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Chemical modeling of irreversible reactions in nuclear waste-water-rock systems

Description: Chemical models of aqueous geochemical systems are usually built on the concept of thermodynamic equilibrium. Though many elementary reactions in a geochemical system may be close to equilibrium, others may not be. Chemical models of aqueous fluids should take into account that many aqueous redox reactions are among the latter. The behavior of redox reactions may critically affect migration of certain radionuclides, especially the actinides. In addition, the progress of reaction in geochemical systems requires thermodynamic driving forces associated with elementary reactions not at equilibrium, which are termed irreversible reactions. Both static chemical models of fluids and dynamic models of reacting systems have been applied to a wide spectrum of problems in water-rock interactions. Potential applications in nuclear waste disposal range from problems in geochemical aspects of site evaluation to those of waste-water-rock interactions. However, much further work in the laboratory and the field will be required to develop and verify such applications of chemical modeling.
Date: February 1, 1981
Creator: Wolery, T.J.
Partner: UNT Libraries Government Documents Department

Computer simulation of temperature-dependent equilibrium precipitation

Description: The EQ3/EQ6 software package contains two computer codes (EQ3 and EQ6) and data files which form a useful tool in modeling precipitation from geothermal fluids caused by heating or cooling. The data files contain information on 140 aqueous species and nearly 150 minerals, and permit calculations over the temperature interval 0 to 350/sup 0/C. Assumption of homogeneous thermodynamic equilibrium in aqueous solution permits calculation of the driving forces for precipitation as measured by the affinity (log Q/K) for each such reaction. Further assumption of precipitation and heterogeneous equilibrium for any mineral whose affinity would otherwise exceed a value of zero permits determination of the identity of the precipitates, their masses and volumes, and the temperature ranges in which they form. The EQ3/EQ6 capability was used to determine the effects of temperature increase on formation of precipitates form Salton Sea water.
Date: July 10, 1979
Creator: Wolery, T.J.
Partner: UNT Libraries Government Documents Department

Calculation of chemical equilibrium between aqueous solution and minerals: the EQ3/6 software package. [In FORTRAN extended 4. 6 for CDC6600 and 7600]

Description: The newly developed EQ/36 software package computes equilibrium models of aqueous geochemical systems. The package contains two principal programs: EQ3 performs distribution-of-species calculations for natural water compositions; EQ6 uses the results of EQ3 to predict the consequences of heating and cooling aqueous solutions and of irreversible reaction in rock--water systems. The programs are valuable for studying such phenomena as the formation of ore bodies, scaling and plugging in geothermal development, and the long-term disposal of nuclear waste. EQ3 and EQ6 are compared with such well-known geochemical codes as SOLMNEQ, WATEQ, REDEQL, MINEQL, and PATHI. The data base allows calculations in the temperature interval 0 to 350{sup 0}C, at either 1 atm-steam saturation pressures or a constant 500 bars. The activity coefficient approximations for aqueous solutes limit modeling to solutions of ionic strength less than about one molal. The mathematical derivations and numerical techniques used in EQ6 are presented in detail. The program uses the Newton--Raphson method to solve the governing equations of chemical equilibrium for a system of specified elemental composition at fixed temperature and pressure. Convergence is aided by optimizing starting estimates and by under-relaxation techniques. The minerals present in the stable phase assemblage are found by several empirical methods. Reaction path models may be generated by using this approach in conjunction with finite differences. This method is analogous to applying high-order predictor--corrector methods to integrate a corresponding set of ordinary differential equations, but avoids propagation of error (drift). 8 figures, 9 tables.
Date: February 1, 1979
Creator: Wolery, T.J.
Partner: UNT Libraries Government Documents Department

EQ3NR, a computer program for geochemical aqueous speciation-solubility calculations: Theoretical manual, user`s guide, and related documentation (Version 7.0); Part 3

