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ReBr(CO)5 is gamma nitrogen-derived structured and crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of four bromorhenium molecules and twenty formaldehyde molecules.
This paper describes the measurement of convective heat transfer coefficients and friction factors for sCO 2 flowing in a smooth tube and compares the results with published correlations for validation. The paper also describes the Heat Exchange and Experimental Testing (HEET) rig recently designed and built at the U.S. Department of Energy’s (DoE’s) National Energy Technology Laboratory (NETL) in Morgantown, WV. Here, the Wilson-plot technique used for measuring the heat transfer coefficients is described along with the data reduction process. The Wilson-plot technique was chosen as the basis for the design of NETL’s HEET rig. Advantages of the Wilson-plot technique include the (1) ability to measure high convective heat transfer coefficients accurately, (2) ability to measure average heat transfer coefficient for complicated heat exchange geometries like those produced using additive manufacturing, (3) ability to measure heat transfer coefficients on both sides of a heat exchanger independently, and (4) simplicity of experimental setup. Capabilities of the HEET rig include pressure to 24 MPa (3500 psig), temperature to 538 °C (1000 °F), mass flow rate to 1.5 kg/s (3 lb/s), and Re to 500,000. The rig is designed to operate with pure CO 2 or a mixture of CO 2 and up to 10% N2 by volume to study the impact of gas mixtures typical of direct-fired sCO 2 power cycles on the convective heat transfer and pressure drop. Preliminary tests in the HEET rig were performed with smooth stainless-steel tube and pure CO 2 , and the results were compared with published correlations for Nusselt number (Nu) and friction factor. Over a Reynolds number (Re) range from 58,000 to 228,000, measured Nu was compared to predictions using the Dittus and Boelter equation (Kreith and Bohn, 1993, “Principles of Heat Transfer, West Publishing Company”) within 5% and measured friction factors were compared to predictions using the McAdams correlation (“McAdams, 1954, “Heat Transmission,” 3rd ed., McGraw Hill, New York)” for smooth tube to be within 5%.
ReI(CO)5 is alpha carbon monoxide-derived structured and crystallizes in the orthorhombic Cmcm space group. The structure is zero-dimensional and consists of twenty formaldehyde molecules and four iodorhenium molecules.
Re2Te5 crystallizes in the orthorhombic Pbca space group. The structure is two-dimensional and consists of two Re2Te5 sheets oriented in the (0, 0, 1) direction. there are three inequivalent Re5+ sites. In the first Re5+ site, Re5+ is bonded to five Te2- atoms to form edge-sharing ReTe5 square pyramids. There are a spread of Re–Te bond distances ranging from 2.71–2.75 Å. In the second Re5+ site, Re5+ is bonded to five Te2- atoms to form edge-sharing ReTe5 square pyramids. There are a spread of Re–Te bond distances ranging from 2.72–2.77 Å. In the third Re5+ site, Re5+ is bonded to five Te2- atoms to form edge-sharing ReTe5 square pyramids. There are a spread of Re–Te bond distances ranging from 2.71–2.76 Å. There are eight inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 7-coordinate geometry to three Re5+ atoms. In the second Te2- site, Te2- is bonded in a 5-coordinate geometry to three Re5+ atoms. In the third Te2- site, Te2- is bonded in a 1-coordinate geometry to one Re5+ atom. In the fourth Te2- site, Te2- is bonded in a square co-planar geometry to four Te2- atoms. There are two shorter (3.04 Å) and two longer (3.07 Å) Te–Te bond lengths. In the fifth Te2- site, Te2- is bonded in a 6-coordinate geometry to three Re5+ atoms. In the sixth Te2- site, Te2- is bonded in a 4-coordinate geometry to three Re5+ atoms. In the seventh Te2- site, Te2- is bonded in a 1-coordinate geometry to one Re5+ and one Te2- atom. In the eighth Te2- site, Te2- is bonded in a 1-coordinate geometry to one Re5+ and one Te2- atom.
