缝丝法强流离子束发射度测量中系统误差的模拟研究

本文分析了缝丝法测量强流离子束发射度时系统误差的主要来源,并用模拟计算的方法研究了不同误差来源所带来的误差大小。对于rms发射度测量,因缝采样、忽略缝宽和丝直径、以及空间电荷效应所引起的系统误差均可忽视,而短缝采样和设置较大的阈值则会引起显著的系统误差。     

反射中子效应测量中的本底和可信性分析

介绍了在反射中子效应实验中的中子本底测量方法和测量结果。从系统误差的角度,分析了反射中子效应实验结果的可信性。在实验误差范围内,实验值和理论值相符,在近50个实验数据中有50％的实验值在3％～5％的误差范围内和理论值相符。     

γ测井中的问题:倾斜层对精确测定矿石品位的影响

根据γ测井数据计算铀矿带品位-厚度乘积时,假设钻孔垂直于矿带平面。如若这种假设不正确,那么确定的品位-厚度乘积给出的铀矿线性储量要比实际的多。一个简单的几何处理说明,对于0到20°的相对倾角来说(钻孔的垂线和矿带平面之间的夹角),这个误差是很小的,约6％或更小些;但对于较大的相对倾角来说这个误差可能相当大,例如60°的相对倾角,误差为100％。如果这个相对倾角能根据倾角测井记录来测定或根据地质情况来估计,那么简单的线性修正系数就可应用于视矿石品位-厚度值中来补偿因倾斜层造成的误差。     

立式靶丸AFM表面轮廓仪系统精度测试

研制了立式轴系结构靶丸AFM表面轮廓仪,对测量装置的精度进行了系统的测试。针对影响测量结果的不确定性因素,分别从气浮轴系回转误差、系统静态噪声误差以及综合测量误差几个角度开展实验研究。采用标准球及两步回转误差分离法获取了气浮轴系系统误差数据,在实际测量时作为系统误差进行消除。综合测量实验证明,该系统的测量噪声峰谷极差约22 nm,RMS为5.2 nm。     

疏失误差及协方差矩阵的调整

给出了检验疏失误差是否存在的符号检验法和游程数检验法。并给出了存在疏失误差时如何调整实验数据协方差矩阵的方法。     

质谱计系统误差的校正

用质谱计作同位素组成的绝对测定时,需要考虑仪器的系统误差。在质谱计中,测量的量是离子流的强度;由于质谱计存在质量甄别效应,因此离子流强度的比值并不完全等于试样中相应的同位素组分的比值。这就构成了仪器的系统误差,而且这个误差是质谱分析中主要的系统误差。为了校正这个系统误差,尼尔(Nier)最先使用了近于同位素纯的A~(36)与A~(40)人     

乏燃料后处理厂核材料衡算仿真

为优化乏燃料后处理设施的核材料衡算,寻找核材料衡算不平衡差（MUF）的主要因素,采用基于数值模拟的系统仿真方法,以核材料衡算视角构建乏燃料后处理设施核材料衡算仿真模型。改变模型工艺参数仿真不同规模的后处理设施中各环节核材料的流通量,然后以正态分布随机变量模拟各铀钚衡算测量点的随机误差,将这些带有随机特征的测量值叠加相应测量的系统误差作为核材料的仿真测量值。仿真计算结果表明,1AF中Pu、U含量测量的系统误差的方差分别占整体MUF方差的50%、40%以上,是主要误差来源。1AF的体积测量误差较小,占比MUF方差小于15%。废液中U和Pu含量很低,U和Pu含量测量的误差分别为10%和30%,对MUF方差影响不大,占比MUF方差分别小于3%和1%,废液的体积测量误差较小,占比MUF方差小于1%。U和Pu产品测量误差的方差占比MUF方差界于1AF和废液的测量之间,不是MUF误差的主要来源。     

脉冲叠加对放射性元素含量的伽玛能谱测定精度的影响

由于在铀的普查勘探工作中采用伽玛能谱方法(伽玛能谱测井、坑道取样、实验室测量等),需要评价记录高强度伽玛辐射时测定放射性元素含量的可能误差。通常对这种情形只考虑记录仪器的死时间所造成的误差。而对于脉冲叠加所造成的仪器谱的失真效应,一般不予考虑。但是此种失真能使按谱线所算出放射性元素含量值带来系统误差。脉冲叠加影响决定于下列三个基本因素:探测器输入端上的γ辐射强度和谱线形     

