Study on element detection and its correction in iron ore concentrate based on a prompt gamma-neutron activation analysis system

A prompt gamma-neutron activation analysis(PGNAA) system was developed to detect the iron content of iron ore concentrate. Because of the self-absorption effect of gamma-rays and neutrons, and the interference of chlorine in the neutron field, the linear relationship between the iron analytical coefficient and total iron content was poor, increasing the error in the quantitative analysis. To solve this problem, gamma-ray self-absorption compensation and a neutron field correction algorithm were proposed, and the experimental results have been corrected using this algorithm. The results show that the linear relationship between the iron analytical coefficient and total iron content was considerably improved after the correction. The linear correlation coefficients reached 0.99 or more.

Design of a prompt-gamma neutron activation analysis system on China Advanced Research Reactor

In this paper,computational methods are used to optimize the design of a prompt-gamma neutron activation analysis(PGNAA) system on China Advanced Research Reactor(CARR).Approaches are adopted for obtaining accurate neutron beam parameter and saving the computing time.For the radiation shielding design,the optimizing factors include the cost,weight,volume,machining convenience and background radiation at the detector position.Low background spectrum and high sensitivity are expected.The simulation results,and experiences from international PGNAA community,were used in the design of the CARR PGNAA system.

Overview of Industrial Materials Detection Based on Prompt Gamma Neutron Activation Analysis Technology

Prompt gamma neutron activation analysis (PGNAA) is a non-destructive online measurement nuclear analysis method. With its unique advantages, it has been widely used in online analysis of industrial materials such as coal, cement, and minerals in recent years. However, there are many kinds of literature on PGNAA in the field of industrial materials detection, and there are still a few concluding articles. To this end, based on the principle of PGNAA online analysis, the status quo and development of the real-time online detection of industrial material components in the field are reviewed and discussed by consulting a large number of domestic and foreign PGNAA related literature and data, to facilitate the reference of relevant scientific researchers.

Progress of neutron induced prompt gamma analysis technique in 1988～2003

This paper described new development of the neutron induced prompt gamma-ray analysis(NIPGA) technology in 1988-2003.The pulse fast-thermal neutron activation analysis method,which utilized the inelastic reaction and capture reaction jointly,was employed to measure the elemental contents more efficiently.Lifetime of the neutron generator was more than 10000h and the performance of detector and MCA reached a high level.At the same time,Monte Carlo library least-square method was used to solve the nonlinearity problem in the NIPGA.

DEVELOPMENT AND APPLICATIONS OF AN ON-LINE THERMAL NEUTRON PROMPT-GAMMA ELEMENT ANALYSIS SYSTEM

This paper introduces the principles, instrumentation, implementation, and industrial applications of an on- line thermal neutron prompt- gamma element analysis system (using a 252Cf neutron source, Am- Be neutron source, or neutron generator). The energy resolution of the system at the H prompt- gamma full- energy photopeak (2.22325 MeV) is 3.6 keV. The concentration measurement error of A12O3, Fe2O3, CaO and SiO2 is ±0.3%,±0.1%.±0.4% and ±0.4%, respectively.The system has been tested on- site at both the Shandong and the Zhengzhou Aluminum Works. Our preliminary on- site measurements confirm that the stability, reliability, measurement range, and accuracy of the system can meet the requirements of the aluminum production process. Facilitation of this measurement at aluminum plants is expected to reduce plant costs by over 3 million dollars annually through reduced energy consumption, more rapid qualification of pulps being mixed during the production process, and in reduced labor costs.

A brief introduction to neutron activation analysis in China―history,major achievements,and future perspectives

The history,the major achievements in both methodology and applications,the current trends and future perspectives of neutron activation analysis (NAA) in China are briefly described.

MC simulation of a PGNAA system for on-line cement analysis

A prompt gamma neutron activation analysis system with a 252Cf neutron source for on-line cement analysis has been simulated with the MCNP code.The results indicate that the optimum arrangement is a Bi shield of 20-mm thickness,a polyethylene moderator of 50-mm thickness,a source-to-sample distance of 70 mm,and cement samples of 1200 mm×600 mm×170 mm.To absorb thermal neutrons and suppress low-energy γ-rays,the optimum-sized sheets are 150 mm×7 mm Cd,and 150 mm×15 mm Pb.

Monte-Carlo simulation of cement neutron field distribution characteristics in PGNAA

The distribution characteristics of the neutron field in cement was simulated using the MCNP code to comply with the requirements of an online Prompt Gamma Neutron Activation Analysis system.Simulation results showed that the neutron relative flux proportion reduced with increasing cement thickness.When the cement thickness remains unchanged,the reduced proportion of thermal neutrons increases to a small extent,but the epithermal, intermediate,and fast neutrons will decrease according to the geometric progression.H element in the cement mainly affects the reduction of fast neutrons and other single-substance elements,e.g.,O,Ca,56Fe,Si,and Al.It also slows down the reduction of the fast neutrons via inelastic scattering.O contributes more than other elements in the reduction of fast neutrons.Changing the H content affects the thermal,epithermal,intermediate,and fast neutrons, while changing the Ca,Fe,and Si contents only influences the thermal,epithermal,and intermediate neutrons;hence, there is little effect on the reduction of fast neutrons.

