A low-level environmental radiation monitor using optically stimulated luminescence from Al2O3:C: Tests using 226Ra and 232Th sources

Abstract

Abstract This paper reports results from a high-sensitivity, remote gamma dosimetry system for subsurface monitoring of arbitrary environments (e.g. the immediate vicinity of nuclear waste storage facilities) that fills the gap between the complexity of active electronic detectors emplaced in soil, such as NaI scintillators and Ge semiconductors for gamma spectroscopy, and conventional, invasive removal of soil and water samples for off-site analysis. The portable system described herein is based on the pulsed optically stimulated luminescence of a carbon-doped aluminum oxide (Al 2 O 3 :C) single-crystal dosimeter, and was tested using two radionuclides relevant to environmental radiation monitoring, namely 226 Ra in liquid form and 232 Th. The system was calibrated against NIST-traceable sources, and the minimum detectable dose was found to be ∼3 μGy. Also, Monte Carlo calculations based on the 226 Ra experimental geometry showed close agreement (2%) with the measured dose value. We conclude that the system described has potential utility as a sensitive, low-level monitoring device suitable for in-situ measurements of environmental gamma radiation levels.