Dallas D. Hill

Performance of Fiber-Optic Raman Probes for Analysis of Gas Mixtures in Enclosures

The feasibility of using fiber-optic Raman probes to identify and quantify gases in enclosures is investigated by measuring and comparing detection thresholds using several probe and enclosure designs. Unfiltered, non-imaging, fiber-optic probes are shown to achieve lower detection thresholds than a filtered, imaging, fiberoptic probe, provided that light scattering within the sample enclosure is minimized and provided that a window is not used between the probe and the analyte gas. Achievable thresholds for hydrogen, oxygen, nitrogen, carbon monoxide, and methane in gas mixtures are demonstrated to be below 1 kPa with ten seconds signal acquisition and 0.1 kPa with twenty minutes signal acquisition with the use of 0.4 W of 532-nm excitation. Ambient carbon dioxide in air (.03 kPa) is shown to be detectable in a twenty minute acquisition, and ambient water vapor is well above the detection threshold. Background signals generated within the optical fibers remain the principal factors limiting detection thresholds. Factors affecting the magnitudes of these signals reaching the detector are investigated and discussed. A flat piece of light-absorbing colored glass tilted to direct reflected light away from the fiber-optic probe performs well as a beam stop to reduce background signal in a simple, cylindrical sample enclosure.

PARTICULATE CAPTURE OF PLUTONIUM BY HIGH GRADIENT MAGNETIC SEPARATION WITH ADVANCED MATRICES

A high performance superconducting magnetic separator is being developed for near single particle retrieval from low concentration field collected samples. Results show that maximum separation is obtained when the effective matrix element diameter approaches the diameter of the particles to be captured. Experimentally, we were able to capture very dilute levels of 0.2 to 0.8 μm PuO2 particles with dodecane as a carrier fluid. The development of new matrix materials is being pursued through the deposition of nickel dendrites on an existing stainless steel matrix material. The new materials are promising for the submicron collection of paramagnetic particles. Results indicate that these new matrices contain a high number of capture sites for the paramagnetic particles. We have also derived a force-balance model that uses empirically determined capture cross section values. The model can be used to optimize the capture cross section and thus increase the capture efficiency. This enables the prediction of high gradient magnetic separator performance for a variety of materials and applications.

Magnetic separation for environmental remediation

Magnetic separation is a physical separation process that segregates materials in a mixture on the basis of magnetic susceptibility. Because all actinides and their compounds and fission products are paramagnetic, and most host materials such as water, graphite, soil, and sand are diamagnetic, magnetic separation methods can be used to extract the actinides from these hosts, concentrating the toxic materials into a low volume waste stream. The technology relies only on physical properties, and therefore separations can be achieved while producing little or no secondary waste.

Apparatus for Testing Rotating Heat Pipes

*† ‡ A test apparatus, that will be used to study the heat transfer performance of rotating heat pipes, has been designed and built. The apparatus allows for simultaneous testing of a pair of crank-shaped rotating heat pipes operating near room temperature. The test rig is designed to support heat pipes with an on-axis rotating condenser section, an off-axis eccentrically rotating evaporator section, and a curved adiabatic section. Due to the length of the heat pipes (55”), the distance from the axis of rotation to the off-axis evaporator section (9.5”), and the maximum rotation speed (5500 rpm), care had to be taken in the design of a substantial support structure for the heat pipes, the selection of a drive system, and the design of the mounting frame. These design issues, as well as safety considerations associated with the test apparatus, are discussed here. Preliminary test data for stationary and low-speed tests are also presented.

CAPTURE AND RETRIEVAL OF PLUTONIUM OXIDE PARTICLES AT ULTRA-LOW CONCENTRATIONS USING HIGH-GRADIENT MAGNETIC SEPARATION

A high-gradient magnetic separation system has been developed for capture and retrieval of ultra-low plutonium oxide concentrations. The application of advanced matrix materials and improved methodology has demonstrated the effective collection and recovery of submicron paramagnetic actinide particles with particle concentrations as low as 10−23 M. Incorporation of multiple passes during recovery of magnetically captured particles improves the system mass balance. Activity balances for plutonium were verified with stringent sampling protocols. Collection and recovery values demonstrate that 99% of the submicron plutonium oxide particles can be accounted for when recycle loops are incorporated into capture and recovery circuits, magnetically captured particles are released by sonication, carrier fluids are organically based, and longer matrix lengths are utilized.

Magnetic Separation for Rare Earth Oxide Recovery at Sillamä, Estonia

In summary, we have shown that magnetic separation can be used to concentrate rare earth oxides or actinides from extraneous materials yielding more efficient recovery and treatment operations. We have demonstrated that the extraction and concentration of paramagnetic actinides (PuO2, UO2, etc.) from soils is feasible, where our actinide separation results have shown that HGMS is effective for extracting >90% of small radioactive particles from soil slurries. In addition, recovery of rare earth oxides such as Pr2O3, Gd2O3, and Ce2O3 has successfully been demonstrated by HGMS and MRS. Analytical models were developed that describe both magnetic separation process. The model provides guidance in selecting the appropriate bench scale experiments to perform and assists in analyzing the resulting data. A validated analytical model also supports prototype design and process scaleup. We anticipate that with proper pretreatment, mainly consisting of size reduction, a permanent magnet roll separator will be the method of choice for recovery of rare-earth oxides. While magnetic separation cannot extract diamagnetic products (such as La2O3) from the soils, we expect that over 90% of paramagnetic rare earth oxide components can be extracted efficiently and economically.

Surveillance and Monitoring Program Full-Scale Experiments to Evaluate the Potential for Corrosion in 3013 Containers

A set of six long-term, full-scale experiments were initiated to determine the type and extent of corrosion that occurs in 3013 containers packaged with chloride-bearing plutonium oxide materials. The materials were exposed to a high relative humidity environment representative of actual packaging conditions for the materials in storage. The materials were sealed in instrumented, inner 3013 containers with corrosion specimens designed to test the corrosiveness of the environment inside the containers under various conditions. This report focuses on initial loading conditions that are used to establish a baseline to show how the conditions change throughout the storage lifetime of the containers.

Magnetic Separation for Nuclear Material Surveillance

A high performance superconducting magnet is being developed for particle retrieval from field collected samples. Results show that the ratio of matrix fiber diameter to the diameter of the captured particles is an important parameter. The development of new matrix materials is being pursued through the controlled corrosion of stainless steel wool, or the deposition of nickel dendrites on the existing stainless steel matrix material. We have also derived a model from a continuity equation that uses empirically determined capture cross section values. This enables the prediction of high gradient magnetic separator performance for a variety of materials and applications. The model can be used to optimize the capture cross section and thus increase the capture efficiency.

Surveillance of sealed containers with plutonium oxide materials (ms163)

DOE is embarking upon a program to store large quantities of plutonium-bearing materials for up to fifty years. Materials destined for long-term storage include metals and oxides that are stabilized and packaged according to the DOE storage standard, where the packaging consists of two nested, welded, stainless steel containers. We have designed instrumented storage containers that mimic the inner storage can specified in the 3013 standard at both full- and small-scale capacities (2.4 liter and 0.005 liter, respectively), Figures 1 and 2. The containers are designed to maintain the volume to material mass ratio while allowing the gas composition and pressure to be monitored over time.

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.