微型气相色谱法测定H2中杂质气体

为了满足氢同位素分离系统、 等离子体排灰气处理系统和贮存与供给工艺系统对进气品质的要求,需建立准确、快速、高精度的杂质气体分析方法。针对H₂中体积分数为10^-2~10^-3的气体组分He、Ne、N₂、Ar、CH₄、CO和CO₂,本研究首先采用配有1个Pora PLOT U通道和1个MS5- 通道的微型气相色谱仪,以H2为载气,建立H2中杂质气体的分析方法并优化测量参数。结果表明,杂质气体组分测量精密度优于0.2%,-0.5%<测量相对误差<0.5%,分离度>1.5,检出限为1.3×10^-6~8.5×10^-6,定量限为4.5×10^-6~36.3×10^-6,分析时间<2.5 min。在优化后的测量条件下探讨分别以He、Ne和Ar为载气测量H2中杂质气体的可行性,得到了标准气体色谱图。所建立方法能够满足工艺系统对进气的分析要求,并可拓展应用到其他氢同位素气体的杂质组分分析。     

复杂混合气体组分在低温活性炭表面的吸附特性

为实现大体积气体中微量放射性气体Kr、Xe同位素的测量，须将混合气体进行浓集并将目标气体吸附于10 mL左右的活性炭源盒中。本实验对混合气体中各组分在活性炭分离柱上的吸附性能进行研究，建立了通过去除其他杂质气体、浓集大体积气体制备放射性Kr和Xe活度源的方法。根据反应堆流出气体和核爆可能生成的气体组分，配制了模拟气体，使用活化的4A分子筛对其中的水和CO₂进行模拟去除，获得了流程中去除水和CO₂的实验条件；选择5个低温点(273、264、255、246、238 K)，在低温活性炭柱上对H₂、CO、CH₄、Kr和Xe的吸附特性进行研究，测定了各气体在不同温度下的吸附穿透曲线。结果表明，室温下4A分子筛对水和CO₂有较好的吸附效果。低温下，H₂、CO不易在活性炭表面吸附；CH₄、Kr吸附性质相似；Xe吸附能力较强。低温下难以去除的CH₄可在高温下氧化去除。因此，可根据混合气体中各组分性质的不同实现杂质气体的去除和目标气体Kr、Xe的回收测量。     

氦中痕量H2、D2组分的高精度气相色谱分析

为满足聚变堆氘氚燃料循环工艺气体中痕量氢同位素组分的特殊检测分析要求,需建立快速、高精度的在线分析方法。针对氦中痕量H₂、D₂组分,本工作以高纯氦为载气,在液氮温度下,使用自制改性Al₂O₃毛细管柱进行分离,放电氦离子化检测器进行检测。结果显示,氢氘组分的检测限不高于1×10^-8,保留时间不高于180 s,氢氘组分色谱峰峰面积响应值的相对标准偏差不大于1.0%,分离度大于1.0。本方法具有分析灵敏、快速的优点,为聚变堆包层在氘氚燃料注入系统和氢同位素分离系统中微量氚的安全分析与精确计量提供了一种有效的测量技术。     

氖中微量组分气相色谱测量分析方法与验证

为测量聚变堆固态氚增殖剂堆内辐照氚增殖剂的产氚速率，除用常规电离室之外，本研究建立了Ne载气的高精度气相色谱在线检测分析方法，通过测量产氚回路中的氦产生量，验证系统中产生的氚量，从而为聚变堆固态包层产氚包层增殖剂材料辐照产氚性能提供一种新的产氚速率测量验证方法。本工作通过研制含有三个检测器、五个色谱柱的气相色谱分析系统，建立了Ne中微量⁴He、H₂及杂质组分的色谱检测分析方法，并完成了实时在线检测的验证实验。结果表明，研发的色谱分析系统可实现高纯Ne中4He、H₂及杂质组分的检测分析，H₂、⁴He检测限可分别达到1.0×10^-6、5.9×10^-6，各组分含量及峰面积的相对标准偏差(sr)均小于5.0%(n=6)，线性相关系数(r²)均大于0.99，说明检测方法重复性好。根据Ne中多组分气体的在线检测验证实验可知，单时段和多时段内的测量重复性均较好，可为辐照产氚考核系统中的产氚速率验证提供分析手段，进而为正式入堆得到辐照数据和氚衡算提供技术支持。     

