FR3015759A1 - METHOD AND DEVICE FOR CLEANING A BEAM OF BARS OR TUBES - Google Patents

Abstract

The invention relates to a method for cleaning a bundle of bars or tubes immersed in a liquid, in which: - a cleaning liquid is projected towards the bundle by causing the jet of the cleaning liquid to rotate, and so that the envelope formed by the rotating jet diverges; a stream of gas is formed which surrounds at least a portion of the jet of cleaning liquid; and - a relative displacement of the rotating jet of liquid and the surrounding gas flow with respect to the beam is caused.

Description

TECHNICAL FIELD The present invention relates to a method of cleaning a bundle of bars or tubes, in particular a method of cleaning an assembly of rods or rods. nuclear fuel needles, and a device for cleaning a bundle of bars or tubes such as an assembly of rods or nuclear fuel needles. STATE OF THE ART The invention applies in particular to the cleaning of bars or tubes - generally designated by the terms of rods or needles - containing a material forming the nuclear fuel, which are assembled (e) s by organs of mechanical assembly to form assemblies - or bundles - and which are immersed in a basin filled with water, called swimming pool. The pool may be a pool in a nuclear reactor or an assembly storage facility. In the present application, the term pencil is used to designate indifferently the pencil or the needle containing the material forming the nuclear fuel. The assembly comprises the rods and a structure for holding these rods, which notably comprises holding grids. The invention is particularly applicable to the cleaning of an assembly of rods in a reactor pool, or in a pool for storing assemblies. The assemblies of fuel rods stored in the water may be the seat of algae or slime deposit, in particular, on the surface of the rods 25 and / or assembly parts of these rods. Before loading the assemblies in the core of a reactor, a cleaning of these assemblies may be necessary to keep clean the heat exchange surfaces of the fuel rods and the mechanical holding structure of the rods. For this, it is necessary to detach the impurities present, for example by deposition or adhesion, on these surfaces and structure, without having to extract the assemblies of the pool. 3 0 1 5 75 9 2 Indeed, the pool water offering radiological protection, the extraction of the assemblies out of the pool requires heavy and complex manipulations, in order to benefit from a continuity of this radiological protection. In addition, the water has a cooling function of these assemblies, which can make the extraction operation even more complex when these assemblies have a significant residual thermal power. Methods and devices for cleaning in a pool of fuel rod assemblies are described in the patents published under the numbers W02011040873, FR28o3o83, DE4129362, U85002079, US4683109, and US6231682. US6231682 discloses a cleaning device using at least one liquid and / or a cleaning gas, which comprises a rectangular frame-shaped body which defines an opening through which it can extend and move - an assembly of crayons to clean. This device comprises nozzles for spraying a cleaning fluid on the portion of the assembly of rods surrounded by the frame, which are connected to a supply duct delivering to the nozzles the cleaning fluid under pressure.

This device also comprises liquid intake orifices arranged opposite the spray nozzles and connected to a conduit for taking up the liquid sucked by these recovery orifices. This device is used to clean a fuel rod assembly during extraction of this assembly from the reactor or assembly storage rack, by projecting the delivered cleaning fluid at a pressure of from 3 bar to 150 psig. bar and flowing along a diagonal of the frame-shaped body. To obtain a more homogeneous cleaning of a rod assembly, this patent proposes to use two of these devices to respectively cause two diagonal flows against the current, or to cause a rotation of the device around the rod assembly.

