EP0555127A1 - Process and device for decontaminating a used nuclear steam-generator - Google Patents

Process and device for decontaminating a used nuclear steam-generator Download PDF

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Publication number
EP0555127A1
EP0555127A1 EP93400219A EP93400219A EP0555127A1 EP 0555127 A1 EP0555127 A1 EP 0555127A1 EP 93400219 A EP93400219 A EP 93400219A EP 93400219 A EP93400219 A EP 93400219A EP 0555127 A1 EP0555127 A1 EP 0555127A1
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EP
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Prior art keywords
tubes
solution
decontamination
bundle
primary part
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EP93400219A
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German (de)
French (fr)
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EP0555127B1 (en
Inventor
Michel Dubourg
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Areva NP SAS
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Framatome SA
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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
    • G21F9/001—Decontamination of contaminated objects, apparatus, clothes, food; Preventing contamination thereof
    • G21F9/002—Decontamination of the surface of objects with chemical or electrochemical processes
    • G21F9/004—Decontamination of the surface of objects with chemical or electrochemical processes of metallic surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C23G1/085—Iron or steel solutions containing HNO3
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B37/00—Component parts or details of steam boilers
    • F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
    • F22B37/48—Devices for removing water, salt, or sludge from boilers; Arrangements of cleaning apparatus in boilers; Combinations thereof with boilers
    • F22B37/483—Devices for removing water, salt, or sludge from boilers; Arrangements of cleaning apparatus in boilers; Combinations thereof with boilers specially adapted for nuclear steam generators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
    • F28F9/02—Header boxes; End plates

Definitions

  • the present invention relates to a method and an installation for decontamination of the primary part of a used steam generator of a pressurized light water nuclear reactor.
  • This primary part includes heat exchange elements, in particular a bundle of U-shaped tubes, the ends of which are connected to a water box and are fixed in a tubular plate. The external surface of the tubes of this bundle is in contact with the supply water of a secondary circuit.
  • the bundle tubes are subjected to significant stresses which can damage the tubes and cause leaks between the primary part and the secondary circuit.
  • the out-of-service steam generator emits high activity radiation reaching several hundred curies. This radiation makes transporting the steam generator very difficult and expensive.
  • the highly radioactive steam generator must be subject to periodic radiological monitoring.
  • this generator so as to reduce the volume of waste stored and to recover or recycle certain noble materials contained in the generator, in particular the Inconel usually used for the manufacture of bundle tubes.
  • the radioactive contamination of the steam generator is mainly distributed over the internal surface of the bundle tubes and the water box.
  • This contamination is due in particular to the presence of a layer of oxides containing radionuclides such as cobalt 60, cobalt 58 and manganese 54.
  • the contamination is concentrated in the thickness of the oxide layer (3 to 5 f..lm approximately) and superficially in the metal wall of the tubes to a thickness of approximately 3 f..lm.
  • the cerium solution constitutes an aggressive and strongly oxidizing chemical medium making it possible to erode the oxide layer and the contaminated surface.
  • the cerium is reduced to valence III and then regenerated to valence IV by injecting ozone into the solution.
  • the temperature of the solution must be below 60 ° so as not to inadvertently destroy the ozone injected.
  • the object of the invention is to effectively decontaminate the primary part of a steam generator, in particular the bundle of tubes, by using a limited volume of decontamination solution, this without creating any overpressure inside the primary part, without raising the temperature of the solution beyond 60 ° and minimizing the volumes of waste produced.
  • the primary part of the steam generator comprises a bundle of U-shaped tubes forming heat exchange elements, the tubes having their two ends connected respectively to the two compartments of a water box.
  • the bundle includes healthy tubes with open ends and defective tubes with plugged ends.
  • the liquid effluents are dried by first carrying out a centrifugation of the effluents so as to collect the insoluble waste from the effluents, and secondly by performing a vacuum evaporation of the effluents so as to collect the waste soluble.
  • the invention also relates to an installation for implementing the method defined above, characterized in that it comprises a closed-loop decontamination circuit comprising a tank for circulating decontamination solution, and means for putting circulating solution connected between the tank and the upstream end of the contaminated elements of the primary part of the steam generator, the installation further comprising means for ozonization of the decontamination solution.
  • FIG. 1 shows a decontamination installation for implementing the method according to the invention, designated by the general reference 10.
  • This installation 10 is connected to contaminated elements of a primary part of a steam generator 12 out of service of a pressurized light water nuclear reactor.
  • This steam generator 12 is stored horizontally on cradles 14,16 in an enclosure (not shown in the figures) built on the site of the nuclear power plant from which the disused steam generator comes.
  • the primary part of the steam generator comprises a bundle 18 of U-shaped tubes made of Inconel.
  • the imaginary envelope of the bundle 18 is shown in dashed lines.
  • the ends of the tubes of the bundle 18 are fixed in a tubular plate 20 and are connected to a water box 22 comprising two compartments 22A, 22B.
  • the defective or suspect tubes of the bundle have their ends closed by plugs (not shown in the figures). Healthy bundle tubes have their ends open.
  • Each compartment 22A, 22B of the water box has a sleeve 23A, 23B for connection to primary water pipes.
  • the pipes were disconnected from the steam generator when it was taken out of service.
  • the sleeves 23A, 23B delimit orifices allowing tools or apparatus to be introduced into the water box.
  • the installation 10 comprises a decontamination circuit 24 in which circulates in a closed loop a predetermined volume of decontamination solution, and means 25 for ozonation of the decontamination solution.
  • the circuit 24 includes a circulation tank 26 intended to contain at least part of the volume of decontamination solution, connected by a conduit 28 to the suction of a circulation pump 30.
  • the pump 30 is connected to a discharge conduit 32 connected by first removable connection means 34A, 34B to a first end of a subset of contaminated elements of the primary part of the steam generator. This subset of contaminated elements will be described in more detail later.
  • the circuit 24 also includes filtration means 36 supplied upstream by a conduit 38 connected by second removable connection means 34A, 34B at the second end of the subset of contaminated elements of the primary part of the steam generator.
  • the filtration means 36 are connected downstream by a conduit 40 to the circulation tank 26.
  • the filtration means 36 comprise two filters 42, 44 connected in parallel to the conduits 38 and 40. Each filter 42, 44 can be isolated from the circuit 24 by two valves 46, 48 arranged respectively upstream and downstream of the filter. A valve 50 bypass of the filters 42, 44 is connected between the conduits 38 and 40.
  • Means 52 for reversing the direction of circulation of the decontamination solution in the elements of the primary part connect the connection means 34A, 34B, on the one hand to the conduit 32 for delivery of the pump 30 and on the other hand to the duct 38 for supplying filters 42.44.
  • a valve 54 for bypassing the elements of the primary part is connected between the pipe 32 for discharging the pump 30 and the pipe 38 for supplying the filters 42, 44.
  • the ozonization means 25 comprise an ozonator 58 connected by a conduit 60 to an injection circuit 62 with a horn 64.
  • the ozonator 58 is connected to a reservoir 66 for supplying oxygen by a conduit 68 provided with a valve 69 with safety valve.
  • the injection circuit 62 comprises an injection pump 70, the suction of which is connected by a conduit 72 to the circulation tank 26 and the discharge of which is connected to the upstream end of the tube 64 by a conduit 74.
  • the downstream end of the tube 64 is connected by a conduit 76 to the circulation tank 26.
  • the conduits 72, 76 are respectively provided with valves 72A, 76A for isolating the means 25 for ozonation from the circuit 24 for circulation of the solution.
  • the installation 10 further comprises an auxiliary tank 78 connected to the circulation tank 26 by means 80 of content transfer.
  • This reservoir 78 the internal volume of which is substantially between 4 and 8 m 3 , is intended in particular for the preparation of the decontamination solution and for the intermediate storage of this solution after emptying the circulation tank 26.
  • the transfer means 80 comprise a conduit 82 connecting the circulation tanks to each other tion 26 and auxiliary 78, fitted with a reversible pump 84.
  • Agitation means 86 arranged in the auxiliary tank 78, make it possible in particular to mix the various constituents of the solution during its preparation.
  • auxiliary reservoir 78 The upper part of the auxiliary reservoir 78 is connected by a conduit 88 to means 90 for treating and discharging the gaseous atmosphere contained in the reservoir above the level of liquid.
  • means 90 comprise a very high efficiency filter 92, of known type, connected in series with an ozone destroyer 94 opening into the open air.
  • the upper part of the circulation tank 26 is connected to the upper part of the auxiliary tank 78 by a conduit 96 provided with a valve 98 with safety valve, allowing the communication of the gaseous atmospheres of the two circulation tanks 26 and auxiliary 78 .
  • the lower part of the auxiliary reservoir 78 is connected to means 100 for draining the solution from the reservoir comprising a conduit 102 provided with a drainage valve 104.
  • a first end of the conduit 102 is connected to the bottom of the reservoir 78 and the second end of the conduit 102 is connected to a collector of liquid effluents, not shown in the figures.
  • the bundle 18 is subdivided into several sub-assemblies each comprising a substantially identical number of tubes.
  • each sub-assembly comprises approximately four hundred tubes and the entire bundle comprises approximately eight to nine tube sub-assemblies.
  • FIG. 1 There is shown in solid line in FIG. 1 an imaginary envelope delimiting a sub-assembly 106 of neighboring tubes.
  • connection means 34A, 34B comprise flexible conduits 108, one end of which is connected to the decontamination circuit 24 and the second end of which is connected to a removable collector 110, shown in more detail in FIG. 2.
  • the conduits 108 pass through the orifices delimited by the sleeves 23A, 23B of the water box 22.
  • the collectors 110 have the general shape of a bell and are pressed against the tube plate with a gasket 20.
  • a first manifold 110 is arranged facing the upstream ends and a second manifold 110 is disposed facing the downstream ends of the tubes of the subassembly 106 .
  • FIG. 2 shows one of the collectors 110 connected to the sub-assembly 106 of the bundle 18.
  • This manifold 110 is positioned to the right of the open ends of healthy tubes 18A and possibly to the right of the closed ends of defective tubes 18B.
  • the collector 110 has a double edge 112, provided with a seal 114, delimiting a channel 116 for collecting possible leaks of the solution flowing through the collector 110.
  • the channel 116 is connected by an orifice 118, formed through the wall of the manifold 110, to a pipe 120 for draining leaks.
  • This conduit 120 is connected to a collector of liquid effluents, not shown in the figures.
  • the collectors 110 are positioned in the compartments of the water box and pressed against the tube plate 20 by known means; in particular by means of a robot with an articulated carrying arm of the type sold under the name "ROMEO", placed in the water box.
  • the contour of the edge 112 of a manifold has a variable shape as a function of the arrangement of the ends of the tubes in the tube plate 20.
  • the outline of the manifold 110 has a substantially square shape or substantially complementary to the outline of the wall of the water box.
  • the subassemblies 106 of tubes of the bundle are successively decontaminated by connecting them one after the other to the decontamination circuit 24 by means of the collectors 110 described above.
  • a volume of approximately 3 m 3 of decontamination solution is initially prepared in the auxiliary tank 78. This volume of solution makes it possible in particular to fill all of the healthy tubes of the subassembly that we want to decontaminate.
  • the decontamination solution comprises nitric acid imposing a pH of the solution between 0.5 and 1, and cerium nitrate in a proportion of 8 to 10 g / I.
  • cerium sulphate can be replaced by cerium nitrate.
  • each sub-assembly of tubes is subjected to the following steps.
  • the solution is put into circulation in the decontamination circuit 24 in a closed loop by means of the circulation pump 30. This solution is circulated simultaneously through all the healthy tubes of the same subassembly for a duration T of between 6 and 24 hours.
  • the latter is supplied with ozone using the ozonization means 25 so as to maintain an ozone concentration in the solution of approximately 2.5 ppm.
  • the decontamination solution reacts with the oxide layer covering the internal surface of the tubes and with the surface layer of the metal constituting the tubes.
  • the valence iron II of the oxide layer is oxidized to valence III and the valence III chromium of the oxide layer is oxidized to chromium of valence VI according to the chemical reaction below:
  • the valence III iron and the valence VI chromium are dissolved in the solution.
  • the valence III cerium (Ce3 + ions) is regenerated to valence IV cerium (Ce4 + ions) by ozone according to the chemical reaction below:
  • the temperature of the solution is maintained between 20 and 30 ° in order to ensure a sufficient lifetime of the ozone in the solution allowing it to regenerate valence III cerium.
  • the speed of circulation of the decontamination solution in the tubes of the bundle is between 2.5 cm / s and 25 cm / s so as to prevent the contaminated particles torn from the surface of the tubes from being redeposited in these same tubes.
  • the Inconel wall of the bundle tubes is superficially eroded by the decontamination solution, which in particular produces Cr 6+ , Fe 3+ and Ni2 + ions.
  • the erosion of the internal surface of the bundle tubes is homogenized by reversing the direction of circulation of the decontamination solution in these tubes approximately every hour, using inversion means 52.
  • the filtration means 36 make it possible to capture a part of the particles torn from the primary part of the steam generator.
  • the pressure drop across the operational filter becomes too great, it switches from one filter to another by means of valves 46,48 for isolating the filters. It is also possible, after a certain period of circulation of the solution, to stop the filtration by isolating the filters from the decontamination circuit 24 and by opening the bypass valve 50.
  • the injection of ozone in the solution is stopped and the entire volume of solution contained in the tubes is emptied of the bundle and in the decontamination circuit 24.
  • the decontamination solution is transferred to the auxiliary tank 78 by means of the pump 84, to be temporarily stored there.
  • the drainage valve 104 is opened and the solution is drained to an effluent collector liquids to be treated subsequently according to steps which will be described later.
  • the same solution can be used to decontaminate three subsets of about four hundred tubes. Decontamination of all of the sound tubes in the bundle is carried out in approximately eight to nine passes using approximately 9 m 3 of decontamination solution.
  • the tubes of the bundle sub-assembly are rinsed with a solution comprising demineralized water and oxygenated water.
  • the rinsing solution is introduced into the circulation tank 26 by known means, not shown in the figures, and the rinsing solution is circulated, by means of the circulation pump 30, through the healthy tubes of the subassembly. of the beam.
  • the hydrogen peroxide H 2 0 2 reacts with the residual cerium of valence IV and reduces it to cerium of valence III, according to the following chemical reaction:
  • the rinsing solution After rinsing the tubes, the rinsing solution is drained by known means, not shown in the figures. The drained rinsing solution is collected in a liquid effluent collector for further treatment according to steps which will be described later.
  • the decontamination circuit 24 After decontaminating and rinsing the healthy tubes of a subset of the bundle, the decontamination circuit 24 is connected to another subset of tubes to which the decontamination and rinsing steps described above are subjected.
  • the same decontamination solution is used or a new charge of the solution of substantially identical volume is prepared.
  • the two ends of the decontaminated healthy tubes are plugged and the caps of the defective tubes not decontaminated are pierced.
  • the two compartments 22A, 22B of the water box are connected by the defective open tubes.
  • the decontamination circuit 24 is connected to a sub-assembly 121 of the primary part of the steam generator comprising the two compartments 22A, 22B of the water box and the defective tubes opened out from the bundle. For reasons of clarity, there is shown in Figure 3, a single defective tube 18B.
  • the sleeves 23A, 23B of the water box are closed by plates 122A, 122B provided with orifices for connection to the conduits 108 connecting the water box to the decontamination circuit 24.
  • the decontamination of the water box and defective tubes is carried out by circulating through them a volume of decontamination solution of the type described above, according to steps analogous to those of decontamination of healthy tubes.
  • Defective tubes present a risk of leakage at pressures in the region of 150 bars. On the other hand, this risk of leakage is eliminated by causing the decontamination solution to circulate in the defective tubes at a pressure substantially equal to atmospheric pressure.
  • the volume of solution used is a function of the total volume delimited by the compartments 22A, 22B of the water box and by the defective tubes which must be filled with solution.
  • the water box and the defective tubes are rinsed at the end of their decontamination with a rinsing solution of the type described above, according to steps analogous to those of rinsing the healthy tubes of the bundle.
  • liquid effluents comprising the altered decontamination and rinsing solutions are collected in a collector, not shown in the figures, for further treatment.
  • An agent comprising hydrogen peroxide is injected into the liquid effluents in order to reduce the Ce4 + ions to Ce3 + ions and subsequently store the cerium at valence III.
  • liquid effluents are then neutralized by injection of an agent comprising soda, then transferred to a drying installation (not shown in the figures) in which they are subjected to evaporation under vacuum.
  • the liquid effluents can be drained by first carrying out a centrifugation of the effluents so as to collect the insoluble waste, and secondly by carrying out a vacuum evaporation of the effluents so as to collect the soluble waste .
  • the dried effluents are confined in known type enclosures suitable for the storage of low and medium activity nuclear waste. These enclosures can be concrete or metallic. In the example described, the total mass of dried effluents after decontamination of the entire bundle and the water box is approximately 1500 Kg.
  • the clogged filters used in the decontamination circuit are compacted. These filters collect approximately 50% of the solid particles torn away by the decontamination solution from the primary part of the steam generator.
  • the total volume of waste comprising compacted filters, dried effluents and containment concrete is approximately 5 m 3.
  • the decontamination process according to the invention makes it possible to obtain a decontamination factor, defined by the ratio of the radiation field before decontamination to the radiation field after decontamination, greater than 1000 and which can reach or even exceed 15000.
  • the decontamination solution may also contain sulfuric acid. You can also replace the nitric acid in the solution with sulfuric acid.
  • the decontamination of the elements of the primary water circuit is carried out without overpressure, at a temperature below 60 °.
  • the decontamination process according to the invention makes it possible to simultaneously decontaminate a group of tubes in the bundle and to reduce the volume of waste produced by the decontamination to a few cubic meters.
  • effluents produced can be stored in standard enclosures.
  • the decontamination solution that has been described has a composition suitable for optimally decontaminating a bundle of primary water tubes made of Inconel, but this solution can also be used to decontaminate stainless steel elements.
  • the decontamination process according to the invention can also be applied to a steam generator comprising a bundle of straight primary water tubes. These tubes are connected at each end to a tube plate and to a water box.
  • a tube sub-assembly is connected to the decontamination circuit by means of collectors fixed to the tubular plates of the ends of the bundle.

