Tank Waste Research Articles

Boehmite Dissolution Model Based on Simulant Data

Several of the Hanford waste tanks contain significant quantities of boehmite. This boehmite will be dissolved through caustic leaching as part of the Hanford Tank Waste Treatment and Immobilization Plant (WTP) currently under construction. Therefore, it is important to fully understand the nature of this dissolution process so that caustic leaching can be effectively deployed on the Hanford tank wastes. This research determined the impact of aluminate ion on the dissolution kinetics of boehmite. In addition, other parameters that impact boehmite dissolution, such reaction temperature, were also assessed and used to develop a semiempirical model of the boehmite dissolution process. A shrinking core model was used to fit data from a series of boehmite dissolution tests with an additional term added to account for the approach to saturation. This revised model provided an adequate fit to the experimental data; however, a superior fit to the experimental data was obtained when a term was added to represent t...

Development of occupational exposure limits for the Hanford tank farms

Production of plutonium for the United States’ nuclear weapons program from the 1940s to the 1980s generated 53 million gallons of radioactive chemical waste, which is stored in 177 underground tanks at the Hanford site in southeastern Washington State. Recent attempts to begin the retrieval and treatment of these wastes require moving the waste to more modern tanks and result in potential exposure of the workers to unfamiliar odors emanating from headspace in the tanks. Given the unknown risks involved, workers were placed on supplied air respiratory protection. CH2MHILL, the managers of the Hanford site tank farms, asked an Independent Toxicology Panel (ITP) to assist them in issues relating to an industrial hygiene and risk assessment problem. The ITP was called upon to help determine the risk of exposure to vapors from the tanks, and in general develop a strategy for solution of the problem. This paper presents the methods used to determine the chemicals of potential concern (COPCs) and the resultant development of screening values and Acceptable Occupational Exposure Limits (AOELs) for these COPCs. A total of 1826 chemicals were inventoried and evaluated. Over 1500 chemicals were identified in the waste tanks headspaces and more than 600 of these were assigned screening values; 72 of these compounds were recommended for AOEL development. Included in this list of 72 were 57 COPCs identified by the ITP and of these 47 were subsequently assigned AOELs. An exhaustive exposure assessment strategy was developed by the CH2MHILL industrial hygiene department to evaluate these COPCs.

The application of in situ formed mixed iron oxides in the removal of strontium and actinides from nuclear tank waste

AbstractThis article discusses the experimental program conducted at Argonne National Laboratory to study the performance of in situ formed mixed iron oxides (IS‐MIO) for the removal of strontium (Sr), plutonium (Pu), neptunium (Np), uranium (U), and americium (Am) from the Savannah River Site (SRS) radioactive tank waste. The boundaries for the experimental work were defined in collaboration with SRS. IS‐MIO was actually found to be a mixture of Fe(II) and Fe(III) oxides and hydroxides, including magnetite. Decontamination factor (DF) values were measured for both IS‐MIO and monosodium titanate (MST), the baseline sorbent used by SRS. DF values for IS‐MIO were found to be superior to MST for all isotopes studied. DF values for Pu, Np, and Sr, achieved within 30 min of IS‐MIO formation were orders of magnitude larger than the needed values. DF values for U and Am were less than the former three but still acceptable, and greater than MST. © 2010 American Institute of Chemical Engineers AIChE J, 2010

Microanalysis of Workplace Dusts from the Mixed Waste Tank Farm of the Hanford Nuclear Reservation

In this study, radioactive particles, also known as “hot particles,” were isolated from occupational dust samples collected at the Hanford Nuclear Reservation tank farm site in Hanford, WA. The present study provides previously unreported data on the size and form of workplace dust particles, which were primarily composed of toxic or radioactive elements. Environmental transport of hot particles is affected by their size, form, and composition. Information about these physical characteristics of particles gives insight into their possible source. Hot particles isolated from two dust samples collected on different days were analyzed by scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDS). This dust analysis also detected nonradioactive fine particles (less than 10 microns in size), which were primarily composed of cadmium (Cd), lead (Pb), bismuth (Bi), and tungsten (W). Microanalysis of a sample of dust collected from the nuclear waste tank farm at the Hanford Nuclear Reservation detected a set of anthropogenic particles, including radioactive and nonradioactive isotopes of metals associated with nuclear processes, such as uranium (U), thorium (Th), plutonium (Pu), Cd, Pb, W, iron (Fe), and Bi. These anthropogenic materials were generally in the 1 to 50 micron size range, with many particles in the fine fraction below 10 microns in size.

