KR870000465B1 - Process for encapsulating radioactive organic liquids in resin - Google Patents

Abstract

Radioactive organic waste is disposed by encapsulating in resin. Low concentration soln. of radioactive organic waste is contacted with an organic liguid-insoluble polymer to form gel particles. These gel particles are dispersed into liguid resin. This liguid resin containing dispersed gel particles is then hardened. The organic liguid-insoluble polymer is a copolymer of tertiary butyl styrene and styrene. The catalyst of the hardening reaction is a peroxide compound.

Description

How to encapsulate low labor radioactive liquid water-insoluble organic waste in curable liquid resin

The present invention relates to a method of encapsulating low labor radioactive liquid-insoluble organic waste in a curable liquid resin.

One of the problems with using radioactive materials is the disposal of waste. Conventionally, these wastes were encapsulated in solid form and buried at designated sites. Concrete and urea / formaldehyde resins were used here. Recently, it has been proposed that wastes in the form of solids, aqueous solutions or slurries can be dispersed in unsaturated polyester or vinylester resins to convert the waste into solids with dispersed droplets.

The prior art methods are useful for aqueous wastes generated during nuclear power plant operation. However, there are many drawbacks when this method is used for radioactive organic solvent wastes from nuclear power devices such as oil and waste generated in medical laboratories. Such wastes are generally water-insoluble, but may be soluble or slightly soluble or insoluble in the resin system, or may be solvents for the resin system or parts thereof.

Prior art methods can be used to disperse certain organic liquids that are water-insoluble but partially soluble in the resin system. However, organic materials, which are relatively low concentrations of organic waste, can cause layer separation. At this time, the organic material acts as a plasticizer and can move between the fourth even after the resin is cured. Since the purpose of radioactive waste is to store it for a long time, the movement of organic material may appear on the surface, which may interfere with the encapsulation.

Such wastes pose serious problems associated with significant ecological aspects of disposal.

The present invention comprises contacting less than 1 part by weight of granular cross-linked, organic liquid-swellable, organic liquid-insoluble polymer with low concentrations of radioactive liquid water-insoluble organic waste, thereby separating the polymer and waste separable, non-polymeric gelled particles. 0.1 to 3 parts by weight of the gel particles were uniformly dispersed in 1 part by weight of a curable liquid resin selected from an unsaturated polyester resin, a vinyl ester resin or a mixture thereof. A method of encapsulating a low concentration of radioactive liquid water-insoluble organic waste in solid form, characterized in that the liquid resin is cured into a solid form having gel particles dispersed in a liquid resin.

Radioactive wastes effective in the process of the present invention are water-insoluble organic liquids and mixtures of such liquids with water. Examples of the organic liquids mentioned above include hydrocarbons such as benzene, toluene, xylene, naphtha, cyclonucleic acid, octane, dodecane and halogenated derivatives of these compounds, such as 1,1,1-trichloroethane, tetrachloroethane Chlorinated compounds and chlorinated aromatics. In addition, oils such as gasoline and kerosene, lubricating oil and diesel oil as well as gasoline and kerosene are included in the organic liquid.

Sometimes, the waste material may be a mixture of water and water-insoluble organic liquid. The method of the present invention is equally useful for such mixtures.

Effective polymer particles contained in radioactive liquid organic waste are crosslinked organic liquid-swellable, organic liquid-insoluble aggregates. The term organic liquid-swellable, organic liquid-insoluble polymer means a polymer that is substantially insoluble but capable of swelling, i.e., absorbs one or more of the aforementioned water-insoluble organic liquids. That is, such polymers can be swollen by any solvent as long as the organic liquid is a solvent used for the homopolymer homologue.

As absorbents in the process of the invention it is preferred to use crosslinked polymers of alkylstyrene, preferably tertiary alkylstyrene. Alkyl styrenes that can be used to prepare such polymers are, for example, those having 4 to 20, preferably 4 to 12, carbon atoms. P-tert-butylstyrene. P-tert-amyl styrene, P-tert-butyl styrene. Tertiary alkyl styrene such as P-tert-dodecyl styrene. For example, n-alkylstyrenes such as n-butylstyrene, n-hexylstyrene, n-decylstyrene, for example, 2, such as secondary-butylstyrene, secondary-octylstyrene, secondary-dodecylstyrene Tertiary-alkyl styrene and for example isobutyl styrene. Isoal styrene, such as isooxstyrene and isodo de silstyrene.

