JP2007127585A - Simultaneous collection device for tritium and carbon 14 in atmosphere - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device capable of collecting and concentrating with ≥90% efficiency simultaneously, furthermore, capable of automatizing the serial operation without complicated operation for preparation at the collecting site. <P>SOLUTION: This collection device for gaseous ingredient containing tritium the radioactive isotope of hydrogen, and carbon 14 the radioactive isotope of the carbon in the constitution of gaseous specimen in the atmosphere of indoor or outdoor, which converts the gaseous ingredient into the tritium water and carbon oxide gas by making contact with heated oxidation catalyst while continuously sucking the atmospheric specimen. Then the tritium water, carbon oxide gas are continuously collected and concentrated by making a kind of absorption liquid contact with the atmospheric specimen, tritium water and carbon oxide gas, which have large solubility or mixed with high affinity or selectively reacting to the liquid. Thereby, the tritium water and the carbon oxide gas are continuously collected in to the absorption liquid simultaneously and concentrated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for simultaneously collecting gaseous tritium and carbon 14 gas and compounds contained in the atmosphere.

  As a conventional method for collecting tritium and carbon 14 in the atmosphere, tritium is a molecular sieve or a moisture absorption method using silica gel (see Non-Patent Document 1), a cooling aggregation collection method using a cold trap, a liquid collection method, or the like (Non-Patent Document). 2), and carbon 14 includes a collection method using an alkaline solution or a collection method using an adsorbent such as molecular sieve (see Non-Patent Document 3).

  In addition, an apparatus capable of collecting tritium and carbon 14 in the atmosphere with a single unit has been developed (see Patent Document 1 and Patent Document 2), and as shown in FIG. The gaseous components of tritium and carbon 14 are combusted in the combustion tube 17 and converted into tritium water and carbon dioxide gas. The tritium water is converted into solid carbon dioxide and ethanol cold trap 19 and the carbon dioxide gas is converted into 2-aminoethanol (monoethanolamine). ) The carbon dioxide gas trap 21 by aeration to the inside can collect each. The combustion tube 17 is filled with copper oxide as an oxidation catalyst and is heated by an electric furnace 18. Further, the cold trap 19 is incorporated in the dewar bottle 20. There is an activated carbon filled trap 22 between the carbon dioxide trap 21 and the air pump 13b for sucking an air sample, and tritiated water and carbon dioxide gas that have passed through the cold trap and the carbon dioxide trap, and 2-aminoethanol used for the carbon dioxide trap. After the mist and other components are collected and removed by the activated carbon, the air sample is discharged out of the apparatus through the air pump 13b.

  On the other hand, as a gas component collection device, a continuous concentration gas collection device by connecting a nebulizer / denuder that can continuously collect a target component in the absorption solution by continuously contacting a sample gas and a liquid absorbent in the form of a droplet. A gas component that has been developed (see Patent Document 3) and easily dissolved in the same absorbing solution can be collected simultaneously.

Radioactivity measurement series 9 Tritium analysis revised in 2002 Ministry of Education, Culture, Sports, Science and Technology Work environment measurement standard Ministry of Labor Notification No. 73 September 1992 Radioactivity Measurement Method Series 25 Radiocarbon Analysis Method 1993 Science and Technology Agency JP-A-56-90299 JP-A-9-61316 JP 2004-233061 A

  However, according to the above technique, the collection of gaseous components having tritium and carbon 14 in the structure in the atmosphere is performed separately according to the characteristics of the nuclide and the nuclide, and extracted, concentrated or collected after the collection. Each collection operation, such as performing a process such as distillation, requires complicated procedures and assembly of complex test equipment.

  In addition, the tritium and carbon 14 traps in the atmosphere developed so far are filled with solid carbon dioxide and ethanol for the cold trap and assembled as a cold trap as a preparatory operation at the collection site. Collection of 2-aminoethanol and trap assembly are necessary for collection, and after collection, each trap must be disassembled, and each collected solution must be recovered while washing. However, there is also a danger in handling reagents such as solid carbon dioxide.