Description: EQ3NR is an aqueous solution speciation-solubility modeling code. It is part of the EQ3/6 software package for geochemical modeling. It computes the thermodynamic state of an aqueous solution by determining the distribution of chemical species, including simple ions, ion pairs, and complexes, using standard state thermodynamic data and various equations which describe the thermodynamic activity coefficients of these species. The input to the code describes the aqueous solution in terms of analytical data, including total (analytical) concentrations of dissolved components and such other parameters as the pH, pHCl, Eh, pe, and oxygen fugacity. The input may also include a desired electrical balancing adjustment and various constraints which impose equilibrium with special pure minerals, solid solution end-member components (of specified mole fractions), and gases (of specified fugacities). The code evaluates the degree of disequilibrium in terms of the saturation index (SI = 1og Q/K) and the thermodynamic affinity (A = {minus}2.303 RT log Q/K) for various reactions, such as mineral dissolution or oxidation-reduction in the aqueous solution itself. Individual values of Eh, pe, oxygen fugacity, and Ah (redox affinity) are computed for aqueous redox couples. Equilibrium fugacities are computed for gas species. The code is highly flexible in dealing with various parameters as either model inputs or outputs. The user can specify modification or substitution of equilibrium constants at run time by using options on the input file.
Date: September 14, 1992
Creator: Wolery, T. J.
Partner: UNT Libraries Government Documents Department

Fixed-fugacity option for the EQ6 geochemical reaction path code

Description: EQ3/6 is a software package used to model aqueous geochemical systems. The EQ6 code allows reaction paths of dynamic systems to be calculated. This report describes a new option for the EQ6 computer program that permits the fugacity of any gas in the EQ6 data base to be set to a fixed value. This capability permits simulation of the effect of rapid chemical exchange with a large external gas reservoir by allowing the user to fix the fugacities of selected gas species. Geochemical environments such as groundwater systems open to the atmosphere (e.g., the unsaturated zone), natural aqueous systems that form closed systems at depth, and experimental systems that use controlled atmospheres can be modeled. Two of the principal geochemical weathering agents, CO{sub 2} and O{sub 2}, are the most likely gas species for which this type of exchange may be important. An example of the effect of constant CO{sub 2} fugacity on both open and closed systems is shown for the case of albite dissolution (NaAlSi{sub 3}O{sub 8}) in distilled water. This example demonstrates that the effects of imposed fugacities on geochemical systems can be considerable. This computer code is used in the Nevada Nuclear Waste Storage Investigations Project. 15 refs., 8 figs.
Date: December 20, 1984
Creator: Delany, J.M. & Wolery, T.J.
Partner: UNT Libraries Government Documents Department

EQ3/6, a software package for geochemical modeling of aqueous systems: Package overview and installation guide (Version 7.0)

Description: EQ3/6 is a software package for geochemical modeling of aqueous systems. This report describes version 7.0. The major components of the package include: EQ3NR, a speciation-solubility code; EQ6, a reaction path code which models water/rock interaction or fluid mixing in either a pure reaction progress mode or a time mode; EQPT, a data file preprocessor, EQLIB, a supporting software library; and five supporting thermodynamic data files. The software deals with the concepts of thermodynamic equilibrium, thermodynamic disequilibrium, and reaction kinetics. The five supporting data files contain both standard state and activity coefficient-related data. Three support the use of the Davies or B-dot equations for the activity coefficients; the other two support the use of Pitzer`s equations. The temperature range of the thermodynamic data on the data files varies from 25{degree}C only to 0--300{degree}C. EQPT takes a formatted data file (a data0 file) and writes an unformatted near-equivalent called a datal file, which is actually the form read by EQ3NR and EQ6. EQ3NR is useful for analyzing groundwater chemistry data, calculating solubility limits, and determining whether certain reactions are in states of partial equilibrium or disequilibrium. It is also required to initialize an EQ6 calculation. EQ6 models the consequences of reacting an aqueous solution with a set of reactants which react irreversibly. It can also model fluid mixing and the consequences of changes in temperature. This code operates both in a pure reaction progress frame and in a time frame.
Date: September 14, 1992
Creator: Wolery, T.J.
Partner: UNT Libraries Government Documents Department

