JP2010038802A - Radon emission source, method for manufacturing the same, and radon gas generating method using that radon emission source - Google Patents

Abstract

An object of the present invention is to provide a low-cost radon emission source that satisfies the requirements of high-rate emission, sustainability, and stability required as a radon emission source particularly for radon mist. The above problems are solved by a radon emission source in which radioactive radium is fixed on a carrier made of a porous ceramic mainly composed of cordierite. The radon emission source can greatly increase the amount of radium supported by acid-etching the surface of the carrier before fixing of radioactive radium.
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Description

  The present invention relates to a radon emission source which is easy to handle and has a high rate emission property, a method for producing the same, and a method for producing a high rate and stable radioactive radon gas using the radon emission source for a long period of time. Such radon-emitting radiation sources are used, for example, for coping therapy for lifestyle-related diseases.

  Conventionally, it is known that limited natural facilities such as hot springs containing radioactive decay products such as radon have a healing effect against various diseases (in Japan, Okayama University Hospital Misasa Medical Center in Tohaku-gun, Tottori Prefecture) The complex hot spring therapy at the center is famous). Therefore, in order to easily obtain the same effect as that of such a natural facility, an apparatus for artificially generating an aqueous solution containing a radioactive decay product has been proposed. For example, in patent document 1, the inside of the stirring tank set in the warm aqueous solution in the extraction tank is partitioned by the upper and lower filter plates, and the granular radioactive substance-containing ore is accommodated in the partition, and exists in the upper part of the extraction tank. The granular ore is agitated by pumping gas to the bottom side of the lower filter and spraying it into the agitation tank, while the aqueous solution derived from the bottom of the extraction tank is sprayed from above the extraction tank to spray the upper part of the extraction tank. An apparatus has been proposed in which a gaseous radioactive decay product eluted in a gas is melted in a warm aqueous solution.

  In the above device, it was intended to promote effective elution while stirring with bubbles while ensuring a wide contact area with the warm aqueous solution by granulating the radioactive material-containing ore. When the particle size is reduced, the aperture diameter of the upper and lower filter plates inevitably becomes finer. However, there is a drawback that the smaller the aperture diameter of the upper and lower filter plates, the more difficult the bubbles pass through.

  On the other hand, radium, which is a radon emission source, hardly dissolves in water, but radon has a property of being well dissolved in water and easily evaporating in the air, so a method of using it as a mist is proposed. Has been. Taking radon-dissolved warm water vapor as a mist sauna does not dilute weak radioactivity compared to immersing the body in a warm aqueous solution eluting radon, and radon reaches not only the body surface but also the respiratory system There is an advantage that it is easy to do. In other words, in these mist saunas, radon is floating in the air with water molecules covered around it, so that radon that has entered the human body by breathing is easily discharged out of the human body and stays in the human body. It is thought that alpha rays released in the meantime have a positive effect on human cells.

  Examples of devices that use radon mist include a sauna bath (Patent Document 2) in which a seat and a mist generator are provided in a large box-shaped main body heated by a far-infrared heater, and a mat and an additional mat installed in a sealed room Radon hot spring water is passed through both mats and the radon hot spring water is mist-filled in the sealed room to fill the mist from the respiratory system. A weak radioactive hot spring therapy facility (Patent Document 3) that can inhale radon mist has been proposed.

  By the way, in order to use radon as a mist, it is essential to have a radiation source that has a high rate of release capable of obtaining a high concentration of radon gas, a long-term stable release of radon gas, and a stability that is easy to handle. It is. However, in the conventional radon mist apparatus, only a radium aqueous solution, radon-releasing soil, and the like are assumed, and none of them have obtained sufficient performance, and it was inferior in handling and storage, Recently, a radon emission source using porous ceramics as a carrier and fixing a radium salt insoluble in water has been developed (Patent Document 4). Patent Document 5 proposes a device for generating radon mist, and discloses a porous ceramic panel (made of alumina / cordylite) carrying a radioactive substance as a radon emission source of this device.

