JPS60187899A - Method of treating radioactive cesium waste liquor - 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 solidifying a radioactive wastewater solution containing cesium as the main metallic element and converting it into a relatively insoluble and thermally stable form. In particular, the present invention relates to a method for treating radioactive cesium waste liquid by converting cesium, a radioactive isotope, in the radioactive waste liquid into the form of stable solid polyusite.

Radioactive cesium, mainly 137QB, is the main hazardous component in the radioactive effluent from the nuclear power plant Zorant.

This component, 0137Q3, is a troublesome substance because it not only has a long half-life, but also is radioactive and has high solubility because it is an alkali metal. Therefore, it is necessary to store it in isolation for a long period of time. In order to safely preserve it in a way that does not harm biological systems, it is easier to convert 137QB in the waste liquid into a solid state. Furthermore, it is not necessary to be in a mere solid state, but to be an insoluble, low-reactivity, and thermally stable compound or mineral. As such a mineral, polyusite according to the present invention has a diameter of 1m7Q.
B can be mentioned as a substance that can be immobilized in its skeleton.

? Leucite is also naturally occurring as a cesium tectosilicate mineral (for example, in Japan, it occurs in the crevices of granite and pegmatite together with petalite, as in Nagashige, Fukuoka, Fukuoka Prefecture), and Os1. (AlK, Si3
It is a quasi-feldspathic mineral whose unit cell is represented by the composition formula of ``Snow 096'', and has physical properties of 6.5 katata and a density of 2-9 t/Cm'', and is a high-density mineral that does not have any ferrite-like micropores. Volusite is a substance that has thermally and chemically stable properties. Volusite can also be synthesized. For example, R, M
, BazTer et al. J, ChemSoc, Dalt.
on (1972) 2534, reported the formation of polynysite by maintaining an aqueous solution of metakaolinite and cesium hydroxide at 80°C.

The present invention focuses on the properties of cesium, and focuses on the properties of cesium, including volusite,
After intensive research on the conditions for synthesizing other minerals, we discovered that this method can be applied to the treatment of radioactive waste solutions.

Cesium-based aluminosilicate minerals such as volusite are produced as inorganic polymers by dehydration condensation from a solution containing water, silica, alumina, and cesium sources or cation sources such as other alkali metals according to the following formula. be synthesized.

A1203- a SiO,-b H,O+2 (1-
x) C? + 2XM++ 20H-+ (Os Mx
), O-All0. - aSiO, -(IX)' cH20+ (1+b-c) H-total 0 Here, M+ refers to an alkali cation including sodium and/or an organic cation, singly or in a mixture.

In addition to polynysite, cesium-based aluminosilicates include endigonite-type zeolite (Os, O-Al, 03-28iO, ・2.4HzO
) 0s-F as its high temperature (1060°C or higher) fired product
(Os, O-Al, O,, SiO,) kampf') f
b) ([), 40s, O-1,1Na! O-Al, O
, -48iO, -xH2O), nepheline as its high-temperature (560°C or higher) calcined product, and zeolite synthesized using a choline compound called ZSM-45 are known. (R,M.

Barrer et al. J, Chem Soc, A (19
68) 2475.

R, M, Barrer I, J, Chem Soc;
(1953) 4029.

R, M, Barrer et al. J, Chem Soc, (
1952) 1561.

JP-A-54-68800) In cholera, C5-D, ZSM-43, etc. are microporous as zeolites, and the main skeleton is loosely formed of silica and alumina, so the existence form of Os is unstable. It is not suitable for the purpose of cinema because it tends to be forced and exchanged. However, C5-F still has a surface layer in that it cannot be formed unless a higher temperature than necessary is used for its formation. In systems coexisting with IJium, Cs can be contained in the structure, but in structures where C8 is insolubilized (generally considered to be the sodalite structure). ) is not very crowded.

Therefore, since it is easily washed out, it cannot be used as a substance for this purpose. In addition, the calcined product of nepheline is different from polynysite in that Os is insolubilized, but its weight is
The s content is small and is not effective in storage, storage, and isolation. In addition, 0s-D reacts with a silica source under hydrothermal conditions and is converted to polynysite, but in the present invention, 0s-D
-D is not necessarily required. In this way, polynysite is a suitable compound for the present invention as a form that insolubilizes Os, and since it can be easily formed from an aluminosilicate gel and a cesium-containing solution, it is the starting point for the present invention. Opened up.

As a result of researching the synthesis conditions of polynysite, the present inventors found that polynysite mineral was produced by including an onium compound in a mixture containing radioactive waste liquid, water, silica, alumina, and an alkali metal source. They have discovered that it is possible to make the conditions mild and short, and have completed the present invention. It is well known that onium compounds are effective in forming special zeolites in zeolite synthesis, but it is difficult to predict that they would have the same effect in polynysite synthesis. Since it is an organic substance, it also has the advantage of being a cation source that can be easily removed by firing, which is also a feature of the present invention.

Onium compounds are compounds that contain elements with lone pairs of electrons, such as oxygen, sulfur, and nitrogen, and are formed by the coordination of protons or other cationic reagents with these lone pairs. For example, R,N 1-R'X→[R8N+R/]X- (where R,N is amine, R'X is halogenated alkyl, (R
3N''R/]X- is an alkyl ammonium arsenide.

In addition to nitrogen, various elements become cationic to form various onium compounds, and in addition to ammonium compounds, phosphonium compounds, oxinium compounds, oxinium compounds, etc. are representative examples. It is widely known that onium compounds are effective substances for zeolite synthesis. For example, for the synthesis of ZSM-5 zeolite,
Tetracylobylammonium bromide is effective for the synthesis of TMA-offretite, and tetramethylammonium hydroxide is effective for the synthesis of TMA-offretite.

