scholarly journals Methods of Simulating Low Redox Potential (Eh) for a Basalt Repository

1983 ◽  
Vol 26 ◽  
Author(s):  
Carol M. Jantzen
Keyword(s):  
Redox Potential ◽  
Nuclear Waste ◽  
Deionized Water ◽  
Waste Form ◽  
Laboratory Simulation ◽  
Redox Potentials ◽  
Waste Package ◽  
Leach Rate ◽  
Ph Conditions ◽  
Selection Of

ABSTRACTIn the selection of a repository for burying vitrified nuclear waste, the leach rate of the waste form in groundwater is of concern. Basaltic groundwaters have inherently low redox potentials which may affect the waste form leach rate. Laboratory simulation of the Eh-pH conditions to be found in a basalt repository can be achieved when crushed basalt is added to deoxygenated deionized water. The effects of other redoxactive waste package components, such as iron, were found to stabilize solution redox potential at different valves under oxic and anoxic conditions. When iron was present, different waste form leach rates were observed with and without oxygen.

Materials Interactions Relating to Long-Term Geologic Disposal of Nuclear Waste Glass

1986 ◽  
Vol 84 ◽  
Author(s):  
Ned E. Bibler ◽  
Carol M. Jantzen
Keyword(s):  
Nuclear Waste ◽  
Review Paper ◽  
Waste Glass ◽  
Waste Form ◽  
Glass Waste ◽  
Waste Package ◽  
Geologic Disposal ◽  
Nuclear Waste Glass ◽  
Backfill Materials

AbstractIn the geologic disposal of nuclear waste glass, the glass will eventually interact with groundwater in the repository system. Interactions can also occur between the glass and other waste package materials that are present. These include the steel canister that holds the glass, the metal overpack over the canister, backfill materials that may be used, and the repository host rock. This review paper systematizes the additional interactions that materials in the waste package will impose on the borosilicate glass waste form-groundwater interactions. The repository geologies reviewed are tuff, salt, basalt, and granite. The interactions emphasized are those appropriate to conditions expected after repository closure, e.g. oxic vs. anoxic conditions. Whenever possible, the effect of radiation from the waste form on the interactions is examined. The interactions are evaluated based on their effect on the release and speciation of various elements including radionuclides from the glass. It is noted when further tests of repository interactions are needed before long-term predictions can be made.

Investigation of Pu-Doped Ceramics Using Modified MCC-1 Leach Test

2002 ◽  
Vol 713 ◽  
Author(s):  
Elena V. Nikolaeva ◽  
Boris E. Burakov
Keyword(s):  
Chemical Resistance ◽  
Leach Solution ◽  
Deionized Water ◽  
Zirconia Ceramic ◽  
Leach Rate ◽  
Leach Test ◽  
Similar Chemical ◽  
Leaching Solution ◽  
Weapons Grade Plutonium ◽  
Selection Of

ABSTRACTLeach testing is an important tool for the investigation of chemical durability of radioactive waste forms. The data obtained from these tests allows for the selection of the most durable ceramics for the immobilization of weapons-grade plutonium. Ceramics based on cubic zirconia, (Zr,Gd,Pu)O2, doped with 10 wt.% 239Pu, zircon, (Zr,Pu)SiO4, doped with separately 5-6 and 10 wt.% 239Pu, pyrochlore, (Ca,Pu,Gd,Hf,U)2Ti2O7, doped with 10 wt.% 239Pu were studied using MCC-1 leach test. Ceramic samples were placed in test vessels with deionized water and set temperatures of 25°C and 90°C in an oven for 28 days. The leaching solution was removed and replaced with fresh deionized water after 3 and 14 days from the start of the test. Only data obtained after 14 and 28 days were used for the interpretation. No saturation of leach solution with Pu was observed in any experiments. It was found that the (without correction for porosity) normalized Pu mass loss (in g/m2 ) after 14 and 28 days was:- for the zirconia ceramic – 2 × 10−2 to 4 × 10−2 at 90°C and 8 × 10−3 to 9 × 10−3 at 25 °C;- for zircon doped with 5-6 wt.% of Pu – 7.0 × 10−3 to 8.2 × 10−3 at 90°C and 1.0 × 10−3 to 1.2 × 10−3 at 25 °C;- for zircon doped with 10 wt.% of Pu – 0.2 to 0.2 at 90°C and 3.0 × 10−2 to 4.0 × 10−2 at 25 °C;- for pyrochlore – 1.0 × 10−3 to 1.0 × 10−3 at 90°C and 2.0 × 10−3 to 3.0 × 10−3 at 25 °C.It was shown that the high leach rate for zircon based ceramic doped with 10 wt.% Pu was caused by the presence of the separated inclusions of PuO2 phases observed in ceramic matrix. The results obtained so far allow us to conclude that ceramics based on zircon, zirconia and pyrochlore are characterized by similar chemical resistance to leaching in deionized water. Based on its low porosity, zircon may be most durable ceramic host phase for Pu.