Japanese Patent Publication No. 6-48320 (Claims, column 5, line 25 to column 6, line 1, FIG. 1) Japanese Utility Model Publication No. 63-38539 (claim for utility model registration, Fig. 2) Japanese Patent Laid-Open No. 11-128375 (Claims, FIG. 2) JP 2000-327457 A (Claims, Effects of the Invention) JP 2008-142326 A ([0009])

The ceramic radon emission radiation source of Patent Document 4 is a SiC porous sintered body or a SiC porous sintered body coated with TiO ₂ fixed with a radium salt insoluble in water. Although it was an epoch-making radon emission source with rate release, sustainability, and stability, SiC as a base material is not easy to process, and in addition, radium does not directly fix, so insoluble salts are used. Special treatment is required, and the base material itself is expensive, resulting in high costs. Moreover, this ceramic radon emission source uses dry air to generate radon gas, and it was not assumed to be used as a hot water vapor by suction from a respiratory organ. Because the scale as a radiation source is limited due to the relationship, it has been difficult to achieve a numerical value (performance) that is considered clinically effective.

On the other hand, Patent Document 5 discloses alumina / cordylite as a carrier for a ceramic radon emission source. Although this carrier is superior in cost performance to SiC and TiO ₂ as the carrier disclosed in Patent Document 4, the radon concentration released and the stability of the radon concentration released are described later in the examples. However, it was not always satisfactory.

  The present invention has been made in view of the above-mentioned circumstances, and the main problem is that each of the requirements for high-rate release, sustainability, and stability required as a radon emission source particularly for radon mist. The object is to provide a low-cost radon emission source while satisfying it.

  In order to solve the intended problem, in the radon emission source according to the present invention, radioactive radium is fixed to a carrier made of porous ceramics like the radon emission source described in Patent Documents 4 and 5. In addition, a porous ceramic mainly composed of cordierite was used as the carrier. The inventor has a good affinity between cordierite and radium (Ra), which are inexpensive, workable and widely used as heat-resistant parts, and when cordierite is used as a carrier, a high concentration of radon is released. The radon emission radiation source with high-rate release was easily obtained by fixing radium on the surface of a porous ceramic cordierite as a carrier. .

  As the porous ceramic used as the carrier, for example, a lightweight ceramic porous body (ceramic foam) having a porosity of 80% or more is preferably used, and an inorganic ceramic precursor for a porous organic substrate such as filter paper. A method of impregnating a polymer and firing it, or a ceramic powder and a powder binder are uniformly mixed at an appropriate ratio, pressed into a panel shape in a mold, or an organic binder dissolved in a solvent. The ceramic powder can be obtained by a conventional method such as a method in which ceramic powder is uniformly mixed and dispersed to form a ceramic slurry, which is formed into a panel shape by extrusion molding or the like, and fired after drying.

  The radon emission source removes fine powders and coatings adhering to the surface of the carrier by etching the surface of the carrier made of porous ceramics with hydrochloric acid, sulfuric acid, etc. By forming, radium loss can be prevented while further improving the fixing property of radium. In other words, a large amount of radium is supported on the carrier whose surface area is significantly increased by making it more porous.

  The radon emission source according to the present invention can be manufactured by immersing a support made of porous ceramics mainly composed of cordierite in a radioactive radium solution, and drying the support after drying. Prior to these treatment steps, the surface of the support may be etched with an acid in advance.

  As a radioactive radium solution, a mixture of silica fine powder, low melting glass fine powder, etc. dispersed in polyvinyl alcohol and mixed with natural radium ore powder to form a slurry, and a commercially available radium standard solution is also preferably used. It is done. In the present invention, the porous ceramic is immersed in such a radium solution. However, the same effect can be obtained by applying the porous ceramic to the porous ceramic instead of immersing in the solution (that is, in the present invention, such a coating is applied). The method is also referred to as “immersion”).

