共查询到20条相似文献,搜索用时 296 毫秒
1.
P. L. Reeder T. W. Bowyer J. I. McIntyre W. K. Pitts 《Journal of Radioanalytical and Nuclear Chemistry》2001,248(3):617-622
The International Monitoring System for the Comprehensive Nuclear-Test-Ban Treaty will include measurements of Xe fission products. Pacific Northwest National Laboratory has developed an automated system for separating Xe from air which detects Xe fission products using a beta-gamma counting system for 131mXe, 133mXe, 133gXe, and 135gXe. Betas and conversion electrons are detected in a plastic scintillation cell containing the Xe sample. Gamma and X-rays are detected in a NaI(Tl) scintillation detector which surrounds the plastic scintillator sample cell. Two-dimensional pulse-height spectra of gamma-energy versus beta-energy are obtained. The plastic scintillator spectrum in coincidence with the 31-keV X-rays from 131mXe. 133mXe, and 133gXe is a complex mixture of conversion electrons and betas. A new technique to simultaneously measure the delayed coincidence (T
1/2 = 6.27 ns) between beta-particles from 133gXe and conversion electrons depopulating the 81-keV state in 133 Cs is being developed. This technique allows separation of the 133gXe beta spectrum from the conversion electrons due to 131mXe and 133mXe and uniquely quantifies all three nuclides. 相似文献
2.
3.
This paper presents the design and characterization of a prototype compact beta–gamma radioxenon detection system that utilizes a coplanar CdZnTe crystal, an array of SiPMs, and a plastic scintillator. The detector is directly mounted on a custom PCB. The system provides the advantage of room-temperature operation, while being compact, low noise, and with simple readout electronics. Preliminary measurements using 137Cs, 135Xe, and 133/133mXe were conducted to optimize various system parameters to achieve optimal resolution of key photopeaks. The purpose of this research was to explore the potential of these radiation detection elements for use in beta–gamma coincidence applications. 相似文献
4.
Troy A. Robinson Nick R. Mann Christopher P. Oertel Matthew G. Watrous Christopher A. McGrath John P. Peterson 《Journal of Radioanalytical and Nuclear Chemistry》2017,311(3):1681-1686
Quantification of low-activity noble gases in air is typically accomplished through separation of the noble gas from air followed by radiometric assay. This work is aimed at quantification of radioactive noble gas in air without extraction. A high pressure aluminum Marinelli counting vessel was designed and fabricated that can be placed on a coaxial high purity germanium detector for gamma counting. Characterization of the performance of this Marinelli using MCNP modeling, large excesses of activity, and low-activity noble gas in air is discussed. Minimum detectable concentrations achieved during a 24 h count are: 5, 10, 50, and 1 Bq/m3 for 133Xe, 133mXe, 131mXe, and 135Xe, respectively. 相似文献
5.
G. Le Petit A. Cagniant M. Morelle P. Gross P. Achim G. Douysset T. Taffary C. Moulin 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):1159-1169
The verification regime of the comprehensive test ban treaty (CTBT) is based on a network of three different waveform technologies together with global monitoring of aerosols and noble gas in order to detect, locate and identify a nuclear weapon explosion down to 1 kt TNT equivalent. In case of a low intensity underground or underwater nuclear explosion, it appears that only radioactive gases, especially the noble gas which are difficult to contain, will allow identification of weak yield nuclear tests. Four radioactive xenon isotopes, 131mXe, 133mXe, 133Xe and 135Xe, are sufficiently produced in fission reactions and exhibit suitable half-lives and radiation emissions to be detected in atmosphere at low level far away from the release site. Four different monitoring CTBT systems, ARIX, ARSA, SAUNA, and SPALAX? have been developed in order to sample and to measure them with high sensitivity. The latest developed by the French Atomic Energy Commission (CEA) is likely to be drastically improved in detection sensitivity (especially for the metastable isotopes) through a higher sampling rate, when equipped with a new conversion electron (CE)/X-ray coincidence spectrometer. This new spectrometer is based on two combined detectors, both exhibiting very low radioactive background: a well-type NaI(Tl) detector for photon detection surrounding a gas cell equipped with two large passivated implanted planar silicon chips for electron detection. It is characterized by a low electron energy threshold and a much better energy resolution for the CE than those usually measured with the existing CTBT equipments. Furthermore, the compact geometry of the spectrometer provides high efficiency for X-ray and for CE associated to the decay modes of the four relevant radioxenons. The paper focus on the design of this new spectrometer and presents spectroscopic performances of a prototype based on recent results achieved from both radioactive xenon standards and air sample measurements. Major improvements in detection sensitivity have been reached and quantified, especially for metastable radioactive isotopes 131mXe and 133mXe with a gain in minimum detectable activity (about 2 × 10?3 Bq) relative to current CTBT SPALAX? system (air sampling frequency normalized to 8 h) of about 70 and 30 respectively. 相似文献
6.
