Study Of The Influencing Factors Of The Thickness Measurement For Fuel Cladding In MCNP

This thesis comes from the horizontal topic research project of Nuclear Power Institute of China.Fuel cladding measurement is one of the most important ndicators for nuclear fuel. An simulated analysis of influencing factors, which is influenceable for计数of the detector on the existing measuring system, is proposed by this thesis and the problem of Lack of stability and which the measuring accuracy is not enough in the system has been resolved. The study has significant industrial application value.After carefully analyzing the development and the key constraint factors of the method of measurement on the nuclear fuel cladding thickness, Putting forward a proposal on account of MCNP’s study, Taking computer simulation as the core, Taking the analog result for reference for optimizing the actual system.To achieve the improving for overall system.In the process of the MCNP simulator investigation,Analysis of the238U’s β energy spectrum, On the calculation of absorption coefficient on fule cladding and the cladding constituent,and then,to raise a point of factors for influencing on the measuring results:Uranium surface density,edge effect,collimator,the detection efficiency of detectors,background,back scatter.Based on the MCNP Modeling calculation of the various factors, To find the respective influence degree,and mapped out the parameter configuration for system optimization.Simulating and analysing the multifarious influencing factors used MCNP,It is Efficient, Targeted,Easily and Inexpensive,liken to the traditional experimental measurement method.The embedded research on MCNP modeling method,and then We took the effective exploration for the technology through the corresponding programme. The main results achieved in this paper are:1、We judged that U decay spectrum range was annexal0.6mm in fuel cladding preliminarily;while the cladding thickness smaller than0.6mm,Count curve informed law of linear reduction.2、Linear attenuation coefficient:μ连续=2.5419(238U);μ2.32MeV=2.1756(2.32MeV);μNi>μSn>μFe>μZr>μCr;The relative error was on the small size.3、Uranium surface density:Different T,Same ρ,Analogue counting was low while the Core thickness was superior;Different ρ,Same T,Analogue counting decreased firstly and Increased gradually secondly until the density was7.256g/cm3;Dimensions of length and width, Analogue counting was low whle the apparent volume was large,It was that linear absorption coefficient was flat.4、The position of the detector was close to the core of fuel element,It was that the count of boundary condition "1" was more,This situation was more accurate.5、Before three thickness:0.385mm,0.5775mm and0.77mm,the count was reduced,but Floating interval was small range,He:0.58%,Air3.93%;After the0.77mm,The count was smooth,He:2.44%,Air:3.59%.6、Collimator:Lead boron polyethylene(PB202,PE-19%、Pb-80%and B4C-1%),Inside radius was4cm,Thickness was2cm.7、The ray shoot the detector directly,Due to the intrinsic of fuel cladding was not core,To provide conditions for P-ray,the count was increased.8、Fuel cladding thickness:DZr=0.835mm,The maximum count was0.0161.