JPH0342639B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION One of the many problems that have arisen with the use of radioactive materials is the disposal of radioactive waste. Traditional methods of such processing have involved encapsulation of radioactive waste in a solid body and embedding the solid body in a designated location. Concrete and urea-formaldehyde resins have been so used. It has recently been proposed that radioactive waste in solid, aqueous or slurry form can be dispersed in an unsaturated polyester or vinyl ester and converted into a solid with a dispersion liquid dispersed therein.

Each of the prior art techniques has been useful for aqueous waste generated from nuclear power generation.

However, these techniques have drawbacks when attempts are made to use them with radioactive organic solvents such as oil from nuclear power generation and wastes generated from chemical and pharmaceutical factories. Such wastes are normally water-insoluble, but may be soluble, partially soluble, or insoluble in the resin system, or in the solvent for the resin system or as part of it. Also good.

With these prior art techniques it is possible to disperse certain organic liquids which are water-insoluble but partially soluble in the resin system. However, at certain low concentrations of such organic waste, the organic material separates into phases. In that respect, the organic material acts like a plasticizer and migrates through the resin system even after the resin has cured. Since long-term storage is necessary for radioactive waste, such migration defeats the purpose of encapsulation by having the waste on its surface.

Disposal of such waste poses primary ecological problems.

The present invention provides a method for encapsulating water-insoluble organic waste in a solid form suitable for implantation, in which a radioactive liquid with a low concentration is mixed with 1 part by weight of the waste and a granular, cross-linked, swellable organic liquid. contact with less than 1 part by weight of an insoluble polymer to form dispersed, non-agglomerated, gelled particles of said polymer and said waste; selected from the group consisting of unsaturated polyester resins, vinyl ester resins or mixtures thereof; 0.1 to 3 parts by weight of the gelled particles are substantially uniformly dispersed in 1 part by weight of an unliquid curable resin; and the liquid resin is cured to form a solid with the gelled particles encapsulated therein. A method characterized by converting the

These radioactive wastes for which the present invention is useful include water-insoluble organic liquids and mixtures of such liquids with water. Hydrocarbons such as benzene, toluene, xylene, naphtha, cyclohexane, octane, dodecane, and 1,1,1-
Within the scope of such organic liquids are halogenated derivatives of hydrocarbons, including chlorinated compounds such as trichloroethane, tetrachloroethane and chlorinated aromatics. Also within the scope are oils such as, for example, light oil, heavy oil, lubricating oil, diesel oil, gasoline, and kerosene.

Often, the waste material may be a mixture of water and the water-insoluble organic liquid. The method of the invention has equal utility with such mixtures.

Polymer particles useful for containing the radioactive liquid organic waste are crosslinked, organic liquid swellable, organic liquid insoluble polymers. An organic liquid-insoluble polymer that is swellable in an organic liquid is one that is substantially insoluble in the organic liquid, but is swellable, i.e. absorbs one or more of the water-insoluble organic liquids described above. means a polymer that can That is, these polymers are swellable by organic liquids that are solvents for linear analogs of the polymers.

Preferably crosslinked polymers of alkylstyrenes, and advantageously crosslinked polymers of tertiary alkylstyrenes, are utilized as swelling or absorbing agents in the process of the invention. These alkylstyrenes that can be used to prepare these polymers include, for example, p-tertiary-butylstyrene, p-
Tertiary alkylstyrenes, including tertiary-amylstyrene, p-tertiary-hexylstyrene, p-dodecylstyrene; e.g. n-butylstyrene;
n-alkylstyrenes, including n-hexylstyrene, n-decylstyrene; secondary-alkylstyrenes, including e.g. Includes alkyl groups containing 4-2U carbon atoms, preferably 4-12 carbon atoms, such as isoalkylstyrenes, including octylstyrene and isododecylstyrene.

Such crosslinked copolymers of alkyl styrenes and C _1-18 alcohol-alkyl esters of acrylic or methacrylic acid or mixtures thereof, as described above, are useful in the present invention.

The copolymer, such as the copolymer of p-tertiary-butylstyrene and methyl methacrylate, should contain at least 50 mole percent of its alkyl styrene to ensure, in addition to its buoyancy with respect to water, the possibility of being swelled by a wide range of organic liquids. is preferred.

