JPS59128498A - Method of processing 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 The present invention relates to a method for treating waste, which is a combustible hybrid solid mixture containing radioactive materials.

Currently, mixed solid waste containing radioactive materials generated from nuclear power plants and facilities that handle radioactive materials is stored untreated (untreated), packed in containers such as drums, or stored in cellulose filter aids. materials, waste ion-exchange resins, etc. are stored in tanks in a mixed state with waste liquids, but in the future, the increase in the amount of storage of these materials will
Tank storage, which is unavoidable and mixed with waste liquid, poses safety problems, and there is an urgent need to develop practical treatment methods to solve these problems.

Compression, incineration, acid decomposition, and other methods for treating hybrid mixed solid waste are currently under development or in the stage of practical application, but the compression method has a low volume reduction ratio, and the incineration method has ,
Waste gas treatment equipment is required, which generates radioactive secondary waste, which negates the volume reduction effect of the incineration method and poses problems such as corrosion of the structural materials of the incineration II treatment facility.

A similar technology to this invention is the wet oxidation method (Z i
mpro method), but this tends to stop oxidation even in the form of organic acids. In order to improve this drawback and improve the degree of oxidation, it is known to add a catalyst such as copper ions. However, the conventional method involves continuously feeding organic acids contained in a large amount of water into an oxidation reactor.
It has the disadvantage of producing a large amount of waste water. Also, special public service 57-5
6796 contains radioactive waste ion exchange resin, filter sludge, rubber, or vinyl chloride resin.
A method is described in which the material is oxidized and decomposed with an oxygen-containing gas at 0 to 300°C and a pressure of 20 to 100 atmospheres, and the decomposition residue is solidified. In this method, whether continuous or batch, waste ion exchange resin, filter sludge, vinyl chloride resin, or rubber is supplied in the form of a slurry, and the necessary water is supplied during the evaporation and concentration process of the decomposition residue. Separated water is used, but this results in increased energy consumption for evaporation and condensation, and a water circulation system is required in the equipment to recycle and reuse water that may contain radioactive materials. Moreover, it complicates driving operations and is also unfavorable for reducing radiation exposure. Furthermore, continuous supply of slurry complicates the equipment and poses problems in terms of operational safety.

In addition, in this method, rubber and other materials are cut to the extent that they do not block the piping, and the size of the cuts not only affects slurry transportation, but also greatly affects the oxidative decomposition reaction time, and is economically important for reactor design. There is a problem with sweet 1-. In addition, when waste ion exchange resins, conjugated vinyl resins, etc. are oxidized and decomposed, the Pl-1 of the reaction solution becomes 4 or less, which may leave the reactor in a state where corrosion is likely to occur.

This invention is mainly used for middle and high level (50m ram 7I)
? To provide a method for cutting or crushing combustible miscellaneous solids containing radioactive substances (more than R) into appropriate sizes and conducting oxidation volume reduction treatment safely and efficiently while saving energy. The catalyst aqueous solution is used repeatedly and the miscellaneous solids are added to it in a state with almost no moisture entrained, and in semi-batch or batch processing, the organic components of the miscellaneous solids are completely converted into water and carbon dioxide. It is characterized by being oxidized to the extent of

In the sintering method, sox, NOx, 'CR2, H
Equipment for separating and removing acidic substances such as Cj, etc. from waste gas.
In the case of incineration of combustible miscellaneous solid waste (mrem/Ar or higher), radioactive materials infiltrate into the reactor mouth and mix into the high-temperature waste gas along with the incineration ash, resulting in considerable damage! ■Many issues remain unresolved, including the generation of radioactive secondary waste.

