At the Rocky Flats Environmental Technology Site (RFETS), the D&D task is enormous. Tons of plutonium has been processed over the years in approximately 1,000 gloveboxes, This represents nearly half of the gloveboxes in the DOE complex. In addition, more than a thousand tanks of various designs, with miles of associated piping, supported the processes. A wide variety of operations were performed at RFETS, including aqueous processing, pyrophoric processing, hydriding and dehydriding, metal casting, and machining of plutonium. Various materials have been handled at the facility, including plutonium, uranium, americium, tantalum, beryllium, chloride salts, and various acids and solvents. Significant amounts of plutonium residues remain in inaccessible equipment in the facilities, which create criticality safety issues. Some of the plutonium has been at RFETS for many years, and there is significant in-growth of americium, a decay product that emits gamma radiation, which potentially increases exposure to the workers. The size reduction portion of the D&D will be difficult and costly. The gloveboxes and tanks are constructed of stainless steel, frequently with lead shielding or double walls that hold water for neutron shielding. Window mountings, glove port rings, site gages, bolted flanges, and various penetrations reinforce the walls. Tanks may be …

The development of hydrogen transport ceramic membranes offers increased opportunities for hydrogen gas separation and utilization. Commercial application of such membranes will most likely take place under conditions of elevated temperature and pressure, where industrial processes producing and or utilizing hydrogen occur, and where such membranes are theoretically expected to have the greatest permeability. Hydrogen separation membrane performance data at elevated temperature is quite limited, and data at elevated pressures is conspicuously lacking. This paper will describe the design, construction, and recent experimental results obtained from a membrane testing unit located at the U.S. Department of Energy's Federal Energy Technology Center (FETC). The membrane testing unit is capable of operating at temperatures up to 900 C and pressures up to 500 psi. Mixed-oxide ceramic ion-transport membranes, fabricated at Argonne National Laboratory (ANL), were evaluated for hydrogen permeability and characterized for surface changes and structural integrity using scanning electron microscopy/X-ray microanalysis (SEM/EDS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), as a function of temperature, pressure, and hydrogen exposure.

Using the CRYRing Facility in Stockholm Coupled with an MCP-CCD detector, and a differential stopping foil, we have determined dynamic parameters in the three-body dissociative recombination of H₂O⁺. These include the distribution between the O(³P) and O(¹D) channels, the distribution of H atom recoil energies in the O(³P) channel and the distribution of angles between the two departing H atoms.

The aqueous complexation reactions of trivalent lanthanide and actinide cations with the hexadentate ligand N,N,N{prime},N{prime}-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), have been characterized using potentiometric and spectroscopic techniques in 0.1 M NaClO{sub 4} At 25 C, the stability constant of Am(TPEN){sup 3+} is two orders of magnitude larger than that of Sm(TPEN){sup 3+}, reflecting the stronger interactions of the trivalent actinide cations with softer ligands as compared to lanthanide cations.

The objective of this research is to develop a system capable of identifying speakers on wiretaps from a large database (>500 speakers) with a short search time duration (<30 seconds), and with better than 90% accuracy. Much previous research in speaker recognition has led to algorithms that produced encouraging preliminary results, but were overwhelmed when applied to populations of more than a dozen or so different speakers. The authors are investigating a solution to the "large population" problem by seeking two completely different kinds of characterizing features. These features are he techniques of Neuro-Linguistic Programming (NLP) and the continuous wavelet transform (CWT). NLP extracts precise neurological, verbal and non-verbal information, and assimilates the information into useful patterns. These patterns are based on specific cues demonstrated by each individual, and provide ways of determining congruency between verbal and non-verbal cues. The primary NLP modalities are characterized through word spotting (or verbal predicates cues, e.g., see, sound, feel, etc.) while the secondary modalities would be characterized through the speech transcription used by the individual. This has the practical effect of reducing the size of the search space, and greatly speeding up the process of identifying an unknown speaker. The wavelet-based line of …

This paper provides a brief review of experimental techniques for producing dynamic isentropic compression of samples to pressures of several hundred GPa. Traditional gun launch techniques include use of buffer plates, such as fused silica, that exhibit negative curvature to their stress-strain response and graded-density impactors. Graded-density impactors have been used to study isentropic compression of specimens to pressures exceeding 2 Mbar on high-impedance materials. A recent development includes the use of the Sandia Z Accelerator to produce magnetic compression in planar specimens to pressures of a few hundred kbar over time scales of 100 ns. These techniques have been successfully applied to isentropic compression of iron to 300 kbar and copper to 130 kbar. The iron results indicate that it is possible to study the polymorphic phase change that occurs at 130 kbar and also the kinetic properties of the transformation. The copper results indicate that with further improvements in progress it should be possible to measure continuous isentropic compression curves in materials of interest to pressures exceeding 1 Mbar. The Z accelerator is limited to peak currents of about 20 MA. By reconfiguring the anode-cathode geometry it should be possible to obtain constant current density and thus driving …

Hohlraums (measuring 6-mm in diameter by 7-mm in height) have been heated by x-rays from a z-pinch. Over measured x-ray input powers P of 0.7 to 13 TW, the hohlraum radiation temperature T increases from {approximately}55 to {approximately}130 eV, and is in agreement with the Planckian relation P-T{sup 4}. The results suggest that indirect-drive ICF studies involving NIF relevant pulse shapes and &lt;2-mm diameter capsules can he studied using this arrangement.

