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DNFSB spots possible bottleneck in Hanford’s waste vitrification
Workers change out spent 27,000-pound TSCR filter columns and place them on a nearby storage pad during a planned outage in 2023. (Photo: DOE)
While the Department of Energy recently celebrated the beginning of hot commissioning of the Hanford Site’s Waste Treatment and Immobilization Plant (WTP), which has begun immobilizing the site’s radioactive tank waste in glass through vitrification, the Defense Nuclear Facilities Safety Board has reported a possible bottleneck in waste processing. According to the DNFSB, unless current systems run efficiently, the issue could result in the interruption of operations at the WTP’s Low-Activity Waste Facility, where waste vitrification takes place.
During operations, the LAW Facility will process an average of 5,300 gallons of tank waste per day, according to Bechtel, the contractor leading design, construction, and commissioning of the WTP. That waste is piped to the facility after being treated by Hanford’s Tanks Side Cesium Removal (TSCR) system, which filters undissolved solid material and removes cesium from liquid waste.
According to a November 7 activity report by the DNFSB, the TSCR system may not be able to produce waste feed fast enough to keep up with the LAW Facility’s vitrification rate.
Bin Zhang, Liang Zhang, Cong Liu, Yixue Chen
Nuclear Science and Engineering | Volume 189 | Number 2 | February 2018 | Pages 120-134
Technical Paper | doi.org/10.1080/00295639.2017.1394085
Articles are hosted by Taylor and Francis Online.
Angular discretization errors inherent in the discrete ordinates method are a major problem, especially for localized source problems and problems with strongly absorbing media or large-volume void regions, where angular discretization errors would be totally unacceptable. This paper proposes a regional angular adaptive algorithm together with a goal-oriented error estimate to solve the SN equations. Standard angular adaptive refinement techniques are based on estimated local errors. We compare an interpolated angular flux value against a calculated value to generate local errors. The adaptive quadrature sets can be created by subdividing a spherical quadrilateral into four spherical subquadrilaterals that have positive weights and can be locally refined. Techniques for mapping angular fluxes from one quadrature set to another are developed to transfer angular fluxes on the interfaces of different spatial regions. To provide a better detector response, local errors are weighted by the importance of a given angular region toward the computational goal, providing an appropriate goal-oriented angular adaptivity. First collision source methods are employed to improve adjoint flux calculation accuracy. We tested the performance and accuracy of the proposed goal-oriented regional angular adaptive algorithm within the ARES code for a number of benchmark problems and present the results of a one-region test model and the Kobayashi benchmark problems. The reduction of angular number is at least one order of magnitude for adaptive refinement. The benchmarks demonstrate that the proposed goal-oriented adaptive refinement can achieve the same level of accuracy as the SN method, which has significantly higher computation cost. Thus, adaptive refinement is a viable approach for investigating difficult particle radiation transport problems.
