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Experimental and Multiscale Modeling Insights for Radiation-Driven Neptunium Redox Processes at Elevated Temperatures
Amy E Kynman1,2, Travis S Grimes1,2, Stephen P Mezyk1,3
1Radiochemical Separations and Radiation Science Department, Idaho National Laboratory, Idaho Falls, Idaho 83415, United States.
The Journal of Physical Chemistry. A
|June 25, 2026
Summary
This study quantifies the reaction rate of pentavalent neptunium with nitrate radicals at high temperatures, crucial for understanding nuclear fuel reprocessing. The findings refine models of neptunium
Area of Science:
- Nuclear Chemistry
- Radiochemistry
- Chemical Kinetics
Background:
- Radiation-induced reactions of actinides are critical for nuclear fuel reprocessing.
- Elevated temperatures and nitric acid concentrations influence actinide redox behavior.
Purpose of the Study:
- To determine rate coefficients for pentavalent neptunium reacting with nitrate radicals at elevated temperatures.
- To refine multiscale models for radiation-induced neptunium redox chemistry in nitric acid.
Main Methods:
- Derivation of rate coefficients and calculation of Eyring and Arrhenius parameters.
- Revisiting and iterating a multiscale model for neptunium redox chemistry.
Main Results:
- Established rate coefficients for the neptunium-nitrate radical reaction at high temperatures.
- Developed an updated multiscale model effective across a broad range of nitric acid concentrations (0.1-6.0 M).
Conclusions:
- The study provides essential kinetic data for actinide reactions under reprocessing conditions.
- Improved modeling enhances understanding of neptunium's behavior in irradiated nuclear fuel environments.
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