EP0192543A1 - Process for conditioning radioactive or toxic waste in epoxyde resins, and polymerisable mixture with two liquid constituents for use in this process - Google Patents

Abstract

The subject of the invention is a process for packaging radioactive or toxic waste in epoxy resins and a polymerizable mixture with two liquid constituents which can be used in this process. This process consists in incorporating the waste into a polymerizable mixture comprising at least one epoxy resin, pitch, and at least one hardener of the epoxy resin, and allowing the mixture thus obtained to harden. Generally, the mixture comprises at most 50% by weight of pitch and it can be used for the treatment of radioactive waste constituted by large objects and organic liquids.

Description

The present invention relates to a process for packaging radioactive or toxic waste in epoxy resins.

In recent years, processes have been developed for conditioning radioactive or toxic waste in thermosetting resins, which consist in introducing the waste into a polymerizable mixture consisting for example of an epoxy resin and a hardener, and then letting the resin polymerize for obtain a solid block inside which radioactive or toxic waste is confined.

More specifically, the present invention relates to polymerizable mixtures of this type based on epoxy resins, which can be used in particular for the treatment of certain wastes such as large solid wastes and organic liquids.

Indeed, the packaging of solid radioactive waste of relatively large dimensions poses problems due to the phenomenon of shrinkage of the epoxy resin during its hardening. These problems have been solved so far by adding to the polymerizable mixture an inert filler constituted for example by sand, as indicated in French patent FR-A 2 36 ₁ 725, but this leads to difficulties in implementing the method.

In the case of contaminated organic liquids, these can be packaged in thermosetting resins, as described in French patent FR-A 2 230 041, but the treatment of such liquids however poses problems of obtaining a homogeneous mixture.

The present invention specifically relates to a polymerizable mixture of epoxy resin and hardener further comprising a particular additive, which solves the problems posed by the packaging of waste consisting of large objects or organic liquids.

The method according to the invention for conditioning radioactive or toxic waste is characterized in that it consists in incorporating said waste into a polymerizable mixture comprising at least one epoxy resin, pitch and at least one hardener of the epoxy resin. and allow the mixture to harden to obtain a solid block.

• - 30% à 45% en poids de résine époxyde,
• - 30% à 50% en poids de brai,
• - 20% à 25% en poids de durcisseur.

According to a preferred mode, the mixture is composed of:

• - 30% to 45% by weight of epoxy resin,
• - 30% to 50% by weight of pitch,
• - 20% to 25% by weight of hardener.

Generally, the mixture comprises at most 50% by weight of pitch.

The addition of pitch to the polymerizable mixtures based on epoxy resin used in the prior art, makes it possible in particular to increase the fluidity of the polymerizable composition, which makes it more suitable for coating large solid waste such as as filter cartridges, tools, metal shavings placed in a basket, etc. The presence of pitch also improves the compatibility of epoxy resins with organic liquids such as waste oils, distillation residues, scintillation liquids, and solvents such as tributylphosphate or xylene, which are generally immiscible with thermosetting resins.

Thus, the polymerizable mixture of the invention is of great interest for the treatment of large solid waste and organic liquids. Furthermore, since the presence of pitch does not harm the qualities of the solid block finally obtained, the polymerizable mixtures of the invention can be used for the conditioning of other waste, which makes it possible to lower the treatment costs because the price of pitch is lower than that of epoxy resins.

The pitches which can be used in the invention may be pitches originating from the distillation of carbonization tars, in particular tars with a low content of insoluble products. These pitches must be compatible with the epoxy resin and the hardener used and they are also chosen according to the nature of the waste treated.

By way of example, it is possible to use the pitch sold under the reference 730130 which is a fluxed coal pitch without volatile fractions originating from the treatment of tars with low contents of insoluble products.

• - teneur en eau : traces,
• - densité à +20°C : 1,184,
• - viscosité à 30°C : 30 poises,
• - distillation fractionnée :
• . fraction avant 200 °C : <0,5%
• . " de 200 à 250°C : 6%
• . " de 250 à 300°C : 18 %
• . " de 300 à 350°C : 16 %
• - résidu de distillation : 60%
• - insoluble dans le benzène : 10%.

The technical characteristics of this pitch are as follows:

• - water content: traces,
• - density at + 20 ° C: 1.184,
• - viscosity at 30 ° C: 30 poises,
• - fractional distillation:
• . fraction before 200 ° C: <0.5%
• . "from 200 to 250 ° C: 6%
• . "from 250 to 300 ° C: 18%
• . "from 300 to 350 ° C: 16%
• - distillation residue: 60%
• - insoluble in benzene: 10%.

