The corrosion and the consequent radionuclide release rate of the fuel will be controlled by the redox conditions produced at the fuel surface by the radiolysis of water (to produce predominantly H2O2 and H2) and by the anoxic corrosion of the steel vessel in the presence of groundwater to produce the potential reductants Fe2+ and H2. [...] The conductivity of UO2 can be increased by either the introduction of OI atoms into the many available lattice locations, as indicated in Figure 1, or by the replacement of a fraction of UIV atoms in the matrix by lower valent species which create holes in the 5f band, with charge balance maintained by the creation of an equivalent concentration of UV atoms (Shoesmith et al. [...] The irradiation history of spent fuel is characterized by its power rating and burn-up, with the radionuclide inventory at the time of emplacement of the waste in the DGR depending on how long it has been since its discharge from the reactor. [...] 5.1 The Instant Release Fraction (IRF) Determination of the IRF requires knowledge of the radionuclide inventories, the half lives and decay sequences of the individual radionuclides, and analytical measurements of the gap and grain boundary inventories. [...] 5.2 The Influence of Redox Conditions The release of > 90% of radionuclides contained within the fuel matrix (the matrix inventory (iii)) will be governed by the corrosion/dissolution of the fuel.
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- Canada
