JP4430250B2 - Method and apparatus for simultaneous sampling of H-3 and C-14 in the atmosphere by chemical form - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a method and apparatus for simultaneously collecting and sampling T (H-3) and ¹⁴ C (C-14) in the atmosphere released from a nuclear facility or the like according to chemical form.
[0002]
[Prior art]
Conventionally, collection sampling has been separately performed for H-3, C-14, and the like in the atmosphere.
[0003]
[Problems to be solved by the invention]
Conventionally, H-3, C-14, etc. in the atmosphere, which have been separately sampled, can be collected and sampled at the same time for each chemical form, thereby saving analysis time and reducing analysis cost.
[0004]
[Means for Solving the Problems]
The chemical forms of the main compounds of H-3 and C-14 in the atmosphere are H ₂ O, H ₂ , CO ₂ and CH ₄ . In the present invention, first, after removing water (H ₂ O) with an electronic cooler and an adsorbent, paying attention to the size of the molecule, using the adsorbent adsorbed for each size, a method of fraction collection and Device.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the chemical form of H-3 (T) is water vapor (HTO), hydrogen molecule (HT), hydrocarbon (CH ₃ T), and C-14 is carbon dioxide. Focusing on the point of being ( ¹⁴ CO ₂ ) and hydrocarbon ( ¹⁴ CH ₄ ), the H-3 sample is collected in the form of water and the C-14 sample is collected in the form of CO ₂ . As the adsorbent used for each collection, dry alite (anhydrous calcium sulfate) and molecular sieve (hereinafter MS) 3A are used for the former, and M. is used for the latter. S. 4A was used. By combining these, simultaneous sampling can be performed for each chemical form. The collected components are absorbed as they are for moisture, and CO ₂ is absorbed by a carbon dioxide absorbent (CARBO-SORB-E: Carbosolve E: product name), mixed with a liquid scintillator, and then measured with a liquid scintillation counter. Do.
[0006]
In this counting device, in order to take out water and measure tritium (T), water collected from a column heated in a tubular furnace is sent out as water vapor, cooled in a cooling tube, and recovered as water. Is done. The collected water is added to a scintillator (Aqua Azoru 2 etc.), and the emission of tritium beta rays is counted with a low background liquid scintillation counting device (Aroka Seisakusho). Measure radioactivity in the same way using standard samples with known concentrations. The concentration in the air is calculated by dividing the radioactivity by the flow rate of the collected air.
[0007]
In order to extract CO ₂ and measure the radioactivity of C-14, the M.C. S. The 4A column is heated in a tubular furnace at 400 ° C. or higher for 1 hour while flowing nitrogen gas, and CO ₂ is absorbed by a carbon dioxide absorbent (for example, Carbosolve E) sealed in a gas washing bottle on the downstream side. For measuring the C-14 radioactivity of ¹⁴ CO _2, an absorbent that has absorbed carbon dioxide is added to a liquid scintillator, and the light emitted from the C-14 beta ray is counted with a low background liquid scintillation counter or the like. Measure radioactivity in the same way using standard samples with known concentrations. The concentration in the air is calculated by dividing the radioactivity by the flow rate of the collected air.
[0008]
That is, as shown in FIG. 1, the dry arlite is anhydrous calcium sulfate and can collect water vaporous tritium (HTO) in the atmosphere, and methane tritium (CH ₃ T) in the atmosphere is This is oxidized to water (HTO) and collected by Doialite. However, CO ₂ is not collected by the door light.
[0009]
In addition, M.M. S. 3A can be collected after making hydrogen (HTO) by oxidizing hydrogen tritium (HT). S. 4A is a ¹⁴ CO _2, also can be collected ¹⁴ CH ₄ after a to ¹⁴ CO ₂ oxidation. M.M. S. 3A and M.M. S. As shown in FIG. 1, 4A has different adsorbed molecules depending on the molecular size. Hereinafter, the present invention will be described with reference to examples.
[0010]
【Example】
Example 1
As shown in FIG. 2, the atmosphere containing H-3, C-14, etc. is introduced into the doialite layer (1) to collect HTO, and then M.I. S. Introduced into the 4A layer (2), ¹⁴ CO ₂ is collected, H ₂ is added to the exhaust gas, and HT is oxidized to HTO in the presence of the Pd catalyst (3). S. The HTO oxidized by being introduced into the 3A layer (4) is collected, CH ₄ is added to the exhaust gas, and then introduced into the Pt catalyst layer (5) to convert CH ₃ T into HTO at a temperature of 400 ° C. , ¹⁴ CH ₄ is oxidized to ¹⁴ CO ₂ and then introduced into the dry lite layer (6) to collect HTO. S. Introduced into 4A (7), CO ₂ is collected. As a result, H-3 and C-14 recovered as HTO and CO ₂ were converted into LSC: Aloka. By measuring with LB3 (low background liquid scintillation counting device: Aloka Seisakusho etc.), H-3, C-14, etc. in the atmosphere are simultaneously measured for each chemical form.
[0011]
(Example 2)
As shown in FIG. 3, the atmosphere containing H-3, C-14, etc. is introduced in series into an HTO collection column filled with two towers of dry light, and the HTO present in the atmosphere is captured. The gas that is collected and exhausted therefrom is M.M. S. 4A (molecular sieve 4A) is introduced into the CO ₂ collecting column packed, CO ₂ is trapped present in the atmosphere.
[0012]
After adding hydrogen from the electrolysis cell to the gas discharged from the CO ₂ collection column, it is introduced into the HT oxidation column filled with the Pd alumina catalyst through the mist collection column, and HT is oxidized to HTO. Existing HT is H. S. The sample is collected by an HT collection column packed with 3A (molecular sieve 3A).
[0013]
The gas discharged from the HT collection column is introduced into a methane oxidation column (Pt / alumina catalyst) disposed in a tubular furnace, and CH ₃ T and ¹⁴ CH ₄ in the discharged gas are converted into HTO and ¹⁴ respectively. CH ₃ T oxidized to CO ₂ and present in the atmosphere and
¹⁴ CH ₄ is collected as HTO and ¹⁴ CO _{2 by} a CH ₃ T collection column (dry area) and a ¹⁴ CH ₄ collection column (molecular sieve 4A), respectively.
[0014]
Thus, using the method and apparatus of the present invention, outdoor air and soil air were collected and sampled on the premises of the Japan Atomic Energy Research Institute, Tokai Research Laboratory, and the concentration of each chemical form was quantified, and its performance was demonstrated. FIG. 4 shows the measurement results of the T ( ³ H) and ¹⁴ C concentrations obtained. This shows the measurement results of H-3 and C-14 in outdoor air and soil air, and shows that the present invention is actually applicable to air.
[0015]
According to this, steam-like tritium (HTO) has reached equilibrium at the same concentration level in both outdoor air and soil air, and hydrogen gas (HT) and methane-like tritium (CH ₃ T) concentrations are low in soil air. Being oxidized by microorganisms, C-14 concentration of carbon dioxide ( ¹⁴ CO ₂ ) is higher in soil air than in the atmosphere, and C-14 generated by atmospheric nuclear tests conducted in the past remains in the soil I understand.
[0016]
【The invention's effect】
With the operation of large-scale reprocessing facilities and the progress of fusion research in the future, the behavior of H-3, C-14, etc., which are the main nuclides released from these nuclear facilities, is getting more and more attention. It is coming. For the purpose of obtaining more detailed information for elucidating their behavior and environmental monitoring, the concentration in the atmosphere can be collected and measured by chemical form with a single device, simplifying the monitoring method and reducing costs Figured.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing adsorption objects of dry allite (anhydrous calcium sulfate) and molecular sieves used as adsorbents in the present invention.
FIG. 2 is a diagram showing a sampling flow in the present invention.
FIG. 3 is a diagram showing a ³ H, ¹⁴ C sampling apparatus according to the present invention.
FIG. 4 is a diagram showing a comparison of measurement results between ³ H and ¹⁴ C in outdoor air and soil air according to the present invention.

