Long-term C-14 source term for a high-level waste repository

• Published in: Waste management (Elmsford) Vol. 14; no. 5; pp. 393 - 408
• Main Author: Ahn, Tae M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.1994
• Subjects: Containers; Corrosion; Degradation; Dissolution; Fission products; Geological repositories; Light water reactors; Nuclear fuel cladding; Oxidation; Oxides; Spent fuels; Uranium compounds; USA, Nevada, Yucca Mt
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/0956-053X(94)90044-2

This paper evaluates the possibility of long-term Carbon-14 (C-14) releases from spent fuels and containers in the anticipated environments of the proposed Yucca Mountain high-level waste repository. Long-term degradation mechanisms of spent fuel matrices, cladding, and containers are evaluated. Under dry conditions, formation of higher oxides, such as U 3 O 8, may lead to significant C-14 releases from the spent fuel matrix. It is unclear whether there will be significant C-14 releases from lower oxidation to UO 2.3 or from the unoxidized matrix. Under aqueous dissolution conditions, C-14 releases from the spent fuel matrix can be significant. Under aqueous dissolution or dry conditions, it is unlikely that there will be significant C-14 releases from cladding, unless severe localized corrosion takes place. In considering containers and cladding as metallic barriers, we discuss qualitatively various factors governing total C-14 containment inside metallic barriers. C-14 releases can be delayed, even by the formation of small through-wall pits in metallic barriers. Although we do not have completely definitive information yet, it is clear that the spent fuel matrix, cladding, and containers can serve as important barriers to C-14 releases from waste packages in a repository environment.