野外γ谱仪刻度的蒙特卡罗模拟

用蒙特卡罗方法对NaI(Tl)野外γ谱仪刻度进行模拟,计算谱仪的响应系数.通过与实验的比较,研究利用蒙特卡罗方法对NaI(Tl)野外γ谱仪进行刻度的可行性.结果表明,当模拟探测器对137Cs的能量分辨率从8%～14%变化时,模拟结果与实验结果的差别在12%以内.     

利用格雷原理刻度氡气电离室

氡气计通常是用标准液体镭源进行刻度的。将液体镭源中已知数量的氡引入电离室。三小时后氡及其子体在电离室中达到平衡,然后进行测量,得到静电计在一定电压灵敏度下的格值。 在现场使用氡气计时,用液体镭源刻度有时感到不便。这是由于当氡气电离室多时,刻度工作量比较大,同时镭源损失也较大以致不能用于标准测量。此外,在野外探矿中应用液体镭源也感到不便。这样就研究了用固体γ源刻度氡气电离室的工作。     

惰性气体β-γ符合测量系统探测器能量及分辨率刻度

β-γ符合法是全面禁止核试验条约(CTBT)放射性核素核查中惰性气体氙测量的一种重要方法,探测器能量及分辨率刻度是其首要解决的关键技术。本工作详细介绍了β-γ符合测量系统NaI(Tl)闪烁体和塑料闪烁体探测器能量及分辨率刻度的方法和结果,采用γ放射性核素点源刻度NaI(Tl)γ射线能量及分辨率,利用137Cs661.66keVγ射线康普顿散射电子刻度塑料闪烁体β射线能量及分辨率,并与131Xem内转换电子刻度的β射线能量分辨率结果进行了比较。结果表明:用137Cs康普顿散射电子刻度塑料闪烁体β射线能量是一种简便可行的方法,但用其刻度的β射线分辨率比实际的大。     

层析γ扫描中的探测效率刻度

探测效率刻度技术是层析γ扫描测量中最重要的技术之一。本工作研究用蒙特卡罗方法刻度层析γ扫描系统探测效率的方法。对3×3×3体素组成的样品模型,用蒙特卡罗软件计算了层析γ扫描测量装置的探测效率矩阵。在实验室层析γ扫描原型装置上,实验研究了层析γ扫描测量装置的探测效率。对两者进行了比较,相对偏差绝对值小于5％。研究结果表明了蒙特卡罗方法刻度层析γ扫描测量装置探测效率的可行性。     

就地HPGeγ谱仪的刻度及应用

介绍了用于就地测量γ谱仪的刻度方法和技术,对一台可携式HPGeγ谱仪进行了刻度。给出了该谱仪用于就地测量的放射性核素比活度刻度因子(N_f/A)和空气吸收剂量率刻度因子(N_f/D),对刻度因子的不确定度进行了估计。在核设施周围环境中进行了就地测量并与其它方法的测量结果进行了比对。     

利用航空模型源刻度车载NaI γ谱仪系统

利用车载Na I(Tl)γ谱仪系统进行巡测之前须进行效率刻度,由于巡测特点刻度需使用大体积源,且系统体积庞大不便进入实验室。因此,传统的实验室γ谱仪刻度方法不适用于该系统。文中对采用的系统进行了介绍,对刻度的方法原理作了描述,并利用航空模型源进行了效率刻度和验证,验证结果表明效率刻度误差小于10%,最后对效率刻度不确定度来源作了分析。     

就地HPGeγ谱仪的刻度及应用

介绍了用于就地测量γ谱仪的刻度方法和技术,对一台可携式HPGeγ谱仪进行了刻度。给出了该谱仪用于就地测量的放射性核素比活度刻度因子(N_f/A)和空气吸收剂量率刻度因子(N_f/D),对刻度因子的不确定度进行了估计。在核设施周围环境中进行了就地测量并与其它方法的测量结果进行了比对。     

线性刻度型γ-料位计的源活度分布检验

本文直接验证了按等效点源法源活度分布公式算出的源活度满足线性刻度要求,并给出了检验线性刻度型γ-料位计源强分布的方法,得到了LB_(3121)型γ-液位计的非线性刻度曲线,提出了改进该液位计源活度分布的初步方案。     

