EP1121690B1 - Degreasing composition and methods using same - Google Patents

Abstract

The present invention relates to a degreasing composition, to a liquid, to a gel and to a degreasing foam which comprise said composition.The composition according to the invention comprises a base, a polyethoxylated fatty alcohol, saturated or unsaturated, a copolymer of ethylene oxide and propylene oxide, and water. The invention also relates to a degreasing and/or decontamination process of a surface using said composition, said liquid, said gel, and/or said degreasing foam.

Description

Technical field of the invention

The invention relates to a degreasing composition, as well as a gel and a degreasing foam which comprise said composition.

The invention also relates to a method of degreasing and / or decontaminating a surface using said composition, said gel and / or said degreasing foam.

The present invention finds, for example, but not limited to, an application in the degreasing of surfaces, especially metal surfaces such as apparatus, components, floors, etc., of an irradiated nuclear fuel reprocessing plant. . These surfaces are, or may be, in contact with one or more fatty substances that may be contaminated. It is therefore necessary to regularly clean these surfaces for the purpose of sanitation and / or radioactive decontamination.

For example, one of these substances is a solvent called tributyl phosphate (TBP) which is used in cycles of extraction of radioactive metals such as for example uranium and plutonium. During these extraction cycles, this solvent acquires a particularly important radiochemical activity, since it can contain up to several tens of grams of uranium and / or plutonium per liter. This solvent can then become a high-activity solvent (HA solvent) or a very high activity solvent (THA solvent). The presence of these HA and THA solvents on some of the components of irradiated fuel reprocessing plants such as settling mixers, extraction columns, etc. often leads to the formation of particularly organophilic metal surfaces which promote oily deposits. later. These fatty deposits are virtually insensitive to rinsing with conventional aqueous solutions used in reprocessing and therefore require specific treatment.

On the other hand, TBP degradation products obtained by radiolysis of the solvent, for example hydrogenodibutyl phosphate (HDBP), form precipitates with most of the metal cations such as iron III, thorium IV, uranium IV and plutonium. IV, europium III, neodymium III, zirconium IV, etc. which may be present during the reprocessing of nuclear waste, and in particular irradiated fuel. These metals are often deposited on the surfaces of reprocessing plant components in contact with them in the form of colloids. Decontamination of these surfaces requires their erosion over a thickness of 2 to 10 μm to be able to eliminate all traces of radiochemical activity. This erosion can be effective only after removal of the fatty solvent covering these surfaces. It is therefore necessary to decontaminate these surfaces to have recourse beforehand to appropriate degreasing products and processes.

The composition, the gel and the foam and the degreasing and / or decontamination process that are the subject of the present invention constitute means effective degreasing and / or decontamination of these surfaces.

In general, the invention is not logically limited to the aforementioned applications, and it finds application in all areas where a rapid and efficient degreasing of an installation is necessary. Examples of these applications will be given below in the disclosure of the invention.

State of the art

In the case of a degreasing of a metal surface having been in contact with a solvent such as TBP and / or with its derivatives such as HDBP, dihydrogenomonobutylphosphate (H ₂ MBP), and tetrapropylenehydrogen (TPH), the technique generally used consists of a succession of rinsing sequences of the surface to be degreased by means of rinsing solutions which are concentrated solutions of sodium hydroxide and nitric acid. These sequences must be repeated up to 5 or 10 times and the concentrations of the solutions used are of the order of 3 to 10 mol.l ^-1 , for example 5.5 mol.l ^-1 .

This technique is however not very effective and causes many disadvantages. Indeed, nitric acid does not completely solubilize precipitates formed on still greasy surfaces including precipitates composed of dibutyl metal phosphate.

In addition, results of radioactivity analyzes of the rinsing solutions, after rinsing, show that there is no significant peak of radioactivity resulting in an effective and rapid rinsing, but a slightly higher radioactivity after two to three sequences of rinsing and then tending towards a limit, with higher activity when the rinsing solutions are renewed.

Moreover, in this technique, the rinsing solutions are used in large quantities, ranging up to five to ten times the volume of a device to be degreased, and at a very high concentration, of the order of 3 to 10 mol. .l ^-1 . This technique, although commonly used, leads to a significant increase in waste from spent nuclear fuel reprocessing.

Finally, it can be difficult to effectively separate the greases rinsing solutions of the prior art for example in processes of reprocessing these solutions (effluents).

It will be readily understood from reading the description which follows, that the present invention not only makes it possible to solve the aforementioned drawbacks in the field of the reprocessing of nuclear waste, but also in the various industrial and domestic fields in which a degreasing of surfaces is necessary.

Presentation of the invention

The object of the present invention is precisely to provide a composition, a liquid, a gel and a degreasing foam which allow an effective and rapid degreasing of a surface, and a reduction of the volume of effluents formed compared with the techniques of the invention. prior art.

The surfaces concerned may be any type of surface resistant to the degreasing composition according to the invention, for example a metal surface, a glass surface, a plastic surface, a concrete surface, etc. The metal surface may be for example a steel surface, an austenitic steel surface, a surface of uranus, aluminum, zirconium, etc. .

These surfaces can be degreased with a fatty substance which can be a fatty solvent such as TBP, HDBP, H ₂ MBP, TPH, or a mixture of these solvents, various oils such as edible oils, oils lubrication, etc ...

The degreasing composition according to the invention is characterized in that it comprises a base, a fatty alcohol, saturated or unsaturated, polyethoxylated, a copolymer of ethylene oxide and propylene oxide and water.

According to the invention, the base may be, for example, sodium hydroxide, or an equivalent base such as alcoholic potassium hydroxide

According to the invention, the base has for example a concentration of OH ^- ions chosen in a range from 0.1 to 1.5 mol.l ^-1 in said composition.

dans laquelle R est un alkyle à longue chaîne carbonée, saturée ou insaturée, comprenant de 10 à 24 atomes de carbone, et dans laquelle n représente le nombre d'unités monomériques d'oxyde d'éthylène, n pouvant varier de 10 à 30.According to the invention, the polyethoxylated fatty alcohol may be a compound of general formula:

wherein R is a saturated or unsaturated long-chain carbon alkyl of from 10 to 24 carbon atoms, and wherein n is the number of monomeric units of ethylene oxide, n being 10 to 30.

The fatty alcohol may be for example lauric alcohol, myristic alcohol, alcoholic alcohol, stearic alcohol, arachidic alcohol, palmitic alcohol, oleic alcohol, and linoleic alcohol, or a mixture thereof.

According to the invention, n may be for example equal to 10 or 20.

According to the invention, the polyethoxylated fatty alcohol may be, for example, an oleic alcohol ether and an ethylene polyoxide with 20 monomeric units of ethylene oxide.

In the composition according to the invention, the polyethoxylated saturated or unsaturated fatty alcohol is at a concentration selected from a range of about 0.01 to 1.5% by weight, or at a concentration selected from a range of ranging from about 0.05 to 0.8% by weight in said composition, or at a concentration selected from a range of about 0.05 to 0.4% by weight in the composition according to the use of the composition according to the invention for making a liquid, a foam or a degreasing gel.

ou encore

avec a par exemple égal à 22 et b par exemple égal à 9.According to the invention, the copolymer of ethylene oxide and of propylene oxide may for example be a block copolymer. It may comprise monomeric units of the ethylene oxide type and monomeric propylene oxide type units, hereinafter denoted OE and OP, respectively. This copolymer will then have the following formula (I):

or

with for example equal to 22 and b for example equal to 9.

Those skilled in the art will readily understand that the copolymer of ethylene oxide and propylene oxide may be replaced by another copolymer having the same or substantially the same properties.

According to the invention, the ethylene oxide-propylene oxide copolymer is at a concentration selected from a range of about 0.025 to about 1.5% by weight, or at a concentration selected from a range of ranging from about 0.025 to about 0.6% by weight, or in a range of about 0.025 to 0.4% by weight, or in a range of about 0.4 to 1.5% by weight. weight according to the use of the composition according to the invention to make a liquid, a foam or a degreasing gel.

For example, the base may be soda, the fatty alcohol, saturated or unsaturated, polyethoxylated may be a polyethoxylated oleic alcohol comprising 10 or 20 units of ethylene oxide, for example 20 units, and the oxide copolymer ethylene and propylene oxide can be a block copolymer containing 45 monomeric units of ethylene oxide and 9 monomeric units of propylene oxide.

