Analysis of oxygen shell splitting in hydrothermally grown single crystal ThO₂(200)

Abstract

Single crystals of ThO2 have been synthesized using hydrothermal growth and studied using the X‐ray absorption fine structure (XAFS) technique. The extended X‐ray absorption fine structure (EXAFS) has been extracted from the XAFS and analyzed using a novel, computational Latin hypercube sampling method. The methodology not only confirms the expected space group and crystal structure, it also identifies the origin of a previously reported split O shell. Since EXAFS is a local order analysis technique, the O shell splitting is identified as an O atom occupying an interstitial site. This result is significant for examining O2– transport in a ThO2 matrix and corroborating research indicating partial Th 5f occupancy that is similar to hyper‐stoichiometric UO2+x compounds. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

Thermal Energy Transport in Oxide Nuclear Fuel

“…If melt growth is eschewed because of these assorted shortcomings, the next most common growth techniques dissolve the feedstock under conditions well below the melting point and then crystallize out the feedstock from the solution. Chemical vapor deposition (CVD) or chemical transport (UO 2 , − U x Th 1– x O 2 , and U 1– x Pu x O 2 ), flux (CeO 2 , − ThO 2 , ,,− ,− UO 2 , ,, U x Th 1– x O 2 , and PuO 2 ,− ), and hydrothermal or solvothermal synthesis (CeO 2 , ThO 2 , ,,,− U 1– x Th x O 2 , − UO 2 , − ,− and PuO 2 ) fall into this category and have been employed for the entire AO 2 family. High-quality, well-faceted single crystals of ThO 2 and UO 2 produced using the hydrothermal method are shown in Figure .…”

“…If the melt growth is eschewed because of these assorted shortcomings, the next most common growth techniques dissolve the feedstock under conditions well below the melting point and then crystallize out the feedstock from the solution. Chemical vapor deposition (CVD) or chemical transport (UO2 [228,229,230,231], UxTh1-xO2 [232], and U1-xPuxO2 [233]), flux (CeO2 [234,235,236,237,238,239,240,241], ThO2 [220,223,234,235,236,237,238,242,243,244,245,246,247], UO2 [217,248,249], UxTh1-xO2 [249], and PuO2 [242,250,251,252,253]), and hydrothermal or solvothermal synthesis (CeO2 [254], ThO2 [29,67,179,255,256,257,258,259,260,…”