Radioactive isotopes of xenon are produced in nuclear facilities,and must be trapped before released into the atmosphere.Study on the adsorption behavior of Xe isotopes in air or other gaseous medium is of great importance.For the perspective of engineering application,direct adsorption of multi-component gas at room temperature using activated carbon was studied.The comparison between multi-stage and single-stage carbon column adsorption was carried out, and the effects of condition parameters including carbon consumption were investigated.Experimental results show that single-stage carbon column is easier to be achieved in engineering application as compared with the way of multi-stage adsorbing column.For single-stage carbon column,the adsorbing efficiency of Xe reaches 90% with a gas flow velocity of 0.33 cm/s,and the resistance from the carbon bed is negli-gible in a certain flow velocity range (0.02-1.2 cm/s).

Monitoring of radioactive xenon in the atmosphere is greatly important in identifi-cation of nuclear activities.Prior atmospheric xenon samplers were usually operated manual-lywhich is costing and laboring.We developed an electric control system for a xenon sam-pler which enables 24-hour continuous sampling.The system is based on an industrial per-sonal computer and a programmable logic controlPLCsystem.The upper computer was designed with Kingview6.3 to communicate with various lower devicesincluding tempera-ture controllerswhich are connected through RS-485 busto provide real-time thermostat temperature informationand the lower PLCwhich is linked through Ethernetto monitor the state of each valve switch and to collect the pressure and flow data of the xenon sampler. We formulated a control program for the lower PLC according to the sampling proceduresand achieved the control of all kinds of instruments and analog data collection.The system was designed to have the functions of automatically alarmingautomatically data recordingreporting and queryingcontinuously samplingmanual/automatic controland has been successfully used in an atmospheric xenon sampler system.

为满足大气放射性核素监测的需求,利用氙(Xe)与二氧化碳(CO2)、氡(Rn)等组分在活性炭吸附柱内脱附行为的差异,采用多级活性炭吸附柱吸附脱附的方法,对大气环境中的Xe(体积分数8.7×10 8)进行浓缩纯化,得到高浓度的Xe样品.研究了空气中的Xe、CO2及Rn等组分在多级活性炭吸附柱上的脱附曲线,选择Xe的脱附时段向下一级吸附柱转移吸附,对Xe进行逐级浓缩纯化.样品中Xe富集倍数可达105～106,Rn去污系数大于10 5,CO2体积分数低于4×10 5.此研究结果对于实现多组分混合气体中某一特定低含量组分的浓缩、纯化具有普遍指导意义.

在发生裂变反应的核设施中会产生放射性稀有气体氙(Xe)等.为保证反应堆的正常运行,须经过净化处理去除Xe等后才能排放,因此需滞留收集Xe等放射性气体.本文针对市售的5种多孔材料,包括颗粒状活性炭、分子筛和活性炭纤维3类,以材料的比表面积、孔容积为指标,结合Xe静态吸附容量,优选出性能较优的Xe吸附剂.研究了进气压力和吸附柱长径比对活性炭吸附Xe的影响,结果显示,活性炭吸附柱长径比为17∶1时,吸附性能最好.

Aerosol radionuclides （131I, 134Cs, 137Cs） and gaseous radioactive xenon （133Xe） were monitored at Xi’an, China following the accident at the Fukushima nuclear power plant in March 2011. The additional annual effective dose attributable to the Fukushima emissions was much lower than the public annual effective dose from natural radiation, according to Chinese national standards. The monitoring results were compared with data from other countries as well as with the radionuclide concentrations observed in Xi’an after the Chernobyl nuclear accident in 1986. Possible transport pathways of the released radionuclides from Fukushima to Xi’an were investigated. The occurrence of an anticyclone in the Pacific Ocean region and the extended period over which the radionuclides were released made the determination transport pathways complex, but divergence in the plume and easterly flow evidently brought the initial suite of radionuclides to Xi’an.

The absorption and separation method of Xe and Kr gas by active carbon was investigated.A standard mixture of Xe and Kr flowed through the active carbon column to be absorbed and enriched at low temperature(-78 ℃).The absorbed Xe and Kr were then deabsorbed from the carbon column separately.The analysis of the experimental data shows that the recoveries of Xe and Kr are greater than 90%.It can be concluded that the decontamination coefficient for Xe from Kr environment is above 104,while the decontamination coefficient for Kr from Xe is no less than 103.

