在高分子负载的钯催化剂上氢-氚交换反应的研究

气-液交换法制备氚标记化合物的实质是氢-氚同位素交换,近年来国内开始引用。该法具有操作方便、快速、比度高和杂质少等优点,尤其是可标记结构复杂的天然产物如中草药有效成份。改进和完善     

液态锂铅合金中微量氚的回收

解决全球能源问题的聚变反应堆一直备受关注,其中由欧盟、俄罗斯、中、韩、印、日等多方合作的ITER(International Thermonuclear Experimental Reactor)计划便是一个代表性的进展标志.ITER实验包层工作组将液态锂铅实验包层模块列为重点开发对象,中国提出的双功能锂铅实验包层模块DFLL-TBM(Dual FunctionLithium Lead-Test Blanket Module)是主要研究方案之一,液态锂铅集氚增殖剂、冷却剂和中子倍增剂于一身,可采用鼓泡器方式实现氚的提取.有关含氚固体废物的回收早有报道,但主要集中于贮氢材料中氚的同位素交换和氘氚化锂残渣中的氚回收,而高温液态合金中氚的回收还未见报道.如果要将液相锂铅中的氚滞留量降低到包层设计的要求,则必须使其上方的氚分压不超过107Pa,采用单纯的氦吹洗或真空脱气难以满足要求,102Pa是它们所能达到的最低极限压力,这是因为在低氚浓度下,由液相转入气相的氚速率是受氚在液相、气相及气-液界面的扩散过程所限制.为了提高从锂铅合金中回收氚的效率,减小氚在液相和气相的分子扩散阻力及气体在液相的滞留时间,本文采用氦吹洗气以及其与氢、氘的混合气作为交换载带气,利用同位素效应(isotopic effect),对液态锂铅合金中的微量氚开展实验回收的预先研究,期望对今后包层氚提取系统(TES)的工程化设计与建造提供技术支持.研究结果显示:随着交换温度的升高,氚的回收率明显增加,并且温度越高,第一次解吸的氚量越大.623K时,同位素交换效果较差,氚回收率较低;723K时经过6次交换后氚的回收率为78.2%;823K时交换一次氚的回收率就可达到66.3%.在相同温度下,氚回收率随交换次数的增加而增加,但经过6次交换后,曲线趋于平坦,氚回收率似乎在接近80%左右形成最大值.此外,单独使用氦吹洗气,氚回收率不到30%;添加0.1%的氘比氢的回收率要略高一些,这是因为充氚结束后的锂铅合金处于平衡状态,并非饱和状态,要交换出合金内的氚,必须预先吸附一定量的载带气,使其达到交换温度下的气体平衡离解压力,方可将合金中的氚交换出来.在较高的交换温度下,氚比氘、氘比氢更容易从锂铅中解析出来,这与气相色谱法分离氢同位素的原理是一致的.但过度增加载带气中氘的比例,反而降低了氚回收率,这是因为随着氘分压的增大,吸附质之间的同位素效应将减弱.总之,采用氦与0.1%氘组成的混合吹洗气,利用同位素交换效应对锂铅合金中的微量氚进行回收是有效的,氚回收效率接近80%;交换温度和交换次数对氚回收率的影响显著,在载带气相同的情况下,温度越高,交换次数越多,氚回收率越高.     

岩石矿物中铀钍的分析方法进展——非破坏分析法

非破坏分析法部分着重介绍了岩石矿物中铀钍的非破坏性分析方法原理、特点和应用范围。非破坏分析手段主要包括:中子活化分析法(NAA)、裂变径迹法(FTA)、X射线荧光光谱法(XRF)、激光烧蚀光谱法(LIBS)和γ能谱直接测量法。非破坏分析鉴于其独特优势仍有发展空间,LIBS技术是新近发展的具有较大潜力的技术手段,而γ能谱直接测量法针对铀钍等放射性核素的测量具有无可比拟的发展优势。     

环境样品中铀的HR-ICP-MS测定

高分辨电感耦合等离子体质谱法(HR-ICP-MS)是痕量元素分析的有效手段。本文采用HR-ICP-MS对环境样品(土壤、底泥、茶叶、地表水)中铀浓度和同位素比值进行了测定。土壤、底泥、茶叶样品采用微波消解法进行溶解;水样采用45μm滤膜过滤后直接测定。实验对样品制备、仪器参数设定、记忆效应消除、质量歧视效应修正等进行了探索,建立了环境样品中痕量铀浓度和同位素比值测定方法。土壤制样过程中铀的加标回收率为97.7%,铀检出限0.51ng·L~(-1)。     

