JPS6220833B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a radioactive aqueous solution that is useful for hot baths, drinks, various disease treatments, etc. The present invention relates to a method for efficiently extracting radioactive decay products by bringing an isotope-containing substance into contact with an organic acid aqueous solution to produce a radioactive aqueous solution.

It is well known that when natural radium hot springs or mineral springs are used for bathing or drinking, they are effective in treating various diseases. This natural radium mineral spring contains radon, which is a type of radioactive decay product, and is thought to be radioactive.
Although naturally produced aqueous solutions containing radioactivity are known, artificially produced solutions have not been known. This is because it is difficult to extract radionuclides present in natural radioactive minerals and artificial radioactive substances with water.

As a result of various studies conducted by the present inventors on methods for artificially obtaining radioactive aqueous solutions, we found that if a radioactive isotope-containing substance is first treated with an organic acid aqueous solution, the radioactive decay products in it can be removed. He discovered that a portion of the radioactive solution could be extracted to obtain an aqueous solution containing radioactivity, and proposed an apparatus for carrying out this process (Japanese Patent Laid-Open Publication No. 42613/1983). The radioactive decay products referred to here are radioactive isotopes containing α-rays, β-rays,
A substance that is generated during the intermediate process of emitting gamma rays and converting into stable isotopes.

However, the extraction tank in this production device is constructed in such a way that the bottom of the inner cylinder of a double cylindrical container as shown in Fig. 3 is used as a filter, and the filter is filled with, for example, monazite granules as a fixed bed. The extraction operation is carried out by circulating the extraction liquid using the water pressure caused by the water level difference between the outer cylinder 13 and the inner cylinder 14. Therefore, if the amount of granules filled is large or the specific gravity of the granules is large, the water level difference may be increased. Therefore, the outer cylinder needs to be taller, and the water level of the inner cylinder often becomes lower than the suction port of the pump 15, making the pump ineffective. Alternatively, since the extraction liquid is taken out from the liquid outlet 16 at the bottom, there are problems such as the extraction liquid in the inner cylinder is difficult to take out due to the resistance of the granules, so this device is not necessarily satisfactory. isn't it.

As a result of further intensive research into methods for producing radioactive aqueous solutions, the inventors of the present invention have found that, for example, by using a fluidized circulation contact type extraction device as shown in a schematic cross-sectional view in FIG. If radioactive decay products are extracted by bringing the fine particles of the radioisotope-containing substance into contact with an organic acid aqueous solution so that the substance can form a fluidized bed, an aqueous solution having radioactivity can be efficiently obtained. The present invention was completed based on this finding.

That is, in the present invention, when producing a radioactive aqueous solution by bringing a radioactive isotope-containing substance into contact with an organic acid aqueous solution and extracting radioactive decay products from the radioisotope-containing substance, a filter layer is used to produce a radioactive aqueous solution. It consists of a cylindrical container divided into upper and lower parts, with a liquid outlet in the upper part and a liquid inlet in the lower part, and a circulation path is formed between the liquid outlet and the liquid inlet via a pump. Using a fluidized circulation contact type extraction device, first fill the filter of the device with a fine particulate radioactive isotope-containing substance, and then pour the organic aqueous solution so that the liquid level is above the liquid outlet of the device. production of an aqueous solution with radioactivity, characterized in that the organic acid aqueous solution is circulated by a pump of the device so that the finely divided radioactive isotope-containing substance can form a fluidized bed. The present invention provides a method.

The radioisotope-containing substance used in the method of the present invention may be either a natural radioactive mineral or an artificial radioactive substance. Examples of these natural radioactive minerals include uranium-containing minerals such as uranite, pitublend, apatite, and branellite; thorium-containing minerals such as thorite,
There are various uranium minerals mentioned above that contain radium, such as trogomite, galena, monazite, and xenotime, but monazite is used because it is easy to obtain, has a mild action, and is harmless to the human body. (a phosphate mineral of Ce, La, Y, and Th) and xenotime (a phosphate mineral of Y, Ce, Er, U, and Th) are preferred. Furthermore, examples of artificial radioactive substances include various compounds containing radioactive isotopes.

