EP0090680A1 - Process for the radioactive decontamination of surfaces - Google Patents
Process for the radioactive decontamination of surfaces Download PDFInfo
- Publication number
- EP0090680A1 EP0090680A1 EP83400370A EP83400370A EP0090680A1 EP 0090680 A1 EP0090680 A1 EP 0090680A1 EP 83400370 A EP83400370 A EP 83400370A EP 83400370 A EP83400370 A EP 83400370A EP 0090680 A1 EP0090680 A1 EP 0090680A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- film
- washing
- hand
- aqueous solution
- liquid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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- 238000000034 method Methods 0.000 title claims abstract description 31
- 230000002285 radioactive effect Effects 0.000 title claims abstract description 20
- 238000005202 decontamination Methods 0.000 title claims abstract description 15
- 230000003588 decontaminative effect Effects 0.000 title claims abstract description 13
- 238000005406 washing Methods 0.000 claims abstract description 32
- 238000000576 coating method Methods 0.000 claims abstract description 28
- 239000011248 coating agent Substances 0.000 claims abstract description 27
- 239000000428 dust Substances 0.000 claims abstract description 24
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 22
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- 239000007864 aqueous solution Substances 0.000 claims abstract description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 14
- 238000001035 drying Methods 0.000 claims abstract description 12
- 238000011109 contamination Methods 0.000 claims abstract description 10
- 239000002966 varnish Substances 0.000 claims description 24
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- 239000011347 resin Substances 0.000 claims description 7
- 229920005989 resin Polymers 0.000 claims description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 5
- 230000008021 deposition Effects 0.000 claims description 5
- 239000003085 diluting agent Substances 0.000 claims description 4
- 230000000694 effects Effects 0.000 claims description 4
- 229920006163 vinyl copolymer Polymers 0.000 claims description 4
- SVONRAPFKPVNKG-UHFFFAOYSA-N 2-ethoxyethyl acetate Chemical compound CCOCCOC(C)=O SVONRAPFKPVNKG-UHFFFAOYSA-N 0.000 claims description 3
- LDHQCZJRKDOVOX-NSCUHMNNSA-N crotonic acid Chemical compound C\C=C\C(O)=O LDHQCZJRKDOVOX-NSCUHMNNSA-N 0.000 claims description 3
- 239000004014 plasticizer Substances 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 3
- LDHQCZJRKDOVOX-UHFFFAOYSA-N trans-crotonic acid Natural products CC=CC(O)=O LDHQCZJRKDOVOX-UHFFFAOYSA-N 0.000 claims description 3
- POAOYUHQDCAZBD-UHFFFAOYSA-N 2-butoxyethanol Chemical compound CCCCOCCO POAOYUHQDCAZBD-UHFFFAOYSA-N 0.000 claims description 2
- MQIUGAXCHLFZKX-UHFFFAOYSA-N Di-n-octyl phthalate Natural products CCCCCCCCOC(=O)C1=CC=CC=C1C(=O)OCCCCCCCC MQIUGAXCHLFZKX-UHFFFAOYSA-N 0.000 claims description 2
- BJQHLKABXJIVAM-UHFFFAOYSA-N bis(2-ethylhexyl) phthalate Chemical compound CCCCC(CC)COC(=O)C1=CC=CC=C1C(=O)OCC(CC)CCCC BJQHLKABXJIVAM-UHFFFAOYSA-N 0.000 claims description 2
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 claims description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims 3
- 229920001577 copolymer Polymers 0.000 claims 1
- 239000000203 mixture Substances 0.000 claims 1
- 229940116351 sebacate Drugs 0.000 claims 1
- CXMXRPHRNRROMY-UHFFFAOYSA-L sebacate(2-) Chemical compound [O-]C(=O)CCCCCCCCC([O-])=O CXMXRPHRNRROMY-UHFFFAOYSA-L 0.000 claims 1
- 239000000853 adhesive Substances 0.000 abstract 1
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- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 239000000499 gel Substances 0.000 description 6
- 239000003973 paint Substances 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
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- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 238000012958 reprocessing Methods 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 230000003750 conditioning effect Effects 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
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- 238000003379 elimination reaction Methods 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
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- 239000011230 binding agent Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000012141 concentrate Substances 0.000 description 2
- 230000002542 deteriorative effect Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 235000019441 ethanol Nutrition 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- 239000002609 medium Substances 0.000 description 2
- 239000004094 surface-active agent Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 241000289669 Erinaceus europaeus Species 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- 240000008042 Zea mays Species 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000002671 adjuvant Substances 0.000 description 1
- 239000000443 aerosol Substances 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 239000012736 aqueous medium Substances 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000009390 chemical decontamination Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
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- 238000009434 installation Methods 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 125000001449 isopropyl group Chemical group [H]C([H])([H])C([H])(*)C([H])([H])[H] 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- 125000002347 octyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
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- 239000000843 powder Substances 0.000 description 1
- 230000003449 preventive effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
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- 239000002915 spent fuel radioactive waste Substances 0.000 description 1
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- 229910052712 strontium Inorganic materials 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 230000009182 swimming Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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Classifications
-
- 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
Definitions
- the present invention relates to radioactive decontamination of polluted surfaces by deposition of contaminating agents, in particular in the form of dust.
- radioactive decontamination (or D.R.A.) consists in ridding the surfaces of the deposited radioactive dust, or at least ridding it sufficiently to no longer represent a danger for the operator.
- the object of the present invention is to allow radioactive decontamination of surfaces while avoiding the drawbacks and handicaps of the usual practice or of known techniques.
- the adherent film-forming coating which is formed beforehand on the surfaces is, on the one hand, insoluble. without marked solubility - in an aqueous medium having a pH at a value between approximately 6 and 8 and, on the other hand, is perfectly soluble in an aqueous solution having a pH at a value situated outside the range of pre- mentioned, and in that said solution is used as a liquid for washing contaminated surfaces.
- the film-forming coating that is formed is insoluble in water, but on the other hand, is perfectly soluble in water added with a base, so as to preferably have a pH at a value d about 9 or more, and this basic aqueous solution is used as a wash for contaminated surfaces.
- dust is therefore meant to qualify, not only powdery solid fragments, but any other substance, in any form whatsoever (droplets, mist, vapor, etc.) capable of being deposited on the surfaces, by example by condensation.
- the invention results, among other things, from the following considerations: it is clear that the dust which is deposited on the surfaces adhere to it with a resistance to removal which depends on the surface condition of the support.
- a "thin layer” is a layer whose thickness is less than 50 A m approximately and, preferably equal or slightly less than 20 ⁇ m.
- an advantageous implementation of the invention consists in using a liquid varnish which is spread over the surfaces to be coated and which, after drying, will form the desired film.
- the "homogeneous" character of the film is really only necessary if the latter is applied in a thin layer, because it is known that it is difficult, if not impossible, to control the porosity of a heterogeneous film (for example example) in a thin layer.