Abstract

The primary part comprises a bundle (18) of U-shaped tubes connected to a water box (22), the bundle (18) comprising healthy tubes with open ends and defective tubes with blocked ends. According to the process the bundle (18) is subdivided into a number of subassemblies (106), each comprising a substantially identical number of tubes. An acidic decontaminating solution containing cerium is circulated successively in each subassembly (106), simultaneously in all the healthy tubes of the subassembly. The ends of the decontaminated healthy tubes are then plugged, the plugs of the undecontaminated defective tubes are pierced and the decontaminating solution is circulated in the water box (22) and the defective tubes. The liquid effluents are neutralised, taken to dryness and confined in standard storage enclosures. <IMAGE>

Description

La présente invention concerne un procédé et une installation de décontamination de la partie primaire d'un générateur de vapeur usagé d'un réacteur nucléaire à eau légère sous pression.The present invention relates to a method and an installation for decontamination of the primary part of a used steam generator of a pressurized light water nuclear reactor.

Cette partie primaire comporte des éléments d'échange de chaleur, en particulier un faisceau de tubes en U dont les extrémités sont raccordées à une boîte à eau et sont fixées dans une plaque tubulaire. La surface externe des tubes de ce faisceau est en contact avec l'eau d'alimentation d'un circuit secondaire.This primary part includes heat exchange elements, in particular a bundle of U-shaped tubes, the ends of which are connected to a water box and are fixed in a tubular plate. The external surface of the tubes of this bundle is in contact with the supply water of a secondary circuit.

Pendant le fonctionnement du générateur de vapeur, les tubes du faisceau sont soumis à des contraintes importantes pouvant endommager les tubes et provoquer des fuites entre la partie primaire et le circuit secondaire.During operation of the steam generator, the bundle tubes are subjected to significant stresses which can damage the tubes and cause leaks between the primary part and the secondary circuit.

Les tubes défectueux ou suspects sont mis hors service, au cours d'opérations de maintenance et de contrôle, en obturant leurs extrémités par des bouchons.Defective or suspect tubes are taken out of service during maintenance and inspection operations, closing their ends with plugs.

Lorsque la proportion de tubes bouchés dans le faisceau devient trop importante, notamment lorsque plus de 10% des tubes dans le faisceau sont défectueux, les performances du générateur de vapeur diminuent notablement et ce dernier est retiré du service et éventuellement remplacé.When the proportion of tubes blocked in the bundle becomes too large, in particular when more than 10% of the tubes in the bundle are defective, the performance of the steam generator decreases notably and the latter is withdrawn from service and possibly replaced.

Le générateur de vapeur hors service émet des rayonnements de forte activité atteignant plusieurs centaines de curie. Ce rayonnement rend le transport du générateur de vapeur très difficile et coûteux.The out-of-service steam generator emits high activity radiation reaching several hundred curies. This radiation makes transporting the steam generator very difficult and expensive.

On préfère donc stocker le générateur de vapeur hors service dans une enceinte construite sur le site même de la centrale nucléaire d'où il provient.We therefore prefer to store the steam generator out of service in an enclosure built on the site of the nuclear power plant where it comes from.

Pendant toute la période de stockage, le générateur de vapeur fortement radioactif doit faire l'objet d'une surveillance radiologique périodique. Pour éviter d'avoir à effectuer la surveillance du générateur de vapeur hors service, et pour remédier à divers problèmes de stockage, on a envisagé de démanteler ce générateur de façon à réduire le volume des déchets stockés et à récupérer ou recycler certains matériaux nobles contenus dans le générateur, en particulier l'Inconel utilisé habituellement pour la fabrication des tubes du faisceau.During the entire storage period, the highly radioactive steam generator must be subject to periodic radiological monitoring. To avoid having to monitor the steam generator out of service, and to remedy various storage problems, it has been envisaged to dismantle this generator so as to reduce the volume of waste stored and to recover or recycle certain noble materials contained in the generator, in particular the Inconel usually used for the manufacture of bundle tubes.

Préalablement au démantèlement du générateur de vapeur, il est nécessaire de réduire l'activité de celui-ci en le décontaminant.Prior to dismantling the steam generator, it is necessary to reduce its activity by decontaminating it.

La contamination radioactive du générateur de vapeur est essentiellement répartie sur la surface interne des tubes du faisceau et de la boîte à eau.The radioactive contamination of the steam generator is mainly distributed over the internal surface of the bundle tubes and the water box.

Cette contamination est due notamment à la présence d'une couche d'oxydes contenant des radionu- cléïdes tels que le cobalt 60, le cobalt 58 et le manganèse 54.This contamination is due in particular to the presence of a layer of oxides containing radionuclides such as cobalt 60, cobalt 58 and manganese 54.