According to this invention, the organic components in the miscellaneous solids are completely reduced to water and carbon dioxide gas, so the volume reduction ratio is about 50%,
In addition, sulfur (S), nitrogen (N), chlorine (C
2) The constituent elements of acidic gases such as S are 804
N remains in the solution as -2 and becomes NH3 which remains in the solution or is easy to process as NH4+, and remains in the solution as C2-, so the waste gas contains SOx, N
Ox, CR2, HCR, etc. are almost absent. Further, the radioactive substances contained in the miscellaneous solids exist in the solution and are hardly contained in the exhaust gas. Therefore, in the exhaust gas treatment process, it is sufficient to install a simple device that prevents only the leakage of radioactive materials with a small diameter due to entrainment of some droplets.

In addition, depending on the type and amount of substances contained in the miscellaneous solid waste, if the concentration of 11 in the solution after the oxidation reaction is as low as about 1 m3, there is a problem of corrosion occurring in the material of the reactor, but CaC
o3 , Ca (OH) 2 , NaOH, ZnOl, etc., when the reaction is carried out by adding trivalent substances, -1 after the reaction
Up to 8F, there is no effect on oxidative decomposition and corrosion. iJ,
Selection of the material is easy.

The method of the present invention will be explained in detail below.

Medium to high level combustible miscellaneous solid wastes to be decomposed by the method of this invention include polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, neoprene, waste ion exchange resin, polyamide, polyester, acrylic resin,
Targets include filter aids, rags, gloves, (cotton blends), wood, duct tape, paper, rubber, and other polymer structures, and/or flammable materials made of polymers such as machine oil and grease. The combustible materials are in solid form or in water from the nuclear power plant J5 and other nuclear facilities (radioactive miscellaneous solid waste, etc.), either individually or in mixtures of each type. However, both can be oxidized and decomposed by the method of this invention.

These combustible miscellaneous solids maintain the shape they are used for, but they are difficult to handle in their original state.
Because the reaction takes a long time, the miscellaneous solid waste has a thickness of 20 mm.
It is preferable to cut or crush the material into pieces of 5wnn or less before oxidation treatment, which is extremely advantageous in terms of reaction rate.
The method of this invention is characterized by the use of metal ions as catalysts.

As metal ions, CLL", CLL", Co"
, Fe”, Fe゛3Pd”, Ce”, Nj”
, Cr", Mh', Pb", or a combination of two or more of them is used.

Among them, C,12, pd+2, Fe12 and Fe'
However, each is desirable alone or in combination of two or more.

Furthermore, even if a trace amount of other metal ions is present in the reaction solution, there is no adverse effect and oxidative decomposition is possible. The concentration of metal ions is 1
-2oooppm, preferably 1-11000 pl). The reaction temperature is in the range of 100-300°C, preferably 190-250°C.

The partial pressure of oxygen is 3 to 30 ka/c+fG, and pure oxygen and/or air can be used as the oxygen.

The decomposition reactor is of the aeration type; b or stirring type;
A combination of both methods as shown in the figure is preferred. An aqueous solution containing metal ions is held in a reactor 8, and after charging combustible miscellaneous solid waste that has been cut and crushed to a certain size or less, the reactor is heated and pressurized in a hermetically sealed manner, While supplying oxygen to a predetermined oxygen partial pressure, remove the gas from valve 2; keep the pressure inside the reactor constant;
The reaction is allowed to take place for 1 to 3 hours each time the miscellaneous solid is charged.

Even if some unreacted organic components remain in the solution, this reaction is repeated by heating, pressurizing, and oxygen supply until the aqueous solution in the reactor is almost saturated with the ash in the miscellaneous solids. Inject the miscellaneous solids into the? The oxidative decomposition is allowed to proceed for several hours without causing any damage, and the organic components are completely oxidized. Finally, the reaction solution is evaporated and concentrated to dryness to form radioactive waste whose volume has been reduced. In addition, an aqueous solution containing metal ions can be used repeatedly several dozen times (However, since the activity of the catalyst does not decrease, it can be used repeatedly until it is saturated with salts, etc.). , CaCO3,
NaOl-1,4 [Can be neutralized with any basic substance and evaporated to dryness, but the volume reduction ratio will be small.