Extension of the EQ3/6 computer codes to geochemical modeling of brines

Description: Recent modifications to the EQ3/6 geochemical modeling software package provide for the use of Pitzer's equations to calculate the activity coefficients of aqueous species and the activity of water. These changes extend the range of solute concentrations over which the codes can be used to dependably calculate equilibria in geochemical systems, and permit the inclusion of ion pairs, complexes, and undissociated acids and bases as explicit component species in the Pitzer model. Comparisons of calculations made by the EQ3NR and EQ6 compuer codes with experimental data confirm that the modifications not only allow the codes to accurately evaluate activity coefficients in concentrated solutions, but also permit prediction of solubility limits of evaporite minerals in brines at 25/sup 0/C and elevated temperatures. Calculations for a few salts can be made at temperatures up to approx. 300/sup 0/C, but the temperature range for most electrolytes is constrained by the availability of requisite data to values less than or equal to 100/sup 0/C. The implementation of Pitzer's equations in EQ3/6 allows application of these codes to problems involving calculation of geochemical equilibria in brines; such as evaluation of the chemical environment which might be anticipated for nuclear waste canisters located in a salt repository. 26 references, 3 figures, 1 table.
Date: October 23, 1984
Creator: Jackson, K.J. & Wolery, T.J.
Partner: UNT Libraries Government Documents Department

Post emplacement environment of waste packages

Description: Experiments have been conducted as part of the Nevada Nuclear Waste Storage Investigations Project to determine the changes in water chemistry due to reaction of the Topopah Spring tuff with natural groundwater at temperatures up to 150{sup 0}C. The reaction extent has been investigated as a function of rock-to-water ratio, temperature, reaction time, physical state of the samples, and geographic location of the samples within the tuff unit. Results of these experiments will be used to provide information on the water chemistry to be expected if a high-level waste repository were to be constructed in the Topopah Spring tuff. 6 references, 5 figures, 1 table.
Date: December 31, 1983
Creator: Knauss, K.G.; Oversby, V.M. & Wolery, T.J.
Partner: UNT Libraries Government Documents Department

EQPT, a data file preprocessor for the EQ3/6 software package: User`s guide and related documentation (Version 7.0); Part 2

Description: EQPT is a data file preprocessor for the EQ3/6 software package. EQ3/6 currently contains five primary data files, called datao files. These files comprise alternative data sets. These data files contain both standard state and activity coefficient-related data. Three (com, sup, and nea) support the use of the Davies or B-dot equations for the activity coefficients; the other two (hmw and pit) support the use of Pitzer`s (1973, 1975) equations. The temperature range of the thermodynamic data on these data files varies from 25{degrees}C only to 0-300{degrees}C. The principal modeling codes in EQ3/6, EQ3NR and EQ6, do not read a data0 file, however. Instead, these codes read an unformatted equivalent called a data1 file. EQPT writes a datal file, using the corresponding data0 file as input. In processing a data0 file, EQPT checks the data for common errors, such as unbalanced reactions. It also conducts two kinds of data transformation. Interpolating polynomials are fit to data which are input on temperature adds. The coefficients of these polynomials are then written on the datal file in place of the original temperature grids. A second transformation pertains only to data files tied to Pitzer`s equations. The commonly reported observable Pitzer coefficient parameters are mapped into a set of primitive parameters by means of a set of conventional relations. These primitive form parameters are then written onto the datal file in place of their observable counterparts. Usage of the primitive form parameters makes it easier to evaluate Pitzer`s equations in EQ3NR and EQ6. EQPT and the other codes in the EQ3/6 package are written in FORTRAN 77 and have been developed to run under the UNIX operating system on computers ranging from workstations to supercomputers.
Date: December 17, 1992
Creator: Daveler, S.A. & Wolery, T.J.
Partner: UNT Libraries Government Documents Department

EQ6, a computer program for reaction path modeling of aqueous geochemical systems: Theoretical manual, user`s guide, and related documentation (Version 7.0); Part 4

