Performances of different efficiency calibration methods of high-purity-germanium gamma-ray spectrometry in an inter-comparison exercise

This study reports the performances of efficiency calibrations for high-purity-germanium gamma-ray spectrometry using the source-, Laboratory Sourceless Object Calibration Software(LabSOCS)-and ANGLE-based methods in an inter-comparison exercise. Although the results of LabSOCS and ANGLE for ^(241)Am emitting lowenergy gamma rays were not very satisfactory, all of the three efficiency calibration methods passed acceptance criteria. The results confirmed the reliability of the calculation codes ANGLE and LabSOCS as alternative efficiency calibration methods in high-purity-germanium gamma spectrometry. This study is likely to promote the further application of the ANGLE and LabSOCS calculation codes in radioactivity measurements.

The Maastrichtian-Danian in the SW Zagros Fold-Thrust Belt(S. Iran):An Integration of Planktonic Foraminiferal Biostratigraphy and Gamma-Ray Spectrometry

In this study, the Maastrichtian-Danian boundary was measured and sampled in two stratigraphic sections, the north and south flanks of the Dehnow anticline in Coastal Fars, Southern Iran. This boundary was also investigated in the drilled exploratory well-1 in the same region. The lithology of the Maastrichtian-Danian deposits consists of glauconitic, phosphatic argillaceous limestones and marlstones. 30 genera and 77 species of planktonic foraminifera have been determined. The recognized biozones are the Gansserina gansseri Interval Zone, and the Contusotruncana contusa Interval Zone, which indicates latest Campanian to middle Maastrichtian age for the upper part of the Gurpi Formation. In addition, the Eoglobigerina edita(P1) Partial Range Zone, Praemurica uncinata(P2) Lowest Occurrence Zone, Morozovella angulata(P3) Lowest Occurrence Zone and Globanomalina psudomenardii(P4) Taxon Range Zone represent a Danian to Thanetian age for the lower part of the Pabdeh Formation. From the absence of the Abathomphalus mayaroensis Interval Zone, Pseudoguembelina hariaensis Interval Zone, Pseudotextularia elegans Interval Zone, Plummerita hantkeninoides Interval Zone, Guembelitria cretacea(P0) Partial Range Zone and Parvularugoglobigerina eugubina(Pα) Total Range Zone, it can be deduced that there is a paraconformity across the Maastrichtian–Danian boundary in the studied area, this hiatus encompassing the late Maastrichtian and the earliest Danian. Danian deposits from the study area contain reworked glauconitized macrofossils, planktonic and benthic foraminifera of the Cretaceous. The obtained surface gamma-ray spectrometry logs resemble the exploratory well-1 gamma-ray wireline log.

Investigating the minimum detectable activity concentration and contributing factors in airborne gamma-ray spectrometry

In this study,the theory of minimum detectable activity concentration(MDAC)for airborne gamma-ray spectrometry(AGS)was derived,and the relationship between the MDAC and the intrinsic effi-ciency of a scintillation counter,volume,and energy res-olution of scintillation crystals,and flight altitude of an aircraft was investigated.To verify this theory,experi-mental devices based on NaI and CeBr 3 scintillation counters were prepared,and the potassium,uranium,and thorium contents in calibration pads obtained via the stripping ratio method and theory were compared.The MDACs of AGS under different conditions were calculated and analyzed using the proposed theory and the Monte Carlo method.The relative errors found via a comparison of the experimental and theoretical results were less than 4%.The theory of MDAC can guide the work of AGS in probing areas with low radioactivity.

