EP0036359A1 - Process for decontaminating an organic solvent containing plutonium - Google Patents
Process for decontaminating an organic solvent containing plutonium Download PDFInfo
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- EP0036359A1 EP0036359A1 EP81400365A EP81400365A EP0036359A1 EP 0036359 A1 EP0036359 A1 EP 0036359A1 EP 81400365 A EP81400365 A EP 81400365A EP 81400365 A EP81400365 A EP 81400365A EP 0036359 A1 EP0036359 A1 EP 0036359A1
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
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- G21F9/12—Processing by absorption; by adsorption; by ion-exchange
- G21F9/125—Processing by absorption; by adsorption; by ion-exchange by solvent extraction
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- the present invention relates to a plutonium decontamination process of an organic solvent, in particular of a used organic solvent such as tributyl phosphate, which has been used for the uranium-plutonium separation during the reprocessing of irradiated nuclear fuels.
- the object of the process of the invention is precisely a process for decontaminating plutonium from an organic solvent which makes it possible to satisfactorily recover the plutonium contained in this solvent.
- This plutonium decontamination process for a organic solvent is characterized in that it consists in adding to said organic solvent a reducing agent soluble in this organic solvent constituted by a dialkyldithiophosphoric acid, in bringing the organic solvent containing said reducing agent into contact with an acidic aqueous solution, and in separating the aqueous solution containing plutonium of the decontaminated organic solvent.
- a dialkyl di-thiophosphoric acid is used, the alkyl radicals of which have from 1 to 4 carbon atoms, for example diethyldithiohosphoric acid or dibutyldithiophosphoric acid.
- the process as characterized above advantageously takes advantage of the fact that by using a dialkyldithiophosphoric acid as a reducing agent, the plutonium present in this solvent can be reduced under good conditions and then re-extracted in an acidic aqueous solution such as nitric solution.
- dialkyldithiophosphoric acid has certain advantages: it is soluble in the organic solvent whereas the aromatic organic compounds are divided between the aqueous phase and the organic phase, which leads to poorer performance; moreover, the reducing agent of the invention can be used in the presence of nitric acid, which is not the case for dialkylhydroquinones which are destroyed by oxidation in the presence of nitric acid.
- dialkyldithiophosphoric acids which are reducing agents as effective as those currently used, it is possible to reduce the plutonium in the organic phase and to re-extract it in an aqueous phase constituted by an acid solution.
- the acidic aqueous solution is a solution of mineral acid such as nitric acid, hydrochloric acid, sulfuric acid.
- the acidity of this solution can vary over a wide range because the kinetics of plutonium re-extraction is practically unaffected by the acidity of the aqueous phase.
- the reducing agent is diethyldithiophosphoric acid
- an acid solution preferably having an acidity of at least 0.5 N is preferably used since, in this case, the reducing agent is slightly soluble in a weakly acid medium.
- the spent organic solvent containing the reducing agent is brought into contact with the acidic aqueous solution at a temperature above 10 ° C., preferably between 10 and 60 ° C., since the re-extraction rate increases with temperature. .
- the decontaminated solvent is preferably subjected to a complementary purification treatment in order to remove the excess of reducing agent and the oxidation products formed in the solvent from this reducing agent .
- this purification treatment is advantageously carried out by bringing the decontaminated organic solvent into contact with a basic solution such as a sodium carbonate solution.
- washing with a 0.6 M sodium carbonate solution with a stirring time of 5 min, at room temperature, makes it possible to remove more than 99% of the diethyldithiophosphoric acid and more than 90% dibutyldithiophosphoric acid present in an organic solvent.
- this elimination is ensured by carrying out the basic treatment for purifying the decontaminated solvent, in the presence of an oxidizing agent such as sodium nitrite, which is added to the basic solution.
- the disulfide is converted into products soluble in the aqueous phase, which also makes it possible to eliminate, during the basic purification treatment of the decontaminated solvent, the oxidation products of dialkyldithiophosphoric acids.
- This cycle is followed by a solvent regeneration treatment in a mixer-settler, a treatment which consists in successively washing the solvent with a 0.6M sodium carbonate solution, a 1N nitric acid solution and a 1N NaOH solution.
- the solvent subjected to the decontamination treatment is removed before the regeneration treatment in a mixer-settler.
