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At least 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Quantum Monte Carlo calculations of two neutrons in finite volume

Ab initio calculations provide direct access to the properties of pure neutron systems that are challenging to study experimentally. In addition to their importance for fundamental physics, their properties are required as input for effective field theories of the strong interaction. In this work, we perform auxiliary-field diffusion Monte Carlo calculations of the ground state and first excited state of two neutrons in a finite box, considering a simple contact potential as well as chiral effective field theory interactions. We compare the results against exact diagonalizations and present a detailed analysis of the finite-volume effects, whose understanding is crucial for determining observables from the calculated energies. Finally, using the Lüscher formula, we extract the low-energy S-wave scattering parameters from ground- and excited-state energies for different box sizes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Self-consistent theory of finite Fermi systems and Skyrme–Hartree–Fock method

Recent results obtained on the basis of the self-consistent theory of finite Fermi systems by employing the energy density functional proposed by Fayans and his coauthors are surveyed. These results are compared with the predictions of Skyrme–Hartree–Fock theory involving several popular versions of the Skyrme energy density functional. Spherical nuclei are predominantly considered. The charge radii of even and odd nuclei and features of low-lying 2{sup +} excitations in semimagic nuclei are discussed briefly. The single-particle energies ofmagic nuclei are examined inmore detail with allowance for corrections to mean-field theory that are induced by particle coupling to low-lying collective surface excitations (phonons). The importance of taking into account, in this problem, nonpole (tadpole) diagrams, which are usually disregarded, is emphasized. The spectroscopic factors of magic and semimagic nuclei are also considered. In this problem, only the surface term stemming from the energy dependence induced in the mass operator by the exchange of surface phonons is usually taken into account. The volume contribution associated with the energy dependence initially present in the mass operator within the self-consistent theory of finite Fermi systems because of the exchange of high-lying particle–hole excitations is also included in the spectroscopic factor. The results of the first studies that employed the Fayans energy density functional for deformed nuclei are also presented.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2014

Energy Storage

Energy storage technology is critical if the U.S. is to achieve more than 25% penetration of renewable electrical energy, given the intermittency of wind and solar. Energy density is a critical parameter in the economic viability of any energy storage system with liquid fuels being 10 to 100 times better than batteries. However, the economical conversion of electricity to fuel still presents significant technical challenges. This project addressed these challenges by focusing on a specific approach: efficient processes to convert electricity, water and nitrogen to ammonia. Ammonia has many attributes that make it the ideal energy storage compound. The feed stocks are plentiful, ammonia is easily liquefied and routinely stored in large volumes in cheap containers, and it has exceptional energy density for grid scale electrical energy storage. Ammonia can be oxidized efficiently in fuel cells or advanced Carnot cycle engines yielding water and nitrogen as end products. Because of the high energy density and low reactivity of ammonia, the capital cost for grid storage will be lower than any other storage application. This project developed the theoretical foundations of N 2 catalysis on specific catalysts and provided for the first time experimental evidence for activation of Mo 2 N based catalysts. Theory also revealed that the N atom adsorbed in the bridging position between two metal atoms is the critical step for catalysis. Simple electrochemical ammonia production reactors were designed and built in this project using two novel electrolyte systems. The first one demonstrated the use of ionic liquid electrolytes at room temperature and the second the use of pyrophosphate based electrolytes at intermediate temperatures (200 – 300 ºC). The mechanism of high proton conduction in the pyrophosphate materials was found to be associated with a polyphosphate second phase contrary to literature claims and ammonia production rates as high as 5X 10-8 mol/s/cm 2 were achieved.