Solubility Constraint: An Important Consideration in Safety Assessment of Nuclear Waste Disposal

1983 ◽  
Vol 26 ◽  
Author(s):  
Dhanpat Rai ◽  
Jack L. Ryan
Keyword(s):  
Nuclear Waste ◽  
Safety Assessment ◽  
Additional Data ◽  
Solid Phase ◽  
Waste Form ◽  
Waste Package ◽  
Reducing Conditions ◽  
Solid Compounds ◽  
Adsorption Desorption ◽  
Hydrologic Transport

ABSTRACTSolubilities of key solid compounds that are either present in the waste form or can readily precipitate from waste package leachates under repository conditions can be used to set maximum limits on radionuclide concentrations expected in groundwater. This is because the solubility limited concentrations are independent of the release scenarios, hydrologic transport characteristics, and adsorption/desorption reactions. Some of the important factors that control solubilities are pH, pe, type of solid phase, and nature of complexing ligands in the ground waters. Most of the above factors are affected by radiolysis due to the inherent radiation field of the waste form. Experimental results pertaining to the solubilities of selected Am, U, Np, and Pu compounds and the effects of radiolysis are discussed. These results show that: 1) at expected repository pH and reducing conditions, solubility controlled concentrations of several actinides are low and near acceptable limits, 2) the redox conditions at the waste form-water interface may be very oxidizing due to radiolyticeffects, despite the fact that normal repository conditions are assumed to be reducing, 3) additional data on solubility limits and key thermodynamic parameters are needed.

Experimental Interaction of Basalt, Bentonite, and Water: Implications for Groundwater Chemistry in Waste Package Packing Material in a Nuclear Waste Repository

1987 ◽  
Vol 112 ◽  
Author(s):  
Gail L. McKeon ◽  
E. C. Thornton ◽  
D. J. Halko ◽  
M. I. Wood
Keyword(s):  
Nuclear Waste ◽  
Near Field ◽  
Sodium Concentration ◽  
Packing Material ◽  
Deionized Water ◽  
Solution Chemistry ◽  
Nuclear Waste Repository ◽  
Waste Package ◽  
Waste Repository ◽  
C 30

AbstractExperiments have been conducted by the Basalt Waste Isolation Project (BWIP) to assess changes in solution chemistry in the near-field environment of a nuclear waste repository in basalt. These Dickson autoclave experiments were carried out using Grande Ronde basalt ± bentonite and synthetic groundwater or deionized water at 300°C, 30 MPa, and solution-to-solid mass ratio of 10 for up to two years. Groundwater solution changes during reaction of the basalt and basalt/bentonite included initial decreases in pH and sodium concentration presumably due to smectite formation. This initial trend subsequently reversed in the basalt system with pH rising to ca. 7.5 and sodium increasing to the starting value. Steady state pH values for the basalt/bentonite system were ca. 6.4. The basalt + deionized water test exhibited a constant rise in pH to ca. 7.9 and release of sodium to solution in response to basalt dissolution. Slightly oxidizing conditions characterized the early part of all of the experiments followed by a decrease in fO2 to 10−31 to 10−32 These results are consistent with other work at similar and lower temperatures, suggesting that the packing material will react in the waste package environment to produce slightly alkaline, reducing conditions.

