Isotopic composition of uranium has previously been used to infer the depositional redox environment of uranium ore concentrates and also provide a potential signature to inform nuclear forensic investigations. This study evaluates the diagnostic power of the U isotope signature by investigating (1) the heterogeneity of U isotope compositions in samples collected from the same mine and/or vein, and (2) the influence of U ore processing on ²³⁸U/²³⁵U and ²³⁴U/²³⁸U ratios. These characteristics are explored via high precision mass spectrometric measurement of vein type uranium ore samples collected predominantly from mines located in central Portugal and Southwest England. Samples collected from the same vein and mine exhibit δ²³⁸U values from −0.16 to +0.03 (±0.04) ‰ and −1.6 to −64.7 (±0.4) ‰ for δ²³⁴U (±2SD). These variations can be attributed to redox-driven isotope fractionation processes and/or U redistribution during localised leaching and re-precipitation. Analyses of residues and leachates from small-scale batch experiments designed to simulate industrial U ore leaching procedures reveal significant positive and negative changes in isotope composition in the leachate relative to the bulk material (up to 0.21 ± 0.06‰ for δ²³⁸U and 62.0 ± 0.6‰ for δ²³⁴U). These findings highlight the possibility of significantly different δ²³⁸U and δ²³⁴U of uranium ore concentrate from the same mine even if manufacturing processes remain unchanged.

铀的同位素组成以前曾被用来推断铀精矿的沉积氧化还原环境，也为核法证研究提供了可能的标志。本研究通过调查 (1) 从同一矿山和/或矿脉收集的样品中 U 同位素组成的异质性，以及 (2) U 矿石加工对²³⁸ U/ ²³⁵ U的影响来评估 U 同位素特征的诊断能力和²³⁴ U/ ²³⁸ U 比率。这些特征是通过对主要从位于葡萄牙中部和英格兰西南部的矿山收集的脉状铀矿石样品进行高精度质谱测量来探索的。从同一矿脉和矿山采集的样品显示δδ ²³⁴ U (±2SD) 的²³⁸ U 值从 -0.16 到 +0.03 (±0.04) ‰ 和 -1.6 到 -64.7 (±0.4) ‰ 。这些变化可归因于氧化还原驱动的同位素分馏过程和/或局部浸出和再沉淀过程中的 U 重新分布。对设计用于模拟工业 U 矿浸出程序的小规模批次实验中的残留物和浸出液进行分析，结果表明浸出液中同位素组成相对于散装材料有显着的正负变化（δ ²³⁸ U 和 62.0 ±高达 0.21 ± 0.06‰）δ ²³⁴ U为 0.6‰ ）。这些发现强调显著不同δ的可能性，²³⁸ U和δ ²³⁴即使制造工艺保持不变，来自同一矿山的铀精矿的U含量也相同。