Battelle Support to the Waste Treatment Plant...

Battelle Support to the Waste Treatment Plant Projecta summary of Contributions for FY03

CONTENTS

Mixing Waste ........................................................1Battelle staff performed studies to establish pulsed jet mixers effectivenessin mixing Bingham plastic rheology waste in tanks within the WasteTreatment Plant (WTP). Battelle staff performed laboratory studies todetermine pulsed jet mixers influence on the waste, specifically the intro-duction of oxygen and the retention and release of flammable hydrogen.

Assessing Pulsed Jet Mixer Performance ..............1Investigating Oxygen and HydrogenGeneration Rates ..............................................3Testing Gas Release in Pulsed Jet Mixed Tanks ....4

Pretreating Waste ..................................................5Battelle staff demonstrated the effectiveness of two ion exchange resins atremoving cesium and the effectiveness of removing strontium and transu-ranics with precipitation from the WTP feed. Battelle staff set up thestudies needed to examine chromium removal with oxidative leaching.

Removing Cesium with Ion Exchange ..................5Removing Strontium and Transuranics withPrecipitation ......................................................6Removing Chromium with Oxidative Leaching......7

Glassifying Waste in Melters ..................................8Battelle staff examined the physical and rheological properties of radioac-tive melter feeds with respect to WTP design criteria, developed boundingphysical and rheological properties for waste materials at WTP, andsummarized information on variations and uncertainties experienced atother U.S. radioactive waste vitrification facilities. Battelle staff studiedhow mercury could move through the tank waste vitrification process.

Preparing Melter Feed........................................8Studying Waste Feed Rheology ...........................9Waste Form Qualification .................................10Abating Mercury in the Melter and Evaporator ...11

Providing Direct Staff Support............................12Battelle staff with special technical expertise provided full-timesupport by filling staff positions within WTP departments.

X-Ray Diffraction Analyses

Post-Melter Test Boiler andGas Scrubbers

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Mixing WasteAssessing Pulsed Jet Mixer PerformanceBattelle and the Waste Treatment Plan (WTP) Pulsed Jet Mixerprogram team developed and implemented a development strategyfor assessing the pulsed jet mixers performance on waste withBingham plastic rheology. The pulsed jet mixers are beingconsidered for mixing radioactive waste, which can have theconsistency of mud, in various tanks at the WTP. This strategyinvolved developing and demonstrating a scale-up strategyfollowed by extensive testing of a number of configurations inscaled prototypic vessels. These tests used simulants and mixingmeasurement methods developed for the pulsed jet mixer program.The following tasks were completed:

• Battelle and WTP Pulsed Jet Mixer program team developedand selected simulants: The Pulsed Jet Mixer program teamconsidered a number of simulants. After extensive evaluation ofrheological properties and testing in a pulsed jet mixer teststand, two inorganic simulants were selected for testing. Onesimulant is based on Laponite, a synthetic clay that istransparent in an aqueous slurry. This simulant wasextraordinarily useful for testing as it allowed direct visualobservation of the mixing behavior. The second simulantkaolin/bentonite clay is opaque but provides a closer match tothe rheology of particulate tank waste slurries. Both simulantsare inexpensive, nonhazardous, and representative of actualwaste rheological properties.

• Battelle developed mixing measurement methods: Methodswere developed to assess the mixing behavior of the opaquekaolin/bentonite clay. One method involved adding dye to themixed portion of the tank and the extent of mixing and the rateat which the tank mixes were assessed by monitoring theconcentration of the dye. A second method involved the use ofradiofrequency tags, which are becoming widely used fortracking materials. The location of these tags was monitoredwith antennas placed around or in the tank. The distributionand frequency of detection provided a measure of how well thesimulant was being mixed. A third method involved addingneutrally buoyant Lexan beads and obtaining core samples ofthe mixed simulant. The number and distribution of the Lexanbeads provided information on the extent of mixing.

