Kinetics of the Uranium-Steam Reaction

Abstract

Reaction rates of unalloyed uranium with super heated steam at 160°–1400°C and 1 atm pressure have been determined by a thermogravimetric method. Up to 880°C the reaction follows a linear rate law with maximum rates at approximately 300° and 750°C. Above 880°C a parabolic rate law applies for the first 60–120 min, after which corrosion is linear; the oxide formed in the initial period gives protection to the underlying metal, and the subsequent linear rate is as low as that at about 200°C. X‐ray diffraction of the reaction product indicated that uranium dioxide was formed over almost the whole temperature range.

Review of oxidation rates of DOE spent nuclear fuel : Part 1 : nuclear fuel.

“…Comparisons between metal loss rate determined by weight and by hydrogen gas measurements generally show that less than stoichiometric hydrogen is produced. Uranium hydride has been reported as a product of the uranium metal reaction with water 6,7,16,33,67,76 and with water vapor 6,7,16,28,33,76,77,78,79 to account for this difference. The mechanism for uranium hydride formation is complex and not well understood.…”

Reactions of Laser-Ablated Uranium Atoms with H2O in Excess Argon: A Matrix Infrared and Relativistic DFT Investigation of Uranium Oxyhydrides

“…The chemistry of uranium, particularly the hydrolysis reaction, is of major importance in the design of nuclear waste repositories and nuclear fuel reprocessing cycles. , Uranium reactions with water have been studied extensively. In particular, studies have focused on the corrosive effect of steam on uranium fuel elements, which is a major safety concern in the operation of nuclear fission reactors. − Other investigations have examined the kinetics of the uranium reaction with water vapor in the presence of oxygen and/or hydrogen. − It was found that water acts as a catalyst for uranium corrosion in humid air, especially at higher temperatures . The reaction of uranium with water vapor produces binary oxides with concomitant formation of H 2 , as described by the following general equation: Values of the O/U ratio ( x ) of the oxide product vary from 2.0 to 2.2, depending on temperature and water pressure. , However, little is known about the intermediates and the mechanisms of the important gas-phase reaction between uranium and water.…”

Pyrophoricity of Uranium in Reactor Environments

“…Huddle ad (38) The data of Huddle36) andHopkinson indicate that the U-steam reaction rate does not increase monotonically with temperature; but exhibits (38) several maximum below the MP of U. Hopkinson ascribes the maximum near 300 C to the formation of UH3, which, through physical effects, (36) decreases the protective quality of the UO2. Huddle attributed the decrease in rate in the range of 300-600 C to changes in the physical characteristics of the UO2 which increase the resistance of the oxide to oxygen penetration via diffusion paths, or gross structural faults, in the oxide.…”