Study On Non-uniformity Of Barreled Radioactive Waste Based On Monte Carlo Method

The production process of nuclear power plant will produce a large amount of radioactive waste,due to its complex composition and the radioactivity of each nuclide is large difference.Generally,it requires classified collection,volume reduction and solidification technology to treat it.In order to improve treatment efficiency,different types of wastes with the same activity level(resin,paper caps,jumpsuits,etc.)are often mixed and loaded in the actual work process.This process aggravates the non-uniform distribution of the radioactivity in the waste bucket,which brings adverse effects to the cleaning control work.In this paper,the Monte Carlo method is used to study the related factors that affect the radioactive distribution of waste drums.The radioactivity characteristics of the 200 L standard barrel were characterized by constructing an equal volume mesh model and geometric weight model that nuclide activity distribution based on “Poisson distribution,Maxwell distribution and uniform distribution”.Specific research contents and conclusions are as follows:1.The simulation model of large object measuring instrument is built,then by the method of control transformation,influence factors(filler material,density,and characteristics of gamma ray energy,etc.)are analyzed,and the results show that the characteristics of the gamma ray energy during 200 ke V～1690ke V,filler material composition negligible influence on the measured results.2.A method was designed to describe the radiation distribution characteristics of standard drums by using normal distribution,and the non-uniformity of barrels was characterized by the ratio of the detection efficiency of uniform distribution to the corresponding detection efficiency of left-sided test(Zq).The results show that the deviation of the test results under95% and 99% confidence conditions is 1.94%～27.33%.3.Sampling functions of Poisson distribution,Maxwell distribution and uniform distribution were used to characterize the characteristics of the standard barrel’s radioactive activity.The numerical size of Zq values that were obtained by the three sampling functions were respectively: Poisson distribution > uniform distribution > Maxwell distribution.4.The finite element analysis method was used to construct an equal volume(150 equal parts)mesh model and a geometric weight(150 points,9 points)model to characterize the radioactive location characteristics of the 200 L standard barrel.Through comparison,it was found that the accuracy of the results of the three sampling methods was all higher than 95%;geometric weight(9 points)model has better convergence than the other two methods;the computing time of the above three sampling model is 310.11 s,312.04 s,8.75 s respectively.the computing speed of the geometric weight(9 points)model is obviously better than the other two methods.