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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.
Wei Ji, William R. Martin
Nuclear Science and Engineering | Volume 169 | Number 1 | September 2011 | Pages 19-39
Technical Paper | doi.org/10.13182/NSE10-73
Articles are hosted by Taylor and Francis Online.
In this paper the chord method is applied to the computation of Dancoff factors for doubly heterogeneous stochastic media, characteristic of prismatic and pebble bed designs of the Very High Temperature Gas-Cooled Reactor (VHTR), where TRISO fuel particles are randomly distributed in fuel compacts or fuel pebbles that are arranged in a full core configuration. Previous work has shown that a chord length probability distribution function (PDF) can be determined analytically or empirically and used to model VHTR lattices with excellent results. The key observation is that once the chord length PDF is known, Dancoff factors for doubly heterogeneous stochastic media can be expressed as closed-form expressions that can be evaluated analytically for infinite and finite media and semianalytically for a collection of finite media.Based on the assumption that the chord length PDF in the moderator region between two fuel kernels in a VHTR compact or pebble is exponential, which was shown to be an excellent approximation in previous work, closed-form expressions for Dancoff factors are derived for a range of configurations from infinite stochastic media to finite stochastic media, including multiple finite stochastic media in a background medium (e.g., a pebble bed core). Numerical comparisons with Monte Carlo benchmark results demonstrate that the closed-form expressions for the Dancoff factors for VHTR configurations are accurate over a range of packing fractions characteristic of prismatic and pebble bed VHTRs.