多接收电感耦合等离子体质谱在单个铀颗粒物分析中的应用研究

为准确地获取单个铀颗粒物中具有核保障监督和核取证意义的铀同位素组成信息和~(230)Th/~(234)U比值,本研究基于多接收电感耦合等离子体质谱(MC-ICP-MS),建立了不同粒径铀颗粒物中铀同位素比值的测量方法和不经化学分离纯化流程的~(230)Th/~(234)U分析技术。在评估铀钍本底的基础上,采用外标法校正同位素的质量分馏效应,进样0.40 ng/g的天然铀工作溶液跳峰测量离子计数器检测效率,使用已知铀钍比例的标样校正铀钍响应差异,完成分析方法的不确定度评估。结果表明,化学处理过程引入的~(238)U和~(232)Th分别小于8×10~(-5)ng和1.5×10~(-3)ng,MC-ICP-MS对粒径0.5~5.0μm铀颗粒物中~(235)U/~(238)U测量的相对扩展不确定度3.6%(k=2),主要来自本底扣除引入的不确定度和B类不确定度;对粒径5μm铀颗粒物中~(235)U/~(238)U测量的相对扩展不确定度0.2%(k=2),主要来自法拉第杯检测器对弱信号测量的不确定度;对更大粒径铀颗粒物中~(234)U/~(235)U和~(236)U/~(235)U测量的相对扩展不确定度分别小于3.5%和3.8%(k=2),主要来自B类不确定度。不经铀钍分离纯化流程,MC-ICP-MS可测得粒径几十微米铀颗粒物中~(230)Th/~(234)U比值信息,并诊断浓缩铀颗粒物生产年龄。     

铀冠醚配合物晶体结构、红外光谱和同位素效应

本文根据单晶的X射线衍射及红外光谱法的实验结果,对铀冠醚配合物(DCH18C6·H_3O)_2UO_2Cl_4的约化配分函数比(RPFR)及各有关振动基频的贡献进行了详细的理论计算,从而估计了UO_2~(2+)(H_2O)_5-(DCH18C6·H_3O)_2UO_2Cl_4铀同位素化学交换体系的交换反应平衡常数K_(eq)(即同位素单级分离因子α,在12℃C和29℃下,分别得到α=1.000746和1,000672与实验值1.0010±0.0002和1.0012±0.0004相当接近。通过理论分析表明,铀的配位水在铀与冠醚形成配合物过程中被剥离,对体系的显著同位素效应起了关键作用。     

激光烧蚀-多接收电感耦合等离子体质谱法测定铀颗粒物中铅杂质的同位素比值

为有效获取铀颗粒物中具有取证价值的铅杂质同位素信息,建立了激光烧蚀-多接收电感耦合等离子体质谱(LA-MC-ICP-MS)测定铀颗粒物中铅杂质同位素比值的方法.探究了诸多同位素分馏效应校正方法下铅本底对同位素测量的影响,选用的LA-MC-ICP-MS系统的本底对比值测量结果的影响小于0.001(208Pb的信号强度大于2.2× 103 cps),确定采用NIST SRM612为外标校正质量分馏,固定激光束斑直径30μm、脉冲重复率20 Hz、调节能量密度使LA-MC-ICP-MS分析NIST SRM612和铀颗粒物样品所得208Pb分别小于1.5×105 cps和3×104 cps,标准物质CRM124-4样品中206Pb/208Pb、206Pb/207Pb和207Pb/208Pb比值测量结果的相对实验标准不确定度小于0.48％、0.68％和0.40％.实际样品分析结果表明,本方法可有效区分铀颗粒物中的铅同位素比值差异,有助于鉴别其来源.     

