氢同位素低温气相色谱分离装置的研制

低温吸附是一种有效的氢同位素分离方式,是国际热核实验堆（ITER）、聚变-裂变混合堆中包层氚提取系统和含氚重水氚回收系统的优选方案之一。课题组采用低温气相色谱技术研制了氢同位素分离装置,开展了氘-氢体系实验。实验结果表明：（1）分离装置的研制是成功的,实现了长期、连续、安全的运行;（2）分离效率高。既可以将天然丰度的氘氢样品浓缩至90％以上,也可以将氘丰度为0．08％的样品混合气分离后得到氘丰度为30％的产品,贫化部分氘丰度小于10^-5;（3）处理容量大。对氕-氘混合气的处理容量达到100m3／a的规模。     

大型低温色谱柱系统的研制

低温吸附是一种有效的氢同位素分离方式,是国际热核实验堆(ITER)、聚变-裂变混合堆(FFHR)包层氚提取系统(TES)和含氚重水氚回收系统的优选方案之一.采用低温气相色谱技术研制了一套大型色谱柱系统,开展了氘-氢体系的调试实验.实验结果表明:(1)低温气相色谱柱系统的研制是成功的,实现了长期、连续、安全地运行;(2)浓缩效率高,可以将天然丰度的氘氢样品浓缩至91%以上;(3)处理容量大,对氕-氘混合原料气的处理容量达到每天200方的规模.     

氘、氚与RAFM钢相容性研究进展

核聚变能是解决人类能源危机和环境问题最有效的途径,其主要是利用氘氚聚合释放的能量。磁约束聚变是目前最可能实现受控热核聚变的方法,但要实现长期且稳态的核聚变反应还面临着诸多挑战,其中材料的研究与开发是聚变堆能否商业化的关键。在服役过程中,包层结构材料不仅受到高热负荷及强腐蚀作用,还受到各种粒子如氘(D)、氚(T)、氦(He)等的轰击和D-T聚变反应产物高能中子的影响。目前,确定的候选结构材料主要有奥氏体不锈钢、低活化铁素体/马氏体(RAFM)钢、钒合金以及碳化硅复合材料四种。而RAFM钢因具有低活性、较低的热膨胀系数、较高的热导率、辐照环境下具有较好的几何稳定性被选为目前最具前景的结构材料。获得氘氚在RAFM钢中的输运参数是未来核数据库建立的基础和前提,近几年关于氘在RAFM钢中输运行为的研究较多,然而不同研究者所得的结果差别很大,且缺乏实际的氚实验的基础数据。因此建立实验测试标准十分必要。RAFM钢主要以板条马氏体结构为主,具有较高的氘、氚渗透率,极易造成氘氚燃料的损失及氚放射性污染。因此,必须减少或避免RAFM钢与氘氚的直接接触。在RAFM钢表面制备一定厚度的阻氚涂层是实现氚自持最有效的途径之一。目前,国内外研究较多的阻氚涂层为Al2O3涂层,其阻氚因子可达103,且已实现工程化应用。此外,RAFM钢在服役过程中产生的辐照损伤及表面状态变化必然会影响氘氚的输运行为,主流观点认为辐照产生的缺陷会增加氘氚在金属材料中的滞留量,当材料中氘原子浓度达到10-6时,塑韧性下降,产生氢脆,尤其对于氚,衰变产生的He-3原子浓度达到10-9时,还会引发更严重的氦脆。除了制备阻氚涂层外,最近的研究多致力于通过成分调控及改善热处理工艺来提高RAFM钢的抗氢性能及抗辐照性能。本文归纳了氘氚在RAFM钢中行为的研究进展,分别对RAFM钢中氘氚渗透和滞留行为及其对力学性能的影响等进行介绍,分析了RAFM钢开发面临的问题并展望其前景,期望为RAFM钢数据库的建立以及服役于聚变堆的工程可行性提供参考。     