氘气中氢同位素的低温气相色谱法测定

针对高纯氘气中H₂、HD与D₂等氢同位素气体间不易分离分析的特点，以5A分子筛微填充石英毛细管色谱柱，在－95℃下对氢同位素进行分离，以气相色谱-脉冲放电氦离子化检测器对氢同位素进行分析。研究建立的H₂、HD与D₂等同位素气体测定方法精密度小于15%，最小检出摩尔分数为1×10^－6。     

压水堆大修下行工况冷却剂主要辐解产物计算研究

压水堆大修时活化腐蚀产物源项控制是降低集体剂量最有力的手段，冷却剂辐解的影响必须予以考虑。本文基于水辐解反应动力学原理，构建了冷却剂辐解动力学模型，根据该模型计算得到了主要辐解产物H₂O₂、O₂和H₂在各工况的生成情况，并讨论了微观反应机理。结果表明：(1)在停堆下行过程中，冷却剂温度从310℃逐步下降到60℃，溶解氢浓度逐步降为0，一回路从还原性转为氧化性，H₂O₂和O₂的生成显著上升；(2)温度、B/Li浓度、溶解氢浓度、H₂O₂和O₂初始浓度等多种因素均会影响辐解产物的浓度；(3)H₂O₂和O₂是相互促进生成的关系，H₂可以显著抑制H₂O₂和O₂的生成，但高浓度的H₂O₂     

氧化锆检测器在微量氢同位素色谱分析中的应用研究

针对氦气与氢同位素气体热导性差异较小的问题,以氧化锆原电池为气相色谱检测器、改性γ-Al_2O_3为填充柱,在液氮温度(77K)下系统研究了氧化锆检测器测量氢同位素的影响因素,对氦气中微量氢同位素气体进行了分离测试。结果表明,氧化锆检测器的最佳工作温度约为700℃,在载气流速为60mL/min条件下,仪器测量的相对标准偏差小于1%,该方法对H2的检测下限可达15ppm,对D2的检测下限可达40ppm,样品检测的相对误差小于5%。以上结果表明,氧化锆检测器可用于氦气中微量氢同位素的分析测量。     

氢/氘气在改性分子筛上的吸附性能研究

在液氮温度下采用容积法研究了5A、ZSM-5及其改性沸石分子筛对氢同位素的吸附分离性能,探讨了过渡金属盐负载和球磨等改性方法对氢同位素气体吸附的影响。结果发现,改性后分子筛上气体的吸附量普遍降低,但某些改性有利于H₂和D₂的分离。     

整体式除氚催化剂的制备及催化氧化性能

针对大型核设施产生的大流量废气的处理,发展低气阻的整体式催化剂尤为必要。本工作在整体式堇青石载体上生长分子筛涂层,以离子交换法负载活性组分Pt,获得的整体式催化剂具有高的金属分散度,达到了60%。使用该催化剂,在15 ℃、体积空速为10 000～40 000 h^-1、1.0%（体积分数）H₂的条件下实现大于99.9%的H₂转化率;在25 ℃、体积空速为50 000 h^-1 、1.0% H₂的条件下实现H2的完全转化。在更低的H₂浓度下（0.1% H₂和0.5% H₂）,该催化剂在湿条件下的H₂转化率低于干条件下的H₂转化率,表明水蒸气会抑制室温催化活性。由于分子筛涂层较Al₂O₃涂层具有更低的吸水性,整体式Pt/sil-cord催化剂在湿条件下具有比Pt/Al₂O₃高得多的室温催化活性（0.1% H₂下,转化率为80%,而在Pt/Al₂O₃ 上的转化率为13%）,表现出较好的抗湿性。     

