Lockheed Martin Energy Research Research Articles

TREATMENT OF LOW-LEVEL RADIOACTIVE WASTEWATERS WITH IONSIV™ IE-911 AND CHABAZITE ZEOLITE

Natural chabazite zeolite was selected as the baseline treatment technology for the removal of the fission products, 90Sr and 137Cs, from near-neutral-pH process wastewater and groundwater. The sorbent Ionsiv™ IE-911, a crystalline silicotitanate commercially developed and manufactured by UOP, was recently tested for this application and found to compare extremely well against the baseline material. This paper presents and compares the results of similar batch and column tests performed using both materials, and summarizes the physical and chemical characteristics of thesorbents. *Managed by Lockheed Martin Energy Research Corp. for the U.S. Department of Energy under contract DE-AC05-96OR22464.

ANALYSIS OF BREAKTHROUGH PROFILES BASED ON GAMMA-RAY EMISSION ALONG LOADED PACKED BED COLUMNS: COMPARATIVE EVALUATION OF IONSIV® IE-911 AND CHABAZITE ZEOLITE FOR THE REMOVAL OF RADIOSTRONTIUM AND CESIUM FROM GROUNDWATER

A gamma counting system has been assembled that can profile the breakthrough fronts of gamma-emitting radioisotopes longitudinally along a loaded column. This profiling technique has been particularly useful in column studies such as those performed with IONSIV® IE-911, a crystalline silicotitanate (CST) manufactured by UOP, in which long operating times are required to observe cesium effluent breakthrough at the low inlet (10−4 ppm) concentrations studied here. The length of the mass transfer zone and extent of column saturation can be detected by viewing the relative emission of gamma emitters along the length of the column. In this study, gamma scans were used to analyze loaded CST and zeolite columns used in the treatment of process wastewater simulant and actual groundwater. The longitudinal gamma scans for both 90Sr and 137Cs conformed with breakthrough results based on column effluent activity. Although not obvious from data obtained by monitoring effluent activity, the gamma scans indicated that both cesium and strontium in the saturated zone of the CST column are slowly displaced by the higher levels of groundwater cations and are then resorbed further down the column. This displacement phenomenon identified by gamma scans was also noted for the zeolite column, in which both the gamma scan and column effluent data exhibited radionuclide displacement. The gamma emission intensities from the CST column runs are used to quantitate and compare the distribution coefficient and loading capacity of 137Cs on CST versus zeolite. Managed by Lockheed Martin Energy Research Corp. for the U.S. Department of Energy under contract DE-AC05-96OR22464.

Effect of electrode configurations on phase equilibria with applied electric fields1This research was supported by the Environmental Management Science Program, Office of Environmental Management, US Department of Energy, under contract DEAC05-96OR22464 with Lockheed Martin Energy Research Corporation.1

Applying an electric field to some boiling binary mixtures has been shown experimentally to increase the separation factor by as much as 10%. In this work, an electric field was applied across the interface of boiling mixtures of 2-propanol–water via electrodes located in the vapor and the liquid. The shape and separation of the electrodes and the strength and polarity of the electric field were altered to investigate their effect on the vapor mole fraction, the current, and the vapor temperature. The results show that greater voltage differences, in the absence of excessive electrical current, lead to higher concentrations of 2-propanol in the vapor. However, it was found that varying the electrode separation at a given potential difference, and thus the electric field strength, has little effect on the vapor composition. The effects of the applied potential difference are reduced with elevated current and under conditions where liquid dynamics such as dripping, splashing, or jetting provide an opportunity for charge to be transferred between the electrode in the vapor and the liquid. It is also shown that directing the electric field from the vapor to the liquid produces a lower current, and the effect on the composition is larger. These findings, in combination with calculations of the interface charge density, suggest that improvements in the separation efficiency achieved by an applied potential difference are not due to effects of the electric field in the bulk fluids, but rather are induced by charge accumulation at the vapor–liquid interface.

