Virginia L. Legore

Dissolution Kinetics of Pyrochlore Ceramics for the Disposition of Plutonium.

Abstract Single-pass β ow-through (SPFT) experiments were conducted on a set of non-radioactive Ti-based ceramics at 90 °C and pH = 2 to 12. The specimens contained 27.9 to 35.8 wt%CeO2 as a surrogate for UO2 and PuO2. Compositions were formulated as TiO2-saturated pyrochlore (CeP1) and pyrochlorerich baseline (CePB1) ceramic waste forms. Pyrochlore + Hf-rutile and pyrochlore + perovskite + Hf-rutile constituted the major phases in the CeP1 and CePB1 ceramics, respectively. Results from dissolution experiments between pH = 2 to 12 indicate a shallow pH-dependence with an ill-defined minimum. Element release rates determined from experiments over a range of sample surface areas (S) and β ow rates (q) indicate that dissolution rates become independent of q/S values at 10.8 to 10.7 m/s. Dissolution rates dropped sharply at lower values of q/S, indicating rates that are subject to solution saturation effects as dissolved constituents become concentrated. Forward dissolution rates were 1.3(0.30) x 10-3 and 5.5(1.3) x 10-3 g/m2·d for CeP1 and CePB1 ceramics, respectively. Dissolution rates obtained in other laboratories compare well to the findings of this study, once the rate data are placed in the context of solution saturation state. These results make progress toward an evaluation of CeO2 as a surrogate for UO2 and PuO2 as well as establishing a baseline for comparison with radiation- damaged specimens.

Characterization of Vadose Zone Sediment: Borehole 299-E33-45 Near BX-102 in the B-BX-BY Waste Management Area

This report was revised in September 2008 to remove acid-extractable sodium data from Table 4.22. The data was removed due to potential contamination introduced during the acid extraction process. The remaining text is unchanged from the original report issued in 2002. The overall goal of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediments from within Waste Management Area B-BX-BY. This report is the first in a series of four reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from borehole 299-E33-45 installed northeast of tank BX-102.

Characterization of Vadose Zone Sediment: Borehole 41-09-39 in the S-SX Waste Management Area

This report was revised in September 2008 to remove acid-extractable sodium data from Table 5.15. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in February 2002. The overall goal of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediment from within the S-SX Waste Management Area. This report is one in a series of four reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from borehole 41-09-39 installed adjacent to tank SX-109.

Characterization of Vadose Zone Sediment: Slant Borehole SX-108 in the S-SX Waste Management Area

This report was revised in September 2008 to remove acid-extractable sodium data from Table 4.17. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in February 2002. The overall goal of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediment from within the S-SX Waste Management Area. This report is the fourth in a series of four reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from a slant borehole installed beneath tank SX-108 (or simply SX-108 slant borehole).

Characterization of Vadose Zone Sediment: RCRA Borehole 299-E33-338 Located Near the B-BX-BY Waste Management Area

This report was revised in September 2008 to remove acid-extractable sodium data from Table 4.8. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in June 2003. The overall goals of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., are: 1) to define risks from past and future single-shell tank farm activities, 2) to identify and evaluate the efficacy of interim measures, and 3) to aid via collection of geotechnical information and data, future decisions that must be made by the U.S. Department of Energy (DOE) regarding the near-term operations, future waste retrieval, and final closure activities for the single-shell tank waste management areas. For a more complete discussion of the goals of the Tank Farm Vadose Zone Project, see the overall work plan, Phase 1 RCRA Facility Investigation/Corrective Measures Study Work Plan for the Single-Shell Tank Waste Management Areas (DOE 1999). Specific details on the rationale for activities performed at the B-BX-BY tank farm waste management area are found in CH2M HILL (2000).

Characterization of Vadose Zone Sediments Below the TX Tank Farm: Boreholes C3830, C3831, C3832 and RCRA Borehole 299-W10-27

This report was revised in September 2008 to remove acid-extractable sodium data from Tables 4.8, 4.28,4.43, and 4.59. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in April 2004. The overall goal of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities at Hanford. To meet this goal, CH2M HILL Hanford Group, Inc. tasked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediments from within Waste Management Area (WMA) T-TX-TY. This report is the first of two reports written to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from boreholes C3830, C3831, and C3832 in the TX Tank Farm, and from borehole 299-W-10-27 installed northeast of the TY Tank Farm.

Radionuclide Incorporation in Secondary Crystalline Minerals from Chemical Weathering of Waste Glasses

Data from corrosion and radionuclide sequestration studies on two waste glasses indicated chemical weathering resulted in the formation of zeolite minerals such as herschelite and analcime. We also found that these minerals incorporated {approx}8 - 22%, {approx}1- 13% and {approx}8 - 25% of spiked 125-I, 99-Tc, and 75-Se respectively. Increasing concentrations of radionuclides in spike solution resulted in higher degree of sequestration as observed by significantly higher proportion of stable isotopes ({approx}70 - 95% I, {approx}58 - 100% Re, and {approx}100% Se) in secondary minerals. The radionuclide incorporation mechanisms for these minerals appear to be mainly isomorphic substitution of Se and Re in tetrahedral sites and iodide substitution for framework oxygen.

Characterization of Vadose Zone Sediment: Borehole 299-E33-46 Near B 110 in the B BX-BY Waste Management Area

This report was revised in September 2008 to remove acid-ectractable sodium data from Table 4.17. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in December 2002. The overall goal of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediment from within the B-BX-BY Waste Management Area. This report is the third in a series of three reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from a borehole installed approximately 4.5 m (15 ft) northeast of tank B- 110 (borehole 299-E33-46).

Characterization of Vadose Zone Sediment: Borehole C3103 Located in the 216-B-7A Crib Near the B Tank Farm

This report summarizes data collected from samples in borehole C3103. Borehole C3103 was completed to further characterize the nature and extent of vadose zone contaminants supplied by intentional liquid discharges into the crib 216-B7A/7B between 1954 and 1967. These cribs received dilute waste streams from the bismuth phosphate fuel reprocessing program in the 1950s and decontamination waste in the 1960s. Elevated concentrations of several constituents were primarily measured at different depth intervals. The primary radionuclides present in this borehole are cesium-137 and uranium near the top of the borehole. Chemical characteristics attributed to wastewater-soil interaction at different locations within this zone are elevated pH, sodium, fluoride, carbonate nitrate, and sulphate

The Status of Radiation Damage Experiments

Experiments have been on-going for about two years to determine the effects that radiation damage have on the physical and chemical properties of candidate titanate ceramics for the immobilization of plutonium. We summarize the results of these experiments in this document.