This work compares the temporal and spatial characteristics of the AIRSAMSU (Atmospheric Infrared Sounder Advanced Microwave Sounding Unit A) Version 6 and MODIS (Moderate resolution Imaging Spectroradiometer) Collection 5 derived surface temperatures over Greenland. To estimate uncertainties in space-based surface temperature measurements, we re-projected the MODIS Ice Surface Temperature (IST) to 0.5 by 0.5 degree spatial resolution. We also re-gridded AIRS Skin Temperature (Ts) into the same grid but classified with different cloud conditions and surface types. These co-located data sets make intercomparison between the two instruments relatively straightforward. Using this approach, the spatial comparison between the monthly mean AIRS Ts and MODIS IST is in good agreement with RMS 2K for May 2012. This approach also allows the detection of any long-term calibration drift and the careful examination of calibration consistency in the MODIS and AIRS temperature data record. The temporal correlations between temperature data are also compared with those from in-situ measurements from GC-Net (GCN) and NOAA stations. The coherent time series of surface temperature evident in the correlation between AIRS Ts and GCN temperatures suggest that at monthly time scales both observations capture the same climate signal over Greenland. It is also suggested that AIRS surface air temperature (Ta) can be used to estimate the boundary layer inversion.
Here, the goal of the present work was to provide the necessary reaction emulation information to enable detailed process simulation of a chemical looping H 2 production system from fossil fuels using CaFe 2 O 4 . This specifically pertained to the necessary kinetic data, reaction model development, and model rate parameters required for reaction emulation in both reducing and oxidizing environments. A logical methodology was defined, which included discretization of the reaction network, establishing a core model for reaction emulation that could be adapted based on the system phenomena, and development of a rate parameter regression tool designed around the core model. An extensive array of data sets was acquired by which parametric regressions were performed. The work presented and tabulated a comprehensive set of rate parameters for the reduction and oxidation reactions of CaFe 2 O 4 and descendent phases of Ca 2 Fe 2 O 5 , FeO, Fe 3 O 4 , Fe, and CaO to emulate reaction behavior in a looping-based process environment. This included direct reduction using CH 4 , H 2 , and CO, and direct oxidation reactions with steam, CO 2 and O 2 . Dynamic equilibrium was quantified for reactions that could utilize H 2 O and CO 2 as soft oxidants to re-saturate lattice oxygen in the depleted structure/phases. The kinetics associated with the oxidative mechanisms with the soft oxidants were quantified and compared to those of the reducing counterparts. The analysis provided critical insight to emulate reactions for a process that seeks to use natural gas (NG) or other fossil fuels as a direct reductant for the end goal of H 2 production.
Two Luna 16 soils have been analyzed for Ag, Au, Bi, Br, Cd, Co, Cs, Cu, Ga, Ge, In, Ur, Ni, Rb, Re, Sb, Se, Te, Tl, and Zn. A meteoritic component similar to that in Apollo 11 and 12 soils seems to be present, corresponding to about 1.5 to 2% Cl chondrites or equivalent. It probably consists largely of micrometeorites. Three elements show strong enrichments compared to Apollo 11 and 12 soils: Cd (5 x to 200 x), Ag (5 x to 10 x), and Bi (3 x). Presumably these elements were brought in by Cd-Ag-Bi rich material, similar to that in Unit VI of Apollo core 12028.
We present the first N 2 profile for Venus’ deep lower atmosphere (<15 km) and a constrained isotopic composition for cloud N 2 [1]. This work directly addresses unresolved questions for Venus using legacy observations. Prior to this work, there were no reported measurements for N 2 abundances at <15 km and the isotopic composition remained unconstrained [2]. The N 2 parameters are critical to understanding the evolution and thermal properties of the atmosphere [3-7]. Our N 2 results were obtained by re-analysis of data acquired in 1978 by the Pioneer Venus Large Probe Neutral Mass Spectrometer (LNMS) [8]. The archived mass spectra from 64.2 to 0.2 km were treated using the analytical procedures specifically developed for the LNMS [9-11]. Judicious peak fitting permitted disambiguation of (A) N 2 + and CO + at 28 u and (B) 14 N 15 N+, 13 CO + , and C 2 H 5 + at 29 u. Quality controls included comparing the (A) LNMS CO + /CO 2 + ratios to the NIST database and literature and (B) fitted counts for CO + to the expected counts of CO + calculated from C 18 O + and 13 CO + using the LNMS 16 O/ 18 O and 12 C/ 13 C ratios (obtained from CO 2 ). Our results show that N 2 is uniformly mixed across the deep lower atmosphere between ~0.2 and 15 km (2.49 ± 0.10 v%). In contrast, N 2 is non-uniformly mixed across the sub-cloud atmosphere and clouds (~15–59 km), where N 2 abundances increase by ~ 2-fold between ~15 km (2.45 ± 0.32 v%) and ~59-51 km (5.21 ± 0.18 v%). Using the cloud data, we also obtained a constrained 15 N/ 14 N ratio (2.93×10 -3 ± 0.13×10 -3 ) and δ 15 N value (-204 ± 35‰). Thus, the LNMS results [1] suggest that (A) the atmosphere is unstable at <15 km, (B) N 2 is not well-mixed >15 km, and (C) the cloud δ 15 N falls between Earth and the solar wind [12, 13]. Comparisons of the N 2 abundances and isotopic compositions for nitrogen, carbon, and oxygen to other Venus measurements will be discussed.