Prototype Pulsed Jet Mixer

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• Battelle and the WTP Pulsed Jet Mixer program teamdeveloped and demonstrated scale-up methodology: Ascale-up methodology for pulsed jet mixers applied toslurries with Bingham plastic rheology was developed anddemonstrated. The scale-up strategy is based on anextension of turbulent steady jet theory to account for theperiodic nature of the jets produced by the mixers. Thescale-up methodology was demonstrated by conductingsimulant tests in three scaled test stands. Each of these teststands contain geometrically scaled pulsed jet mixersystems. The working volume of these test stands rangesfrom about 35 gallons to 10,000 gallons. The extent ofmixing results were used to demonstrate that the mixingresults hold at different scales and that scaled prototypesmay be used to assess mixing behavior of full-scale mixersystems.

• Battelle and Savannah River Technology Center conductedscaled prototypic vessel tests: Using WTP design drawings,three scaled prototypic vessels were designed, procured,fabricated, and assembled for testing. These test standsranged from a volume of about 200 gallons to about1100 gallons. Each of the tanks was made of clear acrylicplastic to allow observation of the mixing behavior. Thesupport structure and the pulsed jet system were designed tobe readily reconfigured so that different designs could beevaluated. More than 90 individual tests were conductedwith Laponite and kaolin/bentonite clay simulants. Theextent of mixing and the time required for mixing weredetermined and used to indicate mixing performance. Thesetests provided valuable information on the design andoperating parameters needed to achieve mixing in full-scale vessels.

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Investigating Oxygen and HydrogenGeneration RatesBattelle and WTP project personnel investigated the contribution ofoxygen on the rate of hydrogen generation from Hanford tankwaste, providing valuable information on the gas-generationcapacity and reactivity of Hanford Site tank waste during storageand processing. The use of pulsed jet mixers and other operationswill introduce oxygen into the tank wastes. Because the initialhydrogen generation correlation was developed for quiescent,anaerobic wastes, not typical of WTP, laboratory studies wereconducted to determine the influence of oxygen on the hydrogengeneration rates in wastes under quiescent and stirring conditions.Five Hanford Site waste tank materials were selected forinvestigation based on their high organic content; amount ofaluminum, a catalyst for the thermal generation of hydrogen; orother criteria.

The results showed that oxygen increases the rates of hydrogengeneration for the wastes that have 2% to 3% organic content, butdoes not appreciably alter the rates of hydrogen generation of thewastes with low organic content. The tests also showed that therate of hydrogen generation from a simulant was not accelerated bystirring it in a 20% oxygen atmosphere. The results for the otherflammable gases, methane and the C2 hydrocarbons, showed thatoxygen has little influence on the rates of methane formation.However, oxygen increases the rates of formation of the C2hydrocarbons measurably.

Reactor Vessel Used in Small-Scale Tests

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Testing Gas Release in Pulsed JetMixed TanksFor the WTP, Battelle is focused on understanding flammable gas(e.g., hydrogen) retention and release when pulsed jet mixers areused in tanks containing non-Newtonian wastes. Battelleconducted gas retention and release testing, including bench-scale development activities and experiments in pulsed jetmixed tanks covering a range of configurations and scales, allusing non-Newtonian waste simulant. Battelle conductedseveral tests to assess the volume fraction of gas retained insimulant during continuous gas generation and steady-statepulsed jet mixer operation (i.e., “gas hold up” tests), and the gasrelease characteristics (volume and rate) in scenariosrepresenting plantrestart after a loss-of-power event(i.e., “gas release”tests). Additionalproof-of-concepttests wereconducted todemonstrate gas-stripping masstransfer resultingfrom air sparging, apossible means ofmitigatingflammable gasbuildup in wastecontained in pulsedjet mixed vessels.

Approximately 9 vol% In Situ GeneratedOxygen Gas Bubbles in Kaolin/Bentonite Simulant Visible at a ClearVessel Wall

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Preatreating WasteRemoving Cesium with Ion ExchangeThe baseline plan to remove cesium in tank waste before the waste isprocessed in the WTP is to use ion exchange with SuperLig-644®

(SL-644) resin. In 2003, Battelle testing demonstrated that this resincould selectively and effectively remove cesium from Hanford tankwaste. Specifically,

• Battelle assessed the aging of SL-644 during storage conditions atWTP. The effects of storage time, storage temperature, storagemedium, storage cover gas, and resin form were assessed in areduced factorial test design.

