Underground Waste Storage Tanks Research Articles

Long-Term Evolution of Corrosion Potential of Carbon Steel in Alkaline Radioactive Waste Environments

The long-term shifts of corrosion potential are important in predicting the likelihood of localized corrosion and stress corrosion cracking (SCC) of carbon steel used for storing radioactive wastes in underground storage tanks. Although considerable work has been done in understanding the passivity and corrosion potential of steel in various electrolytes, an important aspect of the current work is in assessing the effects of multiyear exposures of steel in waste simulants and their effects on corrosion potential. It is shown that SCC susceptibility of steel in nitrate increases at the long-term corrosion potential in solutions without organics (either by applying that potential or letting the corrosion potential increase over time). The long-term increase in corrosion potential results principally from a decrease in the passive current density with time of exposure. The present work shows that such a reduction in passive current density is accompanied by changes in the semi-conductive properties of the passive film, which itself may be a result of changes in stoichiometry of the film over time. Nitrite reduction is the most likely cathodic reaction with a small contribution from oxygen reduction. However, the presence of organic species in the environment can result in additional anodic reactions that may decrease the corrosion potential.

RESULTS OF EXTERNAL TECHNICAL REVIEWS OF SITE MODELING EFFORTS THAT SUPPORT SYSTEM PLANS

An External Technical Review (ETR) team evaluated the system-level modeling and simulation tools in support of Savannah River Site and Office of River Protection liquid waste processing and disposal systems. The reviews focused on the following primary areas: software and modeling tools, capability to model needed facilities and operations, rate at which predictions are performed, and need for additional tools. The Liquid Waste Disposition Systems at these sites are highly integrated operations that involve safely storing liquid waste in underground storage tanks; removing, treating, and disposing low-activity fraction on-site; vitrifying high-level waste; and storing the vitrified waste until permanent disposition at a Federal Repository. The purpose of the ETR team was to evaluate the current process simulation tools that support the planning basis for life cycle liquid waste disposition system plans. These plans establish a base for processing the constituents of liquid waste systems to the end of the program mission. Observations and recommendations were made for each of the review areas. In general, tools appear to provide reasonable estimates for their intended purposes; however, additional functionality and new tools are needed, as well as greater flexibility and improved performance in producing estimates for planning purposes.

Maximizing Production Capacity from an Ultrafiltration Process at the Hanford Department of Energy Waste Treatment Facility

The Department of Energy has contracted Bechtel National, Inc. to design, construct, and commission a Waste Treatment and Immobilization Plant (WTP) to treat radioactive slurry currently stored in underground waste storage tanks. A critical element of the waste treatment capacity for the WTP is the proper operation of an ultrafiltration process (UFP). The UFP separates supernate solution from radioactive solids. The solution and solid phases are separately immobilized. An oversight review of the UFP design and operation has identified several methods to improve the capacity of the ultrafiltration process, which will also improve the capacity of the WTP. Areas explored were the basis of design, an analysis of the WTP capacity, process chemistry within the UFP, and UFP process control. This article discusses some of the findings of this oversight review in terms of sodium and solid production, which supports the treatment of low activity waste (LAW) associated with the facility, and solid production, which supports the treatment of high level waste (HLW) associated with the facility.