25 ENERGY STORAGE↗
DOE OSTI2025

CO 2 in Ionene–Ionic Liquid Composite Membranes

Abstract Ionene – ionic liquid (IL) composites are promising materials for CO 2 separation, yet a molecular‐level understanding of their structure and its impact on CO 2 speciation, solubility, rotation, and diffusivity remains unclear. Herein, using multimodal nuclear magnetic resonance (NMR), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), atomic force microscopy (AFM), and molecular dynamics (MD) simulations, we reveal that the composites contain IL‐rich domains extending across hundreds of nanometres within the ionene matrix, and these bicontinuous domains span the entire membrane depth. CO 2 also absorbs into the ionene matrix, with the distribution between two CO 2 species varying with temperature and time. The rotational correlation times of these two species are on the timescale of 0.1 and 1 ns, respectively. As IL content increases, the ionic domains expand, resulting in higher CO 2 solubility due to enhanced molecular dynamics and increased free volume in both ionene backbones and IL‐rich regions. Although CO 2 diffusion in the membranes is an order of magnitude slower than in bulk IL, the activation energy for CO 2 diffusion remains comparable. Ionene‐IL composites represent a promising platform for designing CO 2 separation membranes, offering enhanced CO 2 diffusion and selectivity through IL‐rich domains, and increased CO 2 solubility and mechanical integrity from the ionene matrix.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Scalable Synthesis of Cholesteric Glassy Liquid Crystals

Capable of non-absorbing circular polarization of unpolarized incident light, cholesteric glassy liquid crystals consisting of hybrid chiral-nematic pendants to volume-excluding cores are potentially useful for the fabrication of various robust optical devices. As illustrated in this study, the well-oriented glassy film of enantiomeric Bz3ChN, with a glass transition at 73 °C and a cholesteric-to-isotropic transition at 295 °C, exhibits a selective reflection band centered at approximately 410 nm, an exceptional set of properties well suited for optical device exploration. To enable sustainable, large-scale synthesis of this material class for widespread applications, a productive strategy has been established, requiring a mere three-step scheme with an overall yield, atom economy, and reaction mass efficiency at 34%, 33% and 12%, respectively. Lastly, while amenable to improvements, the resultant green chemistry metrics are encouraging as the first attempt.

36 MATERIALS SCIENCE↗
NASA NTRS2010

Ionization-Assisted Getter Pumping for Ultra-Stable Trapped Ion Frequency Standards

A method eliminates (or recovers from) residual methane buildup in getter-pumped atomic frequency standard systems by applying ionizing assistance. Ultra-high stability trapped ion frequency standards for applications requiring very high reliability, and/or low power and mass (both for ground-based and space-based platforms) benefit from using sealed vacuum systems. These systems require careful material selection and system processing (cleaning and high-temperature bake-out). Even under the most careful preparation, residual hydrogen outgassing from vacuum chamber walls typically limits the base pressure. Non-evaporable getter pumps (NEGs) provide a convenient pumping option for sealed systems because of low mass and volume, and no power once activated. An ion gauge in conjunction with a NEG can be used to provide a low mass, low-power method for avoiding the deleterious effects of methane buildup in high-performance frequency standard vacuum systems.

Tjoelker, Robert L.↗
DOE OSTI2013

Longitudinal discharge pumped low-pressure XeCl laser

We have studied output parameters of a XeCl and a N{sub 2} laser pumped by a longitudinal discharge with automatic spark UV preionisation. The output parameters of a low-pressure (30 Torr) XeCl laser operating with Ar, Ne and He as buffer gases or with no buffer gas have been optimised for the first time. The laser generated 5-ns FWHM pulses with an average power of 0.5 mW and output energy of 0.15 mJ. Under longitudinal discharge pumping, an output energy per unit volume of 1.8 J L{sup -1} atm{sup -1} was reached using helium as a buffer gas. With argon-containing and buffer-free mixtures, it was 1.5 J L{sup -1} atm{sup -1}. The N{sub 2} laser generated 2.5-ns FWHM pulses with an average power of 0.35 mW and output energy of 0.05 mJ. (lasers)

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Effect of elastic anisotropy on thermally induced distortions of a laser beam in single cubic syngony crystals with radial cooling. Part I

We have studied thermally induced distortions of a beam in single cubic syngony crystals of all symmetry groups with an anisotropic elastic stiffness tensor. The arithmetic mean and the difference between the thermally induced phase incursions of eigenpolarisations, as well as the angle of incidence of these polarisations, are calculated for a long rod and a thin disk with radial cooling under uniform volume pumping of the active element. The position of the specific crystal orientations unrelated to its symmetry elements is investigated. The effective values of the thermo-optical constant Q in two specific orientations, as well as the thermo-optical constant P in an arbitrary orientation, are found. (invited paper)