A disadvantage of these methods and devices is that a substantial portion of the energy of the cleaning fluid is absorbed by the water in which the assembly is embedded. As a result, the frame of the cleaning device must be perfectly adjusted to the geometry of the assembly for the cleaning process to work. It is therefore necessary to change the device according to the geometry of the assembly to be cleaned, which requires having several devices and which requires many operations. SUMMARY OF THE INVENTION An object of the invention is to provide a method and a device for cleaning a bundle of bars or tubes such as an assembly of nuclear fuel rods, which is immersed in a liquid, particularly in within a reactor or storage pool, which is (are) improved and / or remedies, at least in part, to the shortcomings or disadvantages of known beam cleaning methods and devices immersed bars or tubes. According to one aspect of the invention, there is provided a device for cleaning a bundle of bars or tubes immersed in a liquid, which comprises a hollow body arranged to surround a portion of the bundle, and means for projecting a liquid cleaning to the portion of the beam, which are integral with the hollow body and which comprise at least one member - such as a nozzle - for the projection of the cleaning liquid; the projection member of the cleaning liquid is arranged to form a rotating jet whose envelope diverges from the projection member; the cleaning device comprises guide means integral with the hollow body and guiding the cleaning device in its movements relative to the beam; and the cleaning device further comprises means for injecting a gas which are integral with the hollow body and which comprise at least one gas injection member arranged to form a stream of gas which surrounds at least a part of the jet cleaning fluid. The cleaning device may comprise a suction duct 30 opening inside the hollow body, which makes it possible to evacuate a substantial part of the separated residues of the bars or tubes of the bundle by the jet of cleaning liquid, to a system treatment of these residues.

Thanks to the rotating jet of cleaning liquid, such as a rotating straight jet, and the presence of a stream of gas separating at least a portion of this jet of the immersion liquid from the assembly, the impact of the jet cleaning fluid on the bars or tubes of the beam is increased.

Moreover, the angle of incidence of the rotating jet of cleaning fluid whose envelope diverges on the bars or tubes of the bundle varies during a rotation of the jet and makes it possible to clean the surfaces of bars or tubes which are inside the beam, which surfaces can not be directly reached by a jet whose direction is fixed.

The variations in the incidence of the jet of cleaning liquid resulting from the rotation of the jet on the one hand, and the rotation of the cleaning device around the bundle of bars or tubes on the other hand, make it possible to increase the efficiency of the cleaning regardless of the spacing pitch of the beams or tubes of the bundle.

The means for guiding the device and the diverging nature of the envelope of the rotating jet of cleaning liquid make it possible to ensure a homogeneous cleaning of the portion of the bundle surrounded by the body of the device. The guiding means of the cleaning device also make it possible to ensure precise positioning of the body (bodies) for spraying cleaning liquid, as close as possible to the beam. The guiding means may also contribute, with the hollow body, to contain the shielding gas in the space through which the jet of cleaning liquid passes. The guiding means of the cleaning device may comprise at least one guiding structure delimiting a passage opening for the beam, the contour of which may for example be circular. In particular, these guide means may include such guide structures whose orifices are aligned along a sliding axis - and rotation - of the cleaning device around the beam. These orifices 30 have substantially identical dimensions (in particular diameters) which are adapted - in particular substantially equal (little greater) - to the transverse dimensions of the bundle.

This (these) guiding structure (s) can be realized (s), at least partially, in a material having a low coefficient of friction on the material forming the bars or tubes, for example in a material such as only polyethylene.

The liquid in which is immersed the assembly of rods may be water. The cleaning liquid may be an aqueous solution, in particular demineralised water. The shielding gas of the cleaning liquid jet may be air.