• Battelle determined elution requirements for SL-644 for carouselcolumn operation and for SL-644 spent resin disposal. Variablesincluded eluant flow rate, acid strength and temperature, andinitial concentration of cesium on the resin. Speed andcompleteness of elution and resin degradation were used tocompare the effects of the variables in a reduced factorial testdesign. Results indicate increased temperature provided the mostefficient elution with the least resin degradation of the conditionstested.

• Battelle testing demonstrated the feasibility of resorcinol-formaldehyde (RF) resin, which is easily obtainable, as a backupresin if issues arise with SL-644. Physical, chemical, andhydraulic properties of different batches and physical forms (i.e.,spherical and ground gel) of RF, obtained from three differentvendors, were compared. SL-644 was tested in parallel forcomparison in some cases. Spherical RF displayed particularlyrapid, complete elutability and high durability. These results,combined with good capacity and other properties, suggest thatspherical RF would be an excellent alternative to SL-644.

• Battelle determined preconditioning and regeneration require-ments for ground gel RF. Ground gel RF requires approximately4 times more NaOH than SL-644, per volume of resin, forconversion to the sodium form from the acid or as-received forms.

• Battelle determined elution requirements for ground gel RF forcarousel operation and for ground gel RF spent resin disposal.Battelle verified the rapid, complete elutability of spherical RFwith an additional test.

Tank Waste

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Removing Strontium and Transuranicswith PrecipitationThe current design basis for the WTP strontium/transuranicremoval process for Envelope C wastes is the addition ofstrontium nitrate (0.075M), for isotopic dilution and strontium-90 precipitation as SrCO3, and sodium permanganate (0.05M),for transuranic removal, at 50°C. Battelle and the SavannahRiver Technology Center demonstrated the effectiveness of thestrontium-90 removal step. The selection of the permanganateprecipitation step was largely the result of work conducted atBattelle. Other reagents had been considered for the process,but the resulting precipitates could not be removed by crossflowfiltration, the baseline technology for entrained solids removalin the WTP.

Several important findings emerged from thesestudies. The most important finding was, the processis very robust with regards to strontium-90 andtransuranics decontamination. The rate of mixingwas found to have little impact on decontamination,important because the plant design is based onpulsed jet mixers, which result in slower mixing ratesthan other conventional mixing technologies.Battelle demonstrated that decontamination could beachieved with much lower chemical additions,

which would result in lower initial chemical costs and reducedvolumes of waste for vitrification.

Temperature was found to be important and precipitationtemperature should not be reduced below 25°C. However, theprecipitation temperature could be reduced from 50°C to 25°Cwithout impacting decontamination. This would reduce energyrequirements to heat the waste for precipitation, then coolbefore crossflow filtration. Precipitation time was determined tobe most critical to the process; waiting at least 24 hours afterreagent addition to filter the solids was required to achieve highdecontamination with low levels of reagent and ensurecomplete precipitation of the added reagents. The impact ofthese optimized process conditions needs to be balanced withpotential negative impacts on filter performance.

Battelle demonstrated the strontium/transuranic removal processremained robust under variations in process conditions. Theresults of these studies showed how the process could beoptimized to reduce chemical procurement costs, energyconsumption, and reduce waste volume for vitrification.

A Cells Unit Filter

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Removing Chromium withOxidative LeachingThe chromium content in waste fed to the WTP limits the amount ofhigh-level waste that can be incorporated into each glass log, raisingthe costs and increasing the number of logs that need to be made.Battelle worked with the WTP project to set up the studies needed toexamine the effectiveness and other parameters involved in usingoxidative leaching to remove chromium from the waste stream andtransfer it to the low-activity waste (LAW) stream, where it poses lessof a problem.

