Patent Number: 
Section: description

Many other advantages of the present invention will become clear by reading the following examples, provided evidently as illustrative but non-limiting. Comparative Example of Degreasing This example is a comparative example of the degreasing efficiency of a composition and a process in conformity with the invention relating to solutions and a process of prior art. In this example, the surface to be degreased is an austenitic steel blade covered with about 1 g/cm2 of one of the following mixtures A and B which represent the greasy 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 H2MBP. 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 H2MBP. The process according to prior art comprises the following sequences, in this order, and with agitation of the solutions used, by means of a magnetic stirring bar, at 500 rev/min: soaking of each blade in a solution of nitric acid at 5 mol.lxe2x88x921 at a temperature of 50xc2x0 C. for 60 minutes, rinsing of each blade with water at a temperature of 50xc2x0 C. for 5 minutes, soaking of each blade in a caustic soda solution at 5 mol.lxe2x88x921 at a temperature of 50xc2x0 C. for 120 minutes, rinsing of each blade with water at a temperature of 50xc2x0 C. for 5 minutes, soaking of each blade in a solution of nitric acid at 5 mol.lxe2x88x921 at a temperature of 50xc2x0 C. for 60 minutes, and rinsing of each blade with water at a temperature of 50xc2x0 C. for 5 minutes. The process according to the invention comprises soaking each blade in a composition according to the invention, without agitation, at a temperature of 20xc2x0 C. In this example, two different compositions according to the invention are used. Each of these two compositions comprises 0.12% by weight of ether of oleic alcohol and polyoxyethylene glycol with 20 units of ethylene oxide, Trademark SIMULSOL 98 manufactured by the company SEPPIC (formula (I) above) and 0.57% by weight of block copolymer with 45 ethylene oxides and 9 propylene oxides Trademark SYNTHIONIC P8020 manufactured by the company WITCO (formula (II) above). The first of these two compositions, hereinafter called composition 1, comprises 0.5 mol.lxe2x88x921 of NaOH, and the second of these compositions, hereinafter called composition 2 comprises 1 mol.lxe2x88x921 of NaOH. The cloud point of these two compositions is 38xc2x0 C. The degreasing efficiency of these two processes was compared by measuring the contact angle between an aqueous solution and each degreased metallic blade, using the SCHULTZ method, and by measuring the minimum contact time for total degreasing of these blades. A wetting angle equal to 0 represented total degreasing of the surface, that is to say recuperation of the grease from the metallic surface. In order to displace this grease, the aqueous solution must allow its micellisation. Table 1 below groups the results of these measurements: The results of this example show that the degreasing of each blade, by the prior art process, covered with mixture A or mixture B, is only partial for a total time of 255 minutes for this process, at a temperature of 50xc2x0 C. and for very concentrated solutions of nitric acid and caustic soda. Whilst the process and the composition according to the invention provide total degreasing of the blades, whatever 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 prior art, and at ambient temperature. In addition, supplementary trials have shown that a blade degreased with composition 1 or 2 is perfectly wettable by 5N nitric acid, which is not the case for a blade degreased by the solutions and process of prior art. Kinetics of Degreasing of a Surface with a Composition According to the Invention In this example, a metallic blade covered with 0.75 g/cm2 of a mixture C of solvent TPH+TBP+HDBP+H2MBP comprising respectively 70; 27; 1.8 and 1.2% by weight of these solvents and a metallic blade covered by 1.2 mg/cm2 of a mixture D of solvent TBP+HDBP+H2MBP comprising respectively 90; 6 and 4% by weight of these solvents, were degreased by soaking without agitation in an aqueous solution of the composition according to the invention comprising 0.5 mol.lxe2x88x921 of caustic soda, 0.12% by weight of SIMULSOL 98 (Trademark) and 0.57% by weight of SYTHIONIC P8020 (Trademark). Degreasing was carried out at ambient temperature. The degreasing kinetics were followed by measuring over time, and at regular intervals, the surface tension xcex3cosxcex8 of each blade using the WILHELMY submerged blade method and thus determining the corresponding cosxcex8. Table 2 below groups the results of this example. According to the results in this example, it appears that about 120 minutes are required for complete degreasing (cosxcex8=1) of the blade covered with mixture C and 180 minutes for complete degreasing of the blade covered with mixture D under