplary embodiment of the invention.

[0031] For example, the invention is implemented in a compact nuclear reactor.

[0032] Such a compact nuclear reactor is for example part of a nuclear propulsion system, intended for example to equip a submarine. It is however understood that the holding device 10 can be used in other applications requiring the holding of a screw head in the event of the latter breaking.

[0033] Conventionally, the nuclear reactor 100 mainly comprises a vessel 102, containing nuclear fuel rods 104 and water from a primary circuit set in motion by a pump 106 and compressed by a compressor 108, and a steam generator 110 containing water from a secondary circuit injected into the steam generator 110 by a cold water inlet 112 and leaving the steam generator 110 in the form of steam by an outlet 114 to supply, for example, a turbine of a propulsion system.

[0034] The water of the secondary circuit is heated by the water of the primary circuit by heat exchange between the water of the secondary circuit contained in the steam generator 110 and the hot water of the primary circuit circulating in bundles of pipes 116 extending in the steam generator 110, the water of the primary circuit passing from the tank 102 to the bundles of pipes 116, after having been heated by the nuclear fuel rods 104, through a separation plate separating the tank 102 from the steam generator 110.

[0035] The arrows C of [Fig. 1] represent the path of the hot water of the primary circuit. The water of the primary circuit cooled after the heat exchange returns to the tank 102 due to the shape of the pipes of the bundles of pipes 116 as represented by the arrows F of [Fig.l], representing the path of the cold water in the primary circuit. In the tank 102, the cold water, designated by the expression cold leg, is separated from the hot water, designated by the expression hot leg, by a wall 120 surrounding the fuel rods 104. At the separation plate, the nuclear reactor 100 comprises a flow separation shell surmounting the wall 120 and ensuring a seal between the hot leg and the cold leg to prevent water from the hot leg from entering the cold leg.

[0036] In the context of the present invention, the separation plate forms said first element 12, and the flow separation ferrule forms said second element 14.

[0037] The holding device 10 comprises at least one fixing screw 16, and preferably a plurality of fixing screws 16, only one of which is shown in [Fig. 2]. The holding device 10 is identical with respect to the other fixing screws.

[0038] Each fixing screw 16 extends in a longitudinal direction.

[0039] Each fixing screw 16 conventionally comprises a screw head 16a and a screw body 16b extending in the longitudinal direction. The screw head 16a is shaped to cooperate with a suitable screwing tool, and the screw body 16b is threaded.

[0040] Preferably, the screw head 16a has a chamfer 15.

[0041] The first element 12 comprises a threaded portion 18, integral with this first element 12, and complementary to the screw body 16b so that the screw body 16b is capable of being screwed into the threaded portion 18. The threaded portion 18 is preferably formed by a pin welded to the first element 12 and pierced with a threaded orifice. The threaded orifice is defined around a longitudinal axis X parallel to the longitudinal direction. The pin preferably has a general shape of revolution around the longitudinal axis X.

[0042] The second element 14 comprises a through opening 17 opposite the tapped part 18, extending parallel to the longitudinal direction X. The through opening 17 is delimited by an internal wall 17a of general shape of revolution around the longitudinal axis X. The internal wall 17a comprises an annular shoulder 17b, arranged, in the longitudinal direction, between the pin 18 and the screw head 16a.

[0043] Advantageously, the first element 12 comprises a cavity 19 for receiving the pin 18, in which the pin 18 is fitted before welding.

[0044] Said pin 18 extends longitudinally between a distal end 20 welded to the first element 12, and a proximal end 22 at which the threaded orifice opens.

[0045] The fixing device 10 further comprises a holding sleeve 24 of generally tubular shape, comprising a central passage 26 for the screw.

[0046] The central passage 26 is delimited by an inner wall 28. The inner wall 28 comprises an annular portion 30 projecting radially inwards. The annular portion 30 is arranged between the pin 18 and the screw head 16a, so as to be clamped between them when tightening the screw 16 in the pin 18.

[0047] The holding sleeve 24 comprises at least one part 32 projecting radially outwards, intended to be inserted into a housing 34 formed in the second element 14. In the embodiment described, said housing 34 is formed by a recess in the second element 14 on the one hand, and by a wall of the first element 12 on the other hand. The projecting part 32 is preferably formed at a distal end of the holding sleeve 24.

[0048] The projecting portion 32 is preferably formed by a foldable tab.

[0049] The holding sleeve 24 has an outer wall 35, of diameter very slightly smaller than that of the inner wall 17a in a distal part between the shoulder 17b and the first element 12, so as to allow the insertion of the holding sleeve 24 into the opening 17, while allowing the smallest possible transverse movement, or even almost zero. This almost zero transverse movement allows in particular centering of the sleeve 24 relative to the opening 17.

[0050] The outer wall 35 also comprises a shoulder 35a, intended to be arranged opposite the shoulder 17b.

[0051] The holding sleeve 24 comprises, at a proximal end, a portion 36 deformable between a configuration for passing the screw 16, and a configuration for holding the screw head 16a. The deformable portion 36 is for example formed by a thin portion of the sleeve 24. The portion 36 is deformable by means of a tool provided for this purpose, for example a tightening tool making it possible to tighten the deformable portion 36 onto the screw head 16a. More particularly, the portion 36 is deformed against the chamfer 15 of the screw head 16a.

