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

Abstract

As is known, a significant part of the error in determining uranium and thorium content by the gamma‑spectral method is statistical error. Unfavourable measurement conditions arise primarily for small‑size scintillators. Thus, to ensure with NaJ(Tl) crystals, 18×30 mm, a determination error of U and Th of no more than 10% in ores with a content of these elements of 0.03%, the measurement exposure should be about 10 min. If, however, when calculating the content of U and Th from gamma‑spectral data, one uses not the pulse count rates but the area of gamma‑spectral logging diagrams recorded by a recorder or constructed from 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 time for measuring the pulse count rate.

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