1,720,974 research outputs found
Improving the noble gas detection capability for the verification of the Comprehensive Nuclear-Test-Ban Treaty
No full textThe Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear weapon tests on Earth. For its verification, a worldwide network of sensors, called the International Monitoring System (IMS), is being deployed (90% completed in 2024) to continuously monitor the Earth. One of the methods used in the IMS to verify compliance with the CTBT is to monitor the atmosphere for radioactive traces released by a nuclear weapon test. For underground nuclear weapon tests, noble gases are the most likely radioactive signal to seep out of the test cavity. Accordingly, the IMS contains sensors to monitor the atmosphere for traces of radioactive xenon (radioxenon) isotopes, which have a high fission yield and well-suited half-lives. Next to continuously monitoring the Earth, the CTBT foresees On-Site Inspection (OSI) as an ultimate verification measure when a nuclear weapon test is suspected. One of the techniques currently developed for OSI is the measurement of 37Ar in atmospheric and soil air at a suspected test site.
The verification of the CTBT by radioxenon monitoring in the IMS is facing a major issue: the presence of a significant background from nuclear installations. Different approaches are considered to minimize the impact of the radioxenon background on CTBT verification, amongst which: i) improve the discrimination capability of the monitoring sensors and ii) reduce the radioxenon emissions of nuclear installations. Concerning the discrimination capability of the sensors, nuclear weapon tests can be discriminated from the civilian background based on the Xe isotopic composition and backward atmospheric transport modelling of the air sample. For backward atmospheric transport modelling, shorter sampling durations would allow to better identify the origin of radioxenon observations and increase the discrimination capability. Regarding emissions, most of the background arises from a few installations, extracting radioactive isotopes from irradiated uranium targets, distributed worldwide. For OSI, the current processes for sampling and measuring 37Ar are complex (multiple adsorbents) and energy intensive (cryogenic temperatures). Research is required on simplified and less energy demanding processes.
In this work, we investigate the use of new porous adsorbents and new process designs to: i) improve the discrimination capability of radioxenon monitoring systems, ii) simplify 37Ar sampling and iii) reduce radioxenon emissions at nuclear installations. We demonstrate that silver-exchanged zeolites or alike (AgZs), in particular Ag-ETS-10 and Ag-ZSM-5, are much more volume-efficient and selective for collecting and separating Xe from dry air than any other porous material currently reported. Our results reveal that AgZs have the potential to simplify significantly radioxenon monitoring systems and could thus reduce the sampling duration for a better discrimination capability. Similarly, we show that both adsorbents are also much more volume-efficient than activated carbon for trapping radioxenon in nuclear installations. They are thus also promising candidates to reduce radioxenon emissions by replacing the current activated carbon-based mitigation systems. In addition, we establish that both adsorbents can withstand radiation levels up to 100 MGy and at least 40 thermal regeneration cycles without significant loss in Xe adsorption performance. Finally, we show that Ag-ETS-10 can be used as a single adsorbent, operating at room temperature, to separate Ar from air. However, to reach a sufficiently high Ar yield for OSI measurement, the separation would need to be performed at a lower temperature. Our results indicate that operating the Ag-ETS-10 at -25°C would improve the Ar separation and could thus be the way forward to simplify, by using a single adsorbent and working well above cryogenic temperatures, the current Ar separation process for 37Ar measurements during OSI
Improving the noble gas detection capability for the verification of the Comprehensive Nuclear-Test-Ban Treaty
No full textThe Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear weapon tests on Earth. For its verification, a worldwide network of sensors, called the International Monitoring System (IMS), is being deployed (90% completed in 2024) to continuously monitor the Earth. One of the methods used in the IMS to verify compliance with the CTBT is to monitor the atmosphere for radioactive traces released by a nuclear weapon test. For underground nuclear weapon tests, noble gases are the most likely radioactive signal to seep out of the test cavity. Accordingly, the IMS contains sensors to monitor the atmosphere for traces of radioactive xenon (radioxenon) isotopes, which have a high fission yield and well-suited half-lives. Next to continuously monitoring the Earth, the CTBT foresees On-Site Inspection (OSI) as an ultimate verification measure when a nuclear weapon test is suspected. One of the techniques currently developed for OSI is the measurement of 37Ar in atmospheric and soil air at a suspected test site.
