Two new solvent extraction technologies have been recently developed to simultaneously separate cesium and strontium from spent nuclear fuel, following dissolution in nitric acid. The first process utilizes a solvent consisting of chlorinated cobalt dicarbollide and polyethylene glycol extractants in a phenyltrifluoromethyl sulfone diluent. Recent improvements to the process include development of a new, non-nitroaromatic diluent and development of new stripping reagents, including a regenerable strip reagent that can be recovered and recycled. This new strip reagent reduces product volume by a factor of 20, over the baseline process. Countercurrent flowsheet tests on simulated spent nuclear fuel feed streams have been performed with both cesium and strontium removal efficiencies of greater than 99 %. The second process developed to simultaneously separate cesium and strontium from spent nuclear fuel is based on two highly-specific extractants: 4',4',(5')-Di-(t-butyldicyclo-hexano)-18-crown-6 (DtBuCH18C6) and Calix[4]arene-bis-(tert-octylbenzo-crown-6) (BOBCalixC6). The DtBuCH18C6 extractant is selective for strontium and the BOBCalixC6 extractant is selective for cesium. A solvent composition has been developed that enables both elements to be removed together and, in fact, a synergistic effect was observed with strontium distributions in the combined solvent that are much higher that in the strontium extraction (SREX) process. Initial laboratory test results of the …

We report on a direct measurement of two-dimensional potential distribution on the surface of Cu(In,Ga)Se2 thin films using a nanoscale electrical characterization of scanning Kelvin probe microscopy both in air and in ultra-high vacuum. The potential measurement reveals a higher surface potential or a smaller work function on grain boundaries (GBs) of the film than on the grain surfaces. This demonstrates the existence of a local built-in potential on GBs, and the GB is positively charged. The role of the built-in potential in device performance was further examined and found to be positive, by tuning Ga content or bandgap of the film. With increasing Ga content, the potential drops sharply in a Ga range of 28%-38%. Comparing the change in the built-in potential to the theoretical and experimental photoconversion efficiencies, we conclude that the potential plays a significant role in the device conversion efficiency of NREL's three-stage Cu(In,Ga)Se2 device.

We provide qualitative insight into depletion-region collection in GaInNAs cells to (1) understand the effect of diffusion length L on the QE; and (2) describe the magnitude of L required to get adequate current from the cell. We use Wolf's equations for the QE including a drift field E, and model E as being equal to the junction built-in voltage distributed uniformly across the depletion region. This allows us to calculate the QE as a function of L and depletion width WD. We show that if L is sufficiently small, increasing WD can actually decrease the QE. To determine how long L needs to be in a practical GaInNAs junction, we calculate from the QE the short-circuit current density as a function of WD and L. This allows us to estimate that Lambipolar needs to be greater than roughly 1 {micro}m in order to obtain enough photocurrent for the 4-junction application, giving guidance to the experimental effort to develop such cells.

Article addressing, from a historical perspective, Newton's sums of like powers of natural numbers.

While most active research involving beryllium in the United States remains tied strongly to biological effects, there are several areas of technology development in the last two years that should be mentioned. (1) Beryllium disposed of in soil vaults at the Idaho National Laboratory (INL) Radioactive Waste Management Complex (RWMC) has been encapsulated in-situ by high-temperature and pressure injection of a proprietary wax based material to inhibit corrosion. (2) A research program to develop a process for removing heavy metals and cobalt from irradiated beryllium using solvent extraction techniques has been initiated to remove components that prevent the beryllium from being disposed of as ordinary radioactive waste. (3) The JUPITER-II program at the INL Safety and Tritium Applied Research (STAR) facility has addressed the REDOX reaction of beryllium in molten Flibe (a mixture of LiF and BeF2) to control tritium, particularly in the form of HF, bred in the Flibe by reactions involving both beryllium and lithium. (4) Work has been performed at Los Alamos National Laboratory to produce beryllium high heat flux components by plasma spray deposition on macro-roughened substrates. Finally, (5) corrosion studies on buried beryllium samples at the RWMC have shown that the physical form of some …

None

The fuel service conditions for the DOE Next Generation Nuclear Plant (NGNP) will be challenging. All major fuel related design parameters (burnup, temperature, fast neutron fluence, power density, particle packing fraction) exceed the values that were qualified in the successful German UO2 TRISO-coated particle fuel development program in the 1980s. While TRISO-coated particle fuel has been irradiated at NGNP relevant levels for two or three of the design parameters, no data exist for TRISO-coated particle fuel for all five parameters simultaneously. Of particular concern are the high burnup and high temperatures expected in the NGNP. In this paper, where possible, we evaluate the challenges associated with high burnup and high temperature quantitatively by examining the performance of the fuel in terms of different known failure mechanisms. Potential design solutions to ameliorate the negative effects of high burnup and high temperature are also discussed.

