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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.
Joachim Poppei, Gerhard Mayer, Nicolas Hubschwerlen, Guillaume Pépin, Jacques Wendling
Nuclear Technology | Volume 174 | Number 3 | June 2011 | Pages 317-326
Technical Note | TOUGH2 Symposium / Thermal Hydraulics | doi.org/10.13182/NT11-A11742
Articles are hosted by Taylor and Francis Online.
The calculation of relative humidity in tunnels is a fundamental task when designing a repository ventilation system in a clay host rock. It requires complex numerical modeling of transient (forced) convective and conductive heat and fluid transport. The humidity of the tunnel air primarily depends (along with the meteorological conditions at the entrance) upon the thermal-hygric transitional conditions at the exposed rock surface of the tunnel walls. Some portions receive water influx while others receive heat influx from the waste already emplaced in other parts of the host rock.The coupling between the transport processes in the host rock and the transfer processes along the tunnel wall are treated in a simplified manner. The processes described by coefficients for heat (Nusselt number) and vapor (Sherwood number) both depend on the ventilation velocity (Reynolds number). We discuss an approach involving supportive TOUGH2 computations for complex transport problems in the host rock. The results are processed and applied to the transient analysis of temperature and humidity changes in the ventilation air.Analysis of the evaporation along a tunnel wall is supported by a one-dimensional radially symmetric EOS9 model. Results from the TOUGH2 computations with different Sherwood numbers are parameterized accordingly. The prevailing humidity along the tunnel wall is then determined with an iterative approach, whereby the humidity is controlled by either the ventilation (i.e., through the Sherwood number) or the leakage capacity of the host rock. Finally, the humidity changes in the ventilation air are derived from the computed diffusion of vapor along the boundary layer.To calculate the heat transfer into the tunnel along its walls, we used the results from a complex geometric TOUGH2 model. The model considers different thermophysical parameters as well as the transient rates of heat production by the waste. At any given time, the heat transfer along the tunnel wall - with consideration of the then-prevailing heat production and ventilation velocity - causes a rise in air temperature and a corresponding decrease in relative humidity.