  Moreover, the atmospheric tritium and carbon 14 collectors that have been developed so far require the above-described preparatory operations and the collection and cleaning operations of the collected liquid after each measurement. It is unsuitable for collecting operation. For example, when measuring time-dependent changes in tritium and carbon 14 in the atmosphere by continuous collection at regular intervals at one measurement point, two or more collection devices are used, and the above preparatory operation and collection after collection. The collection operation must be performed alternately including the liquid recovery and washing operations, which requires a great deal of labor.

  Furthermore, in the conventional technique, when the collection efficiency of tritium and carbon 14 in the atmosphere is 90% or less, the collection result must be corrected by calculation from the temperature and humidity at the time of collection and the atmospheric pressure.

  On the other hand, even when a continuously concentrated gas sampling device using a nebulizer / denuder connection is used, 90% or more is collected by dissolving, mixing, or reacting with all gaseous components having tritium and carbon 14 in the structure. There is no absorption liquid that can be collected, and it is not possible to collect all the components at the same time with only one kind of absorption liquid by directly contacting an air sample with one kind of absorption liquid.

  Therefore, in the present invention, gaseous components having tritium and carbon 14 in the air in the structure are brought into contact with a heated oxidation catalyst and converted into tritium water and carbon dioxide gas, and then brought into contact with one kind of absorbing liquid at the same time. It is an object of the present invention to provide an apparatus capable of concentrating and collecting with an efficiency of 90% or more and further automating a series of operations without requiring any complicated preparation operations at the collection site.

  In order to solve the above problems, the first invention captures gaseous components having tritium, which is a radioactive isotope of hydrogen, and carbon 14, which is a radioactive isotope of carbon, in an outdoor or indoor air sample. An air sample, tritium water and carbon dioxide gas after being continuously converted into tritium water and carbon dioxide gas by contacting the gaseous component in the atmospheric sample to be continuously sucked with a heated oxidation catalyst. Concentrated and collected tritium water and carbon dioxide gas in the absorbent solution at the same time by continuously contacting one kind of absorbent solution that has high dissolving power or high affinity with respect to water or that selectively reacts. A device for simultaneously collecting tritium and carbon 14 in an air sample.

  The second invention is a platinum or copper oxide catalyst in which the oxidation catalyst is heated, and a heating furnace for heating a column filled with the platinum or copper oxide catalyst and a column filled with the platinum or copper oxide catalyst. And an oxidation reaction part comprising a temperature controller for adjusting the temperature of the heating furnace, and the gaseous component continuously converted into tritium water and carbon dioxide gas in the oxidation reaction part is connected to the subsequent stage of the oxidation reaction part The tritium in the air sample is characterized by continuously moving the collected gas collecting part together with the absorbing liquid and continuously collecting and collecting the tritium water and carbon dioxide gas in one kind of the absorbing liquid. And carbon 14 simultaneous collection device.

  According to a third aspect of the present invention, there is provided a cross-flow type nebulizer in which the gas collection unit sprays the absorbing liquid in the form of fine droplets by the flow of the atmospheric sample, and the atmospheric sample and the absorbing liquid in the form of fine droplets are continuous. A denuder tube that flows in contact with each other, and a gas-liquid separation cylinder that inertially separates the absorbing solution and the atmospheric sample connected to the outlet of the denuder tube, and the contact between the atmospheric sample and the absorbing solution in the denuder tube In order to increase the efficiency, this is an apparatus for simultaneously collecting tritium and carbon 14 in an air sample, wherein a glass fiber thread whose surface is coated with a fluororesin is inserted.

  According to a fourth aspect of the present invention, there is provided an air sample collection holder incorporating at least a filter for removing particulate matter in the air sample, the column filled with the oxidation catalyst, the heating furnace, and the oxidation reaction section comprising a temperature controller. , The gas collecting part comprising the cross flow type nebulizer, the denuder pipe and the gas-liquid separating cylinder, an air pump for sucking and taking in the atmospheric sample, and injecting the absorbing liquid into the gas collecting part. An absorption liquid injection pump, an absorption liquid recovery pump for recovering the absorption liquid obtained by concentrating and collecting the gaseous component in the gas collection section from the gas collection section, and the gas collection section Active to adsorb and remove the vapor or mist-like absorbing liquid mixed in the atmospheric sample collected and removed from the gaseous component discharged from the gas-liquid separation cylinder Activated carbon column and a flow rate sensor having a function of measuring the flow rate of the air sample taken in and collecting the total amount of the air sample in the collection of the gaseous component, and part or all of a series of operations Is a simultaneous collection device of tritium and carbon 14 in an air sample.

