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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

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

Leach test of cladding removal waste grout using Hanford groundwater

Description: This report describes laboratory experiments performed during 1986-1990 designed to produce empirical leach rate data for cladding removal waste (CRW) grout. At the completion of the laboratory work, funding was not available for report completion, and only now during final grout closeout activities is the report published. The leach rates serve as inputs to computer codes used in assessing the potential risk from the migration of waste species from disposed grout. This report discusses chemical analyses conducted on samples of CRW grout, and the results of geochemical computer code calculations that help identify mechanisms involved in the leaching process. The semi-infinite solid diffusion model was selected as the most representative model for describing leaching of grouts. The use of this model with empirically derived leach constants yields conservative predictions of waste release rates, provided no significant changes occur in the grout leach processes over long time periods. The test methods included three types of leach tests--the American Nuclear Society (ANS) 16.1 intermittent solution exchange test, a static leach test, and a once-through flow column test. The synthetic CRW used in the tests was prepared in five batches using simulated liquid waste spiked with several radionuclides: iodine ({sup 125}I), carbon ({sup 14}C), technetium ({sup 99}Tc), cesium ({sup 137}Cs), strontium ({sup 85}Sr), americium ({sup 241}Am), and plutonium ({sup 238}Pu). The grout was formed by mixing the simulated liquid waste with dry blend containing Type I and Type II Portland cement, class F fly ash, Indian Red Pottery clay, and calcium hydroxide. The mixture was allowed to set and cure at room temperature in closed containers for at least 46 days before it was tested.
Date: September 1, 1995
Creator: Serne, R.J.; Martin, W.J. & Legore, V.L.
Partner: UNT Libraries Government Documents Department

Solid waste leach characteristics and contaminant-sediment interactions Volume 2: Contaminant transport under unsaturated moisture contents

Description: The objectives of this report and subsequent volumes include describing progress on (1) development and optimization of experimental methods to quantify the release of contaminants from solid wastes and their subsequent interactions with unsaturated sediments and (2) the creation of empirical data that become input parameters to performance assessment (PA) analyses for future Hanford Site disposal units and baseline risk assessments for inactive and existing solid waste disposal units. For this report, efforts focused on developing methodologies to evaluate contaminant transport in Trench 8 (W-5 Burial Ground) sediments under unsaturated (vadose zone) conditions. To accomplish this task, a series of flow-through column tests were run using standard saturated column systems, Wierenga unsaturated column systems (both commercial and modified), and the Unsaturated Flow Apparatus (UFA). The reactants investigated were {sup 85}Sr, {sup 236}U, and {sup 238}U as reactive tracers, and tritium as a non-reactive tracer. Results indicate that for moderately unsaturated conditions (volumetric water contents >50 % of saturation), the Wierenga system performed reasonably well such that long water residence times (50-147 h) were achieved, and reasonably good steady-state flow conditions were maintained. The major drawbacks in using this system for reactive tracer work included (1) the inability to achieve reproducible and constant moisture content below 50% of saturation, (2) the four to six month time required to complete a single test, and (3) the propensity for mechanical failure resulting from laboratory power outages during the prolonged testing period.
Date: September 1, 1995
Creator: Lindenmeier, C.W.; Serne, R.J. & Conca, J.L.
Partner: UNT Libraries Government Documents Department

Final Report: Caustic Waste-Soil Weathering Reactions and Their Impacts on Trace Contaminant Migration and Sequestration

