Low-Level Waste buried on the SRS contains cellulosic materials, Including wood, paper, and cardboard. Once buried, these materials are expected to degrade to form cellulose degradation products (CDP). Such materials are expected to influence radionuclide speciation in such a way that the radionuclides will sorb less to SRS Subsurface sediments and therefore would migrate more rapidly from the disposal site. The objective of this study was to quantify through laboratory work the influence of CDP and pH on radionuclide sorption to SRS subsurface sediments. The intent of this work was to create a Kd look-up table as a function of radionuclide, pH, and CDP concentration that could be used in future performance assessment calculations. Previous CDP-impacted Kd values were generated using two chemical analogues, UO2 2+ and Eu3+. This study collected data from a wider range of analogues to validate and/or refine this approach. An incomplete-randomized-block-statistical design was used in a laboratory sorption study involving 2 soil types (sandy and clay textured), 5 dissolved organic carbon concentrations (a measure of CDP), and 3 pH levels. Nonradioactive solutes were used as chemical analogues to the radionuclides of interest to the Low-Level Waste Performance Assessment: monovalent cations (K+ and Cs+), divalent cations (Ni2+ and Sr2+), trivalent cations (Ce3+ and Eu3+), tetravalent cations (Th4+ and Zr4+), and an anion (ReO4-). Analogues were matched to approximately 30 radionuclides based on similarities in periodicity and chemical properties. All CDP-impacted Kd values generated from this study were equal to or greater than those used in previous performance assessments. These larger Kd values may result in a greater Waste Acceptance Criteria (WAC), which in turn may permit greater amounts of Low-Level Waste to be safely disposed on site, saving the site the expense of shipping the waste off-site for disposal.