The composition according to the invention may further comprise a foam inhibiting agent when it is used in liquid form, hereinafter also referred to as a degreasing liquid, or in the form of a gel. This inhibiting agent serves to prevent the formation of foam when the composition according to the invention is used in liquid form or in gel form. This inhibiting agent may be, for example, a branched or unbranched alkyl phosphate. The alkyl phosphate in the liquid or the degreasing gel according to the invention also makes it possible to increase the capacity to micellise, by example TBP, by the two other surfactants. According to the invention, the alkyl phosphate may be branched, it may comprise from 4 to 12 carbon atoms, for example from 6 to 10 carbon atoms, and may be mono or polydispersed. According to the invention, when the selected foam inhibiting agent is an alkyl phosphate having from 6 to 10 carbon atoms, it may be for example at a concentration selected from a range of about 0.1 to about 0 , 4% by weight in the composition. This concentration is for example favorable for a concentration of OH ^- ions ranging for example from about 0.5 to about 1 mol.l ^-1 .

According to the invention, the previously described composition may be in concentrated form, for example for storage. Thus, when this concentrated composition is to be used, it can be used as is or diluted with water to form a composition having concentrations of each of the components of this composition required for effective degreasing of a surface.

Thus, the present invention relates in particular to a degreasing liquid comprising a composition according to the invention, which may comprise about 0.05 to about 0.4% by weight of polyethoxylated fatty alcohol, about 0.025 to about 0.6% by weight. copolymer weight of ethylene oxide and propylene oxide, and may further comprise a foam inhibiting agent such as that described above.

This foam inhibiting agent, for example when it is a branched alkyl phosphate having 6 to 12 carbon atoms, can be at a concentration of about 0.1 to about 0.4% by weight. in the degreasing liquid according to the invention.

The present invention also relates to a degreasing foam comprising a gaseous phase and a degreasing composition according to the invention, and may further comprise a foam destabilizing agent.

The gaseous phase can be, for example, air, for example a neutral gas such as argon, or any gas making it possible to form a foam with the composition according to the invention. The foam may be formed by various means such as mechanical agitation, generation through porous lining, etc.

According to the invention, a favorable degreasing composition for forming a foam may comprise a polyethoxylated, saturated or unsaturated fatty alcohol which may be a concentration selected from a range of about 0.4 to about 1.5% by weight, a copolymer of ethylene oxide and propylene oxide which may be at a concentration selected from a range of about 0.4 to about 1.5% by weight, and may further comprise a foam destabilizing agent .

According to the invention, the foam destabilizing agent may be any of the foam destabilizing agents known to those skilled in the art, for example a compound chosen from those previously described as being foam inhibitors. For example, the foam destabilizing agent may be a branched or unbranched alkyl phosphate having from 4 to 12 carbon atoms, or from 6 to 10 carbon atoms and may be mono- or polydispersed.

According to the invention, when the foam destabilizing agent chosen is a branched alkyl phosphate containing from 6 to 10 carbon atoms, it may be at a concentration of 0.2 to 1.1% by weight in the composition according to the invention, for a weight ratio, in the composition, of the concentration of fatty alcohol, saturated or unsaturated, polyethoxylated on the concentration of the copolymer of ethylene oxide and of propylene oxide equal to about 1, 5.

The invention also relates to a degreasing gel comprising a degreasing composition according to the invention, and further comprising a viscosing agent.

According to the invention, the degreasing gel may comprise the degreasing composition according to the invention in which the polyethoxylated saturated or unsaturated fatty alcohol may be at a concentration selected from a range of about 0.05 to about 1 % by weight or in a range of from about 0.05 to about 0.4% by weight, and wherein the ethylene oxide copolymer may be at a concentration selected from a range of about 0.025 to about 0.4% by weight, and further comprising a viscosity agent.

This viscosing agent may be, for example, a compound selected from a group comprising xanthan gum, an alumina oxide or a silica gel.

According to the invention, when the viscosing agent chosen is xanthan gum, it may be at a concentration chosen from a range of from 0.5 to approximately 5% by weight in said composition, for example at a concentration of approximately 1.2% by weight.

The invention thus relates in particular to a composition, a liquid, a foam, and a gel comprising said composition. These different formulations, that is to say liquid, foam and gel, allow a rapid and effective degreasing of a surface as those mentioned above. It has been found that the present invention makes it possible in particular to reduce the quantity of effluents resulting from the degreasing and a decrease in the Na ⁺ concentration of these effluents compared to the prior art, and consequently, a reduction in waste arising from of this degreasing, for a better degreasing efficiency.

The degreasing efficiency of the present invention is due in particular to the nature of the various constituents of this composition and to their concentration.

The composition according to the invention comprises a base. This base makes it possible to form a basic aqueous solution which facilitates the degreasing of a surface as well as a transfer of the fatty substance coming from these surfaces into the aqueous solution in the form of an emulsion. The degreasing efficiency of the composition is in particular a function of the alkalinity of this aqueous solution. According to the invention, the base used is at a concentration of OH ^- selected in a range from 0.1 to 1.5 mol.l ^-1 . In the example of sodium hydroxide, compared with the solutions used in the prior art mentioned above, the composition of the invention thus makes it possible to save up to a factor of up to 10 Na ⁺ ions for the same number. rinsing sequences applied to a surface to be degreased and for better efficiency.

The composition according to the invention also comprises a fatty alcohol, saturated or not, polyethoxylated. This polyethoxylated fatty alcohol is a nonionic surfactant comprising a lipophilic chain formed by the fatty alcohol and a polar head formed by polyethoxyl. The lipophilic chain allows the composition of the invention to ensure optimal detergency and dispersion of fatty substances, or lipophilic organic constituents, in the basic aqueous solution. The polar head makes it possible to ensure the solubility in the aqueous alkaline phase. For example, the polyethoxylated fatty alcohol of the composition according to the invention may consist of an oleic alcohol and an ethylene oxide composed of a chain of twenty monomeric units of ethylene oxide as represented by the following formula (II):

This polyethoxylated fatty alcohol may be for example SIMULSOL 98 or SIMULSOL 96 (trademarks) manufactured by the company SEPPIC.

This polyethoxylated fatty alcohol, with fatty substances, forms micelles which are spherical particles with a diameter of 50 to 150 nm having a polar outer face in contact with the basic aqueous solution and an apolar inner face in contact with the fatty substances. . The fatty substances are retained inside these micelles and dispersed therewith in the basic aqueous solution. The result of this retention and dispersion is a dissolution of the fats in the basic aqueous solution.

The composition according to the invention also comprises an alkylene oxide polymer. This polymer is a nonionic surfactant. It makes it possible, in particular, to confer on the aqueous alkaline solution of the invention a good wettability with respect to the surface to be degreased, and to inhibit any foaming of the aqueous solution resulting from degreasing when the latter is subjected to a treatment. such as a concentration by evaporation, for example in the example of TBP and its derivatives, before calcination for incorporation into a glassy matrix. An example of an alkylene oxide polymer suitable for the composition according to the invention may be a block copolymer containing 45 ethylene oxides and 9 propylene oxides, as represented by the following formula (III):

This copolymer has a molar mass of 2500 g.mol ^-1 and a hydrophilic lipophilic balance (HLB) of the order of 15.

The alkylene oxide polymer may be, for example, SYNTHIONIC P8020 (trademark) manufactured by WITCO, or PLURONIC PE (trademark), in particular of type 6400, 6800, 9400 and 10500, manufactured by the company BASF.

When the chosen formulation is a liquid or a gel, the composition according to the invention may further comprise a foam inhibiting agent. Indeed, the composition according to the invention comprises a surfactant that can under certain conditions cause the formation of a foam. This foam can be troublesome for example in a degreasing process using an aero-ejector or air lift ("airlift"). This inhibiting agent may be, for example, an alkyl phosphate comprising from 4 to 12 carbon atoms as represented by the following formula (III):

This inhibiting agent makes it possible to increase the drainage rate of the interstitial fluid contained in a forming foam, and thus to limit or prevent this formation. It also improves the wetting power of the composition and can play an important role in the retention of the fat (s) in the micelles. It therefore also allows, as emphasized above, to increase the ability to micellise, for example TBP, by the two surfactants of the composition according to the invention. Examples of alkyl phosphate are MONTALINE ANP and SEPPIC 619NP (trademarks) manufactured by the company SEPPIC. It acts as a dispersant and allows, for example, to keep in suspension precipitates of Pu, Am, U and Zr dibutyl phosphates which are produced by the extraction of the solvent in an alkaline medium.