- the decontamination of the solvent is carried out by bringing into contact, with stirring at by means of a rotating magnetic bar, 20 cm 3 of an aqueous solution of nitric acid with 20 cm 3 of spent organic solvent comprising a reducing agent consisting either of diethyldithiophosphoric acid having a purity of approximately 90%, or with dibutyldithiophosphoric acid having a purity of at least 95%.
- the extraction is carried out in a device thermostated by water circulation, and the plutonium content of each of the phases is determined after decantation by alpha counting using a ZnS scintillator or an EMIA type ionization chamber. 2.
- the partition coefficient D of the plutonium is evaluated, which corresponds to the ratio of the plutonium concentration of the organic phase to the plutonium concentration of the aqueous phase.
- This example of treatment of spent solvent applies to the case where it is desired to limit the quantities of reagents added and where there are no heating possibilities.
- 10 -2 M / 1 of diethyldithiophosphoric acid is added to the solvent and the mixture is vigorously stirred in the presence of an aqueous solution of 0.3 N nitric acid at a rate of 0 , 5 volume per volume of solvent. After 60 min, the mixture is allowed to settle.
- the phase assay shows that the plutonium partition coefficient is 2.10 -3 (see Figure 1), ie a 99.6% re-extraction of the plutonium initially present in the solvent. This is then sent to the carbon regeneration unit where the excess diethyldithiophosphoric acid is eliminated.
- One extraction stage is sufficient to re-extract more than 99% of the product after 5 minutes of contact.
- curves 1, 2 and 3 relate respectively to the re-extractions carried out with a concentration of diethyldithiophosphoric acid in the spent solvent of 5.10 -3 M, 10 2M and 2.10 2M, and curve 4 illustrates the variations in the partition coefficient D plutonium for re-extraction carried out under the same conditions, but in the absence of reducing agent.
- diethyldithiophophoric acid is a very effective reducing agent since it takes five minutes to re-extract 97% of the plutonium when the concentration of reducing agent in the organic phase is 2.10 -2 M at room temperature (23 ° VS).
- FIG. 2 whose curves 1, 2 and 3 respectively represent the variations of the coefficient partition D of plutonium as a function of time for re-extractions carried out at 23, 3-0 and 40 ° C.
- the plutonium content of the organic solvent treated in the three examples described is 20 mg / 1.
- the process of the invention thus makes it possible to obtain satisfactory decontamination in plutonium of organic solvents, both acidic and basic. Also, it is of great interest for ensuring the decontamination in plutonium of the used organic solvents before the basic regeneration treatments, which makes it possible to avoid the formation of alkaline radioactive effluents.
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Abstract
L'invention a pour objet un procédé de décontamination en plutonium d'un solvant organique. Ce procédé consiste à ajouter audit solvant organique un agent réducteur soluble dans ce solvant organique, à mettre en contact le solvant organique contenant ledit agent réducteur avec une solution aqueuse acide, et à séparer la solution aqueuse contenant du plutonium du solvant organique décontaminé. Application à la décontamination de solvants organiques tels que le tributylphosphate utilisés pour le retraitement de combustibles irradiés.The invention relates to a plutonium decontamination process of an organic solvent. This process consists in adding to said organic solvent a reducing agent soluble in this organic solvent, in bringing the organic solvent containing said reducing agent into contact with an acidic aqueous solution, and in separating the aqueous solution containing plutonium from the decontaminated organic solvent. Application to the decontamination of organic solvents such as tributylphosphate used for the reprocessing of irradiated fuels.
Description
La présente invention a pour objet un procédé de décontamination en plutonium d'un solvant organique, en particulier d'un solvant organique usé tel que le tributyl phosphate, qui a été utilisé pour la séparation uranium-plutonium lors du retraitement des combustibles nucléaires irradiés.The present invention relates to a plutonium decontamination process of an organic solvent, in particular of a used organic solvent such as tributyl phosphate, which has been used for the uranium-plutonium separation during the reprocessing of irradiated nuclear fuels.
On sait que les solvants organiques tels que le tributyl phosphate qui ont été utilisés pour le retraitement des combustibles nucléaires irradiés, sont dégradés essentiellement par radiolyse alpha et par hydrolyse ; par ailleurs, du plutonium en quantité variable est retenu également dans le solvant organique usé, lorsque le solvant est du tributylphosphate, du plutonium est retenu dans celui-ci probablement en raison de la présence de faibles quantités d'acide dibutyl phosphorique qui forme avec le plutonium des complexes plus stables que les complexes plutonium-tributylphosphate.It is known that organic solvents such as tributyl phosphate which have been used for the reprocessing of irradiated nuclear fuels are degraded essentially by alpha radiolysis and by hydrolysis; moreover, plutonium in variable quantity is also retained in the spent organic solvent, when the solvent is tributylphosphate, plutonium is retained in it probably due to the presence of small amounts of dibutyl phosphoric acid which forms with the plutonium complexes more stable than plutonium-tributylphosphate complexes.
