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Solid phases and solution species of different elements in geologic environments

Description: An investigation was conducted to predict from thermodynamic data the nature of the solid phases and solution species in various weathering environments of different elements (Am, Sb, Ce, Cs, Co, Cm, Eu, I, Np, Pu, Pm, Ra, Ru, Sr, Tc, T, U, and Zr) that are present in radioactive wastes, to predict the degree of adsorption of different elements by the solid matrices and to compare these predictions with observed results, and to determine the influence of different factors (such as Ph, Eh, complexing ligands) on total pore-water concentration and the nature of solution species of selected elements. Based on the nature of the predominant solution species, qualitative predictions regarding the adsorption and movement of various elements can be made. Soils and sediments mainly show cation exchange capacities (since these materials carry a large net negative charge) and to a limited extent, anion exchange capacities. Thus, most cations migrate through the soil or rock column at speeds slower than the groundwater. Relative to each other, the trivalent cations generally move the slowest, the divalent cations at intermediate velocities and the monovalent cations most rapidly. Tritium is unique in that it readily substitutes for hydrogen in water and migrates, therefore, at the same velocity as water. The simple anions tend to migrate through soils and rocks with little reaction because usually a pH of less than 4 is required to activate a significant soil anion exchange capacity. The migration and retention of inorganic complex species (mononuclear and polynuclear) would also be dependent upon the charge and size of the species. The behavior of organic complexed species of elements is difficult to predict because of the lack of knowledge regarding the exact nature of the organic ligands, a wide variation in amounts and types of organic ligands, and the size and solubility ...
Date: March 1, 1978
Creator: Rai, D. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

Waste isolation safety assessment program. Controlled sample program publication number 2: interlaboratory comparison of batch Kd values

Description: Objectives were to: (1) ascertain whether different experimenters obtain the same results for the adsorption of Cs, Sr and Pu using common rocks, standard solutions and a prescribed method; and (2) compare the results obtained by individual laboratories using different experimental methodologies and resolve any differences found or determine what conversions can be made to compare results from one method with another. Results from Objective 1 indicate that several parameters that were uncontrolled may have affected results. The uncontrolled parameters were: (1) method of tracer addition to solution, (2) solution to rock ratio, (3) initial tracer concentration in influent solution, (4) particle size distribution, (5) solid--solution separation method, (6) sample containers, and (7) temperature. Observed Kds for Cs and Sr in brine showed agreement among laboratories for both limestone and basalt rock samples. Comparable results were also found for Sr and Cs in the basalt groundwater. Results for Kd(Cs) in the limestone groundwater varied over three orders of magnitude, and Kd(Sr) varied by one order of magnitude in the limestone system. Observed Kd values for Pu typically varied by two to three orders of magnitude in all systems studied. Adsorption of Pu by container walls and by colloidal particles caused much of the variation in Kd(Pu). Direct measurement of Pu adsorbed by the rock (rather than measured by the difference between influent and effluent activities) also failed to reduce the Kd(Pu) variability.
Date: June 1, 1979
Creator: Relyea, J.F. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

Conceptual adsorption models and open issues pertaining to performance assessment

Description: Recently several articles have been published that question the appropriateness of the distribution coefficient, Rd, concept to quantify radionuclide migration. Several distinct issues are raised by various critics. In this paper I provide some perspective on issues surrounding the modeling of nuclide retardation. The first section defines adsorption terminology and discusses various adsorption processes. The next section describes five commonly used adsorption conceptual models, specifically emphasizing what attributes that affect adsorption are explicitly accommodated in each model. I also review efforts to incorporate each adsorption model into performance assessment transport computer codes. The five adsorption conceptual models are (1) the constant Rd model, (2) the parametric Rd model, (3) isotherm adsorption models, (4) mass-action adsorption models, and (5) surface-complexation with electrostatics models. The final section discusses the adequacy of the distribution ratio concept, the adequacy of transport calculations that rely on constant retardation factors and the status of incorporating sophisticated adsorption models into transport codes.
Date: October 1, 1991
Creator: Serne, R.J.
Partner: UNT Libraries Government Documents Department

Waste/Rock Interactions Technology Program: the status of radionuclide sorption-desorption studies performed by the WRIT program

