JP2984428B2 - Waste liquid nuclide separation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating and recovering technetium and radioactive iodine contained in a radioactive liquid generated from a facility using radioisotopes and nuclear facilities, from other radionuclides, and an apparatus used therefor. It is about.

[0002]

2. Description of the Related Art In nuclear facilities using radioisotopes, it is necessary to clarify the concentration of radionuclides mixed in a generated liquid sample. For this reason, radioactivity of mixed nuclides is measured, but nuclides that emit only β rays and γ
When nuclides that emit rays are mixed, β-ray emitting nuclides are chemically separated, and after confirming that there is no influence of γ-rays on β-ray measurement, each is used for measurement. . Further, the waste liquid may contain the organic substance used in the test, and the radionuclide may be concealed, and the radionuclide to be chemically separated may not exhibit a predetermined chemical behavior. In such a case, at present, after the decomposition treatment of the organic substance, a chemical element separation operation (for example, a precipitation separation method, a solvent extraction method, an ion exchange method, etc.) is performed by a human. Furthermore, the chemical separation of technetium and radioactive iodine, even if performed by workers with advanced analytical techniques, requires a great deal of operation and time to completely remove other radionuclides. I have.

[0003]

Since the radiochemical element separation technique is carried out only by workers with special skills, a limited number of personnel are required to know the radionuclide concentration in the sample. And a huge amount of work time is required.

Accordingly, an object of the present invention is to provide a method for separating technetium and radioactive iodine which does not require a special chemical pretreatment and which can perform element separation processing having a high separation coefficient with other mixed nuclides. It is intended to provide a system capable of performing analysis work even for a person who does not have a special chemical separation technique.

[0005]

SUMMARY OF THE INVENTION According to the present invention, technetium and radioactive iodine are volatilized by chemical wet oxidation of technetium and radioactive iodine in an oxidizing high temperature state with respect to a liquid sample generated from a facility using a radioisotope and a nuclear facility. To provide a system having a function of separating from other non-volatile radioactive nuclides.

That is, the present invention provides a method for elucidating the radioactive concentration of technetium and radioactive iodine in a liquid sample generated from a nuclear-related facility. By volatilizing and recovering in a sulfuric acid environment, the conventional analyst saves a great deal of time and labor. In order to perform the above processing, the following functions are required: a. Heating function b. Temperature control function c. Oxidant injection function d. Collection function e. Control functions that activate the above functions

Accordingly, the present invention provides a method for separating radioactive iodine and technetium from a radioactive liquid containing cobalt 60, wherein the radioactive liquid is heated in a nitric acid environment to volatilize and separate the radioactive iodine. , And the radioactive liquid after removing the radioactive iodine to dryness, and then heating and boiling under a sulfuric acid acidic environment dissolved in sulfuric acid, technetium is volatilized and separated by a technetium separation step characterized by comprising The present invention relates to a method for separating radioactive iodine and technetium from a radioactive liquid containing cobalt 60.

Further, the present invention provides a reaction tank provided with a chemical injection tank and a volatilization port for taking out volatile components, heating means for controlling the temperature to a predetermined temperature, and a reaction tank temperature controller. A cooler for condensing volatile components taken out from the outlet, and an iodine recovery tank and a water recovery tank installed in a cooling water tank for collecting radioactive iodine and technetium condensed by the cooler. The present invention relates to an apparatus for separating radioactive iodine and technetium from a radioactive liquid containing cobalt 60.

[0009]

The separation apparatus of the present invention volatilizes by forming a chemical environment in which technetium and radioactive iodine are easily volatilized from radionuclides mixed in the sample, and efficiently separates and recovers from other radionuclides. Things.

[0010]

FIG. 1 shows an embodiment of the separation apparatus of the present invention. In the figure, a reaction vessel (1) is a glass vessel provided with a reaction vessel temperature controller (2) having an external heater and a heating means. The upper part is equipped with a volatilization port for volatilized gas and a chemical injection tank (3) for injecting a chemical for volatilizing a part of the radionuclide, a reaction tank (1) and a chemical injection tank.
(3) is separated by a Teflon valve (2).

The volatilization port at the top of the reaction tank (1) is connected to a cooler (4), where volatile components are condensed. Further, the cooler outlet is connected to a three-way cock (5), and two outlets of the three-way cock (5) are connected to an iodine recovery tank (6) and a water recovery tank (7).
It is connected to the. The iodine recovery tank (6) and the water recovery tank (7) are immersed in a cooling water tank (8) containing ice and pure water in order to increase the recovery efficiency of volatile components.

A washing water tank (10) for washing the inside of the cooler (4) is connected to an outlet of the reaction tank (1) and a line of the cooler (4) through a Teflon valve 4 (14). ing. A cooler is used to inject chemicals from the chemical injection tank (3) and the washing water tank (10).
(4) The cleaning tank for cleaning the inside is a Teflon valve 4
It is connected via (14). The injection of chemicals from the chemical injection tank (3) and the washing water tank (10) uses the air gas pressure that has passed through the air supply line (9) from the air gas cylinder (15). The medicine is injected into the chemical injection tank (3) by removing the sliding joint (12) at the top of the chemical injection tank by human operation.