- the coating film is applied in a thin layer, in which case coatings of heterogeneous character (for example the paints themselves) can in all rigor be used according to the method of the invention.
- coatings of heterogeneous character for example the paints themselves
- the choice of a film-forming coating in a homogeneous thin layer constitutes an implementation of the method according to the invention which is both easy and economical, and therefore particularly advantageous.
- a varnish is prepared composed, as basic constituents, of a resin (or binder) formed by a vinyl copolymer of crotonic acid and a solvent formed by ethyl (or isopropyl) alcohol).
- Adjuvants are then added in an adequate quantity to improve the quality of the varnish, namely: a diluent, such as ethyl glycol acetate (or butyl glycol) as well as a plasticizer, for example phthalate dioctyl (or octyl cebacate)
- a varnish solution comprising, by weight, Approximately 25% of vinyl copolymer of crotonic acid, between 2.5 and 3% of dioctyl phthalate, the remainder being constituted by the solvent (ethyl alcohol) and the diluent (ethyl glycol acetate).
- the diluent and the plasticizer are determined so that after drying, the resin (or "dry extract") is capable of forming, in a single layer and without sagging or the like, a film of minimum thickness offering good protection.
- the varnish once ready, is applied to clean and dry surfaces, preferably by spraying with a pneumatic gun.
- the varnish After drying, the varnish forms a continuous film, without breaking or cracking and with a thickness of about fifteen microns on average.
- the above-mentioned value represents a practical and economic optimum, but by no means a technical minimum necessary for the execution of the method according to the invention.
- the equipment after proper drying of the varnish, the equipment, the surfaces of which are thus coated, can be put into service, and in particular be exposed to an atmosphere having in suspension the radioactive dust.
- the protective resin film will slowly load into dust without, however, deteriorating or deteriorating, since the vinyl copolymer which constitutes it, being insoluble in the usual solvents as well as in any aqueous solution at pH below about 8, therefore remains perfectly stable and chemically inert in contact with the atmosphere prevailing in the enclosures and cells where the material is used.
- a basic aqueous solution having a pH preferably at least one point above the solubility threshold of the resin.
- aqueous solution is prepared containing 3 g of sodium hydroxide (Na OH) per liter of water, corresponding to a pH close to 9.
- a suitable surfactant can be added to give the washing solution an additional detergent action.
- this solution is then projected onto the contaminated surfaces using injection lances.
- the varnish dissolves easily, carrying with it the contaminating dust which had settled there.
- a period of washing which can range from half an hour to an hour and a half approximately depending on the extent of the initial contamination of the surfaces, the latter are completely cleared radioactive dust.
- a new layer of varnish is applied to them and the equipment is ready for a new start-up.
- the dissolution of the varnish in the soda solution has the advantage of being irreversible, that is to say that the varnish, once dissolved, no longer regains its initial film-forming quality, but occurs after water evaporation, in powder form.
- This absence of gelification in the washing solution constitutes an additional advantage for the final conditioning of the contaminated effluents.
- the solid residue which appears in small quantity on these surfaces can be easily removed by simple dry cleaning, for example by light brushing.
- the method according to the invention has many other advantages and advantages, some of which are now mentioned.
- the state of the surface to be decontaminated is perfectly known, given that it consists of the film-forming coating which is completely controlled both in application and in stability and which is can, at the desired time, easily dissolve and eliminate whatever the nature, the quantity, the distribution and especially the adhesion of the contaminants which are deposited there.
- the quantity of base to be used (for example soda) is less important than that consumed with the usual practice because, not only of the less quantity of washing necessary but also because the concentration of liquid sodium hydroxide can be adjusted to its minimum value, sufficient to slightly exceed the pH threshold above which the coating applied is perfectly soluble.
- the residual concentrate composed of the dry extract of the varnish (the resin), soda and contaminants, can be easily calcined and thus waste of a minimum volume is obtained.
- varnish additives having electrostatic properties which oppose by their effects the tendency to deposit dust and thus making it possible to modify in the direction desired the amount of dust deposited, or even their geographic distribution on the surfaces.
- constituent elements of the film-forming material to be applied in particular varnish when this type of product is used, can vary within a wide range of possibilities, among which the skilled person will be able to make a choice according to his wishes or necessities.
- the process according to the invention can be carried out with washing of the contaminated surfaces with a solution not only basic but also with an acid solution.
- temporary film-forming coating will be made accordingly so that it can be removed by dissolving in an acidic washing solution, preferably at a pH of at least 5.
- the washing operation carried out for this purpose can be carried out, not only by jets with a lance, as is imperatively the case in current current practice, but also - (although less easy to implement and may be generally less effective) - statically, in a "dead bath", by immersion in a swimming pool.
- the field of application of the method according to the invention extends beyond the reprocessing of irradiated fuels and in fact relates to radioactive decontamination in general, within the limit however where the contamination originates from the deposition on surfaces, or other supports, of irradiated dust or condensables .
- the method according to the invention can find civil applications, for example in equipment and installations located in sensitive areas in nuclear power plants, or for laboratory devices on which solutions loaded with radioactive particles can flow during manipulations.
- the method according to the invention can also find military applications, in particular of the same type as civil applications for sensitive areas (for example in nuclear-powered submarines) or for various military materials which may be contaminated. by dust from a nuclear explosion, during atmospheric tests, etc.
Landscapes
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Food Science & Technology (AREA)
- Physics & Mathematics (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
Description
La présente invention concerne la décontamination radioactive des surfaces polluées par dépôt d'agents contaminants, notamment sous forme de poussières.The present invention relates to radioactive decontamination of polluted surfaces by deposition of contaminating agents, in particular in the form of dust.
Dans l'industrie nucléaire en particulier, et plus spécialement dans le secteur du retraitement des combustibles irradiés, les diverses manipulations que l'on effectue sur ces derniers, (transferts, opérations d'usinage, de tronçonnage ou de séparation des combustibles de leur gaine de conditionnement, etc...) provoquent la formation de poussières ou d'aérosols présentant une certaine radioactivité.In the nuclear industry in particular, and more particularly in the sector of reprocessing of irradiated fuels, the various manipulations that are carried out on the latter, (transfers, machining operations, cutting-off or separation of fuels from their cladding packaging, etc.) cause the formation of dust or aerosols with a certain radioactivity.
Ces particules radioactives extrêmement ténues, de diamètre souvent inférieur au micron, se mettent en suspension dans l'atmosphère des locaux spéciaux -"dites cellules chaudes"- où s'effectuent les opérations précitées et se déposent naturellement sur les surfaces offertes, et notamment, sur les surfaces des matériels, machines et outillages présents dans ces cellules.These extremely fine radioactive particles, often less than a micron in diameter, are suspended in the atmosphere of special premises - "so-called hot cells" - where the above operations are carried out and are naturally deposited on the surfaces offered, and in particular, on the surfaces of the materials, machines and tools present in these cells.