The verification of the CTBT by radioxenon monitoring in the IMS is facing a major issue: the presence of a significant background from nuclear installations. Different approaches are considered to minimize the impact of the radioxenon background on CTBT verification, amongst which: i) improve the discrimination capability of the monitoring sensors and ii) reduce the radioxenon emissions of nuclear installations. Concerning the discrimination capability of the sensors, nuclear weapon tests can be discriminated from the civilian background based on the Xe isotopic composition and backward atmospheric transport modelling of the air sample. For backward atmospheric transport modelling, shorter sampling durations would allow to better identify the origin of radioxenon observations and increase the discrimination capability. Regarding emissions, most of the background arises from a few installations, extracting radioactive isotopes from irradiated uranium targets, distributed worldwide. For OSI, the current processes for sampling and measuring 37Ar are complex (multiple adsorbents) and energy intensive (cryogenic temperatures). Research is required on simplified and less energy demanding processes.
In this work, we investigate the use of new porous adsorbents and new process designs to: i) improve the discrimination capability of radioxenon monitoring systems, ii) simplify 37Ar sampling and iii) reduce radioxenon emissions at nuclear installations. We demonstrate that silver-exchanged zeolites or alike (AgZs), in particular Ag-ETS-10 and Ag-ZSM-5, are much more volume-efficient and selective for collecting and separating Xe from dry air than any other porous material currently reported. Our results reveal that AgZs have the potential to simplify significantly radioxenon monitoring systems and could thus reduce the sampling duration for a better discrimination capability. Similarly, we show that both adsorbents are also much more volume-efficient than activated carbon for trapping radioxenon in nuclear installations. They are thus also promising candidates to reduce radioxenon emissions by replacing the current activated carbon-based mitigation systems. In addition, we establish that both adsorbents can withstand radiation levels up to 100 MGy and at least 40 thermal regeneration cycles without significant loss in Xe adsorption performance. Finally, we show that Ag-ETS-10 can be used as a single adsorbent, operating at room temperature, to separate Ar from air. However, to reach a sufficiently high Ar yield for OSI measurement, the separation would need to be performed at a lower temperature. Our results indicate that operating the Ag-ETS-10 at -25°C would improve the Ar separation and could thus be the way forward to simplify, by using a single adsorbent and working well above cryogenic temperatures, the current Ar separation process for 37Ar measurements during OSI
Vacuum pressure swing adsorption-based Ar separation from air on a single adsorbent
No full textDue to their inert nature, radioactive noble gases are key for verifying the nuclear character of underground explosions. 37Ar sampling and detection is considered as an important technique for on-site inspections (OSI) for CTBT verification. Compared to radioxenon, 37Ar has a longer half-life and remains detectable for a longer time. For the detection of 37Ar, high purity Ar needs to be recovered from subsoil or atmospheric air. Less energy intensive alternatives, than current systems using at least a cryocooled adsorbent, for recovering Ar from air are sought for. In this context, research on Ar separation in adsorbents operating near room temperature for OSI is led by CTBTO. SCK CEN was contracted to verify the potential of a silver-exchanged molecular sieve (Ag ETS 10) for separating Ar from air by Vacuum Pressure Swing Adsorption (VPSA) at room temperature. In this project, we confirmed for instance its preferential adsorption of Ar over O2, with a 1.4 selectivity, through air-breakthrough measurements. Ar purity against yield was determined from separations in VPSA mode. Additional research was performed outside the project to investigate Ar separation in a larger set of conditions. These results will be discussed in the framework of Ar separation for CTBT verification
Investigation of xenon adsorption in three types of porous materials
No full textThe recovery of xenon from atmospheric air, based on highly efficient and selective adsorption, could replace the current cost-intensive cryogenic distillation generally used for xenon production. In addition, adsorption improvements for the measurement of ultra-low levels of radioactive xenon in the atmosphere could increase the capability of the verification system for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). In the same context, enhanced radioactive xenon trapping systems at civilian nuclear installations could also improve the verification capability, as this would further reduce the atmospheric radioactive xenon background.