36 MATERIALS SCIENCE↗
DOE OSTI2015

A versatile apparatus for the fine-tuned synthesis of cluster-based materials

In this paper, a custom-designed experimental setup for the fine-tuned synthesis of various cluster–based materials is presented. Providing custom-designed deposition stages and special sample holders it offers a high degree of control over the sample characteristics such as the cluster size, cluster amounts, and sample homogeneity in combination with high sample purity. The system is capable of producing thin films of pure clusters and various cluster-matrix combinations with cluster sizes ranging from single atoms up to aggregates of several thousand atoms. Two custom-designed deposition stages are available, one utilizes the full cluster beam, yielding micrograms of pure clusters within a few hours and the second one uses mass-separated clusters (mass-resolution between 2% and 10%), yielding nanograms of pure clusters in the same timescale. Furthermore, at the second deposition stage, a variety of matrix materials can be co-deposited at a controlled sample temperature between 153 K and 673 K. In order to prove the capabilities of the apparatus, a series of experiments with Fe clusters embedded in Ag matrices with different volume fractions of clusters were carried out. Energy dispersive X-ray spectroscopy measurements revealed that the amount of deposited clusters as well as the sample homogeneity can be controlled with an outstanding accuracy of 10%. Additional measurements of the magnetic properties indicated the presence of separated clusters for volume fractions of clusters around 2 volume percent (vol. %), while above this concentration (10 vol. %) a partial aggregation of the clusters was observed. It was also shown that the resulting thin films are nearly oxygen free, which ascertains that oxygen sensitive materials can be safely handled in this newly developed apparatus.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

The use of noncrystallographic symmetry averaging to solve structures from data affected by perfect hemihedral twinning

Molecular replacement and noncrystallographic symmetry averaging were used to detwin a data set affected by perfect hemihedral twinning. The noncrystallographic symmetry averaging of the electron-density map corrected errors in the detwinning introduced by the differences between the molecular-replacement model and the crystallized structure. Hemihedral twinning is a crystal-growth anomaly in which a specimen is composed of two crystal domains that coincide with each other in three dimensions. However, the orientations of the crystal lattices in the two domains differ in a specific way. In diffraction data collected from hemihedrally twinned crystals, each observed intensity contains contributions from both of the domains. With perfect hemihedral twinning, the two domains have the same volumes and the observed intensities do not contain sufficient information to detwin the data. Here, the use of molecular replacement and of noncrystallographic symmetry (NCS) averaging to detwin a 2.1 Å resolution data set for Aichi virus 1 affected by perfect hemihedral twinning is described. The NCS averaging enabled the correction of errors in the detwinning introduced by the differences between the molecular-replacement model and the crystallized structure. The procedure permitted the structure to be determined from a molecular-replacement model that had 16% sequence identity and a 1.6 Å r.m.s.d. for C{sup α} atoms in comparison to the crystallized structure. The same approach could be used to solve other data sets affected by perfect hemihedral twinning from crystals with NCS.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Synchrotron x-ray thermal diffuse scattering probes for phonons in Si/SiGe/Si trilayer nanomembranes

Nanostructures offer the opportunity to control the vibrational properties of via the scattering of phonons due to boundaries and mass disorder as well as through changes in the phonon dispersion due to spatial confinement. Advances in understanding these effects have the potential to lead to thermoelectrics with an improved figure of merit by lowering the thermal conductivity and to provide insight into electron-phonon scattering rates in nanoelectronics. However, characterizing the phonon population in nanomaterials has been challenging because of their small volume and because optical techniques probe only a small fraction of reciprocal space. Recent developments in x-ray scattering now allow the phonon population to be evaluated across all of reciprocal space in samples with volumes as small as several cubic micrometers. We apply this approach, synchrotron x-ray thermal diffuse scattering (TDS), to probe the population of phonons within a Si/SiGe/Si trilayer nanomembrane. The distributions of scattered intensity from Si/SiGe/Si trilayer nanomembranes and Si nanomembranes with uniform composition are qualitatively similar, with features arising from the elastic anisotropy of the diamond structure. The TDS signal for the Si/SiGe/Si nanomembrane, however, has higher intensity than the Si membrane of the same total thickness by approximately 3.75%. Possible origins of the enhancement in scattering from SiGe in comparison with Si include the larger atomic scattering factor of Ge atoms within the SiGe layer or reduced phonon frequencies due to alloying.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Compact, single mode, frequency stabilized laser spectroscopy sources for isotope analysis

