October 2004

DIAL's Research Highlights

Diagnostic Instrumentation & Analysis Laboratory
Mississippi State University
John Plodinec, Principal Investigator

Prepared for the U.S. Department of Energy
Office of Science and Technology
Cooperative Agreement DE-FC01-04EW54600

Task 1

Support of Closure Sites

Fernald Silos Project Monitoring and Control Integration

Waste stabilization formulation development. Formulation testing continued. During September, the primary goal of the grout testing was to develop formulations using a super plasticizing agent on formulas that proved to be overly stiff and hence, unacceptable from an operational standpoint. These grout formulas use Advacast 500, a super plasticizing agent. Testing with Advacast has demonstrated that its use is sensitive to the total water content of the grout mixture. Addition of too much Advacast 500 results in the formation of free water on the treated material.

Two final tests need to be performed on all acceptable grout formulations, freeze/thaw and shaker tests. The freeze/thaw test is designed to simulate climactic changes during storage and transportation. The shaker test is designed to approximate the vibration and bump characteristics of transport by truck.

Wastewater equilibration study. The wastewater equilibration study (WES) was concluded in August. Follow-up activities are being planned in order to determine treatment methods that will be employed during full-scale operations. The wastewater generated during silos mining operations must meet water requirements of the Fernald Advanced Waste-Water Treatment facility.

Settling tests. During September, settling tests were performed for three settling durations. At each settling duration, the settling characteristics of three different slurry concentrations were evaluated. The resulting supernatant and settled solids component for each sample was analyzed for percent solids, radium concentration, and density. The tests were performed for settling time intervals of 8, 24 and 48 hours at slurry concentrations of 5, 10 and 15% solids.

Planned activities. The following activities are planned for the upcoming months:

Accelerating Phytoremediation by Monitoring Plant Status

During the month of October, we started a new phytoremediation experiment of mercury with brake fern. Mercury contaminated soil used in the current study was from the previous experiment; soil from each treatment group was mixed and sampled before being used again. We have also been analyzing samples and data for the mercury phytoremediation experiment that we finished in July.

Task 2

Support of Hanford Single Shell Tank Waste Disposition

In-tank/At-tank Characterization for Closure of Hanford Tanks

Stereovision. During October, the stereovision effort acquired images at selected working distances (30, 40, 50, 60 and 70 feet) appropriate to acquiring data in a Hanford waste tank. We are currently processing this data in order to determine the precision of the stereovision determinations as a function of distance. These measurements will be repeated with different camera separations in order to optimize the stereovision system for deployment in the Hanford waste tanks.

Laser-induced fluorescence-spectral imaging. During this month, the LIF-SI effort continued working with surrogate samples in order to optimize experimental conditions before recording LIF spectra of simple uranium and thorium compounds. A new graduate student with extensive laser spectroscopy experience has joined this effort.

Microwave-induced plasma-cavity ringdown spectroscopy. Currently mercury monitoring is mainly based on chemistry-based techniques, which usually utilize pre-concentration processes to increase mercury concentrations in order to increase detection sensitivities. These methods are useful for laboratory-based mercury analysis, but less practical in real applications, such as real-time, on-site mercury monitoring at mercury contaminated sites. We are using cavity ringdown spectroscopy (CRDS) under open path conditions to explore the feasibility of monitoring elemental mercury in ambient air saturated with mercury-containing vapor from mercury contaminated soil, water, plants, and atmosphere. Preliminary results show that CRDS can detect elemental mercury directly from mercury-contaminated soil and water under atmospheric pressure and at room temperature. This method may not only offer a new approach for ultra-sensitive, on-site mercury monitoring, but also may provide a new method for mercury partitioning and mechanism studies.

Fiber optic sensors. During this month, we are preparing our laboratory to synthesize CdSe/ZnS quantum dots using a reversed micelle technique reported by B. O. Dabbousi and co-workers. This is a relatively high temperature process. We are preparing glassware and planning chemical reagent purchases for this reaction. In addition, we are also seeking commercial sources of the quantum dots.

Fourier transform profilometry. The FTP probe development efforts concentrated this month on a full-engineering design (including finite element analysis) of the tower that will support the FTP probe. The tower needs to be sufficiently sturdy to firmly support the FTP probe (whether extended or telescoped together) at all times, yet be sufficiently lightweight (even with the complete probe is mounted on it) to not exceed Hanford weight restrictions for how much can be mounted atop a waste tank. This effort is ongoing. Efforts to optimize the fringe pattern projection system for conditions appropriate to the waste tanks continued. A variety of targets of different sizes were fabricated in order to more accurately assess the precision of the FTP volumetric determinations as a function of distance.

