Generation and Study of Am(IV) by Temperature-Controlled Electron Pulse Radiolysis

Conference · Sat Mar 08 00:00:00 EST 2025

DOI:https://doi.org/10.1039/D4DT00991F· OSTI ID:2565666

Kynman, Amy Elizabeth ^[1]; Grimes, Travis S ^[1]; Holmbeck, Gregory Peter ^[1]

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1. Idaho National Laboratory

Used nuclear fuel (UNF) separation techniques that strive to separate radiotoxic americium (Am) from trivalent lanthanide fission products through oxidation state control have increased research efforts surrounding Am(V) and Am(VI). However, equivalent knowledge of the tetravalent state, Am(IV), has remained elusive, particularly in conditions more representative of UNF reprocessing, i.e., in concentrated nitric acid (HNO3). With this in mind, we have used electron pulse radiolysis to study the radiation-induced redox reaction of Am(III) with the oxidizing nitrate radical (NO3?) in 6 M HNO3: Am(III) + NO3? ? Am(IV) + NO3? . These experiments enabled us to observe the growth and decay of Am(IV) in a concentrated acidic solution for the first time. The transient Am(IV) species was found to have a lifetime of ~16 µs?sufficiently long-lived to play a critical mechanistic role in UNF reprocessing systems. Additionally, we performed the first-ever temperature-dependent kinetics study of an actinide element, elucidating unprecedented Arrhenius and Eyring activation parameters for the reaction of Am(III) with NO3?. This new knowledge provides much-needed molecular-level insights into the radiation-induced behavior of Am.

• Research Organization: Idaho National Laboratory (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: 58
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 2565666
• Report Number(s): INL/CON-25-83334-Rev000
• Conference Information: Gordon Research Conference and Seminar - Inorganic Reaction Mechansims, Pomona, California, 03/08/2025 - 03/14/2025
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
actinide
americium
pulse radiolysis
radiation chemistry
radiochemistry
redox