Abstract Neptunium poses challenges for radioactive wastes management due to its long half-life and ingrowth from americium decay, as well as its high mobility in water in its oxidized forms. Np(V)-bearing aqueous solutions were contacted with polished and crushed gneiss and dolerite from the Yeniseisky site, Russia, which is under consideration as a location for an underground repository, both in oxic and anoxic conditions at 20 and 90 °C. Neptunium sorption on crushed gneiss and dolerite in oxic conditions at 20 °C was quite low, but increased substantially in anoxic conditions. Autoradiography on samples treated at 20 °C revealed that sorbed Np was associated mostly with dark colored iron-bearing minerals, and solvent extraction indicated partial reduction of Np(V) to Np(IV). Sorption of Np from aqueous solutions contacted with dolerite and gneiss at 90 °C was in all cases higher than at the lower temperature. Autoradiography of polished rock samples treated in anoxic conditions at 90 °C revealed that Fe-bearing minerals had 3–4 orders of magnitude more Np sorbed on them than the quartz and feldspar grains. X-ray photoelectron spectroscopy indicated this sorbed Np was present as NpO2. This study supports the concept that the geologic conditions present at the planned repository site will retard Np migration.

中文翻译：

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在好氧和缺氧条件和不同温度下，矿物特定的异质镎吸附到地质储存库岩石上

摘要 由于镎半衰期长、镅衰变向内生长，以及在水中以氧化形式存在的高流动性，镎给放射性废物管理带来了挑战。含 Np(V) 的水溶液与来自俄罗斯叶尼塞斯基遗址的抛光和压碎的片麻岩和辉绿岩接触，该遗址正在考虑作为地下处置库的位置，在 20 和 90 °C 的好氧和缺氧条件下。在 20 °C 的有氧条件下，碎片麻岩和辉绿岩上的镎吸附量非常低，但在缺氧条件下显着增加。在 20 °C 下处理的样品的放射自显影显示，吸附的 Np 主要与深色含铁矿物相关，溶剂萃取表明 Np(V) 部分还原为 Np(IV)。在 90 °C 下与辉绿岩和片麻岩接触的水溶液中 Np 的吸附在所有情况下都高于在较低温度下的吸附量。在 90 °C 缺氧条件下处理的抛光岩石样品的放射自显影显示，含铁矿物吸附在其上的 Np 比石英和长石颗粒高 3-4 个数量级。X 射线光电子能谱表明这种吸附的 Np 以 NpO2 的形式存在。这项研究支持这样一个概念，即计划中的处置地点存在的地质条件会阻碍 Np 迁移。X 射线光电子能谱表明这种吸附的 Np 以 NpO2 的形式存在。这项研究支持这样一个概念，即计划中的处置地点存在的地质条件会阻碍 Np 迁移。X 射线光电子能谱表明这种吸附的 Np 以 NpO2 的形式存在。这项研究支持这样一个概念，即计划中的处置地点存在的地质条件会阻碍 Np 迁移。