In recent years, research into the electrochemical reduction of CO 2 has grown exponentially. Formic acid (FA) has become a particular value product from CO 2 due to its versatility [1], optimal atom economy [2], and thermodynamic favorable [3]. FA can be produced electrochemically via a direct two-electron transfer process involving CO 2 with a proton source, requiring less energy input and fewer reaction steps than the conventional Kemira process. However, product selectivity, electrode stability, and low faradic efficiency due to increased resistance under constant current, remain key issues for CO 2 reduction to FA [4]. University of Kentucky’s Center for Applied Energy Research (UK CAER) is currently investigating reactor designs to address the challenges associated with electrochemical CO 2 conversion to FA [5]. The current reactor system employs: (1) an organic-based charge carrier which shuttles charge directly to the catalyst to enable CO 2 reduction to FA; (2) novel electrode materials to mitigate large voltages and improve conductivity; and (3) a flow system which not only allows for the volumetric scale-up of both charge carrier and catalyst, but also decouples the charger carrier re-energized and FA production processes to protect the catalyst’s stability due to overpotential. Through careful adjustment of electrode, charge carrier, and electrolyte selection, cell resistances have decreased by over 15%, facilitating conduction necessary for effective CO 2 reduction to FA. The system uses a highly specific engineered catalyst, which has produced over 100 mM FA at a rate of over 10 mM FA/hour following the aforementioned electrode/charge carrier changes. System design considerations (flow rate, bulk volume) and modeling of the system will also be discussed.
Redox reactions of iron (Fe) can play an important role in controlling the stability and transformation of organic carbon (OC) in soils. However, there is limited knowledge about the dynamics of Fe and OC in soils during anoxic-oxic transitions, which are common in temperate and tropical biomes. In this study, we investigated the fate and transformation of Fe and OC during a 5-day oxic incubation of four pre-reduced (8 days anoxic) forest soils. Up to 3.7% of total OC in the pre-reduced soils was oxidized to CO 2 , in conjunction with the oxidation of 31 –84% of the extractable Fe(II). OC oxidation in pre-reduced soils was lower than non-reducedcontrol soils, indicating that recently anoxically-incubated soils support lower OC metabolism upon re-oxidation than consistently oxic soils. Oxic OC oxidation was negatively correlated with the fraction of Fe-bound OC and also the fraction of short-range-ordered (SRO) Fe oxides. These results suggest that association with Fe oxides—especially SRO Fe oxides—can inhibit the availability of OC for oxidation. However, the difference between the oxidation of OC in pre40 reduced soils and consistently oxic controls could not be linked to the moderate changes in the Fe mineral composition during the anoxic-oxic transition, indicating the importance of longer term OC association with Fe oxides, as well as other processes, in regulating the oxidation of OC during the redox fluctuations. OC association with Fe oxides should be considered during simulations of biogeochemical cycling of OC in soils during the redox fluctuations, for which other processes such as the anoxic transformation of OC and response of the microbial community also need to be incorporated.
Charge transfer at electron-volt energies between multiply charged atomic ions and neutral atoms and molecules is of considerable importance in astrophysics, plasma physics, and in particular, fusion plasmas. In the year covered by this report, several major tasks were completed. These include: (1) the re-calibration of the ion gauge to measure the absolute particle densities of H2, He, N2, and CO for our current measurements; (2) the analysis of data for charge transfer reactions of N(exp 2 plus) ion and He, H2, N2, and CO; (3) measurement and data analysis of the charge transfer reaction of (Fe(exp 2 plus) ion and H2; (4) charge transfer measurement of Fe(exp 2 plus) ion and H2; and (5) redesign and modification of the ion detection and data acquisition system for the low energy beam facility (reflection time of flight mass spectrometer) dedicated to the study of state select charge transfer.