Pour des raisons de maintenance ou de réparation, il est nécessaire de temps à autre de sortir le matériel des cellules chaudes afin de pouvoir intervenir dessus en atelier normal et "à mains nues".For maintenance or repair reasons, it is necessary from time to time to remove the material from the hot cells in order to be able to work on it in a normal workshop and "with bare hands".
Il est toutefois impératif de désactiver préalablement les surfaces polluées de ce matériel.It is however imperative to deactivate the polluted surfaces of this material beforehand.
Cette opération, appelée décontamination radioactive, (ou D.R.A.) çonsiste à débarrasser les surfaces des poussières radioactives déposées, ou du moins à les en débarrasser suffisamment pour ne plus représenter un danger pour l'opérateur.This operation, called radioactive decontamination, (or D.R.A.) consists in ridding the surfaces of the deposited radioactive dust, or at least ridding it sufficiently to no longer represent a danger for the operator.
A cette fin, on procède le plus souvent à l'heure actuelle à un lavage des surfaces contaminées avec une solution détergente appropriée, projetée à chaud en jets à haute pression. On vérifie ensuite, avec un compteur à scintillations, la valeur de la radioactivité résiduelle et on répète l'opération autant de fois qu'il est nécessaire pour amener cette valeur en-dessous d'un seuil acceptable.To this end, most often at present, washing of the contaminated surfaces with an appropriate detergent solution, sprayed hot in high pressure jets. The value of the residual radioactivity is then checked with a scintillation counter and the operation is repeated as many times as necessary to bring this value below an acceptable threshold.
Le résultat de cette méthode de décontamination est souvent aléatoire:on ne peut préjuger de son efficacité, ni de sa durée, d'autant que les poussières de certains métaux, comme le caesium, le ruthénium, ou le strontium, émettent des radiations particulièrement dangereuses. Leur élimination est de surcroît très difficile par cette technique, car il s'agit de métaux relativement mous, qui collent aux parois et qui ont même tendance à y adhérer fortement par écrasement sous l'action mécanique des jets de lavage.The result of this decontamination method is often random: we cannot prejudge its effectiveness or its duration, especially since the dust of certain metals, such as caesium, Ruthenium, or strontium, emits particularly dangerous radiation. Their elimination is moreover very difficult by this technique, since they are relatively soft metals, which stick to the walls and which even tend to adhere strongly to them by crushing under the mechanical action of the washing jets.
On comprend, dans ces conditions, que la méthode de décontamination, telle que pratiquée jusqu'ici, peut-être difficilement compatible avec les contraintes économiques propres aux installations à caractère industriel, où l'indisponibilité d'un appareillage sur une durée indéterminée peut bloquer un processus ou une chaîne de retraitement.It is understandable, under these conditions, that the decontamination method, as practiced so far, may be difficult to reconcile with the economic constraints specific to industrial facilities, where the unavailability of equipment for an indefinite period can block a reprocessing process or chain.
Pour remédier à ces difficultés, on a déjà songé à recouvrir dans un premier temps les surfaces polluées par un gel décontaminant susceptible de réagir avec les éléments radioactifs présents sur les surfaces. Après une durée suffisante pour permettre la réaction, on élimine le gel, soit par lavage à l'eau, dans le cas de gels peu séchants (composés glycérophtaliques ou glycérophosphoriques), soit par voie mécanique dans le cas de gels pelables (composés cellulosiques).To remedy these difficulties, consideration has already been given to first covering the polluted surfaces with a decontaminating gel capable of reacting with the radioactive elements present on the surfaces. After a sufficient time to allow the reaction, the gel is removed, either by washing with water, in the case of slightly drying gels (glycerophthalic or glycerophosphoric compounds), or mechanically in the case of peelable gels (cellulosic compounds) .
Ces techniques, décritent notamment dans la demande de brevet français 2380624 -CEA et dans le brevet français 1303673 -UKAEA, présentent entre autres l'avantage de limiter les quantités de réactifs nécessaires pour assurer la décontamination.These techniques, described in particular in French patent application 2380624 -CEA and in French patent 1303673 -UKAEA, have among other advantages the advantage of limiting the quantities of reagents necessary to ensure decontamination.
Elles imposent toutefois un temps d'attente parfois important avant de pouvoir éliminer le gel. De plus, il faut veuiller à ce que le igel réagisse uniquement avec les particules radioactives pour,, ne pas provoquer une corrosion des surfaces.However, they sometimes require a long waiting time before the gel can be removed. In addition, care should be taken to ensure that the igel reacts only with radioactive particles so as not to cause corrosion of the surfaces.
Il a également été proposé de protéger les surfaces en les recouvrant préalablement à leur contamination par une matière filmogène bien soluble dans l'eau. Après contamination, on élimine le film pollué par dissolution par simple lavage à l'eau.It has also been proposed to protect the surfaces by covering them before their contamination by a film-forming material which is well soluble in water. After contamination, the polluted film is removed by dissolution by simple washing with water.
Cette technique de type préventif, décrite par exemple dans le brevet US 2877131 -OVERHOLT, semble à priori très attrayante puisqu'elle permet en principe d'éviter les handicaps prémentionnés des post-traitements par gels (temps d'attente, réactifs sélectifs).This preventive type technique, described for example in US Pat. No. 2,877,131 -OVERHOLT, seems a priori very attractive since it in principle makes it possible to avoid the aforementioned handicaps of post-treatments with gels (waiting times, selective reagents).
Toutefois, on est en droit de craindre des inconvénients liés à une dégradation plus ou moins rapide du revêtement au contact de l'atmosphère toujours humide des cellules chaudes.However, we are entitled to fear disadvantages linked to a more or less rapid degradation of the coating on contact of the always humid atmosphere of the hot cells.
Le but de la présente invention est de permettre la décontamination radioactive des surfaces en évitant les inconvénients et handicaps de la pratique habituelle ou des techniques connues.The object of the present invention is to allow radioactive decontamination of surfaces while avoiding the drawbacks and handicaps of the usual practice or of known techniques.
A cet effet, l'invention a pour objet un procédé pour la décontamination radioactive des surfaces polluées par dépôt d'agents contaminants, notamment sous forme de poussières en suspension dans l'atmosphère à laquelle ont été exposées ces surfaces, procédé caractérisé en ce que:
- - avant d'exposer lesdites surfaces à l'atmosphère contenant les agents contaminants, on leur applique une matière filmogène qui après séchage forme un revêtement adhérent présentant, d'une part, une bonne stabilité et aucune altérabilité marquée dans l'atmosphère contenant les agents contaminants et d'autre part, une bonne solubilité dans au moins un solvant pouvant constituer un liquide de lavage desdites surfaces,
- - et, après contamination de ces surfaces par dépôt des agents contaminants, on effectue, à l'aide dudit liquide de lavave, un lavage des surfaces de manière à éliminer par dissolution le revêtement filmogène suffisamment pour qu'il entraîne avec lui les agents contaminants.