It is also possible to use the pitch marketed under the reference 710/25 which differs from the pitch 730/30 by its viscosity which is 25 poises and by different distillation fractions.

These pitches are compatible with epoxy resins in practically all proportions. They are inexpensive and when added epoxy resins in an amount not representing more than 50% by weight of the polymerizable mixture, it is possible to retain the advantageous characteristics of the epoxy resins such as infusibility, high mechanical properties and longevity . These mixtures of pitch and epoxy resin can also cure at room temperature like the polymerizable mixture based on epoxy resin. The viscosity of mixtures of epoxy resin and pitch is lower than that of the mixtures of epoxy resin and sand used in the prior art for the treatment of large solid radioactive waste, and it is thus possible to carry out the packaging of such waste under better conditions, in particular as regards the preparation and transfer of the coating mixture.

During the hardening of such mixtures, chemical bonds are established between the pitch and the epoxy reactants; thus, this participation of the pitch in the polymerization gives the matrix greater stability than in the case where mixtures of epoxy resin and sand are used, optionally also comprising solvents and / or plasticizers.

The addition of pitch to the polymerizable mixture of epoxy resin gives the resin a thermoplastic character which increases with the pitch content of the mixture. Thus, the hardness of the mixture decreases when the pitch content increases. Likewise, the hardness of the mixture decreases with increasing temperature, and this effect increases with the pitch content of the mixture. Also, to maintain sufficient hardness characteristics in the solid blocks obtained, ie a Shore hardness of at least 50D, it is preferable that the amount of pitch added does not represent more than 40% by weight of the polymerizable mixture. Indeed, due to the chemical interactions between the pitch and the epoxy resin, a proportion of pitch ranging for example up to 30% by weight of the mixture has no influence on the hardness. On the other hand, above a weight proportion of 30%, the hardness decreases rapidly because the excess pitch plays the role of inert plasticizer.

In some cases, the pitch can also play the role of solvent, in particular with respect to certain liquid wastes which are difficult to incorporate into epoxy resins.

Generally, to implement the method of the invention, a first liquid component composed of pitch and hardener is used, and a second liquid component based on epoxy resin, the two liquid components are mixed with the liquid waste so as to obtain a homogeneous mixture, then let the mixture harden to obtain a solid block. In the case of solid waste, the mixture is poured into the container and its low viscosity allows it to penetrate into the interstices of solid waste.

These operations can be carried out at room temperature as in the case of polymerizable mixtures based on epoxy resin and hardener of the prior art. Indeed, the reaction is exothermic and the change in temperature in the reaction medium is similar to that obtained when using mixtures comprising only an epoxy resin and a hardener. To obtain a 200 l block, a maximum temperature of approximately 100 ° C. is obtained in 7 hours, when the mixture comprises 40% by weight of pitch. However, the presence of pitch considerably slows the final crosslinking of the epoxy resins and a period of three weeks to a month may be necessary to obtain the desired hardness.

However, this phenomenon can be activated by curing the mixture at an initial temperature above 20 ° C. However for a given volume the maximum temperature must not exceed the boiling temperatures of the constituents.

To implement the method of the invention, it is also possible to directly mix the pitch, the epoxy resin and the hardener with the waste to be treated at the time of use, then allow the mixture to harden to obtain a solid block. In the latter case, the hardening can be carried out at a temperature of 20 to 60 ° C.

It is preferable not to mix the pitch and the epoxy resin in advance because these can react and cause, by slow polymerization, an increase in viscosity during storage of the mixture. On the other hand, the pitch can be added in advance to the hardener in order to use, at the time of the coating operation of the waste, a mixture of two liquid constituents, which facilitates the actual coating operation.

• - un premier constituant liquide comportant au moins une résine époxyde, et
• - un second constituant liquide comportant un mélange de brai et d'au moins un durcisseur de la résine époxyde,

The invention therefore also relates to a polymerizable mixture with two liquid constituents, usable for the conditioning of radioactive or toxic waste, which comprises:

• a first liquid constituent comprising at least one epoxy resin, and
• a second liquid constituent comprising a mixture of pitch and at least one hardener of the epoxy resin,

the proportion of pitch in the second liquid constituent being from 53 to 73% by weight.

Preferably, it is fixed at 64% by weight, which corresponds to a polymerizable mixture at 40% by weight of pitch.

The use of such a mixture with two liquid constituents is advantageous in particular for the treatment of radioactive waste constituted by objects of large dimensions, because it is easier to implement than the mixture with three constituents based on resin, sand and hardener used in the prior art, which had to be prepared in a continuous mixer at the time of the coating operation.