In this invention, when heat-generating miscellaneous solid waste is subjected to wet oxidation under high temperature and high pressure, the metal ion aqueous solution can be used repeatedly, resulting in a large volume reduction ratio. Gas and water vapor (P is released, sox, NOx
, CR2, and HCR are substantially not emitted. Therefore, there is no need for complicated waste gas treatment processes such as incineration methods, and it is easy to select materials that are free from corrosion, resulting in many benefits in terms of safety, volume reduction, energy conservation, and economics. I can do it.

In other words, this method provides a method for efficiently reducing the volume of medium- to high-level combustible miscellaneous solid waste stored in facilities, where there has not been an appropriate volume reduction treatment method in the past, while saving energy. Furthermore, the wet oxidative decomposition residue obtained from the volume reduction treatment can also be solidified, opening the way to an effective final treatment method for medium to high level combustible miscellaneous solid waste.

The method of the present invention will be specifically illustrated by examples below.

Example 1 Crepe 71-1 with an internal volume of 500 xi shown in FIG. 1 was used, and as shown in Table 1, experiments (1) and i
In experiment 2, the mixture of substances to be decomposed was decomposed in each decomposition reaction column, and the first TOC of the solution after the reaction was measured.
(total organic carbon) amount was measured.

Next, the mixture and oxygen shown in each decomposition reaction condition were newly sealed in C, and a second reaction was carried out. Similarly, the reaction was repeated 15 times for experiment (2) and 13 times for experiment (2). As shown in Table 1, the residual 1' OC of the reaction solution after the oxidative decomposition reaction remained substantially constant, indicating that the activity of the catalyst did not deteriorate during use.

Please note a note regarding Table 1.

1) The mixture of substances to be decomposed in Experiment (2) was cut and crushed to a size that would pass through a sieve with an opening of 5 mm. Oh 1 for the first time
〜Elemental analysis of the mixture 2.591· which was supplied to the crepe − OC measurement value is 4941 I) I) Note 2) Positive and anion exchange resin mixture 1 which is the decomposition substance of experiment
TOC measurement value by elemental analysis of gr is 2170 pl
)nI.

Example 2 An autoclave with an internal volume of 500 xi as shown in FIG. After the reaction was completed and the reaction solution was cooled to the lowest temperature, the gas inside was released.

Sox, NOx, CRz, and HC in the released gas were measured using a Tregel R detection tube, but as shown in Table 2, none of them were detected.

After opening the autoclay 1 lid, the amount of residual TOC in the reaction solution is -1
-Measured by ○C analyzer, Note 3) TOC decomposition rate is
The results shown in Table 2 were obtained.

Next, I would like to make a note about Table 2.

Note 3) 700 min m1 - (Miscellaneous solids T OCm - amount of T OC remaining in the reaction solution) / Miscellaneous solids 1 - OC volume Oxidative decomposition was performed under each of the conditions shown in Table 1, and the TOC decomposition rate for each type was calculated.

In experiment (2), among the miscellaneous solids, a mixture of waste cloth, wood, paper, and a polyethylene bottle was subjected to oxidative decomposition under the following decomposition reaction conditions (1), and the 110C decomposition rate of the mixture was calculated.