When the chosen formulation is a foam, the composition according to the invention may further comprise a foam destabilizing agent. This agent destabilizing agent may be the same as the aforementioned foam inhibiting agent, but in this case it will control the stability of the foam formed, that is to say the time required for a total transformation of a given volume of this foam in liquid and gas. This time, or lifetime, can be modified by modifying the concentration of this destabilizing agent in the composition according to the invention. This destabilizing agent facilitates drainage of interstitial fluid into the foam.

In general, the concentration of destabilizing agent is chosen to obtain a lifetime of the foam of 10 to 30 minutes. Such a lifetime can be adapted for example to fill a container of a given volume in an acceptable time and have a foam having a sufficient drainage rate so that the composition according to the invention can degrease the surface of this container. In fact, when the foam has filled the container, it produces, if its life is suitably chosen, a drainage liquid which, dripping on the walls of the container, dissolves the fatty substance, for example TBP and its derivatives, and leads in the form of micelles. The drainage liquid, loaded with these micelles can then be recovered in a lower part of the container, and can be recycled.

When the chosen formulation is a gel, the composition according to the invention may further comprise a viscosing agent. This viscosing agent allows, for example, a controlled local application of the gel formed comprising the composition according to the invention for a degreasing of an accessible surface to an operator. An example of a viscosity agent that can be added to the composition according to the invention is xanthan gum. It is a polysaccharide comprising a sequence of 16 molecules, of which 13 are linear and three branched and its molecular weight is several million. It allows the formation of non-Newtonian gels that are resistant to heat and pH variations.

As described above, the degreasing of a surface consists in particular in solubilizing in the aqueous solution (the) substance (s) present (s) on the surface to degrease in the form of micelles. These micelles are formed in particular with fatty alcohol, saturated or unsaturated, polyethoxylated and contain solubilized fatty substance (s).

Micelles are dynamic particles that form and disintegrate constantly in the solution. When the concentration of one of the constituents of the composition according to the invention is too low, especially with respect to the amount of fat substance (s) to be dissolved, the micelles can dissociate and release the substance (s) ( s) greasy (s) which redeposit (s) then on degreased surfaces. The dissociation of micelles is visible and results in the formation of a disorder in the solution. This dissociation can occur when the composition according to the invention is saturated with fat substance (s), and / or from a certain temperature.

The saturation of the composition according to the invention with a fatty substance can be measured by measuring the "cloud point" of this composition. The cloud point is expressed in degrees Celsius (° C). The point of nonionic surfactant disorder polyoxyethylene corresponds to a partial dehydration of the hydrophilic chain, and which results, if the temperature of the cloud point is reached, the phase separation, that is to say the demixing of the surfactant.

If the cloud point is at room temperature, it may cause the fat to be redeposited on the degreased surfaces at room temperature. It is therefore preferable that the cloud point of the composition is greater than room temperature, i.e., about 20 ° C, when the degreasing is performed at or above room temperature. A high cloud point also indicates a high capacity for dissolving a fatty substance. The measurement of the cloud point thus makes it possible in particular to measure the degreasing efficiency of the composition according to the invention. This degreasing efficiency can also be measured by measuring the wettability of this surface.

The degreasing efficiency of a surface by the composition according to the invention is therefore due in particular to the nature of the constituents of this composition. This efficiency is also due to the concentrations of its various constituents.

The concentration of each of the constituents of the composition according to the invention can be adjusted, starting from the concentration ranges described previously, in particular according to the nature and the quantity of fatty substance (s) present (s) on the surface to be degreased, the surface to be degreased, the liquid formulation, foam or gel used, and the temperature at which the degreasing is carried out.

In one embodiment of the present invention, the composition according to the invention comprises sodium hydroxide or an equivalent base, an oleic alcohol ether and an ethylene oxide oxide comprising twenty ethylene oxide units, and a block copolymer containing 45 ethylene oxide units and 9 propylene oxide units, hereinafter referred to as block copolymers.

In a first variant of this embodiment, the aforementioned composition is used to form a degreasing liquid. It may be desirable to adjust the concentrations of each of the above-mentioned components so that the liquid is low foaming. Thus, for example, a degreasing liquid comprising from about 0.5 to about 1 mol.l ^-1 of NaOH, from about 0.05 to about 0.4% by weight of polyethoxylated oleic alcohol, preferably from about 0.05 to about 0.2% of this alcohol, and about 0.025 to about 0.4% by weight of the block copolymer, or about 0.1 to about 0.4% by weight, or still about 0.2 to about 0.4% by weight of this copolymer is a low foaming composition. The liquid may further comprise a foam inhibiting agent. According to this first variant, the composition according to the invention has a cloud point higher than the ambient temperature, approximately equal to 38 ° C., and even higher than 40 ° C.

A decrease in the concentration of polyethoxylated fatty alcohol or block copolymer can increase this cloud point.

Such a composition makes it possible, for example, effectively degreasing a metal strip covered with approximately 1 mg / cm ² of a mixture comprising TBP and its derivatives HDBP and H ₂ MBP, or a mixture comprising TPH, TBP and its derivatives HDBP and H ₂ MBP in a time ranging from about 15 to about 200 minutes, without agitation, and at a temperature of 20 ° C. The defatted blade may indeed have a surface tension cos θ tends to 0, which reflects an almost total or total degreasing of the surface.

However, in some cases, especially for a concentration of polyethoxylated oleic alcohol, that is to say in oleic alcohol ether and polyoxyethylene glycol, about 0.2% or more, this formulation can become foaming when the NaOH concentration is less than or equal to about 0.5 mol.l ^-1 . The composition may then be adjusted and may further include a suds inhibiting agent. This is the case for example for use in a degreasing process using stirring or transport of this liquid composition by means of an air lift or air-lift. Indeed, the pressure and agitation experienced by the liquid in such a process requires a composition having low foamability. The foam inhibiting agent may be for example an alkyl phosphate such as that mentioned above, at a concentration ranging from about 0.1 to about 0.4% by weight, or about 0.3 to about 0.4% by weight in the composition. When this inhibiting agent is added to the composition, in order to preserve and possibly improve the degreasing power of the composition, it may be necessary to increase the concentration of oleic alcohol ether and polyoxyethylene glycol to about 0.3%. in weight. Too much of the latter, and the alkyl phosphate in the composition can however reduce the amount of fat substance (s) that can be retained in the micelles. The concentration of block polymer can then be adjusted to a concentration of about 0.15 to about 0.45% by weight to obtain a cloud point below 80 ° C. For example, a composition comprising about 0.2% by weight of oleic alcohol ether and polyoxyethylene glycol, about 0.35% of block copolymer, about 0.5 to 1 mol.l ^-1 of NaOH, preferably about 0.5 mol.l ^-1 of NaOH, and about 0.4% by weight of alkyl phosphate has a cloud point of 68 ° C. This composition is a low-foaming composition which allows for example a dissolution of about 3 g / l of TBP and its derivatives, and a degreasing of a surface comprising 1 mg / cm ² of TBP and its derivatives in about 20 minutes.

This low foaming composition is compatible for transport by means of an air lift.

In this first variant, the inventors have observed that the cloud point of the composition varies linearly from about 71 to about 20 ° C. with the sodium concentration in a range of from about 0.1 to about 1, respectively. 45 mol.l ^-1 NaOH especially in a natural convective regime, that is to say without stirring the solution of the composition during degreasing.

In a second variant, the composition of this embodiment is used in the form of foam.

The development of a foaming solution from the composition according to the invention can be carried out for example with a concentration of oleic alcohol ether and polyoxyethylene glycol of about 0.4% to about 1.5% by weight. for example from about 0.4 to about 1% by weight, for example with a sodium concentration ranging from 0.5 to 1.5 mol.l ^-1 . For example, when the weight ratio of the concentration of oleic alcohol ether and polyoxyethylene glycol to the block copolymer concentration is from about 1.5 to about 2.5, the concentration of ether of oleic alcohol and polyoxyethylene glycol can be from about 0.35 to about 0.60% by weight. These concentrations can be adapted to the amount of fat substance (s) to dissolve.

This composition is suitable for example for generating a foam from a foam generator comprising a porous lining. This foam generator may for example be composed of a cylinder 120 mm long and 8 mm in diameter filled with 3.24 g of a type of packing FORAFLON (trademark). The foam can be generated for example with a flow rate of a solution of this composition ranging from about 23 to about 28 l / h, and a gas flow, for example air, of about 88 l / h in normal conditions of temperature and pressure. The foam can be generated easily in this example at a rate of from about 120 to about 130 l / h. This foam may have a swelling, that is to say a ratio of the volume of foam generated on the volume of interstitial liquid ranging from about 6 to about 7. This foam is suitable for example to easily solubilize 1.2 g / l TBP and its derivatives.