  The temperature when the sintering process is performed after immersion and drying in the radium solution is preferably about 200 ° C., more preferably about 120 ° C. When sintered at a high temperature, radium (Ra), which is chemically bonded to the outermost surface layer of the support using porous ceramics and is to be stably supported, is hidden in the micropores of the support, and radon (the decay-generated nuclide of radium ( It is desirable to perform low temperature sintering because the amount of released Rn) is reduced. On the other hand, when a usage method in which the radon emission source itself is submerged is expected, the sintering temperature is set slightly higher.

  Further, in the present invention, as a method of generating radioactive radon gas using the radon emission source as described above, the radon emission source is accommodated in a sealed container having a gas inlet and a gas outlet, and the gas inlet side In this method, radioactive radon gas was obtained from the gas discharge port side while injecting the wet gas from the gas discharge port and reducing the output on the gas discharge port side to increase the pressure in the sealed container.

  As described above, in the treatment method using radioactive radon, it is considered effective to suck radon mist in the state where radon molecules are covered with water molecules into the human body by breathing. Although it is necessary to mix with water vapor, the present inventors have made dry room air into a radon emission source by passing wet gas directly through the radon emission source according to the present invention. It was found that radon emission was much higher than when it was passed.

  On the other hand, it has also been found that if the relative humidity of the wet gas is too high, the inside of the sealed container is condensed, and on the contrary, the release rate of radioactive radon gas is lowered, and in some cases it is not released at all. Based on these experimental results, the relative humidity of the wet gas is preferably in the range of 30% to 85%. In some cases, if heating equipment such as a sheathed heater or a heat insulating material is provided outside the airtight container containing the radon emission source, it is effective in preventing condensation. As the wet gas, oxygen or carbon dioxide can be used, but it is easiest to use indoor and outdoor air.

  The high pressure mentioned here means that the pressure in the sealed container is higher than the blowing pressure from the gas inlet side in the sealed container. As the wet gas, in addition to air, gases such as oxygen and nitrogen are used. Is mentioned.

  The radon emission source according to the present invention is not only easy to handle, can obtain highly efficient and sustainable radon gas emission, but also uses as a base material a main component of cordierite that is widely used as heat-resistant ceramics. As a result, it was possible to achieve a significant reduction in manufacturing costs and ease of workability. In particular, the amount of radium supported could be greatly increased by acid etching of the carrier surface.

  In addition, since the radon emission source manufacturing method does not require any special treatment, the manufacturing cost can be greatly reduced by simplifying the manufacturing equipment.

  And, in the method for producing radioactive radon gas according to the present invention using the radon emission radiation source, it is possible to artificially create a radiation radon gas having a much higher concentration than that used in domestic and international natural radon therapy facilities. As a result, it has become possible to carry out effective radon therapy in any place such as a general household without being limited to a specific natural facility.

  The generated radioactive radon gas has a half-life of about 3.5 days. For example, it can be stored in a container filled with an adsorbent such as activated carbon or molecular sieve, and connected to a humidifier. The range of applications is extremely wide, such as being able to perform radon therapy without choosing the time.

  Hereinafter, the present invention will be described in detail according to examples. The performance test as a radon emission source was measured by the apparatus configuration shown in FIG. That is, wet air whose humidity is controlled by a humidifier device 1 having a temperature / humidity sensor and a water level adjustment control function is generated and filled in a laboratory, and then the radon emission source storage unit 3 is compressed by the compressor 2. The gas was injected from the gas inlet side. The radon emission radiation source storage unit 3 was a sealed container and accommodated seven radon emission radiation sources according to the present invention that were shaped like plates along the inner wall. The total supported amount of radium in the housed radon emission source is 12,600 Bq. Radon concentration was measured by installing a radon monitor 5 on the gas discharge port side of the radon emission source storage unit 3 via an adjustment valve 4. As the radon monitor 5, model 1027 manufactured by SUN NUCLEAR, USA was used.