PURIFICATION OF THORIUM FROM URANIUM-233 PROCESS RESIDUE

ABSTRACT Thorium-229 can be used to produce 213Bi. Researchers in phase I human trials are investigating the use of antibodies labeled with 213Bi for selectively destroying leukemia cells. Other types of cancer may potentially be treated using similar approaches. Crude 229Th was liberated from Rachig rings by sonication in 7.5 M HNO3 followed by filtration. Contaminants, included significant levels of uranium, a number of other metals, and radiolytic by-products of di-(2-butyl) phosphoric acid extractant (which was used in the original separation of 233U from thorium). Thorium was selectively retained on Reillex HPQ anion-exchange resin from 7.5 M HNO3 at 65°C, where U(VI), Ac(III), Fe(III), Al(III); Ra(II), and Pb(II) were eluted. Thorium and uranium isotherms on Reillex HPQ are reported. The thorium was then easily eluted from the bed with 0.1 M HNO3. To overcome mass transfer limitations of the resin, the separation was conducted at 65°C. The resin stood up well to use over several campaigns. Other researchers have reported that HPQ has excellent radiological and chemical stability. The eluted thorium was further purified by hydroxide precipitation from the organic contaminants. This process yielded 65 mCi of 229Th. * Managed by Lockheed Martin Energy Research Corp. for the u.s. Department of Energy under contract DE-AC05-96OR22464.

CAUSTIC LEACHING OF HIGH-LEVEL RADIOACTIVE TANK SLUDGE: A CRITICAL LITERATURE REVIEW

ABSTRACT The Department of Energy (DOE) must treat and safely dispose of its radioactive tank contents, which can be separated into high-level waste (HLW) and low-level waste (LLW) fractions. Since the unit costs of treatment and disposal are much higher for HLW than for LLW, technologies to reduce the amount of HLW are being developed. A key process currently being studied to reduce the volume of HLW sludges is called enhanced sludge washing (ESW). This process removes, by water washes, soluble constituents such as sodium salts, and the washed sludge is then leached with 2–3 M NaOH at 60–100°C to remove nonradioactive metals such as aluminum. The remaining solids are considered to be HLW while the solutions are LLW after radionuclides such as 137Cs have been removed. Results of bench-scale tests have shown that the ESW will probably remove the required amounts of inert constituents. While both experimental and theoretical results have shown that leaching efficiency increases as the time and temperature of the leach are increased, increases in the caustic concentration above 2–3 M will only marginally improve the leach factors. However, these tests were not designed to validate the assumption that the caustic used in the ESW process will generate only a small increase (10 Mkg) in the amount of LLW; instead, the test conditions were selected to maximize leaching in a short period and used more water and caustic than is planned during full-scale operations. Even though calculations indicate that the estimate for the amount of LLW generated by the ESW process appears to be reasonable, a detailed study of the amount of LLW from the ESW process is still required. If the LLW analysis indicates that sodium management is critical, then a more comprehensive evaluation of the clean salt process or caustic recycle would be needed. Finally, experimental and theoretical studies have clearly demonstrated the need for the control of solids formation during and after leaching. * Managed by Lockheed Martin Energy Research Corp. for the U.S. Department of Energy under contract DE-AC05-96OR22464.

URANIUM EXTRACTION SELECTIVITIES OF DIBUTYL CARBITOL AND TRIBUTYL PHOSPHATE IN THE SYSTEM UO2(NO3)2-HNO3H2O-Al(NO3)3-SOLVENT*