According to the invention, the ratio of the gas flow rate to the liquid flow rate can be about 6 to 7 to generate a foam from a composition according to the invention and a gas.

As described above, it may be interesting to control the life of the foam generated by adding for example a foam destabilizer. This foam destabilizer may be for example an alkyl phosphate such as that described above, at a concentration of from about 0.2 to about 1.1% by weight in the composition, for example, when the composition comprises a ratio weight of fatty alcohol, saturated or unsaturated, polyethoxylated on the concentration of ethylene oxide copolymer and propylene equal to about 1.5 (that is to say a molar ratio of about 3.3). For example, the alkyl phosphate may be about 0.3% by weight.

For example, when the sodium hydroxide has a concentration greater than or equal to 0.5 mol.l ^-1 , the alkyl phosphate may be at a concentration of about 0.3 to about 0.5% by weight, and when the soda at a concentration of less than 0.5 mol.l ^-1 , the alkyl phosphate may be at a concentration of about 1% by weight.

This composition is particularly effective for degreasing for example a metal surface on which there is TBP and its derivatives.

This latter composition makes it possible, for example, to form a foam at a flow rate of approximately 1.6 m ³ / h for a flow rate of an aqueous solution of this composition of approximately 200 l / h and a flow rate of gas, for example air, about 1200 l / h in a foam generator with a volume of 77 cm ³ and a diameter of 2.4 cm comprising 29 g of FLORAFLON porous seal (trademark). The formed foam can have a shelf life, with the above concentrations, ranging from about 10 to about 30 minutes. Following these concentrations, the composition according to the invention can make it possible to dissolve up to 4 g / l of TBP and its derivatives. The foam rate and its expansion can be increased when the concentration of alkyl phosphate increases from 0.3 to 0.4% by weight in this composition.

In a third variant of this embodiment, the composition is used in the form of a gel. According to this third variant, the composition according to the invention may comprise, for example, from about 0.05 to about 1% by weight or alternatively from about 0.05 to about 0.4% by weight of oleic alcohol ether. and polyethylene oxide, from about 0.025 to about 0.4% by weight of block copolymer, a foam inhibitor and a viscosity agent. The viscosing agent may be xanthan gum. This viscosity agent may be added in an amount to obtain a gel having, for example, a viscosity of about 0.8 cps (800 cps). When the viscosing agent is xanthan gum, it may for example be added at a concentration of about 1.2% by weight. According to this third variant, it may be advantageous to use a low foaming or weakly foaming composition such as those described in the first variant of this embodiment of the present invention, that is to say comprising a foam inhibitor.

When the fatty substance to be solubilized is too large in relation to the concentrations of the constituents of this gel, the degreasing of a surface comprising TBP and its derivatives is not impaired, but it can lead to a triphasic solution which can cause a redeposition of the TBP. An augmentation of the concentration of ether of oleic alcohol and of polyoxyethylene glycol and of block copolymer, for example from 5 to 10 times the concentrations mentioned above, can make it possible to obtain under these conditions a monophasic system, that is to say having a optimal degreasing efficiency.

According to the invention, it appears obvious that the concentrations of each of the constituents in each of the variants of the aforementioned embodiment can be modified depending on the nature and the amount of fat substance (s) to be dissolved for degreasing of a surface, and so as to minimize the volume of the degreasing effluents. The above concentrations are suitable, for example, for degreasing surfaces containing TBP, TPH, HDBP and H ₂ MBP.

The composition, the gel and the foam object of the present invention make it possible to degrease a surface covered with a fatty substance with which they are brought into contact. This contacting can be carried out by any contacting means for applying a liquid, a foam or a gel on a surface to be degreased or cleaned. According to the invention, the contacting means is preferably chosen as a function of the surface to be degreased, and so as to minimize the effluents resulting from degreasing.

For example, when the composition according to the invention is used in liquid form, the contacting of the liquid with the surface to be degreased can be carried out for example by dipping, with or without stirring, by spraying, with or without pressure, or by release. Soaking can be used by For example, for degreasing surfaces of small objects or sealed containers, the spraying can be used to degrease for example larger areas, and circulation for example for pipes. The liquid formulation of the composition according to the invention may allow for example to use an air lift transport ("airlift") for a degreasing of the pipes by putting this formulation into circulation in these pipes.

When the composition according to the invention is used in the form of a foam, the bringing into contact can be done for example by dipping or by circulation. Soaking can be used, for example, to degrease containers and, more generally, bulky structures, and the circulation can be used, for example, for large pipe networks of an installation having, for example, a complex internal geometry. The foam formulation makes it possible to significantly reduce the volume of effluents formed in a degreasing process.

Finally, when the composition according to the invention is used in gel form, the placing in contact can be carried out by applying the gel to the surface to be degreased, for example by means of a roller, a cloth, a spatula , or a sponge. This application can be used for example to degrease a surface accessible to an operator such as an external surface of an installation, a floor, a retention tank or a cell floor in an irradiated fuel reprocessing plant. The composition used in gel form can allow a more localized contact on a surface to be degreased than the liquid or the foam.

According to the invention, the contacting can be carried out at any temperature suitable for degreasing a surface with the composition according to the invention. This temperature can be chosen according to the liquid formulation, foam or gel used, and depending on the surface to be degreased. The choice of this temperature depends of course on the cloud point of the composition used. Indeed, a temperature above the cloud point of the composition causes a separation of the micelles from the aqueous solution, resulting in a portion of the surfactants and TBP associated therewith. The solution becomes two-phase. According to the invention, this temperature may be, for example, the ambient temperature, or a temperature greater than the ambient temperature and lower than the cloud point of the composition.

According to the invention, the contacting of the composition with the surface to be degreased may be carried out for a period of time which may in particular be a function of the nature and amount of fatty substance (s) present on the surface. surface to be degreased, the concentration of each of the constituents of the composition according to the invention, the liquid formulation, foam or gel used, the contacting means used, and the contacting temperature. This time can be very short and reach 15 to 20 minutes for soaking the surface to be degreased, without agitation and at room temperature.

The present invention thus also relates to a method of degreasing a surface, said method comprising contacting the surface to be degreased with a composition, a liquid, a foam, or a gel according to the invention.

This method applies for degreasing of surfaces such as those described above, and makes it possible to remove one (or more) fatty substance (s) such as that (s) described (s) previously.

The bringing into contact may be carried out under the conditions described above and with concentrations of each of the constituents of the composition, of the foam or of the gel as described above.

This contact can be repeated one or more times, renewing or not each contacting the composition, the foam or the gel used.

This contacting may be preceded and / or followed by a treatment, for example in a highly concentrated acid medium, for example HNO ₃ in the case of a surface comprising TPH, TBP or its derivatives, in particular in a reprocessing plant. irradiated fuel.

The surface can then be rinsed, for example with water and then dried.

This process makes it possible, for example, to degrease the surfaces of workshops of nuclear fuel reprocessing plants using in particular solvents such as TBP and its derivatives as a solvent for extracting fuels. The method of the invention is an effective means of degreasing these surfaces and has many advantages over the prior art.

Indeed, because of a radioactive contamination of the aforementioned solvents, the effluents of degreasing of these surfaces must be treated and then stored in confinement in the bitumen drums. The degreasing process of the prior art, because of the concentration and the volume of the solutions used, provides a large quantity of degreasing effluents, which is difficult to treat and leads to a large number of bitumen drums or glass.

The composition and the method of the invention make it possible to significantly reduce the volume of the degreasing effluents, and in the example of a composition according to the invention comprising sodium hydroxide, their concentration of sodium, and thus to reduce the number of bitumen drums compared to the prior art.

In addition, for the treatment of these effluents, the composition according to the invention makes possible the concentration of TBP and its derivatives dissolved and retained in the micelles, by evaporation of the water of these effluents. Indeed, the concentrations of the various constituents of the composition according to the invention can be chosen to have a cloud point lower than the boiling temperature of the TBP and its derivatives.

The invention also provides an effective means for preparing a surface for radioactive decontamination. In irradiated nuclear fuel reprocessing plants, some TBP derivatives, such as HDBP, form precipitates with most of the metal radioactive cations present within these facilities. These precipitates are deposited on the surfaces of these installations in the form of colloids, and the radioactive decontamination of these surfaces requires their erosion to a thickness of 2 to 10 microns. This erosion can only be effective after removal of the fatty solvents from these surfaces, in particular colloids, TBP and derivatives thereof, ie after effective degreasing of these surfaces.

