Research On Determination Of Radon Permeability Coefficient Of Polymer Films

In the high-energy physics research requiring low background,radon is the main error source for detections.Polymer films typically are applied to shielding the damage of radon to detectors in the laboratory.To accurately measure the oscillation signal of reactor neutrinos,the Juno laboratory raise higher requirements to the radon shielding.The stainless steel ball lining in the underground laboratory,radon shielding film,scintillator containers are made of organic polymer films,polymer films with lower radon permeability coefficient are also used in the pool walls,the bottom and the top.In order to select films with good radon shielding effect,the radon permeation performance of polymer films are studied.The research content is divided into four stages.In the first stage,the permeability of radon in polymer films,the related parameters,and the common measurement method of the permeability coefficient in the polymer films are explored by literature survey.The formula for measuring the radon permeability coefficient of the polymer films under steady state is also obtained.In the second stage,The method and deviceof the coefficient of polymer films at steady state with the liquid scintillation counter are further studied based on the literature investigation.In the third stage,the background and the sealing of the recirculating device are measured,and the time that radon concentration distribution in the system reach to steady state is studied.Moreover,the radon permeability coefficients of different polymer films provided by Juno are measured.In the fourth stage,the main environmental factors maybe affect the radon permeability coefficient of polymer films is researched.In the fifth stage,the diffusion process of radon in the polymer film is simulated with the finite difference method,for verifying the accuracy of the counting result and shorten the time.The results show that:the measurement system have low background and good sealing,which is suitable for the subsequent measurement;Different films in the system require different time reach to steady state;The different polymer films measured values show that the several polymer films provided by Juno Laboratory have good effect on shielding the Rn;The environmental humidity and temperature will affect the radon permeability coefficient of polymer films,the coefficient of the films will decrease with the decrease of ambient temperature,which is the general rule of temperature influencing on all films,the coefficient of hydrophilic films will increase with the increase of the environmental humidity,resulting in poor performance in radon shielding;The finitedifference simulation results show that the test values are accurate,and the simulation method can be used to estimate the accuracy of the results,to reduce the repetitions and shorten the time;The measured results with scintillation cell method preliminary verified the accuracy results of the liquid scintillation method.The research measured the radon permeation coefficient of polymer films by liquid scintillation method,which provided an important reference for Juno experiment to choose suitable film.In addition,the study find there are many factors will influence the results.Therefore,some suggestions are put forward at the end of this paper,which helpful for the accurately and effectively measuring of the radon permeability coefficient of the polymer films.