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含铀岩石γ能谱的大多数强光电峰,属于~(222)Rn的子代衰变产物。为了测定铀含量,通常要测量与铀处放射性平衡的核素的弱光电峰(~(234)Th的63千电子伏或~(234)Pa的1001千电子伏)。根据1001千电子伏光电峰测定铀的灵敏度不高,因为该能量γ量子的产额较低(8×10~(-3)γ量子/衰变~(238)U)。要记录63千电子伏的低能γ量子,最好使用小体积半导体探测器,但由于γ辐射在样品内的强烈自吸收,分析灵敏度仍然不够。
Most of the strong electric peaks of γ-ray spectra of uranium-bearing rocks belong to the progeny decay products of ~ (222) Rn. In order to determine the uranium content, the weak photoelectron peak of nuclides that are radioactively balanced with uranium (63 keV at ~ (234) Th or 1001 keV at ~ (234) Pa) is usually measured. The sensitivity of uranium is not high due to the 1001 keV peak because the yield of gamma energy quantum is low (8 × 10 -3 γ quantum / decay ~ (238) U). To record a low-energy γ quantum of 63 keV, it is better to use a small-volume semiconductor detector, but analytical sensitivity is not sufficient due to the strong self-absorption of gamma radiation in the sample.