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09/22/2014

ASCEM: ESD Using HPC at Contaminated Sites

Sources: Haruko Wainwright, Stefan Finsterle, and Dan Hawkes

Cover-arqjune2014As part of the Advanced Simulation Capability for Environmental Management (ASCEM) project—DOE’s recent multi-laboratory effort to develop a state-of-the-art simulation platform for subsurface flow and reactive transport by joining environmental and computing sciences—ESD scientists have led the way in using advanced high-performance computing (HPC) for accurately predicting the long-term behavior of subsurface radioactive contaminant plumes. An article in the June 2014 issue of Actinide Research Quarterly (a journal published by Los Alamos National Laboratory) highlights the ASCEM work led by LBNL-ESD. The cover of the journal shows the prediction of uranium plume evolution in groundwater at the site—and notes that ASCEM marks the first attempt “to use high-performance computing uncertainty quantification to identify key controls at a contaminated site.”

ASCEM addresses soil and groundwater contamination issues that resulted from nuclear weapons production during the Cold War. The Savannah River Site (SRS) F-Area (Aiken, South Carolina) has been one of the primary application sites of ASCEM. Soil and groundwater in the F-Area are contaminated with a number of constituents, and the groundwater plume extends from the waste disposal basins to ~600 m downgradient, where it discharges to a stream. The most hazardous contaminants for potential exposure to receptors are uranium isotopes, strontium-90, iodine-129, technetium-99, tritium, and nitrate. Despite many years of active remediation, the groundwater still remains acidic, and the concentrations of U(VI) and other radionuclides are still significant.

Fig2
Results of two-dimensional Amanzi simulations of the pH (left column) and uranium concentration (right column) evolution over time at the SRS F-Area.

LBNL-ESD has contributed significantly to characterizing and predicting contaminant plume behavior at SRS—as demonstrated by three recently published journal articles. Under the Sustainable Systems Scientific Focus Area (SFA) project, former ESD scientist Doug Sassen et al. (2012) developed a new concept called “reactive facies” to capture the heterogeneity of hydrological and geochemical conditions in the subsurface. Another former ESD scientist Sergio Bea et al. (2013) developed a geochemical reaction network and transport model to describe the complex geochemical processes involved in uranium plume transport. Most recently, ESD’s Haruko Wainwright et al. (2014) developed a novel, noninvasive geophysical data integration method to map reactive facies in the subsurface over a large area. Work at SRS using ASCEM builds on these characterization and modeling efforts to develop an integrated reactive transport model for the F-Area, and to evaluate the effects of in situ remediation, as well as current and planned monitoring strategies. This effort will help DOE-EM provide efficient and cost-effective remediation and closure strategies.

In addition to the aforementioned Sassen, Bea, and Wainwright (who serves as ASCEM Site Application Thrust Deputy Manager), many other ESD scientists have made key contributions to the ASCEM effort. They include: Stefan Finsterle (ASCEM Platform and Integrated Toolsets Thrust Deputy Manager), Carl Steefel (ASCEM Multiprocess HPC Simulator Deputy Manager), ESD Director Susan Hubbard (ASCEM Senior Advisor), Nic Spycher, Boris Faybishenko, Jim Davis, Sergi Molins, Bhavna Arora, George Pau, and Jeff Johnson.

Ascem_portraits_all

To read the Actinide Research Quarterly article, go to: http://www.lanl.gov/arq/

To read more about ASCEM, go to: http://esd.lbl.gov/research/projects/ascem/

Citations:

Bea, S. A., H. Wainwright, N. Spycher, B. Faybishenko, S.S. Hubbard, and M.E. Denham (2013), Identifying key controls on the behavior of an acidic-U (VI) plume in the Savannah River Site using reactive transport modeling. Journal of Contaminant Hydrology, 151, 34–54; DOI: 10.1016/j.jconhyd.2013.04.005.

Sassen, D. S., S.S. Hubbard, S.A. Bea, J. Chen, N. Spycher, and M.E. Denham (2012). Reactive facies: An approach for parameterizing field‐scale reactive transport models using geophysical methods. Water Resources Research, 48, W10526; DOI:10.1029/2011WR011047.

Wainwright, H.M., J. Chen, D.S. Sassen, and S.S. Hubbard (2014). Bayesian hierarchical approach and geophysical data sets for estimation of reactive facies over plume scales. Water Resources Research, 50 (6), 4564–4584; DOI: 10.1002/2013WR013842.