No abstract

v BFS likely remained and worked as a reductant for 30 days reaction time so that the redox condition was not 100% oxidized. 99 Tc solubility test results showed that the aqueous 99 Tc concentration of each sample of crushed LSW grout decreased with increasing reaction times for all samples. After 51 days reaction time under reducing conditions, the aqueous 99 Tc concentrations in all samples converged to average values of 0.34 µg/L (or 3.4 × 10 -9 M), 0.43 µg/L (or 4.3 × 10 -9 M), and 0.51 µg/L (or 5.1 × 10 -9 M) at similar pH (~12.5) for the LSW grouts T19, T20, and T21, respectively. These final effluent 99 Tc concentrations suggest that a single-value empirical solubility of ~4.3±3.8 × 10 -9 M (or 0.42±0.37 µg/L) based on 51 days of testing at 12.5 pH and -400 mV E h conditions can be used for 99 Tc release in the reducing nearfield IDF conditions and that a 99 Tc(IV)-bearing solid phase is controlling 99 Tc release from LSW grouts. Additional testing beyond 51 days reaction time should be conducted to confirm steady-state conditions and provide additional data to support the 99 Tc solubility value under reducing conditions.Based on the results, the new LSW grout formulations using HL, even without adding 99 Tc getters or Xypex are good enough to limit 99 Tc diffusivity to below 10 -12 cm 2 /s. The new formulation using HL instead of FA should replace the Cast Stone formulation for sulfate-rich LSW streams. The results obtained in this task can help fill existing data gaps, support final selection of a LSWG waste form, and improve the technical defensibility of long-term waste form performance estimates for the upcoming IDF performance assessment. vii S siemens wt% weight percent µ micro (prefix, 10 -6

No abstract

Contaminants disposed of at the land surface must migrate through the vadose zone before entering groundwater. Processes that occur in the vadose zone can attenuate contaminant concentrations during transport through the vadose zone. Thus, quantifying contaminant attenuation and contaminant transport processes in the vadose zone, in support of the conceptual site model (CSM) and fate and transport assessments, is important for assessing the need for, and type of, remediation in the vadose zone and groundwater. The framework to characterize attenuation and transport processes provided in U.S. Environmental Protection Agency (EPA) guidance documents was used to guide the laboratory effort reported herein.PNNL-26208 RPT-DVZ-AFRI-037 v all samples. In terms of desorption versus adsorption K d values, there was no clear trend across all of the samples.

No abstract