Uranium Series Disequilibrium and Precision Measurement of Radionuclides Activity in Sediment Sample Using Low Background Gamma Spectrometry

Low background gamma spectrometry was used to measure the radionuclides activity of 238U, 232Th, and 235U series as well as 40K and 137Cs in a sediment sample. The goal of the study was to measure the 238U (63.3 keV peak of 234Th;1001 keV peak of 234mPa) and 235U (143.76 keV, 163.33 keV, and 205.31 keV peaks) activity by low background gamma spectrometry in sediment sample. 235U activity in environmental samples is difficult to accurately measure by gamma spectrometry due to its low abundance in nature and low gamma line intensities at 143.76 keV, 163.33 keV, and 205.31 keV. We have shown that by using low background gamma spectrometry, it is possible to accurately measure the 235U activity in sediment samples. The 235U activity was measured without using the major peak of 185.7 keV (Iγ = 57.2%) which requires interference correction from 186.21 keV of 226Ra. 226Ra activity was determined by measuring 222Rn daughters (214Pb and 214Bi). The precision and accuracy of the gamma activity measurement in the sediment sample were verified by using the HPGe detectors with Certified Reference Material (CRM) Irish Sea Sediment (IAEA-385). The results obtained for the 63.33 keV energy line of 234Th are compared with the 1001 keV energy line of 234mPa. The values of 238U and 235U activities, as well as 40K, 137Cs, and 226Ra, agreed with the certificate values of CRM. The results show that the 238U is in equilibrium with its daughters (234Th, 234mPa, and 210Pb). 232Th is also in equilibrium with its daughters (228Ra, 212Pb, 212Bi and 208Tl). 235U/238U activity ratio of 0.046 ± 0.007 in the sediment is constant in nature but fluctuates due to geological processes. A value of 0.055 ± 0.008 was found in our sediment sample.

基于数字脉冲成形技术的HPGe γ谱仪系统研究

为满足高能量分辨率γ能谱测量要求,设计了基于数字脉冲成形技术的HPGeγ谱仪系统。该系统由前端电路、数字信号处理模块和上位机软件3部分组成,实现了8 192道能谱测量。本文对前端电路的设计及数字脉冲成形参数的选择进行了介绍,并用^(60) Co、^(134) Cs、^(137) Cs和^(152) Eu源对该系统进行了初步测试。测试结果表明,基于数字脉冲成形技术的HPGeγ谱仪系统对1 332keV能量峰的能量分辨率为1.8keV;^(152) Eu特征能量峰与相应道址的线性拟合参数R^2=0.999 993。该系统可满足高能量分辨率γ能谱测量要求。

标准物质对HPGe γ谱仪测定环境放射性核素^(210)Pb和^(137)Cs的影响

为评价不同标准物质效率刻度对环境放射性核素测定准确性的影响,应用具有无源效率刻度(LabSOCS)功能的高纯锗(HPGe)γ谱仪,比较用褐土、黄壤、黄土和紫色土4种土类与供测试土壤栗钙土作为标准物质进行效率刻度获得的210Pb和137Cs比活度之间的差异。选用的5种土类为标准物质对测试土壤中210Pb测定的准确性有显著影响,这是由于标准物质中能够显著影响210Pb测定结果的一组元素Si、Fe和Na,尤其是Fe含量相对于测试土壤存在很大差异(相对差异在94%～166%之间)。不同标准物质对土壤中137Cs测定准确性的影响较小,这是由于不同标准物质中与137Cs比活度显著偏相关(P<0.01)的O和Na含量差异较小(小于10%)。结果表明:标准物质对137Cs测定影响不大,选择与测定样品的化学元素相近的标准物质进行效率刻度,可以提高环境样品中210Pb测定的准确性。

就地HPGeγ谱仪偏差的实验验证

在某放射性污染场选取一块地势平坦区域,就地HPGeγ谱仪现场测量,并采样进行实验室γ谱仪分析。两种结果比较,验证了就地HPGeγ谱仪测量结果偏差。实验表明,相对于样品的实验室分析结果,就地HPGeγ谱仪对^(241)Am、^(137)Cs、^(60)Co、^(152)Eu、^(155)Eu的测量结果偏差分别为-22%、-2%、8%、-20%、11%。

