Preparation of in-house reference soil sample containing high levels of naturally occurring radioactive materials from the oil industry

An in-house reference soil sample containing high levels of naturally occurring radioactive materials collected from contaminated areas in the Syrian oilfields has been prepared as a part of the quality assurance program in AECS. Homogeneity of the sample has been examined using three methods, viz. particle size distribution of the sample matrix, total alpha/beta counting and gamma spectrometry. In conjunction with Dixon and Grubb tests as statistical tools, ten random samples from the original sample were used for this investigation. Reference values for the three radium isotopes (224Ra, 226Ra, 228Ra) were determined using gamma spectrometry equipped with HPGe detectors having high relative efficiencies of 80%, while the reference value of 210Pb in the sample was determined using radiochemical separation and counting of its daughter 210Po by alpha spectrometry. ANOVA analysis was used to estimate the uncertainties due to measurement and inhomogeneity of the sample; uncertainty due to inhomogeneity was found to be around 2.6 times the measurement uncertainty.