Description: The most credible means for radionuclides disposed as solid wastes in deep-geologic repositories to reach the biosphere is through dissolution of the solid waste and subsequent radionuclide transport by circulating ground water. Thus safety assessment activities must consider the physicochemical interactions between radionculides present in ground water with package components, rocks and sediments since these processes can significantly delay or constrain the mass transport of radionuclides in comparison to ground-water movement. This paper focuses on interactions between dissolved radiouclides in ground water and rocks and sediments away from the near-field repository. The primary mechanism discussed is adsorption-desorption, which has been studied using two approaches. Empirical studies of adsorption-desorption rely on distribution coefficient measurements while mechanism studies strive to identify, differentiate and quantify the processes that control nuclide retardation.
Date: April 1, 1982
Creator: Serne, R.J. & Relyea, J.F.
Partner: UNT Libraries Government Documents Department

Evaluation of selected neutralizing agents for the treatment of uranium tailings leachates. Laboratory progress report

Description: Laboratory experiments were conducted to evaluate the performance of selected neutralizing agents for the treatment of uranium tailings solutions. Highly acidic tailings solutions (pH<2) from the Lucky Mc Mill in Gas Hills, Wyoming and the Exxon Highlands Mill near Casper, Wyoming were neutralized to a pH of 7 or greater using seven neutralizing agents. Reagents used included: Fly Ash from Boardman Coal Plant, Boardman, Oregon; Fly Ash from Wyodak Coal Plant, Gillette, Wyoming; Calcium carbonate (CaCO/sub 3/) reagent grade; Calcium hydroxide (Ca(OH)/sub 2/) reagent grade; Magnesium oxide (MgO) reagent grade; Sodium carbonate (Na/sub 2/CO/sub 3/) reagent grade; and Sodium hydroxide (NaOH) reagent grade. Evaluation of the effectiveness for the treatment of uranium tailings solutions for the selected neutralizing agents under controlled laboratory conditions was based on three criteria. The criteria are: (1) treated effluent water quality, (2) neutralized sludge handling and hydraulic properties, and (3) reagent costs and acid neutralizing efficiency. On the basis of these limited laboratory results calcium hydroxide or its dehydrated form CaO (lime) appears to be the most effective option for treatment of uranium tailings solutions.
Date: February 1, 1983
Creator: Sherwood, D.R. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

Conceptual adsorption models and open issues pertaining to performance assessment

Description: Recently several articles have been published that question the appropriateness of the distribution coefficient, Rd, concept to quantify radionuclide migration. Several distinct issues are raised by various critics. In this paper I provide some perspective on issues surrounding the modeling of nuclide retardation. The first section defines adsorption terminology and discusses various adsorption processes. The next section describes five commonly used adsorption conceptual models, specifically emphasizing what attributes that affect adsorption are explicitly accommodated in each model. I also review efforts to incorporate each adsorption model into performance assessment transport computer codes. The five adsorption conceptual models are (1) the constant Rd model, (2) the parametric Rd model, (3) isotherm adsorption models, (4) mass-action adsorption models, and (5) surface-complexation with electrostatics models. The final section discusses the adequacy of the distribution ratio concept, the adequacy of transport calculations that rely on constant retardation factors and the status of incorporating sophisticated adsorption models into transport codes.
Date: October 1, 1991
Creator: Serne, R. J.
Partner: UNT Libraries Government Documents Department

One-dimensional model of the movement of trace radioactive solute through soil columns: the PERCOL model

Description: A one-dimensional mathematical model, PERCOL, has been developed to predict the movement of radionuclides through porous media as a function of measurable chemical parameters of the media. Laboratory column studies were conducted to verify the model. System parameters considered include soil type, radionuclide type, waste composition, flow rate, column length, and soil saturation. The agreement between measured radionuclide movement and that predicted by the model is considered good.(auth)
Date: January 1, 1972
Creator: Routson, R.C. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

PERCOL user's manual

Description: For Atlantic Richfield Hanford Co., Richland, Wash. Research being conducted under the Radionuclides in Soils Program is attempting to predict the distribution and movement of liquid wastes in the heterogeneous subsurface environment of the Hanford Reservation. As part of this program, a transport model is being developed to predict chemical phenomena in soil-waste reactions. This document describes the use of the PERCOL model, which was developed as a simplified one-dimensional precursor to the transport model. PERCOL numerically describes the complex chemical reactions which occur during percolation of a waste solution through a porous media. This User's Manual describes the main program (PERCOL) and two subroutines MEWTIT and DIST) and gives procedures for accessing these programs, inputting data to them and interpreting the output. (auth)
Date: January 1, 1973
Creator: Serne, R.J. & Routson, R.C.
Partner: UNT Libraries Government Documents Department

