JP3346370B2 - Manufacturing method of radiation source - 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 producing a radiation source which emits radiation such as alpha rays, which is applied to various uses including smoke detectors.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view schematically showing an example of a conventional radiation source.

Conventionally, as a radiation source 11 used for a smoke detector or a random pulse generator, as shown in FIG.
The radiator 14 using ²⁴¹ Am generated by an artificial nuclear reaction as a carrier for gold is used as the radiator 14, and the radiator 14 is placed on the substrate 1 via the gold thin film 13.
In order to suppress a decrease in radiation due to self-absorption of the radiator 14 after the gold-palladium alloy 15 is laminated and pressed thereon, a rolled and thinned one is often used. (See JP-A-9-28899).

For calibration of a radiation measuring instrument, ²¹⁰ Pb (lead), which is a radioisotope, and ²¹⁰ Bi (bismuth) generated by spontaneous decay of ²¹⁰ Pb are in radiation equilibrium. Radiation sources employing radiators are commercially available. In the production of the radiation source, which is a natural radioactive isotope uranium series are present in uranium ores ^{2 26}
Ra (the radium) as a raw material, are fixed by electrodepositing ^{2 10} Pb generated by the natural decay of the ²²⁶ Ra on a substrate.

[0005]

However, in the radiation source 11 using ²⁴¹ Am, since this ²⁴¹ Am is an artificial radionuclide, its production method and disposal are problematic from the viewpoint of impact on environmental pollution. I have.

On the other hand, a radiation source using ²²⁶ Ra as a raw material involves an operation of selectively extracting ²²⁶ Ra contained in uranium ore, which complicates the production method and makes it difficult to reduce the cost. was there.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a radiation source capable of easily manufacturing a radiation source having little influence on environmental pollution.

[0008]

Means for Solving the Problems According to the invention of claim 1 of the present application, ²²² Rn is collected from the natural world, and ²¹⁰ Pb generated by the spontaneous decay of this ²²² Rn is retained.
^{The structure is such that 210} Pb (5) is fixed on the base layer (7).

By employing such a configuration, ²¹⁰ Pb existing in the natural world can be used as a radioisotope, and at the same time, the troublesome work of extracting ²²⁶ Ra in uranium ore is not required.

Here, as the base layer, a substrate (2) provided with a metal layer (4) can be used, and as the material of the metal layer, it is desirable to use gold or an alloy containing gold. . This is because gold easily diffuses with various elements,
Because it is chemically stable, ²¹⁰ Pb can be efficiently fixed on the metal layer (gold).
It is also possible to omit the metal layer and adopt a base layer consisting of only the substrate. When the radiation source manufactured according to the present invention is applied to a consumer level, safety in handling of the radiation source and safety in a process of manufacturing a product to which the radiation source is applied are ensured, and “ Taking into account the regulations of the "Radiation Hazard Prevention Act by Radioisotopes" (Radiation Hazard Prevention Law), the source intensity is 370 Bq
It is desirable to make the following.

Further, the invention according to claim 2 of the present application is to collect ²²² Rn from the natural world, retain ²¹⁰ Pb generated by the spontaneous decay of this ²²² Rn, and then retain the ²¹⁰ Pb.
(5) were fixed on the base layer (7), further, the ²¹⁰ Pb
Is coated with a coating material.

With such a configuration, ²¹⁰ existing in the natural world
Pb can be used as a radioisotope, and at the same time, the troublesome work of extracting ²²⁶ Ra in uranium ore is not required, and the sealing property of ²¹⁰ Pb is improved by coating the coating material. It can be handled as a sealed source.

Further, the invention according to claim 3 of the present application is to collect ²²² Rn from the natural world, retain ²¹⁰ Pb generated by the spontaneous decay of this ²²² Rn, and then retain the ²¹⁰ Pb.
(5) were fixed on the base layer (7), further, the ²¹⁰ Pb
Are interdiffused in the base layer.

With such a configuration, ²¹⁰ existing in the natural world
Pb can be used as a radioisotope, and at the same time, laborious work of extracting ²²⁶ Ra in uranium ore is not required. In addition, ²¹⁰ Pb adheres to the base layer and emits radiation uniformly. Since a radiation surface is formed, it is possible to use ²¹⁰ Pb efficiently even in a small amount particularly in an α-ray source.