Leaching Characteristics of Hanford Ferrocyanide Wastes

A series of leach tests were performed on actual Hanford Site tank wastes in support of the Hanford Tank Waste Treatment and Immobilization Plant (WTP). The samples were targeted composite slurries...

HAZARDOUS WASTE: GAO Grades Hanford Cleanup

HAZARDOUS WASTE: GAO Grades Hanford Cleanup

Experimental investigation of cesium mobility in the course of secondary mineral formations in Hanford sediment columns at 50°C

Formation of secondary minerals and Cs mobility in Hanford sediments were investigated under conditions similar to the Hanford tank leak in a dynamic flow system at 50 degrees C. The objectives were to (1) examine the nature and locations of secondary mineral phases precipitated in the sediments and (2) quantify the amount of Cs retained by the sediment matrix at 50 degrees C. To this end, Hanford sediments were packed into 10-cm long columns and leached with simulated tank waste consisting of 1.4 M NaOH, 0.125 M NaAlO(2), 3.7 M NaNO(3), and 1.3 x 10(-4) M Cs at 50 degrees C. Compositions of outflow solution were monitored with time for up to 25 days, and the columns were then segmented into four 2.5-cm long layers. The colloidal fraction in these segments was characterized in terms of mineralogy, particle morphology, Cs content, and short-range Al and Si structure. It was observed that cancrinite and sodalite precipitated at 50 degrees C. Approximately 53% Cs was retained in the column treated by the simulated tank waste at this temperature. Cesium retention in the column was lowered in the high ionic strength solution due to competition from Na for the exchange sites. This can be explained by alteration of distribution and number of sorption sites which reduces the selectivity of Cs for Na, and through the formation of cancrinite and sodalite. The formation of hydroxide complexes in highly alkaline solutions could also contribute to relatively poor retention of Cs by hindering ion exchange mechanism.

Characterization of High Phosphate Radioactive Tank Waste and Simulant Development

A sample of high-level radioactive tank waste was characterized to provide a basis for developing a waste simulant. The simulant is required for pilot-scale testing of pretreatment processes in a nonradiological facility. The waste material examined was derived from the bismuth phosphate process, which was the first industrial process implemented to separate plutonium from irradiated nuclear fuel. The bismuth phosphate process sludge is a complex mixture rich in bismuth, iron, sodium, phosphorus,silicon, and uranium.The form of phosphorus in this particular tank waste material is of specific importance because that is the primary component (other than water-soluble sodium salts) that must be removed from the high-level waste solids by pretreatment. This work shows unequivocally that the phosphorus in this waste material is not present as bismuth phosphate. Rather, the phosphorus appears to be incorporated mostly into an amorphous iron(III) phosphate phase. The bismuth in the sludge solids is best described as BiFeO3. The behavior of phosphorus during caustic leaching of the bismuth phosphate process sludge solids is also discussed.

Theoretical Actinide Molecular Science

Interest in the chemistry of the early actinide elements (notably uranium through americium) usually results either from the nuclear waste problem or the unique chemistry of these elements that result from 5f contributions to bonding. Computational actinide chemistry provides one useful tool for studying these processes. Theoretical actinide chemistry is challenging because three principal axes of approximation have to be optimized. These are the model chemistry (the choice of approximate electron-electron correlation method and basis sets), the approximate relativistic method, and a method for modeling solvent (condensed phase) effects. In this Account, we arrange these approximations in a three-dimensional diagram, implying that they are relatively independent of each other. A fourth level of approximation concerns the choice of suitable models for situations too complex to treat in their entirety. We discuss test cases for each of these approximations. Gas-phase data for uranium fluorides and oxofluorides such as UF(6) and UO(2)F(2) show that GGA functionals provide accurate geometries and frequencies while hybrid density functional theory (DFT) functionals are superior for energetics. MP2 is seen to be somewhat erratic for this set of compounds, and CCSD(T) gives the most accurate results. Three different relativistic methods, small-core effective core potentials (SC-ECP), ZORA, and all-electron scalar, provide comparable results. The older large-core ECP (LC-ECP) approach is consistently worse and should not be used. We confirmed these conclusions through studies of the actinyl aquo complexes [AnO(2)(OH(2))(5)](n+), (An = U, Np, or Pu and n = 1 or 2) that are also used to test solvation models. As long as the first coordination sphere of the metal is included explicitly, continuum solvation models are reliable, and we found no clear advantage for the (costly) explicit treatment of the second coordination sphere. Spin-orbit effects must be included to reproduce the correct trend in An(VI)/An(V) reduction potentials. We propose a multistep mechanism for the experimentally observed oxygen exchange of UO(2)(2+) cations in highly alkaline solutions present in tank wastes. This process involves an equilibrium between [UO(2)(OH)(4)](2-) and [UO(2)(OH)(5)](3-), followed by formation of the stable [UO(3)(OH)(3)](3-) intermediate that forms from [UO(2)(OH)(5)](3-) through intramolecular water elimination. The [UO(3)(OH)(3)](3-) intermediate facilitates oxygen exchange through proton shuttling. We explain the experimentally observed stabilization of the pentavalent oxidation state of actinyl ions by macrocyclic ligands (such as 18-crown-6) as an effect of solvation: the large macrocycle screens the positive charge of the ion from the polarizable solvent. Alkyl-substituted isoamethyrin complexes are bent despite being aromatic because of steric factors, rather than fit/misfit criteria regarding the actinyl ion. By application of an efficient DFT code, actinide molecules with more than 100 atoms can now be studied routinely. "Real" chemical questions can be answered as long as we take great care to apply methods that are accurate with respect to the three axes of approximation described above. While the exclusive focus of this Account has been on the early actinide elements, these conclusions also apply elsewhere in the periodic table.