Strontium-90 adsorption-desorption properties and sediment characterization at the 100 N-Area

Description: Strontium-90 ({sup 90}Sr) has been seeping into the Columbia River since the early 1980s. The likely source is subsurface migration of {sup 90}Sr from once-through cooling water from the Hanford N Reactor disposed into the two disposal crib/trench facilities. Background information has been provided on the operational history of the two liquid waste disposal facilities and some of the regulatory drivers that have lead to the various characterization activities and remediation demonstrations being performed to help choose future full-scale remediation alternatives. The work presented in this topical report had two main objectives. First, we obtained numerous borehole samples from newly installed wells/borings and performed physical and chemical characterization that,included particle size analysis, moisture content, and Strontium-90, Tritium and gamma activity analyses to help improve the conceptual model of where the contaminants currently reside in the sediments. The second objective was to perform laboratory adsorption-desorption tests using both batch and flow- through column techniques to gather data for use in contaminant transport conceptual models and to aid in specific pump-and-treat calculations needed to interpret a field demonstration.
Date: January 1, 1996
Creator: Serne, R.J. & LeGore, V.L.
Partner: UNT Libraries Government Documents Department

Special waste-form lysimeters-arid: Three-year monitoring report

Description: Regulations governing the disposal of commercial low-level waste require all liquid waste to be solidified before burial. Most waste must be solidified into a rigid matrix such as cement or plastic to prevent waste consolidation and site slumping after burial. These solidification processes affect the rate at which radionuclides and other solutes are released into the soil. In 1983, a program was initiated at Pacific Northwest Laboratory to study the release of waste from samples of low-level radioactive waste that had been commercially solidified. The primary method used by this program is to bury sample waste forms in field lysimeters and monitor leachate composition from the release and transport of solutes. The lysimeter facility consists of 10 lysimeters, each containing one sample of solidified waste. Five different waste forms are being tested, allowing duplicate samples of each one to be evaluated. The samples were obtained from operating nuclear power plants and are actual waste forms routinely generated at these facilities. All solidification was accomplished by commercial processes. Sample size is a partially filled 210-L drum. All containers were removed prior to burial leaving the bare waste form in contact with the lysimeter soil. 11 refs., 14 figs., 16 tabs.
Date: April 1, 1988
Creator: Jones, T.L.; Serne, R.J. & Toste, A.P.
Partner: UNT Libraries Government Documents Department

Interactions of tailings leachate with local liner materials found at Canonsburg, Pennsylvania.

Description: The mill tailings site at Canonsburg, Pennsylvania is the first mill site to receive remedial action under the Department of Energy's Uranium Mill Tailings Remedial Action Program. Part of this remedial action will require excavating the 53,500 m/sup 3/ (70,000 yd/sup 3/) of tailings on the site having a specific activity exceeding 100 pCi/g, and encapsulating these contaminated tailings in a clay-lined cell. As part of the remedial action effort, Pacific Northwest Laboratory has been studying the interactions of tailings and tailings leachate with locally occurring clays proposed for liner materials. These studies include physical and chemical characterization of amended and unamended local clays, chemical characterization of the tailings, column studies of tailings leached with deionized water, and column studies of clays contacted with tailings solutions to determine the attenuation properties of the proposed liner materials. Column studies of tailings leached with deionized water indicated that the Canonsburg tailings could represent a source of soluble radium-226 and uranium-238, several trace metals, cations, and the anions SO/sub 4/, NO/sub 3/, and Cl. Of these soluble contaminants, uranium-238, radium-226, the trace metals As and Mo, and the anions F and SO/sub 4/ were present at levels exceeding maximum concentration levels in the tailings leaching column effluents. However, local clays, both in amended and unamended form were effective in attenuating contaminant migration. The soil amendments tested failed to increase radium attenuation. The tailings leaching studies indicated that the tailings will produce leachates of neutral pH and relatively low contaminant levels for at least 200 years. We believe that compacting the tailings within the encapsulation cell will help to reduce leaching of contaminants from the liner system, since very low permeabilities (<10/sup -8/ cm/s) were observed for even slightly compacted tailings materials.
Date: April 1, 1984
Creator: Dodson, M.E.; Gee, G.W. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