Description: The principal goal of this project was to assess the molecular nature and stability of radionuclide (137-Cs, 90-Sr, and 129-I) immobilization during weathering reactions in bulk Hanford sediments and their high surface area clay mineral constituents. We focused on the unique aqueous geochemical conditions that are representative of waste-impacted locations in the Hanford site vadose zone: high ionic strength, high pH and high Al concentrations. The specific objectives of the work were to (i) measure the coupling of clay mineral weathering and contaminant uptake kinetics of Cs+, Sr2+ and I-; (ii) determine the molecular structure of contaminant binding sites and their change with weathering time during and after exposure to synthetic tank waste leachate (STWL); (iii) establish the stability of neoformed weathering products and their sequestered contaminants upon exposure of the solids to more “natural” soil solutions (i.e., after removal of the caustic waste source); and (iv) integrate macroscopic, microscopic and spectroscopic data to distinguish labile from non-labile contaminant binding environments, including their dependence on system composition and weathering time. During this funding period, we completed a large set of bench-scale collaborative experiments and product characterization aimed at elucidating the coupling between mineral transformation reactions and contaminant sequestration/stabilization. Our experiments included three representative Hanford sediments: course and fine sediments collected from the Hanford Formation and Ringold Silt, in addition to investigations with specimen clay minerals illite, vermiculite, smectite and kaolinite. These experiments combined macroscopic measurements of element release, contaminant uptake and subsequent neoformed mineral dissolution behavior, with detailed studies of solid phase products using SEM and TEM microscopy, NMR, XAS and FTIR spectroscopy. Our studies have shown direct coupling between mineral transformation reactions and contaminant sequestration/stabilization.
Date: December 11, 2006
Creator: O'Day, Peggy A.; Chorover, J.; Mueller, K.T. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

Effects on radionuclide concentrations by cement/ground-water interactions in support of performance assessment of low-level radioactive waste disposal facilities

Description: The US Nuclear Regulatory Commission is developing a technical position document that provides guidance regarding the performance assessment of low-level radioactive waste disposal facilities. This guidance considers the effects that the chemistry of the vault disposal system may have on radionuclide release. The geochemistry of pore waters buffered by cementitious materials in the disposal system will be different from the local ground water. Therefore, the cement-buffered environment needs to be considered within the source term calculations if credit is taken for solubility limits and/or sorption of dissolved radionuclides within disposal units. A literature review was conducted on methods to model pore-water compositions resulting from reactions with cement, experimental studies of cement/water systems, natural analogue studies of cement and concrete, and radionuclide solubilities experimentally determined in cement pore waters. Based on this review, geochemical modeling was used to calculate maximum concentrations for americium, neptunium, nickel, plutonium, radium, strontium, thorium, and uranium for pore-water compositions buffered by cement and local ground-water. Another literature review was completed on radionuclide sorption behavior onto fresh cement/concrete where the pore water pH will be greater than or equal 10. Based on this review, a database was developed of preferred minimum distribution coefficient values for these radionuclides in cement/concrete environments.
Date: May 1, 1998
Creator: Krupka, K. M. & Serne, R. J.
Partner: UNT Libraries Government Documents Department

Mineral surface processes responsible for the decreased retardation (or enhanced mobilization) of {sup 137}Cs from HLW tank discharges. 1998 annual progress report

Description: 'Cesium (137) is a major component of high level weapons waste. At Hanford, single shell tanks (SST''s) with high level wastes (HLW) have leaked supernate containing over 10{sup 6} Ci of 137 Cs and other co-contaminants into the vadose zone. In select locations, 137 Cs has migrated further than expected from retardation experiments and performance assessment calculations. Deep 137 Cs migration has been observed beneath the SX tank farm at Hanford with REDOX wastes as the carrier causing regulatory and stakeholder concern. The causes for expedited migration are unclear. This research is investigating how the sorption chemistry of Cs on Hanford vadose zone sediments changes after contact with solutions characteristic of HLW. The central scientific hypothesis is that the high Na concentration of HLW will suppress surface-exchange reactions of Cs, except those to highly-selective frayed edge sites (FES) of the micaceous fraction. The authors further speculate that the concentrations, ion selectivity, and structural aspects of the FES will change after contact with HLW and that these changes will be manifest in the macroscopic sorption behavior of Cs. The authors believe that migration predictions of Cs can be improved substantially if such changes are understood and quantified. The research has three objectives: (1.) identify how the multi-component surface exchange behavior of Cs on Hanford sediments changes after contact with HLW simulants that span a range of relevant chemical (Na, OH, Al, K) and temperature conditions (23-80 C); (2) reconcile changes in sorption chemistry with microscopic and molecular changes in site distribution, chemistry, mineralogy, and surface structure of the micaceous fraction; (3) integrate mass-action-solution exchange measurements with changes in the structure/site distribution of the micaceous fraction to yield a multicomponent exchange model relevant to high ionic strength and hydroxide for prediction of environmental Cs sorption.'
Date: June 1, 1998
Creator: Zachara, J.M.; Ellis, P.D.; Serne, R.J. & Bertsch, P.M.
Partner: UNT Libraries Government Documents Department