(Preparation before starting) A sample to be analyzed is weighed, and a carrier solution necessary for elemental separation is added.
2) is removed, the valve 2 (13) is opened, and the sample is injected into the reaction tank (1). Close valve 2 (13) and slide joint (1
The oxidizing agent solution is put into the chemical injection tank (3) from 2). The sliding joint (12) is connected to the upper part of the chemical injection tank (3), and the air supply line (9) is connected. Prepare a cooling water tank (8), iodine recovery tank (6) (put an alkaline solution in the iodine recovery tank in advance)
And the water recovery tank (7) is connected to the three-way cock outlet (5) in a state of being immersed in the cooling water tank (8). The open / closed state of the valve at this time is as follows. Valve 1: Open Valve 2: Close Valve 3: Close Valve 4: Close

(Starting of the device) Valve 1 (11) is opened and valve 2 is opened.
(13) is slightly opened, and the oxidizing agent solution is added to the reaction tank (1).
Further, the valve 2 (13) is fully opened, and the entire amount of the oxidizing agent is added to the reaction tank by the air sent from the air supply line (9), and the inside of the reaction tank (1) is continuously ventilated. In this state the reaction tank
Start heating in (1). The reaction tank temperature is the temperature control point (17)
Is controlled to a predetermined liquid temperature by a reaction tank temperature controller (2). Radioactive iodine in the sample starts volatilization due to the addition of an oxidizing agent and a temperature effect, and the volatilized radioactive iodine is supplied from the upper part of the reaction tank (1) by a supplied cooler (4) through an iodine recovery tank ( 6) sent to the iodine recovery tank
Absorbed (dissolved) in the alkaline solution in (6). After a lapse of a predetermined time, connect the three-way cock (5) to the cooler outlet (4) and the water collecting tank.
Set in the direction connecting (7). The reaction tank (1) is heated until the water in the container evaporates, and the water and volatile components are cooled by the cooler (4).
And collected in the water recovery tank (9). When the liquid in the reaction tank (1) dries, the heating of the reaction tank (1) is stopped and the reaction tank (1) is cooled (preferably cooling is natural cooling). After the cooling of the reaction tank (1) is completed, the valve 1 (11) and the valve 2 (13) are closed, the sliding joint (12) is once removed, and sulfuric acid containing an oxidizing agent is removed from the sliding joint (12). Put in injection tank (2). Connect the sliding joint (12), open valve 1 (11), and open valve 2 (1
3) is slightly opened, and sulfuric acid containing an oxidizing agent is supplied into the reaction tank. The valve 2 (13) is fully opened to ventilate the inside of the reaction tank (1). The reaction tank (1) is heated again to maintain a liquid temperature of 150 ° C. or higher, thereby evaporating technetium and rhenium and collecting the technetium and rhenium in the water recovery tank (7). After a lapse of a predetermined time, the heating of the reaction tank (1) is stopped, and the reaction tank (1) is cooled. Valve 1 (11) and valve 2 (13) are closed, valve 3 (16) is open, valve 4 (14)
Is slightly opened, and the washing solution previously added to the washing water tank (10) is poured into the cooler (4). After the injection is completed, valve 3 (1
6) is opened and the valve 4 (14) is closed. Remove the iodine recovery tank (6) and the water recovery tank (7) from the cooling water tank (8).

Hereinafter, specific experimental operations will be described in detail. In 100 ml of a sodium borate solution containing 10,000 ppm of B (boron), radioactive iodine ( ¹²⁹ I), ⁹⁹ Tc and
370 Bq was added to each of ⁶⁰ Co, and I ⁻ , ReO ₄ ⁺ and Co ²⁺ were each added as a carrier solution so as to contain 10 mg. Using this as a sample to be analyzed, the sliding joint (12) was removed, and the valve 2 (13) was opened and injected into the reaction tank (1).

[0016] Close the valve 2 (13) and slide the joint
From (12), 20 ml of nitric acid solution (1 volume of JIS special grade nitric acid and 9 volumes of pure water) as an oxidizing agent solution is manually injected into the chemical injection tank. Slide joint (12) into chemical injection tank
(3) Connect to the top and connect the air supply line. Also,
Prepare a cooling water tank (8), and connect it to the outlet of a three-way cock (5) while immersed in the iodine recovery tank (6) (100 ml of 4N sodium hydroxide solution in advance in the recovery tank) and the cooling water tank . The open / closed state of the valve at this time is as follows: valve 1 = open, valve 2 = closed, valve 3 =
Closed, valve 4 = closed.

Next, the valve 1 (11) is opened, the valve 2 (13) is slightly opened, and the nitric acid solution is added to the reaction tank (1). Further, the valve 2 (13) is fully opened, the nitric acid solution is entirely added to the reaction tank by the air (50 ml / min) sent from the air supply line (9), and the inside of the reaction tank (1) is continuously ventilated. .

