FR3092379A1 - Tube assembly process in a nuclear power plant - Google Patents

Abstract

Method for mounting tubes in a nuclear power station The method comprises the following steps: - obtaining a fitting (1) comprising a tubular body (3) internally defining a longitudinal passage (5) for the circulation of fluid and having first and second longitudinal ends (7, 9), and permanent fixings (11, 13) provided to fix in a non-removable manner the first and second longitudinal ends (7, 9) to the tubes; - fixing of a first tube (15, 51, 63) at the first longitudinal end (7); - fixing of a second tube (17, 53, 57) at the second longitudinal end (9), the first tube (15, 51, 63) being in fluid communication with the second tube (17, 53, 57) through the longitudinal passage (5) of the tubular body (3) of the connector (1). Figure for abstract: figure 6

Description

Method of mounting tubes in a nuclear power plant

The invention generally relates to the assembly of tubes in a nuclear power station.

The tubes in a nuclear power plant are generally connected to each other by welds. Such a connection method has many drawbacks.

The companies intervening to carry out such operations must be qualified to intervene in nuclear installations.

Welders must possess professional diplomas, which are periodically renewed. The welding procedures must also be qualified, so that the welding operations are expensive.

It is difficult in some cases to find enough qualified welders to carry out the operations within the required time.

Welding is typically carried out using orbital TIG machines, which are expensive to maintain.

The time required to make a weld, and the destructive and non-destructive testing to guarantee the quality of this weld, is important.

Welding tools are bulky, and in some cases accessibility to the area where the welding is to be carried out cannot be guaranteed.

Gammametric checks, carried out by radio shots, are long, and are generally on the critical path of maintenance operations.

When the welding operation is carried out in an ionizing environment, on installations already in service, the time required to carry out the welding operation and the checks impacts the dose integrated by the intervention personnel.

In this context, the invention aims to provide a method for mounting tubes in a nuclear power plant which does not have the above defects.

To this end, the invention relates to a method for mounting tubes in a nuclear power plant, the method comprising the following steps:

- Obtaining a connector comprising a tubular body internally defining a longitudinal fluid circulation passage and having first and second longitudinal ends, and permanent fasteners provided for fixing the first and second longitudinal ends to the tubes in a non-removable manner;
- Fixing a first tube to the first longitudinal end in a non-removable manner with one of the permanent fixings;
- Attachment of a second tube to the second longitudinal end in a non-removable manner with the other permanent attachment, the first tube being in fluid communication with the second tube through the longitudinal passage of the tubular body of the fitting.

The use of fittings with permanent attachments to the tubes allows the assembly of the tubes to be considerably speeded up. The fact that the fixings are permanent ensures a high level of quality in the fixings. This level of quality is much higher than that obtained with removable fittings.

The fitting can be put in place with a space-saving tool.

The assembly process may also have one or more of the characteristics below, considered individually or in all technically possible combinations:

- the steps of fixing the first and/or second tubes to the first and/or second longitudinal ends of the body are carried out cold;

- The permanent fasteners secure the first and/or second longitudinal ends of the body to the first and/or second tubes by crimping;

- the first and second longitudinal ends are configured to receive internally, before crimping, the first and second tubes, the permanent fixings comprising rings mounted around the first and second longitudinal ends, the step of fixing the first or second tube to the first or second longitudinal end comprising the following sub-steps:
- Engagement of the first or second tube in the first or second longitudinal end;
- Displacement of the ring longitudinally along the first or second longitudinal end towards a central part of the body located longitudinally between the first and second ends, this displacement causing the crimping of the first or second tube at the first or second longitudinal end;

- in the displacement sub-step, the ring is moved longitudinally to a stop, the step of fixing the first or second tube to the first or second longitudinal end comprising a sub-step of dimensional control of displacement during which the longitudinal spacing between the ring and the stop is checked with a shim of thickness less than 5/100 mm;

- in the engagement sub-step, the first or second tube is engaged in the first or second longitudinal end longitudinally up to an internal stop and after displacement of the ring, the step of fixing the first or second tube to the first or second longitudinal end comprising a dimensional engagement control sub-step comprising the following operations:
- before engagement of the first or second tube in the first or second longitudinal end, creation of a visual cue on the first or second tube
- After engagement of the first or second tube in the first or second longitudinal end to the internal stop, measurement of the longitudinal distance between the ring and the visual marker;