Coupling Sorption to Soil Weathering During Reactive Transport: Impacts of Mineral Transformation and Sorbent Aging on Contaminant Speciation and Mobility

Description: This project aimed for a predictive-mechanistic understanding of the coupling between mineral weathering and contaminant (Cs, Sr, I) transport/fate in caustic waste-impacted sediments. Based on our prior studies of model clay mineral systems, we postulated that contaminant uptake to Hanford sediments would reflect concurrent adsorption and co-precipitation effects. Our specific objectives were: (1) to assess the molecular-scale mechanisms responsible for time-dependent sequestration of contaminants (Cs, Sr and I) during penetration of waste-induced weathering fronts; (2) to determine the rate and extent of contaminant release from the sorbed state; (3) to develop a reactive transport model based on molecular mechanisms and macroscopic flow experiments [(1) and (2)] that simulates adsorption, aging, and desorption dynamics. Progress toward achieving each of these objectives is discussed below. We observed unique molecular mechanisms for sequestration of Sr, Cs and I during native silicate weathering in caustic waste. Product solids, which included poorly crystalline aluminosilicates and well-crystallized zeolites and feldspathoids, accumulate contaminant species during crystal growth.
Date: October 30, 2009
Creator: Chorover, J.; Mueller, K. T.; O'Day, P. A.; Serne, R. J. & Steefel, C. I.
Partner: UNT Libraries Government Documents Department

Performance assessment for the disposal of low-level waste in the 200 West Area Burial Grounds

Description: This document reports the findings of a performance assessment (PA) analysis for the disposal of solid low-level radioactive waste (LLW) in the 200 West Area Low-Level Waste Burial Grounds (LLBG) in the northwest corner of the 200 West Area of the Hanford Site. This PA analysis is required by US Department of Energy (DOE) Order 5820.2A (DOE 1988a) to demonstrate that a given disposal practice is in compliance with a set of performance objectives quantified in the order. These performance objectives are applicable to the disposal of DOE-generated LLW at any DOE-operated site after the finalization of the order in September 1988. At the Hanford Site, DOE, Richland Operations Office (RL) has issued a site-specific supplement to DOE Order 5820.2A, DOE-RL 5820.2A (DOE 1993), which provides additiona I ce objectives that must be satisfied.
Date: June 1, 1995
Creator: Wood, M.I.; Khaleel, R.; Rittmann, P.D.; Lu, A.H.; Finfrock, S.H.; DeLorenzo, T.H. et al.
Partner: UNT Libraries Government Documents Department

Long-term-consequence analysis of no action alternative 2

Description: This report is a supplement to the Waste Isolation Pilot Plant (WIPP) Disposal-Phase Supplemental Environmental Impact Statement. Data and information is described which pertains to estimated impacts from postulated long-term release of radionuclides and hazardous constituents from alpha-bearing wastes stored at major generator/storage sites after loss of institutional control (no action alternative 2). Under this alternative, wastes would remain at the generator sites and not be emplaced at WIPP.
Date: July 1, 1996
Creator: Buck, J.W.; Bagaasen, L.M.; Staven, L.H. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

