Selection of duration of gamma-spectral sampling of uranium-thorium ores

Abstract

As it is known, a significant part of the error of uranium and thorium content determination by gamma-spectral method is a statistical error. Unfavorable conditions of measurement are formed first of all for scintillators of small size. So, to provide with NaJ(Tl) crystals, 18x30 mm, the error of U and Th determination not more than 10% in ores with the content of these elements 0,03%, the measurement exposure should be about 10 min. If, however, when calculating the content of U and Th from gamma-spectral data to use not the count rate of pulses, and the area of gamma-spectral logging diagrams recorded by the recorder or built on the results of point measurements in the optimal energy intervals of the gamma-spectrum, the error in determining the area of the curve is relatively small even with a small exposure measurement of the count rate of pulses.