Removable waste tank

Removable waste tank

Characterization and application of SuperLig® 620 solid phase extraction resin for automated process monitoring of 90Sr

Characterization of SuperLig® 620 solid phase extraction resin was performed in order to develop an automated on-line process monitor for 90Sr. The main focus was on strontium separation from barium, with the goal of developing an automated separation process for 90Sr in high-level wastes. High-level waste contains significant 137Cs activity, of which 137mBa is of great concern as an interference to the quantification of strontium. In addition barium, yttrium and plutonium were studied as potential interferences to strontium uptake and detection. A number of complexants were studied in a series of batch Kd experiments, as SuperLig® 620 was not previously known to elute strontium in typical mineral acids. The optimal separation was found using a 2 M nitric acid load solution with a strontium elution step of ~0.49 M ammonium citrate and a barium elution step of ~1.8 M ammonium citrate. 90Sr quantification of Hanford high-level tank waste was performed on a sequential injection analysis microfluidics system coupled to a flow-cell detector. The results of the on-line procedure are compared to standard radiochemical techniques in this paper.

Spectroelectrochemical Sensor: Development and Applications

The spectroelectrochemical sensor concept uses electrochemistry to modulate an optical signal to give improved selectivity. The sensor consists of an optically transparent electrode/waveguide coated with a thin film that preconcentrates the analyte. The sensor concept was first demonstrated with ferricyanide and later it was shown to work on a complex sample by detecting ferrocyanide in radioactive Hanford tank waste. Nafion, partially sulfonated polystyrene-block-polyethylene-ran-butylene)block-polystyrene (SSEBS), and quaternized poly(vinylpyridine) (QPVP) are examples of polymers used for the thin film. Detection limits achieved by the sensor are 10-5 to 10-8 M using change in absorbance as the mode of detection and about 10-10 M using fluorescence. A sensor has been developed for detecting [Re(dmpe)3]+ where dmpe = dimethylphosphinoethane, which serves as a nonradioactive analogue for complexes of radioactive 99Tc. Some polycyclic aromatic hydrocarbons have appropriate electrochemical and spectroscopic properties for spectroelectrochemical detection as demonstrated for 1-hydroxypyrene and its conjugate 1-hydroxypyrene-glucuronide.

Uranium Phases in Contaminated Sediments below Hanford’s U Tank Farm

Macroscopic and spectroscopic investigations (XAFS, XRF, and TRLIF) on Hanford contaminated vadose zone sediments from the U-tank farm showed that U(VI) exists as different surface phases as a function of depth below ground surface (bgs). Secondary precipitates of U(VI) silicate precipitates (boltwoodite and uranophane) were present dominantly in shallow-depth sediments (15-16 m bgs), while adsorbed U(VI) phases and polynuclear U(VI) surface precipitates were considered to dominate in intermediate-depth sediments (20-25 m bgs). Only natural uranium was observed in the deeper sediments (> 28 m bgs) with no signs of contact with tank wastes containing Hanford-derived U(VI). Across all depths, most of the U(VI) was preferentially associated with the silt and clay size fractions of sediments. Strong correlation between U(VI) and Ca was found in the shallow-depth sediments, especially for the precipitated U(VI) silicates. Because U(VI) silicate precipitates dominate in the shallow-depth sediments, the released U(VI) concentration by macroscopic (bi)carbonate leaching resulted from both desorption and dissolution processes. Having different U(VI) surface phases in the Hanford contaminated sediments indicates that the U(VI) release mechanism could be complicated and that detailed characterization of the sediments using several different methods would be needed to estimate U(VI) fate and transport correctly in the vadose zone.

