DIAL's Research Highlights

Characterization of Heavy Metals and Radionuclides

On-line isotopic monitoring and analytical protocol development for uranium and other actinides. The analytical method development group's work with transition metals revealed that samples buffered with ammonium acetate gave no detector response during large volume injections. Samples buffered with acetic acid gave a good response. Samples buffered with oxalic acid gave a response, but the peak was very broad. This information is useful in determining an appropriate sample matrix needed for analysis. The group spent most of July, however, waiting for a replacement visible lamp for the photodiode array detector. Chelation chromatography will be explored now that the replacement visible lamp has been received.

The cavity ringdown/plasma system was prepared in July for work in collaboration with Dr. Yixiang Duan of Los Alamos National Laboratory (LANL). Dr. Duan transported microwave and discharge plasma systems from LANL to DIAL to be tested with our CRDS system. Initial tests have been carried out using lead for system optimization in preparation for additional measurements using uranium. These efforts are directed at continuing to reduce the size, complexity, and power requirements of the CRDS/plasma system for isotopically resolved measurements of uranium. Additional measurements were also continued using a laser ablation sample introduction system on loan from CETAC Corporation. Emission from uranium present in NIST standards at a level of 0.072 mg/kg (72 ppb) was easily observed.

The LIF group has placed a moderately high-resolution dye laser system on bid; written bids will be opened in mid-August. This dye laser system is necessary to enable us to have the required spectral resolution and not have to rely upon when we can borrow the CRDS group's laser.

Laser probe for technetium. Two frequency-doubled Nd:YAG lasers, one Spectra Physics and the other Continuum Surlite III, are being aligned to set up two-pulse LIBS experiment. The Continuum Surlite III based LIBS system was modified and tested in the laboratory and also used to take LIBS data at SSC during DIAL field measurements at SSC.

Development of Tools for Long-term Monitoring

Monitoring plant physiological status in contaminated environments by high-resolution spectral imaging. During the month of June, Brassica juncea was planted in pots on mobile plant racks constructed by the DIAL machine-shop. The plants are growing well and will be treated with selected metal species (Cd and Zn). A portable spectroradiometer system will be used to monitor the metal uptake process. The seeds of another selected plant species, barley, were put on back-order by the supplier. Planting of barley will begin when the seeds arrive.

Design, fabrication and development of a portable miniature ion trap mass spectrometer. This project is scheduled to begin in the fall. Preliminary procurement arrangements are being investigated. Possible cost savings can be achieved through federal surplus list.

Moisture fiber-optic diode laser sensor. The bare portion of the fiber was coated with an aqueous solution of just CoCl₂, to go to lower relative humidity, as it was thought that probably PVA is preventing a better interaction between the light guided by the fiber and CoCl₂. Various CoCl₂ concentrations were tried. It was found that, with high CoCl₂ concentrations, the sensor responds to relative humidity above 60%. The response time was very little and was also reversible. But, the pure CoCl₂ coating was found to be very brittle and could be easily taken off the fiber by the touch of the hand. Also, the insertion loss of the fiber increases with a pure CoCl₂ coating, as there is more scattering loss from the fiber surface. These two properties rule out pure CoCl₂ for long-term monitoring. Other ways of larger interaction with the light propagating in the fiber making a bent probe are under investigation.

Application of Imaging Techniques: thermal imaging. On-line image pixel correction, using the obtained bad pixel correction mask, has been completed. The literature search for the new graphical file format, portable network graphic (PNG), continued. Coding for accessing the PNG file description header is underway. The PNG format is used for DIAL's non-8-bit monochrome cameras. A high-speed image acquisition system was deployed for the Plexiglas combustion furnace measurements at the Stennis Space Center. Initial analysis on the acquired images has begun.

Effort will continue on: (1) establishing the computer-controlled exposure time settings for the NIR InGaAs camera, (2) investigating a new graphical file format, (3) modifying thermal calibration and system software using a high-resolution visible digital camera, and (4) analyzing images from the Plexiglas combustion furnace measurements. Manpower shortages could slow progress on this task.

Application of imaging techniques: profilometry. The development of imaging analysis software, with the new version of the driver system, for the FTP system continued. We also continued the study on the phase unwrapping algorithms for target areas with large height discontinuities and/or surface isolations.

Application of imaging techniques: spectral imaging. We made progress on upgrading and optimizing our image collection and analysis program package. The system has been tested in our lab and will be applied to the spectral imaging study of our ICP system. The UV AOTF manufacturer has informed us that, because of insurmountable technical difficulties, they could not deliver the system we ordered. The purchase order was canceled, and we are searching for an alternative to replace the UV AOTF system.