Also, the present invention also relates to a method of radiochemical decontamination of a surface comprising in this order: a degreasing of said surface by the method of the invention, and a radioactive decontamination of the degreased surface.

This radiochemical decontamination process makes it possible to treat surfaces contaminated by numerous radionuclides such as actinides and fission products.

The surfaces, fatty substance (s), compositions, liquid, foam and gel may be those described above.

According to the invention, the radioactive decontamination may be a decontamination by chemical erosion, for example a chemical erosion chosen from an erosive cerium treatment, an erosive HF treatment and a specific treatment of ruthenium.

Erosive cerium treatment consists in treating a surface by bringing this surface into contact with a treatment solution comprising a mixture of concentrated nitric acid and cerium IV, for a time and at a temperature such that the erosion of this surface is made to a thickness of 2 to 10 microns. The concentration of nitric acid can be for example 2 mol.l ^-1 and that of cerium of 0.05 mol.l ^-1 . The treatment may for example be carried out for a period of 2 hours, for example at 50 ° C., and may comprise stirring of the treatment solution. This treatment is intended to displace the fixed contamination in addition to the solvent borne labile contamination.

The erosive HF treatment consists in treating a surface by bringing this surface into contact with a treatment solution comprising a mixture of concentrated nitric acid and HF, for a time and at a temperature such that the erosion of this surface is make on a thickness of 2 to 10 microns. The concentration of nitric acid can be for example 2 mol.l ^-1 and that of HF 0.1 mol.l ^-1 . The treatment may for example be carried out for a period of 5.5 hours, for example at 50 ° C., and may comprise stirring of the treatment solution. This treatment is intended to complex certain radionuclides such as Pu, Zr, U, Am and to displace the contamination fixed on the surface.

The specific ruthenium treatment consists in treating a surface by contacting this surface with a treatment solution comprising a mixture of KMnO ₄ and sodium hydroxide. The concentration of KMnO ₄ may for example be 0.05 mol.l ^-1 , and the sodium hydroxide concentration of 0.5 mol.l ^-1 . The treatment may for example be carried out for a period of 2 hours, for example at 50 ° C., and may comprise stirring of the treatment solution. This treatment is intended to eliminate contamination due to ruthenium 106 ( ¹⁰⁶ Ru). It can be followed by soaking the surface in nitric acid.

This method of radiochemical decontamination is more efficient than that of the prior art which included degreasing by the method of the prior art and an oxidation treatment which makes it possible to solubilize the ruthenium oxides. In fact, the process of the invention makes it possible to improve radiochemical decontamination of a surface in a consistent manner, since residual radioactivity measurements of the surfaces decontaminated by this process have shown a residual activity up to 20 times lower than that obtained. by the method of the prior art, and a measure of decontamination factor FD of these surfaces has shown a gain of the order of 10 compared to the prior art.

Remember that this process also reduces up to 11 times the amounts of sodium hydroxide used, when the composition comprises sodium hydroxide, compared to the prior art, and with a better efficiency of degreasing.

In addition, tests carried out without agitation of the degreasing solutions showed as effective degreasing of the surfaces as with stirring.

A compatibility study of the composition according to the invention with the various treatments of degreasing effluents and possibly decontamination of irradiated fuel reprocessing plant surfaces has been carried out. This study has shown that a concentration by evaporation of the effluent, in a neutral or acidic medium, with a view to a volume reduction of approximately 10 times, results in the production of a biphasic concentrate which can be emulsified by pumping for transfer to a chemical treatment. Chemical precipitation in an unconcentrated effluent of various inorganic absorbents of radioelements such as insoluble hydroxides, sulphates and ferrocyanides, and associated absorption of inactive tracers of Cs, Sr, Ce, Ru, on these compounds are not modified by the presence of a composition according to the invention. A comparison of decontamination factors in the absence or in the presence of a composition according to the invention shows that there is no change in the performance of a chemical insolubilization process due to this composition. In addition, the amount of sludge formed remains the same with or without composition according to the invention. Sedimentation of the suspensions, used as solid / liquid separation means in a second stage of chemical treatment of the effluents is little disturbed by the presence of surfactant compounds. Indeed, a solids / liquid separation on rotary filter with diatom precoat, carried out under partial vacuum, poses no problem with a composition according to the invention, for example when it has a concentration of approximately 1.38 g / in aqueous solution: no foaming is observed and the presence of the composition according to the invention does not disturb the filtration.

Many other advantages of the present invention will become apparent from the following examples.

Example 1 : Comparative Example of Degreasing

This example is a comparative example of the degreasing efficiency of a composition and a process according to the invention with respect to solutions and a process of the prior art.

• Mélange A : 0,9% en poids de TBP + 0,1% en poids d'un mélange comprenant 60% de HDBP et 40% de H₂MBP.
• Mélange B : 0,7% en poids de TPH + 0,27% en poids de TBP + 0,03% en poids d'un mélange comprenant 60% en poids de HDBP et 40% en poids de H₂MBP.

In this example, the surface to be degreased is an austenitic steel blade covered with approximately 1 g / cm ² of one of the following mixtures A and B which represent the fatty substance to be dissolved.

• Mixture A: 0.9% by weight of TBP + 0.1% by weight of a mixture comprising 60% of HDBP and 40% of H ₂ MBP.
• Mixture B: 0.7% by weight of TPH + 0.27% by weight of TBP + 0.03% by weight of a mixture comprising 60% by weight of HDBP and 40% by weight of H ₂ MBP.

• trempage de chaque lame dans une solution d'acide nitrique à 5 mol.l^-1 à une température de 50°C pendant 60 minutes,
• rinçage de chaque lame à l'eau à une température de 50°C pendant 5 minutes,
• trempage de chaque lame dans une solution de soude à 5 mol.l^-1 à une température de 50°C pendant 120 minutes,
• rinçage de chaque lame dans de l'eau à une température de 50°C pendant 5 minutes,
• trempage de chaque lame dans une solution d'acide nitrique à 5 mol.l^-1 à une température de 50°C pendant 60 minutes, et
• rinçage de chaque lame à l'eau à une température de 50°C pendant 5 minutes.

The method of the prior art comprises the following sequences, in this order, and with stirring of the solutions used, by means of a magnetic bar, at 500 rpm:

• dipping each slide in a solution of nitric acid at 5 mol.l ^-1 at a temperature of 50 ° C for 60 minutes,
• rinsing each slide with water at a temperature of 50 ° C for 5 minutes,
• soaking each slide in a 5 mol.l ^-1 sodium hydroxide solution at a temperature of 50 ° C. for 120 minutes,
• rinsing each slide in water at a temperature of 50 ° C for 5 minutes,
• soaking each slide in a solution of nitric acid at 5 mol.l ^-1 at a temperature of 50 ° C for 60 minutes, and
• rinsing each slide with water at a temperature of 50 ° C for 5 minutes.

The method of the invention comprises dipping each slide in a composition according to the invention, without stirring, at a temperature of 20 ° C.

In this example, two different compositions according to the invention are used. These two compositions each comprise 0.12% by weight of oleic alcohol ether and of polyoxyethylene glycol with 20 ethylene oxide units, of the trademark SIMULSOL 98 manufactured by the company SEPPIC (formula (I) above and 0.57% by weight of 45 block copolymer of ethylene and 9 propylene oxides of the trademark SYNTHIONIC P8020 manufactured by the company WITCO (formula (II) above). A first of these two compositions, hereinafter referred to as composition 1, comprises 0.5 mol.l ^-1 of NaOH, and the second of these compositions, hereinafter referred to as composition 2, comprises 1 mol.l ^-1 of NaOH. The cloud point of these two compositions is 38 ° C.

The degreasing efficiency of these two processes was compared by measuring the contact angle between an aqueous solution and each defatted metal slide, by the SCHULTZ method, and by measuring the minimum contact time for a total degreasing of these blades. An angle of wetting equal to 0 represents a total degreasing of the surface, that is to say a recovery of the grease from the metal surface. To move this fat, the aqueous solution must allow its micellization.

Table 1 below groups the results of these measurements:

The results of this example show that the degreasing of each blade, by the method of the prior art, covered with the mixture A or with the mixture B, is only partial for a total duration of this process of 255 minutes, at a temperature of 50 ° C and for highly concentrated solutions of nitric acid and sodium hydroxide.

While the method and composition according to the invention allow a total degreasing of the blades, regardless of the mixture A or B covering these blades for a total treatment time of 200 and 30 minutes, for solutions up to ten times less concentrated than the solutions of the prior art, and at room temperature.