Factors affecting criticality for spent fuel materials in a geologic setting

Description: Following closure of a geologic repository for spent fuel, geologic process may change geometries and spacings, and water may enter the repository. In this study the conditions required for the criticality of spent fuel constituents are determined. Many factors affect criticality, and the effects of various possible post-closure changes are investigated. Factors having the greatest effect on criticality are identified to provide guidance for research programs and for design and evaluation studies. Section II describes the calculational methods and computer codes used to determine critical conditions. Section III of this document addresses effects of the fissile content of spent fuel on criticality. Calculations have been performed to determine the minimum critical mass of spent fuel actinides as a function of the duration of in-reactor fuel exposure for a variety of possible conditions. Section IV addresses the conditions required for criticality under a scenario believed to be highly unlikely but having a unique possibility. Pu quantities and concentrations required for criticality without water were determined for various conditions of Pu separation, rock moderation and reflection, rock impurities and isotopic content of the Pu. Section V addresses the possibility of geochemical processes separating Pu from other spent fuel constituents. Solubilities of U and Pu are calculated for groundwaters characteristic of basalt, tuff, granite, bedded and dome salt. Maximum concentrations which could be adsorbed on geologic media in contact with these groundwaters are then calculated. Comparison of these maximum adsorbed concentrations with the results presented in Section IV yields the conclusion that criticality cannot occur in sorbed deposits of Pu in geologic media due to the low Pu concentrations achievable. The possibility of selective Pu precipitation, however, is not ruled out by these arguments.
Date: April 1, 1981
Creator: Gore, B.F.; Jenquin, U.P. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

Status of sorption information retrieval system

Description: A Sorption Information Retrieval System (SIRS) is being designed to provide an efficient, computerized, data base for information on radionuclide sorption in geologic media. The data bank will include Kd values for a large number of radionuclides occurring in radioactive wastes originating from the commercial nuclear power industry. Kd values determined to date span several groundwater compositions and a wide variety of rock types and minerals. The data system will not only include Kd values, but also background information on the experiments themselves. This will allow the potential user to retrieve not only the Kd values of interest but also sufficient information to evaluate the accuracy and usefulness of the data. During FY-1979, the logic structure of the system was designed, the software programmed, the data categories selected, and the data format specified. About 40% of the approximately 5000 Kd experiments performed by the Waste Isolation Safety Assessment Program (WISAP) and its subcontractors during FY-1977 and FY-1978 have been evaluated, coded and keypunched. Additional software improvements and system testing are needed before the system will be fully operational. A workshop requested by the NEA was held to discuss potential internatioal participation in the data system.
Date: September 1, 1979
Creator: Hostetler, D.D.; Serne, R.J. & Brandstetter, A.
Partner: UNT Libraries Government Documents Department

Uranium mill tailings neutralization: contaminant complexation and tailings leaching studies

Description: Laboratory experiments were performed to compare the effectiveness of limestone (CaCO/sub 3/) and hydrated lime (Ca(OH)/sub 2/) for improving waste water quality through the neutralization of acidic uranium mill tailings liquor. The experiments were designed to also assess the effects of three proposed mechanisms - carbonate complexation, elevated pH, and colloidal particle adsorption - on the solubility of toxic contaminants found in a typical uranium mill waste solution. Of special interest were the effects each of these possible mechanisms had on the solution concentrations of trace metals such as Cd, Co, Mo, Zn, and U after neutralization. Results indicated that the neutralization of acidic tailings to a pH of 7.3 using hydrated lime provided the highest overall waste water quality. Both the presence of a carbonate source or elevating solution pH beyond pH = 7.3 resulted in a lowering of previously achieved water quality, while adsorption of contaminants onto colloidal particles was not found to affect the solution concentration of any constituent investigated. 24 refs., 8 figs., 19 tabs.
Date: May 1, 1985
Creator: Opitz, B.E.; Dodson, M.E. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

Compilation of data to estimate groundwater migration potential for constituents in active liquid discharges at the Hanford Site

