LabSOCS在级联辐射引起的符合相加修正上的应用

目的 探索LabSOCS无源效率刻度在级联辐射引起的符合相加修正上的应用。方法 利用LabSOCS无源效率刻度软件生成4个标准源的模拟效率曲线,使用实验室高纯锗γ能谱仪测量这4个标准源,在活度分析时计算符合相加修正因子,对测量结果进行符合相加修正,将修正后的放射性活度与证书活度进行比较,并使用GB/T 28043-2019/ISO 13528∶2015中能力评定统计量E_n值评定。结果 测量结果活度值与证书活度值进行比较,符合相加修正后偏差绝对值范围在0.14%~3.87%,且统计量E_n值绝对值均<1。结论 LabSOCS在级联辐射引起的符合相加修正上的应用效果较为理想,符合相加修正后的活度值与证书活度值偏差不大,其能力评定结果是合格的。     

核电站周围环境样品的γ谱分析方法

本文作介绍了用锗γ谱仪分析核电站周围低水平环境样品中人工核索和天然核素时所建立的方法。主要描述丁潜仪的刻度:有笑γ符合相加校正和样品舟一旺收曼王的考虑.谱仪探测限计算；一些核素特征蜂面积的计算方法和注意事项；以及误差分析与估算等,提出了充分利用谱数据计算²²⁶Ra、²²⁸Ra、²²⁶Th等核素含量以减少误差的方法。     

γ能谱无源效率模拟中食品样品成分分析研究

目的 通过分析常见食品的成分,利用无源效率刻度与有源验证相结合的方法,为食品γ能谱无源效率刻度分析推荐参考成分。方法 对全国食品放射性污染监测中30种常见食品样品进行分析,统计出粮食类和蔬菜类的参考成分,结合白藜麦标准源的自身参数,应用LabSOCS进行白藜麦标准源不同成分的无源效率模拟,计算白藜麦标准源测量活度与其证书活度的相对偏差并进行分析。结果 30种 食品样品的检测结果表明,C、H、O、N、S这5种元素占食品组成的77.0% ~ 93.7%, 是食品的主要成分。将白藜麦自身成分和粮食类参考成分应用于白藜麦标准源的无源效率模拟,进行活度计算,与其证书活度的相对偏差绝对值分别在0.37% ~ 5.86%和0.38% ~ 5.87%。结论 白藜麦自身成分和粮食类参考成分应用于白藜麦标准源的无源效率模拟,计算的测量活度与标准源证书活度的相对偏差基本一致,若使用γ能谱无源效率模拟测量未知成分的食品样品且不便进行食品样品成分分析时,特别是在应急情况下,可参考使用本研究得到的参考成分。     

大面积屏栅电离室分析环境样品中多种α核素的方法

目的 建立应用屏栅电离室谱仪同时分析样品中多种α核素的方法。方法 超声分散和真空干燥系统制备大面积样品源,应用大面积标准薄源和钚标准面源对屏栅谱仪测量条件进行优化,建立能量和效率刻度曲线,采用铀钍天然系矿石标准物质(GBW04127)对方法的准确性进行验证。结果 Np、Pu和Am大面积标准薄源的能量曲线非线性<0.2%,线性良好。²³⁷Np、²³⁹Pu、²⁴¹Am的半峰宽分别为112、84和106 keV。大面积标准薄源的探测效率均值为31.2%。分析铀钍天然系矿石标准物质比活度测量值与标准值相一致。用该方法测得某铀矿石中²³²Th、²³⁸U、²³⁰Th、²³⁴U/²²⁶Ra、²¹⁰Po、²²²Rn和²¹⁸Po,比活度分别为5.3、3.8、35.6、21.4、27.0、19.6和11.1 Bq/g。结论 该方法能够快速分析环境样品中的多种α核素,适合低水平放射性环境样品的α谱分析。     

水样品放射性核素γ能谱分析的比对与评价

目的 通过在重点实验室间开展γ能谱测量分析比对活动,改进水样品的γ能谱分析技术。方法 参加中国计量科学研究院组织的水样品中γ能谱测量分析比对。样品中²³⁸U、 ²²⁶Ra、²⁰⁸Tl、²²⁸Ac、⁴⁰K、²⁴¹Am、¹³⁷Cs、⁶⁰Co被检出。为分析比对结果,2015年又采用新制备的水标准源重新进行了效率刻度,并且采用了1台新购进的γ能谱仪（BE5030）重新测量了比对样品。结果 比对样品3次测量结果与主导实验室参考值的分析比较,发现采用γ能谱仪（BE5030）测量分析的结果较好,特别是天然核素结果,与参考值的最大E_n值仅为0.71。结论 宽能高纯锗γ能谱仪（BE5030）在天然放射性核素的测量分析方面优势明显,并且由于其探测器的结构特点,使得其在低能区本底干扰更少。此次比对改进了本实验室样品测量分析的准确性,取得了良好的效果。     