One obstacle to wider market penetration for thin-film polycrystalline photovoltaic (PV) modules is the lack of field performance data, notably temperature-coefficient data for the current-voltage (I-V) characteristics over all irradiance levels encountered in the field. Generally, temperature coefficient and performance data are available only in a restricted range of illumination around 1-sun intensity. In this paper, the I-V performance data are presented, analyzed, and parameterized across a wide range of illumination levels and temperatures, allowing the modeling of the performance for three polycrystalline PV technologies: cadmium telluride, copper indium diselenide, and polycrystalline silicon. The data are scrutinized for clear-sky and diffuse-illumination conditions.

Collection of photocarriers in Ga{sub x}In{sub 1-x}N{sub y}As{sub 1-y} solar cells is limited by the poor quality of the Ga{sub x}In{sub 1-x}N{sub y}As{sub 1-y}. Some reports have shown collection of photocarriers outside of the depleted layer in annealed Ga{sub x}In{sub 1-x}N{sub y}As{sub 1-y}, but the key to achieving the higher collection has been unclear. In this paper, we attempt to quantify the diffusion and collection lengths that contribute to the photocurrent in Ga{sub x}In{sub 1-x}N{sub y}As{sub 1-y} solar cells. The data imply that the effective {mu}{tau} product for the lightly doped Ga{sub x}In{sub 1-x}N{sub y}As{sub 1-y} material may vary when a field is applied. We conclude that the fields present in most of our best Ga{sub x}In{sub 1-x}N{sub y}As{sub 1-y} cells are large enough to aid collection of photocarriers.

Transparent conducting oxides (TCOs) can serve a variety of important functions in thin-film photovoltaics such as transparent electrical contacts, antireflection coatings, and chemical barriers. Two areas of particular interest are TCOs that can be deposited at low temperatures and TCOs with high carrier mobilities. We have employed combinatorial high-throughput approaches to investigate both these areas. Conductivities of s = 2500 W-1-cm-1 have been obtained for In-Zn-O (IZO) films deposited at 100 C and s > 5000 W-1-cm-1 for In-Ti-O (ITiO) and In-Mo-O (IMO) films deposited at 550 C. The highest mobility obtained was 83 cm2/V-s for ITiO deposited at 550 C.

This paper compares results from a computational fluid dynamics (CFD) simulation of airflow and pollutant dispersion under mixed-convection conditions with experimental data obtained in our 7m x 9m x 11m high experimental facility. A tracer gas was continuously released from a 1 m{sup 2} horizontal source 0.5 m above the floor. Path-integrated concentrations were measured along multiple short and long sampling paths in three horizontal planes. A steady state CFD analysis was used to model these experiments. The Reynolds Averaged Navier-Stokes (RANS) equations were solved for the flow and temperature field using the commercial CFD software, StarCD. CFD results were compared with the measured path-integrated concentrations. Accuracy of CFD predictions was found to improve with inclusion of thermal effects, and further by using a low-Re turbulence model.

The Outdoor Test Facility (OTF) at NREL is equipped with data acquisition systems that monitor the performance of modules deployed outdoors in real time, including the measurement of current-voltage traces every 15 minutes during all daylight hours. This affords us the ability to analyze performance across many levels of illumination which allows the determination of factors that affect module performance and that serve as indicators of module quality, including average diode quality factors, series resistances values, and reverse-saturation currents of the cells. This study focuses on several polycrystalline thin-film modules, including cadmium telluride. CIS, and polycrystalline silicon. We present these parameters, acquired from outdoor measurements, and compare the results with measurements obtained from more canonical methods.

A mechanism for the transport of H into a Si solar cell during plasma-enhanced chemical vapor deposition (PECVD) of a hydrogenated silicon nitride (SiN:H) layer and its subsequent fire-through metallization process is described. The PECVD process generates process-induced traps, which ''store'' H at the surface of the solar cell. This stored H is released and diffuses rapidly into the bulk of Si during the high-temperature metallization-firing process. During the ramp-down, the diffused H associates with impurities and defects and passivates them. The firing step partially heals up the surface damage. The proposed model explains a variety of observations and experimental results.

