JPS61239198A - Method of solidifying and treating radioactive waste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] - The present invention relates to a method for solidifying radioactive waste, particularly dry radioactive waste.

One of the important issues related to the use of nuclear power is the disposal of radioactive waste. For example, various radioactive wastes are generated from nuclear power plants and the like, and these radioactive wastes must be solidified to ensure safety during transportation, storage, and disposal.

[Conventional technology]

Conventionally, methods for solidifying radioactive waste, particularly dry radioactive waste, include solidifying radioactive waste with cement or asphalt. However, in these solidification methods using cement or asphalt, the proportion of radioactive waste that can be mixed into the solidified material is small, so if you try to solidify a certain amount of radioactive waste, the volume and weight of the final solid mass will be large. However, there was a problem in that the volume reduction property decreased. Furthermore, the cement solidification method has the disadvantage that the assimilated material obtained has poor water resistance, and the asphalt solidification method has the drawback that the mechanical strength of the obtained solidified material is low.

Recently, various types of dry radioactive waste have been mixed with thermoplastic resins such as polyolefin resins and thermosetting resins such as unsaturated polyester resins in a molten or liquid state.
After that, the radioactive waste is made into a solid mass by means such as cooling, heating using a catalyst, or by adding a thermoplastic resin as a binder to the dried radioactive waste and melting and kneading it in an extruder to form a solid particle. Methods have been developed to solidify and store this in storage tanks or drums. However, the former method, that is, the method of turning radioactive waste into a solid lump of plastic, is superior to solidification methods using cement or asphalt in terms of volume reduction, mechanical strength, and leachability. The waste filling rate (dry waste type t/weight of plastic binder) #i that could be mixed in the mixing device was at most about 1, and was still insufficient in terms of volume reduction. In addition, the latter method, that is, the method of solidifying plastic into particles, has a waste filling rate of about the same level, but has the disadvantage that the mechanical strength of the final particles is low.

[Problem that the invention seeks to solve]

The present inventors have improved the shortcomings of the conventional solidification treatment method using plastics, and have developed a plastic solidification method that has excellent volume reduction properties and can yield a solidified product with better mechanical strength at the same waste filling rate. As a result of intensive research to develop a method, it was found that in addition to a polyolefin resin binder, a specific amount of a modified olefin polymer was added to the radioactive waste as the first component to achieve this purpose. The inventors have completed the present invention by discovering that the following can be achieved.

Structure of the Invention [Means for Solving the Problem] The present invention provides 100 parts by weight of dry radioactive waste (A):
Ka, 1. O L/74:/ Jam (13)yo~ioo□-□' 2,7-, Yayaou8
, 7.0&-/0 parts by weight of a modified olefin polymer (Ct) containing at least one group selected from a ter group, an acid amide group, an acid imide group, and an acid metal base. The present invention relates to a method for disposing of radioactive waste, which is characterized by kneading.

Dry radioactive waste to be treated in the present invention is radioactive waste generated from nuclear power plants, nuclear fuel reprocessing facilities, etc., with a water content of 3% by weight or less;
Alternatively, radioactive waste from nuclear power plants, nuclear fuel reprocessing facilities, etc. is dried until its moisture content is 3% by weight or less. The following are examples of radioactive waste generated from nuclear power plants, nuclear fuel reprocessing facilities, etc.

(→ The particle size of the used ion exchange resin is approximately 0.3'% da granular No. 4 and Bakudex (
There is a powdery substance called Powdex (product name).
Boiling water reactor (BWR) reactor water purification system, condensate desalination system,
They occur in fuel pool water desalination, radioactive waste liquid treatment systems, etc., and in pressurized water reactors (PWRs), bypass purification systems (purification desalination, deboration), fuel pit desalination, extracted coolant treatment systems, etc.

(It refers to the evaporation and concentration of chemical waste liquid (resin recycling waste liquid, etc.) and has a water content of around 10%), and its main component is Na25O4 (sodium sulfate or sulfate).

(c) Contains corrosion products generated from equipment and piping.
Waste liquid (referred to as crud) generated from equipment and piping that comes into contact with liquid.

