A new value for the half-life of Be by Heavy-Ion Elastic Recoil Detection and liquid scintillation counting

The importance of ¹⁰Be in different applications of accelerator mass spectrometry (AMS) is well-known. In this context the half-life of ¹⁰Be has a crucial impact, and an accurate and precise determination of the half-life is a prerequisite for many of the applications of ¹⁰Be in cosmic-ray and earth science research. Recently, the value of the ¹⁰Be half-life has been the centre of much debate. In order to overcome uncertainties inherent in previous determinations, we introduced a new method of high accuracy and precision. An aliquot of our highly enriched ¹⁰Be master solution was serially diluted with increasing well-known masses of ⁹Be. We then determined the initial ¹⁰Be concentration by least square fit to the series of measurements of the resultant ¹⁰Be/⁹Be ratio. In order to minimize uncertainties because of mass bias which plague other low-energy mass spectrometric methods, we used for the first time Heavy-Ion Elastic Recoil Detection (HI-ERD) for the determination of the ¹⁰Be/⁹Be isotopic ratios, a technique which does not suffer from difficult to control mass fractionation. The specific activity of the master solution was measured by means of accurate liquid scintillation counting (LSC). The resultant combination of the ¹⁰Be concentration and activity yields a ¹⁰Be half-life of T_1/2 = 1.388 ± 0.018 (1 s, 1.30%) Ma. In a parallel but independent study (Chmeleff et al. [11]), found a value of 1.386 ± 0.016 (1.15%) Ma. Our recommended weighted mean and mean standard error for the new value for ¹⁰Be half-life based on these two independent measurements is 1.387 ± 0.012 (0.87%) Ma.     

固相闪烁蜡用于液闪测量的评价

介绍一种利用含闪烁体的蜡片熔于样品所在滤膜上进行测量的固相制样技术。与目前常用的普通闪烁液相比较，不同滤膜的测量效率对３Ｈ为３％—１０％。在不同厂家的仪器上测量结果趋势一致。测量结果的精确度和平行度也达到了较好的水平，说明此法适合于大量样品的相对测量。     

HP的液体闪烁测量法

用液体闪烁测方法,通过测量患者呼气中＾１４Ｃ标记的尿素水解物的含量来诊断患者是否感染幽门螺杆菌。     

液体闪烁测量中常被忽略而引入很大误差的问题

液体闪烁测量所用的闪烁液多种多样，而淬灭校正曲线往往只有一二种，闪烁液与淬灭校正曲线之间的不匹配，可以在测量中引入10％左右的误差，甚至更高，讨论了这些有关问题。     

用液闪直接测量核设施周围环境中的氚

某些核设施运行时会释放氚,从而引起周围环境中氚活度浓度水平的变化。对核设施周边区域空气、地下水、雨水和海水样品中的氚分别用内标准法(简称“内标法”)和外标准淬灭指示参数法(简称“外标法”)进行了液闪测量。两种标准方法测量数据的相对偏差在-4.0%～4.0%。根据内标法的探测效率与仪器给出的淬灭指示参数制作了4种环境水样的淬灭校正曲线。在环境样品测量中,内标法和外标法的探测效率最大差值约为1.6%,痕量¹⁴C和其它β放射性核素对³H的计数率影响可忽略。对探测效率为21.5%～24.5%无严重淬灭的样品,用液闪直接测量并根据外标法的淬灭校正曲线计算氚活度浓度,相对偏差在-6.35%～4.41%,基本可满足核设施氚常规监测的要求。     

固相萃取-液闪测量快速测定土壤样品中铅-210

利用浓硝酸加热浸取富集土壤样品中的铅,利用铅特效树脂吸附、柠檬酸溶液解吸,采用ICP-AES测量铅的化学回收率,液闪谱仪测量铅-210的活度浓度,建立了一种土壤样品中铅-210的快速分析方法。当土壤样品用量为1.0 g,测量时间为60 min时,方法的探测下限为24.8 Bq/kg,方法精密度为4.8%,加标回收率范围...     