- - before exposing said surfaces to the atmosphere containing the contaminating agents, a film-forming material is applied to them which, after drying, forms an adherent coating having, on the one hand, good stability and no marked alterability in the atmosphere containing the agents contaminants and on the other hand, good solubility in at least one solvent which can constitute a washing liquid for said surfaces,
- - And, after contamination of these surfaces by deposition of the contaminating agents, the surfaces are washed using said lava liquid so as to dissolve the film-forming coating sufficiently so that it carries with it the contaminating agents .
Conformément à une mise en oeuvre de l'invention, le revêtement filmogène adhérent que l'on forme préalablement sur les surfaces, est, d'une part, insoluble -i.e. sans solubilité marquée- dans un milieu aqueux ayant un pH à une valeur comprise entre 6 et 8 environ et, d'autre-part, est parfaitement soluble dans une solution aqueuse présentant un pH à une valeur située en dehors du domaine de valeurs pré- mentionné, et en ce qu'on utilise ladite solution comme liquide de lavage des surfaces contaminées.In accordance with an implementation of the invention, the adherent film-forming coating which is formed beforehand on the surfaces is, on the one hand, insoluble. without marked solubility - in an aqueous medium having a pH at a value between approximately 6 and 8 and, on the other hand, is perfectly soluble in an aqueous solution having a pH at a value situated outside the range of pre- mentioned, and in that said solution is used as a liquid for washing contaminated surfaces.
Dans une variante préférée, le revêtement filmogène que l'on forme est insoluble dans l'eau, mais par contre, est parfaitement soluble dans de l'eau additionnée d'une base, de manière à présenter de préférence un pH à une valeur d'environ 9 ou plus, et on utilise cette solution aqueuse basique comme liquide de lavage des surfaces contaminées.In a preferred variant, the film-forming coating that is formed is insoluble in water, but on the other hand, is perfectly soluble in water added with a base, so as to preferably have a pH at a value d about 9 or more, and this basic aqueous solution is used as a wash for contaminated surfaces.
Comme on l'aura sans doute déjà compris, l'invention consiste, dans ses caractéristiques essentielles:
- - d'une part, à conditionner les surfaces préalablement à leur exposition aux agents contaminants en les revêtant d'un film temporaire sur lequel se fixent les poussières radioactives et qui est ensuite éliminé par dissolution dans un solvant de lavage, entraînant ainsi avec lui les poussières radioactives;
- - d'autre part, à opter pour un revêtement filmogène qui n'a nul besoin de contenir des réactifs décontaminants et qui, surtout, n'est pas soluble dans l'eau (donc insensible à l'atmosphère humide des -cellules chaudes) mais par contre parfaitement soluble dans une solution acide ou, de préférence alcaline (actipn détergente supplémentaire).
- - on the one hand, condition the surfaces prior to their exposure to contaminating agents by coating them with a temporary film on which the radioactive dust is fixed and which is then eliminated by dissolution in a washing solvent, thus bringing with it the radioactive dust;
- - on the other hand, to opt for a film-forming coating which has no need to contain decontaminating reagents and which, above all, is not soluble in water (therefore insensitive to the humid atmosphere of hot cells) but on the other hand perfectly soluble in an acidic solution, preferably alkaline (additional detergent actipn).
Bien entendu, l'invention procure l'élimination, non seulement des poussières en tant que telles, mais également de toute particule, molécule, ou toute substance et composé condensables. Par "poussière", on entend donc qualifier, non seulement des fragments solides pulvérulents, mais toute autre substance, sous quelque forme que ce soit (goutelettes, brouillard, vapeur, etc...) susceptible, de se déposer sur les surfaces, par exemple par condensation.Of course, the invention provides the elimination, not only of the dust as such, but also of any particle, molecule, or any condensable substance and compound. By "dust" is therefore meant to qualify, not only powdery solid fragments, but any other substance, in any form whatsoever (droplets, mist, vapor, etc.) capable of being deposited on the surfaces, by example by condensation.
L'invention résulte, entre autres, des considérations suivantes: il est clair que les poussières qui se déposent sur les surfaces y adhèrent avec une résistance à l'enlèvement qui dépend de l'état de surface du support.The invention results, among other things, from the following considerations: it is clear that the dust which is deposited on the surfaces adhere to it with a resistance to removal which depends on the surface condition of the support.
Mis à part un poli de qualité "miroir", toutes les surfaces des objets usuels, quelles soient peintes ou non, sont constituées, à l'échelle du microscope, d'une succession de cavités et de pics qui, non seulement augmentent la surface de réception, mais intensifient l'effet de rétention des poussières qui s'y sont déposées.Aside from a "mirror" quality polish, all surfaces of everyday objects, whether painted or not, are made up, on the microscope scale, of a succession of cavities and peaks which not only increase the surface but intensify the retention effect of the dust deposited therein.
En outre, si ces surfaces sont peintes, les phénomènes précédents sont plus accusés encore, car les peintures généralement utilisées, en raison de leur structure hétérogène, comportent une micro- porosité qui les rendent aptes à recevoir à l'intérieur même de la masse des contaminations importantes.In addition, if these surfaces are painted, the above phenomena are even more pronounced, because the paints generally used, because of their heterogeneous structure, have a micro-porosity which make them capable of receiving inside the mass of significant contamination.
Il s'ensuit que même un lavage par jets haute pression avec des solutions détergentes reste insuffisant à lui seul pour éliminer les poussières contaminantes, et ceci principalement, comme on l'a dit, lorsqu'il s'agit de poussières de métaux mous.It follows that even washing with high pressure jets with detergent solutions alone is insufficient to remove contaminating dust, and this mainly, as we said, when it comes to soft metal dust.
Sur la base de considérations de ce type, l'inventeur a été amené à observer que le lavage des surfaces peut devenir pleinement efficace dans la mesure où il est combiné à un conditionnement de ces surfaces préalablement à toute contamination, par un revêtement filmogène adhérent, facilement éliminable par un lavage ultérieur adéquat à l'aide d'un liquide autre que de l'eau.Based on such considerations, the inventor was led to observe that the washing of surfaces can become fully effective insofar as it is combined with conditioning of these surfaces before any contamination, by an adherent film-forming coating, easily removable by an appropriate subsequent washing using a liquid other than water.
Le procédé selon l'invention, tel qu'il vient d'être explicité, est opérationnel de façon optimale lorsque le revêtement utilisé se présente sous la forme d'un film en couche mince, continu et homogène. Pour fixer les idées, on admettra qu'une "couche mince" est une couche dont l'épaisseur est inférieure à 50 Am environ et, de préférence égale ou légèrement inférieure à 20 ¡m.The method according to the invention, as just explained, is optimally operational when the coating used is in the form of a thin, continuous and homogeneous film. To fix the ideas, we will admit that a "thin layer" is a layer whose thickness is less than 50 A m approximately and, preferably equal or slightly less than 20 ¡m.