便携式γ能谱仪快速鉴定低放射性活度贫铀

目的 探索便携式γ能谱仪快速鉴定低放射性活度贫铀可行性和所需的基本条件。方法 取5 g贫铀样品,使用高纯锗γ能谱仪进行分析,鉴定核素种类,计算核素百分含量。运用便携式γ能谱仪,对同一批次样品鉴定,样品质量为1 g,模拟战、现场条件,按不同比例加入0~5 g普通泥土,密封,测量距离为1~5 cm,能谱采集时间为1~10 min,结果以样品中²³⁸U、²³⁵U核素活度表示,将其换算成比活度,计算²³⁵U在铀同位素中的百分含量,若小于0.718%,则确定为贫铀。结果 便携式γ能谱仪检测出²³⁸U的条件是样品质量≥0.5 g,测量距离0.5~5 cm;但检测出²³⁵U的条件必须是质量≥1 g,测量距离≤1 cm。在可同时检测出²³⁸U与²³⁵U时,经计算²³⁵U百分含量均小于0.718%,判定为贫铀样品。结论 便携式γ能谱仪可快速对低放射性活度贫铀获得能谱,鉴定核素种类,结论与高纯锗能谱仪、α谱仪和ICP-MS一致。     

呼和浩特市城区表层土壤和环境辐射水平调查

目的 测定呼和浩特市城区表层土壤中天然和人工放射性核素比活度,测量环境放射性水平,评估其对居民产生的健康风险。方法 采用高纯锗γ能谱仪对呼和浩特市城区48个表层土壤样品进行了放射性核素的测定;用环境γ剂量率仪测量了环境辐射水平;与世界和我国土壤中放射性核素比活度平均值进行了比较,通过联合国原子辐射影响科学委员会和相关文献推荐的方法估算了居民受照剂量。结果 呼和浩特市表层土壤样品中²³⁸U、²³²Th、²²⁶Ra、⁴⁰K和¹³⁷Cs的比活度平均值分别为（29.29±12.95）、（39.33±4.34）、（29.77±3.21）、（650.49±62.21）、（1.62±1.53） Bq/kg;测量的空气吸收剂量率均值为（86.32±11.92） nGy/h,该地区居民受到室外γ辐射所致年有效剂量为79.27 μSv/年。结论 呼和浩特市表层土壤中天然放射性核素比活度和环境辐射处于正常本底水平,对居民造成的健康风险非常低。     

蒙特卡罗方法在γ谱测量中效率刻度的研究

目的 建立探测器的无源效率刻度方法。方法 利用¹³⁷Cs点源,对HPGe和NaI晶体尺寸进行调整以获得正确的探测器几何参数,基于BOMAB体模的数学模型,在γ线能量126～1836 keV范围内,采用蒙特卡罗方法,结合核应急情况下体内核素探测几何模式,分别计算了HPGe探测器和NaI探测器对BOMAB体模的计数效率,根据计算结果拟合出相关的效率曲线和函数。结果 通过拟合函数计算获得的探测效率与应用蒙特卡罗算法得到的探测效率一致性较好。对于NaI探测器,残差为-19%～18%;对于HPGe探测器,残差为-11%～17%。结论 根据BOMAB体模的数学模型应用蒙特卡罗方法对便携式γ谱仪进行无源刻度省时、省力,具有较强的可操作性,是一种非常方便的谱仪校准方法。     

测量125I放射性活度的相加峰符合法

本文介绍测量¹²⁵I放射性活度的相加峰符合法。通过测量¹²⁵I衰变放射的27.5kevx射线飘135.5keVγ 射线单一峰计数率及这两种射线相加峰计数率,可准确的计算出¹²⁵I源的放射性活泼。本法与测量¹²⁵I活度的相对法比较,具有使用方便,不需要对计算系统进行刻度,以及测量结果几乎不受样品源体积、源在探测器中的位置和样品源容器类型的影响等优点,是核医学和辐射防护中测量¹²⁵I放射性活度的较为理想的一种方法。     