- the method comprises a step of fixing a first tube to a structure of a nuclear reactor, the second tube being already fixed to the structure of the nuclear reactor at the time of the step of fixing the first tube to the structure of the reactor nuclear, the method comprising a step of elastic deformation of the second tube during which a free end of the second tube is moved away from a location provided for the connection after assembly, carried out before the step of fixing the second tube to the second end fitting body;

- the method comprises a step of fixing a first tube to a structure of a nuclear reactor, the second tube being already fixed to the structure of the nuclear reactor at the time of the step of fixing the first tube to the structure of the reactor nuclear, the method comprising a step of moving the second tube during which a free end of the second tube is moved away from a location provided for the connector after assembly, carried out before the step of fixing the second tube to the second end of the fitting body;

- the step of moving the second tube includes the following sub-steps:

- disassembly of an accessory to which the second tube is connected opposite the first tube;
- Displacement of the second tube in the direction of a spacing of the free end relative to said location provided for the connection once mounted.

Other characteristics and advantages of the invention will emerge from the detailed description given below, by way of indication and in no way limiting, with reference to the appended figures, among which:

[Fig 2] Figures 1 and 2 show the construction of the connector used in the method of the invention, respectively before fixing the tubes and after fixing the tubes;

[Fig 4] Figures 3 and 4 illustrate dimensional checks which are carried out in the invention to guarantee the quality of the connection of the tubes;

[Fig 6] [Fig 7] Figures 5 to 7 show different stages of the assembly method of the invention, in a case where the method is applied to the replacement of a weld of an already existing conduit;

[Fig 9] [Fig 10] Figures 8 to 10 illustrate different steps of the method of the invention, in the case of mounting a pipe section between two fixed points, for a first embodiment of the invention;

[Fig 12] [Fig 13] [Fig 14] Figures 11 to 14 illustrate, like Figures 8 to 10, different steps of the method of the invention, applied to the assembly of a pipe section between two fixed points, for another alternative embodiment of the invention.

The method of the invention relates to the assembly of tubes in a nuclear power station.

These tubes are typically of moderate section. They generally have an outside diameter between 6 and 25 mm for metric tubes, and between ¼ inch and one inch for imperial tubes.

These tubes are metal tubes, typically steel.

These tubes are part of all kinds of circuits. They are designed for the circulation of liquid or gas, radioactive or non-radioactive fluids.

They are integrated for example in utility supply circuits, in sampling circuits, in measurement circuits, or in any other type of circuit.

The process is applied to already existing circuits, during maintenance operations. In this case, it aims for example to replace a defective weld with a fitting. The tubes connected by the connector are the original tubes, and are not replaced.

Alternatively, the method aims to replace a portion of the existing piping. The original tubes are removed, and are replaced by new tubes, which are connected to each other by the fittings which will be described below.

The process of the invention is also aimed at the assembly of new tubes, during the creation of the piping in new works.

In all cases, the method for mounting tubes of the invention comprises the following steps:

- Obtaining a connector 1 comprising a tubular body 3 internally defining a longitudinal passage 5 for the circulation of fluid and having first and second longitudinal ends 7, 9, and permanent fasteners 11, 13 provided for non-removably fastening the first and second longitudinal ends 7, 9 to the tubes (Figure 1);

- Fixing a first tube 15 to the first longitudinal end 7 in a non-removable manner with one of the permanent fasteners 11, 13 (Figure 2);

- attachment of a second tube 17 to the second longitudinal end 9, in a non-removable manner, with the other permanent attachment 11, 13, the first tube 15 then being in fluid communication with the second tube 17 through the longitudinal passage 5 of the tubular body 3 of the fitting 1 (FIG. 2).

Advantageously, the steps of fixing the first and/or second tubes 15, 17 to the first and/or second longitudinal ends 7, 9 of the body 3 are carried out cold.

In other words, no thermal process is used to connect the first and second longitudinal ends to the first and second tubes. The fixing is exclusively mechanical.

Preferably, the permanent fixings 11, 13 fix the first and/or second longitudinal ends 7, 9 of the body 3 to the first and/or second tubes 15, 17 by crimping.

Crimping is a mechanical operation consisting of fixing two parts to each other by deforming said parts.

As illustrated in Figures 1 and 2, the first and second longitudinal ends 7, 9 are configured to receive internally, before crimping, the first and second tubes 15, 17.

The body 3 comprises a central part 19, located longitudinally between the first and second ends 7, 9, and connecting the first and second ends 7, 9 to each other (figure 1).

The longitudinal passage 5 extends over the entire length of the body 3.

It crosses the first and second longitudinal ends 7, 9 and the central part 19.