Lorsqu'on purifie ces solvants usés par lavage au moyen de solutions alcalines, on régénère le solvant mais on obtient des solutions de lavage présentant une radioactivité alpha non négligeable, ce qui conduit à des masses importantes d'effluents radioactifs alcalins et augmente de ce fait le volume de déchets radioactifs à traiter.When these used solvents are purified by washing with alkaline solutions, the solvent is regenerated but washing solutions are obtained which have a non-negligible alpha radioactivity, which leads to large masses of alkaline radioactive effluents and thereby increases the volume of radioactive waste to be treated.
Aussi, pour éviter cet inconvénient, il est souhaitable de récupérer aussi quantitativement que possible le plutonium présent dans les solvants organiques. usés, avant de les soumettre au traitement basique de régénération.Also, to avoid this drawback, it is desirable to recover as quantitatively as possible the plutonium present in the organic solvents. worn, before subjecting them to the basic regeneration treatment.
Le procédé de l'invention a précisément pour objet un procédé de décontamination en plutonium d'un solvant organique qui permet de récupérer de façon satisfaisante le plutonium contenu dans ce solvant.The object of the process of the invention is precisely a process for decontaminating plutonium from an organic solvent which makes it possible to satisfactorily recover the plutonium contained in this solvent.
Ce procédé de décontamination en plutonium d'un solvant organique se caractérise en ce qu'il consiste à ajouter audit solvant organique un agent réducteur soluble dans ce solvant organique constitué par un acide dialkyldithiophosphorique, à mettre en contact le solvant organique contenant ledit agent réducteur avec une solution aqueuse acide, et à séparer la solution aqueuse contenant du plutonium du solvant organique décontaminé. Avantageusement, on utilise un acide dialkyl di- thiophosphorique dont les radicaux alkyle ont de 1 à 4 atomes de carbone, par exemple l'acide diéthyldithio hosphorique ou l'acide dibutyldithiophosphorique.This plutonium decontamination process for a organic solvent is characterized in that it consists in adding to said organic solvent a reducing agent soluble in this organic solvent constituted by a dialkyldithiophosphoric acid, in bringing the organic solvent containing said reducing agent into contact with an acidic aqueous solution, and in separating the aqueous solution containing plutonium of the decontaminated organic solvent. Advantageously, a dialkyl di-thiophosphoric acid is used, the alkyl radicals of which have from 1 to 4 carbon atoms, for example diethyldithiohosphoric acid or dibutyldithiophosphoric acid.
Le procédé tel que caractérisé ci-dessus tire avantageusement profit du fait qu'en utilisant comme agent réducteur un acide dialkyldithiophosphorique, on peut réduire dans de bonnes conditions le plutonium présent dans ce solvant et le réextraire ensuite dans une solution aqueuse acide telle qu'une solution nitrique.The process as characterized above advantageously takes advantage of the fact that by using a dialkyldithiophosphoric acid as a reducing agent, the plutonium present in this solvent can be reduced under good conditions and then re-extracted in an acidic aqueous solution such as nitric solution.
En effet, par rapport aux agents réducteurs organiques connus actuellement tels que les-dialkylhydroqui- nones (voir brevet américain 3580705) ou les composés organiques aromatiques (voir brevet français 2212611), l'emploi d'un acide dialkyldithiophosphorique présente certains avantages : celui-ci est soluble dans le solvant organique alors que les composés organiques aromatiques se partagent entre la phase aqueuse et la phase organique, ce qui conduit à de moins bonnes performances ; par ailleurs, l'agent réducteur de l'invention peut être utilisé en présence d'acide nitrique, ce qui n'est pas le cas des dial- kylhydroquinones qui sont détruites par oxydation en présence d'acide nitrique.In fact, compared with currently known organic reducing agents such as dialkylhydroquinines (see American patent 3580705) or aromatic organic compounds (see French patent 2212611), the use of a dialkyldithiophosphoric acid has certain advantages: it is soluble in the organic solvent whereas the aromatic organic compounds are divided between the aqueous phase and the organic phase, which leads to poorer performance; moreover, the reducing agent of the invention can be used in the presence of nitric acid, which is not the case for dialkylhydroquinones which are destroyed by oxidation in the presence of nitric acid.