2015年土壤比对样品放射性γ能谱分析

目的 分析实验室比对样品中放射性核素比活度。方法 通过参加2015年中国疾病预防控制中心辐射防护与核安全医学所组织的全国放射性核素γ能谱分析比对,利用高纯锗（HPGe）γ能谱仪测量样品,分别采用效率曲线法和相对比较法分析土壤比对样品中放射性核素²³²Th、⁴⁰K和¹³⁷Cs的比活度。结果 利用两种分析方法求得结果与参考值的相对偏差均 < 5%,相对比较法获得的测量值与参考值的相对偏差 < 4%。结论 效率曲线法和相对比较法均可以完成比对样品中放射性核素的测定,且相对比较法优于效率曲线法。h     

Determination of 198Au X-rays emission probabilities

This work describes the measurements of the K X-ray and gamma-ray emission probabilities per decay of ¹⁹⁸Au performed at the Nuclear Metrology Laboratory (LMN) at the IPEN, São Paulo. The radioactive sample was obtained by means of ¹⁹⁷Au(n, γ)¹⁹⁸Au reaction irradiating an Au foil in a thermal neutron flux near the core of the IPEN 3.5 MW research reactor. The activity of samples was determined in a 4πβ–γ coincidence system, setting the gamma window at the 411.80 keV total energy absorption peak. The same samples were measured in two different spectrometers: a HPGe planar spectrometer with Be window, suitable for measurements in the low energy range and a coaxial REGe spectrometer. Both spectrometers were previously calibrated in a well defined geometry by means of standard sources calibrated in a 4πβ–γ coincidence system. MCNP4C Monte Carlo code was used for simulating the REGe spectrometer calibration curve, and a new version of code ESQUEMA was adopted for simulating the detection processes in the coincidence system, in order to predict the efficiency extrapolation curve.     

伽玛能谱仪分析226Ra的部分影响因素的研究

目的通过对γ能谱分析226Ra的部分影响因素进行有针对性的测量, 进一步优化γ能谱针对226Ra活度的分析方法, 以求得到更为精准的测量结果。方法利用实验室高纯锗γ能谱仪, 开展样品密封时间的跟踪测量、铅室本底波动影响测量, 分析方法与子体核素特征γ射线能峰选择等方面研究。结果样品密封12 d后, 226Ra-222Rn衰变系基本达到平衡。测量屏蔽铅室本底中222Rn昼夜波动明显且无明显规律, 向铅室内注入氮气的方式可降低或避免本底波动影响。针对31份密封23 d后测量的土壤样品, 采用效率曲线法分析的结果表明, 351.9 keV能峰计算的226Ra结果普遍高于609.3 keV能峰, 高出的比例范围为8.0%～20.7%;采用相对比较法分析的结果表明, 两能峰偏差的比例范围为-4.1%～10.3%。结论在样品密封后第12天进行测量时, 建议考虑由衰变系平衡因素引入约4%的不确定度。通过铅室内注入氮气避免本底波动时, 须注意铅室内腔体积与氮气注入流量的匹配关系。采用效率曲线法分析226Ra活度时, 214Bi(609.3 keV)能峰存在级联符合相加影响, 应避免选用;采用相对比较法...     

Measurement of natural radionuclides in phosphgypsum using an anti-cosmic gamma-ray spectrometer

Gamma-ray spectrometry measurements have been carried out to determine the activity of natural radionuclides in a phosphogypsum sample included in a specific tight container. The gamma spectrometer includes an N-type coaxial high-purity germanium (HPGe) detector equipped with an anti-cosmic system. This measurement required the determination of linear attenuation coefficients of phosphogypsum to calculate self-absorption correction between efficiency calibration conditions and measurement ones. The results are given for the three natural chains and for ⁴⁰K, in term of specific activity/g of dry material, ranging from a few Bq kg⁻¹ to a few hundreds Bq kg⁻¹. The equilibrium within the different families and the ²³⁵U/²³⁸U ratio are discussed.     

Correlation effect in activity measurement of 59Fe

Correlation effects due to the cascade transition of gamma-rays with gates on the relevant peaks have been studied in activity measurement of ⁵⁹Fe using the bi-dimensional coincidence counting method. Extrapolation curves were obtained at three gamma gates of 1099.2 keV, 1291.6 keV, and that covering both photo-peaks by a computer discrimination method. Of these extrapolation curves, only that obtained at (950–1350) keV gamma gate shows a linear variation, but those of two single gamma gates are not linearly varied in the high efficiency region. This non-linearity obtained at the gamma gate of 1099.2 keV photo-peak was caused by the correlation effects due to 1–3 coincidence relation via unobserved 192 keV gamma-ray transitions.     