In this state, heating of the reaction tank (1) is started.
The reaction tank temperature is controlled at a temperature of the temperature control point (17) to a liquid temperature of 80 ± 10 ° C. by the reaction tank temperature controller (2). The radioactive iodine in the sample starts volatilization due to the addition of the oxidizing agent and the temperature effect, and the volatilized radioactive iodine is supplied from the upper part of the reaction tank (1) to the iodine recovery tank via the cooler (4) by the supplied air. It is sent and absorbed (dissolved) in the alkaline solution in the iodine recovery tank.

After a lapse of about 30 to 60 minutes, the three-way cock (5)
Was set to connect the cooler outlet (4) and the water recovery tank (7). The reaction tank (1) is heated until the water in the container evaporates,
Water and volatile components are condensed in the cooler (4) and the water recovery tank (9)
Collected in.

When the liquid in the reaction tank (1) dries, the heating of the reaction tank (1) is stopped, and the reaction tank (1) is cooled by natural cooling. After the cooling of the reaction tank (1) is completed, the valve 1 (11) and the valve 2 (13) are closed,
The sliding joint is once removed, and 30 ml of concentrated sulfuric acid to which 1 ml of concentrated nitric acid is added is put into the chemical injection tank from the sliding joint (12). A sliding joint is connected, valve 1 (11) is opened, valve 2 (13) is slightly opened, and sulfuric acid containing an oxidizing agent is supplied into the reaction tank by air pressure. Fully open valve 2 (13),
The inside of the reaction tank (1) is aerated at 50 ml / min.

Next, the reaction tank (1) is heated again to boil the solution. Technetium and rhenium are volatilized and collected in the water recovery tank (7). After about 60 minutes, the heating of the reaction tank (1) is stopped and the reaction vessel (1) is allowed to cool. Valve 1 (11) and Valve 2 (1
3) is closed, the valve 3 (16) is opened, the valve 4 (14) is slightly opened, and the cleaning solution previously added to the cleaning water tank (10) is injected into the cooler (4). After the injection is completed, open valve 3 (16),
The valve 4 (14) is closed, and the iodine recovery tank (6) and the water recovery tank (7) are removed from the cooling water tank (8).

Table 1 shows the results of the experimental operation thus performed. The iodine recovery rate in the iodine recovery tank (6) is 99.9
%, Almost 100% could be volatilized and recovered. In addition, it was confirmed that the cobalt 60 added to the sample solution had good separation ability only by mixing about 1/1000 of the cobalt 60 into the iodine recovery tank. Technetium recovery rate in water recovery tank (7) is 7
At 3%, the recovery of rhenium added as a technetium carrier was 73%. Also, it was confirmed that the cobalt 60 added to the sample solution had a good separation ability only by mixing about 1/2500000 into the water recovery tank.

[0023]

[Table 1] Technetium and iodine recovery results Recovered liquid recovery rate ⁶⁰ Co decontamination coefficient Iodine recovered liquid 99.9%> 10000 Technetium recovered liquid Tc = 73%, Re = 73% 250,000

[0024]

As described above, the pretreatment operation for radiochemically separating technetium-99 and iodine-129 present in the waste liquid generated from a nuclear facility can be simplified, and the analysis time can be significantly reduced and the chemical time can be greatly reduced. Element separation can be easily performed even by a person who does not need the separation technique. This makes it possible to easily separate technetium and iodine in liquids generated from RI facilities and nuclear facilities, and to easily perform radiochemical separation of technetium 99 and iodine 129, etc., which are trace β-ray emitting nuclides. Radioactivity concentration can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a separation device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tank 2 Reaction tank temperature controller 4 Cooler 3 Chemical injection tank 5 Three-way cock 6 Iodine recovery tank 7 Water recovery tank 8 Cooling water tank 9 Air supply line 10 Cleaning water tank 11 Valve 1 12 Sliding joint 13 Valve 2 14 Valve 4 15 Air cylinder 16 Valve 3 17 Temperature control point

Claims (2)

(57) [Claims] 1. A method for separating radioactive iodine and technetium from a radioactive liquid containing cobalt 60, wherein the radioactive liquid is heated in a nitric acid environment to volatilize and separate radioactive iodine, and a radioactive iodine separation step. Cobalt 60 characterized by comprising a technetium separation step of evaporating and separating technetium by heating and boiling in a sulfuric acid environment dissolved in sulfuric acid, after drying the radioactive liquid after removing iodine. A method for separating radioactive iodine and technetium from a radioactive liquid containing: 2. A reaction tank comprising a chemical injection tank and a volatilization port for taking out volatile components at an upper part, and a heating means for controlling the temperature to a predetermined temperature and a reaction tank temperature controller; A cooler for condensing the volatile components taken out from the outlet, and an iodine recovery tank and a water recovery tank installed in a cooling water tank for collecting radioactive iodine and technetium condensed by the cooler An apparatus for separating radioactive iodine and technetium from a radioactive liquid containing cobalt 60, characterized in that: