9 research outputs found
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Test Plan: Sludge Treatment Project Corrosion Process Chemistry Follow-on Testing
This test plan was prepared by the Pacific Northwest National Laboratory (PNNL) under contract with Fluor Hanford (FH). The test plan describes the scope and conditions to be used to perform laboratory-scale testing of the Sludge Treatment Project (STP) hydrothermal treatment of K Basin sludge. The STP, managed for the U. S. Department of Energy (DOE) by FH, was created to design and operate a process to eliminate uranium metal from the sludge prior to packaging for Waste Isolation Pilot Plant (WIPP) by using high temperature liquid water to accelerate the reaction, produce uranium dioxide from the uranium metal, and safely discharge the hydrogen. The proposed testing builds on the approach and laboratory test findings for both K Basin sludge and simulated sludge garnered during prior testing from September 2006 to March 2007. The outlined testing in this plan is designed to yield further understanding of the nature of the chemical reactions, the effects of compositional and process variations and the effectiveness of various strategies to mitigate the observed high shear strength phenomenon observed during the prior testing. These tests are designed to provide process validation and refinement vs. process development and design input. The expected outcome is to establish a level of understanding of the chemistry such that successful operating strategies and parameters can be implemented within the confines of the existing STP corrosion vessel design. In July 2007, the DOE provided direction to FH regarding significant changes to the scope of the overall STP. As a result of the changes, FH directed PNNL to stop work on most of the planned activities covered in this test plan. Therefore, it is unlikely the testing described here will be performed. However, to preserve the test strategy and details developed to date, the test plan has been published
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Preconceptual Design Description for Caustic Recycle Facility
The U.S. Department of Energy plans to vitrify both high-level and low-activity waste at the Hanford Site in southeastern Washington State. One aspect of the planning includes a need for a caustic recycle process to separate sodium hydroxide for recycle. Sodium is already a major limitation to the waste-oxide loading in the low-activity waste glass to be vitrified at the Waste Treatment Plant, and additional sodium hydroxide will be added to remove aluminum and to control precipitation in the process equipment. Aluminum is being removed from the high level sludge to reduce the number of high level waste canisters produced. A sodium recycle process would reduce the volume of low-activity waste glass produced and minimize the need to purchase new sodium hydroxide, so there is a renewed interest in investigating sodium recycle. This document describes an electrochemical facility for recycling sodium for the WTP
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Economic Feasibility of Electrochemical Caustic Recycling at the Hanford Site
This report contains a review of potential cost benefits of NaSICON Ceramic membranes for the separation of sodium from Hanford tank waste. The primary application is for caustic recycle to the Waste Treatment and Immobilization Plant (WTP) pretreatment leaching operation. The report includes a description of the waste, the benefits and costs for a caustic-recycle facility, and Monte Carlo results obtained from a model of these costs and benefits. The use of existing cost information has been limited to publicly available sources. This study is intended to be an initial evaluation of the economic feasibility of a caustic recycle facility based on NaSICON technology. The current pretreatment flowsheet indicates that approximately 6,500 metric tons (MT) of Na will be added to the tank waste, primarily for removing Al from the high-level waste (HLW) sludge (Kirkbride et al. 2007). An assessment (Alexander et al. 2004) of the pretreatment flowsheet, equilibrium chemistry, and laboratory results indicates that the quantity of Na required for sludge leaching will increase by 6,000 to 12,000 MT in order to dissolve sufficient Al from the tank-waste sludge material to maintain the number of HLW canisters produced at 9,400 canisters as defined in the Office of River Protection (ORP) System Plan (Certa 2003). This additional Na will significantly increase the volume of LAW glass and extend the processing time of the Waste Treatment and Immobilization Plant (WTP). Future estimates on sodium requirements for caustic leaching are expected to significantly exceed the 12,000-MT value and approach 40,000-MT of total sodium addition for leaching (Gilbert, 2007). The cost benefit for caustic recycling is assumed to consist of four major contributions: 1) the cost savings realized by not producing additional immobilized low-activity waste (ILAW) glass, 2) caustic recycle capital investment, 3) caustic recycle operating and maintenance costs, and 4) research and technology costs needed to deploy the technology. In estimating costs for each of these components, several parameters are used as inputs. Due to uncertainty in assuming a singular value for each of these parameters, a range of possible values is assumed. A Monte Carlo simulation is then performed where the range of these parameters is exercised, and the resulting range of cost benefits is determined
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Scientific Opportunities to Reduce Risk in Nuclear Process Science
Cleaning up the nationās nuclear weapons complex remains as one of the most technologically challenging and financially costly problems facing the U.S. Department of Energy (DOE). Safety, cost, and technological challenges have often delayed progress in retrieval, processing, and final disposition of high-level waste, spent nuclear fuel, and challenging materials. Some of the issues result from the difficulty and complexity of the technological issues; others have programmatic bases, such as contracting strategies that may provide undue focus on near-term, specific clean-up goals or difficulty in developing and maintaining stakeholder confidence in the proposed solutions. We propose that independent basic fundamental science research focused on the full cleanup life-cycle offers an opportunity to help address these challenges by providing 1) scientific insight into the fundamental mechanisms involved in currently selected processing and disposal options, 2) a rational path to the development of alternative technologies should the primary options fail, 3) confidence that models that predict long-term performance of different disposal options are based upon the best available science, 4) fundamental science discovery that enables transformational solutions to revolutionize the current baseline processes