Characterization strategy report for the criticality safety issue

Description: High-level radioactive waste from nuclear fuels processing is stored in underground waste storage tanks located in the tank farms on the Hanford Site. Waste in tank storage contains low concentrations of fissile isotopes, primarily U-235 and Pu-239. The composition and the distribution of the waste components within the storage environment is highly complex and not subject to easy investigation. An important safety concern is the preclusion of a self-sustaining neutron chain reaction, also known as a nuclear criticality. A thorough technical evaluation of processes, phenomena, and conditions is required to make sure that subcriticality will be ensured for both current and future tank operations. Subcriticality limits must be based on considerations of tank processes and take into account all chemical and geometrical phenomena that are occurring in the tanks. The important chemical and physical phenomena are those capable of influencing the mixing of fissile material and neutron absorbers such that the degree of subcriticality could be adversely impacted. This report describes a logical approach to resolving the criticality safety issues in the Hanford waste tanks. The approach uses a structured logic diagram (SLD) to identify the characterization needed to quantify risk. The scope of this section of the report is limited to those branches of logic needed to quantify the risk associated with a criticality event occurring. The process is linked to a conceptual model that depicts key modes of failure which are linked to the SLD. Data that are needed include adequate knowledge of the chemical and geometric form of the materials of interest. This information is used to determine how much energy the waste would release in the various domains of the tank, the toxicity of the region associated with a criticality event, and the probability of the initiating criticality event.
Date: June 1, 1997
Creator: Doherty, A.L.; Doctor, P.G.; Felmy, A.R.; Prichard, A.W. & Serne, R.J.
Partner: UNT Libraries Government Documents Department

Characterization of radionuclide-chelating agent complexes found in low-level radioactive decontamination waste. Literature review

Description: The US Nuclear Regulatory Commission is responsible for regulating the safe land disposal of low-level radioactive wastes that may contain organic chelating agents. Such agents include ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), picolinic acid, oxalic acid, and citric acid, and can form radionuclide-chelate complexes that may enhance the migration of radionuclides from disposal sites. Data from the available literature indicate that chelates can leach from solidified decontamination wastes in moderate concentration (1--100 ppm) and can potentially complex certain radionuclides in the leachates. In general it appears that both EDTA and DTPA have the potential to mobilize radionuclides from waste disposal sites because such chelates can leach in moderate concentration, form strong radionuclide-chelate complexes, and can be recalcitrant to biodegradation. It also appears that oxalic acid and citric acid will not greatly enhance the mobility of radionuclides from waste disposal sites because these chelates do not appear to leach in high concentration, tend to form relatively weak radionuclide-chelate complexes, and can be readily biodegraded. In the case of picolinic acid, insufficient data are available on adsorption, complexation of key radionuclides (such as the actinides), and biodegradation to make definitive predictions, although the available data indicate that picolinic acid can chelate certain radionuclides in the leachates.
Date: March 1, 1996
Creator: Serne, R. J.; Felmy, A. R.; Cantrell, K. J.; Krupka, K. M.; Campbell, J. A.; Bolton, H., Jr. et al.
Partner: UNT Libraries Government Documents Department

Spent nuclear fuel as a waste form for geologic disposal: Assessment and recommendations on data and modeling needs

Description: This study assesses the status of knowledge pertinent to evaluating the behavior of spent nuclear fuel as a waste form in geologic disposal systems and provides background information that can be used by the DOE to address the information needs that pertain to compliance with applicable standards and regulations. To achieve this objective, applicable federal regulations were reviewed, expected disposal environments were described, the status of spent-fuel modeling was summarized, and information regarding the characteristics and behavior of spent fuel was compiled. This compiled information was then evaluated from a performance modeling perspective to identify further information needs. A number of recommendations were made concerning information still needed to enhance understanding of spent-fuel behavior as a waste form in geologic repositories. 335 refs., 22 figs., 44 tabs.
Date: September 1, 1987
Creator: Van Luik, A.E.; Apted, M.J.; Bailey, W.J.; Haberman, J.H.; Shade, J.S.; Guenther, R.E. et al.
Partner: UNT Libraries Government Documents Department