  As the carrier, ceramic foam (part number: M-12 modified, number of cells: 13/25 mm) manufactured by Narita Ceramics Co., Ltd. was used. It is a porous ceramic with cordierite as the main mineral, with open cells and a porosity of 80% or more. In this embodiment, a plate-like (mat-like) shape is adopted, but since various shapes such as a block shape and a columnar shape are already on the market, a shape that matches the internal shape of the radon emission source storage unit 3 is used. Just choose. For example, when the radon emission source storage unit 3 is formed in a cylindrical shape in consideration of the pressurized state, a columnar ceramic foam along its inner wall is used. Further, the number of cells above may be used.

  First, the water absorption amount of the carrier was measured, and the average water absorption amount was obtained in advance. Specifically, after measuring the dry weight (A) of the carrier, immersed in distilled water for a few seconds, gently taken out and drained lightly, and then again measured the water absorption weight (A) of the carrier, The amount of water absorption ((A)-(I)) was determined. Table 1 shows the results of measuring the average water absorption using five 100 mm square carriers.

  The carrier was then acid etched and washed. The carrier was immersed in a 0.5 mol (mol / l) hydrochloric acid solution for 30 minutes for acid etching, rinsed with running water (tap water), and then rinsed twice with distilled water. Thereafter, it was sufficiently dried by heating at 120 ° C. for 1 hour.

On the other hand, the amount of radium (Ra) supported on the carrier was determined with reference to the water absorption amount of the carrier obtained in advance. In this example, 1,800 Bq (1.8 kBq) of radium is carried on each 100 mm square carrier, so that the radioactive water solution is used to obtain 1,800 Bq for an average water absorption of 20 g (= 20 ml). It was decided to make 90Bq per ml (1,800Bq ÷ 20ml = 90Bq / ml). Specifically, since the commercially available radium standard solution was 175 kBq / 5 ml (35 kBq / ml), 0.14 hydrochloric acid (HCl) 3.24 ml was added to 10 ml of the radium standard solution. After adding 580μg of double moles of barium (BaCl ₂ ) and finally adding distilled water to make 389ml, prepare 90Bq / ml of radioactive radium solution, and then 20g of radioactive radium solution per carrier Was supported.

  The step of immersing the carrier in the radioactive radium solution was performed according to the following procedure. That is, after the weight of the carrier is measured in advance, the carrier is immersed in the radioactive radium solution for 5 to 10 seconds and gently lifted to gently remove the liquid. While performing weight measurement again, after adjusting by repeatedly dipping or draining so that the difference from the initially measured weight is close to the average water absorption, heat drying until the carrier is completely dried at 120 ° C for several hours. . Next, the carrier was sintered at 200 ° C. for 2 hours and allowed to cool at room temperature.

[Example 1]
By using the radon emission source obtained by the above processing steps, the apparatus configuration shown in FIG. 1 is used to store the radon emission source storage unit 3 under conditions of an indoor temperature of 21 to 25 ° C. and a humidity of 25 to 40%. While injecting humid air from the gas inlet side at 0.1 MPa (1 atm), the adjustment valve 4 is adjusted to release radon gas at a rate of 0.2 liters per minute (l / min). Measured. The results are shown in FIG. In addition, it is difficult to adjust the radium solution several times after the start of use of the support. A preparatory operation in which wet air is allowed to pass for 4 hours before the start (the same applies to Examples 2-3 and Comparative Examples 1-6).

[Example 2]
Next, using the same apparatus configuration under the same conditions, wet air is injected at 0.2 Mpa (2 atm) from the gas inlet side of the radon emission source storage unit 3, while 0.2 liters per minute from the adjustment valve 4 ( l / min), the radon gas was discharged, and the radon concentration was measured by the radon monitor 5. The results are shown in FIG.