With the mixture of two liquid components of the invention, a static mixer can be used, that is to say a simpler and less expensive device.

Usually. the pitch is introduced into the polymerizable mixture or into the second liquid constituent in the form of a solution in an appropriate solvent. In fact, pitch is a solid compound and to introduce it in the form of a liquid constituent, a solvent which is preferably not very volatile is added to it, such as chriseme oil, anthracene oil and the viscosity of the the solution by adjusting the amount of solvent added.

The epoxy resins used in the polymerisable mixture of the invention can, for example, be diglycidyl ethers of bisphenol A and their viscosity can be adjusted by adding a reactive diluent with low vapor pressure such as neopentyldiglycidyl ether.

The hardeners used with resins of this type can consist of compounds comprising at least one NH ₂ group, for example by cycloaliphatic or aromatic amines, aromatic or cycloaliphatic polyamines and derivatives of propylene amine. Polyaminoamides can also be used.

Preferably, compounds are chosen comprising a mixture of cycloaliphatic and aromatic amines, which allows polymerization of the resin whatever the pH.

The hardener can consist of a compound of this type in the pure state or dissolved in a suitable diluent such as benzyl alcohol. Generally, it is preferred to use hardeners constituted by "adducts" which are the product of the reaction of a small amount of the epoxy resin with the compound comprising at least one NH group, to which a cycloahphatic polyamine, a non-diluent, is optionally added. reagent and / or a curing accelerator.

The non-reactive diluent can be benzyl alcohol and the hardening accelerator can be the product of the reaction of acrylic acid, benzoic acid, salicylic acid or a phenol such as resorcinol with diaminodiphenylmethane.

Preferably, the hardener is an adduct of diaminodiphenylmethane and epoxy resin, optionally also comprising a cycloaliphatic polyamine.

The quantity of hardener present in the polymerizable mixture to obtain the polymerization and the crosslinking of the epoxy resin, depends on the epoxy resin used, in particular on its epoxy equivalent, that is to say on the mass of resin containing a function epoxy. Generally, to obtain the hardening and crosslinking of the epoxy resin, an amount of hardener is used such that there is at least one NH amine function, per epoxy resin equivalent. Usually, the amount of hardener is such that the weight ratio hardener / epoxy resin is greater than 0.5, for example equal to 0.6. The hardener-epoxy mixture described above must have a low exotherm to allow mass polymerization such that the maximum temperature remains in all cases below the boiling point of the constituents, for example 90 ° C. for a barrel of 200 liters.

The waste likely to be conditioned by the process of the invention can be in various forms. Thus, they can be constituted by solid waste such as powders from concentrates for evaporation of liquid effluents, pulverulent products, ash from the incineration of combustible waste and large objects such as filter cartridges, tools or metal chips placed in a basket. It is also possible, by the process of the invention, to treat organic liquid waste such as aliphatic or aromatic hydrocarbons, chlorinated solvents, extraction solvents such as tributyl phosphate and trilaurylamine, drain oils and scintillation liquids. used for beta counting.

On the other hand, given the hydrophobic nature of the pitch, it is difficult to treat by the method of the invention waste having a high water content and aqueous liquid waste. However, filter cartridges with a water content of 100% can be treated by the method of the invention because this corresponds substantially to the water saturation of the filters.

The amount of waste incorporated into the polymerizable mixture of the invention is of the same order as that which can be incorporated into the polymerizable mixtures of the prior art. In the case of most of the waste, the amount incorporated can represent from 40 to 60% of the whole formed by the waste and the polymerizable mixture. On the other hand, in the case of certain liquid wastes, it is necessary not to exceed certain contents, because otherwise there may be a settling of the liquids during the mixing operation and / or a bleeding phenomenon during the operation of polymerization. Furthermore, the quantities that can be incorporated also depend on the pitch content of the mixture and on the nature of the epoxy resin, the hardener and the pitch used in the polymerizable mixture.

According to an alternative embodiment of the method of the invention, a protective barrier made from a polymerizable mixture comprising a solid block consisting of the waste incorporated in the hardened mixture of epoxy resin, pitch and hardener is formed. at least one epoxy resin, pitch, and at least one hardener of the epoxy resin.

This makes it possible to constitute a barrier with respect to the diffusion of active or toxic elements, in particular when the solid waste is close to the walls of the hardened block. In addition, this barrier is very effective vis-à-vis the diffusion of tritium and tritiated water.

In this variant, it is possible first of all to form a hardened block by incorporating the waste into the polymerizable mixture, then to include this hardened block in a hollow cylindrical barrel produced from a polymerizable mixture comprising an epoxy resin, pitch and a hardener.