CECE法重水电解分离氚的热力学研究

文章研究了CECE法中D2-含氚重水同位素交换以及电解的热力学问题,即可逆分解电压和2个反应(19-1) 和(19-2)的热力学平衡条件。研究给出了H2O, HDO, D2O, DTO和T2O的可逆分解电压。H2O(0) 与T2O(4)的可逆分解电压的相差为0.047 V,如要保留T2O,则实际的分解电压不能大于H2O的分解电压。同时,导出了这5种氢同位素水的平衡蒸汽压和汽化热与温度(0～100 ℃)的函数关系。从热力学来讲,反应(19-1)和(19-2)的平衡常数都很小,在静态反应中难以实现,如果在流动系统中,则能符合条件Q < K,使反应进行。电解分离氢同位素水的最大的难点是选择性差,可以探索使用光催化分离的方法。     

低温精馏与低温气相色谱复合法分离氢同位素

采用低温精馏与低温气相色谱相结合的方法分离、浓缩氢同位素,探讨了分离过程操作参数间的内在联系.实验结果表明:氘浓度为10-3的100 m3原料气经过120 h的连续运行后,可以将氘浓度浓缩至91.5%;低温精馏柱随着回流比的增大,再沸器和冷凝器中氘浓度均减小;顶端采出量增大,再沸器中氘浓度明显增大;随再沸器加热功率的增加,液氢液位下降,床层压降增加,精馏柱操作压力从100 kPa上升到190 kPa,冷凝器和冷头为提供更多冷量温度降低;低温色谱的分离、浓缩效果十分显著,3次运行后将氘浓度从1.25×10-2提高到91.5%.     

氘-氚燃料芯块低温三元相图的建立

为了完成聚变-裂变混合堆(FFHR)氘-氚燃料循环系统的概念设计,掌握氘-氚燃料芯块(D2-DT-T2)的低温性质,依据实验测量的氢同位素一元和二元相图数据、计算程序,初步建立了D2-DT-T2体系的低温三元相图。在此基础上初步分析了D2-DT-T2在19.7 K等温截断面的性质,预测了初始摩尔分数为50%-50%的液体D2-T2在三相点的平衡组成。     

低温热色谱分离氢同位素

叙述了用“６０１”碳分子筛作托卡马克废气排出气的收集、纯化和低温热色谱的进样单元，以５Ａ分子筛柱在液氮（ＬＮ２）温度下吸附氕、氘，氚，随后把柱温回升至室温（２０℃～３０℃），为了提高分离效率、缩短分离时间和分离柱总长度，在两根分离柱间添加了ＨＤ、ＨＴ等歧化平衡器，经过四根分离柱组成的级联分离柱后氕、氘、氚获得了清晰分离。该装置的单次进样量为５标准升，日处理量为１２０～１８０标准升，流程气体总回收率＞９７％，氘丰度＞９９．９％时，氘、氚损失量（不计加热３００℃活化再生分离柱回收的氘、氚）＜５％，除氕效率＞９８％。     

钛吸氢、氘和氚的动力学同位素效应研究

应用反应速率分析方法,在高真空金属系统上测定了钛在恒容体系和550℃～750℃范围内吸收氢、氘和氚的P-t曲线,并由此计算了各自在不同温度的速率常数,得到钛吸氢、氘和氚的表观活化能分别为(55.6±2.4)kJ/mol、(110.2±3.0)kJ/mol和(155.5±3.2)kJ/mol.钛吸氚的表观活化能最高,钛吸氢的表观活化能最低,表现出显著的动力学同位素效应,表明钛吸氚进行氚化反应较氘化和氢化更难于进行.     

