Evaluation of thermal stability in deep geological repository and nuclear criticality safety of spent nuclear fuel vitrified in iron phosphate glass

Iron phosphate glasses with low melting temperatures of similar to 1300 degrees C were developed to immobilize spent nuclear fuels (SNFs). The glasses have densities of similar to 3.15 g/cm(3) and glass transition temperatures of similar to 540 degrees C that are high enough to endure the temperatures in geological repositories. The waste loading of CeO2 in the glass was similar to 21.92 wt%, which corresponds to similar to 30.38 wt% of UO2 at the same molar ratio. Normalized elemental releases from the product consistency test were well below the regulated limit of 2 g/m(2). Effective neutron multiplication factor k(eff) was 0.755, which is below nuclear criticality safety regulation (k(eff) = 0.95). Vitrified SNF occupies one-eleventh of the repository space compared to direct disposal of the same amount of UO2, excluding left-over low-level wastes. (C) 2019 Elsevier Ltd. All rights reserved.