JPH0646238B2 - Method for solidifying radioactive waste silica gel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for solidifying radioactive waste, particularly radioactive waste silica gel containing an aliphatic hydrocarbon solvent.

(Prior Art) One of the important problems related to the use of nuclear power is the treatment of radioactive waste. For example, various kinds of radioactive waste are generated from a nuclear power plant. Generally, these radioactive wastes must be solidified to ensure their safety during transportation, storage and disposal.

Conventionally, the method for solidifying radioactive waste is to solidify the radioactive waste with cement or asphalt and store it in a waste storage facility, or dump it into the ocean. However, the solidification method by (1) was not satisfactory in terms of volume reduction because the final solid mass increased in volume and weight.

Therefore, the applicant of the present invention has recently proposed, as a further improved method, a method of mixing radioactive waste with an epoxy resin and curing the same to carry out a solidification treatment. (JP-A-58-219499) However, when radioactive waste silica gel containing 15 to 50% by weight of an aliphatic hydrocarbon solvent such as n-dodecane is solidified by this method, the solidified product after solidification treatment is used. Not only has the disadvantage of solvent leaching, but when the radioactive waste silica gel and the epoxy resin are mixed, the viscosity of the mixture is large and therefore the workability is poor, and when a curing agent is added to this and it is solidified at room temperature. Since a large amount of reaction heat is generated, when manufacturing a solidified body with a large volume of about 1 or more, the temperature of the solidified body central part becomes adiabatic and solidified, so the temperature becomes too high, and voids and cracks are generated, and burned out. There was a problem such as.

(Problems to be Solved by the Invention) The present inventors have solved these problems, and when solidifying radioactive waste silica gel containing 15 to 50 wt% of an aliphatic hydrocarbon solvent, Prevents the solvent from leaching from the solidified body, and further improves the strength and water resistance of the solidified body. In addition, the content of radioactive waste silica gel in the solidified body is made as high as possible, and when the radioactive waste silica gel and the resin are mixed, As a result of research to develop a solidification treatment method that reduces the viscosity and controls the amount of heat generated during the curing reaction, the use of a specific epoxy resin as a solidifying resin and the use of this with a diluent and a specific polymer As a result, they have found that this object can be achieved and completed the present invention.

(Means for Solving Problems) and (Operation) That is, the present invention is to provide radioactive waste silica gel (A) containing 15 to 50% by weight of an aliphatic hydrocarbon having 8 to 14 carbon atoms.
General formula for 100 parts by weight 10 to 100 parts by weight of the epoxy resin (B) shown in 2
1 ~ of diluent (C) with a viscosity of 2000 cps or less at 5 ° C
The present invention relates to a method for solidifying radioactive waste silica gel, which comprises mixing 60 parts by weight and 1 to 10 parts by weight of polynorbornene (d) and curing the mixture.

The waste silica gel containing 15 to 50% by weight of the aliphatic hydrocarbon having 8 to 14 carbon atoms which is solidified in the present invention means
For example, in a nuclear power plant or a spent nuclear fuel reprocessing plant, etc., aliphatic hydrocarbons with 8 to 14 carbon atoms used to adsorb and remove radioactive nuclides, oil, water, etc. from the extraction solvent of metal compounds such as uranium and plutonium and radioactive waste liquid. It is an excess residue passed by a conventional method from a slurry mixture of waste silica gel contaminated with a radionuclide containing a hydrocarbon solvent by a known machine such as a vibrating sieve or a centrifuge, and is contaminated with the radionuclide. 50 to 85 parts by weight of the prepared silica gel and 50 to 15 parts by weight of an aliphatic hydrocarbon solvent having 8 to 14 carbon atoms which is contaminated with a radionuclide.

The aliphatic hydrocarbon solvent having 8 to 14 carbon atoms in the present invention is usually used as an extraction solvent for uranium and plutonium compounds in the order of extraction-distillation-adsorption dehydration on silica gel, and specifically Chain or branched octane, nonane, decane, undecane, dodecane, tridecane, and tetradecane can be exemplified.
-Dodecane is particularly preferably used.

Further, in the present invention, the epoxy resin used for solidifying the radioactive waste silica gel containing 15 to 50% by weight of the aliphatic hydrocarbon solvent having 8 to 14 carbon atoms (hereinafter simply referred to as radioactive waste silica gel) is represented by the general formula Is an epoxy resin.

These epoxy resins are usually liquid epoxy resins at room temperature and have a viscosity of 2,000 to 200,000 cps.
Is in the range.

Specific examples of these epoxy resins include, for example, Is mentioned.

It is preferable to mix 10 to 100 parts by weight of these epoxy resins with 100 parts by weight of radioactive waste silica gel.