用数据处理标定核数据采集系统

利用计算机程序拟合数据采集系统获取的数据,改变拟合参数,找出最佳拟合值,从而标定该数据采集系统,所得标定值的系统误差最小。     

邻边比率法及其在核工程测量中的应用研究

边交会或测边网是以边长作为观测值进行平差计算的,随着边长增加则观测方差迅速增加。虽然,通常光电测距仪的内符合精度高,但受气象代表性误差的影响,使其外符合精度降低,因此类似于系统误差的气象代表性误差大大降低了观测边的精度。针对这一问题,对短边光电测距比率值相关度、边长比率值稳定度进行了理论研究和野外试验,提出了邻边比率交会新方法。由于比率方差σ_γ~2=2η~2γ~2,而测角方差σ_β~2=2J~2ρ~(″2),两者的权相匹配,可完全消除系统误差的影响,获得高精度的测量点位坐标。该方法不严格要求在最佳观测时间内作业和多光段施测,作业简便,特别适合在核工程测量中应用。     

Brownian bridge and statistical error estimation in Monte Carlo reactor calculation

Brownian bridge (BB) is an effective vehicle in processing an output series in Monte Carlo (MC) simulation. However, most estimators based on BB cost the capability of on-the-fly monitoring. Here, on-the-fly implies that statistical error can be computed at every generation except some initial generations. In this work, on-the-fly estimation of standard deviation by the way of BB, which maintains a fixed storage size of tallies, has been investigated within a framework of the iterated integration of simulation output (IISO). Numerical tests on the MC power distribution calculation of a pressurized water reactor core reveal that the IISO approach with a relatively few number of integrations performs fairly well on average. The bias of statistical error can be managed to be about 10% or less.     

Adjustment of Group Cross Sections by Means of Integral Data, (II)

Adjustment of the ABBN set is performed using various integral data obtained from fast critical experiments; through this adjustment, some practical properties are also examined in detail. The correlation coefficient between group cross sections is numerically obtained by assuming that the compound nucleus formation cross section can be described by a statistical model. The effect brought by this correlation to the adjustment of group cross sections is also studied. When the differential and integral data used in the adjustment contain a systematic error, the normalized sum of squares of residuals has a non-central Chi-square distribution. This is numerically examined by generating artificial differential and integral data with the aid of random numbers. The ABBN set collapsed into 15 energy groups is adjusted, and the principal results are compared with the measurements. The reliability of the adjusted integral data and group cross sections is also studied.     

Multiquadric散乱数据插值方法在γ辐射场可视化中的应用初探

探究γ辐射场分布及其变化规律对于核设施的状态监控以及核辐射的防护研究具有重要意义。获取γ辐射场的空间分布需要解决利用少量、离散且分布不规则的实验数据重构整个辐射场的难题。本文首次将Multiquadric径向基函数散乱数据插值方法应用于γ辐射场的重构,并实现了γ辐射场模拟数据重构及可视化。对于具有轴对称性的γ辐射场,在采样数据点个数相同的条件下,与数据处理软件MATLAB中自带的Spline方法得到的插值结果相比,Multiquadric方法插值结果的平均相对误差仅为前者的9.47%;对于转动π/2对称的γ辐射场,提出了一种采样数据优化方案,重构结果的平均相对误差相较于未优化采样数据的结果降低了约64.51%。     

Nuclear Science Abstracts of Japan,and English Translation series of Japanese Papers in the Nuclear Field

A theoretical treatment is developed for the adjustment of group cross sections making use of integral data such as critical mass, reaction rate ratio and sample worth ratio obtained from various fast critical experiments. The method of least squares is the usual practice in such treatment. In the present case, however, the total number of integral data available is usually smaller than that of the group cross sections to be adjusted. To overcome this difficulty, the observation equations for applying the least squares treatment are established by using both integral and differential data. In such treatment, the correlation between group cross sections can be easily taken into account. General formulas are presented on two kinds of such correlation, one based on nuclear theory and the other due to relative measurements of the cross sections. The χ²-test for the sum of squares of the residual is used as criterion to judge whether or not group cross sections carry systematic error. If systematic error exists, the sum of squares of the residual has a non-central Chi-square distribution. When the systematic error is included only in the group cross sections and not in the integral data, it is possible to remove this systematic error through use of the method of least squares.     

