An on-line measuring device for high-concentration tritium gas

Abstract

The present invention provides an on-line measuring device for high-concentration tritium gas, belonging to the technical field of tritium gas detection devices. It includes a sealed detection chamber, a vacuum coupling cavity and a sample chamber. The sample chamber is successively provided with a bremsstrahlung target film, a heating layer capable of heating the bremsstrahlung target film and a sample chamber housing from inside to outside. The material of the bremsstrahlung target film is a high-atomic-number metal with a high X-ray yield after interacting with β rays. An X-ray detector is arranged in the detection chamber. A tritium gas inlet and a tritium gas outlet are respectively arranged at both ends of the sample chamber. The enclosure of the vacuum coupling cavity contains components that allow X rays to enter the detection chamber from the sample chamber. The present invention has the advantages of repeatable and high-precision detection of tritium gas volume, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of tritium gas detection devices, and relates to an on-line measuring device for high-concentration tritium gas. Background Art

[0002] When the β-rays released during the spontaneous decay of tritium interact with metal materials through bremsstrahlung, low-energy X-rays are generated. Tritium can be indirectly measured by measuring the X-rays. Since tritium does not come into contact with the detector, it can prevent tritium from remaining on the detector and reduce the memory effect. This characteristic makes it widely used for on-line measurement in high-concentration tritium gas fields.

[0003] Common techniques for on-line monitoring of gaseous tritium include ionization chambers, gas chromatography, and mass spectrometers, etc. Ionization chambers can be used on-line, but due to their sensitivity to the chemical composition of gases, strong memory effect, the need for regular recalibration, and the requirement to operate under optimal conditions, their applications are limited. Gas chromatography allows for partial chemical and isotope determination of gas mixtures, but due to the long analysis time, it is not suitable for rapid process monitoring and cannot be used on-line. Mass spectrometry provides the possibility for real-time on-line monitoring. However, the interference of equivalent heavy elements makes the mutual interpretation of spectra quite difficult. To enable the normal operation of the mass spectrometer, the need for a turbo molecular pump device, the risk of filament failure, and the deionization effect are further exacerbated.

[0004] In the published technical solution reported in the open publication "Characteristics of a promising tritium process monitor detecting bremsstrahlung X-rays" in Nuclear Instruments and Methods in Physics Research A (2017), a stainless-steel sensitive chamber, a gold-plated bremsstrahlung material, and a NaI probe were used to measure the tritium gas concentration. Due to the too large memory effect of the stainless-steel sensitive volume used, the detection limit for on-line monitoring is 10 11 Bq / cm 3 . In the published technical solution reported in the open publication "Activity monitoring of a gaseous tritium source by beta induced X-ray spectrometry" in Fusion Engineering & Design (2013), an SDD (silicon drift detector) was used to replace the fluorescent medium and the photomultiplier tube, reducing the background interference, increasing the signal stability, and reducing the memory effect by three orders of magnitude. The detection limit for 100 s is 10 6Bq, but the relatively large memory effect is also introduced by the sensitive volume of stainless steel. In the publicly reported technical solution in the open publication "Development of a compact tritium activity monitor and first tritium measurements" published in Fusion Engineering and Design (2015), after gold plating the sensitive volume inside stainless steel and the surface of the SDD detector, the memory effect is reduced by two orders of magnitude, but it can only be used under a pressure of less than 100 Pa. In the publicly reported technical solution in the open publication "Investigations of the applicability of a new accountancy tool in a closed tritium loop" published in Fusion Engineering and Design (2016), in order to miniaturize the detection device, the usable pressure range is extended to 1 kPa.

[0005] It can be seen that the above publicly reported technical solutions do not give the reusable performance of the detection device, and the performance under a pressure greater than 1 kPa has not been reported yet. Summary of the Invention

[0006] The object of the present invention is to provide an on-line measuring device for high-concentration tritium gas in view of the above problems existing in the prior art. The technical problem to be solved by the present invention is to perform on-line detection of tritium gas repeatedly and with high precision.

[0007] The object of the present invention can be achieved by the following technical solutions: An on-line measuring device for high-concentration tritium gas, characterized in that it includes a sealed detection chamber, a vacuum coupling chamber and a sample chamber. The sample chamber is sequentially provided with a bremsstrahlung target film, a heating layer capable of heating the bremsstrahlung target film and a sample chamber housing from the inside to the outside. The material of the bremsstrahlung target film is a high atomic number metal with a high X-ray yield after interacting with β rays. An X-ray detector is arranged in the detection chamber.

