Corrosion Behavior of Uranium Dioxide in Alpha Radiolytically Decomposed Water

The response of the corrosion potential of a U O 2 electrode to oxidants ( H 2 O 2 , O 2 ) produced by the alpha radiolysis of water has been measured in a thin-layer electrochemical cell. This cell allows the electrode to be brought within ∼ 25 μ m of a gold-plated alpha source, thereby ensuring the uniform distribution of radiolytic oxidants in the aqueous solution filling the gap. The kinetics of water radiolysis, coupled with the surface-catalyzed decomposition of H 2 O 2 and diffusive transport of radiolytic species out of the electrode-source gap, was modeled using a finite difference description of the cell and the commercial numerical integration software, Facsimile. Using this approach, the mechanism of U O 2 corrosion in the presence of alpha radiolysis was shown to be dominated by reaction of the fuel with radiolytically produced H 2 O 2 . To explain the results, two surface-catalyzed H 2 O 2 decomposition processes were invoked: one with H 2 to produce H 2 O , and a second process leading to the production of O 2 and H 2 O . For sufficiently high alpha source strengths, the fuel behavior becomes redox-buffered, i.e., independent of alpha source strength, due to the presence of a corrosion product deposit.