Y. Jao W. L. Cheng H. J. Chen C. C. Shaeh C. C. Huang Y. M. Lin 《Journal of Radioanalytical and Nuclear Chemistry》1995,194(2):411-417
This study was performed under the joint TRMC/INER program for the determination of low level85Kr and133Xe concentrations in the environmental air samples. Based on cryogenic adsorption of krypton and xenon on charcoal followed by chromatographic separation from other gases, the85Kr and133Xe recovered from 200 liters of atmospheric air can be determined by either on-line gas flow proportional counter or liquid scintillation counting. The recovery yields of krypton and xenon examined by using85Kr and133Xe tracers were nearly 100%. The minimum detectable activity of85Kr and133Xe by gas flow proportional counting is about 7.40 Bq. The method is satisfactory for environmental monitoring applications under abnormal conditions of nuclear facilities. However, for lower level environmental85Kr and133Xe measurements, the liquid scintillation counting method can be applied due to their extremely low detection limits (i.e. 0.107 Bq and 0.093 Bq for85Kr and133Xe, respectively). Using this method, the measurable limits of concentrations are 0.535 Bq/m3 and 0.466 Bq/m3 for85Kr and133Xe, respectively. 相似文献
7.
Martin E. Keillor Matthew W. Cooper James C. Hayes Justin I. McIntyre 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):699-702
Pacific Northwest National Laboratory uses beta-gamma coincidence detectors in a number of xenon sampling and measurement
systems to enable simultaneous, sensitive measurements of 131Xe, 133Xe, 133mXe, and 135Xe for treaty monitoring applications. In recent years, a new style of beta–gamma detector was developed to improve upon the
detector module used in the Automated Radioxenon Sampler/Analyzer. The results of an MCNP5 Monte Carlo simulation of the new
detector cell are presented, with particular emphasis on the identification of an energy deposition sequence with the potential
to introduce significant error into the detector efficiency calibration. This sequence occurs when an 81 keV gamma from 133Xe is absorbed in an inactive region of the CsI(Na) scintillator, followed by emission of a 31 keV X-ray from cesium (or possibly
a 28.5 keV X-ray from iodine). These X-rays add excess counts into the 31 keV peak observed in the decay of 133Xe. The impact of this effect on different efficiency calibration techniques is discussed. 相似文献
8.
Weihua Zhang Pawel Mekarski Jonathan Lam Kurt Ungar Eric Pellerin 《Journal of Radioanalytical and Nuclear Chemistry》2010,285(3):475-482
In this work, a Monte Carlo (MC) simulation model is established to accurately characterize a phoswich beta-gamma coincidence detector system. This model can be easily used to predict the beta-gamma coincidence efficiencies of xenon radioisotopes at various stable xenon concentrations in the counting cell. The results demonstrate that there is a significant inverse correlation between beta-gamma coincidence efficiency and stable xenon concentration. The influence of stable xenon concentration on beta-gamma coincidence counting efficiency has been investigated for each individual xenon radioisotope. The results indicate that the effect of stable xenon concentration on beta-gamma coincidence efficiency depends on the xenon radioisotope and its decay modes. The coincidence efficiency of 133Xe with 31.0-keV X-ray decay mode is the most affected one; and then followed by 131mXe, 133Xe with 81.0-keV gamma-ray decay mode, 133mXe and finally 135Xe. The study also indicates that the gamma absorption by xenon gas plays more of a role in the decrease of beta-gamma coincidence efficiency for 133Xe and 135Xe, and that the conversion electron spectrum shifting and broadening plays more of a role in the reduction of beta-gamma coincidence efficiency for the metastable radioxenon of 131mXe and 133mXe. 相似文献
9.