La contamination est concentrée dans l'épaisseur de la couche d'oxydes (3 à 5 f..lm environ) et superficiellement dans la paroi métallique des tubes sur une épaisseur d'environ 3 f..lm.The contamination is concentrated in the thickness of the oxide layer (3 to 5 f..lm approximately) and superficially in the metal wall of the tubes to a thickness of approximately 3 f..lm.

On connaît déjà dans l'état de la technique, notamment dans WO 90/0 1774, un procédé de décontamination d'une surface comportant des dépôts d'oxydes radioactifs au moyen de cérium de valence IV sous forme d'ions Ce4+ en solution dans un milieu acide.Already known in the prior art, in particular in WO 90/0 1774, a method for decontaminating a surface comprising deposits of radioactive oxides by means of valence IV cerium in the form of Ce4 + ions in solution in an acid medium.

La solution de cérium constitue un milieu chimique agressif et fortement oxydant permettant d'éroder la couche d'oxydes et la surface contaminée. Au cours de la décontamination, le cérium est réduit à la valence III puis régénéré à la valence IV par injection d'ozone dans la solution. La température de la solution doit être inférieure à 60° pour ne pas détruire intempestivement l'ozone injecté.The cerium solution constitutes an aggressive and strongly oxidizing chemical medium making it possible to erode the oxide layer and the contaminated surface. During decontamination, the cerium is reduced to valence III and then regenerated to valence IV by injecting ozone into the solution. The temperature of the solution must be below 60 ° so as not to inadvertently destroy the ozone injected.

L'invention a pour but de décontaminer efficacement la partie primaire d'un générateur de vapeur, en particulier le faisceau de tubes, en utilisant un volume limité de solution de décontamination, ceci sans créer de surpression à l'intérieur de la partie primaire, sans élever la température de la solution au delà de 60° et en minimisant les volumes de déchets produits.The object of the invention is to effectively decontaminate the primary part of a steam generator, in particular the bundle of tubes, by using a limited volume of decontamination solution, this without creating any overpressure inside the primary part, without raising the temperature of the solution beyond 60 ° and minimizing the volumes of waste produced.

A cet effet l'invention a pour objet un procédé de décontamination de la partie primaire d'un générateur de vapeur usagé d'un réacteur nucléaire à eau légère sous pression, cette partie primaire comportant une pluralité d'éléments d'échange de chaleur, le procédé comprenant la mise en contact des surfaces contaminées de la partie primaire avec une solution de décontamination acide comportant du cérium de valence IV sous forme d'ions Ce4+ , caractérisé par le fait qu'on subdivise la pluralité d'éléments d'échange de chaleur contaminés en plusieurs sous-ensembles et qu'on fait subir successivement à chaque sous-ensemble les étapes de décontamination suivantes :

  • - on fait circuler en circuit fermé un volume prédéterminé de solution de décontamination dans les éléments contaminés du sous-ensemble, pendant une durée T, en alimentant continuellement la solution de décontamination en ozone,
  • - on vidange la solution de décontamination,
  • - on fait circuler une solution de rinçage dans le sous-ensemble d'éléments contaminés,
  • - on vidange la solution de rinçage.
To this end, the subject of the invention is a process for decontaminating the primary part of a used steam generator of a pressurized light water nuclear reactor, this primary part comprising a plurality of heat exchange elements, the process comprising bringing the contaminated surfaces of the primary part into contact with an acidic decontamination solution comprising valence IV cerium in the form of Ce4 + ions, characterized in that the plurality of exchange elements is subdivided contaminated heat in several sub-assemblies and which each sub-assembly is subjected successively to the following decontamination steps:
  • a predetermined volume of decontamination solution is circulated in a closed circuit in the contaminated elements of the sub-assembly, for a period T, by continuously supplying the decontamination solution with ozone,
  • - the decontamination solution is drained,
  • - a rinsing solution is circulated in the subset of contaminated elements,
  • - the rinsing solution is drained.

Habituellement, la partie primaire du générateur de vapeur comporte un faisceau de tubes en U formant des éléments d'échange de chaleur, les tubes ayant leurs deux extrémités raccordées respectivement aux deux compartiments d'une boîte à eau. Le faisceau comprend des tubes sains dont les extrémités sont ouvertes et des tubes défectueux dont les extrémités sont obturées par des bouchons.Usually, the primary part of the steam generator comprises a bundle of U-shaped tubes forming heat exchange elements, the tubes having their two ends connected respectively to the two compartments of a water box. The bundle includes healthy tubes with open ends and defective tubes with plugged ends.

Suivant d'autres caractéristiques de l'invention:

  • - on subdivise le faisceau en plusieurs sous-ensembles comportant chacun un nombre sensiblement identique de tubes, on fait circuler la solution de décontamination successivement dans chaque sous-ensemble de tubes, simultanément dans tous les tubes sains d'un même sous-ensemble , et après avoir décontaminé tous les tubes sains du faisceau, on bouche les deux extrémités des tubes sains décontaminés, et on perce les bouchons des tubes défectueux non décontaminés, on fait circuler la solution de décontamination à travers les deux compartiments de la boîte à eau et les tubes défectueux,
  • - la solution de décontamination comprend de l'acide nitrique imposant un pH de la solution compris entre 0,5 et 1, du nitrate de cérium suivant une proportion de 8 à 10 g/I, et de l'ozone suivant une concentration de 2,5 ppm,
  • - la température de la solution est comprise entre 20 et 30°,
  • - chaque sous-ensemble du faisceau comprend environ 400 tubes et le volume de solution de décontamination est d'environ 3 m3,
  • - la durée T de circulation de la solution de décontamination dans chaque sous-ensemble de tubes du faisceau est comprise entre 6 et 24 h,
  • - on inverse le sens de circulation de la solution de décontamination dans les tubes du faisceau environ toutes les heures,
  • - la vitesse de circulation de la solution de décontamination dans les tubes du faisceau est comprise entre 2,5 cm/s et 25 cm/s,
  • - la solution de rinçage comprend de l'eau déminéralisée et de l'eau oxygénée,
  • - la solution de décontamination circulant dans les éléments contaminés de la partie primaire est filtrée à travers au moins un filtre captant les particules arrachées par la solution à la partie primaire, ceci tant que la perte de charge à travers le filtre est inférieure à une valeur prédéterminée,
  • - on traite les effluents liquides comprenant la solution de décontamination et la solution de rinçage après leur utilisation dans les éléments de la partie primaire, en effectuant les étapes suivantes, on injecte dans les effluents liquides un agent réduisant les ions Ce4+ en ions Ce3+, on injecte un agent neutralisant la solution, on assèche les effluents liquides, et on confine les effluents asséchés dans des enceintes adaptées pour le stockage de déchets de faible et moyenne activité,
  • - l'agent de réduction des ions Ce4+ en ions Ce3+ comprend de l'eau oxygénée,
  • - l'agent de neutralisation des effluents comprend de la soude,
  • - on assèche les effluents liquides par évaporation sous vide.
According to other characteristics of the invention:
  • - the bundle is subdivided into several sub-assemblies, each comprising a substantially identical number of tubes, the decontamination solution is circulated successively in each sub-assembly of tubes, if simultaneously in all the healthy tubes of the same sub-assembly, and after decontaminating all the healthy tubes of the bundle, the two ends of the decontaminated healthy tubes are plugged, and the caps of the defective tubes not decontaminated are pierced, the decontamination solution through the two compartments of the water box and the defective tubes,
  • - the decontamination solution comprises nitric acid imposing a pH of the solution between 0.5 and 1, cerium nitrate in a proportion of 8 to 10 g / I, and ozone in a concentration of 2 , 5 ppm,
  • - the temperature of the solution is between 20 and 30 °,
  • - each sub-assembly of the bundle comprises approximately 400 tubes and the volume of decontamination solution is approximately 3 m 3 ,
  • the duration T of circulation of the decontamination solution in each subset of tubes in the bundle is between 6 and 24 h,
  • - the direction of circulation of the decontamination solution in the bundle tubes is reversed approximately every hour,
  • - the speed of circulation of the decontamination solution in the bundle tubes is between 2.5 cm / s and 25 cm / s,
  • - the rinsing solution includes demineralized water and oxygenated water,
  • - the decontamination solution circulating in the contaminated elements of the primary part is filtered through at least one filter capturing the particles torn away by the solution from the primary part, this as long as the pressure drop across the filter is less than a value predetermined,
  • - the liquid effluents are treated comprising the decontamination solution and the rinsing solution after their use in the elements of the primary part, by performing the following steps, an agent reducing the Ce4 + ions into Ce3 + ions is injected into the liquid effluents, injects a solution neutralizing agent, the liquid effluents are dried, and the dried effluents are confined in enclosures suitable for the storage of low and medium activity waste,
  • the agent for reducing Ce4 + ions to Ce3 + ions includes hydrogen peroxide,
  • - the effluent neutralizing agent comprises soda,
  • - the liquid effluents are dried by vacuum evaporation.

En variante, on assèche les effluents liquides en effectuant, dans un premier temps, une centrifugation des effluents de façon à recueillir les déchets insolubles des effluents, et dans un deuxième temps, en effectuant une évaporation sous vide des effluents de façon à recueillir les déchets solubles.As a variant, the liquid effluents are dried by first carrying out a centrifugation of the effluents so as to collect the insoluble waste from the effluents, and secondly by performing a vacuum evaporation of the effluents so as to collect the waste soluble.

L'invention a également pour objet une installation pour la mise en oeuvre du procédé défini ci-dessus, caractérisée en ce qu'elle comporte un circuit de décontamination en boucle fermée comprenant un réservoir de circulation de solution de décontamination, et des moyens de mise en circulation de la solution raccordés entre le réservoir et l'extrémité amont des éléments contaminés de la partie primaire du générateur de vapeur, l'installation comprenant de plus des moyens d'ozonation de la solution de décontamination.The invention also relates to an installation for implementing the method defined above, characterized in that it comprises a closed-loop decontamination circuit comprising a tank for circulating decontamination solution, and means for putting circulating solution connected between the tank and the upstream end of the contaminated elements of the primary part of the steam generator, the installation further comprising means for ozonization of the decontamination solution.