In addition, crosslinked copolymers of alkylstyrenes as described above and alcohols having 1 to 18 carbon atoms with alkyl esters derived from acrylic acid or dethacrylic acid or mixtures thereof are effective in carrying out the present invention. In order to have buoyancy in water and the ability to penetrate or swell by a wide range of organic liquids, copolymers such as p-tert-butylstyrene and methyl methacrylate preferably contain at least 50 mol% alkylstyrene.

However, crosslinked polymers in which the linear homologs are organic liquid-soluble. For example, co-polymers of essentially cross-linked vinyl-added polymers and intrinsically anodic monomer compositions comprising the following compounds can be used in the process of the present invention: vinyl naphthalene, styrene and substituted styrenes (eg. α-methylstyrene, ring-substituted α-methylstyrene, alkylstyrene, halostyrene, acylstyrene and alkaryl styrene), methacrylic esters, acrylic ester fumarate esters and 1/2 esters, maleate esters and 1 Eggs such as 1/2 esters, itaconate esters and 1/2 esters, vinyl biphenyls, aliphatic carboxylic acid ester vinyl esters, alkyl vinyl esters, alkyl vinyl ketones, α-olefins, isoolefins, butadiene, isoprene and dimethylburadiene Kenyl aromatic compounds.

The polymer used as the absorbent in the process of the invention contains a small amount of crosslinker. It is important to contain 0.01 to 2% by weight. The most effective absorption of organic liquid contaminants, especially from dispersions, occurs when the crosslinker content is less than 1% because the polymer absorbs almost all of the organic liquid and readily swells. When the organic liquid contaminant fluid is filtered through a packed column or bed, up to 2% crosslinker is preferred because low volume organic liquid materials absorbed by the polymer may be acceptable for this type of operation.

Crosslinkers that can be used to prepare absorbent polymers suitable for use in the present invention include polyethylene unsaturated compounds such as divinylbenzene, diethylene glycol dimethacrylate, diisopropenylbenzene, diisopropenyldiphenyl, di Allyl maleate, diallyl phthalate, allyl acrylate, allyl methacrylate, allyl fumarate, allyl itaconate, allky resin type. Butadiene or isoprene polymer. Cyclooctadiene. Methylene norbornylene. Divinyl phthalate, vinyl isopropenylbenzene, divinyl biphenyl, and other two- or multi-functional compounds known to be used as crosslinking agents in polymerizable vinyl-additives. Typically, the polymer containing the crosslinker is swollen by the absorbed organic liquid. Too much crosslinking agent may result in undesirably long-term absorption or the polymer may not be able to absorb a sufficient amount of the organic liquid, so that the absorbent polymer, which reduces the effectiveness of the polymer as an absorbent, contains no crosslinking agent or contains too little If so, the absorbent polymer will dissolve in the organic liquid to form a non-separated non-granular polymer mass.

These polymer particles are sometimes mixed with lipophilic materials with large surface areas to act as inert wicks to help the organic liquid to be absorbed by the particles. Examples of such lipophilic materials include common materials such as crushed resinous foams and crushed truck tires. The presence of a wicking agent shortens the time for the particles to absorb the organic liquid and swell. If no such working agent is present, it takes an unacceptably long time for the particles to absorb the organic liquid.

In addition, various crosslinked polymers have different absorption capabilities with respect to the organic liquid, depending on the characteristics of the organic liquid. This absorption capacity can be easily measured by simple preliminary experiments.

Thus, in the practice of the present invention, the amount of swelling of the absorbent polymer particles and the amount of polymer used to absorb the organic liquid depends on the type and amount of liquid to be absorbed and the degree of crosslinking of the particular polymer and polymer used. Typically less than 1 part by weight, typically less than 0.1 part by weight, of the absorbent polymer per part by weight of the organic liquid is used to carry out the present invention. If the ratio of beads to organic liquid is too high, the beads may absorb a portion of the reactive diluents used to change the properties of the system, in particular the viscosity.

Various ways in which the polymer particles absorb the organic liquid will be apparent. In one of the methods, the particles are added to the organic liquid with relatively gentle stirring. Care should be taken to ensure that the polymer particles are not cut to less than 0.05 mm in diameter. In general, these small sized particles present more difficulty in the continuous treatment of the materials used in the operation in the present invention. In general, particles having a size of 0.1 to 1 mm in diameter are preferred.

Another aspect is a method of filling a column or phase with absorbent polymer particles and passing an organic liquid therebetween.

Similar techniques can be used if the waste is a mixture of water and radioactive organic liquid. The polymer particles can be mixed with a dispersion of organic liquid and water. The organic liquid can be left to separate and floats on the water surface in most cases. Beads may precipitate in organic liquids.