Battelle extensively washed the tank SX-101 and SY-102 sludgesamples to remove all readily soluble chromium from the tanksludge. Battelle completed thefollowing preliminary examinations:• Scanning electron microscopy-

electron dispersion spectroscopy• X-ray diffraction analyses• Inductively coupled plasma

atomic emission spectrometrymetals analysis

• Gamma energy analyses• Alpha energy analyses

Based on the information fromthese tests, samples were takenfor actual testing.

X-Ray Diffraction Analyses

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Glassifying Waste in MeltersPreparing Melter FeedBattelleexamined thephysical andrheologicalproperties ofseveral actualradioactivemelter feedswith respect toWTP designcriteria. Theresultsvalidated manyof the plant’soriginalassumptions.Specifically,testing atBattelleshowed thelow-activity pretreated waste behaves as a Newtonian fluid withvery little solids content under the WTP baseline conditions.Testing also showed that after glass formers were added, theLAW melter feed is well behaved. The results pointed out severalareas that required more attention, including the high shearstrengths that result if the LAW melter feeds are allowed to settleand the high yield stress of the high-level waste pretreatedsolids. These issues emphasized the need for retainingmixing capabilitites during agitator failure and off-normaloperating conditions.

Following Cesium and Technetium Decon-tamination, Glass Former Chemicals areAdded to the Tank AZ-101 Waste toGenerate Feed for the LAW Melter

Battelle staff are workingwith WTP to optimize thephysical and rheologicalproperties of this feed

to maximize melterthroughput while meetingthe requirements of thefeed delivery system.

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Studying Waste Feed RheologyBattelle developed a set of bounding physical and rheologicalproperties for waste materials that can be reasonably processed andare likely to be encountered in the WTP vitrification facilities. Thisinformation is to be used by the WTP to facilitate consensus amongResearch and Technology, Environmental and Nuclear Safety, Design,and Process Engineering functions. Ultimately, a set of boundingphysical and rheological properties will be used by WTP to designprocess equipment for WTP vitrification facilities. With Battelle’sresearch, the transfer and processing problems that may beencountered can be predicted more accurately.

Battelle identified physical and chemical parameters that aresignificant to WTP vitrification-stream processing through the use ofdimensional analysis. Battelle compared that data with historical datafor actual and simulated process streams. Battelle used the physicaland chemical parameters identified to recommend upper and lowerbounding ranges that, if exceeded, will likely result is performancedegradation.

Battelle also developed bounding conditions for two LAW vitrificationstreams: 1) pretreated LAW and 2) LAW melter feed. The boundingconditions proposed by Battelle were formulated on actual waste data,theoretical/empirical correlations, and the need for a reduction inplant operational risk.

Based on these bounding properties, Battelle determined that physicaland rheological data do not exist for the complete set of LAWs thatwill be processed at the WTP. Battelle’s research did not address therheological effects of gas generation and retention, which should beinvestigated further.

Bounding Conditions forPretreated LAW

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Waste Form QualificationBattelle gathered and summarized information on variations anduncertainties experienced during vitrification operations at theDefense Waste Processing Facility and the West ValleyDemonstration Project to assist in quantifying variations anduncertainties in waste form qualification activities for WTP’simmobilized high-level waste and immobilized LAW facilities.Battelle obtained, statistically analyzed, and summarized theprocess data for the first Defense Waste Processing Facility wastetype and the West Valley Demonstration Project waste type. Ingeneral, the data from these two vitrification facilities for allsampling locations, chemical species, and properties (e.g.,density) exhibit similar behavior with relatively well-definedinitial and final trends and a middle portion of relatively stabledata. Outliers are also fairly common for many species andproperties.

Battelle gathered and summarized the best available WTP projectestimates of variations and uncertainties that will affectimmobilized high-level waste and immobilized LAW vitrificationprocesses. Although a lack of relevant test and computersimulation data limited the estimates of WTP immobilized high-level waste and immobilized LAW variations and uncertainties,Battelle was ableto obtain andsummarize someinformationincludinginhomogeneitydue to pulsed jetmixing,compositionalanalyticaluncertainties,densitymeasurementuncertainties, andglass formerchemicalsuncertainties.