115) Used as the substance to be decomposed in Example 2. 1=刹1
The solid used was cut to a size that could pass through a 5 mm sieve.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of O-1 to Crepe, which captures the aeration pipe stirrer 11-, which was used in the example. 1,...Gas filling RO, -valve 2,...Gas outlet valve 3,...Liquid sampling valve 4,...Stirrer 5,...Pressure gauge 6,...Safety valve 7, ...Electric furnace 8, ...O 1 to Crepe 9, ...Temperature 81 10, ... Diffusion tube (margin below) Table 1 Repeated experiment results Note 3) Experiment ■ Experiment ■ 1. Decomposition Reaction conditions '4 1) Amount of decomposed substance supplied (0) -Ian exchange resin Note 2) (PAO)
Mixture and cation exchange 1! ! ! ! Resin rig
(PCI-1> Note 1) Neoprene mixture and rag 2, 59 poly]-ethylene stool wood 2) Make-up distilled water volume 250 250 (ml)
) 3) Catalyst Cu SO4 river 500 500 (
ppm asQL, ) 4) Oxygen partial pressure 15 15 (kg/c
m'G) 5) Reaction temperature ('C) 230 2306)
Reaction time 33 2, residual TOC concentration in the reaction solution after oxidative decomposition reaction (ppm) 1st time 168 82 2, 179 943
174 85 4 181 84 5 185 81 6 19'3 887
179 93 8 166 90 9 1' 8.0 8210
183 8011 174
, 8912 175 86
13 181 8614
187 -15
185 - Table 2 Oxidative decomposition method experiment by miscellaneous solid type ■ Experiment ■ Experiment ■ 1. Decomposition reaction conditions 1) Amount of decomposed substance supplied ((]) 1 l-4 2) Make-up distilled water ffl 2.50 250 250
(ν1) 3) Touch WCuSO4m 500 500 500 (
ppm asQi) 4) Amount of basic substance ZnO ((1) None 1 None 5) Oxygen partial pressure 7 10 20 (ka/c
i) 6) Reaction temperature (°C) 230 240 2301) Reaction time (='tr) 1 1 38) p)-1-' of reaction solution before and after reaction 6.7-5.0 -2, by type of miscellaneous solids -r OC decomposition rate (%) Total 5) Experiment ■ Experiment ■ Experiment ■ Polyethylene bag 95.1 - - Neoprene 86.2 93.2 - Hard vinyl chloride 79.4 87.4 - Soft vinyl chloride sea) 83.7 - -Vorip] Pyrene 96.1 - -Rubber
92.4 - - Acrylic resin 96
．． 4 - - Polyvinyl chloride rib 82.1 -
-Nylon thread 67.8-
- Notes Measurement results of acidic gas in exhaust gas of experiments ■, ■, ■ SOx NOx Cj21'cR - Not detected -
- 1 - Non-detection Non-detection - Non-detection Non-detection Non-detection Non-detection Non-detection Non-detection - Non-detection Non-detection Non-detection cam tape'' 91,9- - Gloves (cotton blend)' 91,7 98.5 - Machine oil
94.0- -Grease 90
,4 97.2 -Filter aid (KC floc)' 98.7 99.4 -
Cation exchange resin (PCH) 97.1 99.2 - Anion exchange resin (PAO) 85.0 96.5 -1
Non-detection --- One Non-detection Non-detection Non-detection

Claims (1)

[Claims] 1. A waste mixture of flammable hybrid solids containing radioactive waste is put into an aqueous solution in which metal ions are dissolved, and the mixture is heated to a temperature within the range of 100 to 300°C. It is heated, pressurized, and oxygen-containing gas is introduced to bring the oxygen partial pressure to 3 to 30.
kG! /cnf range, the waste 1 is oxidized and decomposed, and then the waste to be decomposed and digested is additionally replenished and the oxidative decomposition operation is repeated. After 1=, the additional replenishment of the new waste is stopped. A radioactive waste treatment method characterized by allowing oxidative decomposition to progress and, after complete oxidative decomposition of organic matter, remaining salt aqueous solution to be concentrated. 2. The metal ions dissolved in the aqueous solution are
CLL", Ctr", Fe", Fe', Pd
", Ce", Nu", Cr", Mn",
2. The method according to claim 1, wherein the metal ion is present in a concentration range of 1 to 200 ppm as a metal ion. 3. The method according to claim 1 or 2, wherein a substance that neutralizes the acid is added to the extent that the state of the reaction solution after oxidative decomposition does not exceed 8. 4. The method according to claim 1 or 2, wherein the combustible miscellaneous solid waste is crushed or pulverized into pieces of 20 mm or less and treated in the aqueous solution.