On pense que la réaction d'oxydation de l'acide dialkyldithiophosphorique correspond à la formation d'un polysulfure suivant le schéma réactionnel suivant :
Ainsi, en utilisant selon l'invention des acides dialkyldithiophosphoriques qui sont des agents réducteurs aussi efficaces que ceux actuellement utilisés, on peut réduire le plutonium en phase organique et le réextraire dans une phase aqueuse constituée par une solution acide.Thus, by using according to the invention dialkyldithiophosphoric acids which are reducing agents as effective as those currently used, it is possible to reduce the plutonium in the organic phase and to re-extract it in an aqueous phase constituted by an acid solution.
Avantageusement, la solution aqueuse acide est une solution d'acide minéral tel que l'acide nitrique, l'acide chlorhydrique, l'acide sulfurique.Advantageously, the acidic aqueous solution is a solution of mineral acid such as nitric acid, hydrochloric acid, sulfuric acid.
L'acidité de cette solution peut varier dans un large intervalle car la cinétique de réextraction du plutonium n'est pratiquement pas affectée par l'acidité de la phase aqueuse.The acidity of this solution can vary over a wide range because the kinetics of plutonium re-extraction is practically unaffected by the acidity of the aqueous phase.
En effet, pour des réextractions du plutonium réalisées en utilisant comme agent réducteur l'acide dibutyldithiophosphorique, des résultats équivalents sont obtenus lorsque l'acidité de la phase aqueuse nitrique varie de 0,01 à 1 N.Indeed, for re-extractions of plutonium carried out using as a reducing agent dibutyldithiophosphoric acid, equivalent results are obtained when the acidity of the nitric aqueous phase varies from 0.01 to 1 N.
Cependant, lorsque l'agent réducteur est l'acide diéthyldithiophosphorique, on utilise de préférence une solution acide ayant une acidité au moins égale à 0,5 N car, dans ce cas, l'agent réducteur est légèrement soluble en milieu faiblement acide.However, when the reducing agent is diethyldithiophosphoric acid, an acid solution preferably having an acidity of at least 0.5 N is preferably used since, in this case, the reducing agent is slightly soluble in a weakly acid medium.
Avantageusement, on réalise la mise en contact du solvant organique usé contenant l'agent réducteur avec la solution aqueuse acide à une température supérieure à l0°C, de préférence comprise entre 10 et 60°C, car la vitesse de réextraction augmente avec la température.Advantageously, the spent organic solvent containing the reducing agent is brought into contact with the acidic aqueous solution at a temperature above 10 ° C., preferably between 10 and 60 ° C., since the re-extraction rate increases with temperature. .
Après réextraction du plutonium présent dans le solvant organique, on soumet de préférence le solvant décontaminé à un traitement de purification complémentaire afin d'éliminer l'excès d'agent réducteur et les produits d'oxydation formés dans le solvant à partir de cet agent réducteur.After re-extracting the plutonium present in the organic solvent, the decontaminated solvent is preferably subjected to a complementary purification treatment in order to remove the excess of reducing agent and the oxidation products formed in the solvent from this reducing agent .
Etant donné que les sels d'acides dithiophospho- riques à chaînes hydrocarbonées courtes (Cl à C4) sont très solubles en milieu basique, ce traitement de purification est avantageusement réalisé par mise en contact du solvant organique décontaminé avec une solution basique telle qu'une solution de carbonate de sodium.Since the salts of dithiophosphoric acids with short hydrocarbon chains (C 1 to C 4 ) are very soluble in basic medium, this purification treatment is advantageously carried out by bringing the decontaminated organic solvent into contact with a basic solution such as a sodium carbonate solution.
En effet, un lavage par une solution de carbonate de sodium 0,6 M, avec un temps d'agitation de 5 mn, à la température ambiante, permet d'éliminer plus de 99% de l'acide diéthyldithiophosphorique et plus de 90% de l'acide dibutyldithiophosphorique présent dans un solvant organique.Indeed, washing with a 0.6 M sodium carbonate solution, with a stirring time of 5 min, at room temperature, makes it possible to remove more than 99% of the diethyldithiophosphoric acid and more than 90% dibutyldithiophosphoric acid present in an organic solvent.