F620! is the main component.

(d) Filter sludge Generated from filtration of equipment drains, floor drains, etc.

The main ingredient is a pulp-like fine powder filter aid.

(6) Incineration ash Exit the incinerator.

(1″) Washing liquid waste Occurs when workers wash contaminated clothing.

The present invention makes it possible to reduce the volume of radioactive waste, preserve it for a long period of time, and facilitate its storage and transportation by drying the radioactive waste and turning it into particles using a binder. It is something.

(g) Coagulation and sedimentation sludge (h) Waste activated carbon (1) Waste silica gel θ) Waste Molecule Error Sheep These radioactive wastes can be dried using r1) tgJ dryer, fluidized bed dryer, vertical centrifugal thin film dryer, etc. It is dried using a dryer until the moisture content is usually 3.0% by weight or less, preferably 2.0% by weight or less.

Incidentally, since some of the incineration ash, waste activated carbon, waste silica gel, and waste molecular sieve are dry themselves, there is no need to dry them using a dryer.

(9) As the polyolefin resin used as a binder for dried radioactive waste in the present invention, (3) homopolymers of α-olefins such as ethylene, propylene, butene-/, <<-methyl-7-pentene, and hexene-1; or with one of the above α-olefins such as ethylene-7'a-H L/-7 copolymer, propylene-ethyl L/7 copolymer, butene-7-ethylene copolymer, and ethylene-dermethyl-/-pentene copolymer. Examples include copolymers with other α-olefins or copolymers of α-olefins with other polymerizable monomers of 15 molar or less, such as ethylene-vinyl acetate copolymers.

Among these polyolefin resins used in the present invention, the melt index (ASTM-D-
723g-6! However, propylene (measured by JOC) is in the range of o, oi to 3o, and its density is 0.
t O-0.9g J//ln', especially 0.9θ~0°? 71)/cys' is preferred.

Further, the crystallinity of the polyolefin resin used in the present invention as determined by X# analysis is usually about 100% or more, particularly preferably about 0000000000000000000000000000000000000000000 or more. Particularly preferred types of polyolefin resins among the above polyolefin resins include polyethylene, polypropylene, polybutene, hyethylene-propylene copolymer, and ethylene-gumethyl-l-pentene copolymer.

In addition, the modified olefin polymer (C) used as the t-th binder component in the present invention has a carboxylic acid group in the polymer,
It is an olefin polymer containing at least one group selected from acid anhydride groups, carboxylic ester groups, acid amide groups, acid imide groups, and acid metal bases.

These modified olefin polymers can be obtained by, for example, the following methods: (1) a method of grafting at least one monomer selected from unsaturated carboxylic acids or derivatives thereof onto the olefin polymer (2) ) A method of copolymerizing an olefin and at least one type of hexamer selected from unsaturated carboxylic acids or derivatives thereof. Olefin polymers are preferred.

In the grafting method (1), examples of the olefin polymer used as a raw material for the modified olefin polymer include evaporated ethylene,
Propylene, l-butene, /-pentene, J-methyl-
α-ole Q4 homopolymer such as /-butene, l-hexene, dermethyl-/-pentene, or one of the above monomers and 30
Examples include copolymers with other α-olefins having a molar ratio of less than io molar, preferably polymers having a crystallinity of 23 or more as determined by X-ray analysis. Among these, medium and high density polyethylene and polypropylene are particularly preferred.

Furthermore, the monomer grafted onto the olefin polymer is an unsaturated carboxylic acid or a derivative thereof.

Examples of unsaturated carboxylic acids include acrylic 1).
acid, methacrylic acid, maleic acid,
Examples include fumaric acid, itaconic acid, and citraconic acid. Derivatives of unsaturated carboxylic acids include acid anhydrides, esters, amides, imides, metal salts, etc., such as maleic anhydride, citraconic anhydride, itaconic anhydride, methyl acrylate, methyl methacrylate, and acrylic acid. Ethyl, ethyl methacrylate, butyl acrylate, butyl methacrylate, glycidyl acrylate, glycidyl methacrylate,
Maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl ester, itaconic acid diethyl ester 1, 791) 7ゞ1゛・ppv"7q)"s v4 / acid monoamide , maleic acid diamide, maleic acid-N-monoethylamide, maleic acid-N.

