Schoepite and dehydrated schoepite
- Univ. of Manitoba, Winnipeg, Manitoba (Canada)
- Univ. of New Mexico, Albuquerque, NM (United States)
Schoepite, [(UO{sub 2}){sub 8}O{sub 2}(OH){sub 12}]{center_dot}12H{sub 2}O, dehydrates irreversibly to a defect structure-derivative of {alpha}-UO{sub 2}(OH){sub 2} with composition UO{sub 3}{center_dot}0.75 H{sub 2}O (dehydrated schoepite). Natural crystals change from translucent yellow schoepite to opaque yellow, polycrystalline dehydrated schoepite. The complete transformation occurs in three steps: (1) loss of interlayer H{sub 2}O in schoepite causing collapse of the layers; (2) atomic rearrangement within the sheets from a schoepite-type arrangement to a configuration which may be similar to that of metaschoepite, UO{sub 3}{center_dot}2H{sub 2}O; (3) a second rearrangement to the defect {alpha}-UO{sub 2}(OH){sub 2}-type sheet. Although dehydrated schoepite may transform to stoichiometric {alpha}-UO{sub 2}(OH){sub 2} in water above approximately 290 C, it does not hydrate at any temperature. Schoepite transforms slowly in air at ambient temperature to metaschoepite, although this may take geologically long periods. The transformation of schoepite to dehydrated schoepite can occur rapidly at room temperature if crystals, which have only partially converted to metaschoepite, are subjected to external stress. The oxidation of UO{sub 2} in spent nuclear fuel has been studied because of the potential effects of corrosion products on the durability of spent fuel as a waste form. Schoepite and dehydrated schoepite have been identified as corrosion products on UO{sub 2} and spent UO{sub 2} nuclear fuel exposed to oxidizing, aqueous solutions.
- DOE Contract Number:
- FG03-95ER14540
- OSTI ID:
- 264441
- Report Number(s):
- CONF-951155--; ISBN 1-55899-315-0
- Country of Publication:
- United States
- Language:
- English
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