This passage 5 has at the first and second ends 7, 9 first and second sections 21, 23.

These first and second sections 21, 23, before crimping, have an internal section slightly larger than the external section of the first and second tubes 15, 17.

The first and second sections 21, 23 are connected to each other by an intermediate section 25 of the passage 5, of smaller internal section than the first and second sections 21, 23. First and second shoulders 27, 29 are thus provided between the intermediate section 25 and respectively the first and second sections 21, 23.

These shoulders 27, 29 constitute abutments for the first and second tubes 15, 17.

The internal surface of the first and second ends 7, 9 carries reliefs 31, allowing the crimping of the first and second ends 7, 9 on the first and second tubes 15, 17.

These reliefs are of any suitable type. In the example shown, these are circumferential ribs.

The permanent fasteners 11, 13 each include a ring 33. The rings 33 are mounted around the first and second longitudinal ends 7, 9.

Each ring 33 internally delimits an internal passage 35 of decreasing section. The internal section of the passage 35 decreases longitudinally, from one end of the ring 33 facing the central part 19 of the body, towards the end of the ring 33 facing away from the central part 19.

The step of fixing the first or second tube 15, 17 to the first or second longitudinal end 7, 9 then comprises the following steps:

- Engagement of the first or second tube 15, 17 in the first or second longitudinal end 7, 9;

- displacement of the ring 33 longitudinally along the first or second longitudinal end 7, 9 towards the central part 19 of the body 3.

This displacement causes the crimping of the first or second tube 15, 17 with the first or second longitudinal end 7, 9.

At the engagement sub-step, the first or second tube 15, 17 is engaged in the first or second longitudinal end 7, 9 longitudinally up to an internal stop.

This internal stop here corresponds to the first or second shoulder 27, 29.

Due to the convergent shape of the internal passage of the ring 33, the longitudinal displacement of the ring 33 causes the crushing of the first or second end 7, 9 on the first or second tube 15, 17. The internal surface of the ring 33 comes to bear on the outer surface of the first or second end 7, 9, forcing the first or second end 7, 9 to deform.

As a result, the internal reliefs 31 of the first and second ends 7, 9 sink into the outer surface of the first or second tube 15, 17. Conversely, the material constituting the first or second tubes 15, 17 fills the hollows between the reliefs 31.

At the displacement sub-step, each ring 33 is moved longitudinally as far as an abutment 37. Typically, this abutment is provided on the central part 19 of the body. The central part thus comprises two stops 37, one for each of the two rings 33.

The state of the connection at the end of the fixing steps is illustrated in FIG. 2. The rings 33 are in abutment against the stops 37. The first and second longitudinal ends 7, 9 of the body 3 are crimped with the first and second tubes 15, 17. The reliefs 31 have penetrated the outer surface of the first and second tubes 15, 17. The material constituting the tubes has filled the spaces between the reliefs 31.

The first and second tubes 15, 17 are thus firmly held in abutment against the shoulders 27, 29.

Typically, the displacement of the rings 33 is carried out using a hydraulic press, equipped with inserts adapted to the shape of the rings and the tubes.

Advantageously, the step of fixing the first or second tube 15, 17 to the first or second longitudinal end 7, 9 includes a sub-step of dimensional control of the movement of the ring 33.

During this sub-step, the longitudinal spacing between the ring 33 and the corresponding stop 37 is checked with a shim with a thickness of less than 5/100 of a mm, preferably less than 3/100 of a mm and equal to example 2/100 mm.

This wedge is shown in Figure 4.

The dimensional control sub-step is carried out by an operator, who tries to slide the wedge 39 between the stop 37 and the corresponding ring 33. If the operator manages to slip the shim between the ring and the stop, it is considered that the movement of the ring has not been complete and that the fixing is not satisfactory.

On the contrary, if the wedge cannot be slid between the ring 33 and the abutment 37, then it is considered that the longitudinal displacement of the ring has been complete and that the test is satisfactory.

Preferably, the fixing step also includes a sub-step of dimensional control of engagement of the first or second tube 15, 17.

As illustrated in Figures 3 and 4, this sub-step includes the following operations:

- before engagement of the first or second tube 15, 17 in the first or second longitudinal end 7, 9, creation of a visual cue 41 on the first or second tube 15, 17;

- after engagement of the first or second tube 15, 17 in the first or second longitudinal end 7, 9 up to the internal stop and after displacement of the ring 33, measurement of the longitudinal distance between the ring 33 and the visual marker 41 .