Evaluation Method of Statistical Error in. Transit Time Measured with Cross-Correlation of Two Detector Signals

In the transit time method for measuring flow velocity, the cross-correlation function of two detector signals is computed; the delay time which maximizes the function gives the transit time of the fluid between the detectors. The cross-correlation function is mathematically defined for an infinite observation time, however actually it is computed based on a finite length of time. Due to this approximation, the measured cross-correlation function has a statistical uncertainty, which induces a scattering on the measured transit time.

In this paper, it is shown that the statistical error of the transit time may be expressed by using either the derivatives of correlation functions or the power spectral densities. The spectral expression has a merit of giving an intuitive understanding of the nature of the error and it can be seen that the error becomes smaller as the higher frequency components of the spectra increase. The error also becomes smaller when the coherence function has a larger value and/or the observation time extends for a longer period.

A simplified evaluation method of the error is proposed using a trapezoidal approximation for the power spectra and this method is applied to the transit time measurement by electro- magnetic-flowmeters. The evaluated statistical error closely agreed with the measured scattering.     

Energy-Space Dependent Error Propagation in Monte Carlo Coupling Calculation

A new formulation of energy-space dependent propagation of errors has been derived for the Monte Carlo-Monte Carlo coupling technique which is applied to analysis of radiation streaming through a long path. In this formula, it is considered that the source uncertainty due to the statistical error of the preceding Monte Carlo calculation is handed down to a particle as an uncertainty of the particle weight. In the succeeding Monte Carlo calculation, the propagated weight error is scored together with the particle weight by flux estimators. The method has been implemented in the MORSE-ALB code system. As a sample problem, calculation of reaction rates in the main pump room of the primary coolant system of JOYO is performed with the Sn-AMC-AMC coupling technique. As a result, the present method turned out to be significant in estimating the Monte Carlo statistical error of the final value taking into consideration of the energy-space dependence of error propagation.     

Heat transfer in LMFBR fuel elements Part II: Effects of fuel pellet cracks, granular fuel structure and azimuthally non-uniform heat transfer from cladding to bulk coolant

The single long-time method of observation for transmission experiments across boiling channels produces a indecisive value for the mean of the void fraction , and can be correctly interpreted for conditions of low noise level only. The finite interval method is employed in an attempt to determine with much greater accuracy; however, the problem arises that, since the value of (f) over the nth time interval t_n t t_n +δt is assumed approximately constant at _n, this finite period, δt, should be as small s possible whereas reducing δt increases the statistical counting errors. The systematic error introduced by the finiteness of δt is examined and a method is suggested for planning the experiment in such a manner as to minimize statistical counting errors. This method is based on achieving those conditions that ensure the expected variance of an experimentally estimated form of is so small that the estimated form of may be confidently assumed to be very close to its expected mean value.     

基于LSSVM的γ能谱平滑方法

γ能谱平滑的效果直接影响寻峰、解谱的精度,为此需要在消除放射性计数的统计涨落,提高信噪比的同时最大程度地保留能谱特征信息。本文采用基于结构风险化最小准则的最小二乘支持向量机方法 LSSVM,结合交叉验证参数寻优方法对Na I(Tl)γ能谱进行平滑处理,实验结果表明:LSSVM能谱平滑在全谱上保持较好峰形而不形变,各谱峰位置与理论计算值的最大误差(即峰偏)≤0.6个道址,平均误差为0.43个道址;且该方法具备良好的适应性和推广能力。     

多家数据样条拟合

研究发展了多家数据的样条函数拟合方法,编写了实用的计算程序。方法、程序作了如下改进:任意阶样条函数作基底;结点的优化;拟合值误差的严格计算。程序已用于实际的核数据评价。     

Bunch-by-bunch longitudinal phase monitor at SSRF

Beam signals captured from a button-type pickup contain multidimensional information including the bunch charge,transverse position,bunch length,and longitudinal phase.A bunch phase monitor,which retrieves longitudinal phase information from a pickup signal at a bunch-by-bunch rate,has been developed at the Shanghai Synchrotron Radiation Facility.This paper introduces the basic principles,system setup,data processing method,and preliminary experimental results of this system.The systematic measurement error introduced by the limited system bandwidth,bunch length,and bunch charge variation was studied using simulation data.The random measurement uncertainty was evaluated using experimental beam data.The experimental result shows that the longitudinal phase resolution of this system is better than 1.0 ps.The first application,measuring the relationship between the longitudinal phase and bunch charge to determine the energy loss factor,was implemented,and the preliminary result is also discussed.