If the mixing amount of epoxy resin is less than 10 parts by weight with respect to 100 parts by weight of radioactive waste silica gel, not only a strong solidified product cannot be obtained, but also the water resistance and the ability to confine radioactive substances are not sufficient, and 100 parts by weight. If the temperature exceeds the above range, the heat generated during curing is intense, and when producing a solidified body with a volume of about 1 or more (particularly a solidified body of drum can size 80 or more), the center of the solidified body becomes an adiabatic state, so the temperature of the center is high. Is too high, cracks are generated due to voids and stress strain, and moreover, it is scorched, which is not preferable.

In the present invention, the particularly preferable mixing amount of the epoxy resin is 20 to 60 parts by weight based on 100 parts by weight of the waste silica gel.

In the present invention, it is essential to use a diluent when mixing the radioactive waste silica gel and the epoxy resin.

In the present invention, the diluent is used for adjusting the viscosity of the compound, controlling the heat generation during curing, and improving the crack resistance of the solidified product.

The diluent used in the present invention is a reactive diluent or a non-reactive diluent, and has a viscosity of 2000 cps or less, particularly preferably 1000 cps or less. As the reactive diluent, an epoxy compound having a viscosity of 2000 cps or less, for example,
General formula A monoglycidyl ether, n-butyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether, C ₁₂ C ₁₃ mixed glycidyl ether (C ₁₂ : 55% C ₁₃ : 45%) and polyoxyalkylene glycol diglycidyl ether, Examples thereof include polyepichlorohydrin diglycidyl ether and epoxy compounds of alicyclic hydrocarbon.

Examples of non-reactive diluents include aromatic or alicyclic hydrocarbon solvents having 9 to 12 carbon atoms such as decalin, methylnaphthalene, indene, cumene, cymene, and alkyl-substituted benzene, dimethyl phthalate, diethyl phthalate, di-n. -Octyl phthalate diethyl phthalate, di- (2-ethylhexyl) phthalate, phthalates such as diisobutyl phthalate, butylphenol,
Alkyl group-substituted phenols such as hexylphenol, octylphenol, nonylphenol, and coumarone, indene, α-methylstyrene, isopropenyltoluene, styrene, ethyl acrylate, acrylic acid esters such as methyl acrylate, methyl methacrylate,
Examples include so-called aromatic polymerized oils, which are obtained by polyaddition condensation of a methacrylic acid ester such as ethyl methacrylate, phenol, an alkyl-substituted phenol, formalin, etc., with a cation catalyst.

Among them, a particularly preferred diluent in the present invention has a viscosity of 1
~ 500 cps, glycidyl ether having an oxygen content in the molecule of 25% by weight or less, specifically butyl glycidyl ether, hexyl glycidyl ether, nonyl glycidyl ether, decyl glycidyl ether, dodecyl glycidyl ether, tetradecyl glycidyl ether, alkyl Examples thereof include monoglycidyl ethers such as substituted phenylglycidyl ethers and polyepichlorohydrin diglycidyl ethers.

Such a reactive diluent may be used in combination with a non-reactive diluent in order to control the heating value thereof.

The amount of the diluent used is 1 to 60 parts by weight, preferably 2 to 50 parts by weight, based on 100 parts by weight of radioactive waste silica gel. When the amount of the diluent added is less than 1 part by weight with respect to 100 parts by weight of radioactive waste, the viscosity of the solidification treatment liquid is high, stirring is difficult, the dispersion of radioactive waste in the solidified body is poor, and the dispersibility is good. No solidified product can be obtained. On the other hand, if the amount exceeds 60 parts by weight, the strength, water resistance and leaching resistance of the solidified product are deteriorated, which is not preferable.

Further, the compounding amount of the diluent with respect to the epoxy resin which is a solidifying agent is usually preferably in the range of 3 to 150 parts by weight, and particularly preferably in the range of 5 to 100 parts by weight, relative to 100 parts by weight of the epoxy resin.

In the present invention, in order to control the heat generation during the solidification treatment of radioactive waste, the average specific heat per 1 kg of the total liquid mixture containing radioactive waste, epoxy resin, diluent, curing agent, and additive, _p Kcal / Kg · ° C. Total calorific value of epoxy resin of compounded epoxy resin and reactive diluent Q Kcal / Kg (where Q is the molar heat of reaction of epoxy group is ΔH Kcal / mol and epoxy content is A mol / Kg, Q = The temperature increase Δt (where Δt = Q / _p ) calculated from ΔH × A is 30 to
The temperature is preferably 120 ° C, preferably 50 to 100 ° C.

If the temperature rise Δt exceeds 120 ° C, the temperature of the central part of the solidified body becomes too high, resulting in voids, cracks, lowering of strength, and burning, and if Δt is less than 30 ° C, solidification occurs. Not only is the time required increased, but the strength of the solidified product obtained is also reduced, which is not preferable.

