Contribution to the development of atmospheric radioxenon monitoring (original) (raw)
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Measurements of ambient radioxenon levels using the automated radioxenon sampler/analyzer (ARSA)
2001
The Pacific Northwest National Laboratory has developed an Automated Radioxenon Sampler/Analyzer (ARSA) in support of the Comprehensive Nuclear-Test-Ban-Treaty (CTBT) to measure four radioxenon isotopes: 131m Xe, 133m Xe, 133g Xe, and 135g Xe. This system uses a beta-gamma coincidence counting detector to produce two-dimensional plots of gamma-energy versus beta-energy. Betas and conversion electrons (CE) are detected in a cylindrical plastic scintillation cell and gamma and X-rays are detected in a surrounding NaI(Tl) scintillation detector. The ARSA has been field tested at several locations to measure the radioxenon concentrations. Most recently it has been deployed at the Institut für Atmosphärische Radioaktivität in Freiburg, Germany. During the first 4 months of 2000 the measured 133 Xe concentrations have varied between 0.0±0.1 and 110±10 mBq/m 3 air. The longer lived 131m Xe (T 1/2 = 11.9 d) and short lived 135 Xe (T 1/2 = 9.1 h) have also been detected in small quantities, while 133m Xe concentrations have been consistent with zero. Minimum detectable concentration (MDC) calculations for 133g Xe fell well below the 1 mBq per standard-cubic-meter of air requirement adopted by the CTBT Preparatory Commission. 1 A description of the radioxenon detector, the concentration and MDC calculations and preliminary results of the field test in Germany are presented.
Intercomparison experiments of systems for the measurement of xenon radionuclides in the atmosphere
Applied Radiation and Isotopes, 2004
Radioactive xenon monitoring is one of the main technologies used for the detection of underground nuclear explosions. Precise and reliable measurements of 131m Xe, 133g Xe, 133m Xe, and 135g Xe are required as part of the International Monitoring System for compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). For the first time, simultaneous testing of four highly sensitive and automated fieldable radioxenon measurement systems has been performed and compared to established laboratory techniques. In addition to an intercomparison of radioxenon monitoring equipment of different design, this paper also presents a set of more than 2000 measurements of activity concentrations of radioactive xenon made in the city of Freiburg, Germany in 2000. The intercomparison experiment showed, that the results from the newly developed systems agree with each other and the equipment fulfills the fundamental requirements for their use in the verification regime of the CTBT. For 24-h measurements, concentrations as low as 0.1 mBq m À3 were measured for atmospheric samples ranging in size from 10 to 80 m 3 . The 133 Xe activity concentrations detected in the ambient air ranged from below 1 mBq m À3 to above 100 mBq m À3 .
The Automated Radioxenon Analyzer/Sampler (ARSA) has been deployed at several locations throughout the world: Richland, WA; New York City, NY; Charlottesville, VA; Freiburg, Germany; and, most recently, Guangzhou, China. In each of these locations, the ARSA has measured varying concentrations of 131m Xe, 133 Xe, 133m Xe, and 135 Xe. These concentrations of radioxenon come from a variety of sources such as nuclear reactors, medical hospitals, and nuclear fuel reprocessing; the concentrations vary by location. This makes it necessary to utilize the isotope ratios as well as their concentrations to differentiate ambient radioxenon emissions from those released by clandestine underground nuclear explosions. High concentrations and multiple isotope identification within a single sample are good measures of potentially suspect radioxenon emissions. Utilizing the ratios of the concentrations of 135 Xe to 133 Xe and 133 Xe to 133m Xe enhances the separation of the more mundane emissions from clandestine underground nuclear detonations. This paper presents concentration data collected from each of the sites and explores the ability of ratios to discriminate between reactor effluents and underground nuclear tests. Analyses to date indicate that concentration levels, multiple radioxenon isotopes in a single sample, the presence of 133m Xe and several isotopic ratios will all be good indicators of clandestine underground nuclear explosions and the combination of two or more of these measures will provide strong evidence of such activities.
SAUNA—a system for automatic sampling, processing, and analysis of radioactive xenon
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2003
A system for automatic sampling, processing, and analysis of atmospheric radioxenon has been developed. From an air sample of about 7 m 3 collected during 12 h; 0:5 cm 3 of xenon is extracted, and the atmospheric activities from the four xenon isotopes 133 Xe; 135 Xe; 131m Xe; and 133m Xe are determined with a beta-gamma coincidence technique. The collection is performed using activated charcoal and molecular sieves at ambient temperature. The sample preparation and quantification are performed using preparative gas chromatography. The system was tested under routine conditions for a 5-month period, with average minimum detectable concentrations below 1 mBq=m 3 for all four isotopes. r
A prototype detection system for atmospheric monitoring of xenon radioisotopes
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2018
The design of a radioxenon detection system utilizing a CdZeTe crystal and a plastic scintillator coupled to an array of SiPMs to conduct beta-gamma coincidence detection for atmospheric radioxenon monitoring, as well as the measurement of 135 Xe and 133/133m Xe, have been detailed previously. This paper presents recent measurements of 133/133m Xe and 131m Xe and the observation of conversion electrons in their coincidence spectra, as well as a 48-hour background measurement to calculate the Minimum Detectable Concentration (MDC) of radioxenon isotopes in the system. The identification of Regions of Interest (ROIs) in the coincidence spectra yielded from the radioxenon measurements, and the subsequent calculation of the MDCs of the system for 135 Xe, 133/133m Xe, and 131m Xe, are also discussed. Calculated MDCs show that the detection system preforms respectably when compared to other state of the art radioxenon detection systems and achieved an MDC of less than 1 mBq/m 3 for 131m Xe, 133 Xe, and 133m Xe, in accordance with limits set by the Comprehensive Nuclear-Test-Ban Treaty (CTBTO). The system also provides the advantage of room temperature operation, compactness, low noise operation and having simple readout electronics.