就地HPGe γ谱仪“比值法”核素深度分布测量

建立了就地HPGeγ谱仪对地表层土壤中152Eu深度分布直接测量的"比值法"技术。实验结果表明,放射性污染场8个实验点152Eu深度分布均近似呈指数函数形式,"比值法"现场测量结果相对于采样-实验室γ谱仪分析结果的最大偏差为-33.8%。这说明,就地HPGeγ谱仪"比值法"152Eu深度分布测量技术是可行的。

HPGe γ 谱仪对体源的效率与源高度近似关系的验证

用γ谱仪分析环境样品时，常遇到样品量或样品盒高度与原刻度时的不一致，如能用事先确定的体源效率与源高度的关系对刻度系数作适当修正，则是一种实用、简便的近似方法。本实验室曾用实验方法对ＨＰＧｅγ谱仪（美国ＯＲＴＥＣ公司产品），对圆柱形体源的效率εｖ与体源高度Ｈｓ得到了一个拟合公式εｖ＝１／（ｃ１＋ｃ２Ｈｓ＋ｃ３Ｈｓ２）（Ｈｓ在１０～７５ｍｍ）。本文介绍了用实际的土壤样品对该经验公式进行实验验证的方法和结果。验证实验中，在杭州地区选取４个不同地点，用常规取样方法采集３个土壤样品和１个煤碴砖样品，制样后装入７５ｍｍ的聚乙烯盒内，得到４组高度由２５ｍｍ至７５ｍｍ不等的２０个圆柱形体源样品；ＨＰＧｅγ谱仪及仪器状态等实验条件与原实验保持一致，测量时间为４～１６ｈ不等；根据该ＨＰＧｅγ谱仪对不同高度土壤样品测得的不同能量γ射线的光电峰比活度的一致性，即比活度相对偏差来验证εｖ～Ｈｓ拟合公式。实验结果表明，对这４组样品，每组不同高度样品中不同能量γ射线的光峰比活度相对偏差的平均值最大为８．２％，一致性较好，可见，所得εｖ～Ｈｓ拟合公式在相应的实验条件下是可用的。

Validation of ²²⁶Ra and ²²⁸Ra Measurements in Water Samples Using Gamma Spectrometric Analysis

Radium isotopes can be analyzed by different analytical methods based on gamma spectrometric measurements or alpha spectrometry. An improved method was developed to determine radium isotopes from water using gamma spectrometry after radiochemical separation. The Radium was selectively extracted from acidified samples using co-precipitation procedure with iron hydroxide and followed by precipitation of radium as radium sulphate Ba(Ra)SO4. The precipitate Ba(Ra)SO4 was filtered through the Millipore filter paper, dried and weighed to calculate chemical yield. 226Ra and 228Ra activities were measured using low-background gamma spectrometry in water samples. Radium was pre-concentrated from environmental samples by co-precipitation with BaSO4. The amounts of 226Ra and 228Ra on the sample were obtained by gamma-ray spectrometry for the 351 keVγ-ray from 214Pb and for the 911 keV γ-ray from 228Ac, both in radioactive equilibrium with precursors, respectively. The accuracy, selectivity, traceability, applicability and Minimum Detectable Activity (MDA) of the technique were discussed. Also, the effect of physical and chemical characteristics of the water samples such as TDS, pH, soluble species, sulphate and bicarbonate that effect on the radium determination were taking into consideration. The method has been validated with a certified reference material supplied by the International Atomic Energy Agency and reliable results were obtained. The radiochemical yields for radium were 70% - 90% and recovery was 97% and 80% for 226Ra and 228Ra, respectively.