[Example 3]
Further, the same apparatus configuration is used under the same conditions, while wet air is injected at 0.3 MPa (3 atm) from the gas inlet side of the radon emission source storage unit 3, while 0.2 liters per minute (l) from the adjustment valve 4 / min), the radon gas was released, and the radon concentration was measured by the radon monitor 5. The results are shown in FIG.

[Comparative Example 1]
As a comparative example, the same as above except that a ceramic foam (manufactured by Narita Ceramics Co., Ltd., product number: M-6CH-T1, number of cells: 13/25 mm) is used as a carrier for supporting radium. In this manner, radium was supported on alumina. The radon emission source thus obtained is set in the apparatus shown in FIG. 1, and the gas injection of the radon emission source storage unit 3 is performed under the conditions of an indoor temperature of 21 ° C. to 25 ° C. and a humidity of 25% to 40%. While wet air was injected at 0.1 MPa (1 atm) from the inlet side, radon gas was released at 0.2 liters per minute (l / min) by adjusting the adjustment valve 4, and the radon concentration was measured by the radon monitor 5. The results are shown in FIG.

[Comparative Example 2]
The concentration of radon gas released was measured under the same conditions as in Comparative Example 1 except that the pressure of the humid air was changed to 0.2 MPa (2 atm). The results are shown in FIG.

[Comparative Example 3]
The concentration of radon gas released was measured under the same conditions as in Comparative Example 1 except that the pressure of the humid air was changed to 0.3 MPa (3 atm). The results are shown in FIG.

[Comparative Example 4]
As a comparative example, the ceramic foam (made by Narita Seiko Co., Ltd., product number: M-2 substrate, number of cells: 13/25 mm) was used as a carrier for supporting radium as a main component. In the same manner as above, radium was supported on alumina / cordylite. The radon emission source thus obtained is set in the apparatus shown in FIG. 1, and the gas injection of the radon emission source storage unit 3 is performed under the conditions of an indoor temperature of 21 ° C. to 25 ° C. and a humidity of 25% to 40%. While wet air was injected at 0.1 MPa (1 atm) from the inlet side, radon gas was released at 0.2 liters per minute (l / min) by adjusting the adjustment valve 4, and the radon concentration was measured by the radon monitor 5. The results are shown in FIG.

[Comparative Example 5]
The concentration of radon gas released under the same conditions as in Comparative Example 4 was measured except that the pressure of the humid air was changed to 0.2 MPa (2 atm). The results are shown in FIG.

[Comparative Example 6]
The concentration of radon gas released under the same conditions as in Comparative Example 4 was measured except that the pressure of the humid air was changed to 0.3 MPa (3 atm). The results are shown in FIG.

When cordierite is used as a carrier of radium (Examples 1 to 3), as shown in FIGS. 2, 3 and 4, it should be stable in the range of about 4,000 to 8,000 Bq / m ^3. Was confirmed. 2, 3 and each average value of radon concentration in FIG. ^{4 5174.3 Bq / m 3, 6182.9} Bq / m 3, was 6556.5Bq / m ^3. On the other hand, as shown in FIGS. 5 and 6, when alumina was used as the radium support (Comparative Examples 1 and 2), the transition was in the range of 2,300 to 3,000 Bq / m ³ . About FIG. 7 (comparative example 3), it changed in the range of 3,500-6,000 Bq / m < ³ >. The average values of radon concentrations in FIGS. 5, 6 and 7 were 2363.7 Bq / m ³ , 2616.1 Bq / m ³ and 4733.8 Bq / m ³ , respectively.

Further, as shown in FIGS. 8 to 10, when alumina / cordylite was used as a support for radium (Comparative Examples 4 to 6), the transition was in the range of about 1,500 to 3,000 Bq / m ³ . 8, each of the average value of radon concentration in FIGS. 9 and ^{10 2318.0Bq / m 3, 2826.0 Bq} / m 3, was 2493.6Bq / m ^3.