Preferably, a second visual cue 43 is also created for the first or second tube 15, 17, before engagement of this tube in the corresponding longitudinal end (FIG. 3).

The visual marker 43 is interposed longitudinally between the visual marker 41 and the free end of the first or second tube 15, 17 inserted into the body 3.

For example, the visual marker 41 is a circular mark, extending over the entire periphery of the first or second tube 15, 17. The visual marker 43 is preferably of the same type.

Typically, when the tube 15, 17 is engaged in the first or second longitudinal end 7, 9, and before displacement of the ring 33, the two marks 41, 43 must be invisible. This ensures that the tube is engaged up to the stop 27, 29.

After displacement of the ring 33, the visual cue 41 is visible. This situation is illustrated in Figure 4.

On the other hand, the visual cue 43 must not be visible.

The non-visibility of the visual marker 43 is a first qualitative check, making it possible to ensure that the tube 15, 17 has remained in abutment during the movement of the ring 33.

The longitudinal distance between the ring 33 and the visual marker 41 is measured using a wedge 45, shown in Figure 7. The wedge 45 is placed against the ring 33. More specifically, it is placed against the end of the ring 33 located opposite the central part 19 of the body.

The visual cue 41 must be masked by the wedge 45 for the control to be positive. This guarantees that the movement of the ring 33 has been complete, and that the tube 15, 17 has remained in abutment during the movement of the ring 33. If the visual marker 41 is visible, it is considered that the control is negative, and that the fixing of the tube is not satisfactory.

The longitudinal positions of the visual markers 41 and 43 are chosen according to the dimensions of the tubular body 3 and the rings 33.

The attachment to the first tube 15 at the first end 7, or the attachment to the second tube 17 at the second end 9 has been described above. The first and second tubes 15, 17 can both be attached as described above.

A first example of implementation of the mounting method of the invention will now be described, with reference to Figures 5 to 7.

This implementation typically corresponds to a case of intervention on existing piping 47 of the nuclear power plant. It aims to replace, for example, a defective weld 49 with the connection 1 described above.

The method then includes a preliminary step of cutting the pipe 47, at the level of the weld 49 to be eliminated. For example, a cut is made on each side of the weld 49, the weld 49 then being evacuated.

The cut is for example made using a pipe cutter, so as to ensure a good surface finish on the free ends of the remaining tubes 51, 53.

The free ends of the remaining tubes 51, 53, located on either side of the weld 49 which has been eliminated, are then deburred, using a “pencil sharpener” type tool.

We then visually check the cleanliness and the absence of scratches on the ends of the remaining tubes.

The visual marks 41, and preferably the visual marks 43, are then made on the tubes 51, 53.

The connector 1 is then placed between the tubes 51 and 53, the tube 51 being engaged in the first longitudinal end 7 of the connector and the tube 53 in the second longitudinal end 9 of the connector.

As illustrated in Figure 6, at this stage, the rings 33 are located at a distance from the central part 19 of the body 3. The tubes 51 and 53 are in abutment against the stops 27, 29.

It is checked at this stage that none of the visual markers 41, 43 is visible.

The tube 51 is then fixed to the first longitudinal end 7, and the tube 53 to the second longitudinal end 9.

This operation is performed by moving the longitudinal rings 33 towards the central part 19 of the body.

This movement ends when the rings 33 come into abutment against the stops 37.

The dimensional displacement and engagement checks are then carried out, as described above.

A second example of implementation of the invention will now be described, with reference to Figures 8 to 10.

This example corresponds to a case where a portion of existing piping is replaced by new piping. The various tubes constituting the new piping are connected to each other using connectors 1 of the type described above.

The pipe portion is mounted between two fixed points 55, 57.

This example of implementation also applies to new works, when installing a section of piping between two fixed points.

The fixed point 55 is for example an isolation valve, or an existing connection, or even a portion of piping already installed.

In the example shown in the figures, the fixed point 57 is a tube.

The method then includes a step of fixing an initial tube 59 to the structure 60 of the reactor. The tube 59 is also connected to the first fixed point 55.

Then, one or more other intermediate tubes 61 are possibly fixed to the structure 60.

The intermediate tubes 61 are connected to the initial tube 59, and are connected together by connectors 1 of the type described above.

The structure 60 of the reactor is typically a civil engineering structure, a floor, a wall or any other structure.

The assembly of the last tube 63 poses a particular problem, because it must be connected by connectors 1 of the above type, between a tube 59 or 61 already in place and the tube 57 which is a fixed point. The final connection to tube 57 is particularly delicate if there is not a degree of freedom between the last tube 63 and tube 57.