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Estimate of Hanford Waste Rheology and Settling Behavior
The U.S. Department of Energy (DOE) Office of River Protectionās Waste Treatment and Immobilization Plant (WTP) will process and treat radioactive waste that is stored in tanks at the Hanford Site. Piping, pumps, and mixing vessels have been selected to transport, store, and mix the high-level waste slurries in the WTP. This report addresses the analyses performed by the Rheology Working Group (RWG) and Risk Assessment Working Group composed of Pacific Northwest National Laboratory (PNNL), Bechtel National Inc. (BNI), CH2M HILL, DOE Office of River Protection (ORP) and Yasuo Onishi Consulting, LLC staff on data obtained from documented Hanford waste analyses to determine a best-estimate of the rheology of the Hanford tank wastes and their settling behavior. The actual testing activities were performed and reported separately in referenced documentation. Because of this, many of the required topics below do not apply and are so noted
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Caustic Recycle from Hanford Tank Waste Using NaSICON Ceramic Membrane Salt Splitting Process
A family of inorganic ceramic materials, called sodium (Na) Super Ion Conductors (NaSICON), has been studied at Pacific Northwest National Laboratory (PNNL) to investigate their ability to separate sodium from radioactively contaminated sodium salt solutions for treating U.S. Department of Energy (DOE) tank wastes. Ceramatec Inc. developed and fabricated a membrane containing a proprietary NAS-GY material formulation that was electrochemically tested in a bench-scale apparatus with both a simulant and a radioactive tank-waste solution to determine the membrane performance when removing sodium from DOE tank wastes. Implementing this sodium separation process can result in significant cost savings by reducing the disposal volume of low-activity wastes and by producing a NaOH feedstock product for recycle into waste treatment processes such as sludge leaching, regenerating ion exchange resins, inhibiting corrosion in carbon-steel tanks, or retrieving tank wastes
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Preparation and Characterization of Chemical Plugs Based on Selected Hanford Waste Simulants
This report presents the results of preparation and characterization of chemical plugs based on selected Hanford Site waste simulants. Included are the results of chemical plug bench testing conducted in support of the M1/M6 Flow Loop Chemical Plugging/Unplugging Test (TP-RPP-WTP-495 Rev A). These results support the proposed plug simulants for the chemical plugging/ unplugging tests. Based on the available simulant data, a set of simulants was identified that would likely result in chemical plugs. The three types of chemical plugs that were generated and tested in this task consisted of: 1. Aluminum hydroxide (NAH), 2. Sodium aluminosilicate (NAS), and 3. Sodium aluminum phosphate (NAP). While both solvents, namely 2 molar (2 M) nitric acid (HNO3) and 2 M sodium hydroxide (NaOH) at 60Ā°C, used in these tests were effective in dissolving the chemical plugs, the 2 M nitric acid was significantly more effective in dissolving the NAH and NAS plugs. The caustic was only slightly more effecting at dissolving the NAP plug. In the bench-scale dissolution tests, hot (60Ā°C) 2 M nitric acid was the most effective solvent in that it completely dissolved both NAH and NAS chemical plugs much faster (1.5 ā 2 x) than 2 M sodium hydroxide. So unless there are operational benefits for the use of caustic verses nitric acid, 2 M nitric acid heated to 60Ā°C C should be the solvent of choice for dissolving these chemical plugs. Flow-loop testing was planned to identify a combination of parameters such as pressure, flush solution, composition, and temperature that would effectively dissolve and flush each type of chemical plug from preformed chemical plugs in 3-inch-diameter and 4-feet-long pipe sections. However, based on a review of the results of the bench-top tests and technical discussions, the Waste Treatment Plant (WTP) Research and Technology (R&T), Engineering and Mechanical Systems (EMS), and Operations concluded that flow-loop testing of the chemically plugged pipe sections would not provide any additional information or useful data. The decision was communicated through a Sub Contract Change Notice (SCN-070) that included a revised scope as follows: ā¢ Photographing the chemical plugs in the pipes before extrusion to compare the morphology of aged gels with that of fresh gels. ā¢ Setting up an extrusion apparatus and extruding the chemical plugs. ā¢ Documenting the qualitative observations on the efforts to remove the chemical plug materials from the pipe sections. ā¢ Performing X-ray diffraction (XRD) analysis of extruded gel samples to detect any crystallization of gel during storage. ā¢ Disposing of the extruded gel as a waste. ā¢ Documenting the analytical results in a test report. There were no significant morphological differences between the fresh and aged plugs except for an overgrowth of small transparent crystals on the surface of the aged NAS gel plug. An initial pressure of <150 psi was required to start extruding the aged NAS and NAP plugs, whereas the NAH plug began to extrude with the application of minimal pressure. The shear strength of extruded samples ranged from ~9 to >15 KPa for the NAS plug and from ~2 to 6 KPa for the NAH plug. Following extrusion, the NAP plug sections were thixotropic. The bulk of all the aged gel plugs consisted of amorphous material with nitratine constituting the crystalline phase. A separate question about the whether the current in-tank waste conditions will bound the future multi-tank blended feed conditions for the Waste Treatment Plant is outside the scope of this study
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Deposition Velocities of Newtonian and Non-Newtonian Slurries in Pipelines
The WTP pipe plugging issue, as stated by the External Flowsheet Review Team (EFRT) Executive Summary, is as follows: āPiping that transports slurries will plug unless it is properly designed to minimize this risk. This design approach has not been followed consistently, which will lead to frequent shutdowns due to line plugging.ā A strategy was employed to perform critical-velocity tests on several physical simulants. Critical velocity is defined as the point where a stationary bed of particles deposits on the bottom of a straight horizontal pipe during slurry transport operations. Results from the critical velocity testing provide an indication of slurry stability as a function of fluid rheological properties and transport conditions. The experimental results are compared to the WTP design guide on slurry transport velocity in an effort to confirm minimum waste velocity and flushing velocity requirements as established by calculations and critical line velocity correlations in the design guide. The major findings of this testing is discussed below. Experimental results indicate that the use of the Oroskar and Turian (1980) correlation in the design guide is conservativeāSlurry viscosity has a greater affect on particles with a large surface area to mass ratio. The increased viscous forces on these particles result in a decrease in predicted critical velocities from this traditional industry derived equations that focus on particles large than 100 ļm in size. Since the Hanford slurry particles generally have large surface area to mass ratios, the reliance on such equations in the Hall (2006) design guide is conservative. Additionally, the use of the 95% percentile particle size as an input to this equation is conservative. However, test results indicate that the use of an average particle density as an input to the equation is not conservative. Particle density has a large influence on the overall result returned by the correlation. Lastly, the viscosity correlation used in the WTP design guide has been shown to be inaccurate for Hanford waste feed materials. The use of the Thomas (1979) correlation in the design guide is not conservativeāIn cases where 100% of the particles are smaller than 74 ļm or particles are considered to be homogeneous due to yield stress forces suspending the particles the homogeneous fraction of the slurry can be set to 100%. In such cases, the predicted critical velocity based on the conservative Oroskar and Turian (1980) correlation is reduced to zero and the design guide returns a value from the Thomas (1979) correlation. The measured data in this report show that the Thomas (1979) correlation predictions often fall below that measured experimental values. A non-Newtonian deposition velocity design guide should be developed for the WTPā Since the WTP design guide is limited to Newtonian fluids and the WTP expects to process large quantities of such materials, the existing design guide should be modified address such systems. A central experimental finding of this testing is that the flow velocity required to reach turbulent flow increases with slurry rheological properties due to viscous forces dampening the formation of turbulent eddies. The flow becomes dominated by viscous forces rather than turbulent eddies. Since the turbulent eddies necessary for particle transport are not present, the particles will settle when crossing this boundary called the transitional deposition boundary. This deposition mechanism should be expected and designed for in the WTP
Deposition Velocities of Non-Newtonian Slurries in Pipelines: Complex Simulant Testing
One of the concerns expressed by the External Flowsheet Review Team (EFRT) is about the potential for pipe plugging at the Waste Treatment and Immobilization Plant (WTP). Per the reviewās executive summary, āPiping that transports slurries will plug unless it is properly designed to minimize this risk. This design approach has not been followed consistently, which will lead to frequent shutdowns due to line plugging.ā To evaluate the potential for plugging, deposition-velocity tests were performed on several physical simulants to determine whether the design approach is conservative. Deposition velocity is defined as the velocity below which particles begin to deposit to form a moving bed of particles on the bottom of a straight horizontal pipe during slurry-transport operations. The deposition velocity depends on the system geometry and the physical properties of the particles and fluid. An experimental program was implemented to test the stability-map concepts presented in WTP-RPT-175 Rev. 01. Two types of simulant were tested. The first type of simulant was similar to the glass-bead simulants discussed in WTP-RPT-175 Rev. 0 ; it consists of glass beads with a nominal particle size of 150 Āµm in a kaolin/water slurry. The initial simulant was prepared at a target yield stress of approximately 30 Pa. The yield stress was then reduced, stepwise, via dilution or rheological modifiers, ultimately to a level of <1 Pa. At each yield-stress step, deposition-velocity testing was performed. Testing over this range of yield-stress bounds the expected rheological operating window of the WTP and allows the results to be compared to stability-map predictions for this system. The second simulant was a precipitated hydroxide that simulates HLW pretreated sludge from Hanford waste tank AZ-101. Testing was performed in a manner similar to that for the first simulant over a wide range of yield stresses; however, an additional test of net-positive suction-head required (NPSHR) was performed at each yield stress condition. Unlike the previous simulant, the sizes and densities of the particles that can deposit in the piping are a result of the simulant precipitation process; there is expected to be a complex mixture of particles of various sizes and densities that make it difficult to predict a stability map. The objective of the testing is to observe whether behavior consistent with the stability-map concept occurs in complex simulants with mixtures of different sizes and densities