A cet égard, une mise en oeuvre avantageuse de l'invention consiste à utiliser un vernis liquide que l'on étale sur les surfaces à revêtir et qui, après séchage, formera le film recherché.In this regard, an advantageous implementation of the invention consists in using a liquid varnish which is spread over the surfaces to be coated and which, after drying, will form the desired film.
Il doit être souligné que le caractère "homogène" du film n'est vraiment nécessaire que si ce dernier est appliqué en couche mince, car on sait qu'il est difficile, voire impossible, de contrôler la porosité d'un film hétérogène (par exemple une peinture) en couche mince.It should be emphasized that the "homogeneous" character of the film is really only necessary if the latter is applied in a thin layer, because it is known that it is difficult, if not impossible, to control the porosity of a heterogeneous film (for example example) in a thin layer.
D'un autre côté, il n'est pas impératif non plus que le film de revêtement soit appliqué en couche mince, auquel cas des revêtements de caractère hétérogène (par exemple les peintures elles-mêmes) peuvent en toute rigueur être utilisés selon le procédé de l'invention. Il reste néanmoins, que le choix d'un revêtement filmogène en couche mince homogène (un vernis notamment) constitue une mise en oeuvre du procédé selon l'invention qui est à la fois aisée et économique, donc particulièrement avantageuse.On the other hand, it is not imperative either that the coating film is applied in a thin layer, in which case coatings of heterogeneous character (for example the paints themselves) can in all rigor be used according to the method of the invention. The fact remains, however, that the choice of a film-forming coating in a homogeneous thin layer (in particular a varnish) constitutes an implementation of the method according to the invention which is both easy and economical, and therefore particularly advantageous.
Ceci,étant, on va maintenant décrire, à titre purement illustratif, un exemple de mise en oeuvre de l'invention à l'aide d'un vernis en vue de la décontamination radioactive dans le secteur industriel du retraitement des combustibles irradiés.That said, we will now describe, purely by way of illustration, an example of implementation of the invention using a varnish for radioactive decontamination in the industrial sector of reprocessing of spent fuel.
On prépare un vernis composé, en tant que constituants de base, d'une résine (ou liant) formée par un copolymère vinylique de l'acide crotonique et d'un solvant formé par de l'alcool éthylique (ou isopropylique)). On ajoute ensuite, en quantité adéquate, des adjuvants pour parfaire la qualité du vernis, à savoir: un diluant, tel qu'un acétate d'éthyl-glycol (ou de butyl-glycol) ainsi qu'un plastifiant, par exemple du phtalate de dioctyle (ou du cébacate d'octyle)A varnish is prepared composed, as basic constituents, of a resin (or binder) formed by a vinyl copolymer of crotonic acid and a solvent formed by ethyl (or isopropyl) alcohol). Adjuvants are then added in an adequate quantity to improve the quality of the varnish, namely: a diluent, such as ethyl glycol acetate (or butyl glycol) as well as a plasticizer, for example phthalate dioctyl (or octyl cebacate)
On réalise ainsi une solution de vernis comprenant, en poids, 25% environ de copolymère vinylique d'acide crotonique, entre 2.5 et 3% environ de phtalate de dioctyle, le reste étant constitué par le solvant (l'acool éthylique) et le diluant (l'acétate d'éthyl-glycol).A varnish solution is thus produced comprising, by weight, Approximately 25% of vinyl copolymer of crotonic acid, between 2.5 and 3% of dioctyl phthalate, the remainder being constituted by the solvent (ethyl alcohol) and the diluent (ethyl glycol acetate).
Bien entendu, les constituants indiqués ci-dessus, ne sont pas limitatifs et leur nature, comme leurs proportions respectives restent de la compétence de l'homme de métier dans le domaine des peintures et vernis destinés au revêtement des surfaces.Of course, the constituents indicated above are not limiting and their nature, like their respective proportions, remains within the competence of those skilled in the art in the field of paints and varnishes intended for coating surfaces.
En particulier, le diluant et le plastitiant sont déterminés de façon qu'après séchage, la résine (ou "extrait sec") soit capable de former, en une seule couche et sans coulure ou autre, un film d'épaisseur minimale offrant une bonne protection.In particular, the diluent and the plasticizer are determined so that after drying, the resin (or "dry extract") is capable of forming, in a single layer and without sagging or the like, a film of minimum thickness offering good protection.
Il doit être souligné à cet égard que la mise en oeuvre de l'invention ne pose aucun problème non maîtrisé, car toutes les indications et prescriptions qui précèdent font partie intégrante des règles de l'art dans le domaine des peintures et vernis.It should be emphasized in this regard that the implementation of the invention poses no uncontrolled problem, since all the above indications and prescriptions are an integral part of the rules of the art in the field of paints and varnishes.
Le vernis, une fois prêt, est appliqué sur les surfaces propres et sèches, de préférence par pulvérisation au pistolet pneumatique.The varnish, once ready, is applied to clean and dry surfaces, preferably by spraying with a pneumatic gun.
Après séchage, le vernis forme un film continu, sans rupture ni craquelure et d'une épaisseur d'une quinzaine de microns environ en moyenne.After drying, the varnish forms a continuous film, without breaking or cracking and with a thickness of about fifteen microns on average.
Il présente une bonne adhérence sur la plupart des surfaces à traiter (métaux nus, peintures, bétons, matières plastiques, etc...). De plus, il est insoluble dans l'eau ou dans toute solution aqueuse à pH inférieur à 8.It has good adhesion to most surfaces to be treated (bare metals, paints, concretes, plastics, etc.). In addition, it is insoluble in water or in any aqueous solution at a pH below 8.
On rappelle, qu'en ce qui concerne l'épaisseur du film, la valeur prémentionnée représente un optimum pratique et économique, mais nullement un minimum technique nécessaire à l'exécution du procédé selon l'invention.It will be recalled that, as regards the thickness of the film, the above-mentioned value represents a practical and economic optimum, but by no means a technical minimum necessary for the execution of the method according to the invention.
En effet, pour assurer une protection suffisante, on pourrait se limiter, en principe, à une épaisseur de quelques microns seulement (par exemple 5 µm correspondant à un film formé par quelques nappes monomoléculaires superposées de résine. Ceci est tout à fait possible avec les moyens technologiques actuellement disponibles et pourrait fort bien être appliqué dans le cas de surfaces planes.In fact, to ensure sufficient protection, one could limit oneself, in principle, to a thickness of only a few microns (for example 5 μm corresponding to a film formed by a few monolayers layers superimposed on resin. This is entirely possible with technological means currently available and could very well be applied in the case of flat surfaces.