氨水溶液在γ场中的稳态辐射分解行为研究

含氨冷却剂被应用于压水堆中,可以清除冷却剂辐射分解产生的O₂、H₂O₂等氧化性产物,从而减轻结构材料腐蚀。本文研究了氨水在γ辐射场中的辐射分解行为,考察氨浓度、辐射吸收剂量和吸收剂量率、气液体积比和不同饱和气体对氨水辐射分解行为的影响,重点关注辐射分解产物H₂O₂和NO₂-的浓度变化。结果表明,随着体系中氨浓度的增加,H₂O₂的浓度受到明显抑制,NO₂-的浓度则呈现出上升趋势;吸收剂量的增加使得H₂O₂浓度明显升高,NO₂-的浓度则在吸收剂量为8 kGy时达到最大(>100μmol/L),而后降低;吸收剂量率的差异(2.78～25 Gy/min)并未导致H₂O₂和NO₂-浓度产生明显变化;氨水中的O₂是NO₂     

应用于等离子体排灰气处理的甲烷水汽重整反应的热力学分析

Tokamak装置中的等离子体反应一段时间后,需对产生的排灰气进行净化处理,以回收其中的氘氚。目前拟采用甲烷水汽重整反应将化合态的氘氚转化为单质并回收。本文运用Gibbs自由能最小化方法,对应用于等离子体排灰气处理的水汽重整反应进行热力学分析,考查反应温度、原料比例、反应压力、O₂、CO₂、H₂、CO等因素对反应平衡的影响,确定了适宜的反应条件,即反应温度范围650～700 ℃,压力1×105 Pa,水碳比1.5～2.0。此外,原料气中O₂或CO₂的存在有利于减少积碳的生成量,并获得较高的氢同位素平衡转化率;H₂的存在对重整反应的热力学平衡无明显影响;CO的存在会使积碳量增加,对反应产生不利影响,在进入重整反应器前应将其去除。     

同分子同位素反应及催化剂应用

轻同位素的工业化富集主要采用精馏法,如H₂、O₂、N₂、CO等,这些双原子分子同位素气体在富集中后期,会受到其他同位素干扰而无法得到高丰度的同位素,需要在精馏级联中间增加反应转化装置,排除同位素干扰。在催化剂的作用下,气体分子之间发生反应,同位素原子得到重新组合生成单一同位素气体,继续分离得到高丰度的同位素气体。本文对同位素气体反应及采用的催化剂进行介绍,并着重介绍了C同位素交换反应的平衡常数、反应机理等特性。     

Effect of N_2 and O_2 on OH radical production in an atmospheric helium microwave plasma jet

UV-pulsed laser cavity ringdown spectroscopy of the hydroxyl radical OH(A–X)(0–0)band in the wavelength range of 306–310 nm was employed to determine absolute number densities of OH in the atmospheric helium plasma jets generated by a 2.45 GHz microwave plasma source.The effect of the addition of molecular gases N_2 and O_2 to He plasma jets on OH generation was studied.Optical emission spectroscopy was simultaneously employed to monitor reactive plasma species.Stark broadening of the hydrogen Balmer emission line(H_β)was used to estimate the electron density nein the jets.For both He/N_2 and He/O_2 jets, newas estimated to be on the order of 10~(15)cm~(-3).The effects of plasma power and gas flow rate were also studied.With increase in N_2 and O_2 flow rates, netended to decrease.Gas temperature in the He/O_2 plasma jets was elevated compared to the temperatures in the pure He and He/N_2 plasma jets.The highest OH densities in the He/N_2 and He/O_2 plasma jets were determined to be 1.0?×10~(16)molecules/cm~3 at x?=?4 mm(from the jet orifice)and 1.8?×?10~(16)molecules/cm~3 at x=3 mm, respectively.Electron impact dissociation of water and water ion dissociative recombination were the dominant reaction pathways, respectively, for OH formation within the jet column and in the downstream and far downstream regions.The presence of strong emissions of the N_2~+ bands in both He/N_2 and He/O_2 plasma jets, as against the absence of the N_2~+ emissions in the Ar plasma jets, suggests that the Penning ionization process is a key reaction channel leading to the formation of N_2~+ in these He plasma jets.     

