Evaporative Evolution of a Na-Cl-NO3-K-Ca-SO4-Mg-Si Brine at 95(degree)C: Experiments and Modeling relevant to Yucca Mountain, Nevada, USA

Journal Article · Tue Aug 24 00:00:00 EDT 2004 · Geochemical Transactions, vol. 6, no. 2, June 7, 2005, pp. 31-45

OSTI ID:902304

Alai, M; Sutton, M; Carroll, S A

A synthetic Topopah Spring Tuff water representative of one type of pore water at Yucca Mountain, Nevada (USA) was evaporated at 95 C in a series of experiments to determine the geochemical controls for brines that may form on, and possibly impact upon the long-term integrity of waste containers and drip shields at the designated high-level, nuclear-waste repository. Solution chemistry, condensed vapor chemistry, and precipitate mineralogy were used to identify important chemical divides and to validate geochemical calculations of evaporating water chemistry using a high temperature Pitzer thermodynamic database. The water evolved towards a complex ''sulfate type'' brine that contained about 45 mol% Na, 40 mol% Cl, 9 mol% NO{sub 3}, 5 mol% K, and less than 1 mol% each of SO{sub 4}, Ca, Mg, {Sigma}CO{sub 2}(aq), F, and Si. All measured ions in the condensed vapor phase were below detection limits. The mineral precipitates identified were halite, anhydrite, bassanite, niter and nitratine. Trends in the solution composition and identification of CaSO{sub 4} solids suggest that fluorite, carbonate, sulfate, and magnesium-silicate precipitation control the aqueous solution composition of sulfate type waters by removing fluoride, calcium, and magnesium during the early stages of evaporation. In most cases, the high temperature Pitzer database, used by EQ3/6 geochemical code, sufficiently predicts water composition and mineral precipitation during evaporation. Predicted solution compositions are generally within a factor of two of the experimental values. The model predicts that sepiolite, bassanite, amorphous silica, calcite, halite and brucite are the solubility controlling mineral phases.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 902304
• Report Number(s): UCRL-JRNL-206367; TRN: US0702827
• Journal Information: Geochemical Transactions, vol. 6, no. 2, June 7, 2005, pp. 31-45, Vol. 6, Issue 2
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
25 ENERGY STORAGE
36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
12 MANAGEMENT OF RADIOACTIVE WASTES AND NON-RACIOACTIVE WASTER FROM NUCLEAR FACILITIES
54 ENVIRONMENTAL SCIENCES
ANHYDRITE
AQUEOUS SOLUTIONS
BRINES
CALCITE
CALCIUM
CHEMISTRY
CONTAINERS
FLUORITE
HALITE
MAGNESIUM
MINERALOGY
SEPIOLITE
SILICA
SOLUBILITY
SULFATES
THERMODYNAMICS
WASTES
WATER CHEMISTRY
YUCCA MOUNTAIN