Claims (2)

A method of simultaneously collecting and sampling HTO, HT, CH ₃ T, ¹⁴ CO ₂ and ¹⁴ CH ₄ in the atmosphere according to chemical form, and collecting HTO with an HTO collection column from the atmosphere containing these, ¹⁴ CO ₂ is collected by the ₂ collection column, H ₂ is added to the exhaust gas from the column, HT is oxidized to HTO by the Pd-containing catalyst in the HT oxidation column, and HT is converted to HTO by the HT collection column. collected, and HTO a CH ₃ T by Pt-containing catalyst in addition after the methane oxidation column in methane gaseous discharge from the column, 14ch ₄ as ¹⁴ CO _2, respectively, CH ₃ T trapping column, ¹⁴ CH _4. The method as described above, which is collected by a collecting column. HTO collection column, CO ₂ collection column, HT oxidation column, HT collection column, methane oxidation column, CH ₃ T collection column and ¹⁴ CH ₄ collection column are connected in series. HTO, HT, CH ₃ T, ¹⁴ CO ₂ and
The ¹⁴ CH ₄ be simultaneous collection sampling apparatus capable by chemical form, sequentially introducing the atmosphere into the column, collecting the HTO in HTO collection column, collecting the CO ₂ in the CO ₂ collecting column, After adding H ₂ , HT is oxidized to HTO with a Pd-containing catalyst in an HT oxidation column, and HT is collected as HTO with an HT collection column. After adding methane to the exhaust gas, CH ₃ with a Pt-containing catalyst is added with a methane oxidation column. T to HTO, ¹⁴ CH ₄ was oxidized to ¹⁴ CO _2, collecting the CH ₃ T in CH ₃ T trapping column as HTO, ¹⁴ CH ₄ collected collecting column with ¹⁴ CH ₄ as ¹⁴ CO ₂ The apparatus as described above.

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