Abstract
This report reviews the findings from dry-, moist- and wet-air oxidation experiments on unused UO{sub 2} fuel specimens at 200-225 degrees C, performed in support of the Dry Storage Program for used CANDU (CANada Deuterium Uranium) fuel. The presence of liquid water, or unsaturated steam, adds to the complexity of air oxidation of UO{sub 2}. The following processes have been identified by using a combination of optical and scanning electron microscopy and X-ray diffraction to detect oxidation products, and are discussed in this report: oxidative dissolution of U(VI) and precipitation of hydrated UO{sub 3}; back-reduction of dissolved U(VI) and precipitation of U{sub 3}O{sub 8} on the UO{sub 2}/U{sub 3}O{sub 7} surface; solid-state surface and grain-boundary oxidation of UO{sub 2} to {beta}-U{sub 3}O{sub 7}; and, preferential dissolution of UO{sub 2} grain boundaries. Although moisture thus adds greatly to the variety of oxidation reactions that can occur on UO{sub 2} surfaces, it does not appear to promote swelling and spalling of the fuel, in spite of the large increase in molar volume associated with formation of the hydrated phase. This conclusion is qualified, however, since variability in the reactivity of fuel specimens, particularly with respect to grain-boundary oxidation, makes it difficult to
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Citation Formats
Taylor, P, Wood, D D, Owen, D G, Hutchings, W G, and Duclos, A M.
Microstructures and phase relationships of crystalline oxidation products formed on unused CANDU fuel exposed to aerated steam and aerated water near 200 degrees C.
Canada: N. p.,
1991.
Web.
Taylor, P, Wood, D D, Owen, D G, Hutchings, W G, & Duclos, A M.
Microstructures and phase relationships of crystalline oxidation products formed on unused CANDU fuel exposed to aerated steam and aerated water near 200 degrees C.
Canada.
Taylor, P, Wood, D D, Owen, D G, Hutchings, W G, and Duclos, A M.
1991.
"Microstructures and phase relationships of crystalline oxidation products formed on unused CANDU fuel exposed to aerated steam and aerated water near 200 degrees C."
Canada.
@misc{etde_10140400,
title = {Microstructures and phase relationships of crystalline oxidation products formed on unused CANDU fuel exposed to aerated steam and aerated water near 200 degrees C}
author = {Taylor, P, Wood, D D, Owen, D G, Hutchings, W G, and Duclos, A M}
abstractNote = {This report reviews the findings from dry-, moist- and wet-air oxidation experiments on unused UO{sub 2} fuel specimens at 200-225 degrees C, performed in support of the Dry Storage Program for used CANDU (CANada Deuterium Uranium) fuel. The presence of liquid water, or unsaturated steam, adds to the complexity of air oxidation of UO{sub 2}. The following processes have been identified by using a combination of optical and scanning electron microscopy and X-ray diffraction to detect oxidation products, and are discussed in this report: oxidative dissolution of U(VI) and precipitation of hydrated UO{sub 3}; back-reduction of dissolved U(VI) and precipitation of U{sub 3}O{sub 8} on the UO{sub 2}/U{sub 3}O{sub 7} surface; solid-state surface and grain-boundary oxidation of UO{sub 2} to {beta}-U{sub 3}O{sub 7}; and, preferential dissolution of UO{sub 2} grain boundaries. Although moisture thus adds greatly to the variety of oxidation reactions that can occur on UO{sub 2} surfaces, it does not appear to promote swelling and spalling of the fuel, in spite of the large increase in molar volume associated with formation of the hydrated phase. This conclusion is qualified, however, since variability in the reactivity of fuel specimens, particularly with respect to grain-boundary oxidation, makes it difficult to distinguish moisture effects. With unused fuel, grain-boundary alteration to U{sub 3}O{sub 7} is the primary process by which oxidation penetrates the fuel near 200 degrees C. Reactions involving water proceed on the specimen surface, and can also follow oxidized grain boundaries and open porosity. Because of differences in the pore and grain-boundary structure of unused and used UO{sub 2} fuel, as well as possible radiolytic processes in the latter, comparisons between these findings and the results of the ongoing CEX-1 (dry controlled-environment experiment) and CEX-2 (moist) used-fuel storage experiments at Whiteshell Laboratories must be made with caution.}
place = {Canada}
year = {1991}
month = {Nov}
}
title = {Microstructures and phase relationships of crystalline oxidation products formed on unused CANDU fuel exposed to aerated steam and aerated water near 200 degrees C}
author = {Taylor, P, Wood, D D, Owen, D G, Hutchings, W G, and Duclos, A M}
abstractNote = {This report reviews the findings from dry-, moist- and wet-air oxidation experiments on unused UO{sub 2} fuel specimens at 200-225 degrees C, performed in support of the Dry Storage Program for used CANDU (CANada Deuterium Uranium) fuel. The presence of liquid water, or unsaturated steam, adds to the complexity of air oxidation of UO{sub 2}. The following processes have been identified by using a combination of optical and scanning electron microscopy and X-ray diffraction to detect oxidation products, and are discussed in this report: oxidative dissolution of U(VI) and precipitation of hydrated UO{sub 3}; back-reduction of dissolved U(VI) and precipitation of U{sub 3}O{sub 8} on the UO{sub 2}/U{sub 3}O{sub 7} surface; solid-state surface and grain-boundary oxidation of UO{sub 2} to {beta}-U{sub 3}O{sub 7}; and, preferential dissolution of UO{sub 2} grain boundaries. Although moisture thus adds greatly to the variety of oxidation reactions that can occur on UO{sub 2} surfaces, it does not appear to promote swelling and spalling of the fuel, in spite of the large increase in molar volume associated with formation of the hydrated phase. This conclusion is qualified, however, since variability in the reactivity of fuel specimens, particularly with respect to grain-boundary oxidation, makes it difficult to distinguish moisture effects. With unused fuel, grain-boundary alteration to U{sub 3}O{sub 7} is the primary process by which oxidation penetrates the fuel near 200 degrees C. Reactions involving water proceed on the specimen surface, and can also follow oxidized grain boundaries and open porosity. Because of differences in the pore and grain-boundary structure of unused and used UO{sub 2} fuel, as well as possible radiolytic processes in the latter, comparisons between these findings and the results of the ongoing CEX-1 (dry controlled-environment experiment) and CEX-2 (moist) used-fuel storage experiments at Whiteshell Laboratories must be made with caution.}
place = {Canada}
year = {1991}
month = {Nov}
}