Standardization of Sn-113

The radionuclide ¹¹³Sn is a quasi-monoenergetic gamma emitter often used in the efficiency calibration of gamma spectrometers in the energy region around 390 keV. This paper presents the results of the standardization of this radionuclide by three methods: integral (4π−γ) counting with a well-type NaI(Tl) detector, liquid scintillation counting applying the CIEMAT-NIST method and 4π coincidence counting (conversion electron-X) with a digital coincidence system.     

Standardization of 99mTc and 99Mo by the use of a 4πβ−4πγ counter

Technetium-99m is widely used for many diagnostic investigations in nuclear medicine, thus the standardization of this nuclide is important. In classical 4πβ?γ coincidence counting of ^99mTc, the steep slope of the efficiency function and the large extrapolation range may cause a large measurement uncertainty. In order to overcome these difficulties, we apply the 4πβ+4πγ sum counting technique for the standardization. Furthermore, we adopt both the 4πβ?4πγ coincidence counting method and the 4πβ+4πγ sum counting technique for the standardization of its parent nuclide ⁹⁹Mo. High efficiencies for both nuclides were easily achieved by the use of our 4πβ?4πγ counter. All the results were consistent with the reference value obtained by the conventional method obtained by NMIJ.     

X-ray true coincidence summing correction in Genie 2000

An analysis algorithm to correct for the γ-ray true coincidence summing effects for radionuclides decay by cascading photons was developed and implemented in Canberra's Genie 2000 software in 2001. It has been extended to correct for true coincidence summing effects from low energy γ-rays, KX-rays from electron capturing and internal conversion, and the 511 keV positron annihilation photons. Validation of these extensions shows significant improvement in Genie 2000's true coincidence summing correction capability and the accuracy of nuclide activity measurement.     

斑马鱼计算模型构建与相关剂量系数的计算

目的 为了评估核电对周围环境的辐射影响,通过模式动物精细化建模,构建剂量评估模型并确定相关剂量系数。方法 针对核电液态流出物辐射危害评估中的重要水生模式生物斑马鱼,建立用以剂量估算的斑马鱼含有内部骨骼和内脏器官的几何模型。使用蒙特卡罗方法,以核电液态流出物及周围环境监测中常见的³H、⁴⁰K、⁵⁸Co、⁶⁰Co、¹¹⁰Ag、¹³⁴Cs、¹³⁷Cs 7种核素为源项,计算斑马鱼模型的内外照射剂量系数（DC）。结果 核素γ能量的高低决定了外照射剂量系数的大小。对内脏器官、骨骼和全身的外照射剂量系数比较显示,大部分核素内脏器官剂量系数高于全身剂量系数,⁵⁸Co的内脏器官剂量系数比全身高165%。本研究建立模型内照射剂量系数较大,⁶⁰Co造成的内照射剂量系数是已有椭球模型剂量系数的2.6倍,说明内部材料的不同和粒子种类不同的选择会影响能量沉积。结论 对模式生物进行精细化建模比较重要。精确评估模式生物器官剂量系数,有助于评估非人类物种的辐射效应。     

Activity determination of simultaneously chemical and color quenched samples using a liquid scintillation counter

Activities of simultaneously chemical and color quenched samples can be accurately determined by using a combination of two external standard techniques, these are, an external standard quenching correction curve and a double external standard relation curve. The latter curve is used for estimating the degree of contribution of chemical and color quenching for the samples. All that is required for this technique are chemical and color quenched standard sample sets for the nuclide to be radioassayed. The technique has been applied to the cases of ³H and ¹⁴C, and found to be very practicable with the aid of computerized data processing.     

Standardization of 241Am by digital coincidence counting,liquid scintillation counting and defined solid angle counting

The nuclide ²⁴¹Am decays by alpha emission to ²³⁷Np. Most of the decays (84.6%) populate the excited level of ²³⁷Np with energy of 59.54 keV. Digital coincidence counting was applied to standardize a solution of ²⁴¹Am by alpha–gamma coincidence counting with efficiency extrapolation. Electronic discrimination was implemented with a pressurized proportional counter and the results were compared with two other independent techniques: Liquid scintillation counting using the logical sum of double coincidences in a TDCR array and defined solid angle counting taking into account activity inhomogeneity in the active deposit. The results show consistency between the three methods within a limit of a 0.3%. An ampoule of this solution will be sent to the International Reference System (SIR) during 2009. Uncertainties were analysed and compared in detail for the three applied methods.