In either embodiment, the process of the invention can be carried out at a temperature at which the radioactive waste becomes liquid. Typically, absorption is carried out at ambient temperature and atmospheric pressure to enable the use of less complex devices and to minimize the risk to the human body from the release of radiation.

Vinyl ester resins are described in US Pat. No. 3,367,992, wherein dicarboxylic acid 1/2 esters of hydroxy alkyl acrylates or methacrylates are reacted with polyepoxide resins.

Bowen, US Pat. Nos. 3,066,112 and 3,179,623, describe a process for preparing vinyl ester resins from monocarboxylic acids such as acrylic acid and methacrylic acid. Bowen also published another method for reacting glycidyl methacrylate or acrylate with sodium salts of dihydric phenols such as bisphenol A. Vinyl ester resins based on epoxy noblock resins are described in US Pat. No. 3,301,743 to Peket et al. In addition, US Pat. No. 3,256,226 to Peket et al describes vinyl ester resins in which a dicarboxylic acid is reacted with a polyepoxide resin, acrylic acid or the like to increase the molecular weight of the polyepoxide. Instead of dicarboxylic acids, other difunctional compounds containing groups reactive with epoxide groups such as amines or mercaptans can be used. All the above-mentioned resins having a specific bond as follows and having a polymerizable vinylidene group at the end are classified as vinyl ester resins.

That is, all the known poly epoxides can be used in producing the vinyl ester resin of the present invention. Useful polyepoxides are glycidyl polyethers of polyhydric alcohols and polyhydric phenols, epoxy noblocks, epoxide unsaturated diunsaturated esters and epoxidized unsaturated polyesters, and these compounds contain one or more oxirane groups per molecule. .

Preferred polyepoxides are glycidyl polyethers of polyhydric alcohols or polyhydric phenols having a molecular weight of 150 to 2000 per epoxide group. These polyepoxides are typically prepared by reacting at least about 2 moles of epihalo hydrin or glycerol hydrin with an amount of caustic alkali sufficient to be combined with one mole of polyalcohol or polyhydric phenol and halohydrin. The product is characterized by having one or more epoxide groups per molecule, for example equivalent one or more 1,2-epoxy groups.

Unsaturated monocarboxylic acids include, for example, acrylic acid, methacrylic acid, halogenated acrylic acid or methacrylic acid, cinnamic acid and mixtures thereof. In addition, "unsaturated carboxylic acids" include hydroxyalkyl acrylates or methacrylate 1/2 esters of the dicarboxylic acids described in U.S. Patent No. 3,367,992, wherein the hydroxyalkyl groups are two to six carbon atoms. It is desirable to have.

It is preferable that a thermosetting resin phase consists of 40 to 70 weight% of vinyl ester or polyester resins, and 60 to 30 weight% of a copolymerizable monomer. Although it does not require complete water insolubility and a small amount of monomer dissolved in emulsified water does not harm, suitable monomers should be essentially water insoluble so that they can be present as monomers on the resin in the emulsion.

Suitable monomers include, for example, vinylaromatic compounds such as styrene, vinyltoluene and divinylbenzene. Other useful monomers include, for example, ethers of saturated alcohols such as methyl, ethyl, isopropyl and octyl with acrylic acid or methacrylic acid, hydroxy ethyl or hydroxy propyl acrylate or methacrylate, vinyl acetate, diallyl male Included are mixtures of the compounds described above with all other monomers that are copolymerizable with water, dimetall fumarate, vinylester resins and are essentially water-insoluble.

In another embodiment of the present invention, a modified vinyl ester resin in which 0.1 to 0.6 moles of dicarboxylic anhydride is reacted with a vinyl ester resin per equivalent of hydroxyl is used. The storage stability of the resin-in-molar emulsion prepared from the modified vinyl ester resin is slightly lower than that of the unmodified vinyl ester resin, but the stability is greatly improved compared to the prior art. Both saturated and unsaturated acid anhydrides are useful for the above modifications.

Suitable dicarboxylic anhydrides containing ethylenically unsaturateds are, for example, maleic anhydride, citraconic anhydride itaconic anhydride and mixtures thereof. Saturated dicarboxylic acid anhydrides are, for example, anhydrides of phthalic anhydride and aliphatic unsaturated dicarboxylic acids. Modified vinylester resins are costly to the present invention in the same manner as described above for unmodified vinylester resins.