The Role of Eh in Nuclear Waste Form Dissolution

1983 ◽  
Vol 26 ◽  
Author(s):  
W. Phelps Freeborn ◽  
William B. White
Keyword(s):  
Redox Potential ◽  
Nuclear Waste ◽  
Palladium Catalyst ◽  
Platinum Electrode ◽  
Thermodynamic Calculations ◽  
Waste Form ◽  
Series Of Experiments ◽  
Rapid Kinetics

ABSTRACTA series of experiments was conducted to evaluate the significance of redox potential, Eh, as an independent opensystem variable in the dissolution of nuclear waste glasses and ceramics. The standard platinum electrode can be used in leach solutions. Measurements on couples with rapid kinetics such as Fe+++/Fe++ give results in agreement with thermodynamic calculations. Highly reducing leaching solutions can be obtained by passing hydrogen through the solvent in the presence of a palladium catalyst.

Corrosion Resistant Canisters for Nuclear Waste Isolation

1982 ◽  
Vol 15 ◽  
Author(s):  
Nicholas J. Magnani
Keyword(s):  
Nuclear Waste ◽  
Waste Disposal ◽  
Material Selection ◽  
Nuclear Waste Disposal ◽  
Waste Form ◽  
Corrosion Resistant ◽  
Engineered Barriers ◽  
Selection Of

ABSTRACTCorrosion resistant canisters are an important component of the engineered barriers of a nuclear waste disposal system. In addition to providing containment for the waste form during transportation and emplacement, a durable canister can eliminate hydrothermal interactions with the waste form. The selection of a repository site and emplacement technique will affect canister design and could also impact material selection. While there are still many issues to be resolved, there are two different concepts being evaluated to provide durable canisters for waste disposal: (1) canisters fabricated out of extremely corrosion resistant materials such as Ti-base or Ni-base alloys, and (2) canisters fabricated out of less durable materials but designed with a corrosion allowance. Each of these types of canisters could fail to meet the design objectives through a variety of failure processes. The more important of these are discussed.

scholarly journals Enhanced Electrokinetic Remediation for the Removal of Heavy Metals from Contaminated Soils

2021 ◽  
Vol 11 (4) ◽  
pp. 1799
Author(s):  
Claudio Cameselle ◽  
Susana Gouveia ◽  
Adrian Cabo
Keyword(s):  
Heavy Metals ◽  
Citric Acid ◽  
Organic Acids ◽  
Contaminated Soils ◽  
Electrokinetic Remediation ◽  
Deionized Water ◽  
Soil Specimen ◽  
Removal Of Heavy Metals ◽  
Ph Conditions ◽  
Neutral Metal

The electrokinetic remediation of an agricultural soil contaminated with heavy metals was studied using organic acids as facilitating agents. The unenhanced electrokinetic treatment using deionized water as processing fluid did not show any significant mobilization and removal of heavy metals due to the low solubilization of metals and precipitation at high pH conditions close to the cathode. EDTA and citric acid 0.1 M were used as facilitating agents to favor the dissolution and transportation of metals. The organic acids were added to the catholyte and penetrated into the soil specimen by electromigration. EDTA formed negatively charged complexes. Citric acid formed neutral metal complexes in the soil pH conditions (pH = 2–4). Citric acid was much more effective in the dissolution and transportation out of the soil specimen of complexed metals. In order to enhance the removal of metals, the concentration of citric acid was increased up to 0.5 M, resulting in the removal of 78.7% of Cd, 78.6% of Co, 72.5% of Cu, 73.3% of Zn, 11.8% of Cr and 9.8% of Pb.

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