We constrain the Cosmic Star Formation Rate (CSFR) by requiring that massive stars produce the observed UV, optical, and IR light while at the same time not overproduce the Diffuse Supernova Neutrino Background as bounded by Super-Kamiokande. With the massive star component so constrained we then show that a reasonable choice of stellar Initial Mass Function and other parameters results in SNIa rates and iron yields in good agreement with data. In this way we define a ''concordance'' CSFR that predicts the optical SNII rate and the SNIa contribution to the MeV Cosmic Gamma-Ray Background. The CSFR constrained to reproduce these and other proxies of intermediate and massive star formation is more clearly delineated than if it were measured by any one technique and has the following testable consequences: (1) SNIa contribute only a small fraction of the MeV Cosmic Gamma-Ray Background, (2) massive star core-collapse is nearly always accompanied by a successful optical SNII, and (3) the Diffuse Supernova Neutrino Background is tantalizingly close to detectability.

During long-term exposure of photovoltaic modules to environmental stress, the ingress of water into the module is correlated with decreased performance. By using diffusivity measurements for water through encapsulants such as ethylene vinyl acetate (EVA), we have modeled moisture ingress using a finite-element analysis with atmospheric data from various locations such as Miami, Florida. This analysis shows that because of the high diffusivity of EVA, even an impermeable glass back-sheet alone is incapable of preventing significant moisture ingress from the edges for a 20-year lifecycle. This result has led us to investigate ways to protect modules from moisture through the use of different encapsulating chemistries and materials.

Following our observation of slow degradation of short-circuit current (Isc) in crystalline silicon (x-Si) modules that was correlated with ultraviolet (UV) exposure dose, we initiated a new study of individual x-Si cells designed to determine the degradation cause. In this paper, we report the initial results of this study, which has accumulated 1056 MJ/m2 of UV dose from 1-sun metal-halide irradiance, equivalent to 3.8 years at our test site. At this time, the control samples are unchanged, the unencapsulated samples have lost about 2% of Isc, and the samples encapsulated in module-style packages have declined from 1% to 3%, depending on the cell technology.

Waste drums containing remote-handled (RH) transuranic (TRU) waste from the Argonne National Laboratory-East (ANL-E) are stored in sealed, underground vaults at the Radioactive Waste Management Complex (RWMC) at the Idaho National Engineering and Environmental Laboratory (INEEL). The waste consists of laboratory debris from the destructive examination of fuel elements irradiated mostly in the Experimental Breeder Reactor II (EBR-II). In 2004, air samples were obtained from some of these vaults and analyzed for radioactivity. Some of the samples show that the vaults contained several DAC's (derived air concentrations) of tritium, which are considered as non-negligible by Environmental Protection Agency (EPA) regulations. Based on Acceptable Knowledge (AK) records of the waste stored in the vaults, ORIGEN2 calculations were performed to estimate the isotopic contents in the waste drums stored in the vaults. The calculations are based on the irradiation of fuel elements that produced the waste. The absolute amounts of isotopic contents in the waste drums are normalized to Cs-137 contents derived from measured surface dose rates, mostly from the Cs-137 radiation, as documented in AK records. The amounts of tritium thus calculated (assuming no loss from those produced during fission except for decay) are compared to the measured values in the …

High-quality single-layer and bilayer diamond-like carbon (DLC) thin films are fabricated by two technologies, namely, ion-assisted plasma-enhanced deposition (IAPED) and electron cyclotron resonance (ECR) deposition. Deposition on various substrates, such as sapphires and solar cells, has been performed at low substrate temperatures (50 {approx} 80 C). The two deposition technologies allow good control over the growth conditions to produce DLC films with desired optical properties, thickness, and energy bandgap. The bilayer-structured DLC can be fabricated by using IAPED for the bottom layer followed by ECR for the top layer, or just by IAPED for both layers with different compositions. The DLC films have shown good spatial uniformity, density, microhardness, and adhesion strength. They exhibit excellent stability against attack by strong acids, prolonged damp-heat exposure at 85 C and 85% relative humidity, mechanical scratch, ultrasonication, and irradiation by ultraviolet (UV), protons, and electrons. When deposited on crystalline Si and GaAs solar cells in single-layer and/or bilayer structure, the DLC films not only serve as antireflection coating and protective encapsulant, but also improve the cell efficiencies.

Ag, Cu, and Ni metallizations were inkjet-printed with near-vacuum deposition quality. The approach developed can be easily extended to other conductors such as Pt, Pd, and Au. Thick, highly conducting lines of Ag and Cu demonstrating good adhesion to glass, Si, and PCB have been printed at 100-200 C in air and N2, respectively. Ag grids were inkjet-printed on Si solar cells and fired through the silicon nitride antireflective layer at 850 C resulting in 8%-efficient cells. Next-generation multicomponent inks (including etching agents) have also been developed with improved fire-through contacts leading to higher cell efficiencies. PEDOT-PSS polymer-based conductors were inkjet-printed with conductivity as good or better than that of spin-coated films.