Suivant d'autres caractéristiques de cette installation :

  • - le circuit de décontamination en boucle fermée comprend des moyens de filtration raccordés entre l'extrémité aval des éléments contaminés de la partie primaire et le réservoir de circulation,
  • - l'installation comporte des moyens d'inversion du sens de circulation de la solution de décontamination dans les éléments contaminés de la partie primaire du générateur de vapeur,
  • - les moyens de filtration comprennent au moins deux filtres raccordés en parallèle, des moyens pour isoler chaque filtre du circuit de décontamination et des moyens de dérivation des filtres,
  • - les moyens d'ozonation comprennent un ozo- neur raccordé à un mélangeur à trompe dont l'extrémité amont est alimentée en solution de décontamination par une pompe raccordée au réservoir de circulation et dont l'extrémité aval est raccordée au réservoir de circulation,
  • - l'installation comprend un réservoir auxiliaire, relié au réservoir de circulation par des moyens de transfert de contenu, destiné notamment à la préparation de la solution de décontamination et au stockage intermédiaire de la solution de décontamination après vidange du réservoir de circulation,
  • - le circuit de décontamination est raccordé par des moyens de raccordement amovibles aux extrémités amont et aval d'un sous-ensemble d'éléments contaminés de la partie primaire du générateur de vapeur,
  • - les moyens de raccordement comprennent deux collecteurs amovibles, raccordant respectivement les extrémités amont et aval d'un sous-ensemble de tubes du faisceau au circuit de décontamination, le bord des collecteurs étant plaqué à joint étanche contre une plaque tubulaire de fixation des extrémités des tubes du faisceau, les deux collecteurs étant disposés l'un en regard des extrémités amont et l'autre en regard des extrémités aval des tubes du sous-ensemble,
  • - les collecteurs de raccordement comportent chacun un double bord délimitant un canal destiné à recueillir des fuites éventuelles de la solution circulant dans le collecteur, ce canal étant raccordé à un collecteur de fuites.
According to other characteristics of this installation:
  • the closed-loop decontamination circuit comprises filtration means connected between the downstream end of the contaminated elements of the primary part and the circulation tank,
  • the installation includes means for reversing the direction of circulation of the decontamination solution in the contaminated elements of the primary part of the steam generator,
  • the filtration means comprise at least two filters connected in parallel, means for isolating each filter from the decontamination circuit and means for deriving the filters,
  • the ozonization means comprise an ozone generator connected to a trumpet mixer the upstream end of which is supplied with decontamination solution by a pump connected to the circulation tank and the downstream end of which is connected to the circulation tank,
  • the installation comprises an auxiliary tank, connected to the circulation tank by content transfer means, intended in particular for the preparation of the decontamination solution and for the intermediate storage of the decontamination solution after emptying the circulation tank,
  • the decontamination circuit is connected by removable connection means at the upstream and downstream ends of a subset of contaminated elements of the primary part of the steam generator,
  • the connection means comprise two removable collectors, respectively connecting the upstream and downstream ends of a subset of tubes of the bundle to the decontamination circuit, the edge of the collectors being pressed against a tubular plate for fixing the ends of the bundle tubes, the two collectors being arranged one facing the upstream ends and the other facing the downstream ends of the tubes of the subassembly,
  • - The connection collectors each have a double edge delimiting a channel intended to collect possible leaks of the solution circulating in the collector, this channel being connected to a leak collector.

Un exemple de réalisation de l'invention va être décrit ci-dessous en se référant aux dessins annexés dans lesquels :

  • - la figure 1 est une vue schématique d'une installation de décontamination raccordée aux extrémités amont et aval d'un sous-ensemble de tubes du faisceau, pour la mise en oeuvre du procédé selon l'invention ;
  • - la figure 2 est une vue en coupe schématique d'un collecteur de raccordement amovible ;
  • - la figure 3 est une vue similaire à la figure 1 dans laquelle l'installation de décontamination est raccordée aux deux compartiments de la boîte à eau du générateur de vapeur.
An exemplary embodiment of the invention will be described below with reference to the accompanying drawings in which:
  • - Figure 1 is a schematic view of a decontamination installation connected to the upstream and downstream ends of a subset of tubes of the bundle, for the implementation of the method according to the invention;
  • - Figure 2 is a schematic sectional view of a removable connection manifold;
  • - Figure 3 is a view similar to Figure 1 in which the decontamination installation is connected to the two compartments of the water box of the steam generator.

On voit à la figure 1 une installation de décontamination pour la mise en oeuvre du procédé selon l'invention, désignée par la référence générale 10. Cette installation 10 est raccordée à des éléments contaminés d'une partie primaire d'un générateur de vapeur 12 hors service d'un réacteur nucléaire à eau légère sous pression. Ce générateur de vapeur 12 est stocké horizontalement sur des berceaux 14,16 dans une enceinte (non représentée sur les figures) construite sur le site même de la centrale nucléaire d'où provient le générateur de vapeur désaffecté.FIG. 1 shows a decontamination installation for implementing the method according to the invention, designated by the general reference 10. This installation 10 is connected to contaminated elements of a primary part of a steam generator 12 out of service of a pressurized light water nuclear reactor. This steam generator 12 is stored horizontally on cradles 14,16 in an enclosure (not shown in the figures) built on the site of the nuclear power plant from which the disused steam generator comes.

La partie primaire du générateur de vapeur comprend un faisceau 18 de tubes en U en Inconel. On a représenté en traits mixtes l'enveloppe imaginaire du faisceau 18. Les extrémités des tubes du faisceau 18 sont fixées dans une plaque tubulaire 20 et sont raccordées à une boîte à eau 22 comportant deux compartiments 22A,22B.The primary part of the steam generator comprises a bundle 18 of U-shaped tubes made of Inconel. The imaginary envelope of the bundle 18 is shown in dashed lines. The ends of the tubes of the bundle 18 are fixed in a tubular plate 20 and are connected to a water box 22 comprising two compartments 22A, 22B.

Les tubes défectueux ou suspects du faisceau ont leurs extrémités obturées par des bouchons (non représentés sur les figures). Les tubes sains du faisceau ont leurs extrémités ouvertes.The defective or suspect tubes of the bundle have their ends closed by plugs (not shown in the figures). Healthy bundle tubes have their ends open.

Chaque compartiment 22A,22B de la boîte à eau comporte un manchon 23A,23B de raccordement à des tuyauteries d'eau primaire. Les tuyauteries ont été déconnectées du générateur de vapeur au moment de la mise hors service de celui-ci. Les manchons 23A,23B délimitent des orifices permettant d'introduire des outils ou des appareillages dans la boîte à eau.Each compartment 22A, 22B of the water box has a sleeve 23A, 23B for connection to primary water pipes. The pipes were disconnected from the steam generator when it was taken out of service. The sleeves 23A, 23B delimit orifices allowing tools or apparatus to be introduced into the water box.

L'installation 10 comprend un circuit de décontamination 24 dans lequel circule en boucle fermée un volume prédéterminé de solution de décontamination, et des moyens 25 d'ozonation de la solution de décontamination.The installation 10 comprises a decontamination circuit 24 in which circulates in a closed loop a predetermined volume of decontamination solution, and means 25 for ozonation of the decontamination solution.

Le circuit 24 comporte un réservoir 26 de circulation destiné à contenir une partie au moins du volume de solution de décontamination, raccordé par un conduit 28 à l'aspiration d'une pompe de circulation 30. La pompe 30 est raccordé à un conduit de refoulement 32 relié par des premiers moyens de raccordement amovibles 34A,34B à une première extrémité d'un sous-ensemble d'éléments contaminés de la partie primaire du générateur de vapeur. Ce sous-ensemble d'éléments contaminés sera décrit plus en détail ultérieurement.The circuit 24 includes a circulation tank 26 intended to contain at least part of the volume of decontamination solution, connected by a conduit 28 to the suction of a circulation pump 30. The pump 30 is connected to a discharge conduit 32 connected by first removable connection means 34A, 34B to a first end of a subset of contaminated elements of the primary part of the steam generator. This subset of contaminated elements will be described in more detail later.

Le circuit 24 comporte également des moyens de filtration 36 alimentés en amont par un conduit 38 relié par des seconds moyens de raccordement amovibles 34A,34B à la seconde extrémité du sous-ensemble d'éléments contaminés de la partie primaire du générateur de vapeur. Les moyens de filtration 36 sont raccordés en aval par un conduit 40 au réservoir de circulation 26.The circuit 24 also includes filtration means 36 supplied upstream by a conduit 38 connected by second removable connection means 34A, 34B at the second end of the subset of contaminated elements of the primary part of the steam generator. The filtration means 36 are connected downstream by a conduit 40 to the circulation tank 26.

Les moyens de filtration 36 comprennent deux filtres 42,44 raccordés en parallèle aux conduits 38 et 40. Chaque filtre 42,44 peut être isolé du circuit 24 par deux vannes 46,48 disposées respectivement en amont et en aval du filtre. Une vanne 50 de dérivation des filtres 42,44 est raccordée entre les conduits 38 et 40.The filtration means 36 comprise two filters 42, 44 connected in parallel to the conduits 38 and 40. Each filter 42, 44 can be isolated from the circuit 24 by two valves 46, 48 arranged respectively upstream and downstream of the filter. A valve 50 bypass of the filters 42, 44 is connected between the conduits 38 and 40.

Des moyens 52 d'inversion du sens de circulation de la solution de décontamination dans les éléments de la partie primaire relient les moyens de raccordement 34A,34B, d'une part au conduit 32 de refoulement de la pompe 30 et d'autre part au conduit 38 d'alimentation des filtres 42,44.Means 52 for reversing the direction of circulation of the decontamination solution in the elements of the primary part connect the connection means 34A, 34B, on the one hand to the conduit 32 for delivery of the pump 30 and on the other hand to the duct 38 for supplying filters 42.44.

Une vanne 54 de dérivation des éléments de la partie primaire est raccordée entre le conduit 32 de refoulement de la pompe 30 et le conduit 38 d'alimentation des filtres 42,44.A valve 54 for bypassing the elements of the primary part is connected between the pipe 32 for discharging the pump 30 and the pipe 38 for supplying the filters 42, 44.

Les moyens 25 d'ozonation comprennent un ozo- neur 58 relié par un conduit 60 à un circuit d'injection 62 à trompe 64.The ozonization means 25 comprise an ozonator 58 connected by a conduit 60 to an injection circuit 62 with a horn 64.

L'ozoneur 58 est raccordé à un réservoir 66 d'alimentation en oxygène par un conduit 68 muni d'une vanne 69 à soupape de sûreté.The ozonator 58 is connected to a reservoir 66 for supplying oxygen by a conduit 68 provided with a valve 69 with safety valve.

Le circuit d'injection 62 comprend une pompe d'injection 70 dont l'aspiration est raccordée par un conduit 72 au réservoir de circulation 26 et dont le refoulement est raccordé à l'extrémité amont de la trompe 64 par un conduit 74. L'extrémité aval de la trompe 64 est raccordée par un conduit 76 au réservoir 26 de circulation.The injection circuit 62 comprises an injection pump 70, the suction of which is connected by a conduit 72 to the circulation tank 26 and the discharge of which is connected to the upstream end of the tube 64 by a conduit 74. The downstream end of the tube 64 is connected by a conduit 76 to the circulation tank 26.

Les conduits 72,76 sont respectivement munis de vannes 72A,76A pour isoler les moyens 25 d'ozona- tion du circuit 24 de circulation de la solution.The conduits 72, 76 are respectively provided with valves 72A, 76A for isolating the means 25 for ozonation from the circuit 24 for circulation of the solution.

L'installation 10 comporte de plus un réservoir auxiliaire 78 relié au réservoir de circulation 26 par des moyens 80 de transfert de contenu. Ce réservoir 78, dont le volume interne est sensiblement compris entre 4 et 8 m3, est destiné notamment à la préparation de la solution de décontamination et au stockage intermédiaire de cette solution après vidange du réservoir de circulation 26.The installation 10 further comprises an auxiliary tank 78 connected to the circulation tank 26 by means 80 of content transfer. This reservoir 78, the internal volume of which is substantially between 4 and 8 m 3 , is intended in particular for the preparation of the decontamination solution and for the intermediate storage of this solution after emptying the circulation tank 26.

Les moyens 80 de transfert comprennent un conduit 82 reliant entre eux les réservoirs de circulation 26 et auxiliaire 78, munis d'une pompe réversible 84.The transfer means 80 comprise a conduit 82 connecting the circulation tanks to each other tion 26 and auxiliary 78, fitted with a reversible pump 84.

Des moyens 86 d'agitation, disposés dans le réservoir auxiliaire 78, permettent notamment de mélanger les divers constituants de la solution au cours de sa préparation.Agitation means 86, arranged in the auxiliary tank 78, make it possible in particular to mix the various constituents of the solution during its preparation.