In other words, there is a particular difficulty due to the fact that the method comprises a step of fixing the tube 63 (first tube) to the structure 60 of the nuclear reactor, whereas the tube 57 (second tube) is already fixed to the structure 60 of the nuclear reactor at the time of attachment of the tube 63 to the structure 60 of the nuclear reactor.

In this case, the method advantageously comprises a step of moving the second tube 57, during which a free end 65 of the second tube 57 is moved away from a location provided for the connector 1 after assembly.

This step is carried out before the step of fixing the second tube 57 to the second end 9 of the connector 1.

More specifically, as shown in Figure 9, the second tube 57 is elastically deformed so as to separate the free end 65 from the location of the future connection. If necessary, attachments of the tube 57 to the structure 60 of the reactor are dismantled to allow the elastic deformation of the second tube 57.

The step of fixing the first tube 63 to the structure 60 of the nuclear reactor is carried out after the deformation step, as illustrated in figure 10.

Finally, the connector 1 is placed between the first tube 63 and the second tube 57, and the tubes 63 and 57 are engaged in the first and second ends 7, 9 of the body 3 of the connector 1. The fixing of the tubes 63 and 57 to fitting 1. This is achieved by moving the rings 33, as described above.

The dimensional displacement and engagement checks are then carried out as described above.

A third example of implementation of the method of the invention will now be described, with reference to Figures 11 to 14.

As in FIGS. 8 to 10, this example corresponds to a case of assembly of a pipe section between two fixed points 55, 57.

The new piping replaces an already existing piping, during a maintenance operation. As a variant, the new piping is put in place during new works, during the creation of the piping.

As before, the second fixed point 57 is a tube (the second tube). The method includes a step of fixing an initial tube 59 to the structure 60 of the reactor, the tube 59 also being connected to the first fixed point 55.

As before, the method optionally comprises a step of fixing one or more intermediate tubes 61 to the structure 60, and connecting the intermediate tube(s) 61 to each other and to the initial tube 59 by fittings 1 of the type described above. .

As before, the assembly of the last tube 63 (the first tube), intended to be connected to the second tube 57 poses a particular problem because the first tube 63 must be inserted between the previous tube 59 or 61, already existing, and the second tube 57, which constitutes a fixed point.

In other words, the method comprises a step of fixing the first tube 63 to the structure 60, while the second tube 57 is itself already fixed to said structure 60 at the time of the step of fixing the first tube 63 .

In this case, the method advantageously includes a step of moving the second tube 57 during which the free end 65 of the second tube 57 is moved away from the location provided for the connector 1 after assembly.

This operation is carried out before the step of fixing the second tube 57 to the second end 9 of the body 3 of the connector 1.

To do this, the step of moving the second tube 57 comprises the following sub-steps:

- disassembly of an accessory 67 to which the second tube 57 is connected opposite the tube 63;

- displacement of the second tube 57 in the direction of a spacing of the free end 65 with respect to said location provided for the connector 1 once mounted.

The dismantling of the accessory 67 is illustrated in figure 12. The accessory 67 corresponds for example to an isolation valve, or to another fitting or to any other suitable removable component. Removing the accessory 67 creates a space to move the second tube 57, as shown in figure 12.

It becomes possible, after removing the accessory 67 and moving the second tube 57, to fix the first tube 63 to the structure of the reactor 60, and to connect the first tube 63 to the previous tube, which is the intermediate tube 61 in the example shown, by a connector 1 of the type described above.

This situation is illustrated in Figure 13.

It also becomes possible to arrange a connector 1 of the type described above between the first tube 63 and the second tube 57 offset on the side of the accessory 67.

The fixing of the first tube 63 to the first end 7 of the body 3 and the fixing of the second tube 63 to the second end 9 of the body 3 then takes place.

As described above, this is done by moving the rings 33 longitudinally up to the stops 37.

The dimensional displacement and engagement checks are then carried out, as described above.

The invention has been described with a connector comprising two ends, designed to receive and fix two tubes. It can be implemented with a connector comprising more than two ends intended to receive a tube, for example three ends (T connector) or four ends (cross connectors).

The invention has been described with crimp fasteners. In a non-preferred variant, another type of permanent attachment is used.