The existence of molecular clouds in the outer galaxy allows the study of star formation at large galactocentric radii. The study of these clouds has two aims. A systematic survey is underway to study the large scale distribution of the molecular clouds outside the solar circle. To understand the physical conditions in the clouds, fully sampled maps were (and are being) made in CO and other molecules. The continuum emission is also being mapped. The main objective in doing an infrared study was to obtain information on the luminosity of the stars formed in these clouds. Assuming all energy radiated from the star is absorbed by the dust and then re-radiated in the infrared, one can get an estimate of the star's luminosity by integrating the flux over the source and converting it to a luminosity. Until these observations, the only way of judging stellar luminosities was from peak CO temperatures. Accounting for beam dilution, Kutner and Mead inferred from these that the heat sources were late B or later stars. The Kupier Airborne Observatory was used to search 9 sources in 5 clouds for far infrared emission.
Li(ReO3)5 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a distorted square co-planar geometry to eight O2- atoms. There are a spread of Li–O bond distances ranging from 2.22–2.68 Å. In the second Li1+ site, Li1+ is bonded in a distorted square co-planar geometry to eight O2- atoms. There are a spread of Li–O bond distances ranging from 2.22–2.68 Å. There are twelve inequivalent Re+5.80+ sites. In the first Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–25°. There are a spread of Re–O bond distances ranging from 1.89–1.92 Å. In the second Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–25°. There are a spread of Re–O bond distances ranging from 1.89–1.94 Å. In the third Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–25°. There are a spread of Re–O bond distances ranging from 1.89–1.94 Å. In the fourth Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 21–25°. There is four shorter (1.90 Å) and two longer (1.92 Å) Re–O bond length. In the fifth Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–26°. There are a spread of Re–O bond distances ranging from 1.88–1.95 Å. In the sixth Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–26°. There are a spread of Re–O bond distances ranging from 1.88–1.94 Å. In the seventh Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–25°. There are a spread of Re–O bond distances ranging from 1.89–1.92 Å. In the eighth Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–25°. There are a spread of Re–O bond distances ranging from 1.89–1.92 Å. In the ninth Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–26°. There are a spread of Re–O bond distances ranging from 1.88–1.94 Å. In the tenth Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–26°. There are a spread of Re–O bond distances ranging from 1.89–1.93 Å. In the eleventh Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–25°. There are a spread of Re–O bond distances ranging from 1.89–1.94 Å. In the twelfth Re+5.80+ site, Re+5.80+ is bonded to six O2- atoms to form corner-sharing ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–25°. There is four shorter (1.90 Å) and two longer (1.92 Å) Re–O bond length. There are thirty inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+ and two Re+5.80+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+ and two Re+5.80+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+ and two Re+5.80+ atoms. In the seventh O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+ and two Re+5.80+ atoms. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+ and two Re+5.80+ atoms. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+ and two Re+5.80+ atoms. In the fourteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the sixteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+ and two Re+5.80+ atoms. In the eighteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the nineteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the twentieth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+ and two Re+5.80+ atoms. In the twenty-second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+ and two Re+5.80+ atoms. In the twenty-third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+ and two Re+5.80+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+ and two Re+5.80+ atoms. In the twenty-fifth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+ and two Re+5.80+ atoms. In the twenty-sixth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+ and two Re+5.80+ atoms. In the twenty-seventh O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+ and two Re+5.80+ atoms. In the twenty-eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two Re+5.80+ atoms. In the twenty-ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+ and two Re+5.80+ atoms. In the thirtieth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+ and two Re+5.80+ atoms.
High-temperature alloy wires are proposed for use in seal applications for future re-useable space vehicles. These alloys offer the potential for improved wear resistance of the seals. The wires must withstand the high temperature environments the seals are subjected to as well as maintain their oxidation resistance during the heating and cooling cycles of vehicle re-entry. To model this, the wires were subjected to cyclic oxidation in stagnant air. of this layer formation is dependent on temperature. Slow growing oxides such as chromia and alumina are desirable. Once the oxide is formed it can prevent the metal from further reacting with its environment. Cyclic oxidation models the changes in temperature these wires will undergo in application. Cycling the temperature introduces thermal stresses which can cause the oxide layer to break off. Re-growth of the oxide layer consumes more metal and therefore reduces the properties and durability of the material. were used for cyclic oxidation testing. The baseline material, Haynes 188, has a Co base and is a chromia former while the other two alloys, Kanthal A1 and PM2000, both have a Fe base and are alumina formers. Haynes 188 and Kanthal A1 wires are 250 pm in diameter and PM2000 wires are 150 pm in diameter. The coiled wire has a total surface area of 3 to 5 sq cm. The wires were oxidized for 11 cycles at 1204 C, each cycle containing a 1 hour heating time and a minimum 20 minute cooling time. Weights were taken between cycles. After 11 cycles, one wire of each composition was removed for analysis. The other wire continued testing for 70 cycles. Post-test analysis includes X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) for phase identification and morphology.