La partie supérieure du réservoir auxiliaire 78 est raccordée par un conduit 88 à des moyens 90 de traitement et d'évacuation de l'atmosphère gazeuse contenue dans le réservoir au dessus du niveau de liquide. Ces moyens 90 comprennent un filtre à très haute efficacité 92, de type connu, raccordé en série avec un destructeur d'ozone 94 débouchant à l'air libre.The upper part of the auxiliary reservoir 78 is connected by a conduit 88 to means 90 for treating and discharging the gaseous atmosphere contained in the reservoir above the level of liquid. These means 90 comprise a very high efficiency filter 92, of known type, connected in series with an ozone destroyer 94 opening into the open air.

La partie supérieure du réservoir de circulation 26 est reliée à la partie supérieure du réservoir auxiliaire 78 par un conduit 96 muni d'une vanne 98 à soupape de sûreté, permettant la mise en communication des atmosphères gazeuses des deux réservoirs de circulation 26 et auxiliaire 78.The upper part of the circulation tank 26 is connected to the upper part of the auxiliary tank 78 by a conduit 96 provided with a valve 98 with safety valve, allowing the communication of the gaseous atmospheres of the two circulation tanks 26 and auxiliary 78 .

La partie inférieure du réservoir auxiliaire 78 est raccordée à des moyens 100 de drainage de la solution du réservoir comprenant un conduit 102 muni d'une vanne de drainage 104. Une première extrémité du conduit 102 est reliée au fond du réservoir 78 et la seconde extrémité du conduit 102 est reliée à un collecteur d'effluents liquides, non représenté sur les figures.The lower part of the auxiliary reservoir 78 is connected to means 100 for draining the solution from the reservoir comprising a conduit 102 provided with a drainage valve 104. A first end of the conduit 102 is connected to the bottom of the reservoir 78 and the second end of the conduit 102 is connected to a collector of liquid effluents, not shown in the figures.

On décrira maintenant les différents sous-ensembles d'éléments contaminés de la partie primaire du générateur de vapeur et les étapes du procédé de décontamination selon l'invention que l'on applique à ces sous-ensembles.We will now describe the different subsets of contaminated elements of the primary part of the steam generator and the steps of the decontamination process according to the invention that are applied to these subsets.

On subdivise le faisceau 18 en plusieurs sous-ensembles comportant chacun un nombre sensiblement identique de tubes. Dans l'exemple décrit, chaque sous-ensemble comprend quatre cents tubes environ et la totalité du faisceau comporte environ huit à neuf sous-ensembles de tubes.The bundle 18 is subdivided into several sub-assemblies each comprising a substantially identical number of tubes. In the example described, each sub-assembly comprises approximately four hundred tubes and the entire bundle comprises approximately eight to nine tube sub-assemblies.

On a représenté en trait plein sur la figure 1 une enveloppe imaginaire délimitant un sous-ensemble 106 de tubes voisins.There is shown in solid line in FIG. 1 an imaginary envelope delimiting a sub-assembly 106 of neighboring tubes.

Les tubes sains du sous-ensemble 106 sont raccordés au circuit de décontamination 24 par les moyens de raccordement 34A,34B. Ces moyens de raccordement 34A,34B comprennent des conduits flexibles 108 dont une première extrémité est raccordée au circuit de décontamination 24 et dont la seconde extrémité est raccordée à un collecteur amovible 110, montré plus en détail à la figure 2. Les conduits 108 traversent les orifices délimités par les manchons 23A,23B de la boîte à eau 22.The healthy tubes of the sub-assembly 106 are connected to the decontamination circuit 24 by the connection means 34A, 34B. These connection means 34A, 34B comprise flexible conduits 108, one end of which is connected to the decontamination circuit 24 and the second end of which is connected to a removable collector 110, shown in more detail in FIG. 2. The conduits 108 pass through the orifices delimited by the sleeves 23A, 23B of the water box 22.

Les collecteurs 110 ont une forme générale de cloche et sont plaqués à joint étanche contre la plaque tubulaire 20. Un premier collecteur 110 0estdisposé en regard des extrémités amont et un second collecteur 110 est disposé en regard des extrémités aval des tubes du sous-ensemble 106.The collectors 110 have the general shape of a bell and are pressed against the tube plate with a gasket 20. A first manifold 110 is arranged facing the upstream ends and a second manifold 110 is disposed facing the downstream ends of the tubes of the subassembly 106 .

Sur la figure 2 on a représenté un des collecteurs 110 raccordé au sous-ensemble 106 du faisceau 18.FIG. 2 shows one of the collectors 110 connected to the sub-assembly 106 of the bundle 18.

Ce collecteur 110 est positionné au droit des extrémités ouvertes de tubes sains 18A et éventuellement au droit des extrémités obturées de tubes défectueux 18B. Le collecteur 110 comporte un double bord 112, muni d'un joint d'étanchéité 114, délimitant un canal 116 pour recueillir des fuites éventuelles de la solution circulant à travers le collecteur 110.This manifold 110 is positioned to the right of the open ends of healthy tubes 18A and possibly to the right of the closed ends of defective tubes 18B. The collector 110 has a double edge 112, provided with a seal 114, delimiting a channel 116 for collecting possible leaks of the solution flowing through the collector 110.

Le canal 116 est relié par un orifice 118, ménagé à travers la paroi du collecteur 110, à un conduit 120 de drainage des fuites. Ce conduit 120 est relié à un collecteur d'effluents liquides, non représenté sur les figures.The channel 116 is connected by an orifice 118, formed through the wall of the manifold 110, to a pipe 120 for draining leaks. This conduit 120 is connected to a collector of liquid effluents, not shown in the figures.

Les collecteurs 110 sont positionnés dans les compartiments de la boîte à eau et plaqués contre la plaque tubulaire 20 par des moyens connus; en particulier au moyen d'un robot à bras porteur articulé du type commercialisé sous le nom "ROMEO", disposé dans la boîte à eau.The collectors 110 are positioned in the compartments of the water box and pressed against the tube plate 20 by known means; in particular by means of a robot with an articulated carrying arm of the type sold under the name "ROMEO", placed in the water box.

Le contour du bord 112 d'un collecteur a une forme variable en fonction de la disposition des extrémités des tubes dans la plaque tubulaire 20. Selon que les extrémités des tubes d'un même sous-ensemble sont disposées à l'écart des parois de la boîte à eau ou sont adjacentes à une paroi de la boîte à eau le contour du collecteur 110 a une forme sensiblement carrée ou sensiblement complémentaire au contour de la paroi de la boîte à eau.The contour of the edge 112 of a manifold has a variable shape as a function of the arrangement of the ends of the tubes in the tube plate 20. Depending on whether the ends of the tubes of the same subassembly are arranged away from the walls of the water box or are adjacent to a wall of the water box the outline of the manifold 110 has a substantially square shape or substantially complementary to the outline of the wall of the water box.

On décrira maintenant les étapes de décontamination des tubes sains (non bouchés) du faisceau.We will now describe the decontamination steps of the healthy tubes (not blocked) of the bundle.

Les sous-ensembles 106 de tubes du faisceau sont décontaminés successivement en les raccordant l'un après l'autre au circuit de décontamination 24 au moyen des collecteurs 110 décrits ci-dessus.The subassemblies 106 of tubes of the bundle are successively decontaminated by connecting them one after the other to the decontamination circuit 24 by means of the collectors 110 described above.

On prépare initialement dans le réservoir auxiliaire 78 un volume d'environ 3 m3 de solution de décontamination. Ce volume de solution permet notamment de remplir la totalité des tubes sains du sous-ensemble que l'on veut décontaminer.A volume of approximately 3 m 3 of decontamination solution is initially prepared in the auxiliary tank 78. This volume of solution makes it possible in particular to fill all of the healthy tubes of the subassembly that we want to decontaminate.

La solution de décontamination comprend de l'acide nitrique imposant un pH de la solution compris entre 0,5 et 1, et du nitrate de cérium suivant une proportion de 8 à 10 g/I. En variante, on peut remplacer le sulfate de cérium par du nitrate de cérium.The decontamination solution comprises nitric acid imposing a pH of the solution between 0.5 and 1, and cerium nitrate in a proportion of 8 to 10 g / I. Alternatively, cerium sulphate can be replaced by cerium nitrate.

Une fois la solution préparée, on transfère celle-ci du réservoir auxiliaire 78 au réservoir de circulation 26 au moyen de la pompe de transfert 84, puis on fait subir à chaque sous-ensemble de tubes les étapes suivantes.Once the solution has been prepared, it is transferred from the auxiliary tank 78 to the circulation tank 26 by means of the transfer pump 84, then each sub-assembly of tubes is subjected to the following steps.

On met en circulation la solution dans le circuit de décontamination 24 en boucle fermée au moyen de la pompe de circulation 30. On fait circuler cette solution simultanément à travers tous les tubes sains d'un même sous-ensemble pendant une durée T comprise entre 6 et 24 heures.The solution is put into circulation in the decontamination circuit 24 in a closed loop by means of the circulation pump 30. This solution is circulated simultaneously through all the healthy tubes of the same subassembly for a duration T of between 6 and 24 hours.

Pendant la circulation de la solution, on alimente celle-ci en ozone à l'aide des moyens d'ozonation 25 de manière à maintenir une concentration d'ozone dans la solution d'environ 2,5 ppm.During the circulation of the solution, the latter is supplied with ozone using the ozonization means 25 so as to maintain an ozone concentration in the solution of approximately 2.5 ppm.

La solution de décontamination réagit avec la couche d'oxydes recouvrant la surface interne des tubes et avec la couche superficielle du métal constituant les tubes.The decontamination solution reacts with the oxide layer covering the internal surface of the tubes and with the surface layer of the metal constituting the tubes.

En particulier, le fer de valence Il de la couche d'oxydes est oxydé à la valence III et le chrome de valence III de la couche d'oxydes est oxydé en chrome de valence VI suivant la réaction chimique ci-dessous :

Figure imgb0001
In particular, the valence iron II of the oxide layer is oxidized to valence III and the valence III chromium of the oxide layer is oxidized to chromium of valence VI according to the chemical reaction below:
Figure imgb0001

Le fer de valence III et le chrome de valence VI sont dissous dans la solution. Le cérium de valence III (ions Ce3+) est régénéré en cérium de valence IV (ions Ce4+) par l'ozone suivant la réaction chimique ci-dessous:

Figure imgb0002
The valence III iron and the valence VI chromium are dissolved in the solution. The valence III cerium (Ce3 + ions) is regenerated to valence IV cerium (Ce4 + ions) by ozone according to the chemical reaction below:
Figure imgb0002

La température de la solution est maintenue entre 20 et 30° afin d'assurer une durée de vie suffisante de l'ozone dans la solution lui permettant de régénérer le cérium de valence III.The temperature of the solution is maintained between 20 and 30 ° in order to ensure a sufficient lifetime of the ozone in the solution allowing it to regenerate valence III cerium.

La vitesse de circulation de la solution de décontamination dans les tubes du faisceau est comprise entre 2,5 cm/s et 25 cm/s de manière à éviter que les particules contaminées arrachées à la surface des tubes ne se redéposent dans ces mêmes tubes.The speed of circulation of the decontamination solution in the tubes of the bundle is between 2.5 cm / s and 25 cm / s so as to prevent the contaminated particles torn from the surface of the tubes from being redeposited in these same tubes.

La paroi en Inconel des tubes du faisceau est superficiellement érodée par la solution de décontamination, ce qui produit en particulier des ions Cr6+, Fe3+ et Ni2+.The Inconel wall of the bundle tubes is superficially eroded by the decontamination solution, which in particular produces Cr 6+ , Fe 3+ and Ni2 + ions.

