JPS6186692A - Method of solidifying spent radioactive ion exchange resin - 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] [Field of Application of the Invention] The present invention relates to a method for solidifying spent radioactive ion exchange resin generated from nuclear power plants, etc., and is particularly suitable when an aqueous sodium silicate solution is used as a solidifying agent. The present invention relates to a method for solidifying used radioactive ion exchange resin.

[Background of the invention]

Land storage and land disposal are one form of final treatment and disposal of radioactive waste generated from nuclear power plants, etc., and for this purpose it is necessary to solidify the radioactive waste to create solidified radioactive waste. There is.

Conventionally, cement has been used as a solidifying filler for solidifying radioactive waste, but recently an aqueous alkali silicate solution has been developed as an alternative solidifying filler (Japanese Unexamined Patent Publication No. 197500/1983).

A solidifying material made of a mixture of the developed aqueous alkali silicate solution as a filler, an inorganic phosphate compound (PzOs SiOz) as a hardening agent, and cement as a water absorbing agent is used. When using these alkali silicates, inorganic phosphate compounds, and cement as solidifying materials, strength,
For the purpose of improving heat resistance and durability and preventing salt precipitation from the solidified body, the proportion of the curing agent is 3% by weight or more and 50% by weight.
In the following, a method is considered in which the proportion of the water-absorbing agent is 3% by weight or more and 35% by weight or less. However, even if a solidifying material such as the one described above is used, when solidifying a used radioactive ion exchange resin, non-uniform solidification occurs, which is not suitable for cine. In addition, when used radioactive ion exchange resin is solidified using the solidifying material in the above example, the standard value of the unconfined compressive strength of the solidified material when dumped into the ocean, which is the most stringent standard, is 1.
In order to secure 50 Kg/crd, only 10 I (7/dram or less) of used radioactive ion exchange resin can be filled. Therefore, the small volume reduction ratio has become a problem.

On the other hand, one of the methods that has been researched in the past is a method of solidifying debris with plastic, but when used for solidifying waste radioactive ion exchange (sealing), cement solidification or cement/alkali silicate aqueous solution solidification It was disadvantageous in that the cost was 50 times higher than that of solidification using.

No matter which method is used, it has not been possible to solidify a used radioactive ion exchange resin in large quantities and at low cost.

[Object of the Invention] An object of the present invention is to provide a method for producing a uniform solidified body with a high filling rate by using a cement/alkali silicate aqueous solution as a solidifying agent for a used radioactive ion exchange resin.

[Summary of the invention]

The used radioactive ion exchange resin to be solidified has sulfonic acid groups (as cation exchange groups) in the resin.
It has R5(hH). Ion exchange ability is theoretically determined by the hydrogen atoms of all sulfonic acid groups being cations (e.g. N
It is lost when it is replaced by a+ or ni+, etc.). However, under actual usage conditions, it is not completely used up and is stored in an on-site storage tank as a used radioactive ion exchange resin. On the other hand, the aqueous alkali silicate solution used as a solidifying agent is solidified according to the following reaction formula.

N a2Q (s iOz )ll+H20d 2N
aOH+ n S i (h...(1) where acid (
In the presence of protonic acid), the following reaction occurs and solidification occurs rapidly.

The pH of used radioactive ion exchange resin actually stored in tanks is around 3, and there are a considerable number of sulfonic acid groups (R-8
03kTJ remains. If the solidification treatment is continued as it is, the reaction (2) above will occur, and rapid hardening will proceed in the vicinity of the used radioactive ion exchange resin. As a result, a non-uniform solidified body is produced. Therefore, we considered suppressing the generation of H+ as a protonic acid by replacing the hydrogen atoms of the remaining sulfonic acid groups with cations in advance.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be explained below with reference to FIG. Spent radioactive ion exchange resin coming out of a nuclear facility is introduced into a resin slurry tank 3 through route 1. 2 NaO
An NaOH aqueous solution is introduced into the resin slurry tank from the H aqueous solution tank to neutralize the sulfonic acid groups of the used radioactive ion exchange resin.

Next, it is introduced into the dryer 4 and dried. N coming out of the dryer
The used radioactive ion exchange resin substituted by 22 is N
The pH is around 4 due to incomplete substitution with a* and the release of sulfonic acid groups in the dryer. If it is filled in the cement/alkali silicate aqueous solution solidifying material as it is, H9 will act as a protonic acid, causing rapid hardening only in the vicinity of the used radioactive ion exchange resin, which will prevent uniform solidification.