Usaha Pencegahan Pencemaran Pada Industri Penyamakan Kulit

Leather industries produce a complicated pollution. Action to minimize the pollution it had been done in the leather industry which is middle industry. To implement this programme will save 50 % of fresh water in hide washing process (batch system) compared to continuous processed, while install screen in wastewater 's flaw will reduce solid waste in the sedimentation tank. Recycling the de!iming washing water for washing the raw hide hes no effect to leather quality (remain unchange). While recycling pickle washing water added with tanning washing water for tanning process will produce pollutant which chrome oxide in it is 50 % less than as usually and the wet blue product is still fulfil the standard requirement. By experiment recycling pickle-washing water added with chrome oxide for tanning process has no effect to the finished leather qual

Iron Mössbauer redox and relation to technetium retention during vitrification

Technetium-99 is a long half-life radioactive fission product whose high volatility during waste vitrification (National Research Council, 2001; Migge, Mat Res Symp Proc 127:205–213, 1989) is a factor in the safe disposal of radioactive waste. Oxidation states of +7, +4 mostly, and some traces of metal have been observed in the glass (Migge, Mat Res Symp Proc 176:411–417, 1990; Darab and Smith, Chem Mater 8:1004–1021, 1996) with Tc7 + more volatile than Tc4 + , leading to a range of technetium retention in the glass varying from 0.8% to 92%. In the present experiments, a simulated high-sulfate Hanford tank waste was vitrified using a slurry fed joule heated furnace producing about 30 kg of glass per day. Various combinations of sucrose and urea were used as denitration and reducing agents in order to optimize sulfate and technetium retention. Since iron oxide is used as a glass additive, Fe-Mossbauer spectroscopy was a vital tool to monitor the melt redox through its Fe2 + /Fetot ratio. A Mossbauer glass redox scale was designed to relate the technetium speciation to its retention in the glass.

An Inorganic Microsphere Composite for the Selective Removal of 137Cesium from Acidic Nuclear Waste Solutions. 1: Equilibrium Capacity and Kinetic Properties of the Sorbent

A new inorganic ion exchange composite consisting of ammonium molybdophosphate, (NH4)3P(Mo3O10)4·3H2O (AMP), synthesized within hollow aluminosilicate microspheres (AMP‐C) has been developed. Two different batches of the sorbent were produced resulting in 20% and 25% AMP loading for two and three loading cycles, respectively. The selective cesium exchange capacity of this inorganic composite was evaluated using simulated sodium bearing waste solution as a surrogate for the acidic tank waste currently stored at the Idaho National Laboratory (INL). Equilibrium isotherms obtained from these experiments were very favorable for cesium uptake and indicated maximum cesium loading of approximately 9% by weight of dry AMP. Batch kinetic experiments were also performed to obtain the necessary data to estimate the effective diffusion coefficient for cesium in the sorbent particle. These experiments resulted in effective intraparticle cesium diffusivity coefficients of 4.99 × 10−8 cm2/min and 4.72 × 10−8 cm2/min for the 20% and 25% AMP‐C material, respectively.

An Inorganic Microsphere Composite for the Selective Removal of 137Cesium from Acidic Nuclear Waste Solutions. 2: Bench‐Scale Column Experiments, Modeling, and Preliminary Process Design

A new inorganic ion exchange composite for removing radioactive cesium from acidic waste streams has been developed. The new material consists of ammonium molybdophosphate, (NH4)3P(Mo3O10)4·3H2O (AMP), synthesized within hollow aluminosilicate microspheres (AMP‐C), which are produced as a by‐product from coal combustion. The selective cesium exchange capacity of this inorganic composite was evaluated in bench‐scale column tests using simulated sodium bearing waste solution as a surrogate for the acidic tank waste currently stored at the Idaho National Laboratory (INL). Total cesium loading on the columns at saturation agreed very well with equilibrium values predicted from isotherm experiments performed previously. A numerical algorithm for solving the governing partial differential equations (PDE) for cesium uptake was developed using the intraparticle mass transfer coefficient obtained from previous batch kinetic experiments. Solutions to the governing equations were generated to obtain the cesium concentration at the column effluent as a function of throughput volume using the same conditions as those used for the actual column experiments. The numerical solutions of the PDE fit the column break through data quite well for all the experimental conditions in the study. The model should therefore provide a reliable prediction of column performance at larger scales.