L'érosion de la surface interne des tubes du faisceau est homogénéisée en inversant environ toutes les heures le sens de circulation de la solution de décontamination dans ces tubes, à l'aide des moyens d'inversion 52.The erosion of the internal surface of the bundle tubes is homogenized by reversing the direction of circulation of the decontamination solution in these tubes approximately every hour, using inversion means 52.

Les moyens de filtration 36 permettent de capter une partie des particules arrachées à la partie primaire du générateur de vapeur. De préférence, on utilise un seul filtre 42,44 à la fois. Lorsque la perte de charge à travers le filtre opérationnel devient trop importante, on bascule d'un filtre à un autre au moyen des vannes 46,48 d'isolation des filtres. On peut également, après une certaine durée de mise en circulation de la solution, arrêter la filtration en isolant les filtres du circuit de décontamination 24 et en ouvrant la vanne de dérivation 50.The filtration means 36 make it possible to capture a part of the particles torn from the primary part of the steam generator. Preferably, only one filter 42,44 is used at a time. When the pressure drop across the operational filter becomes too great, it switches from one filter to another by means of valves 46,48 for isolating the filters. It is also possible, after a certain period of circulation of the solution, to stop the filtration by isolating the filters from the decontamination circuit 24 and by opening the bypass valve 50.

A l'issue de l'étape de circulation de la solution de décontamination dans les tubes sains d'un sous-ensemble, on arrête l'injection d'ozone dans la solution et on vidange la totalité du volume de solution contenue dans les tubes du faisceau et dans le circuit de décontamination 24. La solution de décontamination est transférée dans le réservoir auxiliaire 78 au moyen de la pompe 84, pour y être stockée momentanément.At the end of the step of circulating the decontamination solution in the healthy tubes of a sub-assembly, the injection of ozone in the solution is stopped and the entire volume of solution contained in the tubes is emptied of the bundle and in the decontamination circuit 24. The decontamination solution is transferred to the auxiliary tank 78 by means of the pump 84, to be temporarily stored there.

Si la solution de décontamination est altérée, en particulier si la concentration en cérium est devenue trop faible et la concentration en particules contaminées est devenue trop importante, on ouvre la vanne de drainage 104 et la solution est drainée jusqu'à un collecteur d'effluents liquides pour être traitée par la suite suivant des étapes qui seront décrites ultérieurement.If the decontamination solution is altered, in particular if the cerium concentration has become too low and the contaminated particle concentration has become too high, the drainage valve 104 is opened and the solution is drained to an effluent collector liquids to be treated subsequently according to steps which will be described later.

Habituellement, la même solution peut être utilisée pour décontaminer trois sous-ensembles de quatre cents tubes environ. On effectue la décontamination de la totalité des tubes sains du faisceau en huit à neuf passes environ en utilisant approximativement 9 m3 de solution de décontamination.Usually, the same solution can be used to decontaminate three subsets of about four hundred tubes. Decontamination of all of the sound tubes in the bundle is carried out in approximately eight to nine passes using approximately 9 m 3 of decontamination solution.

A l'issue de la vidange de la solution de décontamination, on rince les tubes du sous-ensemble du faisceau avec une solution comprenant de l'eau déminéralisée et de l'eau oxygénée. On introduit la solution de rinçage dans le réservoir de circulation 26 par des moyens connus, non représentés sur les figures, et on fait circuler, au moyen de la pompe de circulation 30, la solution de rinçage à travers les tubes sains du sous-ensemble du faisceau.At the end of the emptying of the decontamination solution, the tubes of the bundle sub-assembly are rinsed with a solution comprising demineralized water and oxygenated water. The rinsing solution is introduced into the circulation tank 26 by known means, not shown in the figures, and the rinsing solution is circulated, by means of the circulation pump 30, through the healthy tubes of the subassembly. of the beam.

L'eau oxygénée H202 réagit avec le cérium résiduel de valence IV et le réduit en cérium de valence III, selon la réaction chimique suivante :

Figure imgb0003
The hydrogen peroxide H 2 0 2 reacts with the residual cerium of valence IV and reduces it to cerium of valence III, according to the following chemical reaction:
Figure imgb0003

A l'issue du rinçage des tubes, on vidange la solution de rinçage par des moyens connus, non représentés sur les figures. La solution de rinçage vidangée est recueillie dans un collecteur d'effluents liquides pour être traitée par la suite suivant des étapes qui seront décrites ultérieurement.After rinsing the tubes, the rinsing solution is drained by known means, not shown in the figures. The drained rinsing solution is collected in a liquid effluent collector for further treatment according to steps which will be described later.

Après avoir décontaminé et rincé les tubes sains d'un sous-ensemble du faisceau, on raccorde le circuit de décontamination 24 à un autre sous-ensemble de tubes auquel on fait subir les étapes de décontamination et de rinçage décrites ci-dessus.After decontaminating and rinsing the healthy tubes of a subset of the bundle, the decontamination circuit 24 is connected to another subset of tubes to which the decontamination and rinsing steps described above are subjected.

Selon l'état d'altération de la solution de décontamination à l'issue de la décontamination du précédent sous-ensemble de tubes, on utilise la même solution de décontamination ou bien on prépare une nouvelle charge de la solution de volume sensiblement identique.Depending on the state of deterioration of the decontamination solution at the end of the decontamination of the previous subset of tubes, the same decontamination solution is used or a new charge of the solution of substantially identical volume is prepared.

On décrira maintenant les étapes de décontamination de la boîte à eau 22 et des tubes défectueux (bouchés) du faisceau.The steps for decontaminating the water box 22 and the defective (blocked) tubes of the bundle will now be described.

Après avoir décontaminé tous les tubes sains du faisceau, on bouche les deux extrémités des tubes sains décontaminés et on perce les bouchons des tubes défectueux non décontaminés. Ainsi, les deux compartiments 22A,22B de la boîte à eau sont reliés par les tubes défectueux débouchés.After decontaminating all the healthy tubes in the bundle, the two ends of the decontaminated healthy tubes are plugged and the caps of the defective tubes not decontaminated are pierced. Thus, the two compartments 22A, 22B of the water box are connected by the defective open tubes.

On a représenté à la figure 3 une installation 10 similaire à celle représentée à la figure 1. Sur la figure 3, les éléments analogues à ceux de la figure 1 ayant des fonctions analogues sont désignés par les mêmes références.There is shown in Figure 3 an installation 10 similar to that shown in Figure 1. In Figure 3, elements similar to those of Figure 1 having similar functions are designated by the same references.

Le circuit de décontamination 24 est raccordé à un sous-ensemble 121 de la partie primaire du générateur de vapeur comprenant les deux compartiments 22A,22B de la boîte à eau et les tubes défectueux débouchés du faisceau. Pour des raisons de clarté, on a représenté, sur la figure 3, un seul tube défectueux 18B.The decontamination circuit 24 is connected to a sub-assembly 121 of the primary part of the steam generator comprising the two compartments 22A, 22B of the water box and the defective tubes opened out from the bundle. For reasons of clarity, there is shown in Figure 3, a single defective tube 18B.

Les manchons 23A,23B de la boîte à eau sont fermés par des plaques 122A,122B munis d'orifices de raccordement aux conduits 108 reliant la boîte à eau au circuit de décontamination 24.The sleeves 23A, 23B of the water box are closed by plates 122A, 122B provided with orifices for connection to the conduits 108 connecting the water box to the decontamination circuit 24.

La décontamination de la boîte à eau et des tubes défectueux est effectuée en faisant circuler à travers ceux-ci un volume de solution de décontamination du type décrit précédemment, suivant des étapes analogues à celles de la décontamination des tubes sains.The decontamination of the water box and defective tubes is carried out by circulating through them a volume of decontamination solution of the type described above, according to steps analogous to those of decontamination of healthy tubes.

Les tubes défectueux présentent un risque de fuite pour des pressions voisines de 150 bars. Par contre, ce risque de fuite est écarté en faisant circuler dans les tubes défectueux la solution de décontamination à une pression sensiblement égale à la pression atmosphérique.Defective tubes present a risk of leakage at pressures in the region of 150 bars. On the other hand, this risk of leakage is eliminated by causing the decontamination solution to circulate in the defective tubes at a pressure substantially equal to atmospheric pressure.

Le volume de solution utilisé est fonction du volume total délimité par les compartiments 22A,22B de la boîte à eau et par les tubes défectueux que l'on doit remplir de solution.The volume of solution used is a function of the total volume delimited by the compartments 22A, 22B of the water box and by the defective tubes which must be filled with solution.

La boîte à eau et les tubes défectueux sont rincés à l'issue de leur décontamination par une solution de rinçage du type décrit précédemment, suivant des étapes analogues à celles du rinçage des tubes sains du faisceau.The water box and the defective tubes are rinsed at the end of their decontamination with a rinsing solution of the type described above, according to steps analogous to those of rinsing the healthy tubes of the bundle.

Les effluents liquides comprenant les solutions de décontamination et de rinçage altérées sont recueillis dans un collecteur, non représenté sur les figures, pour être traités par la suite.The liquid effluents comprising the altered decontamination and rinsing solutions are collected in a collector, not shown in the figures, for further treatment.

On décrira maintenant le traitement des solutions de décontamination et de rinçage altérées après leur utilisation dans les éléments de la partie primaire du générateur de vapeur. Ces solutions, recueillies dans des collecteurs d'effluents liquides, sont soumises aux étapes de traitement suivantes.The treatment of the altered decontamination and rinsing solutions after their use will now be described in the elements of the primary part of the steam generator. These solutions, collected in liquid effluent collectors, are subjected to the following processing steps.

On injecte dans les effluents liquides un agent comprenant de l'eau oxygénée afin de réduire les ions Ce4+ en ions Ce3+ et de stocker ultérieurement le cérium à la valence III.An agent comprising hydrogen peroxide is injected into the liquid effluents in order to reduce the Ce4 + ions to Ce3 + ions and subsequently store the cerium at valence III.

Les effluents liquides sont ensuite neutralisés par injection d'un agent comprenant de la soude, puis transférés dans une installation d'assèchement (non représentée sur les figures) dans laquelle ils sont soumis à une évaporation sous vide.The liquid effluents are then neutralized by injection of an agent comprising soda, then transferred to a drying installation (not shown in the figures) in which they are subjected to evaporation under vacuum.

En variante, les effluents liquides peuvent être asséchés en effectuant, dans un premier temps, une centrifugation des effluents de façon à recueillir les déchets insolubles, et dans un deuxième temps, en effectuant une évaporation sous vide des effluents de façon à recueillir les déchets solubles.As a variant, the liquid effluents can be drained by first carrying out a centrifugation of the effluents so as to collect the insoluble waste, and secondly by carrying out a vacuum evaporation of the effluents so as to collect the soluble waste .

Les effluents asséchés sont confinés dans des enceintes de type connu adaptées pour le stockage de déchets nucléaires de faible et moyenne activité. Ces enceintes peuvent être en béton ou métalliques. Dans l'exemple décrit, la masse totale d'effluents asséchés après décontamination de la totalité du faisceau et de la boîte à eau est d'environ 1500 Kg.The dried effluents are confined in known type enclosures suitable for the storage of low and medium activity nuclear waste. These enclosures can be concrete or metallic. In the example described, the total mass of dried effluents after decontamination of the entire bundle and the water box is approximately 1500 Kg.

