Steven J. Buelow

Pulsed molecular-beam, diode-laser spectrometry using rapid scanning techniques

We describe a diode‐laser spectrometer for obtaining direct absorption, rovibrational spectra of monomers and/or weakly bound, molecular complexes which are found in supersonic expansions. The spectrometer incorporates a tunable, semiconductor diode‐laser source and a pulsed‐gas slit nozzle. White cell optics are used in the vacuum chamber to increase effective path length, and a Fabry–Perot etalon is used for relative frequency calibration. Stabilization of the source output is accomplished by locking onto a zero crossing of the etalon fringe‐spacing pattern with a gated integrator. The diode laser is scanned rapidly (∼0.2 cm−1/ms) to modulate absorption signals at frequencies which can be electronically filtered from source noise. For 2000 scans, absorbances as small as 1.3×10−5 (0.003% absorption) can be detected. Amplitude fluctuations in the detected signal due to interference effects in the optics and gain variations in the diode laser are eliminated by recording data with and without gas flow from ...

The solubility of 1:1 nitrate electrolytes in supercritical water

Abstract A novel method was developed for determining the solubility of sodium nitrate in water solutions at pressures ranging from 248 to 300 bar and temperatures from 450 to 525°C. Sodium nitrate solubilities determined by this method ranged from 293 mg kg −1 at 248 bar and 525°C to 1963 mg kg −1 at 300 bar and 450°C. A simple hydration mechanism was used to model the data. In addition, solubilities were determined for potassium and lithium nitrate salts to assess the effect of ion size on solubility. These experiments determined that the solubility was proportional to the ion size, so that solubility decreased in the order LiNO 3 > NaNO 3 > KNO 3 . These studies were motivated by applications for sodium nitrate in hydrothermal treatment methods, especially supercritical-water oxidation.

Hydrothermal oxidation of radioactive combustible waste

Abstract A hydrothermal processing system was designed, built and tested for treatment of transuranic combustible material. The operation is performed in a plutonium glovebox. Presented in this paper are results from the study of the hydrothermal oxidation of plutonium and americium contaminated organic wastes. The use of thermal liquefaction, via pyrolysis, to prepare solid materials for hydrothermal processing was tested and compared to the pumping of slurries of small particle sized solids (ion exchange resin). Experiments show that the hydrothermal process converts greater than 99.9% of the organic component to CO 2 and H 2 O, with 30 wt% H 2 O 2 as an oxidant, at 540°C and 46.2 MPa. The majority of the actinide component forms insoluble products that are easily separated by filtration. A titanium liner in the reactor and heat exchanger provides corrosion resistance for the oxidation of chlorinated organics.

Electrical Conductances of Aqueous Solutions of Inorganic Nitrates at 25-505 C and 100-490 Bar

Abstract A simple Pt electrode was used to determine the electrical conductances of 0.00393, 0.00992 and 0.0379 m NaNO3 and 0.00911 m LiNO3, 0.00910 m CsNO3 and 0.00946 m Ca(NO3)2 solutions. Temperatures ranged from 25 to 505°C at pressures ranging from 100 to 490 bar. The electrode was calibrated against the conductance of 0.010 m hydrothermal NaCl solutions. Preliminary limiting equivalent conductances and dissociation constants were obtained for hydrothermal NaNO3 solutions. The alkali nitrate series behaved similarly to the alkali chloride series: the electrical conductance decreases with decreasing cation radius. This seemingly paradoxical result is due to the stronger electric field and hence the greater tendency for ion pairing and larger solvation spheres associated with smaller cations. Nearly complete ion association is observed at low-density supercritical conditions. Maximum conductances were obtained at about 300°C and densities increasing from about 500 kg m−3 to 725 kg m−3 with increasing concentration. Limiting conductances and pKa values for NaNO3 solutions were similar to those for NaCl solutions, with NaNO3 being the weaker electrolyte. Ca(NO3)2 conductances follow similar trends to K2SO4. The data suggests that nearly complete dissociation occurs below 200°C, but that appreciable association to form monovalent cations occurs at higher temperatures.

Destruction of halogenated organics with hydrothermal processing

Chemical reactions in high temperature water (hydrothermal processing) allow new avenues for effective waste treatment and radionuclide separation. Successful implementation of hydrothermal technologies offers the potential to effectively treat many types of radioactive waste and reduce the storage hazards and the disposal costs, while minimizing the generation of hazardous secondary waste streams.1–5 Halogenated hazardous organic liquids containing actinides are a difficult to treat category of TRU radioactive wastes. These liquids are typically used for degreasing operations or density measurements and can include trichlorethylene and bromobenzene. Experiments have demonstrated that hydrothermal processes can eliminate hazardous halogenated organics generated by the nuclear industry by the complete oxidation of the organic components to CO2 and H2O.

Enhanced Sludge Processing of HLW: Hydrothermal Oxidation of Chromium, Technetium, and Complexants by Nitrate

The objective of this project is to develop the scientific basis for hydrothermal separation of chromium from High Level Waste (HLW) sludges. Our worked is aimed at attaining a fundamental understanding of chromium speciation, oxidation/reduction and dissolution kinetics, reaction mechanisms, and transport properties under hydrothermal conditions in both simple and complex salt solutions that will ultimately lead to an efficient chromium leaching process.

Rovibrational Spectroscopy of ArCo Van Der Waals Complex

The information that can be obtained from the high resolution rovibrational spectra of small molecular clusters is very useful for determining intermolecular potentials and the effects of intermolecular interactions on intramolecular bonds. Recently, such spectra have been obtained via absorption measurements using F-center, frequency difference and diode laser sources. Because F-center and frequency difference lasers operate best in the 2-4 ..mu..m region, studies using these laser sources have involved high frequency vibrational modes (H-X, X-C,F,Cl,Br) or overtones. Although diode lasers cover a much broader spectral range (3-20 ..mu..m), they are less convenient to use for doing survey spectroscopy. We have developed several new techniques which improve the sensitivity and convenience of absorption measurements using diode lasers for the study of molecular clusters in supersonic expansions. Here we describe these techniques and their application for the measurement of the rovibrational spectra of ArCO near 5 ..mu..m. 11 refs., 4 figs., 1 tab.