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Glass strategy: Hanford’s enhanced waste glass program
The mission of the Department of Energy’s Office of River Protection (ORP) is to complete the safe cleanup of waste resulting from decades of nuclear weapons development. One of the most technologically challenging responsibilities is the safe disposition of approximately 56 million gallons of radioactive waste historically stored in 177 tanks at the Hanford Site in Washington state.
ORP has a clear incentive to reduce the overall mission duration and cost. One pathway is to develop and deploy innovative technical solutions that can advance baseline flow sheets toward higher efficiency operations while reducing identified risks without compromising safety. Vitrification is the baseline process that will convert both high-level and low-level radioactive waste at Hanford into a stable glass waste form for long-term storage and disposal.
Although vitrification is a mature technology, there are key areas where technology can further reduce operational risks, advance baseline processes to maximize waste throughput, and provide the underpinning to enhance operational flexibility; all steps in reducing mission duration and cost.
M. Hadj-Nacer, T. Manzo, M. T. Ho, I. Graur, M. Greiner
Nuclear Technology | Volume 194 | Number 3 | June 2016 | Pages 387-399
Technical Paper | doi.org/10.13182/NT15-82
Articles are hosted by Taylor and Francis Online.
A two-dimensional computational model of a loaded used nuclear fuel canister filled with dry helium gas was constructed to predict the cladding temperature during vacuum-drying conditions. The model includes distinct regions for the fuel pellets, cladding, and helium within each basket opening, and it calculates the conduction heat transfer within all solid components, heat generation within the fuel pellets, and conduction and surface-to-surface radiation across the gas-filled regions. First, steady-state simulations are performed to determine peak clad temperatures as a function of the fuel heat generation rate, assuming the canister is filled with atmospheric pressure helium. The allowable fuel heat generation rate, which brings the peak clad temperature to its limit, is evaluated. The discrete velocity method is then used to calculate slip-regime rarefied gas conduction across planar and cylindrical helium-filled gaps. These results are used to verify the Lin-Willis solid-gas interface thermal resistance model for a range of thermal accommodation coefficients α. The Lin-Willis model is then implemented at the solid-gas interfaces within the canister model. Finally, canister simulations with helium pressures of 100 and 400 Pa and α = 1, 0.4, and 0.2 are performed to determine how much hotter the fuel cladding is under vacuum-drying conditions compared to atmospheric pressure. For α = 0.4, the fuel heat generation rates that bring the clad temperature to its allowed limit for helium pressures of 400 and 100 Pa are reduced by 10% and 25%, respectively, compared to atmospheric pressure conditions. Transient simulations show that the cladding reaches its steady-state temperatures ~20 to 30 h after water is removed from the canister.