Mais si les surfaces présentent des angles vifs, on aboutit à ces endroits à une maigreur du film (environ 1-2)xm) qui serait alors inapte à assurer la protection recherchée.But if the surfaces have sharp angles, we end up in these places with a thinness of the film (approximately 1-2) xm) which would then be incapable of ensuring the desired protection.
Par conséquent, si on veut obtenir un minimum d'épaisseur sur les angles vifs, il faut, ou bien, appliquer un film d'épaisseur supérieure ailleurs, par exemple 15 µm environ, comme indiqué précédemment, ou procéder à un rechargement de vernis sur les angles vifs, ce qui, en général, serait sans intérêt sur le plan économique.Consequently, if we want to obtain a minimum thickness on the sharp corners, it is necessary either to apply a film of greater thickness elsewhere, for example approximately 15 μm, as indicated previously, or to proceed with a reloading of varnish on sharp angles, which, in general, would be of no economic interest.
Ceci dit, après séchage convenable du vernis, le matériel, dont les surfaces sont ainsi revêtues, peut être mis en service, et notamment être exposé à une atmosphère ayant en suspension les poussières radioactives.That said, after proper drying of the varnish, the equipment, the surfaces of which are thus coated, can be put into service, and in particular be exposed to an atmosphere having in suspension the radioactive dust.
Le film protecteur de résine va lentement se charger en poussières sans toutefois s'altérer ou se détériorer, puisque le copolymère vinylique qui le constitue, étant insoluble dans les solvants usuels ainsi que dans toute solution aqueuse à pH inférieur à 8 environ, demeure donc parfaitement stable et chimiquement inerte au contact de l'atmosphère régnant dans les enceintes et cellules où le matériel est utilisé.The protective resin film will slowly load into dust without, however, deteriorating or deteriorating, since the vinyl copolymer which constitutes it, being insoluble in the usual solvents as well as in any aqueous solution at pH below about 8, therefore remains perfectly stable and chemically inert in contact with the atmosphere prevailing in the enclosures and cells where the material is used.
On précise, au besoin, que l'emploi du qualificatif "insoluble" pour caractériser le comportement d'une substance dans, ou au contact d'un milieu quelconque, signifie nullement une absence totale de dissolution dans ce milieu, mais plus exactement une dissolution à un degré non significatif ou non détectable par les moyens d'analyse habituels.It is specified, if necessary, that the use of the qualifier "insoluble" to characterize the behavior of a substance in, or in contact with any medium, in no way signifies a total absence of dissolution in this medium, but more exactly a dissolution to a degree not significant or not detectable by the usual means of analysis.
Pour procéder ultérieurement à la décontamination des surfaces, on commence par préparer une solution aqueuse basique ayant un pH de préférence un point au moins au-dessus du seuil de solubilité de la résine. Par exemple, on prépare une solution aqueuse contenant 3 g d'hydroxyde de sodium (Na OH) par litre d'eau, correspondant à un pH proche de 9. Avantageusement, on peut ajouter un agent tensio--actif approprié pour conférer à la solution de lavage une action détergente supplémentaire.In order to subsequently decontaminate the surfaces, one begins by preparing a basic aqueous solution having a pH preferably at least one point above the solubility threshold of the resin. For example, an aqueous solution is prepared containing 3 g of sodium hydroxide (Na OH) per liter of water, corresponding to a pH close to 9. Advantageously, a suitable surfactant can be added to give the washing solution an additional detergent action.
On projette alors, selon la pratique connue, cette solution sur les surfaces contaminées à l'aide de lances d'injection. Au contact de la solution alcaline, le vernis se dissout facilement, entraînant avec lui les poussières contaminantes qui s'y étaient déposées. Au bout d'une durée de lavage, pouvant aller d'une demi-heure à une heure et demi environ selon l'importance de la contamination initiale des surfaces, ces dernières sont complètement débarrassées poussières radioactives. Après séchage et nettoyage, on leur applique une nouvelle couche de vernis et le matériel est prêt pour une nouvelle mise en service.In accordance with known practice, this solution is then projected onto the contaminated surfaces using injection lances. On contact with the alkaline solution, the varnish dissolves easily, carrying with it the contaminating dust which had settled there. After a period of washing, which can range from half an hour to an hour and a half approximately depending on the extent of the initial contamination of the surfaces, the latter are completely cleared radioactive dust. After drying and cleaning, a new layer of varnish is applied to them and the equipment is ready for a new start-up.
Il doit être souligné que la dissolution du vernis dans la solution sodée présente l'avantage d'être irréversible, c'est-à-dire que le vernis, une fois dissout, ne retrouve plus sa qualité filmogène initiale, mais se présente, après évaporation de l'eau, sous forme pulvérulente. Cette absence de gelification dans la solution de lavage constitue un avantage supplémentaire pour le conditionnement final des effluents contaminés. Par ailleurs, après séchage des surfaces décontaminées, le résidu solide qui apparaît en faible quantité sur ces surfaces peut être facilement éliminé par simple nettoyage à sec, par exemple par brossage léger.It should be emphasized that the dissolution of the varnish in the soda solution has the advantage of being irreversible, that is to say that the varnish, once dissolved, no longer regains its initial film-forming quality, but occurs after water evaporation, in powder form. This absence of gelification in the washing solution constitutes an additional advantage for the final conditioning of the contaminated effluents. Furthermore, after drying the decontaminated surfaces, the solid residue which appears in small quantity on these surfaces can be easily removed by simple dry cleaning, for example by light brushing.
Le procédé selon l'invention présente bien d'autres intérêts et avantages, dont certains sont maintenant évoqués.The method according to the invention has many other advantages and advantages, some of which are now mentioned.
A cet égard, il faut rappeler que la pratique habituelle de décontamination évoquée au début présente un caractère aléatoire assez marqué: il n'est guère possible de déterminer à priori, avec une précision acceptable, le nombre et la durée des opérations élémentaires successives de lavage décontaminant, puisque on ne peut savoir si la poussière adhère plus ou moins à un endroit ou à un autre de la surface.In this regard, it should be remembered that the usual decontamination practice mentioned at the beginning has a fairly marked randomness: it is hardly possible to determine a priori, with acceptable precision, the number and duration of the successive elementary washing operations. decontaminant, since one cannot know if the dust adheres more or less to one place or another on the surface.
A contraire, grâce au procédé selon l'invention, on connaît parfaitement l'état de la surface à décontaminer, étant donné qu'elle est constituée par le revêtement filmogène dont on maîtrise totalement tant l'application que la stabilité et que l'on peut, au moment voulu, aisément dissoudre et éliminer quelque soit la nature, la quantité, la répartition et surtout l'adhérence des contaminants qui s'y sont déposés.On the contrary, thanks to the process according to the invention, the state of the surface to be decontaminated is perfectly known, given that it consists of the film-forming coating which is completely controlled both in application and in stability and which is can, at the desired time, easily dissolve and eliminate whatever the nature, the quantity, the distribution and especially the adhesion of the contaminants which are deposited there.