As onium compounds that are effective in the present invention, nitrogen compounds, of which tetramethylammonium salt is a representative example, are the most readily available and easy to handle, but other onium compounds may also be used for the purposes of the present invention. , does not exclude its use. Furthermore, when using an alkylammonium salt as a nitrogen-based onium compound, the shorter the carbon chain length of the alkyl group, the more effective it is for the purpose of the present invention. A representative example of this is tetramethylammonium salt. This compound may be introduced into the system as an onium compound, or may be generated and used in the system from trimethylamine and a methyl compound according to the above reaction formula.

Ammonium salts such as ammonium hydroxide and ammonium chloride can also be mentioned as onium compounds of the present invention.

Onium compounds can be used in the form of various salts such as halides and hydroxides. Moreover, the pH of the mixture must be
Since it is necessary to maintain and adjust the pH to be basic, preferably at pH 9 or higher, it is also used in a basic form, for example in the form of a hydroxide, in order to serve as a pH regulator.

The water in the mixture containing water, silica, alumina, and an alkali metal source (hereinafter referred to as the raw material mixture) of the present invention also serves as the water in the radioactive waste solution, but the water must be hydrated in advance to meet the purpose of the present invention. It is necessary to adjust it by operations such as volume reduction. The amount of water contained in the raw material mixture is generally 5 to 50% relative to the amount of alkaline cations, mainly Os, present in the system.
250 equivalents are effective. As the silica in the raw material mixture, known silica source materials commonly used in zeolite synthesis, such as sodium silicate, colloidal silica dispersion, silicic acid, and quaternary ammonium silicate, can be used. The amount of silica in the raw material mixture must be a necessary and sufficient amount to form polynysite with respect to the total amount of Os+ to Os and cations;
It is preferable to select from a range of 2 to 4 moles. As the alumina in the raw material mixture, known alumina source materials used in zeolite synthesis, such as sodium aluminate, aluminum sulfate, aluminum nitrate, and aluminum chloride, can be used. The amount of alumina in the raw material mixture is O
The amount needs to be necessary and sufficient to form polynysite based on the total amount of 8 to Os and cations, and the amount is preferably selected from the range of 1 to 2 moles based on Os. It is also possible to provide silica and alumina sources by clay minerals based on silica and alumina to be effective in zeolite synthesis. Clay minerals that can form silica and alumina in the raw material mixture include kaolinite minerals such as kaolinite,
Examples include (tontonite) and irophyllite.

The alkali metal source contained in the raw material mixture can include not only Os from the radioactive waste solution but also other sources such as Na. In fact, it can also contain alkaline earth metals such as Sr. In any case, the pH of the mixture must be in the basic range of 7 or more, especially 9 or more, and OH
/Sin, the ratio is adjusted to be 1 or less, preferably 0.5 or less.

When calculating the OH/5in2 ratio, for example, Os OH, tetraammonium hydroxide (if the onium compound is in this form), silicate IJum (NaOH
-1-S 1o2) or aluminic acid),
+) A (Calculated by summing the number of moles of OH- added as NaOH-1-A140 to calculate hydroxide, and subtracting the number of moles of acid added from the total value. In this case, the acid is simply HC, HNO3, H2S
It is sometimes added as O4, etc., or as aluminum sulfate (AlzOs+HzSO4), aluminum chloride (Alz03 + HCl2), aluminum nitrate (A1203-1-HNO3), etc.

The amount of onium compound added to the raw material mixture needs to be an effective amount for converting the raw material mixture into polynysite, but in general, 0.05 to 1 mol based on Os is effective. A plan.

The raw material mixture is heated for about 5 minutes until the polynysite mineral is formed.
Obtained at 0°C to 200°C for about 6 hours to about 300 days. A more preferable temperature range is 80°C to 180°C, and the retention time in this temperature range is about 6 hours to about 15 days, but treating radioactive waste in a pressurized container poses safety problems. In this invention, it is particularly preferable to carry out the process at normal pressure, that is, below 100°C, because it is easy to use.It goes without saying that the shortest treatment time is around 100°C, and the time in this case will vary depending on the composition of the raw material mixture, etc. It depends, but polny sites usually form in about 1 day to 1 week.

The temperature of the raw material mixture is maintained until a sufficient amount of polynysite is generated. The solid product mainly composed of borinisite is separated from the aqueous solution by methods such as filtration and sedimentation. In this way, C contained in the raw material mixture
Most of the s is immobilized in the polny site.

The present invention will be further illustrated by the following examples.

Incidentally, radioactive cesium waste liquid from seedlings is dangerous and difficult to obtain, so an aqueous solution of cesium hydroxide was used as a substitute for such waste liquid. In this respect, although the following examples cannot be said to be true examples, the effects of the present invention can be fully understood.

Example 1 By condensing a 1% solution of cesium hydroxide, 28
．． 7% aqueous solution 420.8 r and silica sol (Snowtex 3011 manufactured by Sankagaku Co., Ltd.) 500? and aluminum chloride aqueous solution (AIC; 13: 93.4 y, H2O
: 100F) was added, and 102v of a 10% water bath solution of tetramethylammonium hydroxide was further added and stirred thoroughly.

This mixture was sealed in an autoclave and kept at 1(1)°C for 3 days to reduce the production of grain-leucite.
Confirmed by line diffraction.

By holding the mixture for an additional 6 days, good crystals of polynysite were obtained.

Comparative example 1

Claims (1)

[Claims] A radioactive waste liquid containing cesium as the main metal element is made into a mixture containing water, silica, alumina and an alkali metal source,
A method for treating a radioactive cesium waste solution, which comprises reacting until a poleusite mineral is produced, wherein the mixture further contains an onium compound.