However, crosslinked polymers, such as crosslinked vinyl addition type polymers and copolymers of essentially lipophilic monomer compositions, the linear analogs of which are soluble in organic liquids, can be used in the present invention. The copolymers include vinylnaphthalene, styrene and alkenyl aromatic compounds such as substituted styrenes such as alpha-methylstyrene, ring-substituted alphamethylstyrene, alkylstyrenes, halostyrene arylstyrenes, and alkarylstyrenes, and methacrylic esters, acrylics. acid esters, fumarate esters and half esters, maleate esters and half esters, itaconate esters and half esters,
Copolymers of monomer compositions such as vinyl biphenyls, vinyl esters, aliphatic carboxylic acid esters, alkyl vinyl esters, alkyl vinyl ketones, alphaolefins, isoolefins, butadiene, isoprene and dimethylbutadiene.

The polymer used as absorbent or swelling agent in the present invention contains only a small amount of crosslinking agent, preferably
It is important to include 0.01 to 2% by weight of crosslinking agent. Particularly effective imbibition of organic liquid contaminants from dispersions is achieved when the concentration of the crosslinking agent is 1.
% by weight or less because this causes the polymer to easily swell and absorb substantial amounts of organic liquid. When fluids contaminated with organic liquids are percolated through packed columns or beds, up to 2% crosslinker is acceptable. The reason is that a low volume of organic liquid material absorbed by the polymer is acceptable in this type of operation.

Crosslinking agents that can be used to make absorbent polymers suitable for use in the present invention include divinylbenzene, diethylene glycol dimethacrylate, diisopropenylbenzene, diisopropenyldiphenyl, diallyl maleate, diallyl phthalate, allyl acrylates, Allyl methacrylates, allyl fumarates, allyl itaconates, alkyd resin types, butadiene or isoprene polymers, cyclooctadiene, methylenenorbonylenes, divinyl phthalates,
Polyethylenically unsaturated compounds such as vinylisopropenylbenzene, divinylbiphenyl, as well as other di- or poly-functional compounds known to be used as crosslinking agents in polymer vinyl addition compositions. include. The polymer, usually including the crosslinker, swells with the absorbed organic liquid. If there is too much crosslinking agent, the absorption will occur for an unreasonably long period of time, or the polymer will not be able to absorb a sufficient amount of organic liquid, thereby reducing the effectiveness of the polymer as an absorbent. If the absorbent polymer contains little or no crosslinking agent, the polymer will dissolve in the organic liquid, resulting in the formation of non-dispersed, non-particulate masses of the polymer, for example.

Such polymer particles are sometimes mixed with a large surface area lipophilic substance to act as an inert core and aid in the absorption of organic liquids by the particles.
Such lipophilic substances include crushed resin foam,
This is further exemplified by crushed truck tires. The presence of the heartwood shortens the time during which the particles are swollen by absorption of the organic liquid. When no such heartwood is present, absorption takes a long time.

Different types of crosslinked polymers have different absorption capacities for organic liquids depending on the properties of the organic liquid. Its performance can be easily determined by simple preliminary experiments.

The amount of swelling of the absorbent polymer and the amount of polymer to be used to absorb the organic liquid in the present invention depends on the type of liquid to be absorbed, the particulate polymer used and the degree of crosslinking of the polymer. Less than 1 part by weight of absorbing polymer per part by weight of organic liquid, and usually no more than 0.1 part by weight, is used in the present invention. If the ratio of beads to organic liquid is too high, the beads will absorb a portion of the reactive diluent used and thereby change the properties of the system, such as viscosity.

Various ways of effecting the absorption of organic liquid by the polymer particles are obvious. In one method, the particles are introduced into the organic liquid by relatively gentle agitation. The agitation should not vibrate enough to cause sufficient shear of the polymer particles to sizes less than 0.05 mm in diameter. Such small sized particles are difficult to handle in subsequent handling operations of the present invention. generally diameter
Particles with a size of 0.1 to 1 mm are preferred.

In other embodiments, the column or bed is packed with absorbing polymer particles and an organic liquid passing therethrough.

A similar technique can be used when the waste is a mixture of water and radioactive organic liquid. The polymer particles can be mixed with the organic liquid and water dispersion. The organic liquid separates and often rises to the surface of the water. The beads can then be precipitated in the organic liquid.

The embodiment operates at a temperature where the radioactive waste is a liquid. Usually, the absorption is carried out at room temperature and normal pressure, using complex equipment and minimizing the risk of radioactive leakage.

