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Precipitation of Crystalline NpO2 During Oxidative Corrosion of Neptunium-Bearing Uranium Oxides

Published online by Cambridge University Press:  21 March 2011

Robert J. Finch
Robert J. Finch*
Affiliation:
Chemical Technology Division, Argonne National Laboratory, Argonne, IL 60439, USA
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Abstract

We report crystallization of NpO2 during aqueous corrosion of unirradiated Np-bearing U3O8 under nominally oxidizing conditions. Powders of Np0.33U2.67O8 (Np:U = 1:8) were reacted in humid air at 90° and 150°c for several weeks in sealed stainless-steel vessels. Reacted solids were examined by scanning and transmission electron microscopies (SEM and TEM) and X-ray powder diffraction (XRD). Dehydrated schoepite, (UO2)O0.25–z(OH)1.5+2z (0 ≤ z ≤ 0.15), is the predominant U(VI) compound formed in these experiments and is a minor sink for Np (containing 2 wt.% Np, maximum). The primary sink for Np during corrosion of Np0.33U2.67O8 at 150°C is crystalline NpO2, which crystallized within 2 weeks of reaction in humid air. Corrosion of Np0.33U2.67O8 at 90°C resulted in crystallization of approximately equal proportions of crystalline NpO2 and Np2O5 during 16 weeks of reaction in humid air.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 713: Symposium JJ – Scientific Basis for Nuclear Waste Management XXV , 2002 , JJ11.60
Copyright
Copyright © Materials Research Society 2002

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