4th China - South Africa Joint Symposium on Nuclear Physics

Measurements of natural radioactivity in sands using an array of lanthanum -bromide scintillator detectors

Not scheduled

15m

Speaker

Ms Munirat Bashir (Stellenbosch University/iThemba)

Description

LaBr3:Ce detectors have been shown to be 1.2–1.65 times more efficient than NaI:Tl detectors above 350 keV, for 3.8 cm×3.8 cm (1.5 in.×1.5 in.) detectors and have an energy resolution of 2.5–3% at the 662 keV gamma-line of 137Cs, compared to 6–7% for NaI:Tl detectors[1]. The detector crystal has other advantages such as a high scintillation light output with a fast decay time[2]. An array of 8 2in x 2in LaBr3(Ce) scintillators with an XIA PIXIE-16 Digital Signal Processing system data acquisition system will be used to measure sands placed in the centre (17.5 cm from each detector) of the array (with all detectors lying in the horizontal plane) for 12 hours. The gamma-gamma coincidence method has the advantage of virtually eliminating all background peaks that do not exist in coincidence with other peaks, significantly improving detection limits of useful radionuclides[3][4]. By employing a gamma-gamma coincidence condition, the background from the radioisotopes in the LaBr3:Ce scintillator is eliminated, providing a means for improving detection limits[5]. The absolute gamma–ray energy detection efficiency of each detector will be determined and compared. Data from each detector will be analyzed. The activity concentration of 238U, 232Th and 40K in the sands will be determined and compared to certified values. Radiation hazard indices will be calculated for the soil samples and compared to certified values. Reference [1] K. Ciupek, S. Jednoróg, M. Fujak, and K. Szewczak, “Evaluation of efficiency for in situ gamma spectrometer based upon cerium-doped lanthanum bromide detector dedicated for environmental radiation monitoring,” J. Radioanal. Nucl. Chem., vol. 299, no. 3, pp. 1345–1350, 2014. [2] A. Favalli, H. C. Mehner, and F. Simonelli, “Wide energy range efficiency calibration for a lanthanum bromide scintillation detector,” Radiat. Meas., vol. 43, no. 2–6, pp. 506–509, 2008. [3] M. Yoho and S. Landsberger, “Determination of Selenium in coal fly ash via γ–γ coincidence neutron activation analysis,” J. Radioanal. Nucl. Chem., vol. 307, no. 1, pp. 733–737, Jan. 2016. [4] S. Horne and S. Landsberger, “Selenium and mercury determination in biological samples using gamma–gamma coincidence and Compton suppression,” J. Radioanal. Nucl. Chem., vol. 291, no. 1, pp. 49–53, Jan. 2012. [5] A. Drescher et al., “Gamma-gamma coincidence performance of LaBr3:Ce scintillation detectors vs HPGe detectors in high count-rate scenarios,” Appl. Radiat. Isot., vol. 122, no. January, pp. 116–120, 2017.