Study of the Opuntia ficus indica and Its Radioactive Potassium Content using the Gamma Spectrometry

Mexico is one of the largest producers of nopal （Opuntiaficus indica）. This ＂vegetable＂ is consumed on a daily basis by the Mexican population, being a source of food nutrients. Among its benefits, it is considered the content of potassium, which is essential for human life and health. In this study, it analyzes the content of potassium of the Mexican cactus （Opuntiaficus indica） grown in 5 different regions in the Mexican Basin, where 67% of the nopal is produced for human consumption. The used methodology is gamma spectrometry with Hyperpure Germanium detector （HPGe） and Multichannel Analyzer （MCA） with Maestro~ software. The results show interesting aspects on the concentration of potassium in the nopal. This concentration will primarily depend on： （a） the geological characteristics of the location where the nopal was grows; （b） that potassium concentrations may vary substantially from a region to another, with the same species of nopal as a reference and （c） that this concentration may also vary from one growing season to another.

HpGe γ谱测量铀矿样品中^(40)K结果比对

中核集团地矿事业部组织了"BRIUG IC-2016铀矿地质样品分析实验室间比对"活动,本实验室积极参与了^(40) K的比对,采用HpGeγ谱进行测量。同时,在实验室内部与X荧光光谱法、HR-ICP-MS测量方法比较,3种方法的结果高度一致。表明低本底γ谱法测定地质样品中^(40) K方便准确,测量结果是可信的。通过此次活动,了解到本实验室和其他实验室的测试水平差异,有助于提高本实验室的测试能力。

Study of the Potassium Content in Amaranth Protein Using the Gamma Spectrometry Technique

Amaranthus is a dicotyledonous pseudocereal and one of the new world’s oldest crops,having originated from Meso-America and was a major food crop of the Aztecs.Popularity in the cultivation and consumption of Amaranthus seed in the modern era began in the mid-1970s with the rediscovery and promotion of amaranth due to its superior nutritional attributes as compared to cereal grains.Amaranth plant has a high-quality protein,carbohydrates,unsaturated oil,squalene,dietary fiber,tocopherols,phenolic compounds,flavonoids,vitamins and minerals.The amaranth’s grain was collected at San Martin Pahuacan,Estado de Mexico,Mexico.The used methodology is gamma spectrometry with Hyperpure Germanium detector(HPGe)and Multichannel Analyzer(MCA)with Maestro software.The result shows a unique concentration of radioactive potassium content in the amaranth protein isolated from amaranth grains is 424.1 mg/100 g of amaranth protein.There is an excellent agreement between the amount of potassium determined by atomic absorption spectroscopy in our laboratory and the value obtained in this work using the Gamma Spectrometry Technique.

Calibration of the High Purity Germanium Gamma-Ray Spectrometer in CERT, ABU Zaria, Nigeria

Gamma-ray spectrometry is a very powerful tool for radioactivity measurements. The gamma-ray spectrometer laboratory in Centre for Energy Research and Training (CERT), Ahmadu Bello University, Zaria, Nigeria is accredited to perform measurements of radioactive content of samples collected from the environment, food chain or industrial products with the aid of a high resolution HPGe detector. For accurate gamma-ray spectrometry, certain measurements were considered;the efficiency of the detector was performed experimentally against energies within the range of 59.50 keV (241Am) to 2204.50 keV (226Ra) for the respective geometries of 1 - 6 cm. The sustained solid angle relations with respect to the inverse square of sample geometries from 1 - 6 cm were evaluated. Another main point of this work was focused on the efficiency at geometry of 5 cm with respect to the three selected energies: 661.60 keV (137Cs), 1173.2 keV (60Co) and 1332 keV (60Co) for the main axis, ten degree off main axis, forty five degree off main axis and ninety degree off the detector main axis. In order to verify optimum geometries in our laboratory for both short lived and long lived radionuclides analyses, the evaluation of efficiencies for the respective energies: 1173.2 keV (60Co), 1332.5 keV (60Co), 1764 keV (226Ra) and 2294 keV (226Ra) were plotted against geometries of 1 to 6 cm from the detector end cap along the main axis.