We will discuss here ultra-stable narrow line-width Hybrid External Cavity Lasers (HECL) of visible spectrum. The customer requires ~ 2 MHz linewidth / stability (2.7 fm). It is our goal to design the most stable possible ECL, and then enhance its long-term stability by disciplining it to an atomic wavelength reference. Protection against long-term drift can be provided by calibrating HECL wavelength to a hollow-cathode lamp (HCL) standard using the optogalvanic effect to adjust the HECL set-point. Here we report the short-term stability of the HECL alone, i.e., without the discipline of an atomic wavelength reference. For this purpose, we have studied HECLs operating at 405 nm and at 638 nm. We will interpret their performance in terms of the customer’s need for 600 – 700 nm narrow-linewidth spectroscopy. We selected to perform the portion of the work at 405 nm since the sensitivity to cavity stability is ~2x compared with operating in the 600 – 700 nm wavelength range. Further, we will show excellent wavelength stability over time at 638 nm. The two main ECL components are the semiconductor laser chip, including a high reflectivity (HR) mirror, and a volume Bragg grating (VBG) that provides output coupling. Between them is collimating optics. The theoretical analysis and experimental data suggest that control of ECL wavelength in the femtometer wavelength range can be achieved over short-term time scales by carefully controlling both the temperature and very high current stability. From the results presented here temperature control of the laser to 0.001° C along with current stability of 0.001 mA will be needed in a sensor instrument. Finally, we show a path to achieve 2 MHz short-term stability at 600 to 700 nm.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2018

Transport in Random Media With Inhomogeneous Mixing Statistics

The Levermore-Pomraning (LP) model has been investigated for use in implicit Monte Carlo (IMC) algorithms to describe thermal photon transport computations in stochastically mixed cells with material energy coupling. For purely absorbing non-emitting materials, the LP-model is known to predict the exact material averaged fluxes when the mixing statistics are Markovian. In the presence of scattering or reemmission, or if the mixing is non-Markovian, the LP-model is approximate and has greatly diminished accuracy for optically thick, highly scattering materials. Nevertheless, the model enables a robust extension of the simple atomic mix approximation to accommodate spatial correlation effects through well characterized parameters such as mean chord lengths. In this work, we construct exact analytical solutions of the LP-equations for piecewise constant spatial variation of the material chord lengths. It is not possible in general to obtain closed form solutions when the chord lengths are continuous functions of space, although we briefly examine special conditions under which this is feasible. However, by allowing an arbitrarily fine spatial segmentation of the medium it is possible to construct highly refined solutions to fit desired spatial chord length profiles. Material volume fractions that are consistent with the chord lengths are first constructed by solving the associated Chapmann-Kolmogorov equations and applied to obtain the material averaged fluxes in two settings: when the materials are purely absorbing, and when scattering is present in rod model geometry. Illustrative numerical results for the volume fractions and material averaged fluxes are obtained by implementing the algorithms in MATLAB for spatially linear and quadratic variations of the chord lengths.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Development of an Integrated Waste Plan for Chalk River Laboratories - 13376

To further its Strategic Planning, the Atomic Energy of Canada Limited (AECL) required an effective approach to developing a fully integrated waste plan for its Chalk River Laboratories (CRL) site. Production of the first Integrated Waste Plan (IWP) for Chalk River was a substantial task involving representatives from each of the major internal stakeholders. Since then, a second revision has been produced and a third is underway. The IWP remains an Interim IWP until all gaps have been resolved and all pathways are at an acceptable level of detail. Full completion will involve a number of iterations, typically annually for up to six years. The end result of completing this process is a comprehensive document and supporting information that includes: - An Integrated Waste Plan document summarizing the entire waste management picture in one place; - Details of all the wastes required to be managed, including volume and timings by waste stream; - Detailed waste stream pathway maps for the whole life-cycle for each waste stream to be managed from pre-generation planning through to final disposition; and - Critical decision points, i.e. decisions that need to be made and timings by when they need to be made. A waste inventory has been constructed that serves as the master reference inventory of all waste that has been or is committed to be managed at CRL. In the past, only the waste that is in storage has been effectively captured, and future predictions of wastes requiring to be managed were not available in one place. The IWP has also provided a detailed baseline plan at the current level of refinement. Waste flow maps for all identified waste streams, for the full waste life cycle complete to disposition have been constructed. The maps identify areas requiring further development, and show the complexities and inter-relationships between waste streams. Knowledge of these inter-dependencies is necessary in order to perform effective options studies for enabling facilities that may be necessary for multiple related waste streams. The next step is to engage external stakeholders in the optioneering work required to provide enhanced confidence that the path forward identified within future iterations of the IWP will be acceptable to all. (authors)