Vinyl ester resins are described in US Pat. No. 3,367,992, in which dicarboxylic acid half esters of hydroxyalkyl acrylates or methacrylates are reacted with polyepoxide resins. U.S. Patent No. 3,066,112 and
No. 3,179,623 describes the production of vinyl ester resins from monocarboxylic acids such as acrylic acid or methacrylic acid. That US patent describes another method of preparation in which glycidyl methacrylate or acrylate is reacted with a sodium salt of a divalent phenol, such as bisphenol A. Vinyl ester resins based on epoxy novolak resins are described in US patents. It describes a vinyl ester resin in which the molecular weight of the polyepoxide is increased by reacting dicarboxylic acid with the polyepoxide resin and with acrylic acid or the like. Other difunctional compounds containing groups that react with epoxide groups, such as amines or mercaptans, can be used in place of dicarboxylic acids. All of the above-mentioned resins containing the following bond ■■■ Tortoise Shell [0003] ■■■ and a terminal, polymerizable vinylidene group are classified as vinyl ester resins.

Any of the known polyepoxides can be used in making the vinyl ester resins of this invention. Useful polyepoxides are glycidyl polyethers of polyhydric alcohols and polyhydric phenols, epoxy novolacs, epoxidized fatty acids, or drying oil acids, epoxidized diolefins, epoxidized diunsaturated acid esters, and other epoxidized unsaturated polyesters; The condition is then that they contain more than one oxirane group per molecule.

Preferred polyepoxides are glycidyl polyethers of polyhydric alcohols or polyhydric phenols having a weight of 150 to 2000 per epoxy group. These polyepoxides are usually made by reacting at least about 2 moles of epihalohydrin or glycerol dihalohydrin with 1 mole of polyhydric phenol and a sufficient amount of a carrier alkali to combine with the halogen of the halohydrin. . The products are characterized by the presence of more than one epoxy group per molecule, such as 1,2-epoxy with an equivalent weight of more than one.

Unsaturated monocarboxylic acids include, for example, acrylic acid,
Including methacrylic acid, halogenated acrylic acid, halogenated methacrylic acid, cinnamic acid and mixtures thereof. "Unsaturated carboxylic acids" are hydroxyalkyl acrylate or methacrylate half esters of dicarboxylic acids whose hydroxyalkyl groups preferably have from 2 to 6 carbon atoms, as described in US Pat. No. 3,367,992.

Preferably the thermosetting resin phase consists of 40-70% by weight of the vinyl ester or polyester resin and 60-30% by weight of the copolymerizable monomer. Suitable monomers must be substantially water-insoluble in order to retain the monomer in the resin phase in the emulsion. However, complete water insolubility is not required and small amounts of monomer dissolved in the emulsifying water are not harmful.

Suitable monomers include, for example, vinyl aromatics such as styrene, vinyltoluene and divinylbenzene. Other useful monomers are
Esters of acrylic or methacrylic acid with saturated alcohols such as methyl, ethyl, isopropyl and octyl alcohol; hydroxyethyl or hydroxypropyl acrylate or methacrylate, vinyl acetate, diallyl maleate, dimethallyl fumarate, mixtures thereof and It includes all other monomers that are copolymerizable with the vinyl ester resin and are essentially water-insoluble.

Another embodiment of this invention utilizes a modified vinyl ester resin in which 0.1 to 0.6 moles of dicarboxylic anhydride per equivalent of hydroxyl are reacted with the vinyl ester resin. Although the storage stability of water-in-resin emulsions made from the modified vinyl ester resins is somewhat less than that obtained with unmodified vinyl ester resins, the stability is improved over that of the prior art. . Saturated and unsaturated acid anhydrides are useful for the modification.

Suitable dicarboxylic acid anhydrides containing ethylenic unsaturation include, for example, maleic anhydride, citraconic anhydride, itaconic anhydride, and mixtures thereof. Saturated dicarboxylic acid anhydrides include, for example, phthalic anhydride and aliphatic unsaturated dicarboxylic acid anhydrides. The modified vinyl ester resin is utilized in this invention in the same manner as described for the unmodified vinyl ester resin.

Various unsaturated polyesters that are readily available or can be prepared by conventional methods can also be utilized in the process of this invention. Such polyesters result from the condensation of polybasic carboxylic acids with compounds containing several hydroxyl groups. Generally, in the preparation of suitable polyesters, ethylenically unsaturated dicarboxylic acids, such as maleic acid, fumaric acid, itaconic acid, are esterified with alkylene glycols or polyalkylene glycols having a molecular weight of up to 2000. Often dicarboxylic acids free of ethylenic unsaturation, such as phthalic acid, isophthalic acid, adipic acid, and succinic acid, are used per mole of unsaturated dicarboxylic acid.
It can be used in a range of 0.25 to 15 moles. It is understood that suitable acid anhydrides are preferred when present, usable and commonly available.