N-diethylamide, maleic acid-N-motuptylamide, maleic acid-N,N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, 7-rk acid-N-monoethylamide, fumaric acid-N,N-diethylamide, Fumaric acid-N-motuptylamide, 7malic acid-N, N-dibutylamide, maleimide, N-butylmaleimide, N
-Phenylmaleimide, sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate, and the like.

Among these, it is most preferred to use maleic anhydride.

As a method for grafting the above-mentioned monomer onto the olefin polymer, various known methods can be employed. For example, it is carried out by heating the olefin polymer and the grafting monomer at high temperature in the presence or absence of a solvent, with or without the addition of a radical initiator.

Other vinyl monomers such as styrene may be present during the reaction. The amount of grafted monomer of the olefin polymer (hereinafter referred to as grafting ratio) is:
It is preferred to adjust the amount to be in the range of 10-' to 10% by weight, preferably lo-4 to 3% by weight. The hokiolefin polymer may be partially or entirely grafted.

1. Also, the method for 1P is ・“chi”・joeV7 etc. 1””-fV747 and 7. ? ! J“
This is a method of directly copolymerizing unsaturated carboxylic acids such as acids and b-acid anhydrides and/or their derivatives according to a conventional method.

The olefin used in method (2) is:
Examples thereof include α-olefin inkers such as ethylene, propylene, butene, and dermethyl-/-pentene. Furthermore, as the unsaturated carboxylic acid or its derivative used as a copolymerization component, the same monomers as those used in the grafting method (1) can be used.

The content of unsaturated carboxylic acid units and/or derivative units thereof in the modified olefin copolymer obtained by the method (2) is usually /θ-4 to 10 molt, preferably lo
-4 to 73 molti.

In the method of the present invention, when radioactive waste is solidified with a polyolefin resin, adding a modified olefin polymer as the binder component in the first step improves the filling rate of the waste into the binder. Therefore, the amount of polyolefin resin necessary to solidify the waste into a solidified body with satisfactory mechanical strength is 5 to 100 parts by weight of polyolefin resin per 100 parts by weight of dry radioactive waste (A). In particular, 6 to 0 parts by weight are preferred. If the amount of the polyolefin resin is less than 3 parts by weight based on 100 parts by weight of the waste, workability during cross-talk will be extremely poor, and the mechanical strength of the obtained solidified product will also be reduced, which is not preferable.

Furthermore, if the amount of the polyolefin resin exceeds 100 parts by weight, the volume reduction properties will be poor and the efficiency of radioactive waste treatment will be reduced.

In addition, the amount of the modified olefin polymer (C) used as the third binder component in the method of the present invention is
A) /00 parts by weight, preferably 0.02 to 10 parts by weight, and preferably 1 to 3 parts by weight of FCO. If the amount of the modified olefin polymer is less than 0,000 parts by weight, there is no effect of improving the filling rate of the waste into the binder, that is, the effect of improving the volume reduction ability, and the amount of the modified olefin polymer is less than 100% by weight.
If the amount exceeds this amount, the workability during kneading will deteriorate.

To solidify radioactive waste in the method of the present invention, 1 to 100 parts by weight of polyolefin resin (B) and 0.0 to 0.0 g of modified olefin polymer (C) are added to 00 parts by weight of dry radioactive waste (A). Part by weight of IO is added, and the mixture is melt-kneaded at a temperature above the melting point of the polyolefin resin and modified olefin polymer (1) at a temperature of 0 to 270 °C, and then left at 20 to 30 °C, or cooled with cooling water. The polyolefin resin and the modified olefin polymer are cooled to a temperature below the melting point of the polyolefin resin and the modified olefin polymer by washing with a solvent or the like to form a solidified product. The mixing method and the equipment used therefor can be selected depending on the shape and size of the solidified product to be obtained. For example, dry radioactive waste, a polyolefin resin, and a modified olefin polymer are added to a drum, and heated to a temperature higher than the melting point of the polyolefin resin and modified olefin polymer from the outside of the drum, usually from /10 to body 01.
There is a method of kneading and then cooling to form a solid mass.