Par ailleurs, les filtres colmatés, utilisés dans le circuit de décontamination, sont compactés. Ces filtres permettent de recueillir 50% environ des particules solides arrachées par la solution de décontamination à la partie primaire du générateur de vapeur.Furthermore, the clogged filters used in the decontamination circuit are compacted. These filters collect approximately 50% of the solid particles torn away by the decontamination solution from the primary part of the steam generator.

Dans l'exemple décrit, le volume total des déchets comprenant les filtres compactés, les effluents asséchés et du béton de confinement est d'environ 5 m3.In the example described, the total volume of waste comprising compacted filters, dried effluents and containment concrete is approximately 5 m 3.

Ce volume de déchets est stocké par exemple dans des conteneurs du type commercialisé sous le nom "MOSAÏK".This volume of waste is stored for example in containers of the type sold under the name "MOSAÏK".

Le procédé de décontamination selon l'invention permet d'obtenir un facteur de décontamination, défini par le rapport du champ de rayonnement avant décontamination sur le champ de rayonnement après décontamination, supérieur à 1000 et pouvant attein- dre voire dépasser 15000.The decontamination process according to the invention makes it possible to obtain a decontamination factor, defined by the ratio of the radiation field before decontamination to the radiation field after decontamination, greater than 1000 and which can reach or even exceed 15000.

Outre les constituants déjà cités, la solution de décontamination peut contenir également de l'acide sulfurique. On peut également remplacer l'acide nitrique de la solution par de l'acide sulfurique.In addition to the constituents already mentioned, the decontamination solution may also contain sulfuric acid. You can also replace the nitric acid in the solution with sulfuric acid.

La décontamination des éléments du circuit d'eau primaire est effectuée sans surpression, à une température inférieure à 60°.The decontamination of the elements of the primary water circuit is carried out without overpressure, at a temperature below 60 °.

Le procédé de décontamination selon l'invention permet de décontaminer simultanément un groupe de tubes du faisceau et de réduire à quelques mètres-cube le volume de déchets produit par la décontamination.The decontamination process according to the invention makes it possible to simultaneously decontaminate a group of tubes in the bundle and to reduce the volume of waste produced by the decontamination to a few cubic meters.

Par ailleurs, les effluents produits peuvent être stockés dans des enceintes standard.In addition, the effluents produced can be stored in standard enclosures.

La solution de décontamination que l'on a décrite a une composition adaptée pour décontaminer de façon optimale un faisceau de tubes d'eau primaire en Inconel, mais cette solution peut être également utilisée pour décontaminer des éléments en inox.The decontamination solution that has been described has a composition suitable for optimally decontaminating a bundle of primary water tubes made of Inconel, but this solution can also be used to decontaminate stainless steel elements.

Le procédé de décontamination selon l'invention peut également être appliqué à un générateur de vapeur comprenant un faisceau de tubes d'eau primaire rectilignes. Ces tubes sont reliés à chaque extrémité à une plaque tubulaire et à une boîte à eau. Dans ce cas, un sous-ensemble de tube est raccordé au circuit de décontamination au moyen de collecteurs fixés sur les plaques tubulaires des extrémités du faisceau.The decontamination process according to the invention can also be applied to a steam generator comprising a bundle of straight primary water tubes. These tubes are connected at each end to a tube plate and to a water box. In this case, a tube sub-assembly is connected to the decontamination circuit by means of collectors fixed to the tubular plates of the ends of the bundle.

Claims (24)

1. Procédé de décontamination de la partie primaire d'un générateur de vapeur (12) usagé d'un réacteur nucléaire à eau légère sous pression, cette partie primaire comportant une pluralité d'éléments d'échange de chaleur (18A,18B), le procédé comprenant la mise en contact des surfaces contaminées de la partie primaire avec une solution de décontamination acide comportant du cérium de valence IV sous forme d'ions Ce4+, caractérisé par le fait qu'on subdivise la pluralité d'éléments d'échange de chaleur contamines en plusieurs sous-ensembles (106,121 ) et qu'on fait subir successivement à chaque sous-ensemble (106,121) les étapes de décontamination suivantes : - on fait circuler en circuit fermé un volume prédéterminé de solution de décontamination dans les éléments contaminés (18A,18B) du sous-ensemble (106,121), pendant une durée T, en alimentant continuellement la solution de décontamination en ozone, - on vidange la solution de décontamination, - on fait circuler une solution de rinçage dans le sous-ensemble d'éléments contaminés, - on vidange la solution de rinçage. 1. Method for decontaminating the primary part of a used steam generator (12) of a pressurized light water nuclear reactor, this primary part comprising a plurality of heat exchange elements (18A, 18B), the process dice comprising bringing the contaminated surfaces of the primary part into contact with an acid decontamination solution comprising valence IV cerium in the form of Ce4 + ions, characterized in that the plurality of heat exchange elements is subdivided contaminates in several subsets (106,121) and that each subset (106,121) is subjected successively to the following decontamination steps: - a predetermined volume of decontamination solution is circulated in a closed circuit in the contaminated elements (18A, 18B) of the sub-assembly (106,121), for a period T, by continuously supplying the decontamination solution with ozone, - the decontamination solution is drained, - a rinsing solution is circulated in the subset of contaminated elements, - the rinsing solution is drained. 2. Procédé selon la revendication 1, la partie primaire du générateur de vapeur comportant un faisceau (18) de tubes en U formant des éléments d'échange de chaleur, les tubes ayant leurs deux extrémités raccordées respectivement aux deux compartiments (22A,22B) d'une boîte à eau (22), le faisceau (18) comprenant des tubes sains (18A) dont les extrémités sont ouvertes et des tubes défectueux (18B) dont les extrémités sont obturées par des bouchons, caractérisé par le fait : - qu'on subdivise le faisceau (18) en plusieurs sous-ensembles (106) comportant chacun un nombre sensiblement identique de tubes, - qu'on fait circuler la solution de décontamination successivement dans chaque sous-ensemble (106) de tubes, simultanément dans tous les tubes sains (18A) d'un même sous-ensemble, - et qu'après avoir décontaminé tous les tubes sains (18A) du faisceau, - on bouche les deux extrémités des tubes sains décontaminés, - on perce les bouchons des tubes défectueux (18B) non décontaminés, - on fait circuler la solution de décontamination à travers les deux compartiments (22A,22B) de la boîte à eau et les tubes défectueux (18B). 2. Method according to claim 1, the primary part of the steam generator comprising a bundle (18) of U-shaped tubes forming heat exchange elements, the tubes having their two ends connected respectively to the two compartments (22A, 22B) of a water box (22), the bundle (18) comprising sound tubes (18A) whose ends are open and defective tubes (18B) whose ends are closed by plugs, characterized by the fact: - that the beam (18) is subdivided into several sub-assemblies (106) each comprising a substantially identical number of tubes, - that the decontamination solution is circulated successively in each sub-assembly (106) of tubes, simultaneously in all the healthy tubes (18A) of the same sub-assembly, - and after having decontaminated all the healthy tubes (18A) in the bundle, - the two ends of the healthy decontaminated tubes are plugged, - the plugs of the defective tubes (18B) not decontaminated are drilled, - the decontamination solution is circulated through the two compartments (22A, 22B) of the water box and the defective tubes (18B). 3. Procédé selon la revendication 2, caractérisé en ce que la solution de décontamination comprend de l'acide nitrique imposant un pH de la solution compris entre 0,5 et 1, du nitrate de cérium suivant une proportion de 8 à 10 g/I, et de l'ozone suivant une concentration de 2,5 ppm.3. Method according to claim 2, characterized in that the decontamination solution comprises nitric acid imposing a pH of the solution between 0.5 and 1, cerium nitrate in a proportion of 8 to 10 g / I , and ozone at a concentration of 2.5 ppm. 4. Procédé selon la revendication 2 ou 3, caractérisé en ce que la température de la solution est comprise entre 20 et 30°.4. Method according to claim 2 or 3, characterized in that the temperature of the solution is between 20 and 30 °. 5. Procédé selon l'une quelconque des revendications 2 à 4, caractérisé en ce que chaque sous-ensemble (106) du faisceau comprend environ 400 tubes et en ce que le volume de solution de décontamination est d'environ 3 m3.5. Method according to any one of claims 2 to 4, characterized in that each sub-assembly (106) of the bundle comprises approximately 400 tubes and in that the volume of decontamination solution is approximately 3 m 3 . 6. Procédé selon l'une quelconque des revendications 2 à 5, caractérisé en ce que la durée T de circulation de la solution de décontamination dans chaque sous-ensemble (106) de tubes du faisceau est comprise entre 6 et 24 h.6. Method according to any one of claims 2 to 5, characterized in that the duration T of circulation of the decontamination solution in each sub-assembly (106) of tubes of the bundle is between 6 and 24 h. 7. Procédé selon l'une quelconque des revendications 2 à 6, caractérisé en ce qu'on inverse le sens de circulation de la solution de décontamination dans les tubes du faisceau (18) environ toutes les heures.7. Method according to any one of claims 2 to 6, characterized in that the direction of circulation of the decontamination solution in the bundle tubes (18) is reversed approximately every hour. 8. Procédé selon l'une quelconque des revendications 2 à 7, caractérisé en ce que la vitesse de circulation de la solution de décontamination dans les tubes du faisceau (18) est comprise entre 2,5 cm/s et 25 cm/s.8. Method according to any one of claims 2 to 7, characterized in that the speed of circulation of the decontamination solution in the tubes of the bundle (18) is between 2.5 cm / s and 25 cm / s. 9. Procédé selon l'une quelconque des revendications 1 à 8, caractérisé en ce que la solution de rinçage comprend de l'eau déminéralisée et de l'eau oxygénée.9. Method according to any one of claims 1 to 8, characterized in that the rinsing solution comprises demineralized water and oxygenated water. 10. Procédé selon l'une quelconque des revendications 1 à 9, caractérisé en ce que la solution de décontamination circulant dans les éléments contaminés de la partie primaire est filtrée à travers au moins un filtre (42,44) captant les particules arrachées par la solution à la partie primaire, ceci tant que la perte de charge à travers le filtre (42,44) est inférieure à une valeur prédéterminée.10. Method according to any one of claims 1 to 9, characterized in that the decontamination solution circulating in the contaminated elements of the primary part is filtered through at least one filter (42,44) capturing the particles torn off by the solution in the primary part, this as long as the pressure drop across the filter (42,44) is less than a predetermined value. 11. Procédé selon l'une quelconque des revendications 1 à 10, caractérisé en ce qu'on traite les effluents liquides comprenant la solution de décontamination et la solution de rinçage après leur utilisation dans la partie primaire, en effectuant les étapes suivantes : - on injecte dans les effluents liquides un agent réduisant les ions Ce4+ en ions Ce3+ , - on injecte un agent neutralisant la solution, - on assèche les effluents liquides, - on confine les effluents asséchés dans des enceintes adaptées pour le stockage de déchets de faible et moyenne activité. 11. Method according to any one of claims 1 to 10, characterized in that the liquid effluents comprising the decontamination solution and the rinsing solution are treated after their use in the primary part, by performing the following steps: - an agent reducing the Ce4 + ions into Ce3 + ions is injected into the liquid effluents, - an agent neutralizing the solution is injected, - the liquid effluents are dried, - the dried effluents are confined in enclosures suitable for the storage of low and medium activity waste. 12. Procédé selon la revendication 11, caractérisé en ce que l'agent de réduction des ions Ce4+ en ions Ce3+ comprend de l'eau oxygénée.12. Method according to claim 11, characterized in that the agent for reducing Ce4 + ions to Ce3 + ions comprises hydrogen peroxide. 13. Procédé selon la revendication 11 ou 12, caractérisé en ce que l'agent de neutralisation des effluents comprend de la soude.13. The method of claim 11 or 12, characterized in that the effluent neutralizing agent comprises soda. 14. Procédé selon l'une quelconque des revendications 11 à 13, caractérisé en ce qu'on assèche les effluents liquides par évaporation sous vide.14. Method according to any one of claims 11 to 13, characterized in that the liquid effluents are dried by evaporation under vacuum. 15. Procédé selon l'une quelconque des revendications 11 à 13, caractérisé en ce qu'on assèche les effluents liquides en effectuant, dans un premier temps, une centrifugation des effluents de façon à recueillir les déchets insolubles des effluents, et dans un deuxième temps, en effectuant une évaporation sous vide des effluents de façon à recueillir les déchets solubles.15. Method according to any one of claims 11 to 13, characterized in that the liquid effluents are dried by first carrying out a centrifugation of the effluents so as to collect the insoluble waste from the effluents, and in a second time, by performing a vacuum evaporation of the effluents so as to collect the soluble waste. 16. Installation pour la mise en oeuvre du procédé selon l'une quelconque des revendications 1 à 15, caractérisée en ce qu'elle comporte un circuit de décontamination (24) en boucle fermée comprenant un réservoir de circulation (26) de solution de décontamination, et des moyens (30) de mise en circulation de la solution raccordés entre le réservoir (26) et l'extrémité amont des éléments contaminés (106,121) de la partie primaire du générateur de vapeur, l'installation comprenant de plus des moyens (25) d'ozonation de la solution de décontamination.16. Installation for implementing the method according to any one of claims 1 to 15, characterized in that it comprises a decontamination circuit (24) in closed loop comprising a circulation tank (26) of decontamination solution , and means (30) for circulating the solution connected between the reservoir (26) and the upstream end of the contaminated elements (106,121) of the primary part of the steam generator, the installation further comprising means ( 25) ozonation of the decontamination solution. 17. Installation selon la revendication 16, caractérisée en ce que le circuit de décontamination (24) en boucle fermée comprend des moyens de filtration (36) raccordés entre l'extrémité aval des éléments contaminés (106,121) de la partie primaire et le réservoir de circulation (26).17. Installation according to claim 16, characterized in that the decontamination circuit (24) in closed loop comprises filtration means (36) connected between the downstream end of the contaminated elements (106,121) of the primary part and the reservoir of circulation (26). 18. Installation selon la revendication 16 ou 17, caractérisée en ce qu'elle comporte des moyens (52) d'inversion du sens de circulation de la solution de décontamination dans les éléments contaminés (106,121) de la partie primaire du générateur de vapeur.18. Installation according to claim 16 or 17, characterized in that it comprises means (52) for reversing the direction of circulation of the decontamination solution in the contaminated elements (106,121) of the primary part of the steam generator. 19. Installation selon l'une quelconque des revendications 16 à 18, caractérisé en ce que les moyens (36) de filtration comprennent au moins deux filtres (42,44) raccordés en parallèle, des moyens (46,48) pour isoler chaque filtre du circuit de décontamination et des moyens (50) de dérivation des filtres.19. Installation according to any one of claims 16 to 18, characterized in that the filtration means (36) comprise at least two filters (42,44) connected in parallel, means (46,48) for isolating each filter the decontamination circuit and means (50) for bypassing the filters. 20. Installation selon l'une quelconque des revendications 16 à 19, caractérisée en ce que les moyens d'ozonation (25) comprennent un ozo- neur (58) raccordé à un mélangeur à trompe (64) dont l'extrémité amont est alimentée en solution de décontamination par une pompe (70) raccordée au réservoir de circulation (26) et dont l'extrémité aval est raccordée au réservoir de circulation (26).20. Installation according to any one of claims 16 to 19, characterized in that the ozonization means (25) comprise an ozonator (58) connected to a trumpet mixer (64) whose upstream end is supplied in decontamination solution by a pump (70) connected to the circulation tank (26) and whose downstream end is connected to the circulation tank (26). 21. Installation selon l'une quelconque des revendications 16 à 20, caractérisée en ce qu'elle comprend un réservoir auxiliaire (78), relié au réservoir de circulation (26) par des moyens de transfert de contenu, destiné notamment à la préparation de la solution de décontamination et au stockage intermédiaire de la solution de décontamination après vidange du réservoir de circulation (26).21. Installation according to any one of claims 16 to 20, characterized in that it comprises an auxiliary tank (78), connected to the circulation tank (26) by means of content transfer, intended in particular for the preparation of the decontamination solution and intermediate storage of the decontamination solution after emptying the circulation tank (26). 22. Installation selon l'une quelconque des revendications 16 à 21, caractérisée en ce que le circuit de décontamination (24) est raccordé par des moyens (34A,34B) de raccordement amovibles aux extrémités amont et aval d'un sous-ensemble (106,121) d'éléments contaminés de la partie primaire du générateur de vapeur.22. Installation according to any one of claims 16 to 21, characterized in that the decontamination circuit (24) is connected by means (34A, 34B) of removable connection at the upstream and downstream ends of a sub-assembly ( 106,121) of contaminated elements of the primary part of the steam generator. 23. Installation selon la revendication 22, caractérisée en ce que les moyens de raccordement (34A,34B) comprennent deux collecteurs amovibles (110), raccordant respectivement les extrémités amont et aval d'un sous-ensemble (106) de tubes du faisceau au circuit de décontamination (24), le bord (112) des collecteurs (110) étant plaqué à joint étanche contre une plaque tubulaire (20) de fixation des extrémités des tubes du faisceau, les deux collecteurs (110) étant disposés l'un en regard des extrémités amont et l'autre en regard des extrémités aval des tubes du sous-ensemble (106).23. Installation according to claim 22, characterized in that the connection means (34A, 34B) comprise two removable collectors (110), respectively connecting the upstream and downstream ends of a sub-assembly (106) of bundle tubes to the decontamination circuit (24), the edge (112) of the collectors (110) being pressed against a tubular plate (20) for fixing the ends of the bundle tubes, the two collectors (110) being arranged one at a time facing the upstream ends and the other facing the downstream ends of the tubes of the subassembly (106). 24. Installation selon la revendication 23, caractérisée en ce que les collecteurs (110) de raccordement comportent chacun un double bord (112) délimitant un canal (116) destiné à recueillir des fuites éventuelles de la solution circulant dans le collecteur (110), ce canal étant raccordé à un collecteur de fuites.24. Installation according to claim 23, characterized in that the manifolds (110) for connection each comprise a double edge (112) delimiting a channel (116) intended to collect possible leaks of the solution circulating in the collector (110), this channel being connected to a leak collector.
EP19930400219 1992-02-03 1993-01-28 Process and device for decontaminating a used nuclear steam-generator Expired - Lifetime EP0555127B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9201171 1992-02-03
FR9201171A FR2687005B1 (en) 1992-02-03 1992-02-03 PROCESS AND INSTALLATION FOR DECONTAMINATION OF THE PRIMARY PART OF A STEAM GENERATOR USING A NUCLEAR REACTOR WITH REGULAR WATER UNDER PRESSURE.

