Xenon（Xe） isotopes from nuclear test and accidents are important monitoring components of the comprehensive nuclear test ban treaty（CTBT）.An approach for the reproducible and accurate compositional analysis of Xe isotope ratios by multiple collector inductively coupled plasma mass spectrometry（MC-ICP-MS） was described in this paper.A Xe enrichment and purification platform was established to separate Xe from the collected atmosphere gas,enriching the Xe concentration and utilizing high purity argon as aerosol carrier,thus resulting in eliminating the negative influences of organic compound and particles on mass spectrometry.A relible Xe injection system was built to control the gas flow rate between the sample and the MC-ICP-MS in order to improve the stability and reproducibility of the ion-signals.Furthermore,several measures,including adsorbing Xe from the sample gas for mass spectrometry and baking the Xe introduction device for 2 hours with vaccum pumping,were taken to reduce the Xe blank.As a result,the blank signal of 129 Xe falled from 3.0 × 10 -2 V to 2.7 × 10 -3 V.Analyses were performed on a Neptune XT MC-ICP-MS,and standard sample bracketing（SSB） was involved in correcting the mass fractionation.The approach was successfully validated by the measurement of standard reference materials in 24 hours,showing that the relative uncertainties for all Xe isotope ratios were less than 0.09%（n = 7）,while the results agreed with the certificated values within uncertainty range.Especially,the relative uncertainties for 130 Xe/ 131 Xe and 132 Xe/ 131 Xe ratios were 0.007 1% and 0.006 9%,respectively.Two kinds of atmosphere gas collected at different times were analyzed and distinguished successfully by the proposed approcach.The results demonstrated that the developed technique was a precise and accurate method for Xe isotope dectection,Xe monitoring event identification and event sourcing.

BackgroundThe adsorption and separation of Xenon (Xe) / Krypton (Kr) has received increasing attention due to the concern of reprocessing radioactive isotopes of Xe and Kr from off-gas of used nuclear fuel as well as the commercial value of high purity Xe gas. At present, the separation of Xe/Kr is mainly through cryogenic distillation, which is energy and capital intensive. Porous materials such as metal-organic frameworks (MOFs) have shown the ability to selectively adsorb xenon and krypton at relative high temperature, hence are expected to replace cryogenic distillation to achieve low-cost Xe/Kr separation.PurposeThis study aims to investigate the gamma radiation stability of three MOFs (Co/DOBDC, Ni/DOBDC, Co3(HCOO)6) used for Xe and Kr adsorption separation.MethodsFirst of all, three MOFs, i.e., Co/DOBDC, Ni/DOBDC, and Co3(HCOO)6, were synthesized and activated according to the preparation methods in the published literature, and the adsorption isotherms of Xe and Kr in three MOFs samples were measured by using physical adsorption instrument with a specially designed water circulating system to maintain a constant temperature (273 K). Then, these samples were irradiated with γ-ray (1.322 MeV) at a gamma dose rate of 0~1 kGy·h-1 at ambient temperature. Samples' properties, such as Henry constant, Henry selectivity and ideal adsorbed solution theory (IAST) selectivity of Xe/Kr, before and after irradiation, were characterized by X-ray diffraction (XRD) patterns and N2 adsorption measurements. Finally, the γ-ray radiation stability of Co/DOBDC, Ni/DOBDC and Co3(HCOO)6 were studied, and the pore properties (specific surface area and pore volume) before and after irradiation were compared.Results & ConclusionsExperimental results from the observed single-component Xe and Kr isotherms, Henry's constants, Henry's constant ratio and IAST selectivity of the sample, show that Co/DOBDC and Ni/DOBDC as adsorbents have the potential to adsorb and storage high concentration Xe whilst Co3(HCOO)6 has the potential for adsorption separation of Xe and Kr in low concentration. Radiation resistance test results show that the pore properties of Co/DOBDC and Ni/DOBDC change significantly after different doses of γ-ray irradiation, and the change degree of pore properties of Co/DOBDC is large than that of Ni/DOBDC whilst the pore properties of Co3(HCOO)6 basically do not change after γ-ray radiation at a total dose of 9 kGy, indicating that Co3(HCOO)6 can be considered as a potential adsorbent for Xe/Kr separation under radioactive conditions.

为制备满足放射性测量需求的Kr气体源,需对含Kr气体中的高浓度CH4进行初步分离,本文开展了催化燃烧法分离CH4和Kr的实验研究.研究结果表明,CH4的催化燃烧转化率随CH4浓度和催化温度的升高而增加,H2对CH4催化燃烧的抑制作用随着H2浓度的升高而变大,CO对CH4催化燃烧的抑制作用随着CO浓度的升高而变小,模拟气中的CH4在适宜的催化燃烧条件下可有效去除.

对甲烷(CH4)与氪(Kr)共吸附条件下的脱附行为开展了实验研究.研究了脱附温度、升温速率和吹扫流量对CH4和Kr脱附行为的影响.实验结果表明:CH4和Kr具有相似的脱附行为,在不同脱附温度、升温速率和吹扫流量下,CH4和Kr脱附曲线的峰形和峰位基本相同;CH4和Kr脱附曲线的出峰时间随脱附温度、升温速率和瞬时吹扫流量的增加而缩短,而CH4和Kr的脱附曲线随累积吹扫流量的变化趋势在不同瞬时吹扫流量下基本相同.