  According to the first invention, gaseous components of tritium and carbon 14 in the atmosphere are brought into contact with a heated oxidation catalyst to be converted into tritium water and carbon dioxide, and dissolved, mixed or selectively reacted with tritium water and carbon dioxide. Continuously contacting 2-aminoethanol mixed with tritium water and reacting with carbon dioxide gas to dissolve the tritium water and carbon dioxide gas simultaneously into 2-aminoethanol as the absorbent solution. Can be concentrated and collected.

  In addition, according to the second invention, after the gaseous components of tritium and carbon 14 in the atmosphere are converted into tritium water and carbon dioxide gas by the heated platinum or copper oxide catalyst in the oxidation reaction part, It moves in contact with the absorbing solution at the gas collecting unit connected to the latter stage of the platinum or copper oxide catalyst, and tritium water and carbon dioxide gas can be continuously concentrated and collected in one kind of absorbing solution.

  According to the third invention, the gas collecting part is composed of a cross flow type nebulizer, a denuder pipe and a gas-liquid separation cylinder, and a glass fiber thread whose surface is coated with a fluororesin is inserted into the denuder pipe. The contact efficiency between the air sample and the absorption liquid is increased, and the flow rate of the air sample and the absorption liquid is optimized, and the gas is converted into tritium water and carbon dioxide by the oxidation catalyst simply by introducing it into the gas collector. The components can be continuously concentrated and collected in one type of absorbent at the same time and with high efficiency. Taking a recovery test using tritium and carbon 14 standard reagents as an example, the tritium and carbon 14 standard reagents were heated and vaporized, introduced into the oxidation reaction section together with nitrogen gas, and converted to tritium water and carbon dioxide. As a result of introducing the gas sample flow rate to 2.0 l / min and the absorption liquid as 2-aminoethanol and collecting the flow rate at 0.4 ml / min, the tritium is 90% or more, The carbon 14 has a stable recovery rate of 95% or more.

  According to the fourth aspect of the present invention, gaseous components of tritium and carbon 14 in the atmosphere converted into tritium water and carbon dioxide gas in contact with the heated oxidation catalyst in the oxidation reaction section are converted into a cross-flow type nebulizer, a denuder pipe, and A part or all of a series of collection operations for concentrating and collecting the absorbent at the same time can be automatically performed by the gas collection unit including the gas-liquid separation cylinder.

  Furthermore, according to the present invention, tritium and carbon 14 in the atmosphere can be collected continuously for a long time. For example, the absorption liquid in which tritium and carbon 14 are collected is fractionated at regular time intervals or at constant volumes. It is possible to measure the tritium and carbon 14 concentration in the atmosphere safely and easily with less effort by measuring the tritium and carbon 14 for each absorption liquid collected by the fraction collector that can be fractionated and collected. it can.

  Furthermore, since the collection of tritium and carbon 14 in the atmosphere has been separately collected depending on the nuclide and the nature of the nuclide, there are a plurality of collected samples finally obtained in one measurement at one collection point, However, according to the present invention, the final collected sample of tritium and carbon 14 in the atmosphere for one measurement at one collection point is one. For example, it is possible to add a scintillator such as an emulsification scintillator or a toluene scintillator to the obtained collected sample and simultaneously measure the radioactivity with a liquid scintillation counter.

  One embodiment of the present invention is shown in FIG. An air sample containing gaseous components of tritium and carbon 14 is sucked by the air pump 13 a installed at the last stage of the apparatus and taken in from the air sample holder 1. The air sample holder 1 is an open face type filter holder made of synthetic polymer or metal, and although not shown, a filter for removing particulate matter such as dust and foreign matters in the air sample is incorporated. It is. The filter for removing the particulate matter is made of a material that does not adsorb or react with the target tritium and carbon 14 gaseous components, and one kind of sheet filter such as glass fiber, ceramic fiber, or synthetic polymer. Alternatively, two or more types of filters having different materials or hole diameters are used in combination. For example, a glass fiber filter paper and a fluororesin mesh sheet are combined into an air sample holder.