Description: EQ6 is a FORTRAN computer program in the EQ3/6 software package (Wolery, 1979). It calculates reaction paths (chemical evolution) in reacting water-rock and water-rock-waste systems. Speciation in aqueous solution is an integral part of these calculations. EQ6 computes models of titration processes (including fluid mixing), irreversible reaction in closed systems, irreversible reaction in some simple kinds of open systems, and heating or cooling processes, as well as solve ``single-point`` thermodynamic equilibrium problems. A reaction path calculation normally involves a sequence of thermodynamic equilibrium calculations. Chemical evolution is driven by a set of irreversible reactions (i.e., reactions out of equilibrium) and/or changes in temperature and/or pressure. These irreversible reactions usually represent the dissolution or precipitation of minerals or other solids. The code computes the appearance and disappearance of phases in solubility equilibrium with the water. It finds the identities of these phases automatically. The user may specify which potential phases are allowed to form and which are not. There is an option to fix the fugacities of specified gas species, simulating contact with a large external reservoir. Rate laws for irreversible reactions may be either relative rates or actual rates. If any actual rates are used, the calculation has a time frame. Several forms for actual rate laws are programmed into the code. EQ6 is presently able to model both mineral dissolution and growth kinetics.
Date: October 9, 1992
Creator: Wolery, T.J. & Daveler, S.A.
Partner: UNT Libraries Government Documents Department

EQ3/6 software maintenance and support summary

Description: EQ3/6 is a software package for modeling chemical interactions in aqueous systems of geologic and engineering interest, such as water/rock, water/nuclear waste, and water/nuclear waste/rock. It is being used for a broad range of applications for the Yucca Mountain Site Characterization Project (YMSCP), including predictions of mineralogical changes in the altered zone, man-made materials investigations, and calculations of the long-term release of radionuclides from a variety of waste forms. Version 7.2a was the first qualified version of this software (certified on Aug. 17, 1994). Version 7.2b followed on Aug. 18, 1995 and is the most recent qualified version; it differs from version 7.2a only in that defects noted in the qualification report (Kishi, 7/12/94) were resolved. The present report describes the software maintenance and support activities that were carried out for the Version 7 line of the software in FY97. The most important of these activities is maintaining a system for the logging, documenting, and resolving software defects. This is required by the QARD (Supplement 1) in order for the software to remain certified. Other maintenance activities are necessary to retain functionality as computer hardware, operating systems, programming languages, and compilers change. In FY97, 12 software defects were logged and resolved, and two more were logged and awaiting resolution. These ranged in nature from the trivial to the serious. The corrected software will be released as version 7.2c in the first quarter of FY98. A version 8 line of totally rewritten code in modern Fortran, restructured to support new functionality, and with new capabilities for ion exchange modeling, pressure corrections, and redox disequilibrium, was completed to a baseline level in FY95. Subsequent activities required to complete qualification were not funded in FY96 and FY97. However, in FY97, each line of the software (version 7 and version 8) has been checked ...
Date: September 26, 1997
Creator: Wolery, T. J.
Partner: UNT Libraries Government Documents Department

Letter report: status on code maintenance (EQ3/6)

Description: EQ3/6 is a software package for geochemical modeling of aqueous systems, such as water/rock or waste/water rock. It is being developed for a variety of applications in geochemical studies for the Yucca Mountain Site Characterization Project. Version 7.2a was the first version of this software to be certified for use in quality- affecting work (originally issued for use in non-quality-affecting work only on 12/28/93; certified on S/17/94). In the past year, the Version 7 line software has been maintained while the new Version 8 line has been developed. In this period, sixteen defect reports have been logged and resolved. Corrected software is being released as Version 7.2b. Defect reporting and resolution for the Version 7 line will continue until all released versions in this line are retired, perhaps six months to a year after Version 8.0 is released later this year. The Version 7 software is written in Fortran 77, technically speaking, but incorporates many aspects of older Fortran. The Version 8 software is written in a much more modern Fortran, technically somewhere between Fortran 77 and Fortran 90. Future code maintenance activities will include a more complete move to Fortran 90, as well as continued maintaining of defect reporting and resolution.
Date: April 24, 1995
Creator: Wolery, T. J.
Partner: UNT Libraries Government Documents Department

