JPS6341520B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for heating and reducing the volume of used ion exchange resins generated in nuclear power facilities, and the alkali metals present in the resin are removed in advance by thermal decomposition or oxidative combustion of the ion exchange resin before the heat treatment process. This enables efficient post-processing. Currently, used ion exchange resin generated from nuclear power generation facilities continues to accumulate and remains unprocessed and simply stored. Conventionally, there are cement solidification methods and asphalt solidification methods as these treatment methods, but the current situation is that they are hardly ever actually implemented because the volume reduction effect is small. The method with the greatest volume reduction effect is incineration, but since ion exchange resins are flame retardant, incineration requires advanced technology. In particular, since it contains radioactive materials, sufficient care must be taken to prevent the heated material and residue from being scattered by the combustion air. The present inventor has focused on incineration treatment, which has a large volume reduction effect on ion exchange resins, and has made it easier to incinerate ion exchange resins, which are difficult to burn, by using microwaves that do not require fuel as a heating source. This was discovered after repeated research into pre-treating used ion exchange resin before incineration in order to further increase its incineration efficiency. When microwaves are used as a heating source, the amount of combustion air is much smaller than when fuel is used, so it is possible to minimize the scattering of objects to be heated and incineration residue. Various ions and impurities are adsorbed in used ion exchange resin. If an alkali metal (for example, sodium or potassium) is present, it will melt when heated because it has a low melting point, and this will cover the ion exchange resin, cutting off the supply of oxygen from the outside and preventing combustion. This not only slows down the combustion rate, but also causes the combustion material to become lumpy, which has a significant negative impact on incineration. Used ion-exchange resins usually do not contain large amounts of alkali metals, but if seawater leaks due to trouble in the main condenser, the seawater is removed using a condensate desalination device. In such a case, a used ion exchange resin containing a large amount of alkali metal, which is the object of the present invention, is produced. In this case, the alkali metal to be removed is mainly sodium. The method for removing alkali metals is to pass an acid solution (sulfuric acid, hydrochloric acid, nitric acid, etc.) through the resin and perform removal based on an ion exchange reaction. The object of the present invention is to remove in advance the alkali metals that have the above-mentioned adverse effects when incinerating ion exchange resins, so that the incineration can be carried out smoothly. Used ion exchange resin is usually stored in a mixed state of cation exchange resin (cation resin) and anion exchange resin (anion resin), but since it is the cation resin that adsorbs alkali metals, The treatment may be performed on the cationic resin. However, for this purpose, it is not necessary to separate the used ion exchange resin into positive and negative ion exchange resins, and the acid solution may be passed through the resin in a mixed state. The most preferred method is to separate both ion exchange resins and pass the acid solution through only the cation exchange resin. This is because the ion exchange efficiency improves, and substantially less acid solution is required. This will be explained below based on FIG. The used ion exchange resin 2 in which the cationic resin and the anionic resin are mixed is transferred to the processing device 3. An acid solution, for example, a sulfuric acid solution is prepared as the processing agent 1 and supplied to the processing device 3. The amount of treatment agent 1 supplied is an amount sufficient to remove alkali metals from the used ion exchange resin 2 to 50% or less, preferably 30% or less of the total ion exchange capacity of the cation resin. A rough estimate of the small amount of processing agent 1 required is estimated. The reaction in which alkali metal ions (M _A ⁺ ) are removed with acid (H ⁺ ) is carried out only with cationic resins, and is expressed as R·M _A +H ⁺ =R·H+M _A ⁺ . Table 1 shows the minimum amount of treatment agent required per 1 m ³ of used ion exchange resin.

[Table] In the trial calculation, it was assumed that the total ion exchange capacity of the cationic resin was 2 equivalents/-resin, and that the treatment agent was effective in removing 100% alkali metal ions. As shown in Table 1, if the used ion exchange resin does not contain cation resin,
or contains a cationic resin, and the total amount of alkali metal ions adsorbed thereon is 50% of the total ion exchange capacity of the cationic resin, preferably
If it is less than 30%, there is no need for pretreatment in the present invention. The treated used ion exchange resin is fed to a microwave incinerator after removing attached water using a drainer. When the cationic resin with alkali metal adsorbed is incinerated, the larger the amount of alkali metal is, the larger and harder the lumps become, and as the amount of the alkali metal is reduced, the size of the lumps decreases and becomes softer. Therefore, the smaller and softer the lumps are during microwave heating, the better the efficiency will be. If the alkali metal adsorbed on the ion exchange resin is 50% or less, preferably 30% or less of the total ion exchange capacity in the cation exchange resin, the efficiency of volume reduction by heating with microwaves will be improved. The mixing ratio of cation resin and anion resin in the used ion exchange resin can be determined by sampling it into a measuring cylinder before transferring it to the processing device 3.
The volume of each can be easily confirmed. However, the necessary amount of the treatment agent should be determined based on the amount of cationic resin. In the present invention, by removing the alkali metal which is a substance that prevents combustion of ion exchange resins, the combustion of ion exchange resins is not prevented and incineration becomes extremely easy. Furthermore, by using microwaves as a heating source, scattering of incinerated materials can be reduced as much as possible. Also, since it can be heated from the inside, it becomes easier to incinerate the flame-retardant resin.

[Brief explanation of the drawing]

FIG. 1 shows steps as an embodiment of the present invention. 1...Treatment agent, 2...Used ion exchange resin,
3... Processing device, 4... Draining device, 5... Microwave incinerator.

Claims (1)

[Claims] 1. When reducing the volume of spent ion exchange resin generated from nuclear facilities through thermal decomposition or oxidative combustion, alkali metals adsorbed on the spent ion exchange resin are removed as a pretreatment using an acid solution. A heating volume reduction method for an ion exchange resin containing a radioactive substance, characterized by: 2 The alkali metal adsorbed on the used ion exchange resin is equal to the total ion exchange capacity of the cation exchange resin.
The heat volume reduction method according to claim 1, characterized in that the volume is removed by using an acid solution to reduce the volume to 50% or less. 3. The heating volume reduction method according to claim 1, wherein microwaves are used as a heating source during thermal decomposition or oxidative combustion of the used ion exchange resin. 4. The heating volume reduction method according to claim 1, in which the alkali metal is removed by passing an acid solution through both the positive and negative ion exchange resins in a mixed state without separating them. 5. The heating volume reduction method according to claim 1, wherein the acid solution is any one of sulfuric acid, hydrochloric acid, and nitric acid.