  The air sample taken from the air sample holder is passed through the flow meter 2 with an integration function, and then into an oxidation reaction section 6 comprising a platinum catalyst packed column 3 as an oxidation catalyst, a heating furnace 4, and a heating furnace temperature controller 5. When introduced, the gaseous components of tritium and carbon 14 are converted into tritium water and carbon dioxide. At this time, the platinum catalyst packed column is heated by a heating furnace 4 such as a small tubular furnace, and the heating furnace is maintained at 600 to 800 ° C. by a heating furnace temperature controller 5. Although not shown, a copper oxide catalyst may be used as the oxidation catalyst instead of the platinum catalyst.

  The gaseous components of tritium and carbon 14 in the atmospheric sample converted into tritium water and carbon dioxide gas by the oxidation reaction unit 6 are introduced into the cross-flow type nebulizer 7 of the gas collection unit 10 and at the same time by the absorption liquid injection pump 12. The denuder pipe 7 is moved together with the supplied absorbing liquid. During this time, the atmospheric sample and the absorbing liquid are repeatedly contacted, and tritium water and carbon dioxide gas are simultaneously collected in the absorbing liquid and separated into gas and liquid by inertial separation in the gas-liquid separation cylinder 9.

  The atmospheric sample from which tritium water and carbon dioxide gas are collected and removed by the absorption liquid enters the activated carbon column 11 from the upper part of the gas-liquid separation cylinder, and the vapor and mist of the absorption liquid mixed in the atmospheric sample and the atmospheric sample. Gaseous components that are not collected in an alkaline absorbing solution such as 2-ethanolamine contained in the solution are adsorbed on the activated carbon and removed. The activated carbon column is made of glass or synthetic polymer and filled with granular activated carbon. The air sample that has passed through the activated carbon column passes through the flow control valve 10 and is sucked into the apparatus. Is sucked by the air pump 13a and discharged out of the apparatus.

  On the other hand, after absorbing and separating the tritium water and the carbon dioxide gas by the gas-liquid separation cylinder 9, the absorption liquid is discharged from the lower part of the gas-liquid separation cylinder by the absorption liquid recovery pump 15 as a collected liquid and is shown in the figure. It is not collected in any collection liquid collection container such as vials.

  FIG. 2 shows an embodiment of an oxidation reaction unit for converting a gaseous component having tritium and carbon 14 in the air sample into the structure into tritium water and carbon dioxide gas. The oxidation reaction section used in the present invention comprises the platinum catalyst packed column, the heating furnace 4 and the heating furnace temperature controller 5 as described above, and the platinum catalyst packed column is heated to 600 to 800 ° C. by the heating furnace. Therefore, the column body 3a is made of quartz or ceramic that can be used stably at 600 to 800 ° C. and that does not adsorb or react with the target component. The shape of the column body is tubular, and both ends are narrower than the catalyst packed portion in the center. For example, quartz packed with a catalyst packed portion having an outer diameter of 16 mmφ and both ends having an outer diameter of 6 mmφ and a thickness of about 1.5 to 2 mm. Use a welded tube. At this time, the length of the platinum catalyst filling portion is 100 ± 5 mm, and the column main body is filled with the granular platinum catalyst 3b, and further, quartz wool 3c for sealing the catalyst is filled at both ends of the platinum catalyst. Although not shown, a copper oxide catalyst may be used as the oxidation catalyst instead of the platinum catalyst.