LLNL Yucca Mountain project - near-field environment characterization technical area: Letter report: EQ3/6 version 8: differences from version 7

Description: EQ3/6 is a software package for geochemical modeling of aqueous systems, such as water/rock or waste/water rock. It is being developed for a variety of applications in geochemical studies for the Yucca Mountain Site Characterization Project. The software has been extensively rewritten for Version 8. The source code has been extensively modernized. The software is now written in Fortran 77 with the most common extensions that are part of the new Fortran 90 standard. The architecture of the software has been improved for better performance and to allow the incorporation of new functional capabilities in Version 8 and planned subsequent versions. In particular, the structure of the major data arrays has been significantly altered and extended. Three new major functional capabilities have been incorporated in Version 8. The first of these allows the treatment of redox disequilibrium in reaction-path modeling. This is a natural extension of the long-running capability of providing for such disequilibrium in static speciation-solubility calculations. Such a capability is important, for example, when dealing with systems containing organic species and certain dissolved gas species. The user defines (and sets the controls for) the components in disequilibrium. Such corrections can now be made if the requisite data are present on a supporting data file. At present, this capability is supported only by the SHV data file, which is based on SUPCRT92. Equilibrium constants and other thermodynamic quantities are correct1961ed for pressures which lie off a standard curve, which is defined on the supporting data file and ordinarily corresponds to 1.013 bar up to IOOC, and the steam/liquid water equilibrium pressure up to 300C. The third new major capability is generic ion exchange option previously developed in prototype in a branch Version 7 level version of EQ3/6 by Brian Viani, Bill Bourcier, and Carol Bruton. This option has been ...
Date: September 29, 1994
Creator: Wolery, T.J.
Partner: UNT Libraries Government Documents Department

EQ3/6: status and applications

Description: EQ3/6 is a set of related computer codes and data files for use in geochemical modeling of aqueous systems. The EQ3/6 package centers around two large computer codes, EQ3NR and EQ6, which are supported by a common thermodynamic data base. EQ3NR is a speciation-solubility code, whose function is to compute a model of the state of an aqueous solution. This code is very flexible in terms of the input that it will accept. EQ6 is a reaction-path code, which calculates models of changes in aqueous systems as they proceed toward a state of overall chemical equilibrium. EQ3/6 prior to FY83 had no capability for modeling brines, because the approximations for calculating the thermodynamic activity of water and the activity coefficients of the solute species were restricted to low ionic strengths ({le} 1.0 molal). An option has been added to use Pitzer`s equations for such calculations. At present, EQ3/6 contains two alternate Pitzer coefficient data bases. Several improvements have been made to the EQ6 code. Prior to FY83, the code could run models of mineral dissolution kinetics, but could not calculate models of precipitation kinetics. This problem has been overcome by additional code development. The speed of non-kinetic EQ6 calculations has recently been enhanced by the creation of two new calculational modes, economy mode and super economy mode. A calculational mode to simulate systems open to large gas reservoirs has also been developed. 34 references.
Date: December 1, 1984
Creator: Wolery, T.J.; Isherwood, D.J.; Jackson, K.J.; Delany, J.M. & Puigdomenech, I.
Partner: UNT Libraries Government Documents Department