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2012

Theory of nonlinear elasticity, stress-induced relaxation, and dynamic yielding in dense fluids of hard nonspherical colloids

We generalize the microscopic naïve mode coupling and nonlinear Langevin equation theories of the coupled translation-rotation dynamics of dense suspensions of uniaxial colloids to treat the effect of applied stress on shear elasticity, cooperative cage escape, structural relaxation, and dynamic and static yielding. The key concept is a stress-dependent dynamic free energy surface that quantifies the center-of-mass force and torque on a moving colloid. Here, the consequences of variable particle aspect ratio and volume fraction, and the role of plastic versus double glasses, are established in the context of dense, glass-forming suspensions of hard-core dicolloids. For low aspect ratios, the theory provides a microscopic basis for the recently observed phenomenon of double yielding as a consequence of stress-driven sequential unlocking of caging constraints via reduction of the distinct entropic barriers associated with the rotational and translational degrees of freedom. The existence, and breadth in volume fraction, of the double yielding phenomena is predicted to generally depend on both the degree of particle anisotropy and experimental probing frequency, and as a consequence typically occurs only over a window of (high) volume fractions where there is strong decoupling of rotational and translational activated relaxation. At high enough concentrations, a return to single yielding is predicted. For large aspect ratio dicolloids, rotation and translation are always strongly coupled in the activated barrier hopping event, and hence for all stresses only a single yielding process is predicted.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

INFRARED SPECTROSCOPY OF COMET 73P/SCHWASSMANN-WACHMANN 3 USING THE SPITZER SPACE TELESCOPE

We have used the Spitzer Space Telescope Infrared Spectrograph (IRS) to observe the 5-37 {mu}m thermal emission of comet 73P/Schwassmann-Wachmann 3 (SW3), components B and C. We obtained low spectral resolution (R {approx} 100) data over the entire wavelength interval, along with images at 16 and 22 {mu}m. These observations provided an unprecedented opportunity to study nearly pristine material from the surface and what was until recently the interior of an ecliptic comet-the cometary surface having experienced only two prior perihelion passages, and including material that was totally fresh. The spectra were modeled using a variety of mineral types including both amorphous and crystalline components. We find that the degree of silicate crystallinity, {approx}35%, is somewhat lower than most other comets with strong emission features, while its abundance of amorphous carbon is higher. Both suggest that SW3 is among the most chemically primitive solar system objects yet studied in detail, and that it formed earlier or farther from the Sun than the bulk of the comets studied so far. The similar dust compositions of the two fragments suggest that these are not mineralogically heterogeneous, but rather uniform throughout their volumes. The best-fit particle size distribution for SW3B has a form dn/da {approx} a{sup -3.5}, close to that expected for dust in collisional equilibrium, while that for SW3C has dn/da {approx} a{sup -4.0}, as seen mostly in active comets with strong directed jets, such as C/1995 O1 Hale-Bopp. The total mass of dust in the comae plus nearby tail, extrapolated from the field of view of the IRS peak-up image arrays, is (3-5) x 10{sup 8} kg for B and (7-9) x 10{sup 8} kg for C. Atomic abundances derived from the spectral models indicate a depletion of O compared to solar photospheric values, despite the inclusion of water ice and gas in the models. Atomic C may be solar or slightly sub-solar, but its abundance is complicated by the potential contribution of spectrally featureless mineral species to the portion of the spectra most sensitive to the derivation of the C abundance. We find a relatively high bolometric albedo, {approx}0.13 for the dust, considering the large amount of dark carbonaceous material, but consistent with the presence of abundant small particles and strong emission features.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Enhanced Generic Phase-field Model of Irradiation Materials: Fission Gas Bubble Growth Kinetics in Polycrystalline UO 2