ABSTRACT Historically, both the BUTEX (dibutyl carbitol-based) and PUREX (tributyl phosphate-based) processes have been used for uranium recovery and purification. Currently, BUTEX- and PUREX-type extraction processes are being used in series for recovery of isotopically enriched uranium at the Oak Ridge Y-12 Plant. The use of two solvents is predicated on the differing selectivities of each with regard to the contaminant elements present in the uranium source stream. As part of efforts to streamline plant operations in response to decreasing throughput requirements, the Y-12 Development Division is evaluating options for converting the existing two-solvent operation to a single-solvent process. At the request of the Y-12 Development Division, the Robotics and Process Division at the Oak Ridge National Laboratory has undertaken evaluation of solvents for use in a single-solvent recovery process. Initial efforts have been directed toward development of a single-solvent, dibutyl carbitol-or tributyl phosphate-based process that produces a product with purity equal to or exceeding what is currently obtained in the two-cycle, two-solvent operation. The test effort has involved both laboratory equilibrium determinations and engineering-scale process demonstrations in multistage flowsheets using centrifugal solvent extraction contactors. Excellent uranium recovery results have been obtained from both dibutyl carbitol- and tributyl phosphate-based solvent extraction flowsheets. Contaminant rejection performance by the two solvents is similar for many of the elements considered. Extraction of some contaminant elements by tributyl phosphate is significant enough to conclude that the solvent is not as selective for uranium as is dibutyl carbitol. This determination does not necessarily eliminate tributyl phosphate from consideration for use in a single-solvent process but does indicate a need for effective scrubbing of contaminants from uranium-loaded tributyl phosphate, possibly by partial reflux of the purified, aqueous uranyl nitrate product solution. *Research sponsored by the Oak Ridge Y-12 Development Division for the U.S. Department of Energy under Contract No. DE-AC05-96OR22464 with Lockheed Martin Energy Systems. ** Managed by Lockheed Martin Energy Research Corp. for the U.S. Department of Energy.

MAGNETIC-SEEDING FILTRATION*

ABSTRACT Magnetic-seeding filtration consists of two steps: heterogeneous particle flocculation of magnetic and nonmagnetic particles in a stirred tank and high-gradient magnetic filtration (HGMF). The effects of various parameters affecting magnetic-seeding filtration are theoretically and experimentally investigated. A trajectory model that includes hydrodynamic resistance, van der Waals, and electrostatic forces is developed to calculate the flocculation frequency in a turbulent-shear regime. Fractal dimension is introduced to simulate the open structure of aggregates. A magnetic-filtration model that consists of trajectory analysis, a particle build-up model, a breakthrough model, and a bivariate population-balance model is developed to predict the breakthrough curve of magnetic-seeding filtration. A good agreement between modeling results and experimental data is obtained. The results show that the model developed in this study can be used to predict the performance of magnetic-seeding filtration without using empirical coefficients or fitting parameters. * This research was supported by the Efficient Separations and Processing Crosscutting Program, Office of Environmental Management, U.S. Department of Energy, under contract DE-AC05-96OR22464 with Lockheed Martin Energy Research Corp. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. government purposes.

DISPLACEMENT OF A HYDROCARBON OIL FROM A METAL SURFACE USING A SURFACTANT SOLUTION*

ABSTRACT Separation of oils from solid surfaces is important in cleaning and degreasing operations. Water and oils are immiscible requiring the use of an additive which is miscible with water yet has an affinity for oils. Surface active agents, known as surfactants, have this property, being miscible with water while having an affinity for hydrocarbons. In some cases, surfactant solutions displace oils from a solid surface (i.e., remove oil by replacing the oil/solid interfacial area with surfactant solution/solid interfacial area). The presence of alkalinity as well as surfactant concentration is known to affect the ability of a surfactant solution to wet the solid surface and displace the oil. Experiments have been performed to determine quantitatively the effects of surfactant concentration and pH on the displacement of an oil from a metal surface. The displacement is measured in terms of the contact angle formed by the oil on the solid surface in the presence of the surfactant solution, the amount of time needed for the surfactant solution to cause part of the oil to detach from the solid surface, and the volume of the detached oil. Measuring the contact angle of the oil as a function of time shows that surfactant concentration and pH affect the displacement of oil from a metal surface. Increasing the pH of a solution of Triton X-100, a non-ionic surfactant, enhances oil displacement. Increasing the surfactant concentration also enhances oil displacement. The volume of oil which detaches from the solid surface increases with increasing pH and increasing surfactant concentration. * Research supported by the Division of Chemical Sciences, Office of Basic Energy Sciences, U.S. Department of Energy under contract DE-AC05-96OR22464 with Lockheed Martin Energy Research Corporation and the Department of Chemical Engineering at the University of Tennessee, Knoxville, Tennessee.