In the present invention, when the radioactive waste is cured with an epoxy resin and a diluent, a small amount of polynorbornene (d), which is a polymer capable of absorbing an aliphatic hydrocarbon having 8 to 14 carbon atoms, is further contained together with the epoxy resin and the diluent. Mix and solidify. By thus mixing the polynorbornene (d), exudation of a liquid containing an aliphatic hydrocarbon solvent having 8 to 14 carbon atoms as a main component from the solidified body is prevented, and the strength of the solidified body is improved.

The mixing amount of this polymer with respect to the waste silica gel is 1 to 10 parts by weight, particularly preferably 1 to 5 parts by weight, based on 100 parts by weight of the waste silica gel.

When the amount of the polymer mixed exceeds 10 parts by weight, the viscosity of the mixed solution before solidification increases and stirring becomes difficult, and the strength of the solidified product is not good, which is not preferable.

Further, in the present invention, in order to prevent sedimentation of radioactive waste during stationary curing after mixing radioactive waste silica gel and epoxy resin, colloidal silica (aerosil), pentonite, thixo acid such as oxalic acid treated pentonite. A defoaming agent such as a silicone coil or a dehydrating agent such as calcium oxide or molecular sieve can be added to the agent for imparting a property, or for preventing bubble foaming.

In the present invention, when the radioactive waste silica gel (A) is solidified with the epoxy compound (B), in order to further improve the mechanical strength of the solidified product obtained, the epoxy compound
In addition to (B), the diluent (C) and the polynorbornene (d), an inorganic filler may be further mixed.

As the inorganic filler used in the present invention, calcium carbonate, magnesium carbonate, silica, silica / alumina, alumina, glass powder, glass beads, glass fiber, asbestos, mica, graphite, carbon fiber, whiskers / titanium oxide, disulfide. Molybdenum, beryllium oxide, barium sulfate, magnesium oxide, calcium oxide, magnesium hydroxide, calcium hydroxide, talc,
Examples thereof include kaolin, acid clay, activated clay, attablelite, glandite, generalite, bentonite, diatomaceous earth, montmorillonite, dolomite, wax stone, clay minerals such as vermiculite, activated carbon, metal powder, and gold fiber. These inorganic fillers are non-radioactive,
It may be radioactive.

The blending amount of the inorganic filler is preferably 1000 parts by weight or less with respect to 100 parts by weight of the foamed waste silica gel.

To solidify the radioactive waste silica gel in the present invention, first, the radioactive waste silica gel described above and 10 to 100 parts by weight, preferably 20 to 60 parts by weight, of the epoxy compound (B), 1 to 6 per 100 parts by weight of the radioactive waste silica gel are used.
0 parts by weight, preferably 2 to 50 parts by weight of dilution (C), 1
10 parts by weight of polynorbornene (d) and a curing agent for curing the epoxy resin are uniformly mixed with a mixer having a stirring blade, a static mixing stirrer, or the like. The amount of the curing agent used is suitably 0.5 to 2 times the theoretical amount required to cure the epoxy resin. The mixing order of each component is not particularly limited, but it is generally preferable to first mix the epoxy resin and the diluent, the radioactive waste, and the polynorbornene, and then add and mix the curing agent.

As a curing agent to be added to cure the epoxy resin in the present invention, a chain aliphatic polyamine such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenediamine or diethylaminopropylamine; a cycloaliphatic polyamine; Aliphatic polyamine adducts; ketoimines; modified aliphatic polyamines; polyamidoamines; aromatic amines; aromatic modified amines; aromatic modified polyamines; tertiary amine curing agents; mercaptan curing agents; acid anhydrides -Based curing agents; copolymers having acid anhydride groups such as ethylene-maleic anhydride copolymers; compounds having phenolic hydroxyl groups such as novolak type or resol type phenol resin initial condensates; dicyandiamide; With curing agents for epoxy resins such as melamine Although any known compound can be used, in the present invention, from the viewpoint that the radioactive waste mixed liquid can be cured at room temperature, a polyamine type curing agent, specifically diethylenetriamine, triethylenetetramine, Chain aliphatic polyamines such as tetraethylene / pentamine, hexamethylenediamine, xylylenediamine and N-aminoethylpiperazine, cyclic aliphatic polyamines such as isophoronediamine, menthanediamine, cyclohexylamine and bicyclodecanediamine, polyamidoamine, aromatic Amines, epoxy adducts of these polyamines, Mannich adducts, Michael adducts, ketimine adducts are preferred.

Further, in the present invention, in addition to these components, a compounding agent such as a curing accelerator may be added if necessary.

The addition amount is 0.
It is 01 to 3 PHR.