As can be seen from the above examples and comparative examples, when cordierite was used as the carrier among the three types of carriers, the concentration of radon released was in the highest range and was stable. Even when Examples 1 to 3 and Comparative Examples 1 to 6 according to the present invention are compared at an average value, it is clear that the radon emission radiation source of the present invention has higher efficiency emission. became. For example, in the combined spa therapy at Okayama University Hospital Misasa Medical Center, natural radon is used and a radon concentration of about 2,080 Bq / m ³ is used. It has been proved that it can be obtained.

It is the schematic which shows the apparatus structure which performed the performance test of the radon emission source which concerns on this invention. In the apparatus configuration of FIG. 1, elapsed time and radon when cordierite is used as a carrier for supporting radium and the amount of wet air injected and discharged is adjusted so that the radon emission radiation source storage unit is in a non-pressurized state. It is a graph which shows the change of a density | concentration. 2 is a graph showing changes in elapsed time and radon emission amount when cordierite is used as a carrier for supporting radium in the apparatus configuration of FIG. 1 and a pressure difference is provided before and after the radon emission radiation source storage unit. 2 is a graph showing changes in elapsed time and radon emission amount when cordierite is used as a carrier for supporting radium in the apparatus configuration of FIG. 1 and the pressure difference before and after the radon emission radiation source storage unit is further increased. In the apparatus configuration of FIG. 1, the elapsed time and radon concentration when alumina is used as a carrier for supporting radium and the amount of wet air injected and discharged is adjusted so that the radon emission radiation source storage unit is in a non-pressurized state. It is a graph which shows the change of. 2 is a graph showing changes in elapsed time and radon emission amount when alumina is used as a carrier for supporting radium and a pressure difference is provided before and after a radon emission source storage unit in the apparatus configuration of FIG. 1. FIG. 2 is a graph showing changes in elapsed time and radon emission amount when alumina is used as a carrier for supporting radium and the pressure difference before and after the radon emission radiation source storage unit is further increased in the apparatus configuration of FIG. 1. In the apparatus configuration of FIG. 1, the elapsed time when alumina / cordylite is used as a carrier for supporting radium and the amount of wet air injected and discharged is adjusted so that the radon emission source storage unit is in a non-pressurized state. It is a graph which shows the change of radon concentration. 2 is a graph showing changes in elapsed time and radon emission amount when alumina / cordylite is used as a carrier for supporting radium in the apparatus configuration of FIG. 1 and a pressure difference is provided before and after the radon emission radiation source storage unit. FIG. 2 is a graph showing changes in elapsed time and radon emission amount when alumina / cordylite is used as a carrier for supporting radium and the pressure difference before and after the radon emission radiation source storage unit is further increased in the apparatus configuration of FIG. 1. .

Explanation of symbols

1 Humidifier device 2 Compressor 3 Radon emission source storage unit 4 Adjusting valve 5 Radon monitor

Claims (5)

A radon emission source in which radioactive radium is fixed to a carrier made of porous ceramics mainly composed of cordierite. 2. The radon emission source according to claim 1, wherein the surface of the carrier is acid-etched before fixing the radioactive radium. The method for producing a radon emission source according to claim 1, wherein the carrier is immersed in a radioactive radium solution, and the carrier is sintered after drying. 2. The radon emission source according to claim 1, comprising a first step of acid etching the surface of the carrier, a second step of immersing the carrier in a radioactive radium solution, and a third step of sintering the carrier after drying. Manufacturing method. The radon emission source is housed in a sealed container equipped with a gas inlet and a gas outlet, and the inside of the sealed container is pressurized by reducing the output at the gas outlet while injecting wet gas from the gas inlet. 3. A method for producing radioactive radon gas using a radon emission source according to claim 1, wherein the radioactive radon gas is obtained from the gas outlet side.

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