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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.
Benoît Dessirier, Jerker Jarsjö, Andrew Frampton
Nuclear Technology | Volume 187 | Number 2 | August 2014 | Pages 147-157
Technical Paper | Radioactive Waste Management and Disposal | doi.org/10.13182/NT13-77
Articles are hosted by Taylor and Francis Online.
Deep geological repositories are generally considered as suitable environments for final disposal of spent nuclear fuel. In the Swedish and Finnish repository design concept, canisters are to be placed in deep underground tunnels in sparsely fractured crystalline bedrock, in deposition holes in which each canister is embedded with an expansive bentonite-clay-mixture buffer. A set of semigeneric two-dimensional radially symmetric TOUGH2 simulations are conducted to investigate the multiphase dynamics and interactions between water and air in a bentonite-rock environment. The main objective is to identify how sensitive saturation times of bentonite are to the geometry of the rock fractures and to commonly adopted simplifications in the unsaturated flow description such as Richards assumptions. Results show that the location of the intersection between the fracture system and the deposition hole is a key factor affecting saturation times. A potential long-lasting desaturation of the rock matrix close to the bentonite-rock interface is also identified extending up to 10 cm inside the rock. Two-phase-flow models predict systematically longer saturation times compared to a simplified Richards approximation, which is frequently used to represent unsaturated flows. The discrepancy diverges considerably as full saturation is approached.