In highly permeable sedimentary rock formations, U extraction by in-situ leaching techniques (ISR − In-Situ Recovery) is generally considered to have a limited environmental impact at ground level. Significantly, this method of extraction produces neither mill tailings nor waste rocks. Underground, however, the outcome for ²³⁸U daughter elements in aquifers is not well known because of their trace concentrations in the host rocks. Thus, understanding the in-situ mobility of these elements remains a challenge. Two samples collected before and after six months of ISR experiments (Dulaan Uul, Mongolia) were studied with the help of a digital autoradiography technique (DA) of alpha particles, bulk alpha spectrometry, and complementary petrographic observation methods. These techniques demonstrate that before and after leaching, the radioactivity is concentrated in altered and microporous Fe–Ti oxides. Most of the daughter elements of U remain trapped in the rock after the leaching process. DA confirms that the alpha activity of the Fe–Ti oxides remains high after uranium leaching, and the initial secular equilibrium of the ²³⁸U series for ²³⁰Th to ²¹⁰Po daughter elements (including ²²⁶Ra) of the fresh rocks is maintained after leaching. While these findings should be confirmed by more systematic studies, they already identify potential mechanisms explaining why the U-daughter concentrations in leaching water are low.

在高渗透性的沉积岩地层中，通常认为通过原地浸出技术（ISR –原地采收）进行铀提取对地面环境的影响有限。值得注意的是，这种提取方法既不会产生磨矿尾矿，也不会产生废石。然而，在地下，含水层中²³⁸ U子元素的结果并不为人所知，因为它们在基质岩石中的痕量浓度。因此，就地了解这些要素的流动性仍然是一个挑战。在六个月的ISR实验前后收集了两个样品（蒙古的Dulaan Uul），借助α粒子的数字放射自显影技术（DA），体相Alpha光谱测定法和互补的岩相观测方法进行了研究。这些技术表明，浸出前后，放射性集中在改变的微孔Fe-Ti氧化物中。在浸出过程之后，U的大多数子元素仍保留在岩石中。DA确认的Fe-Ti氧化物的α活性保持铀浸出后高，并且初始长期平衡²³⁸ U系列为²³⁰的Th到²¹⁰宝女儿元件（包括²²⁶浸出后保持新鲜岩石的Ra）。尽管这些发现应通过更系统的研究加以证实，但它们已经确定了潜在的机制，可以解释为什么浸出水中的U子浓度低。