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。     

油页岩中U和Th分布及其赋存状态的研究

利用电感耦合等离子质谱对23个油页岩样品中U和Th含量进行测试,采用浮沉实验和逐级化学提取实验相结合分析了吉林桦甸和罗子沟油页岩样品中U和Th的赋存状态。研究表明,油页岩中铀的含量多小于10×10^-6,平均值为3.92×10^-6,油页岩中钍的含量多小于20×10^-6,平均值为10.51×10^-6。U和Th在油页岩中的丰度略高于在地壳中的丰度,与在沉积岩中的丰度较接近。浮沉实验结果和逐级化学提取结果相当。结果表明,油页岩中U和Th主要存在于无机矿物质中。     

质谱同位素稀释法测定U_3O_8标样中痕量Th

以~(230)Th作稀释剂用IDMS测定了U_3O_8标样中痕量Th。取样1g,先在9mol/l HCI体系中用阴离子交换法除去大量U及Fe、Pb等杂质,进而以CL5209型萃淋树脂分离Th。本法测Th的检出限为2.4×10~(-9)g。分析含Th 0.873 ppm 的U_3O_3试样时方法的精密度为±3.3%。     

三辛基氧膦萃取光度法连续测定矿石中微量铀和钍

同一份称样中微量铀和钍采用三辛基氧膦(TOPO)萃取光度法连续测定,一般文献中所列步骤均较烦琐。本文采用TOPO一次萃取,有机相用0.1mol/L H_2SO_4反萃取钍,经洗涤后直接用5-Br-PADAP-F-光度法测定铀;反萃取液则在0.5mol/L HCl介质中,采用偶氮氯膦mV(CPA-mN)-溴化十六烷基三甲铵(CTMAB)-二苯胍(DPG)多元络合物法测定钍。钍络合物的λ_(max)=670nm,ε_(670)=1.6×10~5,钍量在0—12.5μg/25mL范围内符合比尔定律,组成比Th(Ⅳ):CPA-mN=1:5;铀络合物的λ_(max)=575nm,ε_(575)~5=7.8×10~4,铀量在0—17     

氯化稀土中放射性核素的鉴别和测定

独居石是稀土、钍和铀的共生矿物,含有钍系、铀镭系和锕铀系等三个放射系的几十种核素,其中寿命较长的放射性核素有:~(234)U、~(235)U,~(238)U、~(231)Pa、~(228)Th、~(?)Th、~(232)Th、~(227)Ac、~(226)Ra、~(228)Ra、~(210)Pb、~(21(?))Po等。从独居石中提取稀土元素,不可避免地夹带一些放射性元素。稀土产品中带有放射性杂质,使用时易引起环境污染,这是人们十分关心的问题。锕和稀土同是ⅢB族元素,化学性质相似,很难分离。因此,通常认为氯化稀土中放射性杂质是:~(22(?))Ac     

Th(Ⅳ)在凹凸棒石表面的吸附机理

采用连续电位滴定法研究了天然和高温活化凹凸棒石的表面酸碱和电荷分布性质,利用表面配位模型和FITEQL3.2程序探讨了Th(Ⅳ)在高温活化前后凹凸棒石上的吸附机理.结果表明天然凹凸棒石表面主要以离子交换位(≡XNa/K)、强吸附点位(≡SsOH)和弱吸附点位(≡SwOH)为主;而高温活化凹凸棒石表面则主要以强吸附点位(≡SsOH)和弱吸附点位(≡SwOH)为主.当pH<2.5,Th(Ⅳ)在水溶液中主要以Th4+存在;而当pH>3.0时,Th(Ⅳ)则主要以水解形态存在(例如Th(OH)22+,Th(OH)3+和Th(OH)40).Th(Ⅳ)在天然凹凸棒石表面上的吸附主要以离子交换作用(≡X2Th)和内层配合作用(≡SsOTh)为主,而在高温活化凹凸棒石表面上则主要形成内层配合物(≡SwOTh和≡SsOThOH).胡敏酸(HA)对Th(Ⅳ)在高温活化凹凸棒石上吸附有一定的促进作用,且使Th(Ⅳ)的吸附机理和种态发生明显的改变(主要以≡SsO-CO-HA-Th和≡SsOTh种态存在).Th(Ⅳ)在高温活化凹凸棒石上的吸附是不可逆过程,但当HA存在时,Th(Ⅳ)在高温活化凹凸棒石上会发生解吸.     