  FIG. 3 shows an example of a gas collection unit that collects tritium and carbon 14 in an air sample converted into tritium water and carbon dioxide gas in an oxidation reaction unit in an absorbing solution. The gas sample injection port 7a and the absorption liquid discharge port 7b are close to each other at right angles, and the absorption liquid is formed into fine droplets by the flow of the gas sample, and the inner wall of the denuder pipe 8 and the inside of the denuder pipe are filled from the nebulizer outlet 7c. The glass fiber yarn filler 8b is sprayed on the surface. Tritium water and carbon dioxide gas are collected in the absorption liquid while it moves in the denuder tube while contacting the air sample and the fine liquid droplet absorption liquid, and then gas-liquid separation is performed by inertial separation in the gas-liquid separation cylinder 9. Is done. The cross-flow type nebulizer, denuder pipe and gas-liquid separation cylinder are made of an alkaline solvent such as 2-aminoethanol, which is suitable for the collection of tritium water and carbon dioxide gas. A fluorine-based resin such as polytetrafluoroethylene (PTFE) or perfluoroalkyl vinyl ether resin (PFA) having no adsorption or reaction was used.

  Although not shown, the tritium and carbon 14 capturing operation in the atmosphere according to the present invention is performed by installing the air sampling holder 1, setting the conditions of the flow sensor 2, adjusting the temperature of the oxidation reaction unit 6, and turning on the air pump 13a. And the flow rate setting of the absorption liquid injection pump 14 and the absorption liquid recovery pump 15 and the installation of the collection liquid collection container, except for the installation of the air sample collection holder 1 and the collection liquid collection container. If the conditions are set in advance, a part or all of the collection operation can be automatically operated only by turning on the power. Further, sensors are provided in the flow rate sensor 2 and the furnace temperature controller 5 and the flow paths of the absorption liquid injection pump 14 and the absorption liquid recovery pump 15 (not shown), and alarm functions in case of an abnormality, for example, sampling of air samples, are provided. Safety in automatic operation by adding functions such as sounding a warning and shutting off the power when an air sample flow rate decreases due to clogging of the holder or heating exceeds the set temperature range of the furnace Can be secured.

  Since the collection of tritium and carbon 14 in the atmosphere according to the present invention is simultaneous collection, one collection sample can be obtained per measurement, and operations such as extraction, concentration, and distillation are not required after collection. It is possible to add a certain amount of a scintillator such as an emulsification scintillator or a toluene scintillator to the collected sample, and simultaneously measure the radioactivity of tritium and carbon 14 with a liquid scintillation counter.

  In addition, according to the present invention, gaseous components having tritium in the atmosphere and carbon 14 in the structure can be collected simultaneously with a collection efficiency of 90% or more in one collection operation regardless of the nuclide and chemical form. Automatic collection is possible without the need for complicated preparations at the collection site. Furthermore, the reagent used is only the absorption liquid 2-aminoethanol, and it is not necessary to process the collected sample such as extraction, concentration and distillation after collection, and the final tritium and carbon 14 can be measured simultaneously. Therefore, the labor cost and the cost of reagents used for collection and measurement can be reduced to ½ or less as compared with the conventional technique.

  The air sample collection holder of the atmospheric tritium and carbon 14 collector according to the present invention is a joint type for pipe connection incorporating an air filter, for example, gas collection branched from a gas system pipe installed in a nuclear facility. The gas sample is directly introduced into the tritium and carbon 14 collection device from the gas system pipe, and the tritium and carbon 14 in the gas sample are collected and discharged from the air sample outlet of the air pump. By connecting the gas sample to the original gas system pipe and returning the gas sample to the original gas system pipe, it is possible to obtain a tritium and carbon 14 collector in the in-line type gas sample. .

  According to this method, it is possible to perform a collecting operation without taking out a gas sample containing tritium and carbon 14 and other radionuclides to the outside, and further, by automating the collecting operation, unattended tritium and carbon 14 Since collection can be performed, radiation exposure to workers during collection operation and radioactive contamination to the environment can be prevented, and a highly safe tritium and carbon 14 collection device can be provided. .

