The Melter PerformanceAssessment (MPA) activity in the Pacific Northwest Laboratory's (PNL)(a) Hanford WasteVitrificationPlant (HWVP) Technology Development (PHTD) effort is intendedto determinethe impactof noble metals on the operationallife of the referenceHWVP melter. As a partof this activity, a parametricmelter test was completed using a Research-Scale Melter (RSM). The RSM is a small, approximately1/100-scale melter, 6-in.-diameter, thatallows rapidchanging of process conditions and subsequentre-establiehmentof a steady-statecondition. The test matrix contained nine differentsegments thatvaried the melter operatingparameters(glass and plenumtemperatures)and feed properties(oxide concentration,redox potential, and noble metal concentrations)so that the effects of these parameterson noble metal agglomerationon the melter floor could be evaluated. The RSM operatedfor 48 days and consumed 1,300 L of feed, equatingto 153 tankturnovers.The runproduced531 kg of glass, During the latterportionof the run, the resistance between the electrodes decreased. Upon destructiveexaminationof the melter, a layer of noble metals was found on the bottom. This was surprisingbecausethe glass residencetime in the RSM is only 10% of the HWVP plant melter. The noble metals layer impacted the melter significantly. Approximately1/3 of one paddle electrode was melted or corrode_l off. The cause is assumed to be localized heating from short circuitingof the electrode to the noble metallayer. The metal layer also removed approximately 1/2 in. of the refractoryon the bottom of the melter. The mechanismfor this damage is not presently known. Samples taken from the bottomof the RSM contained a 2 to 4-ramlayer of precipitated noble metals. ScanningElectron Microscopy/EnergyDispersive X-Ray (SEM/EDX) analyses of the layer found that it consisted of metallic particles(10 to 20/_m) of a Ru/Rh alloy surroundedby two separate, continuous phases. One of these continuous phases was an alloy of metallic Pd/Ag/Te with a small amount of Ru metal. The other continuousphase was pureRuO2. It is assumedthat the layer was made up of RuO2 needles and alloys of Pd/Rh/Ag/Te until the last segment of the run which was rununder reducingconditions (Fe+2/_Fe-0.25). This reductionof the RuO2 has significance with respect to HWVP operation. At Fe+2/_Fe = 0.19 palladium alloy spheres were formed. At Fe+2/_Fe = 0.25 there were no visible RuO2 crystals. All of the RuO2 at this point was apparently reducedto metal. This was not expectedto occur so close to the plant redox operatinglimit. The upperredox operating limit for the plant is Fe+2/_Fe-0.23. Under these conditions, the floes of RuO2 could reduceto metallic ruthenium and alloy with rhodium.This would increasethe rate of noble metals sedimentation and thus shorten the life of the melter. (a) PNL is operatedfor the U.S. Departmentof Energy by Battelle Memorial Instituteunder ContractDE-AC06-76RLO 1830. iii Mass balance calculations indicate that approximately 5 % of the noble metals present in the feed precipitate...

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Reprint of historical document PVIPC9Sm.03E. dated September 1995. Data. formaaing. and ocher mnvcntiom refla standards at thc original dak of printing. Technical p a r review and cdilorii reviews may m have been pufamcd. DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor Esnelle Memorial Institute, nor any of their employees, makes any warranty, express or implied, or assurnesany legal liability or responsibility forthe accuracy, completeness, or.usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by 'trade name, trzdemark, manufacturer, or othenvise h 2 s not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Banelle Memorial Institute. Project to test and model simulated waste to support design, feed processibility, operations, permitting, safety, and waste-form qualification. Parallel testing with actual radioactive waste is being performed on a laboratory-scale to c o n f i r m the validity of using simulants and. glass property . models developed from simulants.Laboratory-scale testing has been completed on three radioactive core samples from tanks 101-AZ and 102-AZ containing neutralized.current ac.id waste (NCAW), which is one of the first waSte types to be.processed in the high-level waste vitrification plant under a privatization scenario.Properties of the radioactive waste measured during process and product testing were compared to simulant properties and model predictions to donfirm 'the validity of simulant and glass property models work. This repoh includes,re&s from the three NCAW core samples, comparable results from slurry and glass simulants, and comparisons to glass property model predictions. Experimental Approach 'The three NCAW samples were retrieved from the tanks in cylindrical segments 1 .inchin ' ' diameter and 19 inches long. Several segments representing a complete vertical sample of the settled solids in the tank were combined and blended to make up a core sample. Solids from each core sample were pretreated using a water wash/settle/decant process, including a ferric-nitrate flocculent additive, settle/decant, and two water washes (3 volunies deionized water to 1 volume solids). The washed solids were then characterized chemically, radiochemically, physically, and rheologically (101-AZ Core 1 only). After adjusting the samples to 125 g waste oxide& the waste was trea'ted with formic acid to adjust the feed rheology and to reduce the redox-sensitive species for introduction into the melter,. Off-gas analysis during formic acid addition was performed on 102-AZ Core 2 and . is described in a'separate report.") The formated slurry samples were characterized chemically, physically, and rheologically. Frit was added to ...

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This report is compiled by the Nuclear Waste Treatment Program (NWTP) and the Hanford Waste Vitrification Program (HWVP) at Pacific Northwest Laboratory (PNL)(a) to describe the progress in developing, testing, applying and documenting liquid-fed ceramic melter vitrification technology. Progress in the following technical subject areas during the fourth quarter of FY 1987 is discussed: melting process chemistry and glass development, feed preparation and transfer systems, canister filling and handling systems, and process/product modeling and control.Melting Process Chemistry and Glass Development -Two alternatives were evaluated for providing increased flexibility in the processing and composition of the HWVP pretreated neutralized current acid waste (NCAW). The first involved adjusting the HWVP reference frit to allow for additional sodium from the waste while maintaining the glass composition. The second alternative addressed adding Si0 2 or sodium in place of part of the frit to adjust the temperature at which the melt viscosity is 100 poise (TIOOP). The use of compositional ratios (the ratios of selected glass components to other glass components), such as the ratio of total alkali oxides to Si0 2 , to predict the TlOOP of a melt based on composition was also evaluated.This study showed that up to 5 wt% Na 2 o can be removed from the HW-39 frit composition and still maintain a commercially producible frit. This would allow for up to a 20 wt% increase of Na 2 o in the NCAW'84 waste (from 11.1 to 31.1 wt% Na 2 0J, an approximate 16 wt% increase in the NCAW'86 waste (from 17.2 to _33.5), without changing the glass composition.Glass compositional ratios were found to provide a good method of estimating the TlOOP of glass melts based on composition. The ratios using the total weight percent of alkali oxides over the sum of the weight percents of Si0 2 , Al 2 o 3 , and Zro 2 were found to predict the TIOOP sufficiently for glass development, feed rheology studies, melter testing, and potentially for HWVP process control. (a) Operated by Battelle Memorial Institute for the Department of Energy under Contract DE-AC06-76RLO 1830 ; ; ;The addition of Si0 2 or sodium in place of some portion of the frit can adjust feed compositions. Feed compositions that would yield glass viscosities outside the range required for melter operation could be adjusted to a composition that would give a glass viscosity acceptable for melter operation.PNL is exam1n1ng the effects of composition, ferrous/ferric ratio {redox state), heat treatment, and groundwater on the chemical durability of a glass proposed for solidification of West Valley nuclear waste. Several experiments have been conducted, and preliminary results are given.The results of the experiments conducted to date indicate that waste glass is more durable in groundwater than in deionized water; also, durability is affected by isothermal and simulated canister cooling heat treatments.However, the durability of the waste glass is not strongly affected by the variation of glass ...