Solubility and speciation studies of waste radionuclides pertinent to geologic disposal at Yucca Mountain: Results on neptunium, plutonium and americium in J-13 groundwater; Letter report (R707): Reporting period, October 1, 1985--September 30, 1987
as w < u siP ]| s & iHitSi Mil 6 Mil r' Br 3 = §55 a "3 Page 2 of 70 I. SUMMARY AND RECOMMENDATIONS We summarize in this letter report solubility studies for the Nevada Nuclear Waste Storage Investigations (NNWSI) project at the Lawrence Berkeley Laboratory (LBL) for the fiscal years 1986 and 1987. The research effort was started October 1, 1985, and is planned to continue at least through FY 1992. It covers the following topics: 1. Summary and Recommendations; 2. Objectives; 3. Concept of
... 3. Concept of Solubility Studies; 4. Design and Fabrication of Equipment; 5. Study of me Solubility and Speciation of Neptunium, Plutonium and Americium in J-13 Groundwater of Varying pH Values and Temperatures of 60° and 90°C; 6. Work in Progress; 7. Reports/Publications/Presentations; 8. Quality Assurance. Summary We have studied the solubilities of neptunium, plutonium, and americium in J-13 groundwater from Yucca mountain (Nevada) at three temperatures and hydrogen ion concentrations. They are 25°, 60°C, and 90°C and pH 5.9, 7.0, and 8.5. Tables I, II, and III summarize the results for neptunium, plutonium, and americium, respectively. The results for 25°C are from a study which we did during FY 1984. We included these previous results in the tables to give more information on the solubility tempera ture dependance; they were, however, done at only one pH (7.0). The solubilities were studied from oversaturation. The nuclides were added at the beginning of each NNWSI-LBL-R707, Rl Page 3 of 70 Table I. Summary of results for solubility experiments on neptunium in J-13 groundwater at pH 5.9, 7.0, and 8.5, and at 25°, 60°, and 90°C. 25°C Steady-state concentration (M) 60°C 90°C 25 C C Oxidation state in supernatant solution 60°C 90°C pH5.9 NA (6.4 + 0.3) x 10~3 (1.2 ± 0.