以1-苯基-3-甲基-4-苯甲酰基代吡唑酮[5]萃取稀土和钍铀钛锆及其在分析化学中的某些应用

本文研究了以PMBP-苯萃取稀土和钍、铀、钛、锆的萃取行为。测定了La、Ce、Pr、Nd、Sm、Gd、Dy、Yb、Y、U(Ⅵ)、Ti、Th和Zr的pH_(1/2)值,计算了它们的萃取平衡常数。并介绍了近十年来作者将此萃取剂应用于铀、钍、稀土、鋰、钢铁合金及岩石中痕量稀土、钍和钙的分离和测定方面的工作。实践证明,PMOP合成简便、价格低廉、萃取能力较强,是比TTA更为优越的萃取剂。     

我国南海陆坡沉积物沉积速度的研究

应用Th_过~(230)方法测定了南海陆坡沉积物的沉积速度,结果表明,岩柱上部从表层到48厘米,可能发生过滑坡,反映出不连续沉积过程,古气候转暖;岩柱中段,Th_过~(230)强度沿深度呈指数衰减,沉积速度为1.6毫米/1,000年,沉积物可能是在较冷和深水环境中形成的;岩柱从90厘米以下,沉积环境较为活跃,古气候偏暖。根据岩柱各层位中铀、钍含量和其比值以及与Fe,Mn,C(有机),P的关系,本海区主要物质来源于陆相,部分是自生。     

电感耦合等离子体质谱法测定包头地区土壤中的钍

采用电感耦合等离子体质谱法(ICP-MS)对土壤中痕量的钍进行了分析。讨论了基体干扰和质谱干扰,采用稀释法降低基体干扰,并进行了内标选择实验,确定了238U作为方法的内标补偿基体效应。通过对土壤标准物质分析,用王水和HF混合酸微波消解样品,加HC lO4蒸干后用王水溶解残渣。观察到仪器对于Th的测定在不同稀释程度下的线性关系良好。标准加入回收率在93%~106%。方法检出限为0.6μg/L(232Th)。     

P507-H_2SO_4体系萃取色层分离铀、钍、锆、钛的研究

本文用P507-二甲苯作固定相,以硅烷化硅胶作载体,系统地研究了铀(V1)、钍(1V),锆(1V),钛(1V)的萃取色层行为。测定了铀、钍络合物的组成,探讨了铀、钍的萃取机理。提出了连续萃取色层分离铀、钍、锆钛的途径,拟定了矿石中少量铀和钍连续测定的方法。     

Concentration of232Th,230Th and228Th in various tissues of Japanese subjects

The concentration of²³²Th,²³⁰Th and²²⁸Th in various human tissues of Japanese subjects obtained at autopsies are reported. The tissue samples were weighed, spiked with²³⁴Th tracer and ashed by acid. The solution was dried on a hot-plate. Separation of thorium radionuclides was accomplished through cation-exchange resin chromatography and electrodeposition. The concentrations of thorium isotopes were measured by -spectrometry. Thorium-232 and²³⁰Th concentrations were found to be highest in lung, followed by bone. The maximum concentration of²²⁸Th was in bone. The lowest concentrations of thorium isotopes were in muscle.     

U/Th dating of impure carbonates: 230Th/232Th activity ratios in detrital material

Journal of Radioanalytical and Nuclear Chemistry - A derivation of the Bateman equation combined with successive liquid scintillation counting measurements was used to rapidly determine accurate...     

Determination of228Th,230Th,and232Th in environmental samples from uranium mining and milling operations

A method is described for the determination of²²⁸Th,²³⁰Th, and²³²Th in environmental samples from uranium mining and milling operations. The analytical procedure is based on the direct determination of²²⁸Th in the sample by high resolution γ-spectrometry followed by extraction and purification of the thorium fraction using high molecular weight amines and an anion-exchange technique, respectively, prior to α-spectrometry to determine isotopic ratios. The lowest level of detection for each thorium isotope is 0.01 pCi/g for solid samples and 20 pCi/l for aqueous samples. Replicate analyses of a typical mine waste stream gave a standard deviation of ±3% for²²⁸Th. Standard deviations of the²³⁰Th and²³²Th increased to ±11% apparently due to traces of²¹⁰Po interfering in the α-spectrometry.     

