Environmental release of carbon-14 gas from a hypothetical nuclear waste repository
- Rogers & Associates Engineering Corporation, Salt Lake City, UT (United States)
Radioisotopes may form gases in a spent nuclear fuel waste package due to elevated temperatures or degradation of the fuel rods. Radioactive carbon-14, as gaseous carbon dioxide, is one of the gaseous radioisotopes of concern at an underground disposal facility for spent nuclear fuel and high-level radioactive waste. Carbon-14 dioxide may accumulate inside an intact waste container. Upon breach of the container, a potentially large pulse of carbon-14 dioxide gas may be released to the surrounding environment, followed by a lower, long-term continuous release. If the waste were disposed of in an unsaturated geologic environment, the carbon-14 gas would begin to move through the unsaturated zone to the accessible environment. This study investigates the transport of radioactive carbon-14 gas in geologic porous media using a one-dimensional analytical solution. Spent nuclear fuel emplaced in a deep geologic repository located at a generic unsaturated tuff site is analyzed. The source term for the carbon-14 gas and geologic parameters was obtained from previously published materials. The one-dimensional analytical solution includes diffusion, advection, radionuclide retardation, and radioactive decay terms. Two hypothetical sites are analyzed. One is dominated by advective transport, and the other is dominated by diffusive transport. The dominant transport mechanism at an actual site depends on the site characteristics. Results from the simulations include carbon-14 dioxide travel times to the accessible environment and the total release to the environment over a 10,000-year period. The results are compared to regulatory criteria.
- Research Organization:
- Arizona Univ., Tucson, AZ (United States). Coll. of Engineering and Mines; New Mexico State Univ., University Park, NM (United States); Waste-Management Education and Research Consortium (WERC), Las Cruces, NM (United States); USDOE, Washington, DC (United States)
- OSTI ID:
- 111771
- Report Number(s):
- CONF-940225--Vol.1
- Country of Publication:
- United States
- Language:
- English
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