Claims (9)

A method of mounting tubes in a nuclear power plant, the method comprising the following steps:
- obtaining a connector (1) comprising a tubular body (3) internally defining a longitudinal fluid circulation passage (5) and having first and second longitudinal ends (7, 9), and permanent fasteners (11, 13 ) provided for fixing in a non-removable manner the first and second longitudinal ends (7, 9) to the tubes;
- Fixing a first tube (15, 51, 63) to the first longitudinal end (7) in a non-removable manner with one of the permanent fasteners (11, 13);
- attachment of a second tube (17, 53, 57) to the second longitudinal end (9) in a non-removable manner with the other permanent attachment (11, 13), the first tube (15, 51, 63) being in fluid communication with the second tube (17, 53, 57) through the longitudinal passage (5) of the tubular body (3) of the fitting (1). Assembly method according to claim 1, in which the steps of fixing the first and/or second tubes (15, 51, 63; 17, 53, 57) to the first and/or second longitudinal ends (7, 9) of the body ( 3) are carried out cold. Mounting method according to Claim 1 or 2, in which the permanent fixings (11, 13) fix the first and/or second longitudinal ends (7, 9) of the body (31) to the first and/or second tubes (15, 51 , 63; 17, 53, 57) by crimping. Assembly method according to claim 3, in which the first and second longitudinal ends (7, 9) are configured to receive internally, before crimping, the first and second tubes (15, 51, 63; 17, 53, 57), the permanent fixtures comprising rings (33) fitted around the first and second longitudinal ends (7, 9), the step of securing the first or second tube (15, 51, 63; 17, 53, 57) to the first or second longitudinal end (7, 9) comprising the following sub-steps:
- engagement of the first or second tube (15, 51, 63; 17, 53, 57) in the first or second longitudinal end (7, 9);
- displacement of the ring (33) longitudinally along the first or second longitudinal end (7, 9) towards a central part (19) of the body (3) located longitudinally between the first and second ends (7, 9), this movement causing crimping of the first or second tube (15, 51, 63; 17, 53, 57) at the first or second longitudinal end (7, 9). Mounting method according to Claim 4, in which, in the moving sub-step, the ring (33) is moved longitudinally to an abutment (37), the step of fixing the first or second tube (15, 51 , 63; 17, 53, 57) at the first or second longitudinal end (7, 9) comprising a dimensional displacement control sub-step during which the longitudinal spacing between the ring (33) and the abutment (37 ) is checked with a wedge (39) less than 5/100 mm thick. A mounting method according to claim 4 or 5, wherein, in the engagement sub-step, the first or second tube (15, 51, 63; 17, 53, 57) is engaged in the first or second longitudinal end ( 7, 9) longitudinally up to an internal stop (27, 29), the step of fixing the first or second tube (15, 51, 63; 17, 53, 57) to the first or second longitudinal end (7, 9) comprising a dimensional engagement control sub-step comprising the following operations:
- before engagement of the first or second tube (15, 51, 63; 17, 53, 57) in the first or second longitudinal end (7, 9), creation of a visual marker (41) on the first or second tube (15 , 51, 63; 17, 53, 57)
- after engagement of the first or second tube (15, 51, 63; 17, 53, 57) in the first or second longitudinal end (7, 9) as far as the internal stop (27, 29), and after displacement of the ring (33), measurement of the longitudinal distance between the ring (33) and the visual marker (41). Mounting method according to any one of claims 1 to 6, in which the method comprises a step of attaching a first tube (51) to a structure (60) of a nuclear reactor, the second tube (57) being already fixed to the structure (60) of the nuclear reactor at the time of the step of fixing the first tube (51) to the structure (60) of the nuclear reactor, the method comprising a step of elastic deformation of the second tube (57) at the during which a free end (65) of the second tube (57) is separated from a location provided for the connector (1) after assembly, carried out before the step of fixing the second tube (57) to the second end (9 ) of the body (3) of the fitting (1). Mounting method according to any one of claims 1 to 6, in which the method comprises a step of attaching a first tube (63) to a structure (60) of a nuclear reactor, the second tube (57) being already fixed to the structure (60) of the nuclear reactor at the time of the step of fixing the first tube (63) to the structure (60) of the nuclear reactor, the method comprising a step of moving the second tube (57) during from which a free end (65) of the second tube (57) is separated from a location provided for the connector (1) after assembly, carried out before the step of fixing the second tube (57) to the second end (9) of the body (3) of the fitting (1). A mounting method according to claim 8, wherein the step of moving the second tube (57) comprises the following substeps:
- disassembly of an accessory (67) to which the second tube (57) is connected opposite the first tube (63);
- Displacement of the second tube (57) in the direction of a spacing of the free end (65) relative to said location provided for the connector (1) once mounted.