中国先进研究堆瞬发γ元素成像技术研究

无损分析样品内部的元素分布,对于材料、考古、地质科学等领域的研究具有重要意义。基于瞬发γ活化分析方法,结合中子照相技术,分析了模拟样品的结构和对称性,首次利用中国先进研究堆(CARR)水平孔道聚焦的微束中子束流,开展样品瞬发γ扫描分析和材料内部元素分布研究。通过蒙特卡罗软件(MCNP)对样品元素分布实验模型进行分析,模拟结果获得了样品不同区域的铜、铁、铝元素分布,基本实现了元素空间分辨。MCNP计算结果表明在瞬发γ扫描分析中,优化准直几何参数和提高中子通量能进一步提高元素空间分辨和元素测量准确度。

反应堆瞬发γ活化成像技术研究进展

瞬发γ活化成像技术(Prompt Gamma Activation Imaging,PGAI)是基于瞬发γ中子活化分析技术(Prompt Gamma Neutron Activation Analysis,PGAA)的一种新型元素成像技术,具有PGAA非破坏性、高灵敏度的多元素分析特点,同时可研究大体积样品内元素含量的三维分布情况。与移动中子源(如同位素中子源、加速器中子源)相比,反应堆中子源具有高通量的冷/热中子,因此,基于反应堆中子源的PGAI装置具有更加广阔的应用前景。鉴于PGAI技术的重要性,主要介绍了PGAI技术原理和测量方法、列举了国内外具有代表性的PGAI装置及特点,并指出当前PGAI技术研究现状与应用进展。其中,与中子层析成像(Neutron Tomography,NT)结合的PGAI是目前研究的重点。随着国内高通量中子反应堆的持续稳定运行以及PGAI装置的建立和技术发展,相信未来PGAI技术能在我国更多领域得到广泛和深入应用。

基于PGNAA技术在线分析系统的应用

近年来,随着核探测与分析技术的日趋成熟,使复杂γ谱的获取、解析达到了在线测量的要求,从而使在线PGNAA(中子活化瞬发γ射线分析)技术获得了飞速的发展。它可对一些工业生产过程中的全物料进行在线测量,其分析精度、可靠性等皆能满足在线元素含量分析的需要,因而显示出巨大的发展潜力和广阔的市场前景。这里介绍了基于PGNAA技术的在线分析系统的基本原理、组成和发展,并概述了它在水泥、煤炭等行业的应用情况。

中子诱发伽马产生截面测量中的谱分析技术

在中子反应截面测量中,瞬发γ射线法是一种通过测量核反应放出的特征γ射线来得到截面数据的方法,这种方法能够避免竞争反应道产生的干扰.但是瞬发γ射线法为在线实验,本底来源丰富,造成了在线实验谱分析难度大,结果不确定性高.本文研究了使用瞬发γ射线法测量中子诱发伽马产生截面的谱分析技术,总结了中子诱发伽马产生截面测量中不同特征峰形成的物理过程,降低了在线实验谱处理过程中计算效应峰净面积的不确定度.通过采用各种响应函数来对全能峰、本底以及干扰因素进行拟合的方法,精确提取了效应峰的净面积.针对弱峰的净面积,本方法可将峰区域选取引起的波动从30%降低到1%以内,且净面积拟合值与理论值的差距与统计不确定度相当;对于解重峰,本方法所得结果与理论值差距显著低于1%.通过效率曲线分析、拟合优度计算等方法同时验证了谱分析方法的可靠性.

中子场及γ射线自吸收在PGNAA测量中的影响研究

在中子活化瞬发γ射线分析(PGNAA)技术测量中,被测样品内部中子场分布及γ射线自吸收对测量结果有一定影响。针对一套水溶液样品中有害元素的检测装置,通过对两种效应统一考虑并进行了理论计算,建立了一套相应的理论修正模型,并将其应用于检测装置的蒙特卡罗模拟计算结果中。结果表明,经该理论模型修正后,样品中中子场分布及γ射线自吸收对分析结果所造成的影响得到了显著改善。

样品均匀性对PGNAA技术元素分析影响的初步研究

采用蒙特卡罗模拟技术,从样品自吸收和中子场在样品中分布特性两个角度,对中子活化瞬发γ射线分析(Prompt Gamma-ray Neutron Activition Analysis,PGNAA)技术中γ射线能谱受样品均匀性的影响进行了初步研究。结果表明,因样品均匀性不同引起的样品自吸收及中子场分布的变化,对γ射线能谱有一定的影响。由于样品均匀性的变化,部分元素特征峰计数变化可达20%以上,从而在一定程度上影响了元素成分分析的准确度。

PGNAA煤质在线测量中同时提高C、O和其它元素测量精度的慢化体模拟（英文）

提出两种慢化体设计方案,第一种方案直接在原有慢化体中引入孔道,第二种方案在慢化体中增加一层铅之后再引入孔道.利用蒙特卡罗方法对两种方案进行研究.计算结果表明,采用第一种方案可以有效地提升C、O元素的测量精度,但同时会降低H、Si等元素的测量精度;采用第二种方案可提高C元素和O元素的测量精度,同时也可以提高H、Si等其它元素的测量精度.