Hydrothermal growth kinetics of Np(IV) oxide

Description: Toulouse, France All previous knowledge leading to this estimate is of NpO2(c) is indirect, based on thermodynamic cycles. The phase itself has heretofore not been observed as a precipitate from aqueous solution. Recent attempts (e.g., Nitsche et al., 1993; Efurd et al., 1996) to establish solubility controls on Np in oxidizing groundwaters (including J-13 groundwater) starting from high concentrations (i.e., supersaturation) have shown the formation of one or both of two Np(V) phases, NaNpO2CO3:3.5H2O(c) (with variable stoichiometry) and Np2O5(c). These are both highly soluble, yielding Np concentrations on the order of 1 x 10 -4 to 1 x 10 -3 molal, in accord with existing thermodynamic data for these phases. No evidence was found of the formation of NpO2(c). Under reducing conditions, experiments (Rai et al., 1987 and references cited therein) have shown the formation of Np(IV) polymer, which may be viewed as a hydrated form of NpO2. It is orders of magnitude less soluble than the Np(V) phases, but still orders of magnitude more soluble than NpO2(c). No undersaturation experiments with NpO2(c) are known to have been performed. However, both NpO2(c) and Np(IV) polymer are known to be difficult to dissolve. We have hypothesized that NpO2(c) is simply a phase that is slow to form at low temperature. In this regard, it would be analogous to such minerals as quartz, dolomite, and hematite. It is well known that it is difficult to impossible to demonstrate the formation of such minerals in low temperature experiments on feasible time scales. However, it is possible to demonstrate their formation and measure the kinetics of the process by conducting experiments at elevated temperatures, generally in the range of 150-300 o C (e.g., Rimstidt and Barnes, 1980; Sibley et al., 1984). By developing kinetic models, it should be possible to estimate the appropriate time ...
Date: May 11, 1998
Creator: Palmer, C. E.; Roberts, K. & Wolery, T. J.
Partner: UNT Libraries Government Documents Department

Geochemical modeling (EQ3/6) plan: Office of Civilian Radioactive Waste Management Program

Description: This plan replaces an earlier plan for the Nevada Nuclear Waste Storage Investigations (NNWSI) Project. It includes activities for all repository projects in the Office of Geologic Repositories: NNWSI, the Basalt Waste Isolation Project, the Salt Repository Project, and the Crystalline Project. Each of these projects is part of the Office of Civilian Radioactive Waste Management (OCRWM) Program. The scope of work for fiscal years 1986 to 1992 includes the work required to upgrade the geochemical codes and supporting data bases, to permit modeling of chemical processes associated with nuclear waste repositories in four geological environments: tuff, salt, basalt, and crystalline rock. Planned tasks include theoretical studies and code development to take account of the effects of precipitation kinetics, sorption, solid solutions, glass/water interactions, variable gas fugacities, and simple mass transport. Recent progress has been made in the ability of the codes to account for precipitation kinetics, highly-saline solutions, and solid solutions. Transition state theory was re-examined resulting in new insights that will provide the foundation for further improvements necessary to model chemical kinetics. Currently there is an increased effort that is concentrated on the supporting data base. For aqueous species and solid phases, specific to nuclear waste, requisite thermodynamic values reported in the literature are being evaluated and for cases where essential data is lacking, laboratory measurements will be carried out. Significant modifications and expansions have been made to the data base. During FY86, the total number of species in the data base has almost doubled and many improvements have been made with regard to consistency, organization, user applications, and documentation. Two Ridge computers using a RISC implementation of UNIX were installed; they are completely dedicated EQ3/6 machines.
Date: August 28, 1986
Creator: McKenzie, W.F.; Wolery, T.J.; Delany, J.M.; Silva, R.J.; Jackson, K.J.; Bourcier, W.L. et al.
Partner: UNT Libraries Government Documents Department

The EQ3/6 software package for geochemical modeling: Current status

Description: EQ3/6 is a software package for modeling chemical and mineralogic interactions in aqueous geochemical systems. The major components of the package are EQ3NR (a speciation-solubility code), EQ6 (a reaction path code), EQLIB (a supporting library), and a supporting thermodynamic data base. EQ3NR calculates aqueous speciation and saturation indices from analytical data. It can also be used to calculate compositions of buffer solutions for use in laboratory experiments. EQ6 computes reaction path models of both equilibrium step processes and kinetic reaction processes. These models can be computed for closed systems and relatively simple open systems. EQ3/6 is useful in making purely theoretical calculations, in designing, interpreting, and extrapolating laboratory experiments, and in testing and developing submodels and supporting data used in these codes. The thermodynamic data base supports calculations over the range 0-300{degree}C. 60 refs., 2 figs.
Date: July 1, 1988
Creator: Wolery, T.J.; Jackson, K.J.; Bourcier, W.L.; Bruton, C.J.; Viani, B.E.; Knauss, K.G. et al.
Partner: UNT Libraries Government Documents Department