the same conditions as for the composition according to the invention. Identical kinetic trials corresponding to those of this example were carried out with a concentration of caustic soda, in the composition according to the invention, of 1 mol.lxe2x88x921. The degreasing kinetics were much faster, since 30 minutes were sufficient for complete degreasing of the blade covered with mixture D. These trials showed that the solubility of mixture D is 305 times higher with caustic soda at 1 mol.lxe2x88x921 than with caustic soda at 0.5 mol.l1xe2x88x92. In comparison, treatment of the same blades by caustic soda at a concentration of 0.5 mol.lxe2x88x921, without surfactant with agitation of 500 rev/min, for 120 minutes, did not obtain complete degreasing of the blades. In fact, the cosxcex8 obtained by this treatment was only 0.81. Complementary tests showed that a dilution of a composition according to the invention by a factor of 2 raised the degreasing time by the same factor. Efficiency of Degreasing of a Surface with a Slightly Foaming Composition According to the Invention This example illustrates the efficiency of degreasing a surface by the slightly foaming solutions according to the invention. In this example, the compositions used comprised a constant caustic soda concentration equal to 0.5 mol. lxe2x88x921, and a constant concentration of ether of oleic alcohol and polyoxyethylene glycol equal to 0.2% by weight. The fatty alcohol used was SIMULSOL 98 (Trademark) manufactured by the SEPPIC company. These compositions comprise a variable concentration of block copolymer of the Trademark SYNTHIONIC P8020 manufactured by the WITCO company, and also comprise a foam inhibitor again in a concentration which is also variable. This foam inhibitor agent is an alkyl phosphate of the Trademark MONTALINE ANP manufactured by the SEPPIC company. The surface to be degreased is a steel blade covered with 1 mg/cm2 of TBP. The degreasing was carried out at ambient temperature and without agitation of the degreasing solutions. The degreasing efficiency of these solutions was evaluated by measuring the cloud point (in xc2x0 C.) of each of these solutions, by measurement of the time, in minutes, needed for each of these solutions to degrease the metallic blade completely to obtain a surface tension such that cosxcex8≅1, and by measurement of the quantity (in g/l) of TBP which each solution can dissolve. The following table 3 groups the results of this example. These results show that for a concentration of caustic soda of 0.5 mol.lxe2x88x921 and for a concentration of SIMULSOL 98 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 to be the most efficient for dissolving TBP. Trials for putting these compositions into circulation, by airlift, showed that the production of foam is sufficiently low not to choke the airlift separator trap. Example of a Foam Comprising the Composition According to the Invention The solutions used to form the foam of this example comprise. a concentration of SIMULSOL 98 (Trademark) greater than or equal to 0.4% by weight, a concentration of SYNTHIONIC (Trademark) greater than 0.26% by weight, and also comprise a foam destabilising agent. This destabilising agent is MONTALINE ANP (Trademark) described above as a foam inhibitor. In this example, all the compositions comprise a constant concentration of caustic soda equal to 0.75 mol.lxe2x88x921. Foams were produced from these compositions by a static generator composed of a cylinder 120 mm long and 8 mm in diameter filled with 3.24 g of porous packing of the FORAFLON type (Trademark). The generator was fed with each foaming solution by using a gear pump with flow rate of liquid of 23 to 28 l/hr and of air of 88 l/hr in normal conditions of temperature and pressure. The foams were obtained at a flow rate of 120 to 130 l/hr, with expansion ranging from 6 to 7 and a lifetime of 15xc2x12 minutes. In this example, measurements were taken of the quantity of TBP and its derivatives HDBP and H2MPB (in g/kg) which can be dissolved in different compositions according to the invention. Tests were carried out at ambient temperature. Table 4 below groups the results obtained in this example. These results show that when the levels of SIMULSOL 98 and SYNTHIONIC P8020 are raised, the dissolving of TBP is raised. Supplementary tests with a composition comprising 0.75 mol.lxe2x88x921 NaOH, 0.8% by weight of SIMULSOL 98 (Trademark), 0.6% by weight of SYNTHIONIC P8020 (Trademark) and 0.4% of MONTALINE ANP (Trademark) made it possible to produce, with a flow rate of 1200 l/hr of air and 200 l/hr of liquid, a foam with a flow rate of 1400 l/hr, with a lifetime of 20 minutes. These foam compositions showed a degreasing efficiency identical to that of the preceding examples 1 to 3, concerning the liquid composition according to the invention. Example of a