When diffusing ²¹⁰ Pb into the metal layer, a flux having an ability to remove an oxide film on the surface of the radioisotope is used in an inert gas atmosphere, an inert gas atmosphere containing hydrogen gas, or the like. The radioactive isotope may be diffused into the metal layer by applying to the fixing surface and heating in that state. In this case, the interdiffusion speed between ²¹⁰ Pb and the base layer is increased by heating, and the surface oxidation of ²¹⁰ Pb is prevented by performing a heat treatment in an inert gas, a hydrogen gas or a flux, so that the interdiffusion is smooth. Done.

Alternatively, the fixing surface may be coated with gold and heated in that state to diffuse the radioisotope into the base layer and the gold. In this case, ²¹⁰ Pb is covered with gold and ²¹⁰ Pb
Since the surface oxidation is reduced, the interdiffusion is performed smoothly.

Further, the invention according to claim 4 of the present application is to collect ²²² Rn from the natural world, retain ²¹⁰ Pb generated by spontaneous decay of the ²²² Rn, and then retain the ²¹⁰ Pb.
(5) were fixed on the base layer (7), further, the ²¹⁰ Pb
Are all interdiffused into the base layer.

With such a configuration, ²¹⁰ existing in the natural world
Pb can be used as a radioisotope, and at the same time, laborious work of extracting ²²⁶ Ra in uranium ore is not required. In addition, ²¹⁰ Pb adheres to the base layer and emits radiation uniformly. Since the radiation surface is formed, ²¹⁰ Pb can be efficiently used even in a small amount, particularly in an α-ray source, and ²¹⁰ Pb is completely diffused into the base layer, so that it can be handled as a sealed radiation source.

The invention according to claim 5 of the present application is a
From the world²²²Rn is collected and this²²²Due to the natural collapse of Rn
Generate²¹⁰Exists in the atmosphere when holding Pb
Do ²²²Rn is collected on a filter and this²²²Rn's self
Naturally generated by collapse²¹⁰Pb in the filter
It is configured to hold.

Here, when collecting ²²² Rn existing in the air by the filter, it may be collected together with dust in the air.

[0021] The invention according to claim 6 of the present application, the ²²² Rn is collected from nature, when holding the ²¹⁰ Pb generated by the natural decay of the ²²² Rn, through the air containing ²²² Rn solvent The ²²² Rn is dissolved in the solvent and collected, and ²¹⁰ Pb generated by spontaneous decay of the ²²² Rn is retained in the solvent.

Here, this solvent may be any solvent that dissolves ²²² Rn, and an example thereof is water.

Further, according to the invention of claim 7 of the present application, when collecting ²²² Rn from the natural world and holding ²¹⁰ Pb generated by the natural decay of this ²²² Rn, air is passed through the ore containing uranium. ²²² Rn contained in the air is collected by a filter or a solvent, and ²¹⁰ Pb generated by spontaneous decay of the ²²² Rn is retained in the filter or the solvent.

At this time, it is preferable to pulverize the ore naturally or artificially before passing air through the ore containing uranium.

Further, the invention according to claim 8 of the present application is to collect ²²² Rn from the natural world, and to retain ²¹⁰ Pb generated by the spontaneous decay of this ²²² Rn, to remove water in which ²²² Rn is dissolved. It is configured to collect and retain ²¹⁰ Pb produced by the spontaneous decay of ²²² Rn in the water. Here, this water includes groundwater, rivers, and the like.

[0026] The invention according to the present claim 9, ²¹⁰
When fixing Pb (5) on the base layer (7), ²¹⁰ Pb
An aqueous solution containing ions is used as an electrolytic solution, a pair of electrodes are immersed in the electrolytic solution, and a voltage is applied between the two electrodes to deposit ²¹⁰ Pb on the base layer and perform electrodeposition. You.

Here, when ²¹⁰ Pb is deposited and electrodeposited, the substrate is used as one electrode (cathode or anode) and a metal or alloy capable of electrodepositing lead is used as the other electrode (anode or cathode). And it is sufficient. Further, a metal (for example, tin) or a metal salt thereof (for example, a metal salt of tin) which mutually diffuses with lead may be dissolved in this electrolytic solution.

