Simulation Analysis of Ion Chambers for Area Radiation Monitoring System

Abstract

KAERI (Korea Atomic Energy Research Institute) has been developing ion chambers which are used for an area radiation monitoring system. Those ion chambers will be placed in the area where it is necessary to monitor radiation dose all the time. The areas are nuclear plant site, research reactor site, radiation waste disposal site etc.. KAERI is developing a few different types of ion chambers for the above-mentioned purposes. One is an ion chamber having cylindrical shape with the active volume of similar to 1 l. Another one is also a cylindrical type ion chamber with the active volume of similar to 10 l. The smaller ion chamber of those 2 detectors will be installed in the place where a compact detector is required. Those ion chambers can be filled with gases such as air or Ar or Xe. The characteristics of those two ion chambers can be analyzed by simulation study. The simplified design of air-filled detectors (1.2 l and 13.7 l) was made and simulation study was performed by using the code EGSnrc. The energy of parallel radiation beam was varied from 50 keV to 1.5 MeV to analyze the expected ionization currents and dose as function of beam energy. The 100 keV and I MeV point source beams were adopted to investigate the angular dependence of radiation dose absorbed in the detector. We also investigated the change of characteristics of the 1.2 l ion chamber when the type of filled gas is changed from air. The radiation dose was obtained for the cases of Ar and Xe. The same study was also performed when the pressurized air (2 bar) was filled in the detector.