Thermal effects on the time build-up patterns of a weather resistant radiophotoluminescence glass (SAPANS)

Abstract

A recently developed weather-resistant radiophotoluminscence (RPL) glass, named “SAPANS”, has a feature of slow time build-up of RPL. This feature could be utilized for the estimation of post-exposure elapsed time in a radiological accident accompanied with an unnoticed radiation exposure. In the present study, thermal effects on the time build-up patterns of RPL from SAPANS (“SAPANS RPL” hereafter) were examined. Small SAPANS samples were irradiated with 160 kV X-rays at 1 Gy(H2O) and the time changes of RPL were observed under six different temperatures: 45 °C, 36 °C, 20 °C, 15 °C, 5.5 °C and −18 °C. It was found that the time build-up of SAPANS RPL was notably accelerated by heating. While the ratio of measured RPL to that after preheating (at 160 °C for 1 h) gradually increased to about 35% at 20 °C in 24 h, it reached nearly 80% at 45 °C, and hardly increased at −18 °C. To investigate the thermal effects on the accuracy of the previously proposed method for estimating a post-exposure elapsed time, samples were placed outdoor for nearly two weeks and the observed time build-up of SAPANS RPL was compared to the estimation based on the temperature change measured at 30-min intervals. A good agreement was seen between the measured and estimated RPL data, which indicates that more precise estimation of the post-exposure elapsed time could be achieved with SAPANS based on the information of thermal history. These findings would be useful to broaden the applicability of SAPANS to retrospective dosimetry as part of nuclear/radiological emergency preparedness.