ES950745IX Abstract published in Advance ACS Abstracts, May 15, 1996.

No abstract

In uncontaminated natural materials, plutonium and technetium exist exclusively as products (daughters) of nuclear reactions in which uranium is the principal reactant (parent). Under conditions of chemical stability over geologic periods of time, the relative abundances of daughter and parent elements are fixed by the rates of nuclear reactions and the decay of the daughter radionuclide. The state of this nuclear secular equilibrium condition is the primary basis of the geochemical study of these elements in nature. Thus, it is critical that nuclear parent and daughter abundances are measured in the same sample. We have developed a quantitative procedure for measuring subpicogram quantities of plutonium and technetium in gram quantities of geologic matrices such as uranium ores. The procedure takes advantage of the aggressive properties of sodium peroxide/hydroxide fusion to ensure complete dissolution and homogenization of complex materials, the precision provided by isotope dilution techniques, and the extreme sensitivity offered by thermal ionization mass spectrometry. Using this technique, a quantitative aliquot can be removed for uranium analysis by isotope dilution thermal ionization mass spectrometry or α spectrometry. Although the application of the procedure is unique, the analytical concepts may find more general application in studies of environmental contamination by nuclear materials. To assess the precision and accuracy of the analytical results, blanks and standards were analyzed routinely for a 1-year period to ensure quality control of our sample analyses. The average technetium blank is 5 ± 4 fg (n = 8), and that for plutonium is 0.17 ± 0.15 pg (n = 7). Thus, the detection limit for technetium (defined as 3 times the standard deviation of the average blank) is 11 fg, and that for plutonium is 0.44 pg. To assess the procedural precision, Canadian Reference Material BL-5 was analyzed routinely with samples. The results of seven replicate analyses for technetium in this standard reference material yield a technetium concentration of 59.0 fg/g, with a remarkably small standard deviation of 0.6 fg, 1.0% of the average value. The results of six replicate analyses for the concentration of plutonium in BL-5 give 1.012 pg/g, with an equally small standard deviation of 0.016, 1.6% of the average value. No direct measure of accuracy can be done on the technetium or plutonium analyses, because no standard reference material exists for these elements. To help constrain the accuracy of our measurements, equilibrium technetium/uranium and plutonium/uranium abundances were calculated using the nuclear reaction code MCNP. For technetium, such calculations are relatively insensitive to variations in model parameters, and measurements fall within a 21% high/low bias. For plutonium, the calculations are very sensitive to model parameters and hence inherently less precise. Indirectly, spike and isotope mix calibrations made from weighted quantities of certified isotopes (both technetium and plutonium) can be used t...

This progress report describes new experimental results and interpretations for data collected from October 1,1992, through September 30,1993, as part of the Characterization Task of the Uranium in Soils Integrated Demonstration of the Office of Technology Development, Office of Environmental Restoration and Waste Management of the US Department of Energy. X-ray absorption, optical luminescence, and Raman vibrational spectroscopies were used to determine uranium speciation in contaminated soils from the US Department of Energy's former uranium production facility at Fernald, Ohio (18 mi northwest of Cincinnati). These analyses were carried out both before and after application of one of the various decontamination technologies being developed within die Integrated Demonstration. The treatment technologies included soil washes with carbonate, citrate, Tiron, and Tiron/dithionite mixtures. This year the program focused on characterization of the uranium speciation remaining in the soils after decontamination treatment. X-ray absorption and optical luminescence spectroscopic data were collected for approximately 40 Fernald soil samples, which were treated by one or more of the decontamination technologies. Results for the A-series soils from the Incinerator Area suggest that the treated soils can be divided into three sets. The first set comprises control samples that are little changed from the untreated soils. The second set encompasses most of the A-series samples. The uranium remaining in these soils appears to have a slightly higher ratio of tetravalent to hexavalent uranium than the untreated soils. Determining Uranium Specfatkxi in Femald Soils have. The third set consists of only All soils that were treated by Tiron, carbonate, o? both, but with no reducing agent. This set appears to have the highest ratio of tetravalent to hexavalent uranium remaining in the soil for any sample examined thus far. Observation of different x-ray absorption spectra in the second and thud sets suggests that there are several uranium species-rather than a single intransigent species-left in the soils following treatment and that the treatment chemistry may be dictating the difference in the remnant species. The treated B-series soils from the Plant 1/Storage Pad Area are less easily categorized. However, from the usual x-ray absorption criteria, it appears that they retain primarily hexavalent uranium following the treatments. The optical luminescence data demonstrate that there is a decrease in size (and probably quantity) of the particulate hexavalent uranium that gives rise to the green emission. Thus, all treatment technologies do seem to lead to a more dispersed, finer grained contamination. Some instances of particulate green emission still exist in these samples, and the spectral band structure suggests that this is attributable to a schoepite phase. An orange emissive phase, also seen in many samples, is probably attributable to a hexavalent uranium species, but its identity has not been confirmed. New Raman and luminesc...

The instrumentation, the luminescence microprobe, and synchronously scanned luminescence spectroscopy technique described here can be used to classify microliter quantities of oil such as those in fluid inclusions in cements from petroleum reservoirs. It is primarily constructed to obtain synchronously scanned luminescence spectra from microscopic sized samples to characterize the organic classes of compounds that predominate. At present no other technique can so readily analyze a single oil-bearing fluid inclusion. The data collected from the technique are pertinent to evaluating systems and providing quantitative data for solving problems in oil migration and maturation determinations, oil-to-oil and oil-to-source correlations, oil degradation, and episodes and chemistry of cementation.