LabSOCS无源效率刻度软件验证与测量研究

目的 检验LabSOCS无源效率刻度软件在实际样品测量中的应用效果,对样品自吸收校正和级联辐射符合相加修正进行分析。方法 利用实验室γ谱仪对某公司的两个标准样品进行一系列的测量。采用LabSOCS无源效率刻度软件生成的效率对测量结果进行计算。与证书标准值进行比较,验证分析各核素的计算结果。结果 LabSOCS无源效率刻度软件可以较好地解决γ能谱测量分析中的样品自吸收校正问题,宽能型高纯锗γ能谱仪采用LabSOCS分析的²⁴¹Am和¹⁰⁹Cd结果与标准值的最大偏差<4%,但对于级联辐射引起的符合相加修正还不能直接解决。结论 LabSOCS无源效率刻度软件通过对样品的成分、密度等信息的精准描述,可以较好地解决样品自吸收校正问题。但当分析带有级联辐射的核素时,仍需对符合相加效应加以考虑。可以利用LabSOCS灵活的模拟方式,增加带有级联核素样品到探测器的距离,完成级联核素的精准测量。     

NaI(T1)γ谱仪对环境样品探测效率的刻度

用蒙特蕾罗方法计算了NaI(T1)γ谱仪对不同介质体源的探测效率,用实验方法测量了环境介质体源的探测效率,并给出了部分结果,计算和测量的结果在15%内符合。     

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。     

LabSOCS效率刻度方法在应急监测实验室快速分析中的应用

目的 探讨LabSOCS效率刻度方法在"涉核"事件应急监测实验室分析中的应用.方法 用LabSOCS效率刻度方法模拟应急监测中采集的3种环境样品的探测效率,并与这3种样品的有源效率刻度的实测探测效率进行比较.结果 LabSOCS效率刻度方法模拟的探测效率(共20组比对值)与实测效率最大的相对偏差<15%,其中相对偏差小于5%的占70%.结论 LabSOCS效率刻度方法可以代替实测标准刻度源得到效率的方法,满足"涉核"事件应急监测实验室快速分析的需求.

Abstract：

Objective To explore the effeetiviness of the method of LabSOCS(Laboratory sourceless calibration software)efficiency calibration in laboratory rapid analysis for emergency monitoring of nuclear incidents.Methods The detection efficiency of three kinds of environmental samples in emergency monitoring Wag calculated bY using the LabSOCS efficiency calibration method,and compared with the values that were obtained by way of radioactive source calibration method.Results The maximum relative deviation of the detection efficiency between the two methods was less than 15%,and the values with relative deviation less than 5%accounted for 70%.Conclusions The LabSOCS efficiency calibration method might take the place of radioactive source efficiency calibration method,and meet the requirement of rapid analysis in emergency monitoring of the nuclear incidents.     

LabSOCS效率刻度方法在应急监测实验室快速分析中的应用

目的 探讨LabSOCS效率刻度方法在"涉核"事件应急监测实验室分析中的应用.方法 用LabSOCS效率刻度方法模拟应急监测中采集的3种环境样品的探测效率,并与这3种样品的有源效率刻度的实测探测效率进行比较.结果 LabSOCS效率刻度方法模拟的探测效率(共20组比对值)与实测效率最大的相对偏差<15%,其中相对偏差小于5%的占70%.结论 LabSOCS效率刻度方法可以代替实测标准刻度源得到效率的方法,满足"涉核"事件应急监测实验室快速分析的需求.     

无源效率刻度方法在中子剂量估算中的应用

目的在意外中子照射情况下,快速给出探测器的探测效率,利用24Na能谱分析法估算中子剂量。方法使用Genius-2000 GeomComposer软件实现对探测器的效率刻度。结果可快速给出探测器对3 ml血样中1.368 MeV能量的γ光子的探测效率,其数值为4.05271×10-2,软件给出的误差为4.0%。对中子照射样品的剂量估算值为1.94～2.82 Gy,算术平均值为2.38 Gy,剂量值的不确定度约为20.07%。结论将无源效率刻度方法应用在人体血液24Na能谱分析法中,可提高估算速度。     

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。     

高分辨野外γ能谱仪的刻度和应用

本文介绍了一台高能纯锗野外γ能谱仪系统的组成、性能、刻度和应用.该系统主要由CA NBERRA S10多道分析器,GC2519HpGe探测器组成,对⁶⁰C01332γ射线的分辨率小于1.9keV.相对效率好于25%,采用点源刻度技术进行刻度.本文还简述了高分辨野外γ能谱技术的应用.     