Activated carbon has been used for more than 60 years in the nuclear industry to recover radioactive xenon from gaseous effluents. About 20 years ago, researchers have demonstrated that some silver-exchanged zeolites had a higher Xe adsorption capacity at low Xe-partial pressures. The lack of knowledge on the durability of these zeolites did not yet allow their use with highly radioactive gas streams. More recently, some metal-organic frameworks have been demonstrated to be quite selective for xenon over other gas components, which could open a new opportunity in these fields. Ideally, adsorbents that are capable of trapping large amounts of xenon whilst being highly selective for xenon are looked for. In addition, these adsorbents should be durable against multiple temperature swing adsorption cycles as well as against severe irradiation.
In this poster, the measurement of xenon breakthrough curves over a range of conditions, used for the investigation of the Xe adsorption properties, will be presented and the results obtained on the three types of adsorbents will be discussed. Other characterization techniques (e.g. liquid nitrogen adsorption and thermal gravimetric analysis) used to support such research, through the identification of promising materials and to investigate their durability, will be addressed
Experimental investigation of adsorption materials for the mitigation of civilian radioxenon releases
No full textExperimental investigation of adsorption materials for the mitigation of civilian radioxenon releases
No full text
Investigation of xenon adsorption in three types of porous materials
No full textThe recovery of xenon from atmospheric air, based on highly efficient and selective adsorption, could replace the current cost-intensive cryogenic distillation generally used for xenon production. In addition, adsorption improvements for the measurement of ultra-low levels of radioactive xenon in the atmosphere could increase the capability of the verification system for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). In the same context, enhanced radioactive xenon trapping systems at civilian nuclear installations could also improve the verification capability, as this would further reduce the atmospheric radioactive xenon background.
Activated carbon has been used for more than 60 years in the nuclear industry to recover radioactive xenon from gaseous effluents. About 20 years ago, researchers have demonstrated that some silver-exchanged zeolites had a higher Xe adsorption capacity at low Xe-partial pressures. The lack of knowledge on the durability of these zeolites did not yet allow their use with highly radioactive gas streams. More recently, some metal-organic frameworks have been demonstrated to be quite selective for xenon over other gas components, which could open a new opportunity in these fields. Ideally, adsorbents that are capable of trapping large amounts of xenon whilst being highly selective for xenon are looked for. In addition, these adsorbents should be durable against multiple temperature swing adsorption cycles as well as against severe irradiation.
In this poster, the measurement of xenon breakthrough curves over a range of conditions, used for the investigation of the Xe adsorption properties, will be presented and the results obtained on the three types of adsorbents will be discussed. Other characterization techniques (e.g. liquid nitrogen adsorption and thermal gravimetric analysis) used to support such research, through the identification of promising materials and to investigate their durability, will be addressed
Application of silver-exchanged zeolite for the mitigation of civilian radioxenon releases
No full textThe radioxenon releases from civilian nuclear installations are significantly affecting the International Monitoring System (IMS), which is being deployed for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). These civilian radioxenon releases are disturbing and limiting the detection capability of the noble gas component of the IMS for CTBT-related events. Substantial reductions of civilian radioxenon releases would significantly improve the detection capability of the noble gas component of the IMS.
For a long time, activated carbon has been the standard for trapping radioxenon from gaseous effluents in the nuclear industry. In this work, we demonstrate the potential of silver-exchanged zeolites for replacing activated carbon and providing a higher radioxenon trapping efficiency. For this purpose, three activated carbons and five silver-exchanged zeolites are compared through their Xe adsorption properties in helium - and nitrogen bulk gas. The effect of moisture in the inlet gas stream on the Xe adsorption properties is considered as well. The most promising silver-exchanged zeolite is then further investigated for its practical application by studying the effect of column geometry, flow rate and temperature. Finally, the durability of this adsorbent against irradiation and desorption/adsorption cycles is examined for its application in the nuclear industry.
Recently in the literature, some metal-organic frameworks have been demonstrated to be quite selective for the adsorption of xenon over other gas components. The Xe adsorption properties measured on two metal-organic framework materials will be presented to put their potential application for radioxenon mitigation into perspective
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