Thermal, chemical, and mass-transport processes induced in abyssal sediments by the emplacement of nuclear waste: experimental and modeling results
This paper discusses heat and mass transport studies of marine red clay sediments being considered as a nuclear waste isolation medium. Numerical models indicate that for a maximum allowable sediment/canister interface temperature of 200 to 250/sup 0/C, the sediment can absorb about 1.5 kW initial power from waste in a 3 m long by 0.3 m dia canister buried 30 m in the sediment. Fluid displacement due to convection is found to be less than 1 m. Laboratory studies of the geochemical effects induced by heating sediment/seawater mixtures indicate that the canister and waste form must be designed to resist a hot, acid (pH 3 to 4) oxidizing environment. Since the thermally altered sediment volume of about 5.5 m/sup 3/ is small relative to the sediment volume overlying the canister, the acid and oxidizing conditions are not anticipated to effect the properties of the far field. Using sorption coefficient correlations, the migration of four nuclides /sup 239/Pu, /sup 137/Cs, /sup 129/I, and /sup 99/Tc were computer for a canister buried 30 m deep in a 60 m thick red clay sediment layer. It was found that the /sup 239/Pu and /sup 137/Cs are essentially completely contained in the sediments, while /sup 129/I and /sup 99/Tc broke through the 30 m of sediment in about 5000 years. The resultant peak injection rates of 4.6 x 10/sup -5/ ..mu..Ci/year-m/sup 2/ for /sup 129/I and 1.6 x 10/sup -2/ ..mu..Ci/year-m/sup 2/ for /sup 99/Tc were less than the natural radioactive flux of /sup 226/Ra (3.5 to 8.8 x 10/sup -4/ ..mu..Ci/year-m/sup 2/) and /sup 222/Rn (0.26 to 0.88 ..mu..Ci/year-m/sup 2/).
- Research Organization:
- Sandia Labs., Albuquerque, NM (USA); Minnesota Univ., Minneapolis (USA). Dept. of Geology
- DOE Contract Number:
- EY-76-C-04-0789
- OSTI ID:
- 5399047
- Report Number(s):
- SAND-79-2244C; CONF-800420-3; TRN: 80-007848
- Resource Relation:
- Conference: 2. international ocean disposal symposium, Woods Hole, MA, USA, 15 Apr 1980
- Country of Publication:
- United States
- Language:
- English
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SEA BED
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SEDIMENTS
TECHNETIUM 99
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ALKALI METAL ISOTOPES
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052002* - Nuclear Fuels- Waste Disposal & Storage