In addition, additional tests have shown that a degreased blade with the composition 1 or 2 is perfectly wettable by 5N nitric acid, which is not the case of a degreased blade by the solutions and the method of the prior art.

Example 2 : Degreasing kinetics of a surface with a composition according to the invention

In this example, a metal blade covered with 0.75 g / cm ² of a mixture C of solvent TPH + TBP + HDBP + H ₂ MBP comprising 70, respectively; 27; 1.8 and 1.2% by weight of these solvents and a metal plate coated with 1.2 mg / cm ² of a mixture D of solvent TBP + HDBP + H ₂ MBP comprising 90 respectively; 6 and 4% by weight of these solvents are defatted by immersion without stirring in an aqueous solution of the composition according to the invention comprising 0.5 mol.l ^-1 sodium hydroxide, 0.12% by weight of SIMULSOL 98 (brand 0.57% by weight of SYNTHIONIC P8020 (trademark). Degreasing is carried out at room temperature. Degreasing kinetics are monitored by measuring, over time and at regular intervals, the surface tension γcosθ of each slide by the WILHELMY submerged blade method and determining the corresponding cosθ. Table 2 below groups the results of this example. <b><u> Table 2: Degreasing kinetics of a surface with </ u><u> a composition according to the invention </ u></b> Time (minute) 0 5 10 20 30 45 60 90 120 180 mixture C: cos θ 0.83 0.75 0.69 0.71 0.78 0.90 0.90 0.95 1 - mixture D: cos θ 0; 6 0.67 0.66 0.65 0.75 0.78 0.83 0.89 0.96 1

From the results of this example, it appears that it takes about 120 minutes to degrease perfectly (cosθ = 1) the blade covered with the mixture C and 180 minutes to perfectly degrease the blade covered with the mixture D under the same conditions with the composition according to the invention.

Kinetics tests identical to those of this example were carried out with a concentration of sodium hydroxide in the composition according to the invention of 1 mol.l ^-1 . The kinetics of degreasing was much faster, since 30 minutes were sufficient to degrease perfectly the blade covered with the mixture D. These tests showed that the solubility of the mixture D is 305 times higher with the soda 1 mol.l ^{- 1} with sodium hydroxide 0.5 mol.l ^-1 .

For comparison, a treatment of the same blades with sodium hydroxide at a concentration of 5 mol.l ^-1 , without surfactant with agitation of 500 rpm, and for 120 minutes does not allow total degreasing of the blades. Indeed, the cosθ obtained by this treatment is only 0.81.

Additional tests have shown that a dilution of a composition according to the invention by a factor of 2 increases the duration of degreasing of the same factor.

Example 3 Degreasing Efficiency of a Surface with a Low Foaming Composition According to the Invention

This example illustrates the degreasing efficiency of a surface by solutions of low foaming compositions according to the invention.

In this example, the compositions used comprise a constant concentration of sodium hydroxide equal to 0.5 mol.l ^-1 , and a constant concentration of ether. of oleic alcohol and polyoxyethylene glycol equal to 0.2% by weight. The fatty alcohol used is SIMULSOL 98 (trademark) manufactured by the company SEPPIC. These compositions comprise a variable block copolymer concentration of the trademark SYNTHIONIC P8020 manufactured by WITCO, and further include a foam inhibiting agent in a variable concentration. This foam inhibiting agent is an alkyl phosphate of the trademark MONTALINE ANP manufactured by the company SEPPIC. The surface to be degreased is a steel strip covered with 1 mg / cm ² of TBP.

Degreasing is carried out at ambient temperature and without stirring the degreasing solutions.

The degreasing efficiency of these solutions is evaluated by measuring the cloud point (in ° C) of each of these solutions, by measuring the time, in minutes, required for each of these solutions to completely degrease the metal blade of in order to obtain a surface tension such as cosθ≈1, and by measuring the amount (in g / l) of TBP that each solution can dissolve. Table 3 below groups the results of this example. <b><u> Table 3: Effectiveness of degreasing compositions </ u><u> weakly foaming according to the invention </ u></b> Synthionic P8020 (%) Montaline ANP (% by weight) Cloudy point (° C) Effectiveness of degreasing (mn) for cosθ≈1 TBP that can be dissolved (g / l) 0.25 0.3 69 40 2.8 0.25 0.4 73 40 2.9 0.35 0.3 71 20 2.1 0.35 0.4 65 20 3 0.45 0.3 55 20 1.5 0.45 0.4 59 20 1.2

These results show that for a sodium hydroxide concentration of 0.5 mol.l ^-1 and for a SIMULSOL 98 concentration of 0.2% by weight, the composition according to the invention comprising 0.35% by weight of SYNTHIONIC P8020 and 0.4% by weight of MONTALINE ANP seems the most effective for dissolving TBP.

Airlift testing of these compositions has shown that the production of foam is sufficiently low so as not to clog the separator pot of the "airlift".

Example 4 Example of a Foam Comprising the Composition According to the Invention

The solutions used to form the foam of this example include a concentration of SIMULSOL 98 (Trade Mark) greater than or equal to 0.4% by weight, a concentration of SYNTHIONIC (Trade Mark) greater than 0.26% by weight, and further include a foam destabilizing agent. This destabilizing agent is MONTALINE ANP (brand of commerce) previously described as a foam inhibitor.

In this example, all the compositions comprise a constant sodium concentration equal to 0.75 mol.l ^-1 .

Foams were made from these compositions from a static generator consisting of a cylinder 120 mm long and 8 mm in diameter filled with 3.24 g of a porous filling type FORAFLON (trademark ).

The generator was powered by each foaming solution using a gear pump with a liquid flow rate of 23 to 28 l / h and air at 88 l / h under normal temperature and pressure conditions. The foams are obtained at a flow rate of 120 to 130 l / h, with an expansion ranging from 6 to 7 and a lifetime of 15 + 2 minutes.

In this example, the amount of TBP and its derivatives HDBP and H ₂ MBP (in g / kg) which can be dissolved in various compositions according to the invention were measured. The tests were carried out at room temperature.

Table 4 below groups the results obtained in this example. <b><u> Table 4: dissolution of the TBP for different foams </ u><u> comprising composition according to the invention </ u></b> TBP + HDBP + H ₂ MBP (g / kg)
(NaOH = 0.75 mol.l ^-1 ) 0 0.6 1.2 2 2.5 SIMULSOL 98
(% in weight) 0.4 0.6 0.9 1.2 1.45 SYNTHIONIC P8020
(% in weight) 0.26 0.4 0.6 0.8 0.95 MONTALINE ANP
(% in weight) 0.3 0.3 0.3 0.3 0.3

These results show that when the contents of SIMULSOL 98 and SYNTHIONIC P8020 are increased, the dissolution of the TBP is increased.

Additional tests with a composition comprising 0.75 mol.l ^-1 NaOH, 0.8% by weight of SIMULSOL 98 (trade mark), 0.6% by weight of SYNTHIONIC P8020 (trade mark) and 0.4 % of MONTALINE ANP (trademark) have produced with a flow rate of 1200 l / h of air and 200 l / h of liquid foam at a flow rate of 1400 l / h, a lifetime of 20 minutes.

These foam compositions have shown a degreasing efficiency identical to that of Examples 1 to 3 above, concerning the liquid composition according to the invention.

Example 4 Example of a Gel Comprising the Composition According to the Invention

The gel made in this example comprises 1 mol.l ^-1 NaOH, 0.2% by weight of SIMULSOL 98 (Trade Mark), 0.45% by weight of SYNTHIONIC P8020 (Trade Mark) and further comprises an agent thickening. This viscosity agent is xanthan gum of the trademark KELZAN 140X and is added to the composition according to the invention at 1.2% by weight. The gel obtained has a viscosity of 0.8 Pa.s (800 cps) which varies little with temperature.

This gel makes it possible to degrease a TBP-coated metal strip and its derivatives with the same efficiency as the compositions of Examples 1 to 3 above.

EXAMPLE 5 Comparative Example of a Radiochemical Decontamination of a Surface Between a Process According to the Invention and a Process of the Prior Art

This example is a comparative example of the radiochemical decontamination efficiency of a surface by a method of the present invention compared to a radiochemical decontamination according to the prior art.

