液闪计数中活度标准化的TDCR方法

本文描述液体闪烁计数中放射性活度标准化的一种新方法。该方法以三重对两重符合计数率之比(TDCR)作为效率变化的参量,外推符合计数率曲线到TDCR=1,直接地得出样品活度的接近值。文中给出它的原理、效率计算和理论不确定度估计。对氚水的测量,在NBS标称值的总测量不确定度±0.63％内一致。     

氚化水放射性活度的绝对测量

液体闪烁计数器具有无自吸收、制源简单、操作简便等特点,测量氚化水具有一定优势。利用液闪CIEMAT/NIST方法和三双符合比(TDCR)方法校准氚化水的比活度,旨在为氚化水标准物质的研制提供定值手段。以54 Mn作为示踪核素应用CIEMAT/NIST方法标准化氚化水比活度,合成标准不确定度为0.80%。液闪TDCR方法应用装配有3个光电倍增管的计数器,根据测量的符合信息直接计算得到探测效率,绝对测量氚化水比活度,合成标准不确定度为0.66%。应用这两种方法测量了同一组氚化水淬灭系列源,测量结果 En数检验满意。     

液闪TDCR测量装置研制

介绍了新建液闪活度绝对测量装置,该装置应用液闪三管两管符合比（TDCR）测量原理对β放射性核素活度进行测量。装置由3个光电倍增管及自制的散焦分压线路组成。通过改变光电倍增管的聚焦来改变探测效率,测量了³H放射源活度并进行了不确定度分析及讨论,TDCR测量结果与标定值在0.9%内符合,合成标准不确定度为0.6%（k=1）。     

液闪三双符合比方法测量~(99)Tc放射性活度

液闪三双符合比(TDCR)方法采用3个光电倍增管对称放置的液闪计数器,利用三管符合和三对两管符合的计数计算液闪探测效率,从而得到放射性活度,不需要使用标准源对仪器进行效率刻度,是一种放射性活度绝对测量方法。由于具有无自吸收、制源简单、操作简便、一致性好等优点,已广泛应用于纯β衰变核素放射性活度的测量。介绍了液闪TDCR方法的基本原理和液闪TDCR活度测量装置,并绝对测量了纯β衰变核素99Tc放射性活度,测量不确定度小于0.3%。     

FH1915低本底液体闪烁计数器

本文介绍专为测量低水平样品而设计的带有反符合屏蔽的双管符合型液体闪烁计数器。装置对5ml~(14)C标准源的测量效率为76.3％,对5ml糖炭溶液的测量效率为76.8％,本底为0.40±0.02计数/min,优值为14550。对20ml~8H标准源的测量效率为52.6％,本底为1.11+0.02计数/min,优值为2492。测量氚水样时,采用TritonX-100乳化剂直接测水,18ml样品中含有6ml氚水,测量效率为21％,本底为0.68±0.02计数/min,1000min的灵敏度为2.7Tu。     

液闪TDCR方法测量55Fe核素活度

为准确测量⁵⁵Fe核素活度,本研究采用液闪三双符合比(Triple-to-double Coincidence Ratio,TDCR)方法,首先根据⁵⁵Fe的核衰变与原子壳层数据,应用随机原子重排模型计算得到⁵⁵Fe在闪烁液中的电子沉积谱,其次基于自由参数模型计算单能电子在液闪中的计数效率,然后对所有沉积电子的效率进行求和得到⁵⁵Fe的总效率曲线,最后通过实验测量TDCR值,并结合总效率曲线导出实验计数效率,从而实现⁵⁵Fe活度的绝对测量。实验观测到光电倍增管(Photomultiplier Tube,PMT)量子效率非对称效应,各样品的修正因子在1.001～1.005之间。⁵⁵Fe比活度测量结果为94.15 kBq·g-1,相对标准不确定度为0.45%。结果表明：液闪TDCR方法测量⁵⁵Fe可得到较低的相对标准不确定度。液体闪烁计数器对⁵⁵Fe具有较高的探测效率,两管符合逻辑相加效率达到63%以上。考虑PMT量...     

TDCR法测量氚水活度比对

本文介绍了国防科技工业电离辐射一级计量站与中国计量科学研究院电离辐射所进行的氚水比对实验。详细说明了比对采用的2套液闪TDCR装置的结构以及电子学线路组成。对比对方法、比对结果以及不确定度评定进行了说明。通过比对室验,验证了2套TDCR装置测量结果的一致性。比对结果表明,国防电离辐射一级计量站与中国计量院电离辐射所氚水比活度测量结果偏差为0.24%。     

新型氚蒸馏装置的研制及性能验证

为提高硅胶吸附法监测环境空气中氚的样品前处理效率,采用铸铝加热方式结合温度自动控制技术,研制了一种用于环境硅胶样品自动化氚水蒸馏的装置。经实验验证,该装置选择250℃的加热温度,15 min的蒸馏冷凝收集时间为硅胶吸附氚化水的最佳解析条件,此时对硅胶中氚化水的平均回收率大于99%,氚记忆效应小于0.2‰,100 g饱和硅胶样品能解析水7～10 ml,满足液闪测量要求,研制的氚水蒸馏装置较以往装置蒸馏效率提高了近3倍,能耗减少约77%。     