Adsorption capacity of hydrogen isotopes on mordenite

In a fusion reactor system, a monitoring of hydrogen isotopes including tritium is necessary for the safety of system control and operation. A gas chromatography using a cryogenic separation column is one of the methods for hydrogen isotope analysis. Synthesis zeolite such as molecular sieve 5A (CaA) is a candidate material of the separation column, and its property varies by the ratio of silica to alumina, the kinds of cation and so on. If the factor affected the hydrogen adsorption property of the synthesis zeolite is clarified, it may lead to the development of the new zeolite optimized to the separation column. So, in this work, adsorption capacity of hydrogen (H₂) and deuterium (D₂) for mordenite (MOR) and NaY type zeolite (NaY) were investigated at various temperatures, and were compared with CaA. The amount of adsorption per unit weight of MOR was larger than that of CaA, and that of NaY was smaller than that of CaA. The adsorption isotherms were expressed by sum of two Langmuir equations, and the Langmuir coefficients of H₂ and D₂ were proposed. Furthermore, the Langmuir coefficients of HD, HT, DT and T₂ were estimated by the reduced mass. The correlation between the adsorption properties and the physical parameters of the zeolite were not confirmed.     

Photon-induced impurity production in TEXTOR

Analysis of the residual neutral gas during plasma discharges in the tokamak TEXTOR shows considerable amounts of neutral CO and CO₂. Details of these observations have suggested that the CO₂ and part of the CO neutral gas is released from the surfaces by photon-stimulated desorption processes. To prove this suggestion additional mass-spectroscopic measurements have been performed in a chamber vacuum-sealed from the TEXTOR vacuum by a MgF₂-window which is transparent for wavelengths above about 110 nm. It has been confirmed that CO₂ and CO molecules together with H₂ are released from the walls of the chamber by the photons penetrating from the TEXTOR plasma through the window. The overall desorption rate has been estimated to be between 10⁻⁴ and 10⁻⁵ molecules/photon and a linear relation between the amount of desorbed molecules and the total radiation from the plasma has been found. The results are discussed in view of the overall impurity release from the walls and limiters of TEXTOR.     

H_2O_2调价UTEVA树脂对钚的分离方法

研究了H2O2调节钚价态至Pu(Ⅳ)的条件,对于钚质量浓度在10-3 g/L量级的溶液,适量H2O2可以将钚价态稳定在Pu(Ⅳ)。采用粒径为50~100μm的UTEVA树脂填充的柱体积为2mL的萃取色层柱,在6mol/L HNO3浓度下,使用w=1.5%H2O2作为氧化还原剂对10-2 g/L的钚进行预处理,能将钚吸附上柱。通过适当条件的洗脱,在铀、镎、钚混合溶液中,得到钚的回收率约为108%。     

The effect of gas additives on reactive species and bacterial inactivation by a helium plasma jet

In this paper,the influences of gas doping(O_2,N_2,Air)on the concentrations of reactive species and bactericidal effects induced by a He plasma jet are studied.Firstly,results show that gas doping causes an increase in voltage and a decrease in current compared with the pure He discharge under the same discharge power,which might be attributed to the different chemical characteristics of O_2 and N_2 and verified by the changes in the gaseous reactive species shown in the optical emission spectroscopy(OES) and Fourier transform infrared(FTIR)spectroscopy.Secondly,the concentrations of aqueous reactive oxygen species(ROS) and reactive nitrogen species(RNS) are tightly related to the addition of O_2 and N_2 into the working gas.The concentrations of aqueous NO_2~- and NO_3~- significantly increase while the concentrations of aqueous ROS decrease with the admixture of N_2.The addition of O_2 has little effect on the concentrations of NO_2~- and NO_3~- and pH values; however,the addition of O_2 increases the concentration of O_2~- and deceases the concentrations of H_2O_2 and OH.Finally,the results of bactericidal experiments demonstrate that the inactivation efficiency of the four types of plasma jets is He?+?O_2??He+AirHeHe+N_2,which is in accordance with the changing trend of the concentration of aqueous O_2~-.Simultaneously to the better understanding of the formation and removal mechanisms of reactive species in the plasma–liquid interaction,these results also prove the effectiveness of regulating the concentrations of aqueous reactive species and the bacteria inactivation effects by gas doping.