Multi-Barrier Borehole Canister Designs for a Tuff Repository
Initial dimensions are presented for proposed multi-barrier spent fuel borehole canisters using coated shells combined with sacrificial anodes and alkaline, oxide barriers to adjust potential and pH of the exterior shell into thermodynamically passive or immune regions of the Pourbaix diagram. Configuration of the 3 PWR canister is similar to the 1983 Site Characterization Project (SCP) borehole design. Canister dimensions were determined by using material performance data to calculate wall thickness, criticality, and sacrificial anode life. For the 3-PWR canister. Incoloy 825 is the preferred exterior canister shell material; copper-nickel alloy CDA 715 is the preferred interior canister shell material. High-lime concrete or alumina is preferred for the alkaline filler. Magnesium alloy is the preferred sacrificial anode material. Coating the canister exterior would be necessary to reduce corrosion current density to the point where a 10,000 year design life is possible. A 1 PWR canister has lower mass, thinner walls and lower criticality than the 3 PWR design. Equilibrium calculations for the historical average composition of J-13 water using the aquatic chemical speciation program WQ4F show positive saturation indices for several minerals, indicating potential for deposition on the canister exterior over long time periods. Uniform deposition could reduce corrosion rate by hindering transport of corrosion products from the canister surface. If deposition is non-uniform, local corrosion could increase through development of differential oxygen concentration cells.
Civil and Environmental Engineering | Civil Engineering | Other Civil and Environmental Engineering
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James, D. E.,
Skaggs, R. L.,
Multi-Barrier Borehole Canister Designs for a Tuff Repository.
High level radioactive waste management : Proceedings of the Fifth Annual International Conference