On peut donc prévoir à l'avance avec exactitude les conditions d'une décontamination rationnelle. De ce fait, on ne risque plus en particulier d'immobiliser une chaîne de traitement au-delà du temps initialement prévu ou accepttable.We can therefore predict in advance exactly the conditions for rational decontamination. As a result, there is no longer any risk in particular of immobilizing a processing chain beyond the time initially planned or acceptable.
De ce fait, également, on peut se permettre notamment d'utiliser beaucoup moins de liquide de lavage et il sera ensuite plus facile et moins coûteux de concentrer les condensats par évaporation de l'eau.This also makes it possible, in particular, to allow much less washing liquid to be used, and it will then be easier and less expensive to concentrate the condensates by evaporation of the water.
En outre, la quantité de base à utiliser (par exemple la soude) est moins importante que celle consommée avec la pratique habituelle en raison, non seulement de la quantité moindre de lavage nécessaire, mais aussi parce que la concentration de liquide en soude peut être ajustée à sa valeur minimale, suffisante pour dépasser légèrement le seuil de pH à partir duquel le revêtement appliqué est parfaitement soluble. Ainsi, après évaporation de la solution usée, le concentrat résiduel, composé de l'extrait sec du vernis (la résine), de soude et des contaminants, peut être facilement calciné et on obtient ainsi des déchets d'un volume minimum.In addition, the quantity of base to be used (for example soda) is less important than that consumed with the usual practice because, not only of the less quantity of washing necessary but also because the concentration of liquid sodium hydroxide can be adjusted to its minimum value, sufficient to slightly exceed the pH threshold above which the coating applied is perfectly soluble. Thus, after evaporation of the used solution, the residual concentrate, composed of the dry extract of the varnish (the resin), soda and contaminants, can be easily calcined and thus waste of a minimum volume is obtained.
De même, si la présence d'un tensio-actif dans le liquide de lavage est souhaitable, elle n'est pas pour autant indispensable," au contraire de la pratique actuelle, puisque l'effet recherché par le lavage est essentiellement la dissolution du revêtement filmogène temporaire.Similarly, if the presence of a surfactant in the washing liquid is desirable, it is not essential, "contrary to current practice, since the effect sought by washing is essentially the dissolution of temporary film-forming coating.
De même encore, il n'est nullement indispensable, contrairement à certaines techniques connues évoquées au début, de prévoir dans la matière filmogène à appliquer des réactifs chimiques de décontamination puisque les particules se déposent directement sur le film qu'on élimine par la suite.Likewise again, it is by no means essential, contrary to certain known techniques mentioned at the beginning, to provide in the film-forming material to apply chemical decontamination reagents since the particles are deposited directly on the film which is subsequently eliminated.
Par ailleurs, conformément à une variante de mise en oeuvre de l'invention consistant à utiliser une matière filmogène colorée, d'une couleur différente de celle des surfaces revêtues, l'opérateur peut suivre visuellement et aisément sont travail, à la fois dans la phase initiale d'application uniforme de la matière et dans la phase ultérieure d'élimination correcte du film (donc des contaminants) par lavage.Furthermore, in accordance with an alternative embodiment of the invention consisting in using a colored film-forming material, of a color different from that of the coated surfaces, the operator can visually and easily follow his work, both in the initial phase of uniform application of the material and in the subsequent phase of correct removal of the film (therefore of the contaminants) by washing.
De même, il est possible, conformément à une autre variante de l'invention, de former un revêtement filmogène composite à plusieurs couches superposées de couleurs différentes. Cette manière de procéder présente, comme on l'aura compris, l'avantage de n'avoir à effectuer qu'un seul conditionnement initial des surfaces pour plusieurs décontaminations ultérieures successives.Similarly, it is possible, in accordance with another variant of the invention, to form a composite film-forming coating with several superimposed layers of different colors. This manner of proceeding has, as will have been understood, the advantage of having to carry out only one initial conditioning of the surfaces for several successive subsequent decontaminations.
De même encore, il est tout à fait possible, indépendamment ou conjointement avec la coloration, d'ajouter au vernis des additifs ayant les propriétés électrostatiques s'opposant par leurs effets à la tendance au dépôt des poussières et permettant ainsi de modifier dans le sens souhaité la quantité de poussières déposées, voire leur répartition géographique sur les surfaces.Likewise also, it is quite possible, independently or jointly with the coloring, to add to the varnish additives having electrostatic properties which oppose by their effects the tendency to deposit dust and thus making it possible to modify in the direction desired the amount of dust deposited, or even their geographic distribution on the surfaces.
Il va de soi que l'invention ne saurait se limiter aux exemples et indications précédentes, mais s'étend à de multiples variantes et équivalents dans la mesure où sont respectées les caractéristiques énoncées dans les revendications jointes.It goes without saying that the invention cannot be limited to previous examples and indications, but extends to multiple variants and equivalents as long as the features set out in the appended claims are met.
En particulier, les éléments constitutifs de la matière filmogène à appliquer, notamment du vernis lorsque ce type de produit est utilisé, peuvent varier dans une large gamme de possibilités, parmi lesquelles l'homme de métier saura faire un choix en fonction de ses souhaits ou nécessités.In particular, the constituent elements of the film-forming material to be applied, in particular varnish when this type of product is used, can vary within a wide range of possibilities, among which the skilled person will be able to make a choice according to his wishes or necessities.
Il demeure toutefois important d'utiliser une matière filmogène dont le liant soit prépolymerisé ou non polymerisable après évaporation du solvant (formation du film) et pendant une durée au moins égale à celle d'une mise en service des appareillages protégés. On évite ainsi, qu'après séchage, il ne se forme un film polymérisé qui ne soit plus soluble aisément dans les solvants usuels ou sous des conditions de lavage habituelles.However, it is still important to use a film-forming material, the binder of which is prepolymerized or non-polymerizable after evaporation of the solvent (film formation) and for a period at least equal to that of putting the protected apparatus into service. This prevents, after drying, a polymerized film is formed which is no longer easily soluble in the usual solvents or under usual washing conditions.
Ainsi, le procédé selon l'invention est réalisable avec un lavage des surfaces contaminées par une solution non seulement basique mais également par une solution acide.Thus, the process according to the invention can be carried out with washing of the contaminated surfaces with a solution not only basic but also with an acid solution.
Dans ce cas, bien entendu, le choix du revêtement filmogène temporaire sera fait en conséquence de façon à pouvoir l'éliminer par dissolution dans une solution de lavage acide, de préférence à un pH voisin de 5 au moins.In this case, of course, the choice of temporary film-forming coating will be made accordingly so that it can be removed by dissolving in an acidic washing solution, preferably at a pH of at least 5.
