JPS60219598A - Method and device for removing chlorine ion in radioactive 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 [Technical Field of the Invention] The present invention relates to a method and apparatus for removing chloride ions from radioactive waste liquid produced, for example, in a nuclear power plant.

[Technical background of the invention and its problems] In nuclear power plants, seawater is used as secondary cooling water, but if this seawater leaks and flows into the nuclear coupler, it will be discharged from the plant. Since the radioactive waste liquid contains corrosive jIA elementary ions, there is a problem in that such waste liquid cannot be treated with an evaporative concentrator.

For this reason, conventionally, such radioactive waste liquid has been either discharged as it is after removing the radionuclides, or passed through an ion exchange resin tower and then evaporated and concentrated, while solidifying the unused ion exchange resin. It is being processed and disposed of.

However, the former method has the problem that it is difficult to completely remove various radionuclides because evaporation and concentration cannot be performed, and the latter method has the problem of increasing the amount of waste resin generated. there were.

In order to solve this problem, the present inventors previously proposed a method for removing chlorine ions in radioactive waste liquid by adsorbing them to a bismuth compound (Japanese Patent Application Laid-Open No. 161894/1983).
In this method, insoluble solids such as crud (mainly Fe 203 ) and N in seawater are removed from the radioactive waste liquid.
There was a problem in that the presence of sodium ions derived from a(l) significantly reduced the removal efficiency of chlorine ions.

In addition, with the conventional method of simply adding bismuth compounds into radioactive waste liquid containing chlorine ions and adsorbing chlorine ions by stirring and mixing, the adsorption efficiency of chlorine ions is low in the neutral or alkaline region. In order to fully demonstrate the adsorption effect, the radioactive waste liquid must be kept at a pH of 2.
The problem was that the entire apparatus, including the waste liquid storage tank for storing radioactive waste liquid and piping, had to be made of N14 edible material.

Furthermore, as the bismuth compound reacts with chlorine ions to produce bismuth oxychloride (Bi0CJ2), the resistance to liquid passage increases significantly, and in some cases, the liquid passage rate immediately before treatment may be 1/2 of the initial liquid passage rate. The problem was that it was reduced to /15.

OBJECT OF THE INVENTION] The present invention has been made to address these conventional difficulties, and it is not affected by cladding or sodium ions that interfere with the adsorption of chlorine ions, is efficient, and does not significantly increase liquid flow resistance. The object of the present invention is to provide a method for removing chlorine ions from radioactive waste liquid without causing any damage, and an apparatus for use in this method.

[Summary of the Invention] That is, the method for removing chlorine ions from radioactive waste liquid of the present invention involves treating a bismuth compound supported on a particulate carrier with sulfuric acid, and then passing a radioactive waste liquid containing chloride ions through this mixture. The equipment used in this method includes a waste liquid storage tank that contains radioactive waste liquid containing chlorine ions, a column of bismuth compounds supported on a particulate carrier, and a sulfuric acid tank that contains sulfuric acid that is passed through this column. It is characterized by comprising a storage tank and a treated water storage tank that stores the radioactive waste liquid that has passed through the column.

Examples of the bismuth compound used in the present invention include bismuth acid (1-IBi 03 > or a salt thereof, bismuth oxide (Bi 203·n H20 (n≧0)), among which hydroxylated bismuth Bismuth (B!
(OH) 3) is suitable.

Bismuth hydroxide is produced by, for example, mixing bismuth nitrate and mannitrate, dissolving it in water, and adding 20% NaOH
It is prepared by diluting by pouring into an aqueous solution, neutralizing by adding 4 normal (N) sulfuric acid, cooling, aging for 24 hours, and washing the precipitate.

This bismuth hydroxide is used as it is supported on a particulate carrier without performing operations such as air drying, pulverization, and classification.

Zeolite is suitable as a fine particulate substance on which a bismuth compound is supported. In order to support a bismuth compound on zeolite, for example, the zeolite carrier and the bismuth compound may be stirred and mixed in water. By this operation, a bismuth compound such as bismuth hydroxide is adsorbed on the surface of zeolite, which has excellent adsorption properties and a large specific surface area.