电感耦合等离子体质谱法测定碳化硼中的硼同位素丰度

以碳酸钙为熔剂高温分解,硝酸浸取、硫酸沉淀的方法处理碳化硼样品,稀释后直接进行多接收电感耦合等离子体质谱分析,对碳化硼中的硼同位素丰度进行测定。扫描电镜分析结果表明,碳化硼颗粒形状不规则,尺寸小于50μm。利用建立的方法处理样品,可实现碳化硼样品的完全溶解,回收率接近100%。对样品中10B丰度进行分析,相对标准偏差为0.023%~0.035%(n=6),测量结果与参考值在不确定度范围内保持一致,证明实验方法可行。所建立的碳化硼样品测量方法样品处理步骤简便,分析速度快,测量精度高,可作为碳化硼中硼同位素丰度的常规分析方法。     

阳离子交换树脂分离-离子色谱法测定碳酸稀土和氯化稀土中硫酸根

用阳离子交换树脂柱上交换法将试样中硫酸根与稀土离子分离.交换柱上流出溶液再经AS 9阴离子分离柱(250 mm×4 mm)分离,用9.0 mmol·L-1碳酸钠溶液作流动相.定量测定中采用电导检测器和标准曲线法,该方法的检出限为0.05 mg·L-1,测定下限为0.03%.对硫酸根质量分数为3.19%的试样作精密度试验,测得相对标准偏差(n=11)为1.63%,回收率试验的结果在94.2%～112.6%之间.     

电感耦合等离子体质谱法测定矿物渣中微量铀和钍

采用改进的微波消解程序处理矿物渣样品,用185Re作为内标同位素,以在线内标加入法补偿样品的基体干扰,提出了测定矿物渣中微量铀和钍的电感耦合等离子体质谱法.铀和钍的方法检出限分别为0.017,0.021 ng·g-1;铀和钍的平均加标回收率(n=6)分别为99.0%,101.3%;相对标准偏差(n=6)分别为4.02%和3.54%.两种标准物质中铀和钍的测定结果与标准值相符合.     

Physicochemical conditions for effective hydrogen isotope storage and delivery in a uranium bed

This paper proposes physicochemical conditions for effective hydrogen isotope storage and delivery in a uranium bed. Effective physicochemical conditions for tritium storage and delivery are obtained by manipulating initial depleted uranium (DU) temperatures and hydrogen pressures and applying three distinct operation scenarios. These novel physicochemical conditions and operation scenarios enable higher and more constant hydrogen recovery and delivery rates. The results presented can be used to facilitate the storage and delivery of tritium for environmental protection and waste management in nuclear fission reactors, and for future commercial use in isotope industries and nuclear fusion fuel systems.     

紫外线激活氚原子—制备氚标记单磷酸阿糖腺苷的研究

本文采用紫外线激活氚原子的方法,进行氚-氢同位素交换反应,制得氚标记单磷酸阿糖腺苷(9—~3H—mparaA)。产品的纯度是层析纯;放射性比活度16GBq.m mol~(-1);放射化学纯度92.0%。本法的优点是:交换反应温和、反应时间较短、不易破坏生物活性、引起的副产物少、产品分离和纯化较方便。     

分光光度法测定三氧化铀中的硫酸根

采用TBP-萃淋树脂吸附三氧化铀样品中的铀,硫酸根与铬酸钡进行交换反应后,直接比色法测定硫酸根的含量。实验中研究了三氧化铀样品中硫酸根含量测定的样品制备、分离、反应酸度,煮沸时间,铬酸钡用量等影响因素。优化条件下,采用硝酸(5mol/L)淋洗、1mL HCl溶液(2.5mol/L)调节溶液中酸浓度、使用2mL BaCrO_4进行交换反应、煮沸3min,得到方法相对标准偏差小于10%,加标回收率为92.9%～110%。实验结果表明,直接显色的测定方法灵敏、快速、准确度高。方法测定条件易于获得,适于推广应用。     

疏水催化剂用于水中氚回收的实验研究

本文简要介绍了自制的几种疏水催化剂的主要特性,采用这些催化剂进行了室温下的H—T同位素交换实验,初步考察了氢气流速对催化活性的影响。实验表明,催化剂的催化活性较高,能够用于室温下从氚水中回收氚。     