液闪法提高~(32)P计数效率的研究

对 32 P的切仑科夫计数法及液闪测量作了比较 ,同时对于不同样品瓶和闪烁液对 32 P计数效率的影响进行了实验比较 ,指出提高 32 P测量效率的途径     

用Klein-Elsler法测量~3H、~(125)I双标记样品的条件选择

~3H和~(125)I是目前在生物学和医学中使用相当广泛的核素。用液体闪烁测量法测~(125)I近来也有很大发展。由于~(125)I标记化合物在一般实验室中都可制备,并且碘标记化合物可以达到较高的比放射性。故使用~3H、~(125)I双标记样品具有操作简便、费用低廉的优点。 我们采用Klein-Elsler法,利用计算Klein-Elsler值,以该值最大的一组测量道为分离效率最佳的双标记测量道。然后根据双标记样品在每一道的计数和每一种核素在两道的计数比值来求出两种核素各自的放射性大小。     

10Be/9Be标准样品的制备和加速器质谱测量

采用同位素稀释法由¹⁰Be标准参考物质SRM4325制备系列 ¹⁰Be/⁹Be标准样品,在北京HI-13串列加速器的AMS系统上对该系列标准（n(¹⁰Be)/n(⁹Be)范围为2.68×10^-11~2.38×10^-12）进行测量。测量结果显示，n(¹⁰Be)/n(⁹Be)测量值与标称值呈良好线性关系，且归一化后的测量值与标称值吻合。该系列标准可用于北京HI-13串列加速器的AMS系统对地质环境样品中¹⁰Be/⁹Be绝对比值的准确测定。     

液闪法测氚的一些优化条件和质量检验研究

对液闪法测氚的一些影响因素进行了优化条件实验，通过比对及内部检验证明在优化的实验条件下液闪法测氚所得分析结果的平行性、重现性很好。所用标准源成分如与试样不同，将带来系统误差，应予修正。     

液闪效率示踪法校正效果的评价

本文评价了Aloka商品液闪仪效率示踪法dpm校正的效果。轻,中度猝灭校正效果理想,具有简便、实用和适用性广泛的特点。严重化学和颜色猝灭样品的校正结果分别随猝灭增加而向增大和减小的方向偏离,形成喇叭状曲线,文中对这一现象给出初步解释。     

Positive ion AMS with a single-stage accelerator and an RF-plasma ion source at SUERC

The new single-stage accelerator mass spectrometer at SUERC can also accept positive ions. Potential benefits of positive ion measurement with suitable ion sources are more convenient sample form, smaller sample size, a variety of available charge states and maybe new applications. We have begun with oxygen isotope analyses to demonstrate destruction of interfering molecules.     

Basic characterization of U: Determination of age and U content using sector field ICP-MS, gamma spectrometry and alpha spectrometry

The possibility to determine the age, i.e. the time since the last chemical separation, of ²³³U was studied using two fundamentally different measurement techniques: inductively coupled plasma mass spectrometry (ICP-MS) and gamma spectrometry. Moreover, the isotope ratio ²³²U/²³³U was measured using both alpha spectrometry and gamma spectrometry. For the two materials analysed, all measurement results were in agreement, i.e. consistent within the combined uncertainties. One of the materials was also measured using gamma spectrometry under field conditions. This measurement was also in agreement with the other results on this material.     

液闪谱仪对90Sr和90Y的测量方法研究

使用Sr-Spec树脂对⁹⁰Sr-⁹⁰Y进行分离后采用液闪谱仪对⁹⁰Sr和⁹⁰Y的效率刻度和猝灭校正进行了系统研究,确定了⁹⁰Y效率刻度所用化学回收率,考察了闪烁液种类、载体加入、烘干处理、放置时间、化学猝灭对⁹⁰Sr和⁹⁰Y效率刻度的影响及其校正方法。结果表明：GoldStar LT²闪烁液适用于⁹⁰Sr和⁹⁰Y的测量,⁹⁰Sr刻度源是否烘干和⁹⁰Y刻度源有无钇载体对切伦科夫效率刻度无影响;⁹⁰Y的效率刻度应在⁹⁰Sr-⁹⁰Y分离后10 h内完成,并且有无钇载体对⁹⁰Y的液闪测量效率无影响;⁹⁰Sr的刻度源应经过烘干处理,也应在⁹⁰Sr-⁹⁰Y分离后10 h内完成测量。当待测样品与效率刻度源的制备方法相同,且待测样品的SQP(E)值在偏离标准样品SQP(E)值8.9%范围内时,可直接使用相对测量法。     

An experiment on the radioactivity characteristics of the tritium contaminated metal sample