Structural and thermal properties of small lithium clusters are studied using ab initio-based Monte Carlo simulations. The ab initio scheme uses a Hartree-Fock/density functional treatment of the electronic structure combined with a jump-walking Monte Carlo sampling of nuclear configurations. Structural forms of Li{sub 8} and Li{sub 9}{sup +} clusters are obtained and their thermal properties analyzed in terms of probability distributions of the cluster potential energy, average potential energy and configurational heat capacity all considered as a function of the cluster temperature. Details of the gradual evolution with temperature of the structural forms sampled are examined. Temperatures characterizing the onset of structural changes and isomer coexistence are identified for both clusters.

Titanate ceramics have been selected for the immobilization of excess plutonium. The baseline ceramic formulation leads to a multi-phase assemblage, which consists of a majority pyrochlore phase plus secondary phases. The phase distribution depends on processing conditions and impurity loading. In this paper, we report on the characterization of the phase assemblage and distribution in titanate ceramics using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and x-ray dot mapping. Two titanate ceramics were studied a baseline ceramic and a ceramic with impurities. In the baseline ceramic, the secondary phases that were observed include zirconolite, brannerite, and rutile. Additional phases, such as perovskite, an Al-Ti-Ca phase, and a silicate phase, formed in the impurity ceramic. The distribution of these phases was characterized with backscattered electron (BSE) imaging, except for zirconolite. While the zirconolite exhibited weak contrasts in BSE images and could not be easily distinguished from the pyrochlore matrix, its distribution was effectively characterized with x-ray mapping. Quantitative analyses of BSE images and x-ray maps reveal that the impurity ceramic contains less brannerite, rutile, and pores than the baseline ceramic.

In 1993, members of our team collaborated with Silicon Graphics to perform the first full-scale demonstration of the computational power of the SMP cluster supercomputer architecture. That demonstration involved the simulation of homogeneous, compressible turbulence on a uniform grid of a billion cells, using our PPM gas dynamics code. This computation was embarrassingly parallel, the ideal test case, and it achieved only 4.9 Gflop/s performance, slightly over half that achievable by this application on the most expensive supercomputers of that day. After four to five solid days of computation, when the prototype machine had to be dismantled, the simulation was only about 20% completed. Nevertheless, this computation gave us important new insights into compressible turbulence and also into a powerful new mode of cost-effective, commercially sustainable supercomputing [S]. In the intervening 6 years, the SMP cluster architecture has become a fundamental strategy for several large supercomputer centers in the US, including the DOE's ASCI centers at Los Alamos National Laboratory and at the Lawrence Livermore National Laboratory and the NSF's center NCSA at the University of Illinois. This SMP cluster architecture now underlies product offerings at the high-end of performance from SGI, IBM, and HP, among others. Nevertheless, despite many …

Technical guidance for performance assessment (PA) of low-level radioactive waste (LLRW) sites is currently dependent upon experimental retardation factors (K{sub D}'s) to predict radionuclide transport. Accurate predictions of waste transport or retardation will require mechanistic models of radionuclide sorption so as to be applicable to a wide range of soil/groundwater environments. To that end, we have investigated Cs{sup +}, Sr{sup +}, and Ba{sup 2+} sorption on several clay and Fe-oxide minerals. Relative metal binding strengths for montmorillonite clay decrease from Ba{sup 2+} to Sr{sup +}, which is similar to that sorption trend noticed for kaolinite. Molecular dynamics simulations for kaolinite suggest that Cs{sup +} is sorbed at aluminol (010) edge sites as an inner-sphere complex and weakly sorbed as an outer-sphere complex on (001) basal surfaces. Sorption is thought to occur on similar sites for smectite clays, however, the basal plane residual charge and its increased basal plane exposure should have a greater influence on metal sorption. On the other hand, phase transformation kinetics (e.g., ferrihydrite to goethite) is a very important control of metal sorption and resorption for Fe-oxides/hydroxides. These results provide a basis for understanding and predicting metal sorption on complex soil minerals.

Lawrence Livermore National Lab and Sandia National Laboratories, CA are collaborating on the development of new techniques to study damage evolution and growth in material specimens subjected to mechanical loading. These techniques include metallography, radiography, computed tomography (CT) and modeling. The material specimens being studied include cast magnesium and aluminum alloys, and forged stainless steel. The authors concentrate on characterizing monotonically loaded Mg alloy specimens using CT. Several notched tensile specimens were uniaxially loaded to different percentages of the failure load. Specimens were initially characterized by radiography and computed tomography to determine the preloaded state. Subsequent CT scans were performed after the samples were loaded to different percentages of the load failure. The CT volumetric data are being used to measure void size, distribution and orientation in all three dimensions nondestructively to determine the effect of void growth on the mechanical behavior of the materials.

We have investigated the performance of a position-sensitive, gamma-ray detector based on a CsI(Na) scintillator coupled to a Hamamatsu R3292 Position-Sensitive Photomultiplier Tube (PSPMT). The R3292 has an active area 10.0 cm in diameter (quoted). Utilization of the full active area of the photocathode is a goal that has been previously unrealized due to edge effects. Initial measurements with a 0.75 cm thick CsI(Na) crystal indicate that the performance (position resolution linearity) starts to degrade as one reaches a radius of only 3.5 cm, reducing the active area by 60%. Measuring the anode wires we have found that this fall off is not solely due to crystal edge effects, but rather is inherent to the tube crystal system. In this paper we describe the results of our measurements and how good performance can be maintained across a full 10cm of the tube face through the use of a few additional electronics channels.