D. A. Haas S. R. Biegalski K. M. Foltz Biegalski 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):677-680
The Spectral Deconvolution Analysis Tool (SDAT) software was developed to improve counting statistics and detection limits for nuclear explosion radionuclide measurements. SDAT utilizes spectral deconvolution spectroscopy techniques and can analyze both β–γ coincidence spectra for radioxenon isotopes and high-resolution HPGe spectra from aerosol monitors. The deconvolution algorithm of the SDAT requires a library of β–γ coincidence spectra of individual radioxenon isotopes to determine isotopic ratios in a sample. In order to get experimentally produced spectra of the individual isotopes, we have irradiated enriched samples of 130Xe, 132Xe, and 134Xe gas with a neutron beam from the TRIGA reactor at The University of Texas. The samples were counted in an Automated Radioxenon Sampler/Analyzer (ARSA) style β–γ coincidence detector. The spectra produced show that this method of radioxenon production yields samples with very high purity of the individual isotopes for 131mXe and 135Xe and a sample with a substantial 133mXe to 133Xe ratio. 相似文献
10.
E. Nava A. Rizzo R. Lorenzelli S. Salvi P. Bartolomei F. Padoani 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(2):1163-1167
The strategic value of noble gas capability has been recently recognized by ENEA for the acquisition of data about anthropogenic activities. Within the framework of institutional agreements, a laboratory for measurement of radioactive noble gases is under construction for environmental analysis and for monitoring studies in connection with issues related to the nuclear fuel cycle to distinguish the anthropogenic contributions to the environment. This research is intended to contribute also to the international effort to support the comprehensive nuclear-test-ban treaty verification capability. The present work summarizes the status of implementation of the noble gas laboratory at the ENEA Brasimone research centre that is located in the north-centre part of Italy by the Brasimone lake at about 850 m altitude. The radionuclides of interest are the following four xenon radioisotopes: 131mXe, 133mXe, 133Xe and 135Xe. The noble gas system under development at ENEA has three separate components: air collection (sampling and adsorption), processing (gas extraction and purification) and measurement (gamma-ray spectrometry analysis). The separation of the sampling equipment from the analysis is seen as necessary for the effectiveness of extensive sampling campaigns, as required in monitoring programs. Refurbishment is currently under way to accommodate a more sensitive acquisition system. 相似文献
11.
T. W. Bowyer K. H. Abel C. W. Hubbard M. E. Panisko P. L. Reeder R. C. Thompson R. A. Warner 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(1):109-122
Pacific Northwest National Laboratory, with guidance and support from the U.S. Department of Energy's NN-20 Comprehensive
Test Ban Treaty (CTBT) Research and Development program, has developed and demonstrated a fully automatic sampler-analyzer
(ARSA) for the collection and quantitative measurement of the four xenon radionuclides,131mXe (11.9 d),133mXe (2.19 d),133Xe (5.24 d), and135Xe (9.10 h), in the atmosphere. These radionuclides are important signatures in monitoring for compliance to a CTBT, and may
have applications in stack monitoring and other areas where xenon radionuclides are present. The activity ratios between certain
of these radionuclides permit discrimination between radioxenon originating from nuclear detonations and that from nuclear
reactor operations, nuclear fuel reprocessing, or from medical isotope production and usage. With the ARSA system, xenon is
continuously and automatically separated from the atmosphere at flow rates of about 100 lpm by sorption-bed techniques. Samples
collected in 8 hours are automatically analyzed by electron-photon coincidence spectrometry to provide detection sensitivities
as low as 100 μBq/m3 of air. This sensitivity is about 10-fold better than achieved with reported laboratory-based procedures1 for the short time collection intervals of interest. Gamma-ray energy spectra and gas analysis data are automatically collected. 相似文献
12.
N. Matsuoka N. Momoshima T. Okai Y. Takashima N. Shiraishi 《Journal of Radioanalytical and Nuclear Chemistry》1988,120(1):21-27
A simple and portable apparatus was developed for measurements of85Kr and133Xe that would be released into the atmosphere in an emergency situation of nuclear facilities. The method is based on cryogenic adsorption of these gases on charcoal followed by chromatographic separation from other gases. The85Kr and133Xe recovered from atmospheric air are determined separately by liquid scintillation counting. It takes about 1 hour for the stepwise determination of85Kr and133Xe. The atmospheric concentration of 3·10–3 Ci per m3 air (1.1·102 Bq/m3 air) is measurable for both nuclides with 20% counting error. 相似文献
13.