DISTILLATION UNDER ELECTRIC FIELDS*

ABSTRACT Distillation is the most common separation process used in the chemical and petroleum industry. Major limitations in the applicability and efficiency of distillation come from thermodynamic equilibria, that is, vapor-liquid equilibria (VLE), and heat and mass transfer rates. In this work, electric fields are used to manipulate the VLE of mixtures. VLE experiments are performed for various binary mixtures in the presence of electric fields on the order of a few kilovolts per centimeter. The results show that the VLE of some binary mixtures is changed by electric fields, with changes in the separation factor as high as 10% being observed. Batch distillation experiments are also carried out for binary mixtures of 2-propanol and water with and without an applied electric field. Results show enhanced distillation rates and separation efficiency in the presence of an electric field but decreased separation enhancement when the electric current is increased. The latter phenomenon is caused by the formation at the surface of the liquid mixture of microdroplets that are entrained by the vapor. These observations suggest that there should be an electric field strength for each system for which the separation enhancement is maximum. * This research was supported by the Environmental Management Science Program, Office of Environmental Management, U.S. Department of Energy, under contract DE-AC05-96OR22464 with Lockheed Martin Energy Research Corp. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.

Investigation of Electrokinetic Decontamination of Concrete

Experiments have been conducted to investigate the capabilities of electrokinetic decontamination of conceret. Batch equilibration studies have determined that the loading of cesium and strontium on concrete may be decreased using electrolyte solutions containing competing cations, while solubilization of uranium and cobalt, that precipitate at high pH, will require lixiviants containing complexing agents. Dynamic electrokinetic experiments showed greater mobility of cesium than strontium, while some positive results were obtained for the transport of cobalt through concrete using EDTA and for uranium using carbonate. *Managed by Lockheed Martin Energy Research Corp. for the U. S. Department of Energy under contract DE-AC05-96OR22464.

Particle Flocculation and Filtration by High-Gradient Magnetic Fields*

Flocculation and filtration of micrometer-sized particles in a high-gradient magnetic field (HGMF) were investigated. Experiments were conducted using a cryogenic magnet of 6 Tesla maximum strength. Hematite particles were used for flocculation and filtration experiments. A new approach of using magnetic fields to enhance separation of weakly magnetic particles was also investigated. This approach is based on magnetic seeding which involves flocculation of existing nonmagnetic particles with injected paramagnetic particles. A particle-flocculation model was developed based on trajectory analysis. External forces due to gravity and magnetism, and interparticle forces such as electrostatic, hydrodynamic, magnetic dipole, and van der Waals forces, were taken into consideration in these models. * This research was supported by the Division of Chemical Sciences, Office of Basic Energy Sciences, the AR&TD program of Fossil Energy, and the Efficient Separations and Processing Crosscutting Program, Office of Environmental Management, U.S. Department of Energy, under contract DE-AC05-96OR22464 with Lockheed Martin Energy Research Corp. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.

Modeling the Electrokinetic Decontamination of Concrete

The decontamination of concrete is a major concern in many Department of Energy (DOE) facilities. Numerous techniques (abrasive methods, manual methods, ultrasonics, concrete surface layer removal, chemical extraction methods, etc.) have been used to remove radioactive contamination from the surface of concrete. Recently, processes that are based on electrokinetic phenomena have been developed to decontaminate concrete. Electrokinetic decontamination has been shown to remove from 70 to over 90% of the surface radioactivity. To evaluate and improve the electrokinetic processes, a model has been developed to simulate the transport of ionic radionuclei constituents through the pores of concrete and into the anolyte and catholyte. The model takes into account the adsorption and desorption kinetics of the radionuclei from the pore walls, and ion transport by electro-osmosis, electromigration, and diffusion. A numerical technique, orthogonal collocation, is used to simultaneously solve the governing convective diffusion equations for a porous concrete slab and the current density equation. This paper presents the theoretical framework of the model and the results from the computation of the dynamics of ion transport during electrokinetic treatment of concrete. The simulation results are in good agreement with experimental data. * Managed by Lockheed-Martin Energy Research Corporation, Inc. for the U.S. Department of Energy under contract DE-AC05-84OR21400