JPS6023863B2 - Method for producing cesium selective separator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a selective cesium separator using ammonium phosphomolybdate, which can significantly improve separation performance.

In the treatment of liquid waste discharged from nuclear power plants, that is, liquid waste containing nuclides with various half-lives resulting from nuclear fission production, special consideration must be given to short half-lives, nuclides, and waste treatment. It is extremely desirable to be able to separate nuclides with long half-lives that require However, the conventional methods mainly used, such as the evaporation condensation method, simultaneously process nuclides with long and short half-lives, and therefore include cesium, which has a particularly long half-life, such as 134Cs and 137Cs. Therefore, when disposing of large quantities of waste containing long and short half-life nuclides, it is necessary to dispose of them with the same careful consideration as that required for long half-life nuclides. be. Therefore, there is a demand for the development of a method that can selectively separate cesium, which has a particularly long half-life, from a large amount of liquid waste. On the other hand, the above-mentioned nuclides and separated liquid are released into the environment, for example, into seawater, but they contain the nuclides that could not be separated.

For this reason, in order to evaluate the public's exposure dose, administrative guidance requires measurement and monitoring of the amount of radioactive cesium and radioactivity in seawater. However, the representative methods mainly used in the past, such as the Science and Technology Agency method,
Finely powdered ammonium phosphomolybdate and other reagents that have cesium selective and scavenging properties are added to the collected seawater, and after repeated filtration and filtration, the water is boiled to collect cesium by evaporation and coagulation. It is selective separation.
Therefore, not only does the separation process take a long time, but it also requires a high degree of skill in order to recover 100% of the cesium contained in the collected seawater. Therefore, this method lacks quickness and ease of measurement and cannot be said to be sufficient.
It is also clear that this method is suitable for separating and recovering cesium from small amounts of liquid, but is difficult to apply to separating cesium from large amounts of liquid, such as when measuring environmental radioactivity around nuclear power plants. . Therefore, for example, a method has been proposed in which a powder of ammonium phosphomolybdate, which is well known to selectively separate cesium, is supported on a carrier such as asbestos, and then seawater is passed through the carrier to selectively separate the ammonium phosphomolybdate. However, this is ammonium phosphomolybdate. Not only is it impossible to make a large column because it cannot reliably support the particles, but it also has drawbacks such as increasing the void volume within the column and reducing separation performance. The present invention provides a method for producing a cesium Z selective separator that can eliminate the above-mentioned drawbacks, and is characterized by the following points.

That is, in the present invention, a porous resin is used as a support for ammonium phosphomolybdate, and at the same time, this is impregnated with a scale molybdic acid solution and then treated with an ammonium nitrate solution. As a result, a precipitate (solid) of ammonium molybdate is formed so that it spreads well into the string holes in the resin, and when it expands, it pushes out the string holes against the elasticity of the resin. It is designed to generate a large supporting capacity for ammonium phosphomolybdate. As a result, the void volume is lowered to improve separation performance, and at the same time, columns of the required size can be easily manufactured, thereby eliminating the drawbacks of the conventional cesium selective separator using ammonium phosphomolybdate. It is characterized by:

In this way, selective separation of cesium can be easily and quickly carried out by passing liquid waste from a nuclear power plant.

Further, by passing a liquid to be separated, such as seawater containing cesium, and collecting the cesium separated into resin from the beach, it is possible to easily, quickly and accurately quantitatively measure radioactive cesium in seawater. Next, the manufacturing method and quantitative measurement examples of the present invention will be explained with reference to the drawings. FIG. 1 is a system diagram showing an example in which the present invention is applied to quantitative measurement of radioactive cesium in seawater. The present invention first involves (1) immersing a porous resin 1 made of a conventionally known resin such as epoxy, phenol, or polycarbonate into a tank 3 filled with a phosphomolybdic acid solution 2; Crush it well and let the liquid penetrate into the resin. Next, after removing the top liquid from tank 3, ammonium nitrate solution 4 is added and stirred to react well with phosphomolybdic acid solution 2 in resin 1. In the pores, a precipitate of ammonium phosphomolybdate is formed and trapped in the resin.
After that, ■ This resin 5 is washed by immersing it in a pot 7 filled with a hydrochloric acid solution 6 to remove the precipitate of ammonium molybdate scales formed on the entire surface of the resin 5, and to remove cesium during the measurement. A cesium selective separation resin is prepared by performing a well-known cleaning process to prevent the collected ammonium molybdate from flowing out and causing measurement errors. Next, (1) the prepared resin 5 is packed into a column 7 having a liquid inlet and an outlet, and seawater 8 containing radioactive cesium is passed through this column to collect cesium in the resin 5. For example, sodium hydroxide 9 is passed through the resin 5 to dissolve cesium 10. Then, in exactly the same manner as before, 1. Measure the recovery rate, 2. Transfer to a Kumarinelli container, and 2. Measure the radioactivity to quantitatively measure the amount of radioactive cesium in the seawater. According to the present invention described above, the separation performance can be significantly improved, so that cesium can be recovered with a significantly high degree of separation simply by passing the liquid to be separated through the prepared resin and eluting with a sodium hydroxide solution.