De même, en ce qui concerne la dissolution ultérieure du revêtement, l'opération de lavage effectuée à cet effet peut être réalisée, non seulement par jets à la lance, comme c'est impérativement-le cas dans la pratique courante actuelle, maiségalement -(quoique moins aisée de mise en oeuvre et peut être globalement moins efficace)- de façon statique, au "bain mort", par immersion dans une piscine.Likewise, with regard to the subsequent dissolution of the coating, the washing operation carried out for this purpose can be carried out, not only by jets with a lance, as is imperatively the case in current current practice, but also - (although less easy to implement and may be generally less effective) - statically, in a "dead bath", by immersion in a swimming pool.
De même encore, il n'est pas obligatoire en toute rigueur, lors du lavage décontaminant d'éliminer l'intégralité du film. Il importe seulement, en effet, que la dissolution du film soit suffisante en épaisseur pour qu'en s'éliminant, il entraîne avec lui la totalité des agents contaminants. A cet égard, une élimination partielle du film limitée à sa couche superficielle polluée peut éventuellement suffire.Likewise again, it is not absolutely necessary, during the decontaminating washing, to remove the entire film. It is only important, in fact, that the dissolution of the film is sufficient in thickness so that, when eliminated, it carries with it all of the contaminating agents. In this regard, a partial elimination of the film limited to its polluted surface layer may possibly suffice.
Par ailleurs, le domaine d'application du procédé selon l'invention s'étend au-delà du retraitement des combustibles irradiés et concerne en fait la décontamination radioactive en général, dans la limite toutefois où la contamination a pour origine le dépôt sur des surfaces, ou autres supports, de poussières ou de condensables irradiés.Furthermore, the field of application of the method according to the invention extends beyond the reprocessing of irradiated fuels and in fact relates to radioactive decontamination in general, within the limit however where the contamination originates from the deposition on surfaces, or other supports, of irradiated dust or condensables .
Ainsi, le procédé selon l'invention peut trouver des applications civiles, par exemple dans les matériels et installations situées en zone sensible dans les centrales nucléaires, ou pour les appareils de laboratoire sur lesquels peuvent s'écouler des solutions chargées de particules radioactives au cours de manipulations.Thus, the method according to the invention can find civil applications, for example in equipment and installations located in sensitive areas in nuclear power plants, or for laboratory devices on which solutions loaded with radioactive particles can flow during manipulations.
De même, le procédé selon l'invention peut également trouver des applications militaires, notamment du même type que les applications civiles pour les zones sensibles, (par exemple dans les sous-marins à propulsion nucléaire) ou pour les matériels militaires divers pouvant être contaminés par des poussières provenant d'une explosion nucléaire, lors d'essais atmosphériques, etc...Likewise, the method according to the invention can also find military applications, in particular of the same type as civil applications for sensitive areas (for example in nuclear-powered submarines) or for various military materials which may be contaminated. by dust from a nuclear explosion, during atmospheric tests, etc.
Claims (10)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR8203561A FR2522869B1 (en) | 1982-03-02 | 1982-03-02 | PROCESS FOR RADIOACTIVE DECONTAMINATION OF SURFACES |
FR8203561 | 1982-03-02 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0090680A1 true EP0090680A1 (en) | 1983-10-05 |
EP0090680B1 EP0090680B1 (en) | 1986-12-03 |
Family
ID=9271564
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19830400370 Expired EP0090680B1 (en) | 1982-03-02 | 1983-02-23 | Process for the radioactive decontamination of surfaces |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0090680B1 (en) |
JP (1) | JPS58161897A (en) |
DE (1) | DE3368143D1 (en) |
FR (1) | FR2522869B1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0566493A1 (en) * | 1992-04-17 | 1993-10-20 | Commissariat A L'energie Atomique | Process for decontaminating the surface of a ground covered by polluting particules and decontaminating solution |
EP0674323A1 (en) * | 1994-03-22 | 1995-09-27 | Commissariat A L'energie Atomique | Gel for radioactive decontaminating and protecting of surfaces |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS61209398A (en) * | 1985-03-13 | 1986-09-17 | 上村工業株式会社 | Method of decontaminating radioactive contaminated waste |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2877131A (en) * | 1946-05-06 | 1959-03-10 | Donald C Overholt | Method and coating composition for protecting and decontaminating surfaces |
FR1303673A (en) * | 1960-08-16 | 1962-09-14 | Atomic Energy Authority Uk | Sanitizing agents for purifying surfaces contaminated with radioactive materials |
EP0045983A2 (en) * | 1980-07-30 | 1982-02-17 | BBC Aktiengesellschaft Brown, Boveri & Cie. | Protection against contamination |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2380624A1 (en) * | 1977-02-09 | 1978-09-08 | Commissariat Energie Atomique | Radioactive decontamination by applying gel contg. decontaminant - then rinsing off or removing when dry |
-
1982
- 1982-03-02 FR FR8203561A patent/FR2522869B1/en not_active Expired
-
1983
- 1983-02-23 EP EP19830400370 patent/EP0090680B1/en not_active Expired
- 1983-02-23 DE DE8383400370T patent/DE3368143D1/en not_active Expired
- 1983-03-02 JP JP3300883A patent/JPS58161897A/en active Pending
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2877131A (en) * | 1946-05-06 | 1959-03-10 | Donald C Overholt | Method and coating composition for protecting and decontaminating surfaces |
FR1303673A (en) * | 1960-08-16 | 1962-09-14 | Atomic Energy Authority Uk | Sanitizing agents for purifying surfaces contaminated with radioactive materials |
EP0045983A2 (en) * | 1980-07-30 | 1982-02-17 | BBC Aktiengesellschaft Brown, Boveri & Cie. | Protection against contamination |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0566493A1 (en) * | 1992-04-17 | 1993-10-20 | Commissariat A L'energie Atomique | Process for decontaminating the surface of a ground covered by polluting particules and decontaminating solution |
FR2690163A1 (en) * | 1992-04-17 | 1993-10-22 | Commissariat Energie Atomique | Method for decontaminating the surface layer of a soil covered with polluting particles and decontamination solution |
EP0674323A1 (en) * | 1994-03-22 | 1995-09-27 | Commissariat A L'energie Atomique | Gel for radioactive decontaminating and protecting of surfaces |
FR2717709A1 (en) * | 1994-03-22 | 1995-09-29 | Commissariat Energie Atomique | Gel capable of retaining radioactive contamination and its use for protecting or decontaminating a surface. |
Also Published As
Publication number | Publication date |
---|---|
DE3368143D1 (en) | 1987-01-15 |
FR2522869A1 (en) | 1983-09-09 |
JPS58161897A (en) | 1983-09-26 |
FR2522869B1 (en) | 1988-08-12 |
EP0090680B1 (en) | 1986-12-03 |
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