In addition, various unsaturated polyesters which are commercially available or can be prepared by methods known in the art can also be used in the process of the invention. Such polyesters are produced by condensation of a polybasic carbolic acid with a compound having several hydroxyl groups. Generally, in preparing suitable polyesters, ethylenically unsaturated dicarboxylic acids such as, for example, maleic acid, fumaric acid or itaconic acid are esterified with alkylene glycols or polyalkylene glycols having a molecular weight of 2000 or less. Sometimes, dicarboxylic acids that do not contain ethylenically unsaturated compounds such as, for example, phthalic acid, isophthalic acid, adipic acid, and succinic acid can be used within a molar ratio of about 0.25 to 15 moles per mole of unsaturated dicarboxylic acid. Suitable acid anhydrides may be used if so provided, but it will be appreciated that commercially available ones are preferred.

The glycol or polyalcohol component of the polyester is usually used in stoichiometric or slight excess relative to the total acid. Excess polyhydric alcohols rarely exceed 20 to 25%, typically 10 to 15%.

Generally, such unsaturated polyesters can be prepared by heating a mixture of polyhydric alcohols and dicarboxylic acids or anhydrides in suitable molar ratios at elevated temperatures, typically from 150 to 225 ° C. for 5 hours.

It may be advantageous to add a polymerization inhibitor such as tert-butyl catechol. It is also possible to prepare unsaturated polyesters directly from suitable oxides other than glycols, for example using propylene oxide instead of propylene glycone. In general, the condensation (polymerization) reaction continues until the acid content drops to 2-12% (-COOH), preferably 4-8%.

In another embodiment of the present invention, a vinyl ester / unsaturated polyester resin composition is used. The composition can be made by physically mixing the two resins in the desired weight proportions or by making vinyl ester resins in the presence of unsaturated polyesters.

The concept of the present invention applies to organic wastes, but it is preferred to contain a significant amount of water. The water in the dispersion helps to control the heat generated during curing. This is particularly important when it is difficult to control heat generation by external means using a large amount of curable resin. The use of water also results in a uniform dispersion and helps the cured system to pass various requirements and regulations, such as the U.S. Department of Transportation fire test. In addition, the use of water gives viscosity, which prevents waste from separating before gelation.

Water that may be present in the waste is added to the waste before dispersion, or added to the resin to form an emulsion and then to the waste in swelling beads. When water is added to the waste, water can be mixed with the waste prior to absorption, or absorbed into the waste and then water can be added to produce aqueous slurry.

The ratio of the single component of the slurry particles alone to the dendritic particles or the slurry particles mixed with water may vary within the range of 0.1 to 3 parts by weight of swelling beads + water per 1 part by weight of resin. Preferably, the resin-in-waste dispersion is prepared to contain 1 to 1.5 parts by weight of waste + water per 1 part by weight of resin.

In carrying out the process of the present invention, the waste dispersion in vinyl ester or unsaturated polyester resin can be produced by various methods. Generally, a catalyst providing free radicals is mixed with the resinous phase and then the radioactive waste absorbed in the beads is dispersed in the resin under conditions that produce a uniform dispersion of the waste in the resin. Shear conditions can vary greatly, but in general, when free water is present with the waste, sufficient shear force must be applied to produce a small droplet size uniform emulsion.

The dispersion should have sufficient storage stability to sustain the initial gelation of the resin. Dispersions made from vinyl ester resins, particularly those within the aforementioned monomer ratio ranges, generally exhibit adequate stability without the addition of emulsifiers. Dispersions of swelling particles in water that can be dispersed in unsaturated polyesters often require the addition of emulsifiers. These emulsifiers are known in the art, and an appropriate method of obtaining a closed cell system can be made by simple experiments. In most cases, sodium carboxylate salts emulsify the waste even without the addition of emulsifiers, especially for polyesters with carboxy termini.

Catalysts which can be used for curing or polymerization include peroxides and hydroperoxide catalysts such as benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, methyl ethyl ketone peroxide, tertiary- Preference is given to butyl perbenzoate and potassium and potassium persulfate. The amount of catalyst added is not constant but will be at least 0.1% by weight of the resinous phase.

Curing of the dispersion is usually carried out at a concentration of 0.01 to 5% by weight of a curing accelerator such as lead naphthenate or cobalt naphthenate, N, N-dimethylaniline, N, N-dimethyl-p-toluidine and vanadium neodecano It is preferred to carry out by adding the ate at room temperature. In addition, the catalyst may be added to the resin before dispersing the waste and the accelerator may be added after the dispersion has been produced. The activated dispersion may be cured at least in a gel state within a short time, for example within 3 to 30 minutes, or in the solid phase in 30 minutes to 1 or 2 hours, depending on temperature, catalyst content and promoter content. In addition, curing of the dispersion may be carried out by heating to the boiling point of the organic liquid or below 100 ℃. Conventional practice of post-curing a thermoset product at elevated temperatures for various times can be used in the present invention.