According to one embodiment, the cleaning device comprises at least two cleaning fluid projection members which are arranged on either side of the axis of sliding and rotation of the device around the beam, in particular diametrically opposed by report to this axis. This in particular makes it possible to reduce the support force of the device on the beam, which results from the impact of the liquid jets on the bundle of bars or tubes. Furthermore, the cleaning device may comprise a chamber surrounding an outlet orifice of the liquid-projection member, into which means - in particular a conduit - for injecting the pressurized-protection gas, and which comprises a wall pierced with an orifice extending in the extension of the outlet orifice of the liquid projection member. The orifice pierced in this wall has a shape and dimensions adapted to those of the section of the envelope (envelopes) of (the) jet (s) in the plane of this orifice - and this wall -. This favors the creation of a stream of gas protecting the jet of liquid, this stream being able to escape from the chamber through the orifice allowing the jet of liquid to pass through the wall, in particular through a peripheral portion of the orifice which is of small section, for example of annular shape, and extends between the envelope of the jet of liquid and the edge of this orifice. The casing of a liquid jet may have a substantially conical shape, of circular section; in this case in particular, the orifice provided in the wall of the chamber may have a circular or oblong contour, the dimensions of which are slightly greater than those of the projection of the envelope (envelopes) of the jet (s) in the plane of the wall. According to another aspect of the invention, there is provided a method of cleaning a submerged beam of rods or tubes, in particular an assembly of nuclear fuel rods immersed in a liquid, in which: cleaning liquid to the beam - or assembly - causing a jet of the cleaning liquid to rotate, and so that the envelope formed by the rotating jet diverges; A stream of gas is formed which surrounds at least a portion of the jet of cleaning liquid; and - a relative displacement of the rotating jet of liquid and the gas flow around it, with respect to the beam - at the assembly - is caused, preferably by guiding this displacement. Preferably, several rotating liquid jets are formed, the projections of the envelopes in a plane perpendicular to the rods, covering at least a substantial part of the cross-section of the bundle, in particular the whole of this section. Projections of rotating jet envelopes (in a plane perpendicular to the bars or tubes) may overlap. To form a stream of gas around a jet of cleaning liquid, a compressed gas is injected at a pressure greater than the immersion pressure of the jet member of the liquid jet and the portion of the beam extending next to this body. In particular, compressed gas is injected into the chamber at a pressure at least one bar higher than this immersion pressure, for example at a pressure ranging from about 2 to about 3 bar to About 10 bar above this immersion pressure. The supply of the nozzle (nozzle) producing the rotating jet of liquid can be made under a pressure of a few tens of bar above this immersion pressure, in particular under a pressure in the range of 100 bar. about 200 bar.

The respective flow rates and pressures for supplying gas and cleaning liquid may be chosen so as to obtain, at least in the gas injection chamber and, where appropriate, in the space separating this chamber from the bundle, a rotating jet. of liquid whose shell is hollow, in particular a rotary jet hollow cone. To control the progress of the cleaning of the beam, one can observe the beam with the aid of a camera immersed in the liquid receiving the beam. Other aspects, features, and advantages of the invention appear in the following description which refers to the accompanying figures and illustrates, without any limiting character, preferred embodiments of the invention. BRIEF DESCRIPTION OF THE FIGURES FIG. 1 illustrates in perspective a cleaning device engaged around an assembly of fuel rods. Figure 2 illustrates schematically in a plane perpendicular to the axis of sliding and rotation of the cleaning device, the main components of a cleaning device. FIG. 3 is a diagrammatic view in a plane containing the pivot axis of a rotating jet, of mounting a cleaning fluid spraying nozzle on a hollow body of a cleaning device having a chamber injecting a protective gas from the liquid jet. FIG. 4 is a diagrammatic view in a plane perpendicular to the axis of rotation of a rotating jet of cleaning liquid, the trace of the conical envelope of the jet of liquid in the plane of the opening provided in a wall; a gas injection chamber. FIG. 5 illustrates, in the same way as FIG. 4, the respective traces of the envelopes of two jets of liquid respectively produced by two nozzles of the cleaning device which are arranged side by side, in the plane of the opening provided for in FIG. a wall of a gas injection chamber. DETAILED DESCRIPTION OF THE INVENTION Unless explicitly or implicitly stated otherwise, elements or members - structurally or functionally identical or similar - are designated by identical reference numerals in the various figures.