Application of imaging techniques: data mining. We have examined many of the reference spectral data at the EPA site, including both calculated and measured spectra. Each spectrum is very large - over 33 k points. This poses some problem in loading them into the SYSTAT software package from SPSS. We are looking at different approaches to reduce the data volume to a manageable size without any loss of interesting information.

We have decided to start with a principal component analysis-based algorithm for identifying a measured spectrum by matching it with the reference spectra.¹ The algorithm is prepared. We are in the process of developing programs to implement the algorithm. We have also developed a Web-based user interface to download desired spectra from the site. This can be easily adapted for other sites.

The limitation of SYSTAT to deal with data of huge dimensionality could be a problem. Manpower and hardware needs could also be a hindrance; however, the project is on schedule at this time.

1. P. Vandenabeele, A. Hardy, H.B.M. Edwards, and L. Moens. 2001. Evaluation of principal component based searching algorithm for Raman spectroscopic identification of organic pigments in 20th century artwork. Applied Spectroscopy, 56:5.

Hanford Tank Waste Chemistry

Saltcake Dissolution. Additional ESP calculations were performed on the Na-SO₄-CO₃-OH system at 25 and 50°C and solutions have been prepared. Similar calculations have begun on the Na-F-PO₄-OH-NO₃ system. Data from the later system will be compared to the work performed previously without nitrate. The experimental study on the Na-F-NO₃-OH system was completed. Model predictions were found to be in excellent agreement with the experimentally determined concentrations in water and at 25°C. On an increase in the hydroxide loading, both the fluoride and nitrate ion solubility was found to decrease in agreement with the model predictions. Regression analysis of this data is planned. Regression analysis for the Na-F-SO₄ system continued. Like ion interactions are being incorporated.

Further simulations of the BY-109 saltcake dissolution experiments were performed. Earlier results indicated that both fluoride and sulfate concentrations predicted by the model take on constant values between 100 and 150 cumulative weight percent dilutions. This result is at odds with the experimental data, and the effect of additional dilutions in this range were investigated to confirm the original model calculations. Like results were obtained. The model error has been traced to inaccurate partitioning between the NaF and Na₃FSO₄ solids. Further comparisons with solids identification studies are in progress.

Prevention of solids formation. Saltwell pumping flow loop data, obtained at initial SX-104 supernatant surrogate velocities of 15 and 8 cm/sec, were compared. Normalization of the data to the time at which the plug forms allowed a direct comparison of the pressure and velocity profiles. Both traces were similar. A two-phase flow model was successfully adopted for the increase in pressure as the particles accumulate in the channel. Velocities determined from the analysis of images collected during the experiment indicated four distinct regimes, free particle flow, agglomeration and deposition, development of a moving bed, and finally plug formation. Flow stream temperatures were in excellent agreement with predictions based on an unsteady-state heat transfer model. For this particular surrogate composition, the main driving force appears to be the growth of the particles and the associated fluid velocities. Particle growth rates and ultimate dimensions were found to be the same for both runs. Thus, the time needed to form a complete plug is based strictly on the initial velocity. Additional experiments are in progress to examine particle growth rates and flow behavior at different phosphate loadings.

Work on the development of a three-dimensional surface plot correlating transport and waste parameters is in progress. Results of the literature search conducted last month have allowed the establishment of limits for parameters such as density, viscosity, and particle size distribution range. Initial simulations at a distance of 250 meters have been started. A new version of the software is expected next month. This version will allow for grid acceleration thereby improving convergence times, and permitting longer sections of transport pipe to be modeled.

Environmental Control Device Testing

HEPA filter testing. A first draft of Section 4 of the Quality Assurance Test Plan was completed and circulated to members of the HEPA Technical Work Group. After review and comment by the NTW, a second draft of this section was written and also reviewed by the group. In preparing for the ASME peer review of the document, it was decided that an overview of the testing to be done should be added to the documentation being reviewed in order to aid the reviewers in gaining full understanding of the entire project. Summary versions of Section 5, "Failure Mode vs. Minimum Detection Limit Testing" and Section 6, "Source Term Testing", are currently being written and will be sent to the members of the NTW for review and comment.

Process Monitoring and Control of Toxic Organics

Toxic organic compound monitoring using cavity ringdown spectroscopy. Optimization of the diode laser cavity ringdown system performance continued throughout July. The calibration of the system response for a given organic species (such as toluene, chlorobenzene, or benzene) remains constant over a few hours but tends to drift slightly on longer time scales. We are investigating the effects of slight variations in the electronic baseline on the mathematical routines used to fit our exponential decay waveforms and the potential for loss of analyte due to coating on the vacuum system surfaces. Other than this slight problem, the system is functioning with the expected sensitivity.

Construction of the supersonic jet expansion system for dioxin detection has begun. The frame for the system is in place near the laser system, and the system is being assembled as components arrive. Additional laboratory preparations for this new experiment are underway to provide water and power for the laser system and vacuum system.