Next, in order to solidify this mixture, the reaction rate between the epoxy resin and the curing agent is usually 65% or more, preferably 70% or more, until the solidified body from which the epoxy resin is obtained has sufficient strength. Cure until The curing condition is 5 ° C or higher, preferably 15 ° C to 80 ° C, and 5
It is usually left for 5 minutes to 10 hours or more.

(Effects of the Invention) In the present invention, the amount of the aliphatic hydrocarbon having 8 to 14 carbon atoms is 30
When the radioactive waste silica gel containing ~ 50 wt% is solidified with an epoxy, a specific epoxy resin is used as a solidifying resin, and a diluent and polynorbornene (d) are mixed with the epoxy resin, resulting in excellent strength and water resistance. , A solidified product without solvent exudation is obtained, and the viscosity when mixing radioactive waste silica gel and epoxy resin is reduced,
Also, the heat generation during the curing reaction can be controlled, a solidified body with a high radioactive waste content (high volume reduction ratio) can be obtained by a simple process, and the void volume of the obtained solidified body can be reduced. Became.

Example 1. A stirrer having a pitch paddle type blade (two stages) with a span of 300 mm was installed in a 100 drum having a diameter of 450 mm and a height of 700 mm.

Next, 60% by weight of spherical silica gel (Fuji Davison, trade name Microbeads 3A; 50 to 150 mesh), n-
Simulated waste silica gel 57.6 consisting of 40% by weight of dodecane
Kg, Phenol-modified aromatic polymerized oil (Tokyo resin industry, trade name: Shintalon ^# 370; 25 ° C viscosity 1500cps) 1
4.6 kg, bisphenol A diglycidyl ether type liquid epoxy resin (Mitsui Petrochemical Co., Ltd., trade name Epomic R-140, epoxy equivalent 189, 25 ° C. viscosity 130
00 cps) 14.6 Kg was added, and the mixture was stirred at 240 rpm for 1 hour and uniformly mixed. Next, polynorbornene (molecular weight 300
10,000 or more, density 0.96, bulk specific gravity 0.30, average particle size 0.
1.9 kg (3 to 0.4 mm, white powder) was added, and the mixture was stirred for about 30 minutes. Next, a polyamine curing agent (Mitsui Petrochemical Co., Ltd., Q637, active hydrogen equivalent 95, density 1.07, 25
℃ viscosity 9,000, modified metaxylylenediamine) 7.3
Kg was added. After stirring for about 15 minutes after the addition was completed, the stirrer was pulled out, and the drum containing the mixed liquid was solidified at room temperature (average temperature of about 25 ° C.). Approximately 1 hour after the addition of the curing agent, the liquid surface solidified to such an extent that it could not be left even if it was lightly pressed with a finger.
After solidification by touching with fingers, aging was carried out at room temperature, and one month later, physical properties were measured at 9 locations inside the solidified body, and an average value was obtained. The Shore D altitude was 49, the compressive strength was 170 kg / cm ² , and a homogeneous solidified body with no liquid bleeding or cracks and few bubbles was obtained (volume about 80).

This solidified body contained 60% by weight of silica gel containing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadao Iwata 912 Shiinazaki-cho, Chiba-shi, Chiba (56) References JP-A-58-219499 (JP, A) JP-A-59-32898 (JP, A) JP-A-59-208499 (JP, A)

Claims (7)

[Claims] 1. An aliphatic hydrocarbon having 8 to 14 carbon atoms is contained in an amount of 15 to
General formula for 100 parts by weight of radioactive waste silica gel (A) containing 50% by weight 10 to 100 parts by weight of the epoxy resin (B), 1 to 60 parts by weight of the diluent (C) having a viscosity of 2000 cps or less at 25 ° C., and 1 to 10 parts by weight of the polynorbornene (d) are mixed. A method for solidifying radioactive waste silica gel containing an aliphatic hydrocarbon, characterized by curing the. 2. The method according to claim 1, wherein the curing is performed with a polyamine type epoxy resin curing agent. 3. A process according to claim 1, wherein the diluent (C) is a reactive or non-reactive diluent. 4. The diluent (C) has a viscosity of 1 to 500 c at 25 ° C.
Claim 1 which is a compound containing an epoxy group of ps
Item 4. The method according to any one of Items 3 to 3. 5. The diluent (C) has a viscosity at 25 ° C. of 1 to 500.
The method according to claim 1, which is an epoxy group-containing compound having cps and an oxygen content in the molecule of 25% by weight or less. 6. The method according to claim 1, wherein the diluent (C) is an aliphatic, alicyclic or aromatic hydrocarbon having 10 to 12 carbon atoms, or a phenol formalin modified aromatic oil. The method described in any one of. 7. The method according to any one of claims 1 to 6, which is an aliphatic hydrocarbon n-dodecane.