Cependant, ce traitement au moyen d'une solution basique ne permet pas d'éliminer les produits d'oxydation des acides dialkyldithiophosphoriques tels que les disul- fures qui sont au contraire très solubles en phase organique.However, this treatment by means of a basic solution does not make it possible to remove the oxidation products of dialkyldithiophosphoric acids such as the disulphides which are on the contrary very soluble in the organic phase.
Selon l'invention, on assure cette élimination en réalisant le traitement basiquè de purification du solvant décontaminé, en présence d'un agent oxydant tel que le nitrite de sodium, que l'on ajoute à la solution basique.According to the invention, this elimination is ensured by carrying out the basic treatment for purifying the decontaminated solvent, in the presence of an oxidizing agent such as sodium nitrite, which is added to the basic solution.
Dans ces conditions, on oxyde le disulfure selon la réaction :
Ainsi, on transforme le disulfure en produits solubles dans la phase aqueuse, ce qui permet d'éliminer également, lors du traitement basique de purification du solvant décontaminé, les produits d'oxydation des acides dialkyldithiophosphoriques.Thus, the disulfide is converted into products soluble in the aqueous phase, which also makes it possible to eliminate, during the basic purification treatment of the decontaminated solvent, the oxidation products of dialkyldithiophosphoric acids.
D'autres caractéristiques et avantages de l'invention apparaîtront mieux à la lecture des exemples suivants donnés bien entendu à titre illustratif et non limitatif se référant au dessin annexé sur lequel :
- - la figure 1 est un diagramme représentant les variations du coefficient de partage D du plutonium en fonction du temps, pour diverses concentrations en agent réducteur, et
- - la figure 2 est un diagramme représentant les variations du coefficient de partage D du plutonium en fonction du temps pour diverses températures.
- - Figure 1 is a diagram representing the variations in the partition coefficient D of plutonium as a function of time, for various concentrations of reducing agent, and
- - Figure 2 is a diagram showing the variations of the partition coefficient D of plutonium as a function of time for various temperatures.
Ces exemples se rapportent au traitement de décontamination d'un solvant organique usé, constitué par du tributyl phosphate dilué dans du dodécane, la teneur en tributylphosphate du solvant étant de 30%.These examples relate to the decontamination treatment of a spent organic solvent, consisting of tributyl phosphate diluted in dodecane, the tributyl phosphate content of the solvent being 30%.
On précise que ce solvant usé provient d'une installation de retraitement de combustibles irradiés, dans laquelle il a été utilisé pendant cinq à six mois comme solvant d'extraction mis en oeuvre dans des colonnes pulsées. Ceci correspond à la réalisation d'environ une cinquantaine de cycles d'extraction qui comprennent chacun :
- - l'extraction de l'uranium et du plutonium,
- - le lavage du plutonium par de l'acide nitrique,
- - la séparation uranium-plutonium par réduction du plutonium au moyen d'uranium IV,
- - le lavage de l'uranium par du tributylphosphate à 30% dans du dodécane, et
- - deux réextractions de l'uranium.
- - the extraction of uranium and plutonium,
- - washing the plutonium with nitric acid,
- - uranium-plutonium separation by reduction of plutonium by means of uranium IV,
- - washing the uranium with 30% tributylphosphate in dodecane, and
- - two re-extractions of uranium.
Ce cycle est suivi d'un traitement de régénération du solvant en mélangeur-décanteur, traitement qui consiste à laver successivement le solvant par une solution de carbonate de sodium 0,6M, une solution d'acide nitrique 1N et une solution de NaOH 1N.This cycle is followed by a solvent regeneration treatment in a mixer-settler, a treatment which consists in successively washing the solvent with a 0.6M sodium carbonate solution, a 1N nitric acid solution and a 1N NaOH solution.
Dans les exemples suivants, le solvant soumis au traitement de décontamination est prélevé avant le traitement de régénération en mélangeur-décanteur.In the following examples, the solvent subjected to the decontamination treatment is removed before the regeneration treatment in a mixer-settler.
Dans tous ces exemples, on réalise la décontamination du solvant en mettant en contact, sous agitation au moyen d'un barreau magnétique tournant, 20 cm3 d'une solution aqueuse d'acide nitrique avec 20 cm3 de solvant organique usé comprenant un agent réducteur constitué soit par de l'acide diéthyldithiophosphorique ayant une pureté d'environ 90%, soit par de l'acide dibutyldithiophosphorique ayant une pureté d'au moins 95%.In all these examples, the decontamination of the solvent is carried out by bringing into contact, with stirring at by means of a rotating magnetic bar, 20 cm 3 of an aqueous solution of nitric acid with 20 cm 3 of spent organic solvent comprising a reducing agent consisting either of diethyldithiophosphoric acid having a purity of approximately 90%, or with dibutyldithiophosphoric acid having a purity of at least 95%.
