Speaker
Description
NaI(Tl) Scintillation detectors are widely used to measure the ambient dose equivalent rate for monitoring environmental gamma radiation. However, NaI(Tl) is limited to identify some gamma-rays from 131I, 134Cs, and 137Cs which are released from the nuclear facilities due to its low energy resolution. Three halide scintillation detectors – LaBr3(Ce), CeBr3, and SrI2(Eu) – were used to measure the ambient dose equivalent rate by measuring gamma-ray energy spectrum. Each scintillation detector was connected to a signal processing unit and the signal processing unit was optimized for pulse-shaping time. G(E) function method was applied to estimate the dose rate from the measured-gamma energy spectrum. Irradiation test was conducted with 137Cs source to each detector system. The exposure dose rate was in the range of 1 – 100 μSv/hr. A 3”x3” NaI(Tl) scintillation detector was exposured to the irradiation test as a reference. The LaBr3(Ce) showed high dose linearity and energy resolution from low to high dose rate condition. The CeBr3 and SrI2(Eu) showed good energy resolution under 30 μSv/hr of ambient dose equivalent rate. From the result, the LaBe3(Ce) was applied to in situ gamma spectrometry system for monitoring environmental radiation near the Fukushima nuclear power plant.