X,γ个人剂量计的刻度

本文讲述x、γ个人剂量计的刻度方法,给出了个人剂量计刻度的最新资料和个人剂量计刻度的实例。     

航空γ谱低能段地质岩性响应规律模拟校正

以往航空γ能谱低能段计数比与地层岩性等效原子序数的相关性模型中未考虑到诸多现实因素的影响。本文基于航空γ能谱刻度模型构建思想,解决了航空γ能谱MC模拟的深穿透问题。并依托此MC模型研究发现空气密度为1.289×10~(-3)g/m~3与实测结果最吻合、地层天然放射性系列活度比与地层密度对航空γ能谱低能段计数比的无影响、90~150 m高空航空γ能谱低能段计数比可采用指数模型校正。并将该模型应用于野外实践,获得良好效果。     

In-situ Calibration Techniques and Preliminary Assessment of Accuracy for NFM on ITER

Absolutely calibrated measurements of the neutron yields which need to cover both D-D and D-T phase of the international thermal-nuclear experimental reactor （ITER） are important for the evaluation of fusion power and fusion gain Q in D-D and D-T operations. This paper describes the in-situ calibration techniques and methods, the neutron sources including ^252Cf and neutron generator for calibration, the preliminary accuracy assessment and the error analyses. In addition, some difficult problems regarding the in situ calibration for the neutron flux monitor （NFM） on ITER are presented and discussed.     

In Situ Methods for Quantifying Gamma-Radiation Levels and Radionuclide Concentrations

Small perturbations of the environmental radiation field by artificial radionuclides have been successfully quantified using high pressure ionization chambers and in situ semiconductor detector gamma-ray spectra. The calibration and use of these instruments for the detection of ground-deposited and airborne sources of activity is described and general methods for data interpretation are discussed. Specific examples are given in which the exposure rate from fallout radionuclides deposited on the soil surface and from noble gases released by nuclear facilities are determined and unambiguously separated from variations in the underlying background.     

Configuration and installation design of optical diagnostic systems on KSTAR

The optical diagnostic system of KSTAR consists of visible diagnostics including toroidal and poloidal Hα monitors, a visible survey spectrometer, and filterscopes. A re-entrant cassette made of stainless steel, containing five optical quartz windows has been developed to allow easy access of the visible diagnostics to the plasma. The configuration and manufacturing design of the diagnostic cassette and the installation of optical diagnostic systems within the cassette are described. The structural and thermal analysis of the diagnostic cassette and in situ calibration of optical diagnostics have also been performed. The optical lens system showed good image quality by spot diagram analysis.     

Fusion yield measurements on JET and their calibration

The power output of fusion experiments and fusion reactor-like devices is measured in terms of the neutron yields which relate directly to the fusion yield. In this paper we describe the devices and methods used to make the new in situ calibration of JET in April 2013 and its early results.The target accuracy of this calibration was 10%, just as in the earlier JET calibration and as required for ITER, where a precise neutron yield measurement is important, e.g., for tritium accountancy.We discuss the constraints and early decisions which defined the main calibration approach, e.g., the choice of source type and the deployment method.We describe the physics, source issues, safety and engineering aspects required to calibrate directly the Fission Chambers and the Activation System which carry the JET neutron calibration. In particular a direct calibration of the Activation system was planned for the first time in JET. We used the existing JET remote-handling system to deploy the ²⁵²Cf source and developed the compatible tooling and systems necessary to ensure safe and efficient deployment in these cases.The scientific programme has sought to better understand the limitations of the calibration, to optimise the measurements and other provisions, to provide corrections for perturbing factors (e.g., presence of the remote-handling boom and other non-standard torus conditions) and to ensure personnel safety and safe working conditions. Much of this work has been based on an extensive programme of Monte-Carlo calculations which, e.g., revealed a potential contribution to the neutron yield via a direct line of sight through the ports which presents individually depending on the details of the port geometry.     