In the present invention, these radioactive isotope-containing substances are used after being crushed into fine particles of a size that can form a fluidized bed. This size varies depending on the type, concentration, circulation speed, and specific gravity of the radioisotope-containing substance of the organic acid aqueous solution used, but is usually in the range of 20 to 150 mesh.

By the way, the above-mentioned natural radioactive minerals are dissolved and treated with strong reagents such as sulfuric acid, alkali, or chlorine, and used as industrial chemicals.
All of these products contain powerful chemicals, so they are unsuitable for hot baths, drinking, or medical treatment.

In the method of the present invention, as an organic acid aqueous solution,
For example, aqueous solutions of organic acids with weak effects such as acetic acid, citric acid, succinic acid, tartaric acid, and oxalic acid are preferably used. Among these aqueous solutions, an aqueous solution of citric acid is preferred because it is harmless to the human body, satisfies the requirements of being colorless and odorless, and is relatively inexpensive.

In the method of the present invention, the concentration of the organic acid aqueous solution is preferably 0.05 to 10% by weight, and the pH is preferably in the range of 1.5 to 3.5.

Next, one example of an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of an extraction device suitable for use in the method of the present invention. It has a liquid supply port 3 at the top for supplying the organic acid aqueous solution, a liquid outlet 4 at the top of the container, a liquid inlet 5 at the bottom, and a liquid inlet 4 at the bottom to circulate the organic acid aqueous solution. It has a pump 6 and a circulation pipe 7, and is further provided with a drain port 8 and, if necessary, a barrier plate 9 having a number of holes for preventing channeling of the circulating fluid flowing in from the fluid inlet 5. There is. The holes in this board are larger on the circumferential side and smaller in the center.

In the method of the present invention, first, a radioactive isotope-containing substance such as finely divided monozite or xenotime, which has been crushed to a size of 20 to 150 mesh, is placed on the filter 2 of the extraction device from the filter 2 to the liquid outlet 4. After filling the liquid to a height of about 1/10 of the distance of Supply to position. Next, the organic acid aqueous solution is circulated from the liquid outlet 4 to the liquid inlet 5 using the pump 6 and the circulation pipe 7, thereby forming a fluidized bed of the fine particulate radioisotope-containing substance. , to extract radioactive decay substances. The circulation rate of the organic acid aqueous solution at this time is adjusted so that the height of the fluidized bed of the radioisotope-containing substance is about 2 to 3 times the height in a stationary state. In addition, this extraction can be carried out at room temperature, but if the temperature is low, it will take a long time to obtain the desired dissolved concentration of radioactive decay products, making it impractical. Preferably, an aqueous organic acid solution heated to a certain temperature is used. By using an organic acid aqueous solution at such elevated temperature, an aqueous solution having a radioactivity dose of 50 to 1000 pine can be obtained in an extraction time of 1 to 10 hours. The dose unit ``matsuhe'' is a dose unit based on radon and corresponds to kyuri.

When the radioactive aqueous solution obtained in this way is analyzed by γ-ray spectrometry,
The presence of nuclides such as ²²⁶ Rd, ²¹² Pb, ²¹⁴ Pb, ²⁰⁸ Tl, and ²¹² Bi is observed. This indicates that radioactive decay products are dissolved in the obtained aqueous solution.

After this extraction, the radioactive aqueous solution is taken out from the drain port 8 and stored in a stock solution tank as desired.

Further, the extraction apparatus used in the present invention may be operated in batch mode, or may be operated in continuous mode by connecting with a liquid supply pipe and a liquid drain pipe.

In the method of the present invention, by using a fluid circulation type contact extraction device, it is possible to produce an aqueous solution containing radioactivity extremely efficiently, and the obtained aqueous solution is diluted as necessary to adjust the dose and temperature. ,PH
After adjusting the ingredients, it can be used as a hot bath, a drink, a therapeutic medicine, etc.

Next, the present invention will be explained in more detail with reference to Examples.

Example A radioactive aqueous solution was produced using an apparatus system as shown in FIG.

