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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.
Jianan Lu, Jiong Guo, Tomasz Kozlowski, Fu Li
Nuclear Science and Engineering | Volume 193 | Number 1 | January-February 2019 | Pages 131-146
Technical Paper – Selected papers from NURETH 2017 | doi.org/10.1080/00295639.2018.1504545
Articles are hosted by Taylor and Francis Online.
The High-Temperature Gas-Cooled Reactor–Pebble Bed Module (HTR-PM) is a large-scale complex system that includes reactor core, steam generator, helium circulator, and other important components. When integrating these components, coupling problems such as multiphysics problem, multicircuit problem, multiscale problem, and multimodule problem arise in the numerical simulation. The HTR-PM multicircuit system comprises the primary circuit and secondary circuit, which are simulated by two independent codes and coupled by the interface in the once-through steam generator. Although time-consuming, Picard iteration is a feasible and convenient coupling method to integrate two components because oversolving in the early stages of the iteration causes strong fluctuation between circuits. To address this problem, optimization of the maximum subiteration number and convergence precision have been implemented to improve the efficiency and numerical stability of the Picard iteration. The Dynamic Residual Balance method, an improved version of the Residual Balance method, is proposed to prevent oversolving inside the subiterations. It takes into consideration fluctuation between circuits, and this method is robust in a wide range of cases. Moreover, the nonlinear preconditioned Jacobian-Free Newton-Krylov method, which has less fluctuation between circuits than Picard iteration, is a coupling scheme that updates all the solution variables from the primary circuit and the secondary circuit simultaneously. Outstanding convergence and efficiency can be obtained by implementing the proper preconditioner in this HTR-PM multicircuit problem. The downside is that it requires significant modification to the legacy codes.