核聚变堆用氚增殖剂材料及其制备技术的研究进展与发展趋势

核聚变能是清洁安全的理想能源,是最终可能解决人类能源问题的途径之一。氚是核聚变的关键原料,自然界中存在稀少,如何利用氘-氚聚变反应产生的中子与含有锂的氚增殖剂材料发生核反应制备氚并使之自持是目前聚变工程堆尚待验证的核心关键技术,且是三大难题之一。常用氚增殖剂材料包括液态含锂金属与固态含锂陶瓷,目前示范堆型设计主要考虑选用固态陶瓷增殖剂,包括硅酸锂(Li_4SiO_4)、钛酸锂(Li_2TiO_3)、锆酸锂(Li_2ZrO_3)、氧化锂(Li_2O)等,并将增殖剂包层设计为球床结构。欧盟氦冷球床包层(HCPB)和中国氦冷固态包层(HCSB)中均选用Li_4SiO_4小球为增殖剂材料。根据以往设计经验,中国聚变工程实验堆(CFETR)也优先考虑硅酸锂小球作为氚增殖剂材料。本文总结了传统氚增殖剂的制备技术,包括锂同位素分离技术、小球成型工艺技术和成型过程中相纯度控制。分析对比了国内、国外氚增殖剂的常用方法的差异与优劣。通过比较发现传统制备技术获得的氚增殖剂小球的性能差异不大,且随着对氚增殖剂材料研究的推进,性能要求愈发严苛,不仅需要满足聚变堆内服役力学性能、产氚性能的要求,还应注重氚释放性能与安全性。传统球床结构目前存在诸如装载密度较低、小球易破碎堵塞提氚通道等缺陷,甚至会危及聚变堆安全,故需要开发结构和性能更优的新一代先进的增殖剂材料。本文综述了传统氚增殖剂材料制备技术,同时指出需要开发新型增殖剂材料的理由。重点阐述了新型一体成型多孔氚增殖剂的综合性能优势,并对新型一体成型多孔氚增殖剂材料研究进行了展望。     

氢化锂含氚量变化之数学模型的测定

氢化锂含氚量的实际及化与氚的自然衰变规律并不完全一致,为了测定其变化规律,对贮存中的氢化锂含氚量进行了长时间跟踪测量。本文利用实测数据与多项式回归法,结合氚的衰变规律建立了氢化锂含氚量变化的数学模型,此模型在测量点具有很低的预测误差。     

The influence of deuterium exposures on subsequent outgassing rate of an UHV system

The accuracy of results in experiments where a well-processed UHV system is exposed to hydrogen depends on the hydrogen absorption rate and kinetics of subsequent spontaneous release from the system itself. In experiments to date, the sensitivity required to detect very low rates has been achieved only when tritium has been used as a tracer gas. Unfortunately, tritiated water from the surface prevails among released gas species which is not expected for well-outgassed surfaces. In the present studies, UHV system behaviour at 303 K during three deuterium exposures of duration 92 and 72 h at an initial pressure of 1 mbar was explored. The rate of decrease of pressure was constant during the whole of these periods as monitored by non-ionizing vacuum gauges. It corresponded to an effective sticking probability of the order of 1×10^-12 and resulted in absorption of 5×10¹⁴ D atoms/cm². The release kinetics were observed for several days starting immediately after deuterium had been pumped from the system. Initially, the deuterium release rate exceeded the background hydrogen outgassing by more than three orders of magnitude. These results demonstrate that extremely high sensitivity for deuterium absorption and release can be achieved with a precise pressure measuring technique otherwise attributed exclusively to tritium scintillation methods.     

Dosimetric implications of atmospheric dispersal of tritium near a heavy-water research reactor facility

An estimate of the tritium dose to the public in the vicinity of the heavy water research reactor facility at AECL-Chalk River Laboratories, Ontario, Canada, has largely been accomplished from analyses on regularly-collected samples of air, precipitation, drinking water and foodstuffs (pasture, fruit, vegetables and milk) and environmental dose models. To increase the confidence with which public doses are calculated, tritium doses were estimated directly from the ratio of tritiated species in urine samples from members of the general public. Single cumulative 24 h urine samples from a few adults living in the vicinity of the heavy-water research reactor facility at Chalk River Laboratories, Canada were collected and analysed for tritiated water and organically bound tritium. The participants were from Ottawa (200 km east), Deep River (10 km west) and Chalk River Laboratories. Tritiated water concentrations in urine ranged from 6.5 Bq.l-1 for the Ottawa resident to 15.9 Bq.l-1 for the Deep River resident, and were comparable to the ambient levels of tritium-in-precipitation at their locations. The ultra-low levels of organically bound tritium in urine from these same individuals were measured by 3He-ingrowth mass spectrometry and were 0.06 Bq.l-1 (Ottawa) and 0.29 Bq.l-1 (Deep River). For Chalk River Laboratories workers, tritiated water concentrations in urine ranged from 32 Bq.l-1 to 9.2 x 10(4) Bq.l-1, depending on the ambient levels of tritium in their workplace. The organically bound tritium concentrations in urine from the same workers were between 0.08 Bq.l-1 and 350 Bq.l-1. With a model based on the ratio of tritiated water to organically bound tritium in urine, the estimated dose arising from organically bound tritium in the body for the Ottawa and Deep River residents was about 26% and 50%, respectively, of the body water tritium dose. The workers in a reactor building at Chalk River Laboratories had less than 10% dose contribution from organically bound tritium, but had higher overall tritium dose due to frequent intakes of tritiated water vapour in the workplace. The results of this study suggest that most of the tritium dose to workers at Chalk River and general population near Chalk River is the result of tritiated water intakes and not due to dietary intake of organically bound tritium.     