The glycol or polyhydric alcohol component of the polyester is usually stoichiometric or in slight excess with respect to the amount of acid. Excess amount of polyhydric alcohol rarely exceeds 20-25%, and usually 10-15%
It is.

These unsaturated polyesters are generally prepared by preparing a mixture of the polyhydric alcohol and the dicarboxylic acid or dicarboxylic acid anhydride in appropriate molar ratios at high temperature, usually 150
Generally made by heating at ~225°C for 1 to 5 hours. It is advantageous to add a polymerization inhibitor such as t-butylcatechol. Unsaturated polyesters can be made directly from slightly more suitable oxides than glycols. For example, propylene oxide can be used in place of propylene glycol. Generally, the condensation (polymerization) reaction is carried out with an acid content of 2-12% (-COOH) and preferably 4-8%.
Continue until it reaches %.

Yet another embodiment of this invention utilizes vinyl ester/unsaturated polyester resin compositions. The composition has a desired weight proportion of 2
The vinyl ester resin can be prepared by physically mixing two resins or by preparing the vinyl ester resin in the presence of the unsaturated polyester.

Although the concept of the present invention is operable with waste that is only organic, it is preferred that a sufficient amount of water be present. The water in the dispersion helps control water generated during curing. The presence of water is particularly important when large quantities of cured resin are used and exotherm control by multiple means becomes difficult. Water is also an aid in curing systems that helps create a homogeneous dispersion and passes various requirements and regulations such as the United States Department of Transportation Fire Test. In addition, the water is a viscosity aid to prevent separation of the waste prior to gelation.

The water may be present in the waste, may be added to the waste prior to dispersion, or may be added to the resin to form an emulsion, and then the waste in swollen beads. Add to the emulsion. When adding the water to the waste, the water can be mixed with the waste before absorption, or the waste can be absorbed and then the water added to form an aqueous slurry.

The ratio of swollen particles alone or included to the resin phase is 0.1 to 3 parts of swelling beads + water to 1 part by weight of resin.
Can vary within parts by weight. Preferably, the waste-in-resin dispersion is prepared to contain 1 to 1.5 parts by weight of waste plus water per part by weight of resin.

In practicing the process of this invention, the dispersion of waste in vinyl ester or unsaturated polyester resin can be prepared in a variety of ways. Generally a free radical generating catalyst is mixed with the resin phase and the radioactive waste is absorbed into the beads,
It is then dispersed into the resin under conditions to form a uniform water-in-resin dispersion. Although the shear conditions can vary over a wide range, generally when free water is present with the waste, sufficient shear should be applied to produce a uniform emulsion of droplet sieves.

The dispersion should have sufficient storage stability to at least outlast the initial gelation of the resin. Dispersions made of vinyl ester resins, especially vinyl ester resins within the monomer proportions mentioned above, generally exhibit sufficient stability without the addition of emulsifiers.
Dispersions of swollen resins in water to be dispersed in unsaturated polyesters often require added emulsifiers. Such emulsifiers are known and an astute selection to obtain closed cells can be made with simple routine experience. In many instances, especially carboxyl-terminated polyesters, the carboxylic acid sodium salt will emulsify the waste without the addition of an emulsifier.

Catalysts that can be used for curing or polymerization include peroxides such as benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, methyl ethyl ketone peroxide, t-butyl perbenzoate, and potassium persulfate. and a hydroperoxide catalyst. The amount of catalyst added will vary, but preferably at least
It is 0.1% by weight.

Preferably, the curing of the dispersion is carried out using, for example, tin or cobalt naphthate, usually in an amount of 0.01 to 5 wt%.
N,N-dimethylaniline, N,N-dimethyl-
It can be started at room temperature by addition of known accelerators or enhancers such as p-toluidine and vanadium neodecanoate. Alternatively, the catalyst can be added to the resin before dispersing the waste, and then the promoter is added after the dispersion is formed. The accelerator-added dispersion can be easily cured to at least the gel state in a short period of time, e.g. 3-30 minutes, and to the solid state in 30 minutes to 2 hours, depending on the concentration of accelerator and catalyst. Can be easily hardened to Curing of the dispersion can be initiated by heating to a temperature below 100°C or the boiling point of the organic liquid (whichever is lower). Thermoset products that are post-cured at elevated temperatures for varying times can be utilized with this invention.