Optimization of PGNAA device and algorithm for testing basicity index of sinter mixture

Sinter is the main raw material in the blast furnace iron-making process,and basicity(CaO/SiO2)is an important quality index of sinter.Prompt gamma neutron activation analysis is a multi-elemental online detection technology that has been successfully applied in cement,coal,etc.Compared with cement as a raw material,sinter exhibits poor moderation ability and a large neutron absorption cross section.Therefore,cement detection devices are not suitable for sinter mixture detection.In this study,a prompt gamma neutron activation analysis equipment used for testing cement was re-optimized to render it suitable for measuring a sinter mixture.Using Monte Carlo simulation,the comprehensive detection efficiency of the detection device improved by 71.52%.Because of the gamma-ray self-shielding effect of the sinter mixture,the detection errors of CaO and SiO2 are significant.By applying the gamma-ray self-shielding correction algorithm,the detection accuracies improved,and their linear correlation coefficients R2 exceeded 0.99.Furthermore,by applying an improved analyzer to a sintering plant,the first-grade product rate of the factory increased by 4.64%.

利用PGNAA系统对铝土矿石进行在线检测的可行性研究

利用一款基于瞬发γ中子活化原理设计的主要针对皮带散状物料元素进行在线检测的工业仪器,研究这款仪器用于测量铝土矿组成分析的可行性,实验主要进行了两组样品中Ca、Si、Al、Fe、Ti五种元素的测试,其中一组样品由高纯氧化物组成,一组样品由铝土矿和高纯氧化物组成,测量结果表明,CaO、SiO2、Al2O3、Fe2O3、TiO2的测量精度分别为±0.23%、±0.18%、±0.35%、±0.14%、±0.08%,能够满足原料自动配比及入厂原料质量控制的要求。

MC simulation of thermal neutron flux of large samples irradiated by 14 MeV neutrons

The response of a 14 MeV neutron-based prompt gamma neutron activation analysis (PGNAA) system,i.e.the prompt gamma-rays count rate and the average thermal neutron flux,is studied with a large concrete sample and with a homogeneous large sample,which is made of polyethylene and metal with various concentrations of hydrogen and cadmium using the MCNP-5 (Monte Carlo N-Particle) code.The average thermal neutron flux is determined by the analysis of the prompt gamma-rays using the thermal neutron activation of hydrogen in the sample,and the thermal and fast neutron activation of carbon graphite irradiation chamber of the PGNAA-system.Our results demonstrated that the graphite irradiation chamber of the PGNAA-system fairly operates,and is useful to estimate the average thermal neutron flux of large samples with various compositions irradiated by 14 MeV neutrons.

PGNAA方法测量元素的非线性规律研究

瞬发伽玛中子活化分析(prompt gamma neutron activation analysis,PGNAA)在线分析仪广泛应用于水泥、煤炭等工业控制领域,由于工业现场产量的变化,导致皮带上物料的厚度不恒定,当物料厚度变化时,在线分析仪的测量结果会出现偏差。为消除在线分析仪测量不同厚度物料的测量偏差,通过理论分析和蒙特卡罗模拟(MCNP)研究中子自屏蔽和伽玛自衰减影响,并寻求修正模型。根据探测器接收特征伽玛射线的计算公式进行理论分析,利用蒙特卡罗软件建立PGNAA在线分析仪装置模型,分别模拟Al_2O_3、SiO_2、CaO、Fe和水泥生料等物料随厚度变化的特征射线计数,以水泥在线分析仪为例,寻求修正模型。结果表明,特征伽玛射线强度不随物料厚度增加而线性增长,按照线性标定方法的在线分析仪测量误差增大,各元素平均相对误差大于10%;根据水泥生料各元素的特征射线计数与物料厚度之间的关系,建立适用于测量水泥生料的多项式厚度修正模型。与线性标定相比,修正后分析仪测量误差降低30%以上,可为煤质、烧结料、铝土矿等块状物料的PGNAA元素检测提供修正方法。

应用MOCA程序设计煤料PGNAA实验装置

为促进国内煤料瞬发γ中子活化分析(prompt gamma neutron activation analysis,PGNAA)技术开发,本研究使用基于蒙特卡罗模拟方法的MOCA程序对煤料PGNAA技术常用中子源252 Cf进行模拟建模,并对252 Cf中子源在煤料和常用慢化体聚乙烯中的中子场分布进行模拟计算,得到了源距与中子通量的关系曲线。通过模拟计算的结果,结合煤料PGNAA的测量过程和实验室情况,设计了既可表征大批煤料PGNAA过程又可实现辐射防护的实验装置。使用该装置开展实验室实验,取得了具有明显特征峰的实验谱图和良好线性的灰分标定系数,表明设计的实验装置具有适宜性,可利用该装置对煤料PGNAA进行进一步实验室研究。