A column for adsorbing chloride ions is prepared by filling the column with the bismuth compound supported on the particulate carrier thus obtained.

[Embodiment of the Invention] The details of the present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 1 is a block diagram schematically showing the configuration of a chlorine ion removal apparatus according to an embodiment of the present invention.

This chlorine ion removal device consists of a waste liquid storage tank 1 that temporarily stores chlorine-containing waste liquid such as leaked seawater, demineralizer recycled waste liquid that has been treated with seawater, or floor drain waste liquid; A bismuth hydroxide preparation tank 2 for preparing bismuth hydroxide, a zeolite mixing tank 3 for mixing and supporting the slurry bismuth hydroxide sent from the bismuth hydroxide preparation tank 2 with zeolite, and a zeolite mixing tank 3 for transporting bismuth hydroxide from the zeolite mixing tank 3. A sulfuric acid storage tank 5 supplies sulfuric acid to the columns 4a and 4b, and the treated water treated in the column 4a or 4b is temporarily stored until the next treatment is carried out. It consists of a treated water storage tank 6.

Next, a method for removing chlorine ions using the apparatus of the above-described embodiment will be explained.

First, bismuth hydroxide supported on zeolite is supplied as a bed to the columns 4a and 4b, and then 0.1 to 5 N sulfuric acid is passed through the bed to treat the bismuth hydroxide. Mixed bed 4a,
In 4b the following reaction is carried out.

Bi (OH)3+ @” −+ Bi (OH)2”
+ t12 0 ... ... 0 Next, the chlorine-containing ion waste liquid 7 stored in the waste liquid storage tank 1 is passed through one of the bismuth hydroxide columns 4a or 4b at an appropriate water flow rate. . In addition, columns 4a and 4b
are used alternately.

Here, the crud in the radioactive waste liquid is adsorbed and removed by the zeolite, and at the same time, the chlorine ions in the radioactive waste liquid are removed by the zeolite-supported chlorine ions (Bi (OH)2 ÷
At this time, bismuth hydroxide (Bi (OH)2'') reacts with chlorine to form bismuth oxychloride (Bi QCβ), but it is removed in the form of fine particles. Since the zeolite ensures voids for water to flow, the water flow resistance does not increase much.

It is also known that sodium ions in the radioactive waste liquid interfere with the adsorption of chlorine ions by bismuth hydroxide, and this is because they interfere with the production of 81(OH)2+ in the reaction (2).

If Bi (OH>3→Bi (OH)20 and C are set in advance by sulfuric acid treatment,
B! (OH)2+ reacts with chlorine ions without being hindered by sodium ions to form B10C.

This is why a cation exchange resin is not required, and the method of the present invention does not require that the sodium ions be treated in any particular way.

Next, the treated water that has passed through the column 4a or 4b is accommodated and stored in the treated water storage tank 6.

Therefore, according to this device, the crud in the radioactive waste liquid is removed by the zeolite, and the sulfuric acid treatment eliminates the interfering effect of sodium ions. Under these conditions, chlorine ions come into contact with bismuth hydroxide, causing secondary
As shown in the figure and FIG. 3, the chloride ion adsorption effect on bismuth hydroxide is improved, and the chloride ion removal efficiency is greatly improved.

That is, Figure 2 shows that bismuth hydroxide is immersed in a plurality of simulated waste solutions in which different amounts of cladding (Fe203) are added to a p)-17 solution containing 2000 ppm of chloride ions at 25°C for 24 hours to remove chloride ions. It is a graph showing the results of measuring the amount of adsorption. As is clear from the results in FIG. 2, it can be seen that as the amount of crud in the liquid to be treated decreases, the adsorption of chlorine ions rapidly increases.