In this example, the surfaces to be degreased and decontaminated radioactively are substantially cylindrical sections of stainless steel from organic phase probes of a nuclear fuel extraction plant. They were numbered from 1 to 9. These surfaces were in contact with TBP, TPH, HDBP and H ₂ DBP, and their radioactivity is due to more than 98% ruthenium 106 ( ¹⁰⁶ Ru). Before sampling, they were rinsed with concentrated nitric acid and then measured to their radioactivity in ¹⁰⁶ Ru. This activity will be called hereinafter A _o and corresponds to the activity of each surface before radiochemical decontamination.

The radiochemical decontamination processes in this example comprise a degreasing of each surface, or according to a method of the prior art described in Example 1, either according to the method of the invention, and a radioactive decontamination by erosive treatment.

• trempage de la surface dans une solution d'acide nitrique à 5 mol.l^-1 pendant une heure à 50°C sous agitation,
• trempage de la surface dans une solution d'une composition selon l'invention comprenant 0,5 mol.l^-1 de NaOH, 0,12 % en poids de SIMULSOL 98 (marque de commerce) et 0,57 % en poids de SYNTHIONIC P8020 (marque de commerce) à 21°C sans agitation, et
• trempage dans une solution à 0,5 mol.l-1 pendant une heure à 50°C sous agitation.

The method of the invention used in this example comprises the following three steps, in this order:

• soaking the surface in a solution of nitric acid at 5 mol.l ^-1 for one hour at 50 ° C. with stirring,
• dipping the surface in a solution of a composition according to the invention comprising 0.5 mol.l ^-1 of NaOH, 0.12% by weight of SIMULSOL 98 (trademark) and 0.57% by weight of SYNTHIONIC P8020 (trademark) at 21 ° C without agitation, and
• soaking in a 0.5 mol.l-1 solution for one hour at 50 ° C. with stirring.

est calculé pour chaque surface dégraissée.A measurement of the residual radioactive activity Ru ¹⁰⁶ (AR1) was carried out for each surface after degreasing, and before the radioactive decontamination, to measure the decontamination of the surface due to degreasing. From these measurements, a radioactive decontamination factor $\mathrm{FD}\mathrm{1}\mathrm{=}\frac{{\mathrm{AT}}_{\mathrm{o}}}{\mathrm{AR}\mathrm{1}}$

is calculated for each defatted area.

Table 5 below groups together the results of these measurements and calculations and makes it possible to compare the effect of degreasing according to the invention on the radioactive decontamination of a surface, compared to the prior art. <b><u> Table 5: Degreasing effect on decontamination </ u><u> of a surface </ u></b> Prior art Invention Area 1 2 3 4 5 6 7 8 9 A ₀ ¹⁰⁶ Ru x 10 ⁶ Bq 59.9 4.7 - - 6.4 6.3 14.4 6.5 7.6 AR1 ¹⁰⁶ Ru x 10 ⁶ Bq 6 1.37 2.1 3.05 0.29 0.46 0.34 0.29 0.23 FD1 10 3.5 - - 22 14 42 22.5 33 with A ₀ : activity ¹⁰⁶ Ru of the surface before degreasing
AR1: residual activity ¹⁰⁶ Ru of the surface after degreasing
FD1: decontamination factor of the surface after degreasing = $\frac{{\mathrm{AT}}_{\mathrm{o}}}{\mathrm{AR}\mathrm{1}}$

These results show that the residual activity of the surfaces after the degreasing treatment according to the invention is homogeneous and its average value is 0.32 × 10 ⁶ Bq, ie an average FD1 decontamination factor of about 25. degreased surfaces by the method of the prior art show residual activities much higher than those of the invention, ie 6 x 10 ⁶ Bq and 1.37 x 10 ⁶ Bq, ie a decontamination factor of 10 and 3.5 respectively.

The process of the invention therefore appears significantly more effective than the method of the prior art for degreasing a surface, and even for decontaminating this surface radioactively.

After these degreasing treatments, some of these surfaces are subjected to radioactive decontamination by erosive treatment. This treatment erosive is either erosive treatment cerium IV (TE Ce IV) for 2.5 hours, or erosive treatment HF (TE HF) for 5.5 hours, or an erosive treatment ruthenium (TE Ru) for 2 hours, the latter treatment followed by soaking in HNO ₃ for 1 hour. These treatments have been described previously.

est déterminé pour chaque surface. Le facteur de décontamination FDT est celui obtenu pour le dégraissage et la décontamination de chaque surface.After this treatment of radioactive decontamination, weight loss due to erosive treatment Dm and the residual activity ¹⁰⁶ Ru (AR2) of each degreased and decontaminated surface are measured. From this last measure, a total decontamination factor $\mathrm{FDT}\mathrm{=}\frac{{\mathrm{AT}}_{\mathrm{o}}}{\mathrm{AR}\mathrm{2}}$

is determined for each surface. The FDT decontamination factor is the one obtained for the degreasing and decontamination of each surface.

Table 6 below groups these results of measurements and calculations. <b><u> Table 6: Summary of Example 5 </ u></b> Prior art Invention Prior art Invention Prior art Invention Area 2 5 3 6 7 4 8 9 AR1 ¹⁰⁶ Ru x 10 ⁶ Bq 1.37 0.29 2.1 0.46 0.34 3.05 0.29 0.23 Erosive (TE) or specific (TS) treatment TE This IV 2.5 h TE HF 5, 5 h TS Ru = KMnO ₄ AR2 ¹⁰⁶ Ru x 10 ⁶ Bq 0.012 0.0012 0.1 0.016 0.005 0.12 0,011 0.014 FDT 388 3,045 743 800 1,266 480 590 462 Δm (kg) x 10 ^-6 65 57 65 77 78 - - -

These results show a greater efficiency of radiochemical decontamination by the method of the invention than by the method of the prior art. Indeed, the residual activity AR2 ¹⁰⁶ Ru is approximately 10 to 20 times lower for a surface treated by the process of the invention than by the method of the prior art, and whatever the additional treatment used: either erosive for example for Ce IV or Hf, or specific for ruthenium. This improvement can notably be explained by a better preparation of the surfaces to be decontaminated by the degreasing process according to the invention in comparison with the process of the prior art.

These results also show that the degreasing process according to the invention is compatible with erosive treatments.

These results also show that the mass losses Δm measured are comparable for all surfaces, regardless of the degreasing process and the erosive treatment used. There is therefore no change in the erosion kinetics attributable to the degreasing treatment.

Further tests have shown that degreasing according to the invention applied for 3 hours, with the previously described composition, without agitation is as effective as in the presence of agitation. These tests have been extended to 3.5 hours, and showed a maximum efficiency in these conditions of concentration and at a temperature of 25 ° C was obtained in 3 hours, in particular concerning the residual activity of ¹⁰⁶ Ru.

Example 6 Decontamination of an Active Cell with a Gel According to the Invention

In reprocessing plants, the cleaning of the solvent extraction units requires effective degreasing prior to any decontamination in order to extract the TBP and its radiolysis products from the metal surfaces.

The decontaminated cell served as the U / Pu partition (2nd extraction cycle).

The contamination of the floor of this cell was caused by U and Pu laden solvent leaks that were more or less spread by stakeholders.

Part of this solvent was more or less radiolysed, producing tarry black deposits.

The average level of alpha surface contamination was estimated at just under 2 Mbq / cm ² , which, given a floor area of approximately 30 m ² , had a total alpha emitter activity of 0.57 Tbq.

• Pu²³⁸ : 0, 64
• Pu²³⁹ : 81,3
• Pu²⁴⁰ : 14,61
• Pu²⁴¹ : 2,48
• Pu²⁴² : 0,89
• Am²⁴¹ : 0,38

The average isotopic composition (% by weight) determined on the recovered waste is as follows:

• Pu ²³⁸ : 0, 64
• Pu ²³⁹ : 81.3
• Pu ²⁴⁰ : 14.61
• Pu ²⁴¹ : 2.48
• Pu ²⁴² : 0.89
• Am ²⁴¹ : 0.38

The dose rates measured in the cell fluctuated before any decontamination operation, between 0.3 and 10 mGy / h according to the zones.

• Simulsol 98 : 2,0 g/l soit 0,2% en poids
• Synthionic P8020 : 4,8 g/l soit 0,48% en poids
• Montaline ANP : 3,0 g/l soit 0,3% en poids
• NaOH : 1,0 mol/l
• eau qsp : 1 1

The formulation according to the invention used had the following characteristics:

• Simulsol 98: 2.0 g / l or 0.2% by weight
• Synthionic P8020: 4.8 g / l or 0.48% by weight
• Montaline ANP: 3.0 g / l or 0.3% by weight
• NaOH: 1.0 mol / l
• water qsp: 1 1

The gel was applied to the floor (30 m ² ) using a roller per 5 to 6 m ² portion, with particular emphasis on the areas identified as the most radiant.