Process Chemistry and Operations Planning for Hanford Waste Alternatives

Some difficulties have been identified in the quantification of aluminum in the presence of high sodium concentrations using ICP. Using a 10 ppm aluminum standard and varying the sodium loading from 0 to 500 ppm indicated an enhanced signal strength for the aluminum transitions which translates into increased aluminum concentrations if the response calibration is based solely on aluminum standards at different concentrations alone. Examination of the literature did not reveal any sodium lines in the spectral region (396.1 ± 0.1 nm) employed for aluminum quantification. Thus other explanations for the repeatedly observed behavior are being investigated. The effect appears to arise from changes in the plasma brought about by the easily ionizable sodium ions. The increase in signal strength does not correspond to a continuum effect as only minor increases in the baseline intensities (1 - 2%) are observed as opposed to a change in 13% at the peak of the aluminum transition. Efforts to more effectively matrix match the compositions of the equilibrated aluminum - nitrate, and aluminum-phosphate systems are also being investigated. Spiking of 1000 ppm cesium into the standards appears to reduce the effect to 6% increase in peak intensity and another option, changing the rf applied to the plasma is being investigated as well. Once a reliable calibration is attained the equilibrated solutions ill be analyzed. Most of the laboratory work needed to separate the filtrate from the solids formed during equilibrium and the subsequent dilution of the filtrates has been completed.

Flexible Scintillating Optical Fiber Sensor for Determination of Liquid Level

Review of the literature procedures for synthesizing quantum dots was accomplished during this reporting period. In addition, an equipment and chemical regent list was compiled and is currently being processed. Quotes from several quantum dot suppliers have also been received with the final selection to be made during the next reporting period.

Task 3

Disposition of Idaho HLW Calcine

Support of ICP-SP3 Calcine Disposition Project

Tests were run on the curing process for the hydroceramic cement and on the effect of various compounds on the setting time of the Fe-P cement.

Task 4

Support of SRS Salt Disposition and Other SRS Alternatives

Support of Alternatives for Disposition of High Level SRS Waste

The drain, add, sit, and remove (low Curie salt process) experiment for the tank 37H simulant continued the entire month of October. The experimental run time should be contrasted to the earlier work on simulants for SRS tanks 38H and 41H which nominally lasted two and a half weeks. As noted previously, the 37H simulant contains aluminum and silicon in equal molar amounts. Previous difficulties in evaporating waste at SRS have noted the formation of sodium aluminosilicates, nominally hydroxysodalite and cancrinite. During the 37H DASR experiment it was noted that a secondary layer appeared within the salt column and PLM analysis did not reveal the presence of gibbsite, Al(OH₃). The solids forming the layer were quite small and could not be observed at a magnification of 40x. ESP model calculations indicated that the cancrinite will form at room temperature simply by direct mixing of caustic, sodium silicate pentahydrate, sodium aluminate, and sodium carbonate in water. 100 g batches of the simulant were then prepared with and without carbonate. The model predicts the formation of hydroxysodalite without carbonate and of cancrinite in the presence of carbonate. Two distinct solids have been recovered from the batch experiments and XRD analysis should commence in early November. Additional simulations were performed with the ESP software to determine a possible means for dissolving or reacting the cancrinite and sodalite. It appears possible to convert the cancrinite to hydroxysodalite using a strong caustic solution. The reaction is accompanied by the liberation of carbonate anion which can be quantified using the total inorganic carbon instrument. Work will continue on the identification of the layer constituents and on analysis of all of the fractions collected during the column experiment. The potential, low temperature, formation of cancrinite and/or hydroxysodalite within the SRS waste has significant implications on salt cake retrieval operations and equipment.

On-line Analysis for Defense Waste Processing Facility

Testing calibration-free techniques for different sample types continued. The plasma parameters (plasma temperature and electron density), optical depth for the selected emission line, and total plasma emission obtained from LIBS data of various sample types (pellet, glass and sludge) were compared. By considering all the parameters, an improved accuracy (20 - 50%) can be achieve for most elements with this calibration-free technique. However, this accuracy is still poor compared with the results obtained from the calibration data, which gives an accuracy within 10% for the major element. Also, the calibration free-technique is currently not working for elements such as Na and K that have severe self absorption problems. Various methods to correct the self-absorption effect are under evaluation. We had a conference call with DWPF staff to discuss the proposed LIBS tasks. Based on the discussion, David Peeler sent the information regarding the flow rates and materials for construction which are needed for designing a sludge sampling system in DIAL laboratory.

Support of Production of High Waste Loading Glasses in the DWPF

Experiments looking at temperatures below the usual melting point of 1150°C to examine the reaction between the frits and the surrogate waste slurry (Case 7d SRAT product) were completed last month. Samples of the frit/slurry mixture heated to 700, 800 and 900°C were polished for examination with optical and electron microscopy. Photos have been taken with the optical microscope. SEM observations were made, but were inconclusive. This experiment has been discontinued. Slumping experiments are being designed and will be run during the next reporting period.

Task 5

HEPA Filter Performance Assurance

Regenerable HEPA Filter Performance Testing

Testing for the month of October included challenging Porvair sintered metal filters with iron aerosols. The Porvair filters are 47 mm in diameter. The iron aerosol used was the RIC stimulant. The filters were loaded to two times their original clean differential pressure. Four filters were examined by the Mississippi State University scanning electron microscope. One filter was washed, loaded and washed once more. A second filter was washed and loaded once. The third filter was washed and not loaded. The fourth filter was not washed or loaded. The Porvair filters were washed with an acid solution. The filters were loaded at low relative humidity in the HEPA filter test stand.

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