The chemical shift of the {sup 129}Xe NMR signal has been shown to be extremely sensitive to the local environment around the atom and has been used to follow processes such as ligand binding by bacterial periplasmic binding proteins (Rubin et al. 2000; Lowery et al. 2004). Here we show that the {sup 129}Xe shift can sense more subtle changes: magnesium binding, BeF{sub 3}{sup -} activation, and peptide binding by the E. coli chemotaxis Y protein. {sup 1}H-{sup 15}N correlation spectroscopy and x-ray crystallography were used to identify two xenon-binding cavities in CheY that are primarily responsible for the shift changes. One site is near the active site, and the other is near the peptide binding site.

Sodium is known to enhance p-type doping in copper indium diselenide (CIS)-based devices fabricated on soda-lime glass substrates, and similar amounts of Na are present in commercial cadmium telluride (CdTe) devices. We present the results on the effects of Na incorporation on the properties of CdTe/CdS solar cells prepared on borosilicate glass substrates. A NaF layer 10 to 30 nm thick was incorporated at either the CdS/CdTe interface or on the CdTe surface, as a source of Na. CdTe layers were deposited by close-spaced sublimation at substrate temperatures from 425 C (LT) to 620 C (HT), followed by heat-treatment in the presence of CdCl2 vapor. Atomic force microscopy analysis showed that the samples with NaF at the CdS/CdTe interface deposited in He ambient have larger grains with a sub-grain structure that disappears after CdCl2 heat treatment accompanied by an increase in grain size. Samples deposited in O2 ambient have smaller grains without a sub-grain structure. For samples with NaF deposited on the CdTe surface, LT samples with CdCl2 heat treatment showed a morphology similar to samples without NaF layers; but samples heat-treated in He ambient at 500 C prior to CdCl2 treatment showed a different microstructure with platelets on the …

A study of Ga1-xInxNyAs1-y solar cells shows that nitrogen degrades the solar cells even for very small nitrogen concentrations. By comparing the properties of p-on-n and n-on-p Ga1-xInxNyAs1-y cells as a function of y, we find that the n-on-p cells show a more abrupt decrease in the open-circuit voltage and greater decrease of the photocurrent. The asymmetry in the performance of the cells reflects the differences observed for electrons and holes in Ga1-xInxNyAs1-y. The electron mobility is degraded much more than the hole mobility when nitrogen is added to GaAs, implying that the electron diffusion length should be degraded more than the hole diffusion length. An electron trap (observed by deep-level transient spectroscopy) affects p-type GaNyAs1-y more than n-type GaNyAs1-y, consistent with the observation that the open-circuit voltage of n-on-p cells decreases more than that of p-on-n cells. The effect of nitrogen on GaNAs cells is shown to be much greater than expected for an isoelectronic impurity.

This paper reviews the current commercial status of CuInSe2 alloys (collectively, CIS) and CdTe-based photovoltaic (PV) modules, comparing the performance of commercial products with the results achieved for solar cell and prototype module champions. We provide an update for these PV cell and module technologies, and also compare CIS and CdTe performance levels to the results achieved by the crystalline Si PV industry. This comparison shows that CIS and CdTe module technology presently offers the best (and perhaps only) approach for significantly exceeding the cost/performance levels established by crystalline Si PV technologies. A semi-empirical methodology is used for comparing ''champion'' solar cell and prototype module data with performance achieved on manufacturing lines. Using a conservative assumption that thin-film technologies will eliminate the 40% of PV module costs arising from the Si wafer or ribbon, we estimate the future performance of all established PV module candidates, and conclude that, based on 2004 knowledge about each PV technology, CIS and CdTe should provide cost-competitive advantages over crystalline Si.

We have used deep-level transient spectroscopy to detect traps in p-type GaAsN grown by metal-organic chemical vapor deposition. Although minority-carrier electrons are not intentionally injected into the depletion region of the measured samples, electron traps are detected in both Schottky barrier and p-n junction devices. The electron-trap signal can exist using only reverse biases during measurement, and checks of series resistance and minority-carrier injection using an optical source also confirm the electron-trap signal. For dilute-nitrogen p-n junction samples, the electron trap gives the dominant signal peak. The peak's magnitude, which corresponds to trap density, correlates to amounts of nitrogen incorporated during growth and reduced open-circuit voltage during light characterization. The p-type GaAsN layers have net acceptor carrier concentrations in the mid-1016 to low-1017 cm-3, as determined by capacitance-voltage profiling. The electron-trap concentration depends on the N content, but values, when traps are filled to saturation, range from 1015 to 1016 cm-3. The electron signal peak shows a shoulder peak on some samples, giving another close energy level. The electron-trap activation energy is somewhat dependent on the trap filling time, but ranges from about 0.15 to 0.30 eV, and is usually near 0.2 eV for the largest peak when filled to …