An HPGe gamma-ray spectrometry system for radioxenon isotopes detection has been developed. The system was comprised of two low-energy planar HPGe detectors that were horizontally and oppositely placed, and a gas source cell made of carbon fiber in both sides was used. The spectra obtained simultaneously by the two HPGe detectors were analyzed by summing spectrum method. After the radioactive concentration of 133Xe was determined with three internal gas proportional counters, the efficiency of 81keV gamma-ray for 133Xe was calibrated to be 0.50 (1), and the Minimum Detectable Activity (MDA) for 133Xe detection was determined to be 10mBq during 1 day measurement time. Finally, the system was applied in atmospheric 133Xe monitoring at Xi'an of China after the Fukushima nuclear accident.

The retention time of Xe and Kr can be varied by changing the flow rate of carrier gas and temperature of the chromatography column packed with 5A molecular screen.It can be used for separating the noble gases.Test results show that an enhanced decontamination factor can be observed by extending the interval between retention times of Kr and Xe.Over 95% of the Kr and Xe can be absorbed by active carbon at –80oC.

In order to monitor radioactive krypton distribution in the environment,active charcoal is used to enrich krypton before the sample can be submitted to further laboratory analysis.The importance and method of krypton enrichment were presented.The absorption behavior of krypton by charcoal was analyzed.The experimental setup was designed to investigate effects of working temperature,linear velocities,partial-pressure of krypton on the enrichment of krypton by charcoal.The micro-structure parameters of the absorbing material to characterize its absorbing property was used,and the experimental data with theoretical analysis to conclude that for CF-1450 was fitted.The saturation absorption capacity at 191 K is 32.9 mL/g.

Radionuclide verification is one of four international monitoring systems that were stipulated by the comprehensive nuclear test ban treaty.The radioactive noble gas xenon is a gaseous fission product of nuclear fuels.The radionuclides of Xe are characteristic nuclides of nuclear explosion.A nuclear event that violates the treaty may be found by monitoring the variation of radioxenon(mainly ~(133)Xe~(m),~(133)Xe,~(135)Xe and ~(131)Xe~(m)) in global atmosphere through a global network of eighty stations of the international monitoring system(IMS).Therefore,it is necessary to research the sampling technology for xenon isotopes.The possibilities for sampling technology(including condensation and concentration of xenon isotopes) is explored from pre-separating and pre-condensing(microxenon) sample with FNQ-01 gas condenser experimental platform.The collecting efficiencies of microxenon influenced by the different condensing conditions were studied on this experimental platform.The best condensing conditions optimized with the orthogonal design method are showed respectively as follows: xenon concentration in sample 1.046×10~(-3),condensing temperature-198 ℃,gas flow rate 0.3 L/min,gas inlet pressure 55 kPa and evaporating temperature-50 ℃.The average collecting efficiency under these optimized conditions is 73%.Furthermore,the influences of different admitting methods to xenon collecting efficiency and condensation were discussed.

An experimental sampler for rare gases (ESRG) which can collect radioxenon isotopes from atmosphere under normal temperature and low temperature is installed and studied. Its sampling efficiency is calibrated with ICP-MS (Inductively Coupled Plasma-Mass Spectrum) through analyzing the ~129Xe in the off-gas of ESRG. The main experimental results show that the sampling efficiency to xenon isotopes in ambient air is up to 40% when the adsorbent is effectually regenerated.

研究了在空气和含NO2气氛中不同温度下对GF/Cu皮芯复合导电纤维材料加速老化,力学性能、电学性能的影响,以及空气中高低温冲击导致其力学性能变化的规律.给出了导电纤维材料在不同环境中的氧化动力学曲线并分别计算了氧化激活能,推算出室温(25℃)条件下不同气氛中的储存氧化半衰期分别为:13.55年(空气气氛)、216.29天(氧化性气氛NO2:空气＝1:1)和374.75天(氧化性气氛NO2:空气＝1:2).

The static adsorption isotherms and adsorption rates of krypton and xenon at 201 K on viscose-based activated carbon fibres(VACF),pitch-based ACF(PACF),and granular activated carbon (GAC) are measured on a Micromeritics ASAP 2010M specific surface area and pore size distribution instrument by changing working gas of the instrument from N_2 to krypton or xenon. The results show that VACF has the same equilibrium adsorption capacity, but different adsorption rates for krypton and xenon.Because of the difference in their adsorption rates,sampling or concentration of krypton and xenon with VACF may lead to an alternation in their molar ratios.