Developing Waste Forms for Transuranic Elements: Quaternary Neptunium Fluorides of the Type NaxMNp6F30 (M = Ti, V, Cr, Mn, Fe, Co, Ni, Al, Ga)

Travis K Deason; Gregory Morrison; Amir Mofrad; Hunter B Tisdale; Jake Amoroso; David DiPrete; Gary Was; Kai Sun; Theodore M Besmann; Hans-Conrad Zur Loye

doi:10.1021/jacs.2c10669

Developing Waste Forms for Transuranic Elements: Quaternary Neptunium Fluorides of the Type Na_xMNp₆F₃₀ (M = Ti, V, Cr, Mn, Fe, Co, Ni, Al, Ga)

J Am Chem Soc. 2023 Jan 11;145(1):465-475. doi: 10.1021/jacs.2c10669. Epub 2022 Dec 19.

Authors

Travis K Deason^{1

2

3}, Gregory Morrison^{1

2}, Amir Mofrad^{1

4}, Hunter B Tisdale^{1

2}, Jake Amoroso^{1

3}, David DiPrete^{1

3}, Gary Was^{1

5}, Kai Sun^{1

6}, Theodore M Besmann^{1

4}, Hans-Conrad Zur Loye^{1

2

3}

Affiliations

¹ Center for Hierarchical Waste Form Materials, University of South Carolina, Columbia, South Carolina29208, United States.
² Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina29208, United States.
³ Savannah River National Laboratory, Aiken, South Carolina29803, United States.
⁴ Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina29208, United States.
⁵ Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2301 Bonisteel Blvd., Ann Arbor, Michigan48109, United States.
⁶ Department of Materials Science and Engineering, University of Michigan, 3062 H.H. Dow, Ann Arbor, Michigan48109, United States.

PMID: 36534937
DOI: 10.1021/jacs.2c10669

Abstract

A series of quaternary Np(IV) fluorides was synthesized using a mild hydrothermal synthesis approach. The compositions are all of the type Na_xMNp₆F₃₀, where M = Ti(III), V(III), Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Al(III), and Ga(III) and x = 4 for divalent metals, x = 3 for trivalent metals. The compounds all crystallize in the P-3c1 space group and are isotypic with actinide analogues Na_xMAn₆F₃₀ (An = Ce, U, Th, Pu). Structure data from the neptunium crystals were combined with data from the other actinide analogues to establish the tetravalent, nine-coordinated ionic radii of neptunium (1.030(2) Å), plutonium (1.014(1) Å), and cerium (1.012(2) Å). Radiation damage studies were also carried out on a surrogate material, the cerium analogue Na₃AlCe₆F₃₀, which indicates that the structure type has low resistance to amorphization. Density functional theory calculations were carried out to compute the band gaps and enthalpies of formation variations among the isotypic cerium and actinide structures to compare the stability of the structures.