L'extraction est réalisée dans un appareil ther- mostaté par circulation d'eau, et la teneur en plutonium de chacune des phases est déterminée après décantation par comptage alpha au moyen d'un scintillateur ZnS ou d'une chambre d'ionisation type EMIA 2.The extraction is carried out in a device thermostated by water circulation, and the plutonium content of each of the phases is determined after decantation by alpha counting using a ZnS scintillator or an EMIA type ionization chamber. 2.
Après détermination de la teneur en plutonium des deux phases, on évalue le coefficient de partage D du plutonium qui correspond au rapport de la concentration en plutonium de la phase organique sur la concentration en plutonium de la phase aqueuse.After determining the plutonium content of the two phases, the partition coefficient D of the plutonium is evaluated, which corresponds to the ratio of the plutonium concentration of the organic phase to the plutonium concentration of the aqueous phase.
Cet exemple de traitement de solvant usé s'applique au cas où on désire limiter les quantités de réactifs ajoutés et où on ne dispose pas de possibilités de chauffage. Après la partition uranium-plutonium lors du retraitement des combustibles irradiés, on ajoute au solvant 10-2 M/1 d'acide diéthyldithiophosphorique et on agite énergiquement en présence d'une solution aqueuse d'acide nitrique 0,3 N à raison de 0,5 volume par volume de solvant. Après 60 mn, on laisse décanter le mélange. Le dosage des phases permet de constater que le coefficient de partage du plutonium est de 2.10-3 (voir figure 1), soit une réextraction de 99,6% du plutonium initialement présent dans le solvant. Celui-ci est ensuite envoyé à l'unité de régénération carbonique où l'excès d'acide diéthyldithiophosphorique est éliminé. Un étage d'extraction suffit pour réextraire plus de 99% du produit après 5mn de contact.This example of treatment of spent solvent applies to the case where it is desired to limit the quantities of reagents added and where there are no heating possibilities. After the uranium-plutonium partition during the reprocessing of irradiated fuels, 10 -2 M / 1 of diethyldithiophosphoric acid is added to the solvent and the mixture is vigorously stirred in the presence of an aqueous solution of 0.3 N nitric acid at a rate of 0 , 5 volume per volume of solvent. After 60 min, the mixture is allowed to settle. The phase assay shows that the plutonium partition coefficient is 2.10 -3 (see Figure 1), ie a 99.6% re-extraction of the plutonium initially present in the solvent. This is then sent to the carbon regeneration unit where the excess diethyldithiophosphoric acid is eliminated. One extraction stage is sufficient to re-extract more than 99% of the product after 5 minutes of contact.
En effectuant plusieurs réextractions avec des concentrations en acide diéthyldithiophosphorique de la phase organique de 5.10 3M, 10-2M et 2.10-2M et des temps variables, on obtient les courbes de la figure 1 qui représentent les variations du coefficient de partage D du plutonium en fonction de la durée de réextraction (en minutes).By carrying out several re-extractions with diethyldithiophosphoric acid concentrations of the organic phase of 5.10 3M, 10 -2 M and 2.10 -2 M and variable times, the curves of FIG. 1 are obtained which represent the variations in the partition coefficient D of the plutonium depending on the re-extraction time (in minutes).
Sur cette figure, les courbes 1, 2 et 3 se rapportent respectivement aux réextractions réalisées avec une concentration en acide diéthyldithiophosphorique du solvant usé de 5.10-3M, 10 2M et 2.10 2M, et la courbe 4 illustre les variations du coefficient de partage D du plutonium pour une réextraction réalisée dans les mêmes conditions, mais en l'absence d'agent réducteur.In this figure,
Au vu de cette figure, on constate que l'addition d'acide diéthyldithiophosphorique au solvant organique usé permet d'éliminer pratiquement la totalité du plutonium.In view of this figure, it can be seen that the addition of diethyldithiophosphoric acid to the spent organic solvent makes it possible to eliminate practically all of the plutonium.
Enfin, on remarque que la vitesse d'extraction augmente de façon importante avec la concentration en agent réducteur.Finally, we note that the extraction speed increases significantly with the concentration of reducing agent.