Gel Comprising the Composition According to the Invention The gel produced in this example comprises 1 mol.lxe2x88x921 NaOH, 0.2% by weight of SIMULSOL 98 (Trademark), 0.45% by weight of SYNTHIONIC P8020 (Trademark) and also comprises a viscosity agent. This viscosity agent is xanthan gum KELZAN 140X (Trademark) 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 metallic blade covered with TBP and its derivatives with the same efficiency as the compositions of examples 1 to 3 above. Comparative Example of Radiochemical Decontamination of a Surface Between a Process According to the Invention and a Process of Prior Art This example is a comparative example of the efficiency of radiochemical decontamination of a surface by a process of the present invention compared with radiochemical contamination according to prior art. In this example, the surfaces to be degreased and to be radioactively decontaminated are approximately cylindrical sections in stainless steel coming from organic phase probes from a nuclear fuel extraction plant. They are numbered from 1 to 9. These surfaces were put in contact with TBP, TPH, HDBP and H2DBH, and their radioactivity is due to more than 98% of ruthenium 106 (106Ru). Before taking samples, they underwent a rinsing with concentrated nitric acid and then measurement of their radioactivity in 106Ru. Hereinafter this radioactivity will be named Ao and will correspond to the activity of each surface before radiochemical decontamination. The radiochemical decontamination processes in this example comprise a degreasing of each surface, either according to a prior art process described in example 1, or according to the process of the invention, and radioactive decontamination by erosive treatment. The process according to the invention used in this example comprises the following three stages, in this order: soaking of the surface in a nitric acid solution at 5 mol.lxe2x88x921 for one hour at 50xc2x0 C. with agitation, soaking of the surface in a solution according to the invention comprising 0.5 mol.lxe2x88x921 of NaOH, 0.12% by weight of SIMULSOL 98 (Trademark) and 0.57% by weight of SYNTHIONIC P8020 (Trademark) at 21xc2x0 C. without agitation, and soaking in a solution at 0.5 mol.lxe2x88x921 for one hour at 50xc2x0 C. with agitation. Measurement of the residual radioactive activity 106Ru (AR1) was carried out for each surface after degreasing, and before radioactive decontamination, to measure the decontamination of the surface due to degreasing. Working from these measurements, a radioactive decontamination factor FD1=Ao/AR1 was calculated for each degreased surface. Table 5 groups the results of these measurements and makes it possible to compare the degreasing effect of the invention on radioactive decontamination of a surface, compared with prior art. with A0: 106Ru activity of the surface before degreasing AR1 : 106Ru residual activity of the surface after degreasing FD1 : decontamination factor of the surface after degreasing=Ao/AR1 These results show that the residual activity of the surfaces after degreasing treatment according to the invention is homogeneous and its average value is 0.32xc3x97106 Bq, that is an average decontamination factor FD1 of the order of 25. The surfaces degreased by the prior art process show much higher residual activities than those of the invention, such as 6xc3x97106 Bq and 1.37xc3x97106 Bq, that is to say a decontamination factor of 10 and 3.5 respectively. The process according to the invention therefore seems significantly more efficient than the prior art process for degreasing a surface, and even for radioactive decontamination of this surface. After these degreasing treatments, some of the surfaces underwent radioactive decontamination by an erosive treatment. This erosive treatment was either a cerium IV erosive treatment (T.E. Ce IV) for 2.5 hours, or an HF erosive treatment (T.E. HF) for 5.5 hours, or a ruthenium erosive treatment (T.E. Ru) for 2 hours, this latter treatment being followed by soaking in HNO3 for 1 hour. These treatments have been described above. After this radioactive decontamination treatment, the loss in weight xcex94m due to the erosive treatment and the residual activity 106Ru (AR2) of each surface degreased and decontaminated were measured. From this latter measurement, a total decontamination factor FDT=A0/AR2 was determined for each surface. The FDT decontamination factor is that obtained for degreasing and decontamination of each surface. Table 6 below groups the results of these measurements and calculations. These results demonstrate greater efficiency of radiochemical decontamination by the process according to the invention than by the prior art process. In fact, the residual activity AR2 106Ru is about 10 to 20 times lower for a surface treated by the process according to the invention than