Grain boundary facilitated dissolution of nanocrystalline NpO2(s) from legacy waste processing

Kathryn M. Peruski; Kelliann C. Koehler; Brian A. Powell

doi:10.1039/d0en00262c

Grain boundary facilitated dissolution of nanocrystalline NpO₂(s) from legacy waste processing

Kathryn M. Peruski, Kelliann C. Koehler, Brian A. Powell

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

Dissolution of actinide dioxides, including neptunium dioxide (NpO2(s)), is paramount for the prediction of the environmental fate of nuclear materials. Quantifying dissolution rates, as well as understanding qualitative dissolution mechanisms, informs performance assessment for geologic disposal of spent nuclear fuel and management of legacy radioactive waste. The aim of this research was to measure the dissolution rate of nanocrystalline NpO2(s), produced through legacy nuclear waste processing, under oxidizing conditions, as well as to characterize surface alteration to the material. The solid phase was characterized using electron microscopy techniques (SEM/STEM) and X-ray photoelectron spectroscopy (XPS), indicating preferential dissolution of Np-hydroxide contained in the grain boundaries of NpO2(s) and fragmentation of grains from the matrix. The oxidative dissolution was monitored over 40 weeks, yielding a two-step kinetic dissolution model involving hydration of NpO2(s) and subsequent oxidation and dissolution of the hydroxide phase. The proposed dissolution models for nanocrystalline NpO2(s) suggest that microstructural features such as grain boundaries are key factors affecting dissolution, including release of colloidal particles, and ultimately, environmental fate and transport of nuclear materials.

Original language	English
Pages (from-to)	2293-2301
Number of pages	9
Journal	Environmental Science: Nano
Volume	7
Issue number	8
DOIs	https://doi.org/10.1039/d0en00262c
State	Published - Aug 2020
Externally published	Yes

Funding

The authors thank Dr. Philip Almond of Savannah National Laboratory for providing the PXRD pattern of NpO2Ĳs). This work is supported by the U.S. Department of Energy (DOE) Office of Science, Office of Basic Energy Sciences and Office of Biological and Environmental Research under Award Number DE-SC-00012530. The authors thank Dr. Philip Almond of Savannah National Laboratory for providing the PXRD pattern of NpO2(s). This work is supported by the U.S. Department of Energy (DOE) Office of Science, Office of Basic Energy Sciences and Office of Biological and Environmental Research under Award Number DE-SC-00012530.

Funders	Funder number
Office of Basic Energy Sciences
Office of Biological and Environmental Research
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Biological and Environmental Research	DE-SC-00012530

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1039/d0en00262c

Cite this

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title = "Grain boundary facilitated dissolution of nanocrystalline NpO2(s) from legacy waste processing",

abstract = "Dissolution of actinide dioxides, including neptunium dioxide (NpO2(s)), is paramount for the prediction of the environmental fate of nuclear materials. Quantifying dissolution rates, as well as understanding qualitative dissolution mechanisms, informs performance assessment for geologic disposal of spent nuclear fuel and management of legacy radioactive waste. The aim of this research was to measure the dissolution rate of nanocrystalline NpO2(s), produced through legacy nuclear waste processing, under oxidizing conditions, as well as to characterize surface alteration to the material. The solid phase was characterized using electron microscopy techniques (SEM/STEM) and X-ray photoelectron spectroscopy (XPS), indicating preferential dissolution of Np-hydroxide contained in the grain boundaries of NpO2(s) and fragmentation of grains from the matrix. The oxidative dissolution was monitored over 40 weeks, yielding a two-step kinetic dissolution model involving hydration of NpO2(s) and subsequent oxidation and dissolution of the hydroxide phase. The proposed dissolution models for nanocrystalline NpO2(s) suggest that microstructural features such as grain boundaries are key factors affecting dissolution, including release of colloidal particles, and ultimately, environmental fate and transport of nuclear materials.",

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AU - Koehler, Kelliann C.

AU - Powell, Brian A.

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