When i-tactic radioactive waste is solidified into pellets (particulates) for the purpose of storage or storage, the radioactive waste, polyolefin resin, and modified olefin copolymer are first mixed in a Henschel mixer, and then this The mixture is heated in a single-screw or twin-screw extruder at a temperature higher than the melting point of the polyolefin resin and modified olefin polymer, usually /#0-,
Knead and extrude at 270r, cut the extruded strand, and granulate. The obtained particulate solidified material can be stored until disposal is decided, or the particulate solidified material can be filled into a mold, compressed to form a volume-reduced solidified material, and then disposed of. You can also do it. Although there are no particular limitations on the shape and size of the solidified product obtained in the present invention, the method of the present invention is particularly preferred when the final solidified product is formed into a pellet-like solidified product.

Effects of the Invention In the method of the present invention, when dry radioactive waste is solidified, a specific modified olefin polymer is added as a binder component in addition to the sibori olefin resin. In contrast, the amount of waste that can be mixed in (waste filling rate), that is, the ability to reduce the volume, can be significantly improved, and at the same waste filling rate, the mechanical strength of the solidified material obtained can be further improved. became possible.

Example 1 As a simulated radioactive waste, anhydrous sodium sulfate (reagent/grade manufactured by Wako Tsumugi Pharmaceutical Co., Ltd., density θp/l: m", average particle size 0μ) was used, and 90 parts by weight of this anhydrous sodium sulfate , 99 parts by weight of polypropylene resin as a binder [density: θ, ri/rn", melt index: /, s (co30υ, co1bKp) Modified polypropylene polymer obtained by graft polymerization of J, θ weight % of maleic anhydride on (for)
After mixing for 1 minute with an ooorpa, this mixture was introduced into a single screw extruder and extruded with a screwdriver at a screw speed of AOr%, and the extruded strands were cut to form particulate solidified radioactive waste. Obtained.

The physical properties of this solidified product are shown in Table 1.

Example A particulate solidified product of anhydrous sodium sulfate was produced in the same manner as in Example 1, except that the blending amounts of polypropylene resin, maleic anhydride, and modified polypropylene were changed as shown in Table 1. Table 1 shows the physical properties of the obtained solidified product.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the modified polypropylene was not added in Example 1 and 10 parts by weight of polypropylene resin was added instead. The results are shown in Table 1.

Example 3~'l! In Example 1, polybutene resin (density: O, decoction f
i/1m', melt index=0.03(/90υ
, ko, 1aKp)) or polyethylene resin [density:
o,qs 4! A particulate solidified body of anhydrous sodium sulfate was obtained in the same manner as in Example 1 except that 1)/lx*', melt index: /, 3) I (1901::, ko, 1xKp)) was used. The results are shown in Table 1.

Comparative Example The same procedure as in Example 1 was carried out except that in Example &, modified polypropylene was not added and 70 parts by weight of polybutene resin was added instead. The results are shown in Table 1.

Claims (4)

[Claims] (1) For 100 parts by weight of dry radioactive waste (A), 5 to 100 parts by weight of polyolefin resin (B) and carboxylic acid groups, acid anhydride groups, carboxylic acid ester groups, acid amide groups, acid imide groups, and acid Modified olefin polymer (C) containing at least one group selected from metal bases 0.05
A method for solidifying radioactive waste, which comprises adding ~10 parts by weight and kneading. (2) The method according to claim (1), wherein the polyolefin resin (B) is polyethylene, polypropylene or polybutene-1. (3) The modified olefin polymer (C) is an olefin polymer grafted with at least one monomer selected from unsaturated carboxylic acids or derivatives thereof. ). (4) The method according to any one of claims (1) to (3), wherein the solidified material is in the form of pellets.