Colloid Formation in Hanford Sediments Reacted with Simulated Tank Waste

Solutions of high pH, ionic strength, and aluminum concentration have leaked into the subsurface from underground waste storage tanks atthe Hanford Reservation in Washington State. Here, we test the hypothesis that these waste solutions alter and dissolve the native minerals present in the sediments and that colloidal (diameter < 2 microm) feldspathoids form. We reacted Hanford sediments with simulated solutions representative of Hanford waste tanks. The solutions consisted of 1.4 or 2.8 mol/kg NaOH, 0.125 or 0.25 mol/kg NaAlO4, and 3.7 mol/kg NaNO3 and were contacted with the sediments for a period of 25 or 40 days at 50 degrees C. The colloidal size fraction was separated from the sediments and characterized in terms of mineralogy, morphology, chemical composition, and electrophoretic mobility. Upon reaction with tank waste solutions, native minerals released Si and other elements into the solution phase. This Si precipitated with the Al present in the waste solutions to form secondary minerals, identified as the feldspathoids cancrinite and sodalite. The solution phase was modeled with the chemical equilibrium model GMIN for solution speciation and saturation indices with respect to sodalite and cancrinite. The amount of colloidal material in the sediments increased upon reaction with waste solutions. At the natural pH found in Hanford sediments (pH 8) the newly formed minerals are negatively charged, similar to the unreacted colloidal material present in the sediments. The formation of colloidal material in Hanford sediments upon reaction with tank waste solutions is an important aspect to consider in the characterization of Hanford tank leaks and may affect the fate of hazardous radionuclides present in the tank waste.

A Cost Comparison of Organic versus Inorganic Ion Exchange Resin for Remediation of High-Level Waste

Ion exchange (IX) can be used to aid in the remediation of underground storage tank (UST) radioactive waste at the U.S. Department of Energy's Hanford site in the state of Washington. In particular, IX can be used to concentrate the radionuclides in liquid-based waste prior to immobilization for final disposal. Concentration of the radionuclides can significantly reduce the final immobilized high-level waste volume and consequent overall remediation cost. Organic and inorganic IX resins each have unique advantages and disadvantages regarding the remediation process. This study presents a comparison of the remediation cost for UST waste at Hanford for a phenol-formaldehyde type organic resin versus crystalline silico-titanate inorganic resin. It was determined that with optimum processing conditions such as waste blending and sludge washing, remediation with the inorganic resin would be less expensive than the organic resin. Assuming baseline remediation conditions, the use of inorganic rather than organic IX resin for UST remediation at Hanford can save approximately $383 million. A limited sensitivity analysis was performed as pan of this study and is reported in the following. © 1999 John Wiley & Sons, Inc.

A cost study for enhanced sludge washing of high‐level radioactive waste at the U.S. Department of energy Hanford Site

AbstractEnhanced Sludge Washing (ESW) with caustic has the potential to significantly reduce the amount of sludge‐based underground storage tank (UST) high‐level radioactive waste at the Hanford Site. The alternative to ESW is a simple sludge wash, a process that does not take advantege of recent dissolution development efforts. During the past several years, studies have been conducted to determine the remediation cost savings derived from the development and deployment of ESW. The tank waste inventory and ESW process performance continues to be revised as waste characterization, and ESW development efforts advance. This study provides a new cost savings estimate based upon the most recent waste inventory and ESW process performance revisions, an estimate of the associated cost savings uncertainty, and an estimate of the rate of return (ROR) on the investment in technology development. The revised remediation cost savings estimate due to ESW of all UST waste at Hanford is $4.8 billion ± $0.7 billion within 95 percent confidence in 1998 dollars. The ROR on investment was estimated to range from 100 percent to 130 percent. A sensitivity analysis indicated that it would be difficult to imagine a remediation scenario for which ESW did not yield a significant remediation cost savings and ROR.

Colloidal Agglomerates in Tank Sludge and Their Impact on Waste Processing

AbstractDisposal of millions of gallons of existing radioactive wastes in underground storage tanks is a major remediation activity for the United States Department of Energy. These wastes include a substantial volume of insoluble sludges consisting of submicron colloidal particles. Processing these sludges under the proposed processing conditions presents unique challenges in retrieval transport, separation, and solidification of these waste streams. Depending on processing conditions, these colloidal particles can form agglomerated networks having high viscosities that could clog transfer lines or produce high volumes of low-density sediments that interfere with solid-liquid separations. Under different conditions, these particles can be dispersed to form very fine suspended particles that do not settle. Given the wide range of waste chemistries present at Department of Energy sites, it is impractical to measure the properties of all treatment procedures. Under the current research activities, the underlying principles of colloid chemistry and physics are being studied to predict and eventually control the physical properties of sludge suspensions and sediment layers in tank wastes and other waste processing streams. Proposed tank processing strategies include retrieval transport, and solid-liquid separations in basic (pH 10 to 14), high ionic strength (0.1 to 1.0 M) salt solutions. The effect of salt concentration, ionic strength, and salt composition on the physical properties such as viscosity, agglomerate size, and sedimentation of model suspensions containing mixtures of one or two of the major components found in actual wastes have been measured to understand how agglomeration influences processing. Property models developed from theory and experiment on these simple suspensions are then applied to explain the results obtained on actual wastes.