A method for the simultaneous estimation of228Th and229Th

A simple method is reported in this paper to estimate²²⁹Th in the presence of²²⁸Th. The total activity of²²⁹Th and²²⁸Th was determined by following the alpha activity growth (using a liquid scintillation counter and proportional counter) of purified thorium samples. The activity ratio of²²⁹Th/²²⁸Th was determined by alpha spectrometry. From the initial total activity and ratio, disintegration rates of²²⁹Th and²²⁸Th were calculated. The values obtained for the activities have a precision better than ±2%.     

Thoriumbromidcluster mit oktaedrischen Th6-Einheiten

Thorium Bromide Clusters with Octahedral Th₆ Units The preparation, structures and properties of the compounds MTh₆Br₁₅ (M = Mn, Fe, Co, Ni), Na_xFeTh₆Br₁₅, Th₆Br₁₅H₇ and Th₆Br₁₄C are described (MTh₆Br₁₅: Im3 m; M = Mn: a = 1150.85(3) pm; Fe: a = 1148.81(4) pm; Co: a = 1150.68(2) pm; Ni: a = 1151.43(4) pm; Th₆Br₁₅H₇: a = 1140.7(1) pm; Th₆Br₁₄C: Cmca; a = 1576.4(3) pm, b = 1416.0(4) pm; c = 1312.4(3) pm). The structures of these compounds are closely related to those of the niobium halides Nb₆F₁₅ and Nb₆Cl₁₄, respectively. All compounds contain Th₆Br₁₂ clusters with octahedral Th₆ cores and interstitial atoms in these cores. The magnetic properties of the compounds are discussed and compared with the results of Extended-Hückel calculations.     

Synthesis and characterization of Th2N2(NH) isomorphous to Th2N3

Using a new, low-temperature, fluoride-based process, thorium nitride imide of the chemical formula Th(2)N(2)(NH) was synthesized from thorium dioxide via an ammonium thorium fluoride intermediate. The resulting product phase was characterized by powder X-ray diffraction (XRD) analysis and was found to be crystallographically similar to Th(2)N(3). Its unit cell was hexagonal with a space group of P3m1 and lattice parameters of a = b = 3.886(1) and c = 6.185(2) ?. The presence of -NH in the nitride phase was verified by Fourier transform infrared spectroscopy (FTIR). Total energy calculations performed using all-electron scalar relativistic density functional theory (DFT) showed that the hydrogen atom in the Th(2)N(2)(NH) prefers to bond with nitrogen atoms occupying 1a Wyckoff positions of the unit cell. Lattice fringe disruptions observed in nanoparticle areas of the nitride species by high-resolution transmission electron microscopic (HRTEM) images also displayed some evidence for the presence of -NH group. As ThO(2) was identified as an impurity, possible reaction mechanisms involving its formation are discussed.     

Determination of232Th in human tissues by pre-concentration neutron activation analysis with yield determination using227Th

The accurate and precise determination of²³²Th in biological samples is very important for the development of biokinetic models for thorium and for improving our knowledge on its distribution in human tissues. Radiochemical neutron activation analysis has long been one of the most sensitive methods for the determination of²³²Th. However, these determinations suffer in reliability because recovery information following the separation is not typically available. This information is particularly important for difficult matrices such as human bone where recoveries may be significantly less than unity. Also, the separation of difficult matrices following neutron activation may involve relatively high personal dose from the co-activated matrix. A novel approach for the determination of radiochemical yield has been developed which employs the use of a readily available, gamma-emitting isotope of thorium,²²⁷Th.²²⁷Th, obtained by radiochemical separation from²²⁷Ac, is added to each, dissolved sample prior to separation and the chemical yield determined by gamma-ray spectrometry following the separation. This pre-concentration step is then followed by neutron activation and the²³²Th determined via²³³Pa using gamma-ray spectrometry. Detection limits were approximately an order of magnitude lower than obtained by alpha-spectrometry.     

Mechanistic aspects of the reaction of Th+ and Th2+ with water in the gas phase

Density functional theory calculations were performed to study the gas-phase reaction of Th(+) and Th(2+) with water. An in-depth analysis of the reaction pathways leading to different reaction products is presented. The obtained results are compared to experimental data and to the previously studied reactions of U cations with water.