Further, the invention according to claim 10 of the present application is:
²¹⁰ Pb (5) when fixed on the base layer (7), ²¹⁰
A metal target containing Pb is deposited on the base layer by sputtering.

It should be noted that reference numerals in parentheses are for convenience showing corresponding elements in the drawings, and therefore, the present invention is not limited to the description in the drawings. The same applies to the column of “Claims”.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a method of manufacturing a radiation source according to the present invention.
FIG. 3 is a cross-sectional view schematically showing a radiation source manufactured by applying the method.
(A)²¹⁰State diagram in which Pb is fixed on a metal layer,
(B) ²¹⁰Pb was fixed on the metal layer and interdiffused
FIG. 2 shows a method for manufacturing a radiation source according to the present invention.
It is a process drawing.

As shown in FIG. 1B, the radiation source 1 has a base layer 7, and the base layer 7 is composed of the substrate 2, the base metal layer 3, and the metal layer 4. That is, a base metal layer 3 made of nickel is stuck on the substrate 2, and a metal layer 4 made of gold is stuck on the base metal layer 3. On the metal layer 4 of the base layer 7, ²¹⁰ Pb
5 are formed in an island shape. Here, since ²¹⁰ Pb 5 is interdiffused in the metal layer 4, the lead-gold diffusion portion 6 is formed.

Although the radiation source 1 in which ²¹⁰ Pb 5 is interdiffused in the metal layer 4 of the base layer 7 has been described,
It is not necessary to interdiffuse ²¹⁰ Pb5, and FIG.
As shown in (a), the radiation source 1 may be configured with ²¹⁰ Pb5 formed in an island shape on the metal layer 4.

The radiation source 1 having the above configuration is
By manufacturing without using ²²⁶ Ra as a raw material and without using artificial radioactive nuclides such as ²⁴¹ Am, the manufacturing method of the radiation source 1 is simplified and cost reduction is realized, and at the same time, the influence on environmental pollution is reduced. can do. Less than,
The specific manufacturing method will be described as first to sixth embodiments.

First Embodiment First, an embodiment in which ²¹⁰ Pb is fixed (precipitated) on a substrate by an electrodeposition method will be described below.

The substrate constituting the radiation source is made of Kovar, and nickel is applied to the surface of the substrate by electrolytic plating.
μm, and further coated with gold by 0.5 to 0.7 μm by electrolytic plating.

As ²¹⁰ Pb, one collected by the following method was used.

The air in the tunnel at the site of the former mine is filtered through a filter, and ²²² Rn (radon: half-life 3.
8) was collected on a filter together with dust in the atmosphere (S1 in FIG. 2). The filter after collecting the ²²² Rn is left for about 30 days, and ²¹⁰ P generated by decay of ²²² Rn is formed.
b (half-life 22.3 years) was retained on the filter (S2 in FIG. 2). Thereafter, this filter was immersed in a nitric acid solution, and ²¹⁰ Pb in the filter was dissolved in the nitric acid solution (S3 in FIG. 2). After dissolving a few milligrams of stable lead (commercially available reagent) in the nitric acid solution in which ²¹⁰ Pb was dissolved, the nitric acid solution was evaporated to produce lead nitrate containing ²¹⁰ Pb.

The conditions for electrodeposition are as follows.

The lead nitrate containing the ²¹⁰ Pb ⁽²¹⁰ Pb
Radiation intensity of 500 Bq (Becquerel)) in 200 ml of water
And then, with sulfuric acid and aqueous ammonia, from pH 2 to p
The aqueous solution was adjusted to be in the range of H3 (S4 in FIG. 2). Using a platinum plate (50 mm x 50 mm) for the anode,
The cathode is the gold-plated Kovar plate (30 mm x 30 m
m) was immersed in the aqueous solution. The back surface of the Kovar substrate was masked with a polyimide-based adhesive tape to prevent ²¹⁰ Pb from depositing on the back surface of the substrate. After this, a constant current of 150 mA was passed between the two electrodes (S5 in FIG. 2). The voltage at this time is from 5.2 V to 5.3 V
Met. Under such conditions, electricity was supplied for 30 minutes to deposit ²¹⁰ Pb-containing lead on the gold plating of the substrate.

