Structural and chemical insights on the incorporation of americium into zircaloy-derived monoclinic zirconia

Monoclinic zirconia (m-ZrO2) forms on the internal surface of nuclear fuel Zircaloy cladding, acting as a critical barrier against radionuclide release at the fuel-cladding interface. However, the incorporation of minor actinide elements like americium in m-ZrO2 and resultant structural chemistry remains poorly understood. Using a combination of diffraction and high-resolution X-ray spectroscopic techniques, we have examined m-ZrO2 with 5mol%Am doping. We show Am enters m-ZrO2 tetravalently, where its solubility is approximately 1.0 mol%, m-(Am4+ 0.011(7)Zr4+0.989(7))O2, attributed to the large Am4+ cation,where excess Am, that is predominantly trivalent, adopts a C-type (Am4+/3+1-xZr4+x)2O3+x phase in space group Ia-3. The known reversible high temperature phase transformation of m-ZrO2 to tetragonal is further shown to be reduced from 1150 oC to 1050 oC via Am4+ incorporation. The investigation provides critical insight into the chemical reactivity and speciation of minor actinide elements with nuclear fuel cladding related m-ZrO2.

MURPHY Gabriel L.;  GILSON Sara E.;  POPA Karin;  PRIEUR Damien;  SCHENK Sven;  VĂLU Sorin Octavian;  RAMANANTOANINA Harry;  PRUESSMANN Tim;  VITOVA Tonya;  DARDENNE Kathy;  ROTHE Jorg;  COLLE Jean-Yves;  WALTER Olaf;  HUITTINEN N; 

2026-02-02

NATURE PORTFOLIO

JRC142845

2399-3669 (online),   

https://www.nature.com/articles/s42004-025-01857-9,    https://publications.jrc.ec.europa.eu/repository/handle/JRC142845,   

10.1038/s42004-025-01857-9 (online),