June 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
Accelerating Phytoremediation by Monitoring Plant Status
During the month of June, we continued a mercury phytoremediation experiment with brake fern. The experiment was started in May. Mercury was provided as HgC12, HgS and Hg(NO3)2. We collected plants and soil samples at different stages of the phytoremediation process. Spectral reflectance was used to monitor the process. This experiment is expected to be finished in July. Meanwhile, we will continue to analyze samples and data from previous experiments.
Task 2
Support of Hanford Single Shell Tank Waste Disposition
In-tank/At-tank Characterization for Closure of Hanford Tanks
Stereovision. Efforts to optimize the stereovision system for operation in the Hanford tanks continued as did our effort to prepare a scientific journal paper describing our state-of-the-art system.
Laser-induced fluorescence-spectral imaging. During May, the charge-coupled device (CCD) camera detector on the spectrometer was diagnosed as malfunctioning, was sent to the manufacturer for repair, and was received back from the manufacturer in late May. Subsequent testing revealed that the CCD detector was still not functioning properIy, and it has once again been shipped to the manufacturer for repair. We will use this system to collect laser-induced fluorescence spectra of selected simple uranium compounds.
Microwave-induced plasma-cavity ringdown spectroscopy. Measurements of mercury using microwave-induced plasma source cavity ringdown spectroscopy (MIP-CRDS) were conducted under atmospheric conditions. A standard Hg solution was diluted to different concentrations. Elemental Hg was generated by the MIP. With optimized experimental conditions, such as plasma power, gas flow rates, and plasma positions, detection sensitivity of mercury at 254 nm was determined to be 10 ppb, based on the standard three criteria. The spectrum of Hg with hyperfine structures at 254 nm was also recorded. The forbidden transitions of the Hertzberg band I 
of O2, pose a strong background spectral interference in this stectral kgion. The detection sensitivity can be expected to be improved by employing a tube-shaped MIP as the plasma source. Performance of this type of plasma source is being tested.
Fiber optic sensors. Work this month focused on connecting the Hamamatsu photomultiplier tube (PMT) to an optical fiber. Mechanical parts have been fabricated to couple light guided through an optical fiber into the PMT and block stray light from entering the PMT.
Fourier transform profilometry. The preliminary design of the insertion probe has been completed. We are beginning fabrication of a three-section telescoping probe that is shorter in length, but the same diameter as the full-size version; this unit will be used to test the design. For the detachable elbow section of the insertion probe, efforts continued with the projector optical arrangement. Laying out all the elbow components on an optical table has been completed. We are currently transferring these components to a 1-meter optical rail; the effects of the various component positions on the results of FTP measurements will be determined. Efforts to correct target distortion introduced by non-perpendicular FTP viewing geometry continued. Further experiments with variations in image contrast, projected fringe frequencies, and image resolution to verify and eventually eliminate the target height stepping effect are underway.
Information sifting. The information sifting effort is at present testing the spectrum identification tool using reflectance spectra of simple uranium compounds and other test data. The implementation of the spectrum identification tool is completed.
Process Chemistry and Operations Planning for Hanford Waste Alternatives
Work continues on preparing and evaluating solutions of aluminum with added nitrate and of aluminum with added phosphate. All solutions are being prepared based on 100 g of water. Each solution is then split; and one portion is sampled at two week intervals to assess the approach to thermodynamic equilibrium. The remaining fraction will only be sampled once equilibration has been established. Based on the existing aluminum - nitrate solutions it appears that equilibration times will be greater than four months. Additional model calculations are in progress.
Simulations for the FIU pilot-scale column test are continuing. Layer models are under consideration for modeling the heterogeneous salt cake batches within the column. DifficuIties have been encountered with the top most column material as it is of low free water loading. From a modeling standpoint this has led to convergence difficulties. Flow sheet alternatives that address this problem are under consideration. Simulations and analysis of the retrieval of salt waste in Hanford tank S-102 are continuing. Results indicate that the dissolved salt solutions that will be transferred to SY-103 are high in phosphate loading. Even slight cooling of the streams is predicted to result in precipitation of sodium phosphate dodecahydrate which tends to for gels. Various additives are under investigation to prevent formation of this solid, either in a transfer line or in the receipt tank.
Flexible Scintillating Optical Fiber Sensor for Determination of Liquid Level
A fiber optic coupling interface for the photomultiplier tube (PMT) was designed and constructed during this reporting period. The necessity of this interface was realized as initial attempts to couple fused silica capillary fibers to the original PMT housing were unsuccessful. The interface includes a piece of aluminum (3 mm thick, 3 cm in diameter) tapped and mounted with a fiber optic coupler (SMA type). This adaptor has been mounted to the face of the PMT (separated with an O-ring for preservation of the detection window) using a modified polyethylene cap which holds the entire assembly together. This fiber optic interface provides a means for rapid and reproducible coupling of fused silica fibers to the face of the PMT. During the development stage of this project, this capability will be critical as many different fibers must be tested to determine the optimal scintillation coating agent. The fused silica capillaries coated with respective scintillating agents will be tested using the aforementioned PMT configuration.
