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

• Published in: Annals of nuclear energy 2020-02, Vol.136, p.107055, Article 107055
• Main Authors: Won Lee, Cheong, Gyun Shin, Sung, Uk Kye, Yong, Heo, Jong
• Format: Article
• Language: English
• Subjects: Deep geological repository; Nuclear criticality safety; Vitrification
• ISSN: 0306-4549; 1873-2100
• DOI: 10.1016/j.anucene.2019.107055

[Display omitted] •Thermally stable iron phosphate glass for immobilization of spent nuclear fuel was developed.•Iron phosphate glass can contain up to 15 mol% of CeO2, as a surrogate for UO2.•Iron phosphate glass has good chemical durability and nuclear criticality safety.•Repository space can be saved 11 times more than direct disposal by vitrification. Iron phosphate glasses with low melting temperatures of ∼1300 °C were developed to immobilize spent nuclear fuels (SNFs). The glasses have densities of ∼3.15 g/cm3 and glass transition temperatures of ∼540 °C that are high enough to endure the temperatures in geological repositories. The waste loading of CeO2 in the glass was ∼21.92 wt%, which corresponds 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/m2. Effective neutron multiplication factor keff was 0.755, which is below nuclear criticality safety regulation (keff = 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.