Spatially Resolved U(VI) Partitioning and Speciation: Implications for Plume Scale Behavior of Contaminant U in the Hanford Vadose Zone

A saline-alkaline brine containing high concentration of U(VI) was accidentally spilled at the Hanford Site in 1951, introducing 10 tons of U into sediments under storage tank BX-102. U concentrations in the deep vadose zone and groundwater plumes increase with time, yet how the U has been migrating is not fully understood. We simulated the spill event in laboratory soil columns, followed by aging, and obtained spatially resolved U partitioning and speciation along simulated plumes. We found after aging, at apparent steady state, that the pore aqueous phase U concentrations remained surprisingly high (up to 0.022 M), in close agreement with the recently reported high U concentrations (up to 0.027 M) in the vadose zone plume (1). The pH values of aged pore liquids varying from 10 to 7, consistent with the measured pH of the field borehole sediments varying from 9.5 to 7.4 (2), from near the plume source to the plume front. The direct measurements of aged pore liquids together with thermodynamic calculations using a Pitzer approach revealed that UO2(CO3)3(4-) is the dominant aqueous U species within the plume body (pH 8-10), whereas Ca2UO2(CO3)3 and CaUO2(CO3)32- are also significant in the plume frontvicinity (pH 7-8), consistent with that measured from field borehole pore-waters (3). U solid phase speciation varies at different locations along the plume flow path and even within single sediment grains, because of location dependent pore and micropore solution chemistry. Our results suggest that continuous gravity-driven migration of the highly stable U02(CO3)34 in the residual carbonate and sodium rich tank waste solution is likely responsible for the detected growing U concentrations in the vadose zone and groundwater.

Aplicação de rejeito argiloso de uma mineração de areia industrial como matéria-prima na indústria cerâmica

O reaproveitamento de rejeitos argilosos provenientes da mineração de areia industrial da Formação Pirambóia representa uma opção na diminuição dos impactos ambientais gerados pela sua disposição em tanques de decantação. O presente trabalho teve por objetivo testar a aplicação destes rejeitos na confecção de produtos cerâmicos. Com este intuito, foi feita a caracterização química e mineralógica, bem como ensaios cerâmicos, de amostras provenientes dos espessadores e dos tanques de decantação de uma mineração de areia da região de Analândia (SP). As amostras dos espessadores apresentam características homogêneas, alta plasticidade e presença dominante do argilomineral caulinita. Já as amostras do tanque de decantação são mais heterogêneas, silicosas e menos plásticas. Para a produção de blocos, as argilas dos espessadores mostraram-se mais adequadas por apresentarem características homogêneas, facilitando a extrusão e reduzindo os defeitos dimensionais das peças, proporcionando assim um produto final de qualidade.

The United States Department of Energy's Environmental Management Program

The year 2009 marks 20 years since the Environmental Management program was first established in the Department of Energy. At that time, nearly 50 years of nuclear activity had left a legacy that included nuclear waste and environmental contamination at more than 100 sites across the United States. The extent of the risk to our citizens and communities was unknown, and certainly many of the processes and technologies to reduce that risk had not yet been invented. Since then, the Department of Energy has closed 86 of 108 sites originally assigned to the program nationwide. The Department of Energy has packaged and safely stored the nation’s entire excess plutonium inventory. The Department has pioneered new technologies that have allowed progress in retrieving millions of liters of tank waste and safely disposing of tens of thousands of cubic meters of transuranic waste. In Fiscal years 2006 and 2007 alone, the Department of Energy demolished approximately 500 buildings (nuclear, radioactive, and industrial) as part of our decontamination and decommissioning projects. Finally, there have been great strides in restoring groundwater contaminated with radionuclides using innovative treatment systems. In August 2005, a rigorous project management system was instituted. This Department of Energy program was built on the principle of prioritizing risk reduction supported by our four guiding tenets of safety, performance, clean-up, and closure. The mission activities at our clean-up sites are targeted at our highest risk activities. In planning its environmental clean-up efforts and developing the budget for those activities, the Department seeks to focus on work that will produce the greatest environmental benefit and the largest amount of risk reduction.