Abstract The ability to identify the sources of nuclear materials using various analytical methods has become a major target of nuclear forensics science. However, despite the emergence of novel tools developed in recent years, it has become obvious that accurate identification of sources requires multiple tools. Here, we have developed a new isotope tool based on Mo isotopes that could be used in nuclear forensics. Molybdenum is a trace element that is found in significant levels in uranium ores (0.5–4800 ppm), uranium minerals (0.02–6000 ppm) and uranium ore concentrates (UOCs, from 0.7 to 1400 ppm). The Mo isotope composition, reported as δ98Mo was analyzed in these materials and shown to have a significant variability from −2.62 to +0.30‰ in uranium ores and from −3.50 to +0.46‰ in UOCs. In uranium ores, the largest Mo isotope fractionation is found in deposits of sedimentary origin while the few ores with a magmatic origin show limited Mo isotope fractionation. Thus, the Mo isotope ratios may ultimately be used to distinguish high temperature from low temperature uranium ores. The δ98Mo values in UOCs also show a significant range that not only originate from variations in ore compositions but can also be attributed to ore processing such as leaching, solvent extraction, resin extraction and UOC precipitation. Laboratory experiments based on existing protocols of uranium ore separation demonstrate the existence of sizeable Mo isotope fractionation associated with these processes. Experiments with solvent extraction and precipitation of ammonium diuranate and peruranate show that the refined uranium fraction is enriched in light Mo isotopes in both cases. In the case of a uranium ore (SOMAIR, Niger) and associated UOC, the observed fractionation can possibly be assigned to the combined effect of solvent extraction and precipitation, although Mo isotope variability in ores and UOCs may make such a diagnostic difficult. Ultimately, these experiments can be used to reconstruct the Mo isotope composition of the ore, if there is sufficient knowledge about the ore processing flowsheet or to provide information about the type of uranium ore. Alternatively, it could be used to identify the process used for manufacturing a given UOC, if one can make an estimate about the composition of the ore, probably in conjunction with other tools. Our study demonstrates the potential of Mo isotopes as a useful tool in the field of nuclear forensics.

中文翻译：

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铀氧化物中和核燃料循环关键过程中的钼同位素分馏：迈向新的核法证工具

摘要 使用各种分析方法识别核材料来源的能力已成为核取证科学的主要目标。然而，尽管近年来开发了新工具，但很明显，准确识别来源需要多种工具。在这里，我们开发了一种基于 Mo 同位素的新同位素工具，可用于核法医学。钼是一种微量元素，在铀矿石 (0.5–4800 ppm)、铀矿物 (0.02–6000 ppm) 和铀精矿 (UOC，0.7 至 1400 ppm) 中含量很高。对这些材料中报告为 δ98Mo 的 Mo 同位素组成进行了分析，结果表明铀矿石中的钼同位素组成从 -2.62 到 +0.30‰ 以及在 UOC 中从 -3.50 到 +0.46‰ 具有显着的变异性。在铀矿中，在沉积成因的矿床中发现了最大的 Mo 同位素分馏，而少数具有岩浆成因的矿石显示出有限的 Mo 同位素分馏。因此，Mo同位素比最终可用于区分高温铀矿石和低温铀矿石。UOC 中的 δ98Mo 值也显示出很大的范围，这不仅源于矿石成分的变化，还可以归因于矿石加工，如浸出、溶剂萃取、树脂萃取和 UOC 沉淀。基于现有铀矿石分离协议的实验室实验表明，存在与这些过程相关的大量 Mo 同位素分馏。用溶剂萃取和沉淀重铀酸铵和过铀酸铵的实验表明，在这两种情况下，精制铀馏分都富含轻钼同位素。在铀矿石（SOMAIR，尼日尔）和相关 UOC 的情况下，观察到的分馏可能归因于溶剂萃取和沉淀的综合影响，尽管矿石和 UOC 中的 Mo 同位素变异性可能使这种诊断变得困难。最终，如果对矿石加工流程有足够的了解或提供有关铀矿石类型的信息，这些实验可用于重建矿石的 Mo 同位素组成。或者，如果可以对矿石的成分进行估计，则可以使用它来确定用于制造给定 UOC 的过程，可能与其他工具结合使用。我们的研究证明了 Mo 同位素作为核法医学领域有用工具的潜力。