On the other hand, adjust the solidifying material as follows. A predetermined amount of mixer (
Then, the solidifying agent is introduced from the solidifying agent tank 5 into the mixer 7. In the mixer 7, the solidified weight after solidification is used as a standard.
Adjust the amount of aqueous solution. After the used radioactive ion exchange resin and the solidifying material are uniformly mixed in the mixer 7, they are transferred to a 200-ton waste storage drum for solidification and curing.

In addition, in these series of steps, it is possible to obtain a solidified product having the same strength even if either the mixer 3 or the dryer 4 is omitted.

Next, we will discuss the experimental data that supported the present invention in the second section.
This will be explained based on FIGS.

Figure 2 shows the unconfined compressive strength of 150 required for ocean dumping.
K9/: When using the ttif standard, the uniaxial compressive strength ( Kg/Cd), and the horizontal axis shows the amount of waste resin powder (
200,/, conversion, K9) and 9 is a graph of the obtained experimental results. When solidified with cement alone, only used radioactive ion exchange resins less than 1019 can be processed. When using Portland cement and silicate water glass, the throughput can be increased to 40 kg. Furthermore, by using the solidifying agent of the present invention in which an alkali of 1 to 5 by weight is added to Portland cement and silicate water glass, it becomes possible to treat the radioactive ion exchange resin used up to 9 to 85. A significant increase in processing power is obtained. 15, which is the standard value for unconfined compressive strength for ocean dumping.
0 to 9/C111 with a margin of 20 candy, 180 K
When the standard value of y/d is increased, the effect of the present invention becomes even greater, and the processing capacity of used radioactive ion exchange resin is approximately 4 times that of solidification using Portland cement and silicate water glass, which has been considered optimal until now. have.

FIG. 3 shows the results of an experiment in which the amount of alkali added in the present invention was determined to be 1 weight or more and 5 weight or less. The vertical axis shows the unconfined compressive strength (Kr/i), the horizontal axis shows the alkali (any alkali aqueous solution containing monovalent cations is fine), the addition weight ratio (wt%) f, [the experimental results obtained] It is expressed in a graph. The strength of the solidified material increases as the curing period increases, but when 1 weight of alkali is
The solidified material obtained by curing with the addition of 100% or less and 5% or less of IJ fully satisfies the unconfined compressive strength standard value of 150 Ky/crd when dumped at sea.

〔Effect of the invention〕

According to the present invention, it is possible to create a uniform solidified body of a used radioactive ion exchange resin with a high filling rate using cement/alkali silicate aqueous solution as a solidifying agent.

[Brief explanation of drawings]

Figure 1 is a diagram showing one example of solidifying a used radioactive ion exchange resin using the present invention, and Figure 2 shows data from experiments that formed the background of the present invention on the vertical axis. Unconfined compressive strength (Kp/crtl) The horizontal axis represents the filled amount of used radioactive ion exchange resin.
y/crIi) is an organized diagram showing the amount of alkali added (wt%) on the horizontal axis. 1... Inflow route of spent radioactive ion exchange resin discharged from nuclear facilities, 2... Alka+) (N aOH
) Aqueous solution tank, 3... Used radioactive ion exchange resin slurry tank, 4... Dryer, 5... Solidifying agent tank, 6... Cement tank, 7... Mixer (tank tank) , 8...zoot drum for radioactive waste, 9
...Graph for solidifying with cement alone, 10...
・Graph when solidifying using cement and aqueous alkali silicate solution, 11... Graph when solidifying by adding 1% by weight or more and 5% by weight or less of alkali to cement and aqueous alkali silicate solution, 12・...Standard values for ocean dumping, 13...Experimental data after curing for 18 days or more, 14.
...Experimental data after 3 days of curing.

Claims (1)

[Claims] 1. In a method of solidifying a used radioactive ion exchange resin, after treating the used radioactive ion exchange resin with an alkaline solution, an excess alkali aqueous solution, cement, and an alkali silicate aqueous solution are used as a solidifying agent. A method for solidifying a used radioactive ion exchange resin, characterized by solidifying it. 2. The method for solidifying a used radioactive ion exchange resin according to claim 1, wherein the content of alkali in the solidifying material is 1% by weight or more and 5% by weight or less. 3. In the solidification method, the used radioactive ion exchange resin is not treated with an alkaline solution, but is solidified using an excess alkaline aqueous solution, cement, and an alkali silicate aqueous solution as solidifying agents. A method for solidifying a used radioactive ion exchange resin according to item 1.