On-line monitoring applications in nuclear power plants

The nuclear power industry is working to reduce generation costs by adopting condition-based maintenance strategies and automating testing activities. These developments have stimulated great interest in on-line monitoring (OLM) technologies and new diagnostic and prognostic methods to anticipate, identify, and resolve equipment and process problems and ensure plant safety, efficiency, and immunity to accidents. This paper provides examples of these technologies with particular emphasis on eight key OLM applications: detecting sensing-line blockages, testing the response time of pressure transmitters, monitoring the calibration of pressure transmitters on-line, cross-calibrating temperature sensors in situ, assessing equipment condition, performing predictive maintenance of reactor internals, monitoring fluid flow, and extending the life of neutron detectors. These applications are discussed in the following sections. Emphasis is placed on the principles of a core OLM method - noise analysis - and the technical requirements for an integrated OLM system are summarized.     

A Comparative Study of the Effect of Calibration Conditions on the Water Equivalence of a Range of Gel Dosimeters

Gel dosimeters are of increasing interest in the field of radiation oncology as the only truly three-dimensional integrating radiation dosimeter. There are a range of ferrous-sulphate and polymer gel dosimeters. To be of use, they must be water-equivalent. On their own, this relates to their radiological properties as determined by their composition. In the context of calibration of gel dosimeters, there is the added complexity of the calibration geometry; the presence of containment vessels may influence the dose absorbed. Five such methods of calibration are modelled here using the Monte Carlo method. It is found that the Fricke gel best matches water for most of the calibration methods, and that the best calibration method involves the use of a large tub into which multiple fields of different dose are directed. The least accurate calibration method involves the use of a long test tube along which a depth dose curve yields multiple calibration points.     

A new consecutive energy calibration method for X/γ detectors based on energy continuously tunable laser Compton scattering light source

In this paper, we present an energy calibration method based on steep Compton edges of the laser Compton scattered(LCS) photon energy spectra. It performs consecutive energy calibration in the neighborhood of certain energy, hence improves calibration precision in the energy region. It can also achieve direct calibration at high energy region(several MeV) where detectors can only be calibrated by extrapolation in conventional methods.These make it suitable for detectors that need wide-range energy calibration with high precision. The effects of systematic uncertainties on accuracy of this calibration method are studied by simulation, using the design parameters of a LCS device—SINAP Ⅲ. The results show that the SINAP Ⅲ device is able to perform energy calibration work over the energy region of 25–740 keV. The precision of calibration is better than 1.6% from 25 to 300 keV and is better than 0.5% from 300 to 740 keV.     

一种高纯锗能谱测井仪相对效率刻度方法

介绍了一种用於多元素分析的高纯锗测井系统相对效率刻度的方法,即所谓“自刻度”方法。这种刻度方法仅依赖於被测对象自身的中子俘获γ射线谱,不需要任何标准样品或模拟刻度井,适用于任何高纯锗探测系统。该文给出了用自刻度方法得到的三个分析结果。     

Calibration factors for the SNOOPY - NP-100 neutron dosimeter

Within CANDU nuclear power facilities, only a small fraction of workers are exposed to neutron radiation. For these individuals, roughly 4.5% of the total radiation equivalent dose is the result of exposure to neutrons. When this figure is considered across all workers receiving external exposure of any kind, only 0.25% of the total radiation equivalent dose is the result of exposure to neutrons. At many facilities, the NP-100 neutron dosimeter, manufactured by Canberra Industries Incorporated, is employed in both direct and indirect dosimetry methods. Also known as “SNOOPY”, these detectors undergo calibration, which results in a calibration factor relating the neutron count rate to the ambient dose equivalent rate, using a standard Am-Be neutron source. Using measurements presented in a technical note, readings from the dosimeter for six different neutron fields in six source-detector orientations were used, to determine a calibration factor for each of these sources. The calibration factor depends on the neutron energy spectrum and the radiation weighting factor to link neutron fluence to equivalent dose. Although the neutron energy spectra measured in the CANDU workplace are quite different than that of the Am-Be calibration source, the calibration factor remains constant - within acceptable limits - regardless of the neutron source used in the calibration; for the specified calibration orientation and current radiation weighting factors. However, changing the value of the radiation weighting factors would result in changes to the calibration factor. In the event of changes to the radiation weighting factors, it will be necessary to assess whether a change to the calibration process or resulting calibration factor is warranted.