After the electrodeposition, the substrate was washed with water and dried, and the masking tape was removed (S6 in FIG. 2). ²¹⁰ Pb obtained by electrodeposition at this time is 420 Bq / 30 mm
× 30 mm. The radiation intensity of ²¹⁰ Pb (B
q) is a gamma ray (46.5 keV) emitted from ²¹⁰ Pb
Is a value measured by a Ge detector. In the present embodiment, several milligrams of stable lead are added and dissolved. For example, the mass of ²¹⁰ Pb per 100 Bq of radiation intensity is extremely small at 3.5 × 10 ⁻¹¹ g. In many cases, the radioisotope of ()) behaves completely differently from ions in the concentration range (normal dose) used in ordinary electrodeposition. In order to prevent this, an appropriate amount of a non-radioactive substance (stable lead) is added as a carrier.

<Second Embodiment> Next, an embodiment in which ²¹⁰ Pb is fixed on a substrate by an electrodeposition method and then heated to diffuse ²¹⁰ Pb into gold plating on the substrate will be described below. .

Table 1 shows the heating conditions and the change in the ²¹⁰ Pb radiation intensity before and after heating. The substrate used and the electrodeposition conditions were in accordance with the first embodiment.

[Table 1]

FIG. 1B is a sectional view schematically showing a radiation source using ²¹⁰ Pb obtained under the heating conditions of Experiments 1 to 3. FIG. 1A is a cross-sectional view schematically showing a state before the heating, in which lead (containing ²¹⁰ Pb) deposited on a metal layer (gold plating) by an electrodeposition method. Indicates a state where is not diffused into the metal layer. FIGS. 1 (a) and 1 (b) are schematically shown for easy understanding of the effect of the present invention. The surface of the substrate after electrodeposition (before heat treatment) and after heat treatment are scanned. Observed by microscope and XMA (X-ray microanalyzer)
The results are shown based on the analyzed results.

As shown in FIG. 1B, the lead (containing ²¹⁰ Pb) and the gold on the substrate are mutually diffused by the heat treatment, and lead and gold diffusion portions are formed in the metal layer (gold plating). Observed. Arrows shown by solid lines in the figure are arrows schematically showing emission of α-rays that can be used as an α-ray source. On the other hand, the arrow shown by the broken line is an arrow schematically showing emission of α-rays that are not detected (cannot be used effectively). These α-rays shown in the figure are ²¹⁰ Po generated by the spontaneous decay of ²¹⁰ Pb.
(Polonium) shows α rays emitted from (Polonium).

In practice, radiation is emitted from random positions in all 4π directions, but for convenience, the emission directions of radiation (α-rays) are described as upward, lateral, and downward on the paper.

The distance (range) in which the α ray travels is extremely short.
If²⁴¹In the case of Am α ray (5.486 MeV), air
Above all, it is about 4 cm.²¹⁰Generated by the decay of Pb
Be ²¹⁰Α rays (5.304 MeV) emitted from Po
The same is true. Therefore, as shown in FIGS. 1 (a) and 1 (b)
Α-rays emitted in the horizontal or downward direction on the paper
It cannot be used effectively because it is absorbed by the substrate or the like.

According to the present invention, lead (containing ²¹⁰ Pb) deposited by the electrodeposition method can be diffused over almost the entire surface of the metal layer (gold plating), and a more uniform radiation surface can be formed. In addition, the radioisotope can be efficiently used in a small amount.

<Third Embodiment> Next, after ²¹⁰ Pb is fixed on a substrate by an electrodeposition method, gold is coated on the fixed surface, and then heated to form a metal on which ²¹⁰ Pb is provided on the substrate. The embodiment diffused in the layer (gold plating) is shown below.

The substrate used and the electrodeposition conditions were the same as in the first embodiment.
Adheres (deposits) lead containing ²¹⁰ Pb on the substrate according to
I let it. Thereafter, gold was deposited on the fixing surface by sputtering to cover the entire fixing surface. The sample thus obtained was subjected to the conditions of Experiment 1 described in Embodiment 2, that is, a nitrogen gas atmosphere (oxygen concentration: 100 ppm) and a temperature of 3.
Heated at 50 ° C. for about 30 seconds.