Environmental applications of stable xenon and radioxenon monitoring
Journal of Radioanalytical and Nuclear Chemistry, 2008
Characterization of transuranic waste is needed for decisions about waste site remediation. Soil-gas sampling for xenon isotopes can be used to define the locations of spent fuel and transuranic waste. Radioxenon in the subsurface is characteristic of transuranic waste and can be measured with extreme sensitivity using large-volume soil-gas samples. Measurements at the Hanford Site showed 133 Xe and 135 Xe levels indicative of 240 Pu spontaneous fission. Stable xenon isotopic ratios from fission are distinct from atmospheric xenon background. Neutron capture by 135 Xe produces an excess of 136 Xe in reactor-produced xenon, providing a means of distinguishing spent fuel from separated transuranic material.
Journal of Radioanalytical and Nuclear Chemistry, 2013
The Comprehensive Nuclear-Test-Ban Treaty (CTBT) specifies that radioxenon measurements should be performed at 40 or more stations worldwide within the International Monitoring System (IMS). Measuring radioxenon is one of the principle techniques to detect underground nuclear explosions. Specifically, presence and ratios of different radioxenon isotopes allows determining whether a detection event under consideration originated from a nuclear explosion or a civilian source. However, radioxenon monitoring on a global scale is a novel technology and the global civil background must be characterized sufficiently. This paper lays out a study, based on several unique measurement campaigns, of the worldwide concentrations and sources of verification relevant xenon isotopes. It complements the experience already gathered with radioxenon measurements within the CTBT IMS programme and focuses on locations in Belgium, Germany, Kuwait, Thailand and South Africa where very little information was available on ambient xenon levels or interesting sites offered opportunities to learn more about emissions from known sources. The findings corroborate the hypothesis that a few major radioxenon sources contribute in great part to the global radioxenon background. Additionally, the existence of independent sources of 131m Xe (the daughter of 131 I) has been demonstrated, which has some potential to bias the isotopic signature of signals from nuclear explosions.
Environmental Radioxenon Levels in Europe: a Comprehensive Overview
Pure and Applied Geophysics, 2010
Activity concentration data from ambient radioxenon measurements in ground level air, which were carried out in Europe in the framework of the International Noble Gas Experiment (INGE) in support of the development and build-up of a radioxenon monitoring network for the Comprehensive Nuclear-Test-Ban Treaty verification regime are presented and discussed. Six measurement stations provided data from 5 years of measurements performed between 2003 and 2008: Longyearbyen (Spitsbergen, Norway), Stockholm (Sweden), Dubna (Russian Federation), Schauinsland Mountain (Germany), Bruyères-le-Châtel and Marseille (both France). The noble gas systems used within the INGE are designed to continuously measure low concentrations of the four radioxenon isotopes which are most relevant for detection of nuclear explosions: 131mXe, 133mXe, 133Xe and 135Xe with a time resolution less than or equal to 24 h and a minimum detectable concentration of 133Xe less than 1 mBq/m3. This European cluster of six stations is particularly interesting because it is highly influenced by a high density of nuclear power reactors and some radiopharmaceutical production facilities. The activity concentrations at the European INGE stations are studied to characterise the influence of civilian releases, to be able to distinguish them from possible nuclear explosions. It was found that the mean activity concentration of the most frequently detected isotope, 133Xe, was 5–20 mBq/m3 within Central Europe where most nuclear installations are situated (Bruyères-le-Châtel and Schauinsland), 1.4–2.4 mBq/m3 just outside that region (Stockholm, Dubna and Marseille) and 0.2 mBq/m3 in the remote polar station of Spitsbergen. No seasonal trends could be observed from the data. Two interesting events have been examined and their source regions have been identified using atmospheric backtracking methods that deploy Lagrangian particle dispersion modelling and inversion techniques. The results are consistent with known releases of a radiopharmaceutical facility.
Global Radioxenon Emission Inventory from Nuclear Research Reactors
Pure and Applied Geophysics, 2021
To monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT), the International Monitoring System (IMS) is being established which will include 40 sensor systems for atmospheric xenon radioactivity. Radioactive isotopes of the noble gas xenon provide the most likely observable radioactive signatures of underground nuclear explosions. These isotopes are frequently detected by IMS noble gas systems as a result of normal operational releases from different types of nuclear facilities including nuclear power plants (NPPs), medical isotope production facilities (MIPFs), and nuclear research reactors (NRRs). Improved knowledge of the contribution of different emission sources on IMS observations strengthens the screening of radioxenon measurements to exclude observations not relevant to emissions from a nuclear explosion. The contribution of NPPs and MIPFs to the global radioxenon emission inventory is fairly well understood. NRRs have yet to be systematically assessed. Thi...
Environmental application of stable xenon and radioxenonmonitoring
Journal of Radioanalytical and Nuclear Chemistry, 2006
Characterization of transuranic waste is needed to makedecisions about waste site remediation. Soil-gas sampling for xenonisotopes can be used to define the locations of spent fuel andtransuranic wastes. Radioxenon in the subsurface is characteristic oftransuranic waste and can be measured with extreme sensitivity usinglarge-volume soilgas samples. Measurements at the Hanford Site showed133Xe and 135Xe levels indicative of 240Pu spontaneous fission.