Figure 1 illustrates a cleaning apparatus 10 engaged around an assembly 11 of fuel rods, partially shown, the assembly resting on a support 12 in a pool (not shown) filled with water. The assembly 11 consists essentially of a bundle of parallel rods 13, which extends along a longitudinal axis 14 and has a substantially rectangular cross section. Pencils containing a fissile material are assembled by members (or grids) 15 mechanical assembly ensuring the cohesion of the beam. The assembly 11 may be pivotally mounted and / or sliding along the axis 14, 10 on the support 12. Alternatively, or in addition, the cleaning device 10 may be pivotally mounted and / or sliding along the axis 14, by relative to the assembly The device 10 comprises a hollow body 16 comprising four flat lateral walls 17, parallel in pairs and joined together, surrounding a portion of the assembly 11, and forming a section of square section tube and of which the longitudinal axis is substantially coincident with the longitudinal axis 14 of the assembly. The hollow body 16 further comprises two flat end walls 18, which are integral with the side walls 17, extend perpendicular to the axis 14. longitudinal of the hollow body, and are respectively pierced by two central orifices 19 which are aligned along the axis 14, so that the assembly can extend through these orifices 19 and the hollow body 16, with a small clearance, and of that the pierced walls 18, 19 serve to guide the device 10 in its movements relative to the assembly 25 The device 10 comprises four nozzles 20 for producing four rotating jets of cleaning liquid inside the hollow body 16. For this purpose, the nozzles 20 are fed with pressurized cleaning liquid via conduits 21. The nozzles 20 are arranged in pairs on either side of the hollow body 16 and the axis 14. With reference to FIGS. to 3 in particular, each nozzle 20 is fixed to a wall 22 integral with one of the walls 17, so that the outlet orifice of the nozzle extends through - and / or in correspondence - with a pierced orifice 24 in this wall 22. With reference to FIG. 3 in particular, each wall 22 delimits, with the wall 17 to which the wall 22 is fixed, an airtight cavity or chamber 23 which is traversed by the jet of liquid produced by the corresponding nozzle. As illustrated in FIGS. 4 and 5 in particular, the straight jet 25 produced by each nozzle 20 pivots around the axis 26 of the nozzle, as illustrated by the arrows 27, thanks to a mechanism for rotating the jet which is integrated into the nozzle. nozzle 20.

It follows from this rotation of the jet 25 that this jet remains confined, during a rotation of the jet along the axis 26, in a jet containment envelope 28 which deviates from the axis 26 in "divergent" direction. as the progress of the jet 25 progresses. This divergent casing 28, in the form of a cone with an axis 26, forms in the planes of FIGS. 4 and 5 an annular "trace" centered on the axis 26 and of which the thickness corresponds to the diameter of the jet in the section plane considered; this trace is shown in gray in FIGS. 4 and 5. As illustrated in FIGS. 1 and 2, the device 10 furthermore comprises two air transport ducts 29 opening respectively into the two chambers 23. The ducts 29 are connected to a source (not shown) of compressed air, so as to inject the compressed air into the chambers 23. As illustrated in FIGS. 3 to 5, the wall 17 is pierced with an orifice 3o which extends in the extension, along of the axis 26, the outlet orifice 24 of the jet 25 25. In the embodiment illustrated in FIG. 4, the diameter of the circular orifice 30 is greater than the outside diameter of the trace of the envelope 28 of the jet. in the plane of the figure - and the orifice 30 -, so that a free space 31 of annular shape separates the envelope 28 from the edge of the orifice 30.

In the embodiment illustrated in FIG. 5, the orifice 30 pierced in the wall 17 has an oblong shape whose length is little greater than twice the diameter of the envelope 28 of the jet 25 in the plane of the wall 17, and whose width is little greater than the diameter of this envelope 28, so that a free space 31 of small section also separates the envelopes 28 from the edge of the orifice 30. In both embodiments, the air introduced under pressure in the chamber 23 can escape from this chamber by passing through the space 5 left free by the jet (s) 25 in the section of the orifice 3o, especially in the free space 31. This allows the formation of a stream of air 32 (see Figure 3) escaping from the chamber 23 by surrounding the jet (s) 25 cleaning liquid, if necessary until the impact of this (s) jet (s) on the portions of rods of the assembly 10 extending in the extension of the orifice 30. At least a portion of the r residues separated from the assembly rods by the liquid jet is discharged through a conduit 33 suction opening inside the hollow body 16 (cf. Figures 1 and 2). In order to cause a relative displacement of the rotating jet of liquid 25 and the surrounding gas flow with respect to the rod assembly 13, the cleaning device - and / or the assembly of rods, for example, can be suspended. 13 - to a handling device adapted to cause a relative rotation of the device 10 relative to the assembly 11, along the axis 14, and / or the relative sliding of the device 10 and the assembly 11, along the same axis 14. 20

Claims (4)