The surface of the sample before and after the heat treatment was observed and analyzed with a scanning electron microscope and XMA. As a result, as shown in FIG. 1B, lead (containing ²¹⁰ Pb) was obtained by the heat treatment.
And gold on the substrate diffused into each other, and a diffusion portion of lead and gold was observed in the metal layer (gold plating).

According to the present invention, by coating the fixed radioisotope with gold, the surface oxidation of the radioisotope is reduced, and the effect that the interdiffusion between the radioisotope and the metal layer proceeds more smoothly is achieved. can get.

Further, the effect of the present invention can be theoretically explained from a phase diagram of lead-gold. That is, the melting point of lead is 3
Although the temperature is 27 ° C., the melting point of lead shifts to a lower temperature side due to the diffusion of gold, and the ratio of lead-gold is atomic percent and the ratio of lead: gold = 84: 16 has a eutectic point. Has a melting point of 215 ° C. As described above, by coating gold on the lead (containing ²¹⁰ Pb) fixed on the gold plating, diffusion of the lead with the gold proceeds on the pole surface of the lead in a subsequent heat treatment step, and the melting point of this part is reduced. Is shifted to the low temperature side, and the effect that the interdiffusion between lead and gold proceeds more smoothly than in the state without gold coating is obtained.

<Fourth Embodiment> Next, as a method of fixing a radioisotope on a metal layer provided on a substrate constituting a radiation source, a metal target containing a radioisotope is sputtered onto the metal layer. Embodiments in which a radioactive isotope is diffused into the metal layer after being deposited thereon are described below.

A lead target used for sputtering was produced by the following method.

First, as for ²¹⁰ Pb, lead nitrate (containing ²¹⁰ Pb) produced by the method described in Embodiment 1 was used, and a stable lead plate was used for the cathode in the same manner as in the electrodeposition conditions described in Embodiment 1. On this lead plate, lead containing ²¹⁰ Pb was deposited by an electrodeposition method. After the electrodeposition, the lead plate was washed with water, dried, and formed into a shape capable of being sputtered to obtain a lead target.

Using this lead target, ²¹⁰ Pb-containing lead was deposited on the substrate described in the first embodiment by sputtering. The sample thus obtained was heated for about 30 seconds in the condition of Experiment 1 described in Embodiment 2, that is, at a temperature of 350 ° C. in a nitrogen gas atmosphere (oxygen concentration: 100 ppm).

As a result of observing and analyzing the sample surface before and after the heat treatment with a scanning electron microscope and XMA, as shown in FIG. 1B, lead (containing ²¹⁰ Pb) and gold on the substrate were separated by the heat treatment. It diffused mutually and the diffusion part of lead and gold was observed in the metal layer (gold plating).

According to the present invention, the lead (containing ²¹⁰ Pb) fixed on the metal layer (gold plating) can be fixed to the entire surface of the metal layer with a uniform thickness, and the thickness of the lead can be accurately determined under sputtering conditions. Control becomes possible. For this reason, the effect of easily controlling the target radiation intensity (Bq) is obtained.

In this embodiment, lead containing ²¹⁰ Pb is fixed to the surface of a lead plate serving as a base material of a target by an electrodeposition method. However, in consideration of mass productivity, for example, ²¹⁰ Pb is used.
May be melted and diffused into stable lead serving as a base material to produce a target.

Fifth Embodiment Next, a metal layer that diffuses with a radioisotope is provided on a substrate constituting a radiation source, and an alloy containing a radioisotope is formed on the metal layer. The form is shown below.

The substrate used in the experiment was the one shown in the first embodiment. The radioisotope ^{2 10} Pb is also used in the first embodiment.
Lead nitrate produced by the method described in (2) (containing ²¹⁰ Pb)
Was used.

The conditions for electrodeposition are shown below.