It is a block diagram of the simultaneous collection apparatus of the tritium and carbon 14 in the atmosphere which is one Example of this invention. It is one Example of the oxidation reaction part integrated in the simultaneous collection apparatus of the tritium and carbon 14 in the atmosphere of this invention. It is one Example of the gas collection part integrated in the simultaneous collection apparatus of the tritium and carbon 14 in the atmosphere of this invention. It is a block diagram of the collection apparatus of the tritium and carbon 14 in the atmosphere which is one Example of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air sampling holder 2 Flow rate sensor 3 with integration function Platinum catalyst packed column 3a Column main body 3b Platinum catalyst 3c Quartz wool 4 Heating furnace 5 Heating furnace temperature controller 6 Oxidation reaction part 7 Cross flow type nebulizer 7a Gas sample injection port 7b Absorption liquid discharge port 7c Nebulizer outlet 8 Denuder tube 8a Glass fiber yarn filler 9 Gas-liquid separation cylinder 10 Gas collection unit 11 Activated carbon column 12 Flow rate control valve 13a Air pump 13b Air pump 14 Absorption liquid injection pump 15 Absorption liquid recovery pump 16 Dust filter 17 Combustion tube 18 Electric furnace 19 Cold trap 20 Dewar bottle 21 Carbon dioxide trap 22 Activated carbon filling trap

Claims (4)

  An apparatus for collecting gaseous components having tritium, which is a radioactive isotope of hydrogen, and carbon 14, which is a radioactive isotope of carbon, in an outdoor or indoor atmospheric sample, and which is continuously aspirated in an atmospheric sample The gaseous component is contacted with a heated oxidation catalyst and continuously converted to tritium water and carbon dioxide gas, and then mixed with the atmospheric sample, tritium water and carbon dioxide gas with high solubility or high affinity. Alternatively, tritium and carbon 14 in an air sample characterized in that one kind of selectively reacting absorbing liquid is continuously brought into contact and tritium water and carbon dioxide gas are continuously concentrated and collected in the absorbing liquid. Simultaneous collection device.   The oxidation catalyst is a heated platinum or copper oxide catalyst, a column filled with the platinum or copper oxide catalyst, a heating furnace for heating the column filled with the platinum or copper oxide catalyst, and the temperature of the heating furnace An oxidation reaction part comprising a temperature controller to be adjusted is formed, and the gaseous component continuously converted into tritium water and carbon dioxide gas in the oxidation reaction part is connected to a gas collecting part connected to the subsequent stage of the oxidation reaction part. The tritium in the air sample according to claim 1, wherein the tritium in the atmospheric sample according to claim 1, wherein the tritium in the air sample is continuously moved together with the absorption liquid, and the tritium water and carbon dioxide gas are continuously concentrated and collected in one type of the absorption liquid. Carbon 14 simultaneous collection device.   A cross flow type nebulizer in which the gas collection unit sprays the absorbing liquid into fine droplets by the flow of the atmospheric sample, and the atmospheric sample and the absorbing liquid in the form of fine droplets are in continuous contact. In order to increase the contact efficiency between the air sample and the absorbing liquid in the denuder pipe, comprising a flowing denuder pipe and a gas-liquid separation cylinder for inertial separation of the atmospheric sample and the absorbing liquid connected to the outlet of the denuder pipe The apparatus for simultaneously collecting tritium and carbon 14 in an air sample according to claim 1 or 2, wherein a glass fiber yarn whose surface is coated with a fluororesin is inserted. An atmospheric sampling holder incorporating a filter for removing at least particulate matter in the atmospheric sample, the oxidation reaction section comprising the column filled with the oxidation catalyst, the heating furnace, and the temperature controller, and the cross flow An air pump for sucking and taking in the atmospheric sample, and an absorbing liquid for injecting the absorbing liquid into the gas collecting part An injection pump, an absorption liquid recovery pump for recovering the absorption liquid obtained by concentrating and collecting the gaseous component in the gas collection part from the gas collection part, and the gas-liquid separation cylinder of the gas collection part Filled with activated carbon to adsorb and remove the vapor or mist-like absorbing liquid mixed in the atmospheric sample collected and removed from the gaseous components discharged from Activated carbon column and a flow sensor that has the function of measuring the flow rate of the air sample taken in and collecting the total amount of the air sample in the collection of the gaseous components, and automates part or all of the series of operations. The apparatus for simultaneously collecting tritium and carbon 14 in an air sample according to any one of claims 1 to 3, wherein the apparatus can simultaneously collect tritium and carbon 14.

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