M. El-Garhy S. A. Marei S. El-Bayoumy R. Münze O. Hladik 《Journal of Radioanalytical and Nuclear Chemistry》1978,44(1):129-136
Uranium metal samples of large surface to volume ratios were irradiated in the presence of 1 cm3 of air. It was found that 1.708±0.015% of133Xe was released during irradiation. It was proved that this amount of133Xe is due to the decay of133I originally released. The release of133Xe was attributed to the knock-out mechanism. 相似文献
14.
Jiali Huang Yunbin Li Hao Zhang Zhen Yuan Prof. Shengchang Xiang Prof. Banglin Chen Prof. Zhangjing Zhang 《Angewandte Chemie (International ed. in English)》2023,62(52):e202315987
Hydrogen-bonded organic frameworks (HOFs) have been emerging as a new type of very promising microporous materials for gas separation and purification, but few HOFs structures constructed through hydrogen-bonding tetramers have been explored in this field. Herein, we report the first microporous HOF (termed as HOF-FJU-46) afforded by hydrogen-bonding tetramers with 4-fold interpenetrated diamond networks, which shows excellent chemical and thermal stability. What's more, activated HOF-FJU-46 exhibits the highest xenon (Xe) uptake of 2.51 mmol g−1 and xenon/krypton (Kr) selectivity of 19.9 at the ambient condition among the reported HOFs up to date. Dynamic breakthrough tests confirmed the excellent Xe/Kr separation of HOF-FJU-46a, showing high Kr productivity (110 mL g−1) and Xe uptake (1.29 mmol g−1), as well as good recyclability. The single crystal X-ray diffraction and the molecular simulations revealed that the abundant accessible aromatic and pyrazole rings in the pore channels of HOF-FJU-46a can provide the multiple strong C−H⋅⋅⋅Xe interactions with Xe atoms. 相似文献
15.
Qian Wang Shunshun Xiong Zhonghua Xiang Shuming Peng Xiaolin Wang Dapeng Cao 《中国科学:化学(英文版)》2016,59(5):643-650
We systematically investigate dynamic separation of Xe and Kr at room temperature using four representative porous materials (Cu-BTC, ZIF-8, COP-4 and activated carbon (AC)). Results indicate that among the four materials, Cu-BTC not only shows the highest retention volume per gram (Vg=788 mL g-1, which is 1.8 times of activated carbon (436 mL g-1)) under flowing condition, but also can separate 350 ppm Xe from 35 ppm Kr mixture in air with a high Xe/Kr selectivity of 8.6 at room temperature and 200 kPa, due to its suitable pore morphology, open metal sites, small side pockets in the framework. Moreover, the Cu-BTC also performs well on individual separation of Xe, Kr, CO2 from five-component gas mixture (Xe:Kr:CO2:Ar:N2=1:1:1:1:0.5, V/V) and has the longest retention time for Xe (20 min) in gas chromatographic separation, suggesting that it is a good candidate for potential applications as polymeric sieves. 相似文献
16.
S. Biegalski A. Flory D. Haas J. Ely M. Cooper 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(1):471-476
The standard deconvolution analysis tool (SDAT) was developed for analysis of radioxenon β–γ coincidence spectra measured as part of the international monitoring system as defined in the comprehensive nuclear-test-ban treaty. The SDAT software analyzes each β–γ coincidence spectrum by fitting library vectors of each radionuclide of interest: 131mXe, 133mXe, 133Xe, and 135Xe. Detector background and radon are incorporated as optional components of the sample solution. Results are reported in mBq m?3. A new graphical user interface has been developed to facilitate ease of use and improve the data visualization. Automated energy versus channel calibration algorithms were developed and implemented based on 137Cs β–γ coincidence spectra. Details on the user tool and testing are included. 相似文献
17.