On constate ainsi que l'acide diéthyldithiopho phorique est un agent réducteur très efficace puisqu'il suffit de cinq minutes pour réextraire 97% du plutonium lorsque la concentration en agent réducteur de la phase organique est de 2.10-2M à température ambiante (23°C).It can thus be seen that diethyldithiophophoric acid is a very effective reducing agent since it takes five minutes to re-extract 97% of the plutonium when the concentration of reducing agent in the organic phase is 2.10 -2 M at room temperature (23 ° VS).
Cet exemple s'applique au cas où on dispose d'un système de chauffage et où on désire limiter le temps de contact entre phase aqueuse et phase organique. On pourra également se permettre d'utiliser de faibles quantités de réactif. Après avoir chauffé à 40°C le solvant usé sortant du cycle de partition uranium-plutonium, on y ajoute 5.10-3 M/1 d'acide dibutyldithiophosphorique en présence d'une solution aqueuse d'acide nitrique 0,05 N également portée à 40°C. Après 5mn de contact, on décante les phases et on trouve que le coefficient de partage du plutonium est de 0,0014 (voir figure 2). On a réextrait ainsi 99,7% du plutonium en ayant opéré avec un rapport de volume phase organique sur phase aqueuse égal à 2. Comme dans l'exemple 1, le solvant est alors envoyé au traitement carbonique, cependant, il faut deux étages de réextraction pour éliminer 99% de l'acide dibutyldithiophosphorique avec un temps de contact de 5 mn.This example applies to the case where there is a heating system and where it is desired to limit the contact time between the aqueous phase and the organic phase. We can also afford to use small amounts of reagent. After having heated the spent solvent leaving the uranium-plutonium partition cycle to 40 ° C., 5.10 -3 M / 1 of dibutyldithiophosphoric acid is added thereto in the presence of an aqueous 0.05 N nitric acid solution. brought to 40 ° C. After 5 minutes of contact, the phases are decanted and the plutonium partition coefficient is found to be 0.0014 (see Figure 2). 99.7% of the plutonium was thus reextracted, having operated with an organic phase to aqueous phase volume ratio equal to 2. As in Example 1, the solvent is then sent to carbon dioxide treatment, however, two stages of re-extraction to remove 99% of dibutyldithiophosphoric acid with a contact time of 5 min.
En effectuant plusieurs réextractions du plutonium à des températures de 23, 30 et 40°C et en déterminant dans chaque cas le coefficient de partage D du plutonium, on obtient la figure 2 dont les courbes 1, 2 et 3 représentent respectivement les variations du coefficient de partage D du plutonium en fonction du temps pour des réextractions réalisées à 23, 3-0 et 40°C.By carrying out several re-extractions of the plutonium at temperatures of 23, 30 and 40 ° C and by determining in each case the partition coefficient D of the plutonium, we obtain FIG. 2 whose
Au vu de cette figure, on constate que la vitesse de réextraction augmente avec la température. Ainsi, à 40°C (courbe 3), il faut moins de 5 mn pour obtenir un coefficient de partage du plutonium inférieur à 10-3.In view of this figure, it can be seen that the re-extraction speed increases with temperature. Thus, at 40 ° C (curve 3), it takes less than 5 min to obtain a plutonium partition coefficient of less than 10 -3 .
Cet exemple s'applique au cas où la température dans l'installation de retraitement est voisine de 30°C. Dans ce cas, on opère sans chauffer avec une concentration en acide dibutyldithiophosphorique de 5.10-3 M. Après 10 mn de temps de contact, on trouve un coefficient de partage du plutonium égal à 0,003 (voir figure 2) et on a éliminé du solvant 99,7% du plutonium en ayant utilisé un volume de solution aqueuse 0,05 N en acide nitrique pour un volume de solvant. Celui-ci est alors envoyé à l'unité de régénération carbonique. L'élimination de 99% de l'acide dibutyldithiophosphorique nécessite deux contacts de 5 mn comme dans l'exemple 2.This example applies to the case where the temperature in the reprocessing installation is close to 30 ° C. In this case, the operation is carried out without heating with a concentration of dibutyldithiophosphoric acid of 5.10 -3 M. After 10 min of contact time, a plutonium partition coefficient equal to 0.003 is found (see FIG. 2) and the solvent has been removed. 99.7% of the plutonium having used a volume of 0.05 N aqueous solution of nitric acid for a volume of solvent. This is then sent to the carbon regeneration unit. The elimination of 99% of the dibutyldithiophosphoric acid requires two contacts of 5 min as in Example 2.
