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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.
Blair P. Bromley
Nuclear Technology | Volume 194 | Number 2 | May 2016 | Pages 192-203
Technical Paper | doi.org/10.13182/NT14-101
Articles are hosted by Taylor and Francis Online.
Pressure-tube heavy water reactors (PT-HWRs) are highly advantageous for implementing plutonium-thorium (Pu-Th) fuels because of their high neutron economy and online refueling capability. The use of annular heterogeneous seed-blanket core concepts in a PT-HWR where higher-fissile-content seed fuel bundles are physically separate from lower-fissile-content blanket bundles allows more flexibility and control in fuel management. The lattice concept modeled was a 35-element bundle made with a homogeneous mixture of reactor-grade PuO2 (67 wt% fissile) and ThO2, with a central zirconia rod to reduce coolant void reactivity. Eight annular heterogeneous seed-blanket core concepts with plutonium-thorium–based fuels in a 700-MW(electric)–class PT HWR were analyzed, using a once-through-thorium cycle. Blanket region(s) represented 50% to 75% of the total fuel volume. There were 1, 2, and 3 different blanket regions and 1, 2, and 3 different seed regions. The seed fuel tested was 3 wt% or 4 wt% PuO2, while the blanket fuel tested was 1 wt% PuO2, mixed with ThO2. The impact of different fuel combinations on the core-average burnup, fissile utilization (FU), power distributions, and other performance parameters were evaluated. WIMS-AECL 3.1 was used to perform lattice physics calculations using two-dimensional, 89-group integral neutron transport theory, while RFSP 3.5.1 was used to perform the core physics and fuel management calculations using three-dimensional two-group diffusion theory. Among the different core concepts investigated, there were cores where the FU was up to 25% higher than is achieved in a PT-HWR using natural uranium fuel bundles. There were cores where up to 60% of the Pu was consumed, cores where up to 41% of the energy was produced from 233U, and cores where up to 236 kg/yr of fissile uranium (mainly 233U) was produced in the discharged fuel. This study is an extension of previous work that involved the analysis of homogeneous cores, two-region (one seed, one blanket) and eight-region (four seeds, four blankets) annular, and checkerboard-type heterogeneous seed-blanket cores.