Study of the minimum detectable activity in gamma-ray spectrometry with various shielding configurations

Abstract

In the environmental radioactivity analyzing methods using gamma-ray spectrometry, the natural activities of radionuclides were required to be higher than the minimum detectable activity (MDA). To reduce MDA, one of the popular methods is to improve the ability of reducing the background radiation of the gamma-ray spectrometry. In this work, we designed the shielding configuration with 5 cm lead and 2 mm copper (thickness of walls and top). The MDAs of gamma-ray spectrometer were 2.6–4.24 times times for 40K (1460.8 keV), 232Th (208Tl- 2614.5 keV) and 238U (214Pb- 352 keV; 214Bi- 609.3 keV, 214Bi- 1764.5 keV). In the other hand, MDA for 238U with this shielding configuration is smaller than the activity of 238U inside surface soils in Vietnam. These results showed that the gamma spectrometer with NaI(Tl) detector and this shielding configuration was suitable for measurements activity of 238U in the environmental samples.

An Advanced Optimization Method to Minimize the Detection Limit of Liquid Scintillation Counter to Measure Low-Level Tritium Activity in Groundwater

“…This was achieved by varying the counting time of the sample [9]. Lequang et al reported reducing the MDA for environmental radioactivity using gamma-ray spectrometry by improving the ability to reduce background radiation [10]. They devised a shielding setup consisting of 5 cm of lead and 2 mm of copper, resulting in the minimum detectable activity (MDA) for 40 K, 232 Th, and 238 U being 2.60 to 4.24 times lower than previous configurations.…”