Furthermore, by selecting the amount of resin used, it can be applied to the separation and removal of cesium from large amounts of liquid waste as well as from small amounts of liquid in quantitative measurements. Therefore, for example, if cesium is separated from liquid waste from a nuclear power plant by the method of the present invention and then the evaporative condensation method is applied, the waste obtained by evaporative condensation can be easily disposed of. Furthermore, if the present invention is applied to the quantitative measurement of cesium in seawater, cesium can be separated and recovered without the need for a long time and skilled operation techniques unlike the conventional method described above, making the measurement simple and quick. can be achieved. Next, the present invention will be explained with reference to examples. Example 1 To artificial seawater, that is, seawater that was artificially prepared to have the same salinity and pH as natural seawater, 1 to 30 m of cesium ions for carrier were added depending on the cesium ion concentration in the seawater. Afterwards, the solution was made into a hydrochloric acid solution of about 0.1N, and the ammonium phosphomolybdate concentration in the resin was made into a resin of 9/92 (Amberlite XAD manufactured by Rohm and Haas Co., Ltd. in the United States).
-7 resin was passed through.

As a result, as shown in Fig. 2, a flow capacity of 1.7 x 10-3 meg/' was obtained at a single carrier cesium concentration, demonstrating the effectiveness of the resin of the present invention. Furthermore, almost 100% of the cesium ions trapped in the resin could be recovered by passing IN sodium hydroxide in an amount twice the amount of the resin. In addition, as a result of examining the influence of flow velocity on throughflow capacity,
It was not observed in the range of SV30-120. In addition, the exchange capacity increased as the concentration of ammonium dextrose molybdate increased. Note that the concentration of ammonium phosphomolybdate in the above resin is 92 9/I resin, and the concentration of ammonium phosphomolybdate on the porous resin 30 is 5 to 20.
After soaking in a 10' solution of polyphosphorous molybdic acid, adding an ammonium nitrate solution of the same concentration, and finally washing with 0.1N hydrochloric acid, it was obtained by soaking in a 10' solution of polyphosphorous molybdic acid and nitric acid. Ammonium solution concentration (evening/10')
The relationship between the concentration of ammonium phosphomolybdate and the ammonium phosphomolybdate concentration (female/') is shown in Figure 3. Example 2 Natural seawater with a concentration of 60 to 80% was used, and cesium ions were added to it to make the carrier concentration 1.
00' resin was passed through SVIOO.

After that, cesium was dissolved in IN sodium hydroxide, and the recovery rate of the cesium was limited by atomic absorption spectroscopy, and as shown in Table 1, extremely good results of 93 to 102% were obtained. was completed. In addition, when we filled one Kumarinelli container and measured the radioactivity per second using a high-efficiency Y-ray measuring device, the results shown in Table 1 were obtained. Conventionally reported values, for example, 0.1 to 0.1 for 137Cs. The spots Ci/ showed more agreement.

Furthermore, when the present invention is applied to the determination of seawater cesium, 0.00% is required to fill the resin preparation column. It took a total of 3 hours, 2 hours to pass the liquid through the column, and 0.5 hours to elute. This is 1/10 of the time required for conventional quantitative determination, which is about 3 hours for the so-called Science and Technology Agency method, and is also 1/2 of the time required for the fastest method. In addition, in the present invention, only the liquid is passed through the column, and there is no need for several operations such as addition of each reagent, filtration, and boiling, as in conventional methods. Therefore, the measurement operation can be made much simpler and faster than the conventional method. In the above embodiments, the cesium concentration of the liquid to be separated was adjusted by adding cesium ions, but this adjustment is not required when the cesium concentration is equal to or higher than a predetermined value. Moreover, although the case where the preparation and separation of the resin are carried out continuously has been described above, the resin can also be prepared in advance and used as needed. As is clear from the above explanation, the present invention provides an excellent advantage of being able to easily and quickly separate and remove cesium in a liquid, and separate and recover it, which is extremely useful for quantitative measurement of radioactive cesium in the environment. It makes a contribution.

Brief explanation of the drawings Figure 1 is a systematic diagram showing the preparation process of the resin of the present invention, Figure 2 is a diagram showing the relationship between cesium ion concentration in seawater and flow capacity, and Figure 3 is a diagram showing the relationship between cesium ion concentration and flow capacity in seawater. , is a relationship diagram between the ammonium nitrate solution (Y/10) and the molybdenum concentration in the resin (Imitation/'s resin).

Figure 1 younger brother 2 Figure 5

Claims (1)

[Claims] 1 Cesium selection characterized by adding an ammonium nitrate solution to a porous resin having no exchange group impregnated with a phosphomolybdic acid solution to form a precipitate of ammonium phosphomolybdate in the pores of the resin. Method for producing a separator.