甲烷催化裂解技术研究进展

甲烷催化裂解技术因在适当的吸热过程中裂解只生成碳和氢气而在制备高纯氢气和性能优异的碳纳米管以及ITER(国际热核聚变实验堆)废气处理系统中裂解氚、氘代甲烷以回收其中的氚和氘等方面具有十分重要的意义。介绍了甲烷催化裂解反应机理,阐述了甲烷裂解催化剂的制备方法、催化剂性能的影响因素以及催化剂的失活与再生,指出焙烧温度、活性金属、载体和反应温度对催化剂性能有重要影响,讨论了甲烷催化裂解反应中存在的问题。     

Reassessment of tritium dose coefficients for the general public

Concerns of increased risk from tritium intake by humans have been claimed in the past. The arguments concerning the radiobiological effectiveness of tritium, its longer retention in the human body and the presence of tritium in the DNA hydration shell are analysed in this paper. A biokinetic model for tritiated water and organically bound tritium retention in the human body is used, based on a common approach for mammals using energy and hydrogen metabolism and tested separately with animal experiments. Extension to this model to humans considers the increased role of the brain, food quality and unique growth patterns of humans. Various ages and genders for Caucasians are considered. For an intake of tritium in organic forms in the diet, the retention for the female is of about a factor 2 compared with ICRP recommendations. Effective dose coefficients are estimated to be about a factor of 2 to 3 higher than those of the ICRP.     

气载氚监测仪校准用氚化甲烷体积活度测量方法及其不确定度分析

针对气载氚监测仪校准用气体参考源氚化甲烷,提出其体积活度测量方法,用催化氧化燃烧炉将其转化为氚化水,用二级串联鼓泡器收集氚化水,并用液体闪烁计数器测定活度,从而确定气体参考源氚化甲烷体积活度,并进行了不确定度分析测定实验室已有氚化甲烷的体积活度为17.4 MBq/m3,不确定度为6.4％(k=2),符合GBT 3015...     

Tritium in the urine in Finnish people

Tritium in urine was analysed from 227 randomly selected Finnish adults. The people were 18 to 65 of age. Urine samples were collected over night. The mean activity concentration of tritiated water in urine was 2.5 Bq l(-1) and the maximum activity concentration 18.3 Bq l(-1). The minimum detectable activity varied from 1.5 to 2.3 Bq l(-1). Because organically bound tritium is approximately 10% of the total tritium, its concentration was below the detection limit and could be ignored. The mean effective dose for Finnish people from tritium was 2.4 x 10(-3) microSv y(-1).     

Blood tritium level as an estimate of soft tissue dose

To test the blood tritium level as an estimate of free water tritium (FWT) and organically bound tritium (OBT) in human soft tissues, a tritiated amino acid mixture (TAA) and tritiated water (HTO) were injected or orally administered to mice. Relatively high tritium retention in the blood was found after TAA injection. This observation was explained by a low rate of clearance of non-volatile tritium components. The dose estimated for the soft tissues after TAA injection was larger than that estimated on the basis of tritium concentration in urine by a factor of 1.8-2.3. In both HTO and TAA injections, the blood tritium level gave a conservative estimate of the dose to soft tissues including active bone marrow. The accumulated dose to soft tissues after oral administration tended to be lower than that for intraperitoneal injection.     

Atomic and Molecular Hydrogen Impurities in Liquid 4He

The static properties of a single hydrogen atom and an hydrogen molecule in bulk superfluid ⁴ He are studied by means of the diffusion Monte Carlo method. The analysis includes atomic hydrogen, deuterium and tritium, and molecular hydrogen and deuterium. Our results, which show some differences with previous variational calculations, are in agreement with the only available experimental data corresponding to atomic deuterium. In contrast to the unbinding presented by the atomic impurities, the molecular ones do bind with energies higher than the chemical potential of pure ⁴ He.