S. R. Biegalski T. Saller J. Helfand K. M. F. Biegalski 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(3):663-668
As part of the Comprehensive Nuclear Test-Ban Treaty (CTBT), the International Monitoring System (IMS) was established to
monitor the world for nuclear weapon explosions. As part of this network, systems are in place to monitor the atmosphere for
radioxenon. The IMS routinely detects radioxenon from sources other than nuclear explosions. One of these radioxenon sources
is radiopharmaceutical production facilities. This is a sensitivity study on the nuclear forensic signals possible from such
facilities. A fission process model was produced to calculate the activity of 131mXe, 133mXe, 133Xe and 135Xe in the process utilized to produce 99Mo and 131I for medical applications through high enriched uranium fission. The computer model accounts for fractionation of radionuclides
within a decay chain that may result from filtering or chemical procedures. Ratios of the radioxenon isotopes are calculated
as a function of decay time after the release. The ratios are then compared to those expected from nuclear explosions. The
main conclusion from this work is that the two main factors that affect the nuclear forensic signal from radiopharmaceutical
production facilities are the sample irradiation time and the use of emission gas storage tanks. 相似文献
18.
Qingju Wang Tian Ke Lifeng Yang Zhaoqiang Zhang Xili Cui Zongbi Bao Qilong Ren Qiwei Yang Huabin Xing 《Angewandte Chemie (International ed. in English)》2020,59(9):3423-3428
The separation of xenon/krypton (Xe/Kr) mixture is of great importance to industry, but the available porous materials allow the adsorption of both, Xe and Kr only with limited selectivity. Herein we report an anion‐pillared ultramicroporous material NbOFFIVE‐2‐Cu‐i (ZU‐62) with finely tuned pore aperture size and structure flexibility, which for the first time enables an inverse size‐sieving effect in separation along with record Xe/Kr selectivity and ultrahigh Xe capacity. Evidenced by single‐crystal X‐ray diffraction, the rotation of anions and pyridine rings upon contact of larger‐size Xe atoms adapts cavities to the shape/size of Xe and allows strong host‐Xe interaction, while the smaller‐size Kr is excluded. Breakthrough experiments confirmed that ZU‐62 has a real practical potential for producing high‐purity Kr and Xe from air‐separation byproducts, showing record Kr productivity (206 mL g?1) and Xe productivity (42 mL g?1, in desorption) as well as good recyclability. 相似文献
19.
Automated separation and measurement of radioxenon for the Comprehensive Test Ban Treaty 总被引:2,自引:0,他引:2
T. W. Bowyer K. H. Abel C. W. Hubbard A. D. McKinnon M. E. Panisko R. W. Perkins P. L. Reeder R. C. Thompson R. A. Warner 《Journal of Radioanalytical and Nuclear Chemistry》1998,235(1-2):77-82
A fully automatic radioxenon sampler/analyzer (ARSA) has been developed and demonstrated for the collection and quantitative
measurement of the four xenon radionuclides,131mXe(11.9 d),133mXe(2.2 d),133Xe(5.2 d), and135Xe(9.1 hr), in the atmosphere. These radionuclides are important signatures in monitoring for compliance to a Comprehensive
Test Ban Treaty (CTBT). Activity ratios of these radionuclides permit source attribution. Xenon, continuously and automatically
separated from the atmosphere, is automatically analyzed by electron-photon coincidence spectrometry providing a lower limit
of detection of about 100 μBq/m3. The demonstrated detection limit is about 100 times better than achievable with reported laboratory-based procedures for
the short-time collection intervals of interest. 相似文献
20.
Alain Vivier Gilbert Le Petit Benoit Pigeon Xavier Blanchard 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):743-748
When a net count value is below the type 1 error critical limit it is customary to declare that the activity is “below the
detection limit”. The content of this declaration is particularly impoverished, incapable for example of discriminating between
a net measurement just below the critical limit, but positive, and a negative net measurement, two types of information that
it is legitimate and intuitive to think do not have the same weight of information. In the case of a spectral measurement
of 131mXe and 133mXe certain information is available according to the various X and gamma emissions, which might all be below their respective
critical limits. We shall see that a Bayesian probabilistic approach can be used, without considering the critical limits,
to obtain anti-correlated maximum likelihood values taking all the information into account jointly and to obtain powerful
and pertinent information in the form of the absolute probability that the sample contains 131mXe and/or 133mXe, all possible activity values combined. Conversely, of course, this is used immediately to deduce the probability that
the sample does not contain 131mXe and/or 133mXe. This information enables the customary critical limit to be ignored. 相似文献