基于高纯锗探测器的核电厂一回路系统辐射源项就地γ谱测量

针对核电厂一回路系统管道内壁沉积的腐蚀活化产物,开展γ辐射源项就地测量技术研究。基于高纯锗探测器开发了辐射源项就地测量系统(Sterm-HPGe),利用蒙特卡罗软件进行了无源效率刻度,并开展了实验室效率验证工作。在300~1 408 ke V能量范围内,HPGe探测器在无准直器屏蔽和有准直器屏蔽情况下,点源全能峰效率计算值与测量值的相对偏差分别在±5%和±10%以内。测量系统在我国压水堆核电厂进行了现场应用,能够较准确地测量出管道内60Co、58Co、110mAg等典型沉积核素的源项活度,管道表面剂量率的计算值与测量值的相对偏差一般在±40%以内。

γ谱仪效率刻度标准源的制备

介绍了１种常用的热焊封制备γ点源的方法，并制备了几种核素的γ点源。在γ谱仪上进行了检验，得到了计算值和测量值一致的结果。同时，将高纯锗γ谱仪作了更准确的效率刻度。

建筑材料中天然放射性的γ能谱分析

应用HPGeγ谱仪对一批建筑材料中226Ra、232Th和40K的放射性比活度进行了测定。结果表明,根据GB6566-2001《建筑材料放射核素限量》,其内照射指数IRa和外照射指数Ir(除2#、3#样品外)均达国家标准限制要求,可作为建筑主体材料使用。根据放射性水平指数,皆属于A类装修材料。并计算了相关的年有效剂量当量。

受放射性微粒污染的地表砂土中放射性核素活度的就地测量

本文简要介绍一种对放射性微粒污染的地表砂土中放射性核素活度的就地测量方法。在实验测量中,所关注的测量区域是半径为r的圆形地面,污染层厚度为l,探测器置于圆心上方h高度处。测量中使用了"取样扣除"技术,即先在现场用就地HPGeγ谱仪直接测量,然后刮去污染层,回填与刮出土壤同质量的不含人工核素的"空白砂土",再测量一次。将两次测得的净计数率相减后计算出污染层土壤中被测核素的比活度;同时取污染砂土样品送实验室分析测量。当r取0.80m,l为0.02m,h为0.50m时,对污染核素137Cs,在9个实验点上的就地测量结果与样品实验室分析结果相比,最大偏差为37%。

北京周边地区土壤中天然放射性核素所致γ射线外照射剂量率空间分布

目的:通过调查北京周边地区土壤中天然放射性核素^(226)Ra、^(232)Th和^(40)K的放射性活度浓度,估算其所致γ射线外照射剂量率,绘制北京周边地区γ射线外照射剂量率空间分布图。方法:用HPGeγ能谱仪测量土壤样品中^(226)Ra、^(232)Th和^(40)K的活度浓度,借助Arc GIS软件绘制土壤中天然放射性核素所致γ射线外照射剂量率空间分布图。结果:共采集和测量416份土壤样品,得到的γ射线外照射剂量率为26.9~94.2 nGy/h,平均值为62.0 nGy/h,北京周边大部分地区γ射线空气吸收剂量率水平在50.0~70.0 nGy/h之间。结论:绘制直观简单的北京周边地区土壤中天然放射性核素所致γ射线外照射剂量率分布图,对于评价和研究该区域环境放射性水平的变化具有重要意义。

放射性核素γ谱分析方法探讨

在实验室仅存在混合刻度源条件下,探讨不同解谱方法对放射性核素活度估算的适用性。本文利用HPGe γ谱仪测量样品,并分别采用效率曲线法和相对比较法来分析样品中^(241)Am、^(60)Co、^(137)Cs、^(40)K核素活度。结果表明,若干扰核素对样品中待分析核素产生的影响可忽略,但对混合刻度源中相应的待分析核素影响较大时,经综合考虑,相对比较法所得结果优于效率曲线法;若干扰核素对样品中待分析核素产生的影响不可忽略,但对混合刻度源中相应的待分析核素影响不大时,与相对比较法相比,效率曲线法占优势。