Environmental radiation dosimetry by the small OSL reader

Aluminum Oxide is well known as a TLD material for environmental dose measurement. The use of aluminum oxide TLD became popular due to its high sensitivity, small fading, and physical stability. However the TL material was not easy to analyze due to thermal quenching and light fading effect. The development of Optically Stimulated Luminescence (OSL) method made Aluminum Oxide simplified the analytical process and equipment. A light emitting diode (LED) stimulation method was developed, which enabled the development of a compact reader, called microStar. This study was conducted to understand the characteristic of low dose measurement using the microStar and its application for environmental dose measurement. OSL dosimeters (OSLD) were irradiated using a 74 GBq and 7.4 GBq Cs-137 radiation source at National Institute of Radiological Science. Irradiations included various delivered doses from 20 μGy to 1 mGy free in air. The microStar gets good read out results. The microStar can be used for environmental dose measurement. Over 10 microStar readers have been deployed around the Fukushima Daiichi Nuclear Power Plant (NPP) for monitoring members of the general public, workers, and environmental dose. (author)