Preparation of LAW Glass

Minute Phase Identification/QuantificationWithin LAW Glass

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Abating Mercury in the Melter andEvaporatorMercury in the tank waste can form different chemical species duringvitrification. The physical properties of these mercury species providedifferent pathways for the mercury in the WTP. This requires differentabatement schemes to control mercury releases. To simulate key WTPconditions that may affect mercury speciation, Battelle conductedseven processing campaigns over a ~120-hour period that involvedselected combinations of three mercury, two halogen, and tworeductant feed concentrations using Battelle’s research-scale melter.Continuous emission monitoring for volatiles in the unquenchedmelter exhaust was conducted by Battelle during all seven testconditions.

Beyond the continuous emission monitoring studies, Battelleconducted four discrete U.S. Environmental Protection AgencyMethod-29 sampling campaigns to characterize the melter-effluentsource and the chemical species of effluent mercury in particular.Battelle routinely sampled secondary waste streams to furtherelucidate the fate and behavior of mercury and all other species in thewaste simulant.

Battelle conducted a separate, post-melter test evaporator study toproject mercury partitioning in liquid effluent retention facility/effluent treatment facility and vessel vent streams. A secondaryaqueous waste stream generated by the melter’s quench-scrubberwas used.

Using representative glass samples generated under worst-case, high-mercury testing conditions, Battelle conducted U.S. EnvironmentalProtection Agency’s Toxicity Characteristic Leach Procedure test todemonstrate land-disposal suitability of the simulated waste glassproduced during research-scale melter testing. The extremely lowmercury concentrations in the glass present no adverse leachingproblems that would preclude the vitrification product fromconforming with all existing Resource Conservation and Recovery Actland-disposal limits.

Research-Scale Melter

Interior of Enclosed Melter

Post-Melter Test Boilerand Gas Scrubbers

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Providing Direct StaffSupportSeveral Battelle staff with special technical expertise providedfull-time support to the WTP by filling staff positions within theWTP Research and Technology and Process OperationsDepartments. Specific areas of contribution included LAWvitrification, high-level waste and LAW glass formulation, wasteform qualification, thermodynamic modeling, ion exchange,technical management and simulant validation.

• LAW vitrification: A Battelle staff member led a multi-disciplinary team in a development and testing program togenerate and demonstrate a melter bubbler design sufficientto meet the WTP design need (i.e., lifetimes of greater than17 weeks). Bubbler lifetimes were increased from 8 weeksto over 26 weeks, eliminating one of WTP’s greatesttechnical risks and resulting in a cost avoidance of$50 million. The staff member also played a key role in apilot melter test program that demonstrated enhanced melterproduction rates for all LAW feeds anticipated during the firstphase of WTP operation. These enhanced production ratesalso dispositioned a major WTP technical risk.

• Glass formulation and waste form qualification: Throughthe leadership of two Battelle staff members, two majorexperimental programs were completed and documented toprovide the technical basis for a land disposal restrictionstreatability variance petition for LAW and high-level wasteglasses and for a high-level waste delisting petition, bothmajor WTP deliverables to DOE’s Office of River Protectionin 2003.

• Ion exchange: Battelle staff provided evidence and technicalbasis for the process design for cesium removal using anorganic elutable ion exchange resin.

Advanced Bubbler Designs

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• Waste simulant validation: A Battelle staff member serves at theSimulant Coordinator ensuring the development and use ofsimulants is coordinated, consistent, and defensible. This personis the principal contact for all simulant questions and involvedin resolving all issues that involve the “performance” of asimulant.

• Chemical thermodynamic modeling: Thermodynamic modelswere developed to determine the present waste composition andmodel WTPprocesses.The models are usedto determine therequired amounts ofreagents, estimatevolumes of LAW andhigh-level wasteglass, and determinethe fate ofcontaminantsin WTP.

Thermodynamic Modeling of Tank Waste

Terry WaltonEnvironmental Management(509) [email protected]

For More Information, Contact:

PNWD-SA-6404

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