便携式NaI (Tl)γ谱仪对甲状腺内131 I的探测效率模拟计算

目的 计算不同甲状腺-颈部刻度模体和测量位置对便携式γ谱仪的全能峰探测效率影响,为更加准确开展人体甲状腺内¹³¹I活度现场测量提供指导。方法 在对4种典型的甲状腺-颈部模体和用于甲状腺内¹³¹I活度测量的便携式3英寸NaI （TI）γ谱仪进行建模的基础上,结合可能的现场测量情景,利用蒙特卡罗方法模拟计算便携式NaI （TI）γ谱仪在不同测量距离、不同甲状腺深度、不同甲状腺体积等条件下的全能峰（364.5 keV）探测效率。结果 NaI （TI）γ谱仪的探测效率随探测器与颈部表面距离增加而显著递减,紧贴颈部表面的探测效率约为距颈部表面15 cm的15倍;探测效率随甲状腺深度增加而明显降低,在颈部表面测量时,深度为2 mm的探测效率约为30 mm的3.6倍;探测效率随甲状腺体积增大而减小,在颈部表面测量时,体积为1 ml的探测效率是30 ml的1.71倍;探测效率随探测器中心偏移而降低,尤其是在颈部表面测量时,中心偏离2 cm会导致探测效率下降约15%。结论 利用便携式NaI （TI）γ谱仪开展人体甲状腺内¹³¹I活度准确测量,不仅需要掌握探测效率刻度时的测量距离,还需了解所用刻度模体内的甲状腺深度与体积。     

环境样品中放射性核素γ谱分析的比对

为了对用γ谱仪分析环境样品中的放射性核素含量进行质量控制,组织了第二次卫生部系统及有关单位的γ谱分析环境样品的比对工作.本文介绍了这次比对的方法,方式、数据处理、定值方法及十二个实验室分析三个不同填充密度的土壤样品及二个河泥样品中的²³⁸U、²²⁶Ra、²³²Th、⁴⁰K¹³⁷Cs和¹³⁴Cs等放射性核素含量的测量结果,还分析了各实验室测量数据的精确度,有86%左右的测量分析数据与参考值在±20%以内符合,只有个别实验室由于系统误差较大,影响了测量结果的准确性.     

Monte Carlo simulation of a PhosWatch detector using Geant4 for xenon isotope beta–gamma coincidence spectrum profile and detection efficiency calculations

A simulation tool has been developed using the Geant4 Toolkit to simulate a PhosWatch single channel beta–gamma coincidence detection system consisting of a CsI(Tl)/BC404 Phoswich well detector and pulse shape analysis algorithms implemented digital signal processor. The tool can be used to simulate the detector's response for all the gamma rays and beta particles emitted from ¹³⁵Xe, ^133mXe, ¹³³Xe, ^131mXe and ²¹⁴Pb. Two- and three-dimensional beta–gamma coincidence spectra from the PhosWatch detector can be produced using the simulation tool. The accurately simulated spectra could be used to calculate system coincidence detection efficiency for each xenon isotope, the corrections for the interference from the various spectral components from radon and xenon isotopes, and system gain calibration. Also, it can generate two- and three-dimensional xenon reference spectra to test beta–gamma coincidence spectral deconvolution analysis software.     

Geometrical optimization of an annulus Compton suppression system using Monte Carlo simulation

We are planning to construct a Compton-suppression system permitting accurate and precise determinations of radioactivity of low-level environmental samples. An annulus guard detector (NaI) and a plug-in detector (NaI) are being used as suppression detectors with an HPGe primary detector. The geometry of the Compton suppression spectrometer was optimized by simulation with PENELOPE for obtaining the highest suppression factor (SF) for a point source. The results of the simulations show that the ultimate value of the suppression factor is 7.87±0.18, obtained when the source is located at 57% of an annuls guard detector.     

Optimization of a measurement facility for radioactive waste free release by Monte Carlo simulation

A novel free release measurement facility (FRMF) was developed within the joint research project “Metrology for Radioactive Waste Management” of the European Metrology Research Programme. Before and during FRMF design and construction, Monte Carlo calculations with MCNPX and PENELOPE codes were used to optimize the thickness of the shielding, the dimensions of the container, and the shape of detector collimators. Validation of the numerical models of the FRMF detectors and the results of the optimization are discussed in the paper.     

A feasibility study on gamma-ray tomography by Monte Carlo simulation for development of portable tomographic system

The electron beam X-ray tomographic scanner has been used in industrial and medical field since it was developed two decades ago. However, X-ray electron beam tomography has remained as indoor equipment because of its bulky hardware of X-ray generation devices. By replacing X-ray devices of electron beam CT with a gamma-ray source, a tomographic system can be a portable device. This paper introduces analysis and simulation results on industrial gamma-ray tomographic system with scanning geometry similar to electron beam CT. The gamma-ray tomographic system is introduced through the geometrical layout and analysis on non-uniformly distributed problem. The proposed system adopts clamp-on type device to actualize portable industrial system. MCNPx is used to generate virtual experimental data. Pulse height spectra from F8 tally of MCNPx are obtained for single channel counting data of photo-peak and gross counting. Photo-peak and gross counting data are reconstructed for the cross-sectional image of simulation phantoms by ART, Total Variation algorithm and ML-EM. Image reconstruction results from Monte Carlo simulation show that the proposed tomographic system can provide the image solution for industrial objects. Those results provide the preliminary data for the tomographic scanner, which will be developed in future work.     