Synthesis of radiolabelled compounds

Compounds labelled with radioisotopes such as¹⁴C,³H,³²P,³⁵S and¹²⁵I, are essential tools for research and especially in the life sciences. Syntheses can be directed to isotopic labelling or to non-isotopic labelling. In isotopic labelling a compound is labelled with an isotope of an element already present in the compound whereas non-isotopic labelling is achieved with an isotope is foreign to the material or compound being labelled. This paper reviews the properties of the more important and commonly used radioisotopes in research and methods currently employed for the synthesis of radiolabelled compounds. The relative ease of measurement of radioactivity in large numbers of samples, when compared for example with the measurement of mass, and the great sensitivity with which very small quantities of radioactive compounds can be accurately measured, has resulted in the widespread need and use of radiolebelled compounds. Methods for the practicable labelling of compounds for use as radiotracers all into three main categories, namely, chemical systhesis, biochemical methods and isotope exchange reactions. Examples are chosen to illustrate these methods for the labelling of amino acids, peptides, proteins, carbohydrates, lipids, neurochemicals, nucleic acids, steroids and miscellaneous compounds of interest in biological research. Most methods of labelling employed lead to specific labelling, that is, to modecules in which the position(s) of the radioactive atom(s) is known with certainty. However, isotope exchange reactions which are especially useful for labelling molecules with tritium are often non-specific. The routine use of tritium nuclear magnetic resonance spectroscopy has resolved any uncertainties in the specificity of labelling with tritium. Examples are given illustrating the effectiveness of this valuable analytical technique. A review of the synthesis of radiolabelled compounds would not be complete without reference to the special properties of the labelled compounds themselves which affect their useful shelf-life, self-decomposition, purification and analysis; factors which all need to be clearly understood in order to use radiolabelled compounds with confidence in scientific research.     

In situ Generated Iridium Nanoparticles as Hydride Donors in Photoredox-Catalyzed Hydrogen Isotope Exchange Reactions with Deuterium and Tritium Gas

We have studied the photoredox-catalyzed hydrogen isotope exchange (HIE) reaction with deuterium or tritium gas as isotope sources and in situ formed transition metal nanoparticles as hydrogen atom transfer pre-catalysts. By this means we have found synergistic reactivities applying two different HIE mechanisms, namely photoredox-catalyzed and CH-functionalization HIE leading to the synthesis of highly deuterated complex molecules. Finally, we adopted these findings successfully to tritium chemistry.     

A Procedure for Determination of Tritium in Potassium

Abstract

A procedure has been developed for the quantitative analysis of potassium for its tritium content. This procedure consists of dissolving the highly reactive alkali metal in an inert liquid containing a small amount of ethanol and then analyzing the resulting solution for its tritium content by classical methods. Techniques previously used for sodium analysis are reviewed and discussed as they apply to the more reactive potassium.     

Application of Inductively Coupled Plasma Mass Spectrometry to the determination of uranium isotope ratios in individual particles for nuclear safeguards

The capability of inductively coupled plasma mass spectrometry (ICP-MS) for the determination of uranium isotope ratios in individual particles was determined. For this purpose, we developed an experimental procedure including single particle transfer with a manipulator, chemical dissolution and isotope ratio analysis, and applied to the analysis of individual uranium particles in certified reference materials (NBL CRM U050 and U350). As the result, the ²³⁵U/²³⁸U isotope ratio for the particle with the diameter between 0.5 and 3.9 μm was successfully determined with the deviation from the certified ratio within 1.8%. The relative standard deviation (R.S.D.) of the ²³⁵U/²³⁸U isotope ratio was within 4.2%. Although the analysis of ²³⁴U/²³⁸U and ²³⁶U/²³⁸U isotope ratios gave the results with inferior precision, the R.S.D. within 20% was possible for the measurement of the particle with the diameter more than 2.1 μm. The developed procedure was successfully applied to the analysis of a simulated environmental sample prepared from a mixture of indoor dust (NIST SRM 2583) and uranium particles (NBL CRM U050, U350 and U950a). From the results, the proposed procedure was found to be an alternative analytical tool for nuclear safeguards.     

EDTA返滴定法测定铀钼合金中钼含量

介绍了采用EDTA返滴定法测定铀钼合金中钼含量的方法。以王水溶样,用磷酸三丁酯-氢化煤油萃取分离铀,采用盐酸羟胺将Mo6+还原为Mo5+,用EDTA络合Mo5+,然后用锌标准溶液返滴定过量的EDTA,从而完成铀钼合金中的钼含量测定。优化了方法的实验条件,实验表明,相对标准偏差(RSD)为1.4%。     

Tritium/Protium Fractionation Near and Inside DNA

The fractionation factor of tritium between water and DNA as well as between water and the first hydration shell of DNA is determined. For this purpose the sublimation kinetics of water from DNA dissolved in water were determined at -200 °C and tritium was measured in the remaining water free DNA. The last sublimating water fractions showed a tritium level of about 1.4, the residual water free DNA about 1.9 units above the bulk water. The tritium accumulation inside and near DNA is attributed to the thermodynamic triton-proton exchange isotope effect existing between the strong hydrogen bridges of water and weaker hydrogen bridges as well as inside DNA as between the first hydration shell and DNA.