Description: A preliminary characterization of the constituents present in the 33 liquid waste streams at the US Department of Energy's Hanford Site has been completed by Westinghouse Hanford Company. In addition, Westinghouse Hanford has summarized the soil characteristics based on drill logs collected at each site that receives these liquid wastes. Literature searches were conducted and available Hanford-specific data were tabulated and reviewed. General literature on organic chemicals present in the liquid waste streams was also reviewed. Using all of this information, Pacific Northwest Laboratory has developed a best estimate of the transport characteristics (water solubility and soil adsorption properties) for those radionuclides and inorganic and organic chemicals identified in the various waste streams. We assume that the potential for transport is qualified through the four geochemical parameters: solubility, distribution coefficient, persistence (radiogenic or biochemical half-life), and volatility. Summary tables of these parameters are presented for more than 50 inorganic and radioactive species and more than 50 organic compounds identified in the liquid waste streams. Brief descriptions of the chemical characteristics of Hanford sediments, solubility, and adsorption processes, and of how geochemical parameters are used to estimate migration in groundwater-sediment environments are also presented. Groundwater monitoring data are tabulated for wells neighboring the facilities that receive the liquid wastes. 91 refs., 16 figs., 23 tabs.
Date: March 1, 1991
Creator: Ames, L.L. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

Methods for determining radionuclide retardation factors: status report

Description: This report identifies a number of mechanisms that retard radionuclide migration, and describes the static and dynamic methods that are used to study such retardation phenomena. Both static and dynamic methods are needed for reliable safety assessments of underground nuclear-waste repositories. This report also evaluates the extent to which the two methods may be used to diagnose radionuclide migration through various types of geologic media, among them unconsolidated, crushed, intact, and fractured rocks. Adsorption is one mechanism that can control radionuclide concentrations in solution and therefore impede radionuclide migration. Other mechanisms that control a solution's radionuclide concentration and radionuclide migration are precipitation of hydroxides and oxides, oxidation-reduction reactions, and the formation of minerals that might include the radionuclide as a structural element. The retardation mechanisms mentioned above are controlled by such factors as surface area, cation exchange capacity, solution pH, chemical composition of the rock and of the solution, oxidation-reduction potential, and radionuclide concentration. Rocks and ground waters used in determining retardation factors should represent the expected equilibrium conditions in the geologic system under investigation. Static test methods can be used to rapidly screen the effects of the factors mentioned above. Dynamic (or column) testing, is needed to assess the effects of hydrodynamics and the interaction of hydrodynamics with the other important parameters. This paper proposes both a standard method for conducting batch Kd determinations, and a standard format for organizing and reporting data. Dynamic testing methods are not presently developed to the point that a standard methodology can be proposed. Normal procedures are outlined for column experimentation and the data that are needed to analyze a column experiment are identified.
Date: April 1, 1980
Creator: Relyea, J.F.; Serne, R.J. & Rai, D.
Partner: UNT Libraries Government Documents Department

Laboratory measurements of contaminant attenuation of uranium mill tailings leachates by sediments and clay liners

Description: We discuss FY82 progress on the development of laboratory tools to aid in the prediction of migration potential of contaminants present in acidic uranium mill tailings leachate. Further, empirical data on trace metal and radionuclide migration through a clay liner are presented. Acidic uranium mill tailings solution from a Wyoming mill was percolated through a composite sediment called Morton Ranch Clay liner. These laboratory columns and subsequent sediment extraction data show: (1) As, Cr, Pb, Ag, Th and V migrate very slowly; (2) U, Cd, Ni, Zn, Fe, Mn and similar transition metals are initially immobilized during acid neutralization but later are remobilized as the tailings solution exhausts the clay liner&#x27;s acid buffering capacity. Such metals remain immobilized as long as the effluent pH remains above a pH value of 4 to 4.5, but they become mobile once the effluent pH drops below this range; and (3) fractions of the Se and Mo present in the influent tailings solution are very mobile. Possible controlling mechanisms for the pH-dependent immobilization-mobilization of the trace metals are discussed. More study is required to understand the controlling mechanisms for Se and Mo and Ra for which data were not successfully collected. Using several column lengths (from 4.5 to 65 cm) and pore volume residence times (from 0.8 to 40 days) we found no significant differences in contaminant migration rates or types and extent of controlling processes. Thus, we conclude that the laboratory results may be capable of extrapolation to actual disposal site conditions.
Date: April 1, 1983
Creator: Serne, R.J.; Peterson, S.R. & Gee, G.W.
Partner: UNT Libraries Government Documents Department

Laboratory evaluation of limestone and lime neutralization of acidic uranium mill tailings solution. Progress report