The selection of catalyst, catalyst concentration, promoter selection and promoter concentration are determined by the exothermic temperature until the resin is cured to the point where it is strong enough to withstand increased vapor pressure if the temperature or below limits are exceeded. should be determined so that it does not exceed at least the above range. If the temperature exceeds 100° C. before curing, the water in the liquid waste will boil, which will dissociate the waste material or the organic liquid can dissociate from the swollen particles. Its solidification is 55 gallons (28
) can be carried out in a suitable container such as a drum.
Larger or smaller containers can be used, depending on handling and shipping limitations, available equipment and the amount of waste to be treated. As the size of the container increases, it becomes more difficult to maintain control of heat generation within the limits mentioned above. In such cases, it is desirable to adjust the amount of water, catalyst concentration and promoter for its control.

The process of the invention is illustrated in the examples below, in which all parts and percentages are by weight unless otherwise indicated.

Example 1 Radioactive waste containing 0.04 microcuries per ml of carbon-14 and tritium in toluene mixed with water was solidified in the following manner. The liquid contained 10% toluene and 90% water.

To 75 ml of well-shaken sample was added 0.38 g of a composition consisting of an absorbent, lightly crosslinked tertiary butyl styrene polymer in the form of small beads and ground polyethylene foam. The composition is disclosed in U.S. Patent No.
Described in No. 4172031. After a few minutes, the beads rose to the surface and phase separation occurred. The aqueous phase was decanted and emulsified in 50 g of vinyl ester resin containing 1.5 g of a catalyst composition of 40 wt% benzoyl peroxide emulsified in diisobutyl phthalate. The vinyl ester resins used were 0.25 equivalents of diglycidyl ether of bisphenol A (EEW=188) and 0.75 equivalents of epoxy novolak. The resin contained 36% styrene as a copolymerizable monomer.

The swollen beads were added to a water-in-resin emulsion along with 0.13 ml of dimethyltoluidine.

The composition gelled in 5.8 minutes and became hard overnight.

Test samples were made by curing the dispersion described above in nylon molds 2 inches (5 cm) long and 0.5 inches (12.77 mm) in diameter. With water extraction, radioactive leakage in 24 hours was 2.2% for carbon-14 and 1.5% for tritium.

Example 2 The same radioactive waste used in Example 1 was made of a polyester resin obtained from PPG Industries, Inc. sold under the trade name Selectron SR-3703 and 2.5 phr of the catalyst of Example 1.
The gel time solidified using (parts per 100 parts of resin) and 0.2 phr dimethyltoluidine was 6.8 minutes, and the sample solidified in 30 minutes.

Claims (1)

[Scope of Claims] 1. A method for encapsulating low concentration radioactive, liquid, water-insoluble organic waste in a solid form suitable for burial underground, comprising 1 part by weight of said waste and granular cross-linked swellable in radioactive organic liquid waste;
less than 1 part by weight of an insoluble polymer is contacted with radioactive organic liquid waste to form dispersed, non-agglomerated, gelled particles of said polymer and said waste, and unsaturated polyester resin, vinyl ester resin and 0.1 to 3 parts by weight of the gelled particles are substantially uniformly dispersed in 1 part by weight of a curable liquid resin selected from the group consisting of mixtures thereof, and the liquid resin is cured and encapsulated therein. A method of encapsulating radioactive waste by forming a solid with gelled particles. 2. The method of claim 1, wherein the radioactive organic liquid waste swellable and insoluble polymer is a crosslinked copolymer of tertiary butylstyrene and styrene. 3. A method according to claim 2, wherein the copolymer is crosslinked with divinylbenzene. 4. The method of claim 1, wherein the liquid organic waste is a hydrocarbon. 5. The method of claim 1, wherein the liquid organic waste is an aqueous dispersion of a radioactive, water-insoluble liquid substance. 6. The method of claim 5, wherein the organic liquid insoluble polymer is added to the aqueous dispersion and the aqueous dispersion and dispersed gelling particles are encapsulated within the curable liquid resin. 7. The organic liquid-insoluble polymer is added to the aqueous dispersion, the phases are separated, the water is stirred into the liquid-curable resin to form a water-in-resin emulsion, and then directly into the emulsion. 6. A method according to claim 5, comprising mixing gelling particles.