SPE固体电解质氚水浓集装置及其应用

简述了SPE固体聚合膜氚水自动电解浓集装置的工作原理，介绍了在研制该装置中所进行的实验与工作进展，用SPE氚水电解浓集装置处理。IAEA第6次低水平氚国际比对样品(TRIC2000)，取得了满意的测量结果。     

液体闪烁核活度计量仪

本文描述用液体闪烁计数法直接测定α、β发射体溶液放射性活度的计量仪器。该仪器包括三个光电倍增管的符合探测器和三个输出计数道;以三重对两重符合计数率之比(TDCR)为猝灭参数,通过外推效率曲线至TDCR=1直接得到核素的活度。该仪器用于放射性活度绝对测量至少有两个突出的优点:1.精确度较高,对~3H、~(63)Ni和~(14)C等多种β、α核素其总测量不确定度(3σ)在0.5—1.5％;2.操作简便,测量迅速。     

Low-Background Measurements of 22Na in Natural Waters of Krasnodar Krai

Gamma spectrometers with 100 × 100 mm NaI(Tl) and 200 × 100 mm CsI(Tl) crystals for detecting annihilation radiation of ⁺ radionuclides are described. Two spectrometers are located in a surface laboratory and one underground, at a depth of 500 m of water equivalent, in Novorossiisk. The background characteristics and the detection efficiency are presented for different operating modes of the coincidence system and for samples with different mass. A coincidence scheme in which all events with coincidences of pulses in both crystals and energy released in each detector are detected, making it possible to raise the ²²Na detection efficiency by approximately 30%, was tested. The results of measurements of the ²²Na content in some natural waters in Krasnodar krai, including in mud volcanoes, are presented. They show large seasonal variations.     

环境大气氚的测定技术研究

文章分析环境大气中氚的来源，并描述环境大气氚浓度测量系统的组成与测量原理。研究了累积氚取样装置中催化炉的催化温度和气体流速对催化效率的影响、冷阱冷却温度对氚回收率的影响，刻度了氚电解浓集装置的回收率，在此基础上测定了某核设施周围环境大气氚浓度。结果表明：在催化温度为350℃、催化效率为98%、电解浓集装置平均回收率为54%的实验条件下，本测试方法可高灵敏度地测定特定范围内外环境低水平大气氚浓度变化，探测下限可达0.1Bq/m³。     

Comparison of tritium measurement techniques for a laser cleaned JET tile

Over the last 7–8 years, two quantitative analyzing methods—accelerator mass spectrometry (AMS) and full combustion (FC) followed by scintillation detection have been applied for determining the tritium activity concentrations in JET divertor tiles. These methods have two main differences – the range of detection and the spatial resolution – and are thus complementary. However, these differences can also complicate the comparison of the two techniques for typical JET divertor samples. Therefore a cross comparison exercise for tritium measurements was performed between the two methods using specially produced identical standard samples. The cross comparison measurements were performed firstly on the identical standard samples and were extended then to selected samples from the JET divertor tile (laser treated and non-treated samples from tile 14ING3B exposed in 2001–2004). The results obtained by AMS and FC agreed within an error limit of 10% for the standard samples and of 18% for the JET divertor samples. The results of this comparison study provided also useful information concerning the efficiency of tritium removal from the plasma facing surface of the divertor tiles by means of laser ablation.     

Effects of internal bremsstrahlung of tritium β-decay and surface roughness in the BIXS method

We have studied the effects of the internal bremsstrahlung of tritium β-decay, sample surface roughness and tritium content as well on the tritium β-decay induced X-ray spectroscopy (BIXS) for tritium measurements based on Monte Carlo simulations. The Knipp-Uhlenbeck-Bloch theoretical model was adopted for the internal bremsstrahlung. It is found that the contributions of internal bremsstrahlung of tritium β-decays are approximately 30%, 10%, 4% and 2% of the corresponding external bremsstrahlung for C, Ti, Mo and W materials, respectively, and the sample surface roughness may cause an error of several percent in the BIXS method if the surface roughness of a sample is in a reasonable range. Moreover, the effect of tritium content should be taken into account when a sample contains a large amount of tritium, otherwise, the tritium contents measured by the BIXS method will be underestimated, for example, by up to ∼15% for Ti metal.     

k_0-NAA样品测量架位自动调节和半参量化效率计算

设计了中子活化自动换样和架位精密调节系统。实现了任意衰变纲图的γ发射核在源-探测器为0～280mm范围内不同测量位置的效率测定,提出了解决k0法不同测量几何的效率归一以及级联符合校正的半参量化方法。对于源与探测器距离较远的位置(符合效应可忽略),采用有效作用深度进行效率计算;对于源与探测器距离较近的位置(符合效应不能忽略),采用实验测得不同位置的效率比进行计算。     

基于铝箔封装碳酸锂探测片产氚率测量的液闪样品制备方法

氚增殖包层中产氚率的测量是聚变核能系统中需要研究的重要问题之一,本文开展了用于产氚率测量的Al箔封装碳酸锂探测片液闪样品制备化学处理方法的研究。结果表明,首先采用氢氧化钠溶液来溶解Al箔,然后再用盐酸溶解碳酸锂探测片的溶解方式,能制成透明度高且无分层的液闪样品。为了提高测氚计数效率和保证样品兼容性,对20 m L的标准液闪样品,闪烁液体积应至少取12 m L,同时还应将液闪样品保持在10-20°C范围进行储存和测量。