Rolf Sjöblom

Carolyn Pearce¹ David Peeler¹ Rolf Sjöblom/sup& Mark Triplett¹ Kirk Cantrell¹ Robert Moore¹ MichaelSchweiger¹ Vicky Freedman¹ Matthew Fountain¹ Sue Clark¹ Albert Kruger³

1, Pacific Northwest National Laboratory, Richland, Washington, United States2, Luleå University of Technology, Luleå, , Sweden3, U.S. Department of Energy—Office of River Protection, Richland, Washington,United States

The Department of Energy’s Environmental Management cleanup effort is focusedon developing and implementing innovative and high impact technologies andsolutions that positively impact the overall mission lifecycle by: (1) reducing lifecyclecosts; (2) accelerating lifecycle schedules; (3) mitigating mission uncertainties,vulnerabilities, and risks; and (4) minimizing the mortgage associated with longterm,post-closure and post-completion stewardship. Pacific Northwest NationalLaboratory and its partnering institutions, are focused on reducing risk anduncertainty across the integrated flowsheet which includes safe waste storage,retrieval, pretreatment, immobilization, disposal, and tank closure. In thispresentation, an overview of the major Hanford flowsheet unit operations will beprovided and examples of specific projects focused on reducing risks anduncertainties will be explored.For example, a key issue of Hanford tank waste processing and disposal is that,although radionuclides (e.g., technetium) drive the disposal risk for the low-activityflowsheet, the presence of ‘benign’ elements (e.g., aluminum) dictate processinglimits or rates in both retrieval and pretreatment unit operations and have otherpotential downstream negative impacts. Thus, safe, cost-effective, and efficient wasteprocessing depends on a fundamental understanding of aluminum chemistry in highionic strength, highly alkaline solutions where water activity is low. Once the wastehas been retrieved, proces>sed, and immobilized, controlling the behavior of riskdriving elements (e.g., Tc and/or I for low-activity waste) in the waste form and theenvironment becomes essential for waste form disposal or tank closure.With respect to low-activity waste form disposal, material solutions mustdemonstrate that the risk driving radioactive elements will be contained in a mannerwholly consistent with statutory requirements. Modelling future performanceremains a challenge for performance assessment (PA) formalism. An appealingoption is to perform an inverse PA (IPA) and look far into the past. Archeologicalartifacts, analogous to wasteform materials (i.e. glass and concrete) that have beenleft by our ancestors and exposed to the environment for thousands of years can beused to check for comprehensiveness as well as to validate and refine predictedwasteform durability. An IPA describes the features, events and processes that haveinfluenced the corrosion of a material over time and can help establish the mostlikely scenarios that should be included in PA for the future. An IPA for ancient glassfrom a hillfort at Broborg, Sweden (ca. 400-575 AD), used to fortify the fort wallswill also be one of the key focal points of this presentation.2