In this case, the waste and the polymerizable mixture comprising at least one epoxy resin, pitch and at least one hardener of the epoxy resin are introduced into a cylindrical drum obtained by curing a polymerizable mixture comprising at least one epoxy resin, pitch and at least one hardener of the epoxy resin, and said polymerizable mixture is allowed to harden to obtain a solid block inside said barrel.

Such a barrel can be prepared by conventional methods, for example by casting in a mold inside which an internal core is disposed or by centrifugation.

This protective barrier can also be formed during the packaging of radioactive or toxic waste by placing the solid waste in a basket such as a metal basket located in a barrel so as to provide a sufficient thickness between the basket and the barrel. In this case, the waste is first introduced into a basket, the basket containing the waste is placed in a barrel so as to provide a space between the internal wall of the barrel and the external wall of the basket, the barrel is filled and said basket of the polymerizable mixture comprising at least one epoxy resin, pitch and at least one hardener of the epoxy resin, and this mixture is allowed to harden in order to obtain in the barrel a solid block comprising an external layer formed solely of polymerized mixture based on epoxy, pitch and hardener.

When the polymerizable fluid mixture is introduced into the basket, it passes through the perforations in the basket to fill the space between the barrel and the basket and then harden the outer layer which constitutes the protective barrier. .

Other characteristics and advantages of the invention will appear better on reading the following examples, of course given without implied limitation to illustrate the invention, with reference to the appended drawing which is a diagram representing the Shore D hardness of solid blocks obtained according to the invention according to their waste content.

• - une résine époxyde constituée par un diglycidyl éther du bis phénol A ayant un équivalent époxyde d'environ 190 dilué par du néopentyldiglycidyléther et commercialisé par CDF Chimie sous la référence MN 201 T,
• - un durcisseur constitué par le produit vendu sous la référence D6M5 par CDF Chimie, qui est composé d'une polyamine cycloaliphatique ayant un équivalent amine d'environ 63 et d'un adduct de diaminodiphénylméthane et de la résine époxyde ayant un équivalent amine d'environ ₁30, et
• - une solution de brai commercialisée sous la référence 730/30 par DESAILLY.

In all the examples, a polymerizable mixture is used comprising:

• an epoxy resin constituted by a diglycidyl ether of bisphenol A having an epoxide equivalent of approximately 190 diluted with neopentyldiglycidylether and sold by CDF Chimie under the reference MN 201 T,
• - a hardener consisting of the product sold under the reference D6M5 by CDF Chimie, which is composed of a cycloaliphatic polyamine having an amine equivalent of approximately 63 and of a diaminodiphenylmethane adduct and of epoxy resin having an amine equivalent of about ₁ 30, and
• - a pitch solution sold under the reference 730/30 by DESAILLY.

Example ₁

This example illustrates the coating of solid waste constituted by metal chips and tools arranged in a metal basket. 20% by volume of this waste is introduced into a 200 1 container. 80% by volume of a mixture (40% pitch, 20% hardener and 40% resin) are then added and fill the voids left between the waste. The block obtained has a shore hardness of 54D.

Example 2

This example illustrates the packaging of a drain oil constituted by an industrial lubricating oil.

• - 10% en poids d'huile de vidange,
• - 30% en poids de brai,
• - 22,5% en poids de durcisseur, et
• - 37,5% en poids de résine époxyde.

In this example, a mixture of pitch and hardener D6M5, the epoxy resin MN 20 ₁ T and the drain oil are introduced into a 200 l barrel, in the following proportions:

• - 10% by weight of drain oil,
• - 30% by weight of pitch,
• - 22.5% by weight of hardener, and
• - 37.5% by weight of epoxy resin.

The mixture is then allowed to harden at 20 ° C for 15 days and the Shore hardness of the block obtained is determined. This is around 67D.

Tests carried out by replacing part of the drain oil with pitch and keeping the same proportions of resin and hardener, have shown that the Shore hardness decreases with the oil content. These results are illustrated in the appended figure which represents the Shore hardness as a function of the percentage of oil in the oil-pitch assembly. Furthermore, it has been verified that if the oil content of the oil-pitch mixture is increased above 50%, decantation of the oil takes place, which does not make it possible to obtain a block. homogeneous.

Example 3

• - 4% en poids de TBP,
• - 36% en poids de brai,
• - 22,5% en poids de durcisseur,
• - 37,5% en poids de résine époxyde.

