1987 Volume 22 Issue 3 Pages 269-276
The present study was conducted to develop a finger dosimeter for beta-rays and to investigate a practical method for estimating, ‘maximum shallow dose equivalent’, as secondary limit of protection standard. The developped dosimeter is consisted of two Li2B4O7(Cu) TL elements, Al-shield and polyethylene case. To examine the relationship between the maximum shallow dose equivalent and receptor air dose measured by this dosimeter, dose distribution at various depths within a surface layer of human body was calculated by the Monte Carlo method in the case of irradiation from 35S, 147Pm, 45Ca 133Xe 131I, 85Kr, 204Tl 198Au 133I 32P and 90Sr-90Y. We used a model, such as receptor and dosimeter exposed to beta-rays under conditions of parallel beam with angles of incidence, 15°, 30°, 45°, 60°, 75° and 90°. Moreover, we irradiated the dosimeter with the sources of 35S, 131I, 198Au, 32P and 90Sr-90Y to verify the results of the calculation and to estimate minimum detectable dose of this dosimeter. Main results were as follows; 1) The point of maximum shallow dose equivalent for beta-rays was located at the depth of 7mg/cm2. 2) The conversion factors for receptor air dose to maximum shallow dose equivalent for beta-rays depended on the energies and angles of incidence of beta-rays. But, using the energy indexes which were difined as ratios of measured values of two TL elements, the conversion factors were decided independently of the energies and angles of incidence of beta-rays. 3) Minimum detectable dose of this dosimeter was 0.02mGy for beta-rays.