by the prior art process, whatever the complementary treatment used: whether it be erosive, for example for Ce IV or HF, or specific for ruthenium. This improvement can be explained in particular by better preparation of the surfaces to be decontaminated by the degreasing process according to the invention compared with the prior art process. These results also show that the degreasing process according to the invention is compatible with erosive treatments. These results also show that the weight losses xcex94m measured are comparable for all surfaces, whatever the degreasing process and erosive treatment used. Thus there is no modification of erosion kinetics to be attributed to the degreasing treatment. Complementary tests showed that a degreasing according to the invention applied for 3 hours, with the composition described above, without agitation, is just as efficient as with agitation. These tests were prolonged up to 3.5 hours, and showed that maximum efficiency, in these concentration conditions, and at a temperature of 25xc2x0 C., was obtained in 3 hours, in particular concerning the residual activity of 106Ru. Decontamination of an Active Cell by a Gel According to the Invention In reprocessing plants, the cleaning of extraction units by solvent requires, before any decontamination, efficient degreasing so as to extract the TBP and its radiolysis products from the metallic surfaces. The decontaminated cell had the function of partition U/Pu (2nd extraction cycle). Contamination of the floor of this cell was caused by leaks of solvent containing U and Pu which were more or less spread by the interveners. Part of this solvent was more or less radiolysed, which produced the black tarry deposits. The average level of alpha surface contamination was estimated at a little below 2 Mbq/cm2, that is, taking into account a floor surface of about 30 m2, a total activity of alpha emitters of 0.57 Tbq. The average isotopic composition, (% by weight) determined on the recuperated wastes was as follows: Pu238: 0.64 Pu239: 81.3 Pu240: 14.61 Pu241: 2.48 Pu242: 0.89 Am241: 0.38 The dose rates measured in the cell fluctuated before each decontamination operation, between 0.3 and 10 mGy/hr according to the zones. The formula according to the invention used had the following characteristics: Simulsol 98: 2.0 g/l; 0.2% by weight Synthionic P8020: 4.8 g/l; 0.48% by weight Montaline ANP: 3.0 g/l; 0.3% by weight NaOH: 1.0 mol/l water qsp: 1 l The gel was applied on the floor (30 m2) using a roller per portion of 5 to 6 m2, insisting in particular on the zones identified as being the most irradiating. After a contact time of 2 hours with the flooring, the contaminated gel was recuperated using a scraper and then submitted to natural drying in its original pot. The most contaminated part of the cell (process side) was cleaned in 4 sequences without about 2 kg gel/m2. The rest of the cell was treated with 2 sequences (20 to 25 m2 per 25 kg gel, that is about 1 kg gel per m2). An acid rinsing (10 l nitric acid) was necessary to eliminate the final traces of gel present on the flooring. The cell flooring was perfectly wettable by nitric acid after the degreasing. The nitric acid used was recuperated with the aid of polypropylene cloths. The results obtained are summarised in table 7 below: It is to be noted that after degreasing, the absorbed dose rates measured in the cell had fallen in the interval [2.10xe2x88x922, 3.10xe2x88x922]mGy/hr, that is a reduction factor of the dose rate of between 10 and 500. Evaluation of the Wastes Produced In order to be studied under good conditions, the solids were divided into batches weighing about one hundred grams each. These batches were then measured individually by neutron counting (measurement of neutrons from spontaneous fission) and by gamma spectrometry. The relative error of this type of measurement determined after a series of tests involving over a hundred different measurements is 25%. The evaluation of the wastes generated is as follows for 53 kg of wastes and 73 g of plutonium: for 13 kg of cloths (acid rinsing) and vinyl clothing: 7.2 g Pu. for 40 kg of solid wastes composed of dried gels mixed with bentonite: 65.8 g of Pu. The application of a surfactant formulation conditioned in gel form made it possible to degrease and decontaminate the floor of a cell which had been used for 6 years for U and Pu partitions (2nd extraction cycle). The strong points of this surfactant formulation are as follows: good degreasing of the surface practically without any mechanical effect even in the zones covered with tarry deposits (radiolysis of the solvent), putting into suspension the metal dibutyl phosphates which are the carriers of the main part of the radiochemical activity. These results are encouraging for the applications of this surfactant formulation under liquid form.