[0008] A tritium gas inlet and a tritium gas outlet are respectively arranged at both ends of the sample chamber. The enclosure of the vacuum coupling chamber includes a component that allows X rays to enter the detection chamber from the sample chamber.

[0009] Further, the vacuum coupling chamber consists of a sealed cylinder, an incident window plate blocking one end of the sealed cylinder close to the sample chamber, and an exit window plate blocking one end of the sealed cylinder close to the detection chamber. Both the incident window plate and the exit window plate are made of materials that allow X rays to penetrate.

[0010] Further, the incident window plate is made of aluminum or carbon material.

[0011] Further, the exit window plate is made of beryllium.

[0012] Further, the detector is a NaI or high-purity germanium or silicon drift detector.

[0013] Preferably, the detector is a silicon drift detector.

[0014] Further, the material of the bremsstrahlung target film is one or several of gold, tungsten, or nickel.

[0015] The material of the bremsstrahlung target film is a high atomic number metal that has a high X-ray yield after interacting with β rays.

[0016] Preferably, the material of the bremsstrahlung target film is gold.

[0017] Further, the heating layer is a coating of zirconium metal, embedded between the bremsstrahlung target film and the sample chamber housing.

[0018] Further, a gasket is provided between the detection sealed chamber and the sample sealed chamber.

[0019] The principle is as follows:

[0020] This solution is an online tritium concentration measurement device with low memory effect based on the bremsstrahlung principle (BIXS). Tritium gas enters the sample sealed chamber from the tritium gas inlet, and after β decay, it interacts with the bremsstrahlung target film on the inner wall of the sample sealed chamber to generate X-rays. The X-rays pass through the incident window plate into the vacuum coupling cavity, and then pass through the exit window plate into the detection sealed chamber. After being detected by the detector, the value of the X-rays is obtained, and then through computer processing, it is converted into the corresponding value of tritium gas, thereby realizing the detection of the amount of tritium gas in the sample sealed chamber.

[0021] By designing a heating layer in the sensitive volume, the residual tritium gas in the sample chamber can be removed by heating after use; the incident window plate can be removed and replaced after long-term use; the non-contact measurement method can avoid the direct attachment of tritium gas to the probe. All of the above measures can improve the detector memory effect.

[0022] The present invention can greatly improve the detector memory effect by designing a heating coating in the sensitive volume, adopting a movable sample chamber sealing window, and a non-contact measurement method. It has the characteristics of low price, accurate measurement results, high tritium gas concentration measurement, online measurement, and compact structure.

[0023] It should also be clarified that the vacuum coupling cavity is provided to isolate the tritium gas in the sample sealed chamber from entering the detection sealed chamber; the heating layer mainly heats to remove the tritium gas adsorbed on the bremsstrahlung target film. This is because metals have a retention effect on tritium gas. By heating, the tritium gas remaining in the metal can be removed, which can eliminate the influence of non-introduced tritium gas on the detection results during the interval between two detections. So that the data obtained by the detector during the next detection is the data of the rays corresponding to the tritium gas passing through the sample sealed chamber at this time, and there will be no rays generated by the tritium gas remaining in the sample sealed chamber during the previous gas injection; heating is conducive to gas removal, which can ensure that most of the tritium gas does not remain in the sample sealed chamber before the second detection. It is common knowledge in the industry that tritium decay produces rays. Other details such as the specific structure of the detector and the computer analysis program are well-known in the art and will not be elaborated here.

[0024] The detection device of this invention application adopts a movable bremsstrahlung material and an internal coating heating design, and designs appropriate dimensions through Monte Carlo to reduce the memory effect of the detection device, improve the reusability performance and broaden its application range, which is significantly different from the existing BIXS detector design.

[0025] Since the incident window plate needs to be replaced, in this solution, the incident window plate is made of inexpensive material, and the exit window plate does not need to be replaced and is made of beryllium, which is expensive. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of a high-concentration tritium gas on-line measurement device.