[0052] Alternatively, the deformable portion could be formed by a plurality of deformable tabs.

[0053] The method of mounting the holding device 10 will now be described.

[0054] Firstly, the pin 18 is placed in the cavity 19 of the first element 12, before being welded there.

[0055] Furthermore, the sleeve 24 is arranged in the opening 17, from a proximal end of the opening 17 towards a distal end. The insertion of the sleeve 24 is limited by the shoulders 17b and 35a facing each other.

[0056] During a following step, each radial part 32 is put in place, for example by radially folding the tab(s) forming the radial part(s) 32. The radial part thus extends into the housing 34.

[0057] It should be noted that at this stage, the sleeve 34 is held in the opening 17, towards the proximal end by the radial part 32 and towards the distal end by the shoulder 35a.

[0058] The second element 14 can therefore be handled without risk of the socket 34 falling.

[0059] The second element 14 is then attached to the first element 12, by placing each opening 17 opposite each corresponding pin 18. The second element 14 is put in place ensuring that the pin 18 fits into the socket 24. Thus, the socket 24 surrounds the pin 18.

[0060] The screw 16 is then inserted through the opening 17 to be screwed into the threaded hole of the pin 18. The screwing is carried out until the annular part 30 is clamped between the pin 18 and the screw head 16a. The screwing is carried out using a conventional screwing tool, through the opening 17.

[0061] Once screwed, the screw 16 allows, with the other screws, a holding of the first 12 and second 14 elements between them. More particularly, when the first element 12 moves away from the second element 14, the shoulder 17b comes into contact with the shoulder 35a, this shoulder 35a being connected to the screw 16 by means of the sleeve 24. The first 12 and second 14 elements cannot therefore move further apart than the clearance between the shoulders 17b and 35a.

[0062] It will be noted that the transverse forces pass from the second element 14 to the first element 12 through the sleeve 24 and the pin 18. The holding device 10 therefore makes it possible to transversely hold the assembly of the first 12 and second 14 elements. It should be noted that the forces do not pass through the screw, although the latter is not subjected to much stress, which limits the risks of the screw head breaking.

[0063] Finally, the method comprises tightening the deformable part 36 onto the screw head 16a.

[0064] In the event of the screw head 16a breaking, it remains held by the deformable part 36 of the sleeve 24. This sleeve 24 then remains held in the opening 17 by the radially projecting part 32.

[0065] It will be noted that the disassembly of the holding device 10 is easy, by simply providing for the loosening of the deformable part 36.

Claims

Claims

1. Device (10) for holding a first element (12) with a second element (14), comprising at least one fixing screw (16), comprising a screw head (16a) and a screw body (16b), and, for each fixing screw (16): - a threaded portion (18) for receiving the screw body (16b), the threaded portion (18) being integral with the first element (12), - a holding sleeve (24), of generally tubular shape, comprising a central passage (26) for the screw (16), the central passage (26) being delimited by an inner wall (28), the inner wall (28) comprising an annular portion (30) projecting radially inwards intended to be clamped longitudinally between the screw head (16a) and the threaded portion (18), characterized in that: - the holding sleeve (24) comprises at least one radially projecting portion (32) outwards, intended to be inserted into a housing (34) provided in the second element (14),- the holding sleeve (24) comprises, at a proximal end, a part (36) deformable between a configuration for passing the screw (16), and a configuration for holding the screw head (16a).,

2. Holding device (10) according to claim 1, in which the threaded part (18) is formed by a pin integral with the first element (12).

3. Holding device (10) according to claim 2, in which the pin is welded to the first element (12), preferably in a cavity (19) for receiving this pin.

4. Holding device (10) according to any one of the preceding claims, in which the second element (14) comprises a through opening (17) opposite the threaded part (18), the through opening (17) being delimited by an internal wall (17a) of general shape of revolution around a longitudinal axis (X), the internal wall (17a) comprising an annular shoulder (17b), arranged, in the longitudinal direction, between the pin (18) and the screw head (16a), and the sleeve (24) also comprising a (35a) opposite said annular shoulder (17b).

5. A holding device (10) according to any preceding claim, wherein the projecting portion (32) is formed by a foldable tab.

6. Holding device (10) according to any one of the preceding claims, in which the housing (34) for receiving the radially projecting part (32) is delimited on the one hand by the second element (14) and on the other hand by the first element (12).

7. A holding device (10) according to any preceding claim, wherein the deformable portion (36) is formed by a thin portion of the sleeve (24).

8. Nuclear reactor (100) comprising a plate (12) and a flow separation shell (14), characterized in that it comprises a holding device (10) according to any one of the preceding claims, in which the first element is formed by the plate (12) and the second element is formed by the flow separation shell (14).

9. Method for mounting a holding device (10) according to any one of claims 1 to 7, characterized in that it comprises the following steps: - arrangement of the sleeve (24) in an opening (17) of the second element (14), - arrangement of the radial part (32) in the housing (34), - arrangement of the second element (14) on the first element (12) by placing each opening (17) opposite the corresponding threaded part (18), - insertion of the screw (16) by screwing it into the threaded orifice (18), and - deformation of the deformable part (36) towards its configuration for holding the screw head (16a).

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