[0064] lead nitrate containing the ²¹⁰ Pb ⁽²¹⁰ Pb
Radiation intensity of 500 Bq (Becquerel)) in 200 ml of water
Then, several milligrams of stannous sulfate was added and dissolved, and then, sulfuric acid and aqueous ammonia were used to adjust the pH from 2 to 3
The aqueous solution was adjusted so as to fall within the range described above. Embodiment 1
A platinum plate (50 mm x 50 mm) was used for the anode in the same manner as
The cathode is the gold-plated Kovar plate (30 mm x 30 m
m) was immersed in the aqueous solution. The back surface of the Kovar substrate was masked with a polyimide-based adhesive tape to prevent ²¹⁰ Pb from depositing on the back surface of the substrate. After this, a constant current of 150 mA was passed between the two electrodes.
The voltage at this time was from 5.0 V to 5.2 V. Under such conditions, current is applied for 30 minutes and ²¹⁰ P
Lead containing tin and tin were precipitated. After the electrodeposition, the substrate was washed with water and dried, and the masking tape was removed. ²¹⁰ Pb obtained by electrodeposition at this time is 405 Bq / 30
mm × 30 mm.

Thereafter, the surface of the substrate was observed and analyzed with an electron microscope and XMA, and it was confirmed that lead (containing ²¹⁰ Pb), tin and their alloys were precipitated on the gold plating. The radiation source thus obtained can form an alloy of lead (containing ²¹⁰ Pb) and tin (lead-tin solder) by the method described in Embodiments 2 and 3 described above, In addition, it is possible to easily diffuse into a metal layer (gold plating in this embodiment) mutually diffusing with a radioisotope provided on a substrate constituting a radiation source. Tin is larger than the lead diffusion coefficient of gold, and each other mixed in lead and any ratio, to lower the melting point of lead ⁽²¹⁰ Pb-containing), in easily gold plating ^{2 10} Pb is a radioactive isotope Can be spread.

[0066] in <Sixth Embodiment> Finally, ²²² Rn present in the atmosphere (radon:. The half-life 3 8 days) was collected on a filter with dust in the air, this the collected ²²² R
²¹⁰ Pb (half-life produced by the decay of n 22.3
The following shows an embodiment in which year is stored on the filter.

The filter used was Toyo HE40T (trade name) and the outer diameter was 110 mm, and the filter was mounted on a dust collector. In addition, the diameter of the dust collecting surface of the filter is 100m.
A bendable hose of mφ and length of 10 m was connected.

After inserting the tip of the hose about 5 m into the tunnel of the former mine site having an opening of about 1 m on the ground surface, the air in the tunnel was sucked for 2 hours, and ²²² Rn existing in the air was removed from the air. Collected on the filter with dust. The collection (suction) flow rate at this time was 700 l / min on average.

The filter after the collection of ²²² Rn was left for 30 days, and ²¹⁰ Pb generated by decay of the collected ²²² Rn was retained on the filter. As a result of the measurement, ²¹⁰ Pb retained in the filter was 35 Bq (becquerel). Incidentally, ^{2 10} Pb in the radiation intensity (B
q: Becquerel) is γ-rays emitted from the ²¹⁰ Pb (46.
5 keV) is a value measured by a Ge detector.

As described above, the radiation source obtained by the method described in Embodiments 1 to 6 may have a radiation emission surface coated with a plastic having a thickness of several μm, if necessary.
By contacting and covering the metal thin film, it can be handled as a sealed radiation source.

Further, the radioactive isotope fixed on the metal layer mutually diffusing with the radioisotope can be handled as a sealed radiation source by diffusing all of the radioisotope into the metal layer. In the embodiment described above,
^The method of collecting ²¹⁰ Pb is to filter the air in the tunnel at the site of the former mine through a filter to remove ²²² Rn (half-life 3.
8) was collected on a filter together with dust in the atmosphere,
²¹⁰ Pb (half-life 22.3 years) generated by the decay of ²²² Rn is retained in the filter.
However, there are other methods of collecting ²¹⁰ Pb such as ²²² Pb.
A method of trapping ²²² Rn by passing air containing Rn through a solution dissolving water or radon gas, or a method of trapping ²²² Rn contained in this air by passing air through crushed ore containing uranium. it is also possible to collect ^{2 10} Pb from ²²² Rn which is dissolved method for collecting or groundwater.

[0072] In addition to collecting method ²¹⁰ Pb is the, ²²² Rn similarly atmosphere by spent air-conditioning filters are collected, ²¹⁰ to the filter
Pb is held. Analysis of an air conditioning filter that had been operating for about one year in a certain electronic component manufacturing plant detected ²¹⁰ Pb at 42 Bq / 50 cm × 50 cm. Thus, it is possible to sufficiently collect ²¹⁰ Pb from the air conditioning filter.

