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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.
Luis Palomino, Mohamed S. El-Genk
Nuclear Technology | Volume 195 | Number 1 | July 2016 | Pages 1-14
Technical Paper | doi.org/10.13182/NT15-102
Articles are hosted by Taylor and Francis Online.
The Scalable LIquid Metal–cooled small Modular (SLIMM) reactor generates 10 to 100 MW(thermal) for extended periods without refueling. With the aid of an in-vessel chimney and a Na/Na helically coiled tubes heat exchanger (HEX) in the downcomer, natural circulation of in-vessel liquid sodium cools the SLIMM reactor core during nominal operation and after shutdown. With an unlikely malfunction of the Na/Na HEX, natural circulation of ambient air along the outer surface of the guard vessel wall maintains in-vessel natural circulation of liquid sodium and passively removes the decay heat after reactor shutdown. This paper performs three-dimensional computational fluid dynamics and thermal-hydraulic analyses to obtain preliminary estimates of the rate of decay heat removal by ambient air in case of a malfunction of the in-vessel Na/Na HEX and investigates the effect of using longitudinal metal fins along the guard vessel outer surface. The analyses calculate the contributions of natural convection and thermal radiation to the rate of decay heat removal by ambient air. For the same sodium temperatures in the reactor vessel downcomer as during steady-state nominal operation at 100 MW(thermal), the decay heat removal rate by ambient air without metal fins is ~1.0 MW(thermal), increasing by 26% to 1.26 MW(thermal) with metal fins. The contributions of natural convection and thermal radiation to the rate of decay heat removal are 58% and 42% without metal fins and 70% and 30% with metal fins, respectively. Extending the metal fins an additional 5 m and doubling the axial thermal conductivity increase the rate of the decay heat removal only slightly, to 1.28 MW(thermal).