The radioactivity of ³H of metal samples from nuclear sites was analyzed by using a commercialized high temperature furnace and a liquid scintillation counter (LSC). The ³H activity of a sample was measured according to the duration of the high temperature combustion and the oxidation temperature. Basically, the recovery from the furnace was 90% for ³H, and the LSC had a counting efficiency of approximately 30%. HNO₃ was used as a trapping solution for ³H, and the scintillation cocktail was added for LSC measurement. The activity of the metal sample was increased till the combustion time of 60 min had elapsed and decreased continuously thereafter at 600 °C whereas most of radioactivity was extracted during the first 15 min at 900 °C. Also, the pre-treatment of the metal sample, which included a high temperature combustion and trapping, had the time required of at least 4 h at 900 °C. Finally, it was suggested that this high temperature combustion method could be applied to analyze the activity of the radioactive metal waste from nuclear power plants for the determination of its clearance.     

Effect of counting vials and scintillators on the detection of low-level 14C by liquid scintillation spectrometry

The low-level ¹⁴C detection efficiencies and background count rates of glass and commercially available copper-Teflon (C-T) vials have been determined. The C-T vials gave better results and their spectral characteristics were investigated using four different scintillators. The highest figure of merit was obtained using sample benzene with a butyl- PBD scintillator, confirming results reported in the literature. However, some undesirable characteristics of C-T vials have come to light. We have investigated and overcome the high benzene (sample) vapour loss and the between vials variable ¹⁴C spectral end point. These factors dictate that care as well as individual vial calibration is needed for their successful application to low-level ¹⁴C counting. The sample volume to background relationship determined for the C-T vials indicates that a 4 ml counting volume is near to optimal for low-level ¹⁴C detection.     

Determination of 125I impurities in [123I]labelled radiopharmaceuticals,by liquid scintillation counting: sensitivity of the method

Iodine-125 is a radioisotopic impurity “always” present in iodine-123, produced by nuclear reactions induced either on natural or “highly” enriched targets. Liquid scintillation counting is a very sensitive tool to determine low level impurities of both low energy electrons and photons in aqueous and organic solutions of radiopharmaceutical compounds. With this technique it was possible to determine, on commercial samples, that the content of ¹²⁵I was of the order of not less than 0.1% for ¹²³I produced via ¹²⁷I(p,5n) reactions and not less than 0.01% for ¹²³I produced via “highly” enriched ¹²⁴Xe(p,X) nuclear reactions.     

TOPO萃取色层分离-ICP-MS法测定土壤中痕量铀的同位素丰度比

为了测定土壤中痕量铀的同位素丰度比,对TOPO萃取色层分离环境样品中U的方法进行了探讨。通过对色层柱体积、吸附酸度、洗涤酸度,以及不同洗脱剂的条件实验,确定了分离流程。获得U的全程回收率为(98.1±1 5)%,对土壤样品中基体元素的去污因子为1 4×103～1 8×105。通过对不同丰度铀同位素标样的测量,确定了ICP MS测量铀同位素的质量偏倚系数。采用了扫描和跳峰两种数据采集方式,获得235U/238U的相对标准偏差优于1%,234U/235U,236U/235U,234U/238U和236U/238U的相对标准偏差优于5%。两种方式测量实际样品的结果吻合。     

放化分离-液闪测量联合分析核电厂废树脂中的^(55)Fe和^(63)Ni北大核心CSCD

建立了一种核电厂放射性废离子交换树脂中^(55)Fe和^(63)Ni的联合分析方法。将废树脂样品经芬顿氧化消解后,先用氢氧化钠沉淀法沉淀^(55)Fe和^(63)Ni,再用阴离子交换树脂联合丁二酮肟沉淀对杂质离子进行分离纯化,纯化后用液体闪烁计器测量。本方法对废树脂中^(60)Co、^(65)Zn、^(54)Mn等干扰核素的去污因子均大于10^(3)。本方法对^(55)Fe和^(63)Ni的平均化学回收率分别为86%和90%,对废树脂中^(55)Fe和^(63)Ni的检测限分别为5.7 Bq/g、6.8 Bq/g。用加标样品对分析方法进行验证,预期值和测量值的偏差小于±10%。实验测得某核电厂一组一回路实际废树脂样品中^(55)Fe和^(63)Ni的平均活度浓度分别为(76.2±1.4)kBq/g和(120.0±5.1)kBq/g。