Description: Experiments were conducted to evaluate a two-step neutralization scheme for treatment of acidic uranium mill tailings solutions. Tailings solutions from the Lucky Mc Mill and Exxon Highland Mill, both in Wyoming, were neutralized with limestone, CaCO/sub 3/, to an intermediate pH of 4.0 or 5.0, followed by lime, Ca(OH)/sub 2/, neutralization to pH 7.3. The combination limestone/lime treatment methods, CaCO/sub 3/ neutralization to pH 4 followed by neutralization with Ca(OH)/sub 2/ to pH 7.3 resulted in the highest quality effluent solution with respect to EPA&#x27;s water quality guidelines. The combination method is the most cost-effective treatment procedure tested in our studies. Neutralization experiments to evaluate the optimum solution pH for contaminant removal were performed on the same two tailings solutions using only lime Ca(OH)/sub 2/ as the neutralizing agent. The data indicate solution neutralization above pH 7.3 does not significantly increase removal of pH dependent contaminants from solution. Column leaching experiments were performed on the neutralized sludge material (the precipitated solid material which forms as the acidic tailings solutions are neutralized to pH 4 or above). The sludges were contacted with laboratory prepared synthetic ground water until several effluent pore volumes were collected. Effluent solutions were analyzed for macro ions, trace metals and radionuclides in an effort to evaluate the long term effectiveness of attenuating contaminants in sludges formed during solution neutralization. Neutralized sludge leaching experiments indicate that Ca, Na, Mg, Se, Cl, and SO/sub 4/ are the only constituents which show solution concentrations significantly higher than the synthetic ground water in the early pore volumes of long-term leaching studies.
Date: February 1, 1984
Creator: Opitz, B.E.; Dodson, M.E. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

Predictive calculations to assess the long-term effect of cementitious materials on the pH and solubility of uranium(VI) in a shallow land disposal environment

Description: One proposed method of low-level radioactive waste (LLW) disposal is to mix the radioactive waste streams with cement, place the mixture in steel barrels, and dispose of the barrels in near-surface unsaturated sediments. Cement or concrete is frequently used in burial grounds, because cement porewaters are buffered at high pH values and lanthanides and actinides; are very insoluble in highly alkaline environments. Therefore, leaching of these contaminants from the combined cement/low-level radioactive waste streams will at least initially be retarded. The calculations performed in this study demonstrate that the pH of cement porewaters will be maintained at a value greater than 10 for 10,000 years under Hanford specific hydrogeochemical conditions. Ten thousand years is the period generally studied in longterm performance assessments per regulatory guidance. The concentrations of dissolved hexavalent uranium [U(VI)], the valence form of dissolved U usually present in oxidizing surface and groundwaters, are also constrained by the high pH and predicted solution compositions over the 10,000-year period, which is favorable from a long-term performance perspective.
Date: September 1, 1996
Creator: Criscenti, L.J.; Serne, R.J.; Krupka, K.M. & Wood, M.I.
Partner: UNT Libraries Government Documents Department

Radionuclide adsorption distribution coefficients measured in Hanford sediments for the low level waste performance assessment project

Description: Preliminary modeling efforts for the Hanford Site`s Low Level Waste-Performance Assessment (LLW PA) identified {sup 129}I, {sup 237}Np, {sup 79}Se, {sup 99}Tc, and {sup 234},{sup 235},{sup 238}U as posing the greatest potential health hazard. It was also determined that the outcome of these simulations was very sensitive to the parameter describing the extent to which radionuclides sorb to the subsurface matrix, i.e., the distribution coefficient (K{sub d}). The distribution coefficient is a ratio of the radionuclide concentration associated with the solid phase to that in the liquid phase. The objectives of this study were to (1) measure iodine, neptunium, technetium, and uranium K{sub d} values using laboratory conditions similar to those expected at the LLW PA disposal site, and (2) evaluate the effect of selected environmental parameters, such as pH, ionic strength, moisture concentration, and radio nuclide concentration, on K{sub d} values of selected radionuclides. It is the intent of these studies to develop technically defensible K{sub d} values for the PA. The approach taken throughout these studies was to measure the key radio nuclide K{sub d} values as a function of several environmental parameters likely to affect their values. Such an approach provides technical defensibility by identifying the mechanisms responsible for trends in K{sub d} values. Additionally, such studies provide valuable guidance regarding the range of K{sub d} values likely to be encountered in the proposed disposal site.
Date: August 1, 1996
Creator: Kaplan, D.I.; Serne, R.J. & Owen, A.T.
Partner: UNT Libraries Government Documents Department