Figure 3 also shows a simulated waste solution (curve A) at pH 2 containing NaCJ2 of 23001)I) and a bismuth hydroxide column treated with 0.5MA constant sulfuric acid.
Simulated waste liquid at pH 7 containing lm of chloride ions (curve B
) to a column packed with bismuth hydroxide.
Processing liquid ω (m
The figure shows the results of measuring the column outlet chlorine concentration (μg/l1lJ2) for A10-Bi (OH) 3 ). It is clear from the graph of FIG. 3 that even if sodium ions are present in the liquid to be treated, the chloride ion adsorption effect of bismuth hydroxide is considerably improved.

In this example, the sulfuric acid treatment causes the reaction of equation 0 to proceed and τB! Since (OH)2÷ is generated, even if the solution is passed through the solution without adjusting the pH, the reaction according to the following equation proceeds smoothly and the amount of chlorine ions adsorbed by bismuth hydroxide increases.

Bi (OH)2 ” + Gλ−→ B! <0f−1)2+・Cλ−・・・・・・■B!
(OH)2+・CJ2− → Bi QCa 10 HzO・・・・・・・・・■ Figure 5 also shows the case where the chlorine ion concentration is 230001111 at pi-17 shown by curve A in Figure 2. NaC! 2 is a graph showing the results of measuring the pH at the column outlet when a solution is passed through the apparatus of this example. From this graph, it can be seen that the column outlet is also neutral.

Therefore, in the apparatus of the present invention, a neutralization device is not necessary, but it goes without saying that a neutralization device may be provided in the treated water storage tank 6 in consideration of safety during the sulfuric acid treatment.

[Effects of the Invention] As is clear from the above description, according to the method and apparatus of the present invention, since the bismuth compound is used in a state supported on the zeolite surface, the specific surface area of the bismuth compound becomes large. It is possible to improve the adsorption performance of chlorine ions.

In addition, since the bismuth compound supported on the particulate carrier is a zeolite column, it has the effect of removing undissolved solids (crud) by zeolite etc. and not being interfered with by sodium ions. The adsorption effect of chloride ions by bismuth compounds has been significantly improved compared to conventional methods, and there is no abnormal increase in water flow resistance during treatment.
) There is an advantage that H adjustment is not necessary and chlorine ion treatment can be performed while remaining neutral.

Furthermore, since the pH of the waste liquid treated by this column remains near neutral, there is also the advantage that there is no need to provide special anti-corrosion measures to the equipment.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a graph showing changes in chloride ion adsorption when cladding is present, and Fig. 3 is a graph showing changes in chloride ion adsorption and release when cladding is present, and Fig. 3 is a graph showing the case where sodium ions are present and the case where sulfuric acid treatment has been performed A graph showing the change in outlet chlorine ion concentration with respect to the amount of treated liquid in a column filled with chloride hydroxide.
This is a graph showing. 1...... Waste liquid storage tank 2...
...Bismuth hydroxide preparation tank 3...
... Zeolite mixing tank 4a, 4b ... Zeolite column supporting bismuth hydroxide 6 ...... Treated water storage tank Patent attorney Sasa Suyama - No. Figure 1 Figure 2 Fe20Bt (pg/ml)

Claims (6)

[Claims] (1) A method for removing chlorine ions from a radioactive waste liquid, which comprises treating a bismuth compound supported on a particulate carrier with sulfuric acid, and then passing a radioactive waste liquid containing chloride ions through this mixture. (2) The method for removing chlorine ions from radioactive waste liquid according to claim 1, wherein the bismuth compound is bismuth hydroxide. (3) The method for removing chlorine ions from radioactive waste liquid according to claim 1 or 2, wherein the particulate carrier is zeolite. (4) A waste liquid storage tank containing a radioactive waste liquid containing chloride ions, a column of bismuth compound supported on a particulate carrier, and passing through this column. An apparatus for removing chlorine ions from radioactive waste liquid, comprising a treated water storage tank for storing radioactive waste liquid. (5) The apparatus for removing chlorine ions from radioactive waste liquid according to claim 4, wherein the bismuth compound is bismuth hydroxide. (6) The apparatus for removing chlorine ions from radioactive waste liquid according to claim 4 or 5, wherein the particulate carrier is zeolite.