CESIUM REMOVAL FROM HIGH-pH, HIGH-SALT WASTEWATER USING CRYSTALLINE SILICOTITANATE SORBENT

ABSTRACT Treatment and disposal options for Department of Energy (DOE) underground storage tank waste at Hanford, Savannah River, Idaho National Engineering and Environmental Laboratory (INEEL), and Oak Ridge National Laboratory (ORNL) are limited by high gamma radiation fields that are produced by high concentrations of cesium in the waste. Treatment methods are needed to remove the cesium from the liquid waste and thus concentrate the cesium into high-activity, remote-handled waste forms. The treated liquids could then be processed and disposed of by more cost-effective means with less radiation exposure to workers. A full-scale demonstration of one cesium removal technology has been conducted at ORNL. This demonstration utilizes a modular, mobile ion-exchange system and existing facilities for the off-gas system, secondary containment, and utilities. The ion-exchange material, crystalline silicotitanate (CST), was chosen on the basis of its effectiveness in laboratory tests. The CST, which was developed through a Cooperative Research and Development Agreement between DOE and private industry, has several advantages over current organic ion-exchange technologies. These advantages include (1) the ability to remove cesium in the presence of high concentrations of potassium, (2) a high affinity for cesium in both alkaline and acidic conditions, (3) physical stability over wide alkaline and acidic ranges, and (4) the elimination of large volumes of secondary waste required for regeneration of organic ion exchangers. Approximately 116,000 L of supernate was processed during the demonstration with ∼1,142 Ci of137CS removed from the supernate and loaded onto 265L (70 gal) of sorbent. The supernate processed had a high salt content, about 4 M NaNO3, and a pH of 12 to 13. This paper discusses the results of the full-scale demonstration and compares these results with data from the laboratory tests.

Performance Evaluation of a Thermal Desorption/Gas Chromatographic/ Mass Spectrometric Method for the Characterization of Waste Tank Headspace Samples

A thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) method was validated for the determination of volatile organic compounds collected on carbonaceous triple sorbent traps and applied to characterize samples of headspace gases collected from underground nuclear waste storage tanks at the U.S. Department of Energy's Hanford site, in Richland, WA. Method validation used vapor-phase standards generated from 25 target analytes, including alkanes, alkyl alcohols, alkyl ketones, alkylated aromatics, and alkyl nitriles. The target analytes represent a group of compounds identified in one of the most problematic tanks. TD/GC/MS was carried out with Hewlett-Packard 5972A or 5995 GC/MS systems with modified injectors. Performance was characterized based on desorption efficiency, reproducibility, stability, and linearity of the calibration, method detection limits, pre-analytical holding time, and quality control limits for sur rogate standard recoveries. Desorption efficiencies were all greater tha...

Analysis of Underground Storage Tank Waste Simulants by Fourier Transform Infrared Photoacoustic Spectroscopy

Underground storage tank waste sludge from nuclear fuel processes is difficult to analyze because of the extreme heterogeneity, chemical reactivity, and radioactivity of the waste. Conventional methods of analysis typically require extensive sample handling procedures either to thin the sample or to separate components prior to analysis. These procedures are time consuming, require radiation containment cells, and increase the risk of radiation exposure to lab personnel as a result of the extensive handling. In this paper a method utilizing Fourier transform infrared photoacoustic spectroscopy to analyze hazardous underground storage tank waste with a minimal amount of sample and sample handling is discussed. The method was developed with the use of waste tank simulants that were obtained from the Westinghouse Hanford Company. Emphasis was placed on the determination of disodium nickel ferrocyanide, sodium nitrate, and sodium nitrite because of the concern for the potential of exothermic reactions occurring between oxidizers and ferrocyanide-containing compounds. This method also allows for the analysis of other ions of interest in waste processes such as sodium sulfate. A simple sample preparation method is also discussed which uses freeze drying to remove water from the simulants while maintaining a uniform sample for analysis.