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EP0555127A1 true EP0555127A1 (en) 1993-08-11
EP0555127B1 EP0555127B1 (en) 1996-04-24

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EP19930400219 Expired - Lifetime EP0555127B1 (en) 1992-02-03 1993-01-28 Process and device for decontaminating a used nuclear steam-generator

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EP (1) EP0555127B1 (en)
BG (1) BG97390A (en)
CZ (1) CZ11093A3 (en)
DE (1) DE69302290T2 (en)
FR (1) FR2687005B1 (en)
HU (1) HU213081B (en)
SK (1) SK5693A3 (en)

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EP0628969A1 (en) * 1993-06-08 1994-12-14 Framatome Process for restoring the heat exchanger of a nuclear power station
WO1995008173A1 (en) * 1993-09-16 1995-03-23 Framatome Method of dismantling a worn steam generator in a pressurized water nuclear reactor
EP0727243A1 (en) * 1995-02-20 1996-08-21 Commissariat A L'energie Atomique Ozone containing decontamination foam and decontamination methid using this foam
DE19541501A1 (en) * 1995-11-07 1997-05-15 Siemens Ag Method and device for disposing of a nuclear steam generator
WO1999043006A1 (en) * 1998-02-20 1999-08-26 Centre D'etudes De L'energie Nucleaire Method and installation for decontaminating metallic surfaces
CN112481624A (en) * 2019-09-11 2021-03-12 中冶南方工程技术有限公司 Automatic purification device for concentrated acid pipeline of acid regeneration system and use method thereof

Families Citing this family (2)

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FR2711898B1 (en) * 1993-11-05 1995-12-29 Oreal Brush for applying nail polish, or the like.
DE102016122513B3 (en) * 2016-11-22 2017-03-16 Areva Gmbh Method for dismantling a steam generator or heat exchanger, in particular a steam generator or heat exchanger of a nuclear power plant

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FR2547449A1 (en) * 1983-06-07 1984-12-14 Westinghouse Electric Corp METHOD FOR RADIOACTIVE DECONTAMINATION OF A NUCLEAR STEAM GENERATOR, OPERATING BY FLOW CONTROL
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EP0628969A1 (en) * 1993-06-08 1994-12-14 Framatome Process for restoring the heat exchanger of a nuclear power station
FR2706217A1 (en) * 1993-06-08 1994-12-16 Framatome Sa Method for rehabilitating a heat exchanger in a nuclear power plant, in particular a heat exchanger in the auxiliary cooling circuit of a shutdown nuclear reactor.
WO1995008173A1 (en) * 1993-09-16 1995-03-23 Framatome Method of dismantling a worn steam generator in a pressurized water nuclear reactor
FR2710182A1 (en) * 1993-09-16 1995-03-24 Framatome Sa Process for dismantling a used steam generator from a pressurized water nuclear reactor.
EP0727243A1 (en) * 1995-02-20 1996-08-21 Commissariat A L'energie Atomique Ozone containing decontamination foam and decontamination methid using this foam
FR2730641A1 (en) * 1995-02-20 1996-08-23 Commissariat Energie Atomique OZONE DECONTAMINATION FOAM, AND DECONTAMINATION METHOD USING THE SAME
DE19541501A1 (en) * 1995-11-07 1997-05-15 Siemens Ag Method and device for disposing of a nuclear steam generator
WO1999043006A1 (en) * 1998-02-20 1999-08-26 Centre D'etudes De L'energie Nucleaire Method and installation for decontaminating metallic surfaces
BE1011754A3 (en) * 1998-02-20 1999-12-07 En Nucleaire Etabilissement D Method and metal surfaces decontamination installation.
CN112481624A (en) * 2019-09-11 2021-03-12 中冶南方工程技术有限公司 Automatic purification device for concentrated acid pipeline of acid regeneration system and use method thereof
CN112481624B (en) * 2019-09-11 2024-03-22 中冶南方工程技术有限公司 Automatic purification device for concentrated acid pipeline of acid regeneration system and use method of automatic purification device

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Publication number Publication date
DE69302290D1 (en) 1996-05-30
HU9300267D0 (en) 1993-06-28
SK5693A3 (en) 1993-09-09
BG97390A (en) 1994-03-24
HUT66988A (en) 1995-01-30
DE69302290T2 (en) 1996-09-19
EP0555127B1 (en) 1996-04-24
FR2687005A1 (en) 1993-08-06
HU213081B (en) 1997-02-28
FR2687005B1 (en) 1994-10-21
CZ11093A3 (en) 1993-08-11

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