基于蒙特卡罗方法的氪-85活度反演中容器参数的分析研究OA

During the detection of releasers from nuclear fuel plants,the isotope 85Kr presents a challenge due to its exceptionally low γ branching ratio of approximately 0.434%and the complex bremsstrahlung mechanism that follows β radiation,where the branching ratio exceeds 99.5%.This complexity complicates the precise inversion of 85Kr activity within a sealed container.To investigate the interference effects under realistic working conditions,a cylindrical three-dimensional model was developed.Dynamic analyses were performed to assess the effects of varying container wall thickness(0.5-1.5 mm),container material(aluminum,brass,stainless steel),85Kr source gas pressure(1.0-5.0 atm),and container inner diameter(1.9-5.9 cm).The dose rate response function and bremsstrahlung radiation leakage ratio were compared across these variables.The results indicate that:(1)The wall thickness of the container is significantly negatively correlated with the proportion of bremsstrahlung leakage,leading to nonlinear distortion of the dose rate response function in the near-field area.This finding suggests that wall thickness tolerance is a primary source of systematic error;(2)Low-Z materials,such as aluminum,due to small photoelectric cross-sections and low mass thicknesses,exhibit poor self-absorption of low-energy photons,resulting in a markedly higher proportion of bremsstrahlung leakage compared to high-Z materials,such as brass;(3)The gas pressure of the radioactive source demonstrates a significant positive correlation with the proportion of bremsstrahlung radiation leakage.However,under the same detection distance,the dose-rate response function remains largely unchanged;(4)The inner diameter of the container reveals a significant nonlinear relationship with the proportion of bremsstrahlung leakage.Nevertheless,containers with a larger inner diameter substantially reduce the effective detection efficiency per unit activity.This research establishes a correction model for geometric parameters and pressure variations within the container during the 85Kr activity inversion process,thereby providing a theoretical foundation for enhancing the accuracy of the 85Kr online monitoring system and the precision of the inversion system,which holds considerable reference value for engineering applications.