Optimization of the target of an accelerator-driven neutron source through Monte Carlo numerical simulation of neutron and gamma transport by the PRIZMA code

At Budker Institute of Nuclear Physics, epithermal neutron source for neutron-capture therapy was built and neutron generation was realized. Source is based on tandem accelerator and uses near-threshold neutron generation from the reaction ⁷Li(p,n)⁷Be. The paper describes target optimization through the numerical simulation of proton, neutron and gamma transport by Monte Carlo method (PRIZMA code). It is shown that the near-threshold mode attractive due low activation provides high efficiency of the dose and acceptable therapeutic ratio and advantage depth.     

Interface software for DOSXYZnrc Monte Carlo dose evaluation on a commercial radiation treatment planning system

Purpose As the conventional graphical user interface (GUI) associated with DOSXYZnrc or BEAMnrc is unable to define specific structures such as gross tumor volume (GTV) on computed tomography (CT) data, the quantitative analysis of doses in the form of dose-volume histograms (DVHs) is difficult. The purpose of this study was to develop an interface that enables us to analyze the results of DOSXYZnrc output with a commercial radiation treatment planning (RTP) system and to investigate the validity of the system. Materials and methods Interface software to visualize three-dimensional radiotherapy Monte Carlo (MC) dose data from DOSXYZnrc on the XiO RTP system was developed. To evaluate the interface, MC doses for a variety of photon energies were calculated using the CT data of a thorax phantom and a uniform phantom as well as data from patients with lung tumors. Results The dose files were analyzed on the XiO RTP system in the form of isodose distributions and DVHs. In all cases, the XiO RTP system perfectly displayed the MC doses for quantitative evaluation in the form of differential and integral DVHs. Conclusion Three-dimensional display of DOSXYZnrc doses on a dedicated RTP system could provide all the existing facilities of the system for quantitative dose analysis.     

252Cf裂变中子源在组织等效模体中的中子和γ辐射剂量分布的计算

目的：计算^252Cf裂变中子源的的中子和γ辐射在组织等模体内的剂量分布,为使用^252Cf裂变中子源进行中子放疗提供有用的剂量学参数。方法：建立^252Cf源和组织等效模体的三维几何计算模型,利用蒙特卡罗方法进行中子和γ辐射联合输运计算。结果：计算了两种医用^252Cf裂变中子源在水、血液、肌肉、皮肤、骨骼和肺组织等效材料构成的模体中距源不同距离点处的中子和γ辐射吸收剂量。结论：蒙特卡罗计算结果与文献数据以及使用双电离室实验测量的结果符合得较好。对^252Cf裂变中子源在5种组织材料构成的模体中中子和γ辐射的剂量分布进行了比较,使用水作为组织等效材料对^252Cf裂变中子源在在以肌肉、血液和皮肤构成的局部组织内的剂量分布进行模拟计算,可取得较可靠的结果。     

Determination of full-energy peak efficiency at the center position of a through-hole-type clover detector between 0.05 MeV and 3.2 MeV by source measurements and Monte Carlo simulations

Full-energy peak efficiency at the center position of a through-hole-type clover detector was determined by the measurement of standard sources and by Monte Carlo simulation. The coincidence summing under the large-solid-angle condition was corrected using Monte Carlo calculation based on the specific decay scheme for ¹³³Ba, ^152,154Eu, and ⁵⁶Co. This allowed the peak efficiency to be extended from 0.05 MeV to 3.2 MeV with an approximate uncertainty of 3%.     

EyeDose: An open-source tool for using published Monte Carlo results to estimate the radiation dose delivered to the tumor and critical ocular structures for 125I Collaborative Ocular Melanoma Study eye plaques

PurposeRadiation side effects and visual outcome for uveal melanoma patients managed with plaque radiotherapy are dependent on the radiation dose administered to the tumor and nearby healthy tissues. We have developed an open-source software tool, EyeDose, to simplify and standardize tumor and critical structure dose reporting for Collaborative Ocular Melanoma Study eye plaques.Methods and MaterialsEyeDose is a MATLAB-based program that calculates point dose and volume dose metrics for standard models of the tumor and critical ocular structures. It uses published three-dimensional dose distributions for eye plaques, calculated with Monte Carlo methods, which are oriented with respect to the eye using the tumor's position on a fundus diagram. A standard model for the ocular structures was created using published measurements and patient CT scans. EyeDose reports radiation statistics for the fovea, optic disc, lens, lacrimal gland, retina, and tumor. The dosimetric margin for implant placement uncertainty is also calculated.ResultsEyeDose calculations were validated against previously published Monte Carlo results for eight different tumor positions, including the dose to the fovea, optic disc, lacrimal gland, lens, and along the central axis. EyeDose accepts a spreadsheet input for rapidly processing large retrospective patient data sets, with an average run time of <40 s per patient. EyeDose is published as an open-source tool for easy adaptation at different institutions.ConclusionsEyeDose calculates radiation statistics for Collaborative Ocular Melanoma Study eye plaque patients with Monte Carlo accuracy and without a treatment planning system. EyeDose streamlines data collection for large retrospective studies and can also be used prospectively to assess plaque applicability.