This example illustrates the packaging of waste consisting of tributylphosphate. In this example, the tributylphosphate (TBP), the pitch, the hardener and the epoxy resin are mixed in the following proportions:

• - 4% by weight of TBP,
• - 36% by weight of pitch,
• - 22.5% by weight of hardener,
• - 37.5% by weight of epoxy resin.

After the mixing operation, it is left to harden at 20 ° C. and the Shore hardness of the blocks obtained is measured after 15 days of hardening. This Shore hardness is around 52D.

Example 4

• - ₄,8% en poids de liquide de scintillation,
• - 35,2% en poids de brai,
• - 22,5% en poids de durcisseur, et
• - 37,5% en poids de résine époxyde.

This example illustrates the packaging of a scintillation liquid used for beta counting consisting of 99.5% by weight of solvent mainly xylene and 0.5% by weight of liquid scintillator. In this example, the scintillation liquid, the pitch, the hardener and the epoxy resin are mixed in the following weight proportions:

• - _4, 8% by weight of scintillation fluid,
• - 35.2% by weight of pitch,
• - 22.5% by weight of hardener, and
• - 37.5% by weight of epoxy resin.

The Shore hardness of the blocks obtained after 15 days of hardening at 20 ° C. is measured as before.

This hardness exceeds 50D.

Claims (17)

1. A method of packaging radioactive or toxic waste, characterized in that it consists in incorporating said waste into a polymerizable mixture comprising at least one epoxy resin, pitch, and at least one hardener of the epoxy resin, and allowing it to harden the mixture to obtain a solid block. 2. Method according to claim 1, characterized in that the mixture comprises: - 30 to 45% by weight of epoxy resin, - 30 to 50% by weight of pitch, - 20 to 25% by weight of hardener. 3. Method according to claim 1, characterized in that the mixture comprises up to 50% by weight of pitch. ₄ . Process according to either of Claims 1 and 2, characterized in that the mixture comprises up to 40% by weight of pitch. 5. Method according to any one of claims 1 to 4, characterized in that the pitch is a pitch of coal from the treatment of tars with a low content of insoluble products. 6. Method according to any one of claims 1 to 5, characterized in that one uses a first liquid constituent composed of pitch and hardener and a second liquid constituent based on epoxy resin, in that one mix the two liquid constituents with the waste so as to obtain a homogeneous mixture, and in that the mixture is then allowed to harden to obtain a solid block. 7. Method according to claim 6, characterized in that the hardening of the mixture is carried out at a temperature of 20 to 60 ° C. 8. Method according to any one of claims 1 to 7, characterized in that the waste is large objects. 9. Method according to any one of claims 1 to 7, characterized in that the waste is organic liquids. 10. Method according to claim 9, characterized in that the organic liquids are chosen from drain oils, organic solvents and scintillation liquids. 11. Method according to any one of claims 1 and 2, characterized in that a protective barrier is formed around the solid block produced from a polymerizable mixture comprising at least one epoxy resin, pitch and at least an epoxy resin hardener. 12. Method according to claim 1, characterized in that the waste and the polymerizable mixture comprising at least one epoxy resin, pitch and at least one hardener of the epoxy resin are introduced into a cylindrical barrel obtained by hardening of a polymerizable mixture comprising at least one epoxy resin, pitch and at least one hardener of the epoxy resin, and in that said polymerizable mixture is allowed to harden to obtain a solid block inside said barrel. 13. Method according to claim 1, characterized in that the waste is introduced into a basket, in that the basket containing the waste is placed in a barrel so as to provide a space between the internal wall of the barrel and the outer wall of the basket, and in that the barrel and said basket are filled with the polymerizable mixture comprising at least one epoxy resin, pitch and at least one hardener of the epoxy resin, and in that said hardening is allowed to harden mixture to obtain in the barrel a solid block comprising an external layer formed solely of polymerized mixture based on epoxy resin, pitch and hardener. 14. Polymenable mixture of two constituents for the conditioning of radioactive or toxic waste, characterized in that it comprises: a first liquid constituent comprising at least one epoxy resin, and - A second liquid component comprising a mixture of pitch and at least one hardener of the epoxy resin, the proportion of pitch in the second liquid component being from 53 to 73% by weight. 15. The mixture as claimed in claim 14, characterized in that the epoxy resin is a diglycidyl ether of bis-phenol A with the addition of a reactive diluent. 16. A mixture according to any one of claims 14 and 15, characterized in that the hardener is an adduct of diaminodiphenylmethane and epoxy resin. 17. Mixture according to any one of claims 14 and 15, characterized in that the hardener comprises a cycloaliphatic polyamine and a diaminodiphenylmethane adduct and epoxy resin.

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