Further, in the present embodiment, ²¹⁰ Pb collected by the above-described method is treated with nitric acid to produce ²¹⁰ Pb-containing lead nitrate. However, the present invention is not limited to this. Treatment with an acid may produce the inorganic lead. Furthermore, ²¹⁰ P obtained by treating with acid
The aqueous solution containing b of ions through the anion exchange column, are adsorbed ²¹⁰ Pb in the column after the adsorbed state of the ions, a suitable acidic aqueous solution through within the column into the column ²¹⁰ It is also possible to selectively emit Pb ions to concentrate ²¹⁰ Pb and collect it.

[0074]²¹⁰Pb collapses with a half-life of 22.3 years
²¹⁰Bi (bismuth)²¹⁰Bi has a half-life of 5.0
Devastating in the sun²¹⁰Po. afterwards²¹⁰Po is half-life
Destruction in 138.4 days and stable²⁰⁶Α ray when it becomes Pb
Release. As mentioned above, ²¹⁰Pb is natural radioactive
Element, which exists in nature and eventually becomes non-radioactive
Quality is stable²⁰⁶Pb.

According to the present invention, the ²¹⁰ Pb α-ray source has a lower environmental load than ²⁴¹ Am (half-life: 432 years), which is an artificial radionuclide, can be easily manufactured, and is more easily used on a consumer level. Will be possible.

In this embodiment, only an example in which gold is used as a metal layer capable of interdiffusion with ²¹⁰ Pb is described. However, the present invention is not limited to this. , Gold-platinum, gold-palladium and other alloys,
Also applicable to tin or alloys containing tin, etc.
^{The present} invention can be applied to a combination in which ²¹⁰ Pb and the metal layer can mutually diffuse.

[0077]

As described above, according to claim 1 of the present application,
According to the invention, it exists in the natural world ²¹⁰Radioactive Pb
Uranium can be used as an isotope
In ore²²⁶Eliminates the troublesome work of extracting Ra
Easily produce radiation sources with little impact on environmental pollution
It is possible to produce smoke detectors and random pulses
Providing radiation sources that can be used safely for civil
Can be.

According to the invention of claim 2 of the present application, ²¹⁰ Pb present in the natural world can be used as a radioisotope, and at the same time, ²²⁶ R in uranium ore can be used.
Since the troublesome work of extracting a is not required, a radiation source having little influence on environmental pollution can be easily manufactured. In addition, since the sealing property of ²¹⁰ Pb is improved by coating the coating material, the sealing can be performed. Since the radiation source can be treated as a radiation source, the safety at the time of manufacturing the radiation source is improved.

According to the invention of claim 3 of the present application, ²¹⁰ Pb existing in nature can be used as a radioisotope, and at the same time, ²²⁶ R in uranium ore can be used.
Since the troublesome work of extracting a is not required, it is possible to easily produce a radiation source having little effect on environmental pollution, and also to make the radiation uniform even while ²¹⁰ Pb adheres to the metal of the metal layer. Since a radiation surface to be emitted is formed, it is possible to efficiently use even a small amount of ^{2 10} Pb in an α-ray source, so that the production cost of the radiation source can be reduced.

According to the invention of claim 4 of the present application, ²¹⁰ Pb existing in the natural world can be used as a radioisotope, and at the same time, ²²⁶ R in uranium ore can be used.
Since the troublesome work of extracting a is not required, it is possible to easily produce a radiation source having little effect on environmental pollution, and also to make the radiation uniform even while ²¹⁰ Pb adheres to the metal of the metal layer. since the radiating surface that emits is formed, it is possible to efficiently utilize even small amounts of ^{2 10} Pb in particular α-ray source, it is possible to reduce the manufacturing cost of the radiation source, moreover, it does not remain ²¹⁰ Pb Since it diffuses into the metal layer, it can be handled as a sealed radiation source, so that the safety in manufacturing the radiation source is improved.

According to the fifth to eighth aspects of the present invention, since ²¹⁰ Pb can be easily held, the production of the radiation source is further facilitated.