CLAIMS1 - Device (io) for cleaning a bundle (11) of bars or tubes (13) immersed in a liquid, which comprises a hollow body (16) arranged to surround a portion of the bundle, and projection means of a cleaning liquid to the portion of the bundle which are integral with the hollow body and which comprise at least one member (20) for spraying the cleaning liquid, characterized in that: - the member (20) for the projection of the cleaning liquid is arranged to form a rotating jet (25) (27) whose envelope (28) diverges from the projection member; - The cleaning device comprises guide means (18, 19) integral with the hollow body and guiding the cleaning device in its movements relative to the beam; and the cleaning device further comprises means (23, 29, 30, 31) for injecting a gas which are integral with the hollow body and which comprise at least one member (3o) for the injection of the arranged gas. to form a stream (32) of gas that surrounds at least a portion of the jet of cleaning liquid. 2 - Device according to claim 1 which comprises a chamber (23) 20 surrounding an orifice (24) outlet of the member (20) for liquid projection, into which open means (29) for injecting the gas, and which comprises a wall (17) pierced with an orifice (3o) extending in the extension of the outlet orifice (24) of the liquid projection member, and having a shape and dimensions adapted to those of the section of the envelope (28) - or the envelopes - of the jet (s) in the plane of this wall (17). 3 - Device according to claim 2 wherein the casing (28) of the jet (25) of liquid has a substantially conical shape, of circular section, and the orifice (30) provided in the wall (17) of the chamber ( 23) has a circular or oblong contour, the dimensions of which are slightly greater than those of the projection of the envelope (28) or the envelopes of the jet (s) in the plane of the wall (17). . 4 - Device according to any one of claims 1 to 3 wherein the guide means comprise at least one guide structure (18) defining a hole (19) for passage of the beam. - Device according to any one of claims 1 to 4 wherein 5 the guide means comprise guide structures (18) defining respective apertures (19) for passage which are aligned along an axis (14) of sliding and rotation the cleaning device (m) around the beam (11), and have appropriate dimensions - in particular substantially equal - to the transverse dimensions of the beam. 6 - Device according to any one of claims 1 to 5 which comprises at least two bodies (20) for the projection of the cleaning liquid which are arranged on either side of the axis (14) of sliding and rotation of the device around the beam, in particular diametrically opposite with respect to this axis. 7 - Device according to any one of claims 1 to 6 which comprises a suction duct (33) opening inside the hollow body for discharging separated residues of the bars or tubes of the beam by the jet of liquid. 8 - Method for cleaning a bundle (n) of bars or tubes (13) 20 immersed in a liquid, in which: - a cleaning liquid is projected towards the bundle by causing the rotation (27) of a jet ( 25) of the cleaning liquid, and so that the casing (28) formed by the rotating jet diverges; forming a stream (32) of gas surrounding at least a portion of the jet (25) of cleaning liquid; and - a relative displacement of the rotating jet of liquid and the surrounding gas flow, relative to the beam, is preferably caused by guiding this displacement. 9 - Process according to claim 8 wherein several rotating jets of liquid are formed, the projections of the envelopes in a plane perpendicular to the rods, cover at least a substantial part of the cross section of the beam.10 - Process according to claim 8 or 9 in which several rotating jets of liquid are formed, the projections of the envelopes of the jets in a plane perpendicular to the rods, overlap. 11 - Process according to any one of claims 8 to 10 wherein 5 the liquid in which is dipped the assembly of rods is water. 12 - Process according to any one of claims 8 to 11 wherein the cleaning liquid is an aqueous solution, in particular water. 13 - Process according to any one of claims 8 to 12 wherein the shielding gas of the cleaning liquid jet is air. 14 - Process according to any one of claims 8 to 13 wherein, to form a stream (32) of gas around the jet (25) of liquid, is injected a compressed gas at a pressure greater than the immersion pressure a member (20) for projecting the jet of cleaning liquid and the portion of the beam extending opposite this member. 15 - Process according to any one of claims 8 to 14 wherein is fed to the member (20) producing the rotating jet of liquid under a pressure of a few tens of bar above the immersion pressure of the organ (20) projecting the jet of liquid. 16 - Process according to any one of claims 8 to 15 wherein the beam is observed using a camera immersed in the liquid receiving the beam. 17. A method according to any one of claims 8 to 16 wherein a device according to any one of claims 1 to 7 is used, and wherein the bundle of rods or tubes is an assembly of nuclear fuel rods.