[0027] In the figure, 1. Detection sealed chamber; 11. Tritium gas inlet; 12. Tritium gas outlet; 2. Vacuum coupling cavity; 21. Incident window plate; 22. Exit window plate; 23. Sealing cylinder; 3. Sample sealed chamber; 31. Bremsstrahlung target film; 32. Heating layer; 33. Sample chamber housing; 4. Detector; 5. Sealing gasket. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following are specific embodiments of the present invention in combination with the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0029] As Figure 1 shown, it includes a sealed detection sealed chamber 1, a vacuum coupling cavity 2 and a sample sealed chamber 3. The sample sealed chamber 3 is sequentially provided with a bremsstrahlung target film 31, a heating layer 32 capable of heating the bremsstrahlung target film 31 and a sample chamber housing 33 from the inside to the outside. The material of the bremsstrahlung target film 31 is a high atomic number metal with a high X-ray yield after interacting with β rays. An X-ray detector 4 is arranged in the detection sealed chamber 1;

[0030] At both ends of the sample sealing chamber 3, a tritium gas inlet 11 and a tritium gas outlet 12 are respectively arranged, and the enclosure of the vacuum coupling cavity 2 contains a component that allows X-rays to enter the detection sealing chamber 1 from the sample sealing chamber 3.

[0031] The vacuum coupling cavity 2 consists of a sealing cylinder 23, an incident window plate 21 that plugs the end of the sealing cylinder 23 close to the sample sealing chamber 3, and an exit window plate 22 that plugs the end of the sealing cylinder 23 close to the detection sealing chamber 1. Both the incident window plate 21 and the exit window plate 22 are made of materials that allow X-rays to penetrate.

[0032] The incident window plate 21 is made of aluminum or carbon.

[0033] The exit window plate 22 is beryllium.

[0034] The detector 4 is a NaI or high-purity germanium or silicon drift detector, preferably a silicon drift detector.

[0035] The material of the bremsstrahlung target film 31 is one or several of gold, tungsten, or nickel. The material of the bremsstrahlung target film 31 is a high atomic number metal that has a high X-ray yield after interacting with β-rays, preferably gold.

[0036] The heating layer 32 is a coating of zirconium metal, embedded between the bremsstrahlung target film 31 and the sample chamber housing 33. A sealing gasket 5 is arranged between the detection sealing chamber 1 and the sample sealing chamber 3.

[0037] The principle is as follows:

[0038] This solution is an on-line tritium concentration measurement device with low memory effect based on the bremsstrahlung principle (BIXS). Tritium gas enters the sample sealing chamber 3 from the tritium gas inlet 11, and after β decay, it interacts with the bremsstrahlung target film 31 on the inner wall of the sample sealing chamber 3 to generate X-rays. The X-rays pass through the incident window plate 21 and enter the vacuum coupling cavity 2, and then pass through the exit window plate 22 and enter the detection sealing chamber 1. After being detected by the detector 4, the value of the X-rays is obtained, and then through computer processing, it is converted into the corresponding value of tritium gas, thereby realizing the detection of the amount of tritium gas passing through the sample sealing chamber 3.

[0039] By designing a heating layer 32 in the sensitive volume, the residual tritium gas in the sample chamber can be removed by heating after use; the incident window plate 21 can be removed and replaced after long-term use; the non-contact measurement method can avoid the direct attachment of tritium gas to the probe head. The above measures can all improve the memory effect of the detector 4.

[0040] The present invention can greatly improve the memory effect of the detector 4 by designing a heating coating in the sensitive volume, adopting a movable sample chamber sealing window, and a non-contact measurement method, and has the characteristics of low price, accurate measurement results, high tritium gas concentration measurement, on-line measurement, and compact structure.

[0041] It should also be clarified that the vacuum coupling cavity 2 is provided to prevent tritium gas in the sample sealing chamber 3 from entering the detection sealing chamber 1; the heating layer 32 mainly heats to remove the tritium gas adsorbed on the bremsstrahlung target film 31. This is because metals have a retention effect on tritium gas. By heating, the tritium gas retained in the metal can be removed, which can eliminate the influence of non-introduced tritium gas on the detection results during the interval between two detections. So that the data obtained by the detector 4 during the next detection is the data of the rays corresponding to the tritium gas passing through the sample sealing chamber 3 at this time, rather than the rays generated by the tritium gas remaining in the sample sealing chamber 3 during the previous gas introduction; heating is conducive to gas removal, which can ensure that most of the tritium gas does not remain in the sample sealing chamber 3 before the second detection. It is common knowledge in the industry that tritium gas decay produces rays. Other details such as the specific structure of the detector 4 and the computer analysis program, which are not elaborated here, are well-known in the art and will not be elaborated further.