Combine Studies Pertaining to the Solubility of Neptunium in Oxidizing Aqueous Systems

Description: The report combines two separate studies dealing with different aspects of the behavior of neptunium in oxidizing aqueous systems. The goal of both studies is to obtain a better understanding of what would control the concentration of neptunium in oxidizing groundwaters upon release from a geologic high-level waste repository. {sup 237}Np has a very long half-life, and consequently tends to appear as a component of concern in long-term dose calculations. Part A examines the formation of NpO{sub 2} [Np(IV) oxide] from aqueous Np(V) under oxidizing conditions, using elevated temperature as a means of accelerating putative slow kinetics. According to thermodynamic data, NpO{sub 2} should be the stable Np solid, even though Np is generally thought to be mainly some form of Np(V) under oxidizing conditions. The first observed precipitation of this solid from aqueous solution under any conditions is reported. This result suggests, but does not prove, that long-term very slow formation of NpO{sub 2} might be an important long-term control on neptunium migration. Even at 200{sup o}C, the kinetics can be sluggish on typical experimental time scales. Though not reported in Part A, a similar situation may exist for Pu, and NpO{sub 2} and PuO{sub 2} may potentially form solid solutions. Under reducing conditions, UO{sub 2} might join in. Part B examines the interaction of Np(V) with the uranium mineral schoepite. Is neptunium incorporated into the crystal structure as a solid-solution component, or does it just sorb onto the mineral surface? The results presented here suggest that it basically just sorbs onto the surface, which would be a less effective process in limiting neptunium migration. This is not a surprising result, as schoepite is a relatively simple solid of U(VI). There is no obvious means to compensate for the charge difference between U(VI) and Np(V) without introducing unfavorable energetics. ...
Date: September 15, 2000
Creator: Wolery, T. J.; Robert, K. E.; Wruck, D. A.; Brachmann, A. & Palmer, C. E. A.
Partner: UNT Libraries Government Documents Department

LLNL/JNC repository collaboration interim progress report

Description: Under this Annex, a research program on the near-field performance assessment related to the geological disposal of radioactive waste will be carried out at the Lawrence Livermore National Laboratory (LLNL) in close collaboration with the Power Reactor and Nuclear Fuel Development Corporation of Japan (PNC). This program will focus on activities that provide direct support for PNC's near-term and long-term needs that will, in turn, utilize and further strengthen US capabilities for radioactive waste management. The work scope for two years will be designed based on the PNC's priorities for its second progress report (the H12 report) of research and development for high-level radioactive waste disposal and on the interest and capabilities of the LLNL. The work will focus on the chemical modeling for the near-field environment and long-term mechanical modeling of engineered barrier system as it evolves. Certain activities in this program will provide for a final iteration of analyses to provide additional technical basis prior to the year 2000 as determined in discussions with the PNC's technical coordinator. The work for two years will include the following activities: Activity 1: Chemical Modeling of EBS Materials Interactions--Task 1.1 Chemical Modeling of Iron Effects on Borosilicate Glass Durability; and Task 1.2 Changes in Overpack and Bentonite Properties Due to Metal, Bentonite and Water Interactions. Activity 2: Thermodynamic Database Validation and Comparison--Task 2.1 Set up EQ3/6 to Run with the Pitzer-based PNC Thermodynamic Data Base; Task 2.2 Provide Expert Consultation on the Thermodynamic Data Base; and Task 2.3 Provide Analysis of Likely Solubility Controls on Selenium. Activity 3: Engineered Barrier Performance Assessment of the Unsaturated, Oxidizing Transient--Task 3.1 Apply YMIM to PNC Transient EBS Performance; Task 3.2 Demonstrate Methods for Modeling the Return to Reducing Conditions; and Task 3.3 Evaluate the Potential for Stress Corrosion Cracking in PNC Waste Packages. Activity ...
Date: July 1, 1999
Creator: Bourcier, W.L.; Couch, R.G.; Gansemer, J.; Halsey, W.G.; Palmer, C.E.; Sinz, K.H. et al.
Partner: UNT Libraries Government Documents Department