Further, according to the ninth and tenth aspects of the present invention, since ²¹⁰ Pb can be securely fixed on the metal layer, the quality of the radiation source is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a radiation source manufactured by applying the method of manufacturing a radiation source according to the present invention, wherein (a) is a cross-sectional view.
State diagram the ²¹⁰ Pb was fixed on the metal layer, (b) is ²¹⁰ P
FIG. 6 is a diagram showing a state where b is fixed on a metal layer and interdiffused.

FIG. 2 is a process chart showing a method for manufacturing a radiation source according to the present invention.

FIG. 3 is a cross-sectional view schematically illustrating an example of a conventional radiation source.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Radiation source 2 ... Substrate 4 ... Metal layer 5 ... ²¹⁰ Pb 7 ... Base layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-50-47096 (JP, A) JP-A-1-253699 (JP, A) JP-A-7-128499 (JP, A) JP-A 5- 264794 (JP, A) JP-38-19900 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25D 3/34 C23C 14/34 C25D 5/00 G21G 4/04

Claims (10)

(57) [Claims] [Claim 1] to collect the ²²² Rn from the natural world, this ²²²
A method for producing a radiation source, comprising: holding ²¹⁰ Pb generated by spontaneous decay of Rn, and then fixing ²¹⁰ Pb (5) on a base layer (7). 2. The method of claim 1] to collect the ²²² Rn from the natural world, this ²²²
After holding ²¹⁰ Pb generated by spontaneous decay of Rn, the ²¹⁰ Pb (5) is fixed on the base layer (7), and the ²¹⁰ Pb is coated with a coating material. Source manufacturing method. [Claim 3] to collect the ²²² Rn from the natural world, this ²²²
After holding ²¹⁰ Pb generated by the spontaneous decay of Rn, the ²¹⁰ Pb (5) is fixed on the base layer (7), and the ²¹⁰ Pb is mutually diffused into the base layer. Method of manufacturing the radiation source. 4. to collect the ²²² Rn from the natural world, this ²²²
After holding ²¹⁰ Pb generated by the spontaneous decay of Rn, this ²¹⁰ Pb (5) is fixed on the base layer (7), and all of this ²¹⁰ Pb is mutually diffused into the base layer. Method of manufacturing a radiation source. 5. to collect the ²²² Rn from the natural world, this ²²²
When ²¹⁰ Pb produced by the spontaneous decay of Rn is retained, ²²² Rn present in the atmosphere is collected by a filter,
^{The method according} to any one of claims 1 to 4, wherein ²¹⁰ Pb generated by spontaneous decay of ²²² Rn is retained in the filter. 6.] to collect the ²²² Rn from the natural world, this ²²²
When holding the ²¹⁰ Pb generated by the natural decay of Rn, through the air containing ²²² rn solvent, the ²²² Rn is collected is dissolved in the solvent, it is produced by the natural decay of the ²²² Rn ²¹⁰ The method for producing a radiation source according to claim 1, wherein Pb is held in the solvent. 7. collected from the natural world ²²² Rn, this ²²²
When holding the ²¹⁰ Pb generated by the natural decay of Rn, passing air into the ore containing uranium, collecting the ²²² Rn contained in the air filter or a solvent, the ²²²
The method according to any one of claims 1 to 4, wherein ²¹⁰ Pb generated by spontaneous decay of Rn is retained in the filter or the solvent. 8.] to collect the ²²² Rn from the natural world, this ²²²
When holding the ²¹⁰ Pb generated by the natural decay of Rn, ²²² Rn is collected the water is dissolved, the water ²²² R
The method according to any one of claims 1 to 4, wherein ²¹⁰ Pb generated by the natural decay of n is held in the water. 9. When ²¹⁰ Pb (5) is fixed on the base layer (7), an aqueous solution containing ions of ²¹⁰ Pb is used as an electrolyte, a pair of electrodes are immersed in the electrolyte, and a voltage is applied between both electrodes. The method according to any one of claims 1 to 4, wherein ²¹⁰ Pb is deposited on the base layer by electrodeposition and electrodeposited. 10. The method according to claim 1, wherein, when the ²¹⁰ Pb (5) is fixed on the base layer (7), a metal target containing ²¹⁰ Pb is deposited on the base layer by sputtering. A method for producing a radiation source according to claim 4.