[0042] The detection device of this invention application adopts a movable bremsstrahlung material and an internal coating heating design, and designs appropriate dimensions through Monte Carlo, aiming to reduce the memory effect of the detection device, improve the reusability performance and broaden its application range, which is significantly different from the existing BIXS detector 4 design.

[0043] Since the incident window plate 21 needs to be replaced, in this solution, the incident window plate 21 is made of inexpensive material, and the exit window plate 22 does not need to be replaced and is made of beryllium, which is expensive.

[0044] The dimensions of each part are as follows:

[0045] The sample chamber housing 33 is cylindrical, with an inner diameter of 3 cm and a thickness of 2 cm. The inner diameter of the sealing cylinder is 3.2 cm and the height is 2.4 cm.

[0046] The heating layer 32 is a layer of zirconium metal, embedded between the sample chamber housing 33 and the bremsstrahlung target film 31, with a thickness of 0.5 cm.

[0047] The bremsstrahlung target film 31 is coated on the heating layer 32, with a thickness in the range of 0.0125 μm - 0.02 μm.

[0048] The incident window plate 21 is an aluminum plate, with a thickness of 0.015 cm and a radius of 1.5 cm. The surface is coated with 0.0125 μm thick gold and is sealed at one end of the sealing cylinder; the exit window plate is a beryllium window, with a thickness of 0.015 cm and a radius of 1.5 cm, and is sealed at the other end of the sealing cylinder.

[0049] The sealing gasket is a ring, with a thickness of 0 - 3 cm, an inner radius of 1.5 cm, and an outer radius of 5 cm.

[0050] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains may make various modifications or supplements to the described specific embodiments or use similar means for substitution, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. An on-line measuring device for high-concentration tritium gas, characterized in that, it includes a sealed detection sealing chamber (1), a vacuum coupling chamber (2) and a sample sealing chamber (3). The sample sealing chamber (3) is successively provided with a bremsstrahlung target film (31), a heating layer (32) capable of heating the bremsstrahlung target film (31), and a sample chamber housing (33) from inside to outside. The material of the bremsstrahlung target film (31) is a high-atomic-number metal with a high X-ray yield after interacting with β rays. An X-ray detector (4) is arranged in the detection sealing chamber (1); Both ends of the sample sealing chamber (3) are respectively provided with a tritium gas inlet (11) and a tritium gas outlet (12). The enclosure of the vacuum coupling chamber (2) includes a component that allows X rays to enter the detection sealing chamber (1) from the sample sealing chamber (3); The detector (4) is a NaI or high-purity germanium or silicon drift probe; the material of the bremsstrahlung target film (31) is one or several of gold, tungsten or nickel.

2. The on-line measuring device for high-concentration tritium gas according to claim 1, characterized in that, the vacuum coupling chamber (2) consists of a sealing cylinder (23), an incident window plate (21) blocking one end of the sealing cylinder (23) close to the sample sealing chamber (3), and an exit window plate (22) blocking one end of the sealing cylinder (23) close to the detection sealing chamber (1). Both the incident window plate (21) and the exit window plate (22) are made of materials allowing X rays to penetrate.

3. The on-line measuring device for high-concentration tritium gas according to claim 2, characterized in that, the incident window plate (21) is made of aluminum or carbon.

4. The on-line measuring device for high-concentration tritium gas according to claim 2, characterized in that, the exit window plate (22) is beryllium.

5. The on-line measuring device for high-concentration tritium gas according to claim 1 or 2 or 3 or 4, characterized in that, the heating layer (32) is a coating of zirconium metal, embedded between the bremsstrahlung target film (31) and the sample chamber housing (33).

6. The on-line measuring device for high-concentration tritium gas according to claim 1 or 2 or 3 or 4, characterized in that, a sealing gasket (5) is arranged between the detection sealing chamber (1) and the sample sealing chamber (3).

Images