Careful manipulation of the plutonium oxidation states is essential in the study and utilization of its rich redox chemistry. To achieve this level of control, a comprehensive mechanistic understanding of radiation-induced plutonium redox chemistry is critical due to the unavoidable exposure of plutonium to ionizing radiation fields, both inherent and from in-process applications. To this end, we have developed an experimentally evaluated multiscale computer model for the prediction of gamma radiation-induced Pu(IV) redox chemistry in concentrated nitric acid solutions (1.0, 3.0, and 6.0 M). Under these acidic, aqueous solution conditions, cobalt-60 gamma irradiation afforded marginal net conversion of Pu(IV) to Pu(VI), the extent of which was dependent on the concentration of HNO₃ and absorbed gamma dose. Multiscale calculations, which are in excellent agreement with experimental data, indicate that this observation is due to a combination of inherent plutonium disproportionation reactions and several radiation-induced processes, including redox cycling between Pu(IV) and Pu(III), as achieved by the reduction of Pu(IV) by nitrous acid and hydrogen peroxide, the oxidation of Pu(III) by nitrate and hydroxyl radicals, and the sequential oxidation of Pu(IV) to Pu(V) and Pu(VI) by the remaining available yield of nitrate radicals.

中文翻译：

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硝酸溶液中钚辐射化学的多尺度建模。 1. Pu(IV) 的钴 60 伽马辐照

仔细控制钚的氧化态对于研究和利用其丰富的氧化还原化学至关重要。为了实现这种控制水平，对辐射引起的钚氧化还原化学的全面机械理解至关重要，因为钚不可避免地暴露在电离辐射场中，无论是固有的还是过程中的应用。为此，我们开发了一种经过实验评估的多尺度计算机模型，用于预测浓硝酸溶液（1.0、3.0 和 6.0 M）中伽马辐射诱导的 Pu(IV) 氧化还原化学反应。在这些酸性水溶液条件下，钴 60 伽马辐射提供了 Pu(IV) 至 Pu(VI) 的边际净转化，其程度取决于 HNO ₃的浓度和吸收的伽马剂量。多尺度计算与实验数据非常吻合，表明这一观察结果是由于固有的钚歧化反应和几种辐射诱导过程的结合，包括 Pu(IV) 和 Pu(III) 之间的氧化还原循环，如通过亚硝酸和过氧化氢还原 Pu(IV)，硝酸盐和羟基自由基氧化 Pu(III)，以及剩余可用物质将 Pu(IV) 依次氧化为 Pu(V) 和 Pu(VI)硝酸根的产量。