In FIG. 2, A is an aqueous solution preparation tank equipped with a stirring device for preparing an organic acid aqueous solution by mixing water and an organic acid, B is a tank for bringing the organic acid aqueous solution into contact with a radioactive isotope-containing substance, Fluid circulation contact extraction device for extracting radioactive decay products;
C is a stock solution tank, and D is an adjustment tank for adjusting the temperature of the extraction stock solution, the concentration of organic acid, PH, and dose to the conditions of use. A filter having the structure shown in FIG. 1 with a height of 100 cm from the filter to the liquid outlet 4 was used, and a 1 mm thick Teflon nonwoven fabric was used as the filter.

First, hot water at 100° C. is introduced from the supply pipe 10 and citric acid powder is introduced from the supply pipe 11 into the aqueous solution preparation tank A to prepare a citric acid aqueous solution (PH about 3) having a concentration of 1% by volume. Next, 1000 kg of the citric acid aqueous solution prepared in this way was added to the
Monazite granules with a viscosity of 100 mesh 50
kg (3 kg in terms of thorium) is fed to the extraction device B (in this case, the liquid level is located above the liquid outlet 4), and the pump 6 is operated so that the monozite granules are 2 to 3 kg of the static height. The aqueous solution was circulated at a circulation rate such that a fluidized bed with double height was formed. Extraction was carried out at a temperature of 90-95°C for 4 hours. Through this treatment, only the radioactive decay products are extracted without dissolving the ore. Next, this extract is sent to stock solution tank C and stored. The dose of the extract thus obtained is approximately 500 m. Next, put this extract into the adjustment tank D, and add 20 times as much hot water to the hot water supply pipe 12.
By supplying and diluting the water, a dose of 25 matsuhe of hot water can be obtained. The citric acid concentration of this hot water is
It is 0.05% by volume and has a PH of 3.5, which is comparable to the soft water of ordinary drinkable weakly acidic hot springs.

When this material was analyzed by gamma ray spectrometry, nucleation of ²²⁶ Rd, ²¹² db, ²¹⁴ Pb, ²⁰⁸ Tl, and ²¹² Bi was detected. Also, the radioactivity of this thing is about 12
Showing the half-life of time.

Comparative Example The extraction device shown in Figure 3 (outer cylinder diameter 100 cm, inner cylinder diameter 60 cm, inner cylinder height 80 cm) was filled with 50 kg of the same monazite granules as used in the example, and under the same conditions as in the example. Extraction with an aqueous citric acid solution was performed.

The dose of the extract thus obtained is approximately 100
It is Matsuhe.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an extraction device suitable for use in the method of the present invention, and FIG. 2 is a schematic cross-sectional view of an extraction device suitable for use in the method of the present invention.
The example flow sheet, FIG. 3, shows a schematic cross-sectional view of a conventional extraction tank. In the figure, 2 is a filter, 4 and 16 are liquid outlet ports, 5 is a liquid inlet port, 6 and 15 are pumps, 7 is a circulation pipe, 13 is an outer cylinder, 14 is an inner cylinder, and A is an organic acid aqueous solution preparation tank , B is an extraction device, C is a stock solution tank, and D is an adjustment tank.

Claims (1)

[Claims] 1. When producing a radioactive aqueous solution by bringing a radioactive isotope-containing substance into contact with an organic acid aqueous solution and extracting the radioactive decay products in the radioisotope-containing substance, the organic acid is separated into upper and lower parts by a filter layer. , a fluid circulation contact type, consisting of a cylindrical container with a liquid outlet at the top and a liquid inlet at the bottom, and a circulation path formed between the liquid outlet and the liquid inlet via a pump. Using an extraction device, first fill the filter of the device with a fine particulate radioactive isotope-containing substance, and then fill it with an organic acid aqueous solution so that the liquid level is located above the liquid outlet of the device,
A method for producing an aqueous solution having radioactivity, characterized in that the organic acid aqueous solution is then circulated by a pump of the apparatus so that the fine particulate radioactive isotope-containing substance can form a fluidized bed.