Tank Leak Detection and Monitoring System
The manually-controlled laboratory-level tank leak detection system was packed into a mobile rubber cart last month. Efforts in June focused on testing the long-term reliability of the system performance. Two individual, one-week non-stop tests were conducted. The ringdown baseline stabilities obtained were better than 0.5%. The spectral scans of atmospheric water, methane, and carbon dioxide in the near IR spectral region were recorded by utilizing commercial instruments for the electronic control combined with manual operation of the laser wavelength scanning. Molecular concentrations of these three gases were determined to be 12500,1.8, and 350 ppm, respectively; the results were compared with the theoretical concentrations calculated using Hitran 96 database. Based on the baseline stability obtained in the testing and the absorption crosssections of these molecules documented in the literature, the measurement uncertainty of the concentrations is less than 15%. Under the same experimental condition, the measurement uncertainty of the system is expected to be improved to 5% by using a programmed temperature control which will provide a higher resolution scan of the laser wavelength.
In order to test potential spectral interferences, the ringdown mirrors must be mounted on a gas cell which allows the system to be purged and filled with sample gases. The gas samples will be introduced through a long tube-shaped probe which will be deployed underground during a real tank site test. A micro filter with a diameter of 2 um will be installed on the probe head to prevent particles from being sucked into the gas cell. The system can be upgraded to incorporate different ringdown gas modules for measurements of several different gas species which are present in the tank waste plume.
Task 3
Disposition of Idaho HLW Calcine
Support of INEEL Calcine Disposition Project
DIALMSU is working on the procurement of equipment and materials to perform the work outlined in the test plan.
Task 4
Support of SRS Salt Disposition and Other SRS Alternatives
Support for SRS Salt Disposition Alternatives
Work focused on completion of a second drain, add, sit, and remove experiment for simulated salt waste based on SRS Tank 38H. The previous experiment revealed unusual trends in nitrite and aluminum ion concentrations as a function of diluent added. These trends were confirmed in the recent experiment. The only physical explanations for the increases of nitrite and aluminum observed in the 20 - 30% dilution by weight range are either the initial precipitation of sodium nitrite and gibbsite followed by re-dissolution as larger amounts of water are added, or that the remaining interstitial liquid within the salt cake waste in the column is not effectively mixed with the generated dissolved salt solution. Efforts to model the process, amounting to a reconsideration of the extent of mixing that is actually occurring within the column, are in progress.
On-line Analysis for Defense Waste Processing Facility
During this reporting period, three glass samples with different Li-to-Fe ratios were made. LIBS data of these glass samples were recorded under different laser energies and gate delay time. These data were analyzed with different Li and Fe analyte lines. We found that the higher laser energy and longer gate delay time results in a serious saturation effect for high Li/Fe ratio. The data recorded with 12.5 mJ and 1 microsecond gate delay time shows a linear calibration for many pairs of the Li and Fe lines. Among all the tested Li and Fe lines, we found that Li 610.4 nm and Fe 440.48 nm give the best relative accuracy and precision (better than 7%). The glass samples were sent to the analytical laboratory for analysis.
Support of Production of High Waste Loading Glasses in the DWPF
DIAL, has performed DSC analysis on Frit 418 and compared it to the signal from the 185% and 155% material. Concerning the melt rate, experiments were conducted in which pellets were melted on an approximately 15 degree slope and on a flat surface in an attempt to detect variations in the melt rate that would show either in a faster "running" down the slope or in a more rapid increase in diameter of the molten pellet. Neither technique showed significant differences between the pellets. In the slope test, the 185% pellet adhered to the slope before the 155% material, suggesting an earlier softening. More investigation will be conducted.
Task 5
HEPA Filter Performance Assurance
Regenerable HEPA Filter Performance Testing
Extensive testing on the HEPA test stand was completed during the month of June. The particulate challenge for these tests was potassium chloride. A loaded filter test with the cyclone inline with the particle generator was completed. Another loaded filter test without the cyclone in line was completed also. It was determined that removing the cyclone from the particle generator allowed particulate to predominately load on the face of the filter, thus increasing the weight of the particulate captured by the filter. The cyclone captured the larger particles, which allowed the smaller particles to move deeper into the filter. This allowed the particulate to increase the differential pressure across the filter with less mass.
Media penetration tests were completed with 47-mm filters. Filters tested included Porvair sintered metal filters, S and S-glass fiber filters, Whatman Method 5i filters, and the 47-mm HEPA glass fiber filters.