After a contact time of 2 hours with the floor, the contaminated gel was recovered with a squeegee and then subjected to natural drying in its original pot.

The most contaminated part of the cell (process side) was sanitized in 4 sequences with approximately 2 kg of gel / m ² .

The rest of the cell was treated in 2 passes (20 to 25 m ² per 25 kg of gel, ie almost 1 kg of gel per m ² ).

An acid rinse (10 l of nitric acid) was required to remove the last traces of frost on the floor.

The cell floor is perfectly wettable by nitric acid after degreasing. The nitric acid used was recovered using polypropylene wipes.

The results obtained are summarized in Table 7 below: Reagents used Characteristics of the gel (Volume) (masses) Degreasing gel: 37 liters NaOH: 1480 g HNO ₃ (1 mol / l): 10 liters Surfactants: 285 g Viscosant: 444 g Indicator Before degreasing After degreasing Decontamination factor (*) Mass of Pu (g) 73 < 0.069 > 1050 (**) Alpha surface activity (Bq / cm ² ) 1.9.10 ⁶ 1.7.10 ³ ≅1100

• (*) Les quantités de plutonium déplacé ont été estimées à partir des activités radiochimiques mesurées dans les déchets générés.
• (**) L'activité résiduelle de la cellule était évaluée à l'aide de frottis et de mesures directes.

It should be noted that after degreasing, the absorbed dose rates measured in the cell fell in the interval [2.10 ^-2 , 3.10 ^-2 ] mGy / h, a reduction factor of the dose rate between 10 and 500 .

• (*) The quantities of displaced plutonium were estimated from the radiochemical activities measured in the waste generated.
• (**) The residual activity of the cell was assessed using smears and direct measurements.

Balance of produced waste

In order to be characterized in good conditions, the solids were divided into lots of one hundred grams each.

These batches were then individually measured by neutron counting (measurement of spontaneous fission neutrons) and by gamma spectrometry.

The relative error of this type of measurement determined following a test campaign involving more than a hundred different measurements is 25%.

• pour 13 kg de chiffonnettes (rinçage acide) et de tenues vinyles : 7,2 g Pu
• pour 40 kg de déchets solides composés des gels séchés mélangés à de la bentonite : 65,8 g de Pu.

The waste generated is as follows for 53 kg of waste and 73 g of plutonium:

• for 13 kg of wipes (acid rinsing) and vinyl outfits: 7.2 g Pu
• for 40 kg of solid waste composed of dried gels mixed with bentonite: 65.8 g of Pu.

The application of a surfactant formulation packaged in the form of a gel made it possible to degrease and decontaminate the floor of a cell that has been used for 6 years for the U and Pu partitions (2nd extraction cycle).

• un bon dégraissage de la surface pratiquement sans effet mécanique y compris dans les zones recouvertes de dépôts goudronneux (radiolyse du solvant),
• la mise en suspension des dibutylphosphates métalliques qui sont porteurs de l'essentiel de l'activité radiochimique.

The strengths of this surfactant formulation are:

• a good degreasing of the surface practically without mechanical effect including in the zones covered with tarry deposits (radiolysis of the solvent),
• the suspension of metal dibutylphosphates which carry most of the radiochemical activity.

These results are encouraging for the applications of this surfactant formulation in liquid form.

Claims (24)

1. Degreasing composition, characterised in that it comprises a base, a polyethoxylated fatty alcohol, saturated or unsaturated, a copolymer of ethylene oxide and propylene oxide, and water, in which the base has a concentration in OH^- ions chosen within a range from 0.1 to 1.5 mol.l^-1, in which the polyethoxylated fatty alcohol, saturated or unsaturated, is at a concentration chosen within a range from about 0.01 to about 1.5% by weight, and in which the copolymer of ethylene oxide and propylene oxide has a concentration chosen within a range from about 0.025 to about 1.5% by weight.
2. Composition according to Claim 1, in which the fatty alcohol is chosen from a group comprising lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, arachidyl alcohol, palmitic alcohol, oleic alcohol and linoleic alcohol.
3. Composition according to Claim 1, in which the polyethoxylated fatty alcohol is a compound of the following formula (I):

   

   in which R is an alkyl with a long carbonaceous chain, saturated or unsaturated, comprising from 10 to 24 atoms of carbon, and in which n represents the monomeric unit number of ethylene oxide, n being able to vary from 10 to 30.
4. Composition according to Claim 1, in which the polyethoxylated fatty alcohol is an ether of oleic alcohol and an ethylene polyoxide with 20 monometric units of ethylene oxide, according to the following formula (II):

   
5. Composition according to any one of Claims 1 to 4, in which the copolymer of ethylene oxide and propylene oxide is a block copolymer.
6. Composition according to any one of Claims 1 to 4 in which the copolymer of ethylene oxide and propylene oxide is a block copolymer of the following formula (III):

   
7. Composition according to any one of Claims 1 to 6 and also comprising a foam inhibitor agent.
8. Degreasing liquid comprising a composition according to any one of Claims 1 to 6 comprising about 0.05 to about 0.4% by weight of polyethoxylated fatty alcohol, about 0.025 to about 0.6% by weight of copolymer of ethylene oxide and propylene oxide, about 0.5 to about 1 mol.l^-1 in OH^- ions, and also comprising a foam inhibitor agent.
9. Liquid according to Claim 8, in which the foam inhibitor agent is an alkyl phosphate, branched or not, comprising 4 to 12 atoms of carbon.
10. Degreasing liquid according to one or the other of Claims 8 or 9, in which the inhibitor agent is a branched alkyl phosphate, comprising from 6 to 12 carbon atoms, at a concentration of 0.1 to 0.4% by weight.
11. Degreasing foam comprising a gaseous phase and a degreasing composition according to any one of Claims 1 to 6 and also comprising a foam destabilising agent.
12. Degreasing foam comprising a gaseous phase, and a degreasing composition according to any one of Claims 1 to 6, in which said composition comprises the polyethoxylated fatty alcohol, saturated or unsaturated, at a concentration chosen within a range from about 0.4 to about 1.5% by weight, the copolymer of ethylene oxide and propylene oxide at a concentration chosen within a range from about 0.4 to about 1.5% by weight, said composition also comprising a foam destabilising agent.
13. Degreasing foam according to one or the other of Claims 11 or 12, in which the foam destabilising agent is an alkyl phosphate, branched or not, comprising from 4 to 12 atoms of carbon.
14. Degreasing foam according to one or the other of Claims 11 or 12, in which said foam destabilising agent is a branched alkyl phosphate comprising 6 to 10 atoms of carbon, which is at a concentration of 0.2 to 1.1% by weight in the composition, for a weight ratio, in the composition, of the concentration of polyethoxylated fatty alcohol, saturated or unsaturated, to the concentration of the copolymer of ethylene oxide and propylene oxide, equal to about 1.5.
15. Degreasing gel comprising a degreasing composition according to any one of Claims 1 to 7 and also comprising a viscosity agent.
16. Degreasing gel comprising a degreasing composition according to any one of Claims 1 to 7, in which the polyethoxylated fatty alcohol, saturated or unsaturated, has a concentration chosen within a range from about 0.05 to about 1% by weight, the copolymer of ethylene oxide and propylene oxide has a concentration chosen within a range from about 0.025% to about 0.4% by weight, and also comprising a viscosity agent.
17. Degreasing gel according to one or the other of Claims 15 or 16, in which the viscosity agent is chosen from a group comprising xanthan gum, an aluminium oxide or a silica gel.
18. Degreasing process of a surface, said process comprising putting the surface to be degreased into contact with a composition according to any one of Claims 1 to 7.
19. Degreasing process of a surface, said process comprising putting into contact the surface to be degreased with a liquid according to any one of Claims 8 to 10.
20. Degreasing process of a surface, said process comprising putting into contact the surface to be degreased with a foam according to any one of Claims 11 to 14.
21. Degreasing process of a surface, said process comprising putting into contact the surface to be degreased with a gel according to any one of Claims 15 to 17.
22. Process of radiochemical decontamination of a surface comprising in this order: degreasing of the surface by a process according to any one of Claims 18 to 21, and radioactive decontamination of said degreased surface.
23. Process according to Claim 22, in which the radioactive decontamination is decontamination by chemical erosion or specific treatment of said surface.
24. Process according to Claim 23, in which the chemical erosion of said surface is chosen among a cerium erosive treatment, an HF erosive treatment, or a ruthenium specific treatment.