Experiments show that inter-granular and intra-granular gas bubbles have different growth kinetics which results in heterogeneous gas bubble microstructures in irradiated nuclear fuels. A science-based model predicting the heterogeneous microstructure evolution kinetics is desired, which enables one to study the effect of thermodynamic and kinetic properties of the system on gas bubble microstructure evolution kinetics and morphology, improve the understanding of the formation mechanisms of heterogeneous gas bubble microstructure, and provide the microstructure to macroscale approaches to study their impact on thermo-mechanical properties such as thermo-conductivity, gas release, volume swelling, and cracking. In our previous report 'Mesoscale Benchmark Demonstration, Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO 2 under Post-irradiation Thermal Annealing', we developed a phase-field model to simulate the intra-granular gas bubble evolution in a single crystal during post-irradiation thermal annealing. In this work, we enhanced the model by incorporating thermodynamic and kinetic properties at grain boundaries, which can be obtained from atomistic simulations, to simulate fission gas bubble growth kinetics in polycrystalline UO 2 fuels. The model takes into account of gas atom and vacancy diffusion, vacancy trapping and emission at defects, gas atom absorption and resolution at gas bubbles, internal pressure in gas bubbles, elastic interaction between defects and gas bubbles, and the difference of thermodynamic and kinetic properties in matrix and grain boundaries. We applied the model to simulate gas atom segregation at grain boundaries and the effect of interfacial energy and gas mobility on gas bubble morphology and growth kinetics in a bi-crystal UO 2 during post-irradiation thermal annealing. The preliminary results demonstrate that the model can produce the equilibrium thermodynamic properties and the morphology of gas bubbles at grain boundaries for given grain boundary properties. More validation of the model capability in polycrystalline is underway.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2013

A Novel and Cost Effective Approach to the Decommissioning and Decontamination of Legacy Glove Boxes - Minimizing TRU Waste and Maximizing LLW Waste - 13634

This paper describes the process of decommissioning two gloveboxes at the Argonne National Laboratory (ANL) that were employed for work with plutonium and other radioactive materials. The decommissioning process involved an initial phase of clearing tools and materials from the glove boxes and disconnecting them from the laboratory infrastructure. The removed materials, assessed as Transuranic (TRU) waste, were packaged into 55 gallon (200 litre) drums and prepared for ultimate disposal at the Waste Isolation Pilot Plant (WIPP) at Carlsbad New Mexico. The boxes were then sampled to determine the radioactive contents by means of smears that were counted with alpha and beta detectors to determine the residual surface contamination, especially in terms of alpha particle emitters that are an indicator of TRU activity. Paint chip samples were also collected and sent for laboratory analysis in order to ascertain the radioactive contamination contributing to the TRU activity as a fixed contamination. The investigations predicted that it may be feasible to reduce the residual surface contamination and render the glovebox structure low level waste (LLW) for disposal. In order to reduce the TRU activity a comprehensive decontamination process was initiated using chemical compounds that are particularly effective for lifting and dissolving radionuclides that adhere to the inner surfaces of the gloveboxes. The result of the decontamination process was a reduction in the TRU surface activity on the inner surfaces of the gloveboxes by four orders of magnitude in terms of disintegrations per unit area (DPA). The next phase of the process involved a comprehensive assay of the gloveboxes using a combination of passive neutron and gamma ray scintillation detectors and a shielded and collimated high purity Germanium (HPGe) gamma ray detector. The HPGe detector was used to obtain gamma ray spectra for a variety of measurement positions within the glovebox. The spectra were used to determine the TRU content of the boxes by assessing the activity of Am-241 (59 keV) and Pu-241 (414 keV). Using the data generated it was possible for qualified subject matter experts (SME) to assess that the gloveboxes could be consigned for disposition as LLW and not as TRU. Once this determination was assessed and accepted the gloveboxes were prepared for final disposition to the Nevada National Security Site (NNSS) - formerly the Nevada Test Site (NTS). This preparation involved fixing any remaining radioactive contamination within the gloveboxes by filling them with a foam compound, prior to transportation. Once the remaining contamination was fixed the gloveboxes were removed from the laboratory and prepared for transported by road to NNSS. This successful glovebox decontamination and decommissioning process illustrates the means by which TRU waste generation has been minimized, LLW generation has been maximized, and risk has been effectively managed. The process minimizes the volume of TRU waste and reduced the decommissioning time with significant cost savings as the result. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