If the temperature is increased above the above-mentioned range, the catalyst, catalyst concentration, accelerator and accelerator concentration should be selected so that the exothermic temperature does not exceed the above-mentioned range until the resin has cured to such an extent that it can withstand the increased vapor pressure strength. do. If the temperature exceeds 100 ° C. before curing, the water in the liquid waste aeration may boil to release the waste material or the organic liquid may be released from the swollen particles.

Solidification can be carried out in a suitable container such as a 55 gallon (208 liter) drop. Larger or smaller containers may be used depending on the amount of waste to be treated, the equipment used and restrictions on handling and transportation. As the size of the container increases, it becomes more difficult to control the exotherm within the range as mentioned above. In this case, it may be desirable for the amount of water and catalyst concentration to control the exotherm by controlling the promoter.

The method of the present invention is specifically described in the following examples, all parts and percentages by weight unless otherwise indicated.

Example 1

Radioactive wastes containing 0.04 microcurie per ml of carbon 14 and tritium in toluene mixed with water are solidified in the following manner. Toluene is 10% of the liquid and water is 90%.

To 75 ml of well shaken sample was added 0.38 g of a composition containing slightly crosslinked tert-butyl-styrene absorbent polymer in the form of small beads and crushed polyethylene bubbles. This composition is described in US Pat. No. 4,172,031. Phase separation occurs as beads float to the surface within minutes. The crystal phase is inclined and emulsified in 50 g of a vinyl ester resin containing 1.5 g of 40% by weight of the Enzoyl peroxside catalyst composition emulsified in diisobutyl phthalate. The vinylether resin used is a polymethacrylic acid ester of polyepoxide consisting of 0.25 equivalents of diglycidyl ether of bisphenol A (EEW = 188) and 0.75 equivalents of epoxy novolac (EEW = 180). The resin contains 36% of styrene as a copolymerizable monomer.

The swollen beads are added to the resin-in-water with 0.13 ml of dimethyl toluidine.

The composition gels within 5.8 minutes and cures overnight.

The sample to be tested is prepared by curing the dispersion in a nylon mold of 2 inches (5 cm) in length and 0.5 inches (12.77 mm) in diameter. Radioactive losses within 24 hours by water extraction were 142.2% carbon and 1.5% tritium.

Example 2

The same radioactive waste used in Example 1 was obtained from commercially available polyester resin (manufactured by PPG Indastries, Inc., under the trade name selectron SR-3703), 2.5 parts of the catalyst of Example 1 and 0.2 phr of dimethyl toludine per 100 parts of resin (phr). To solidify according to the method of Example 1.

Gel time is 6.8 and the sample cures in 30 minutes.

Claims (7)

1 part by weight of a low concentration of radioactive liquid water-insoluble organic waste is contacted with less than 1 part by weight of a granular crosslinked organic liquid-swellable, organic liquid-insoluble polymer to obtain separable, non-granulated gelling particles of the polymer and waste, 0.1 to 3 parts by weight of the gel particles are uniformly dispersed in 1 part by weight of a curable liquid resin selected from unsaturated polyester resins, vinyl ester resins and mixtures thereof, and the liquid resin is cured to a solid having gel particles dispersed in the liquid resin. Characterized in that a low concentration of radioactive liquid water-insoluble organic waste is encapsulated in a solid form suitable for investment. The method of claim 1 wherein the insoluble aggregate is a crosslinked copolymer of tertiary butyl styrene and styrene. The method of claim 2 wherein the copolymer is crosslinked with divinyl benzene. The method of claim 1 wherein the liquid organic waste is a hydrocarbon. The process of claim 1 wherein the liquid organic waste is an aqueous acid solution of a radioactive water-insoluble liquid material. The method of claim 5, wherein the organic liquid-insoluble polymer is added to the aqueous liquid solution, and the dispersion of the gel particles dispersed with water is encapsulated in the curable liquid resin. The gelled particles according to claim 5, wherein the organic liquid-insoluble aggregate is added to the aqueous dispersion, the phases are separated, and water is added to the liquid-curable resin to stir to form a resin-in-water emulsion to form gelled particles in this emulsion. How to mix in.