Hydrothermal reaction of simulated waste forms with basalt under conditions expected in a nuclear waste repository in basalt

Technical Report · Thu Mar 01 04:00:00 EST 1984

OSTI ID:6386041

Myers, J; Apted, M J; Mazer, J J

Simulated spent fuel, simulated defense high-level waste, and simulated and /sup 99/Tc-doped commercial high-level waste (PNL 76-68) were reacted with groundwater, both in the presence and absence of basalt, simulating expected conditions for a nuclear waste repository located in basalt in gold bag sampling autoclaves at temperatures between 90/sup 0/ and 300/sup 0/C, at 30 MPa pressure. During the course of the experiments, samples of the fluid phase were periodically withdrawn from the autoclaves and were analyzed for pH as well as major, minor, and trace cations and anions. At 200 and 300/sup 0/C, all dissolved species displayed either steady-state concentrations or decreasing concentrations after the first 1000 h. At 100/sup 0/C, some dissolved components had not reached steady-state concentrations after 6000 h. Solids characterization suggests that the formation of secondary alteration phases such as alkali feldspar, smectite clays, scapolite, and a variety of uranium-bearing silicate phases, imposes solubility limits on the release of many analog elements of potential radionuclides. These steady-state (or solubility) concentration limits can be coupled with measured hydrologic flow rates to calculate radionuclide release rates from the waste form for a nuclear waste repository in basalt. The experimentally determined steady-state concentrations of analog elements are compared to calculated solubilities for individual elements. In many cases, the experimentally determined concentrations are several orders of magnitude higher than the calculated solubility concentrations. Possible reasons for these discrepancies include invalid assumptions on stable alteration solids, temperature differences, and kinetic effects. The steady-state concentrations reported in this document provide realistic and defensibly conservative data that can be used on a preliminary basis for evaluating waste form performance both alone and in the presence of basalt.

• Research Organization: Rockwell International Corp., Richland, WA (USA). Rockwell Hanford Operations
• DOE Contract Number: AC06-77RL01030
• OSTI ID: 6386041
• Report Number(s): RHO-BW-ST-59-P; ON: DE85007091
• Country of Publication: United States
• Language: English

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54 ENVIRONMENTAL SCIENCES
BASALT
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BOROSILICATE GLASS
DATA
DISSOLUTION
EXPERIMENTAL DATA
FUEL ELEMENTS
GLASS
GROUND WATER
HIGH-LEVEL RADIOACTIVE WASTES
HOURS LIVING RADIOISOTOPES
HYDROGEN COMPOUNDS
HYDROTHERMAL ALTERATION
IGNEOUS ROCKS
INFORMATION
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LEACHING
MATERIALS
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
OXYGEN COMPOUNDS
PERFORMANCE
RADIOACTIVE MATERIALS
RADIOACTIVE WASTES
RADIOISOTOPES
REACTOR COMPONENTS
ROCK-FLUID INTERACTIONS
ROCKS
SEPARATION PROCESSES
SPENT FUEL ELEMENTS
TECHNETIUM 99
TECHNETIUM ISOTOPES
TEMPERATURE EFFECTS
VOLCANIC ROCKS
WASTE FORMS
WASTES
WATER
YEARS LIVING RADIOISOTOPES