Spin‐off applications of recyclable phase transformation (RPT) gel technology ranging from soil cleanup to pharmaceutical separations

Federal Facilities Environmental JournalVolume 6, Issue 2 p. 121-131 Article Spin-off applications of recyclable phase transformation (RPT) gel technology ranging from soil cleanup to pharmaceutical separations Donald H. Alexander, Donald H. Alexander Dr. Donald H. Alexander is Program Manager for Underground Storage Tank Waste, Department of Energy, Richland Operations.Search for more papers by this authorNabil Morcos, Nabil Morcos Dr. Nabil Morcos is Staff Scientist, Chemistry Division, Lockheed/Idaho National Engineering Laboratory.Search for more papers by this authorR. Soundararajan, R. Soundararajan Dr. R. Soundararajan is President, Sudharsan International, Inc., and a senior advisor to the U.S. EPA and Department of Energy.Search for more papers by this author Donald H. Alexander, Donald H. Alexander Dr. Donald H. Alexander is Program Manager for Underground Storage Tank Waste, Department of Energy, Richland Operations.Search for more papers by this authorNabil Morcos, Nabil Morcos Dr. Nabil Morcos is Staff Scientist, Chemistry Division, Lockheed/Idaho National Engineering Laboratory.Search for more papers by this authorR. Soundararajan, R. Soundararajan Dr. R. Soundararajan is President, Sudharsan International, Inc., and a senior advisor to the U.S. EPA and Department of Energy.Search for more papers by this author First published: Summer 1995 https://doi.org/10.1002/ffej.3330060213 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume6, Issue2Summer 1995Pages 121-131 RelatedInformation

A relative risk index for prioritization of inactive underground storage tanks

A relative risk index (RRI) is proposed for ranking the relative health risk potential of mixed liquid wastes in underground storage tanks (USTs) that are scheduled for remedial action. The RRI is defined as the number of reference volumes in the liquid volume of a tank. A reference volume is the amount of liquid a person must ingest over a lifetime to incur either a 10 −6 lifetime cancer risk or a noncarcinogenic reference dose level exceeding one. The RRI accounts for contaminant concentration, contaminant toxicity, and the tank's liquid volume. The higher the number of reference volumes in a tank, the higher the relative risk potential of the tank. The RRI may be incorporated into any of the existing hazard ranking systems used for UST remediation.

Behavior of Concrete as a Barrier Material for Nuclear Waste Disposal

SummaryThe foundation necessary for a constitutive model to simulate the response of concrete at elevated temperature has been presented. A model including temperature dependent creep, material property degradation, and cracking is needed to evaluate the long term functional requirements of concrete as a barrier material for nuclear waste disposal. Since the stress due to thermal load is proportional to the modulus, the degradation of the modulus with time even at constant elevated temperatures requires continual redistribution of load. Furthermore, since this degradation is not recoverable, the response of the material at elevated temperatures exhibits a complex dependence not only on the temperature distribution, but on the prior thermal history of the structure.This constitutive model for the response of concrete at elevated temperatures has been implemented into an implicit, finite element program called ANACAP [8]. Because of the direct coupling with temperature, both through thermal loads and material property dependency, ANACAP also contains a heat transfer module that includes thermal effects due to fluid flow and moving material boundaries. This program has been applied to problems involving underground waste storage tanks and grout vaults at the DOE Hanford site in Richland, Washington.