La teneur en plutonium du solvant organique traité dans les trois exemples décrits est de 20 mg/1.The plutonium content of the organic solvent treated in the three examples described is 20 mg / 1.
Le procédé de l'invention permet ainsi d'obtenir une décontamination satisfaisante en plutonium de solvants organiques aussi bien acides que basiques. Aussi, il présente un grand intérêt pour assurer la décontamination en plutonium des solvants organiques usés avant les traitements basiques de régénération, ce qui permet d'éviter la formation d'effluents radioactifs alcalins.The process of the invention thus makes it possible to obtain satisfactory decontamination in plutonium of organic solvents, both acidic and basic. Also, it is of great interest for ensuring the decontamination in plutonium of the used organic solvents before the basic regeneration treatments, which makes it possible to avoid the formation of alkaline radioactive effluents.
Par ailleurs, il permet une récupération quantitative du plutonium retenu dans un solvant usé tout en ne nécessitant que peu de réactif.Furthermore, it allows quantitative recovery of the plutonium retained in a spent solvent while requiring only a small reagent.
Claims (11)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8005626A FR2478363B1 (en) | 1980-03-13 | 1980-03-13 | PROCESS FOR PLUTONIUM DECONTAMINATION OF AN ORGANIC SOLVENT |
| FR8005626 | 1980-03-13 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0036359A1 true EP0036359A1 (en) | 1981-09-23 |
| EP0036359B1 EP0036359B1 (en) | 1984-06-13 |
Family
ID=9239634
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP81400365A Expired EP0036359B1 (en) | 1980-03-13 | 1981-03-10 | Process for decontaminating an organic solvent containing plutonium |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4404130A (en) |
| EP (1) | EP0036359B1 (en) |
| JP (1) | JPS56143999A (en) |
| DE (1) | DE3164062D1 (en) |
| FR (1) | FR2478363B1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4595529A (en) * | 1984-03-13 | 1986-06-17 | The United States Of America As Represented By The Department Of Energy | Solvent wash solution |
| FR2665975A1 (en) * | 1990-08-14 | 1992-02-21 | Doryokuro Kakunenryo Kaithasu | PROCESS FOR EXTRACTING AND SEPARATING EXHAUSTED SOLVENT PRODUCED IN A NUCLEAR FUEL CYCLE. |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4681705A (en) * | 1985-10-15 | 1987-07-21 | Carolina Power & Light Company | Decontamination of radioactively contaminated liquids |
| US4855081A (en) * | 1988-06-07 | 1989-08-08 | Nutech, Inc. | Method for decontaminating conventional plastic materials which have become radioactively contaminated, and articles |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3580705A (en) * | 1968-10-02 | 1971-05-25 | Atomic Energy Commission | Selective stripping of plutonium from organic extracts |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2212611B1 (en) * | 1972-12-28 | 1975-11-07 | Commissariat Energie Atomique |
-
1980
- 1980-03-13 FR FR8005626A patent/FR2478363B1/en not_active Expired
-
1981
- 1981-03-10 EP EP81400365A patent/EP0036359B1/en not_active Expired
- 1981-03-10 DE DE8181400365T patent/DE3164062D1/en not_active Expired
- 1981-03-10 JP JP3445381A patent/JPS56143999A/en active Pending
- 1981-03-11 US US06/242,656 patent/US4404130A/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3580705A (en) * | 1968-10-02 | 1971-05-25 | Atomic Energy Commission | Selective stripping of plutonium from organic extracts |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4595529A (en) * | 1984-03-13 | 1986-06-17 | The United States Of America As Represented By The Department Of Energy | Solvent wash solution |
| FR2665975A1 (en) * | 1990-08-14 | 1992-02-21 | Doryokuro Kakunenryo Kaithasu | PROCESS FOR EXTRACTING AND SEPARATING EXHAUSTED SOLVENT PRODUCED IN A NUCLEAR FUEL CYCLE. |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0036359B1 (en) | 1984-06-13 |
| DE3164062D1 (en) | 1984-07-19 |
| FR2478363B1 (en) | 1987-05-07 |
| US4404130A (en) | 1983-09-13 |
| JPS56143999A (en) | 1981-11-10 |
| FR2478363A1 (en) | 1981-09-18 |
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