Yb2ReC2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Yb+2.50+ sites. In the first Yb+2.50+ site, Yb+2.50+ is bonded to five C4- atoms to form a mixture of edge and corner-sharing YbC5 square pyramids. There are a spread of Yb–C bond distances ranging from 2.59–2.73 Å. In the second Yb+2.50+ site, Yb+2.50+ is bonded in a square co-planar geometry to four C4- atoms. There are a spread of Yb–C bond distances ranging from 2.59–2.89 Å. Re3+ is bonded in a trigonal planar geometry to three C4- atoms. There are a spread of Re–C bond distances ranging from 1.86–1.99 Å. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded to four Yb+2.50+ and two equivalent Re3+ atoms to form a mixture of edge and corner-sharing CYb4Re2 octahedra. The corner-sharing octahedra tilt angles range from 5–52°. In the second C4- site, C4- is bonded to five Yb+2.50+ and one Re3+ atom to form a mixture of distorted edge and corner-sharing CYb5Re octahedra. The corner-sharing octahedra tilt angles range from 5–52°.
The multilab Intentional Forensics Venture is working to identify which stable elements (i.e., taggants) at trace concentrations relative to U would persist throughout the nuclear fuel cycle in a voluntary fuel tagging scheme. A taggant would provide the nuclear forensics community with a “barcode” to help identify nuclear materials found outside of regulatory control. A portion of this project was focused on reprocessing effects and determining which, if any, elements would coextract with U(VI) in standard Pu–U reduction extraction (PUREX) conditions. Elements with a propensity to coextract could, in theory, be used as taggants from a PUREX perspective. Although retention is not a performance requirement, the taggant signature would need to partition predictably from the U stream after the PUREX process to maintain forensic utility. This report documents results from several batch extraction studies with numerous trace elements from HNO 3 (1.5–5 M), with and without U(VI), into 30% tri-n-butyl phosphate (TBP) in kerosene. Extraction and back-extraction tests were used to evaluate nearly 60 elements in surrogate conditions for PUREX, and distribution coefficients (i.e., D-values) for most species were <0.1, indicating few species are likely to co-extract with U through PUREX. Additional studies are needed to optimize sample volumes and dilutions to dial in these low D-values. The D-values (D) were determined for several of the more promising elements, including Re and Se. Ultimately, we conclude that only a limited number of the ~ 60 elements investigated are extractable in the U stream of PUREX, based on measured D values, meaning most candidate elemental taggants would likely be lost at this stage of the nuclear fuel cycle, even when considering a range of acid concentrations.
The tetragonal ThMn 12 -type structure is stabilized in (Ce 1-x Zr x ) 2 T 16 M (x = 0.2 – 0.3; T = Fe or Fe/Co, M = Mo or W) arc-melted alloys. Approximately 5 at% of Mo or W admixture is sufficient to transform the hexagonal Th 2 Ni 17 -type structure of (Ce 1-x Zr x ) 2 Fe 17 into the tetragonal ThMn 12 -type structure of nearly single-phase (Ce 1-x Zr x ) 2 Fe 16 M and/or (Ce 1-x Zr x ) 2 Fe 15 CoM bulk alloys. X-ray Rietveld refinements reveal that Zr and Mo (W) substitute different sites in the tetragonal crystal structure. Zirconium preferentially replaces Ce, whereas Mo (W) substitutes Fe. At room temperature, the tetragonal phases exhibit strong ferromagnetism and a uniaxial magneto-crystalline anisotropy with anisotropy fields of 15 – 17 kOe. These materials possess room-temperature saturation magnetizations of 95 – 105 emu/g and Curie temperature of 420 – 505 K. At some concentrations, concurrent Zr and Mo (W) site occupancy facilitates 1:12 structure formation in bulk alloys with minimal presence of non-magnetic element in the Fe sublattice, thus securing the highest known magnetic moment per Fe atom (∼ 1.37 µ B ) in this type of materials. The intrinsic magnetic characteristics, as well as the absence of critical rare earths (RE), make these compounds interesting for development as low-cost permanent magnets. In conclusion, small Co additions improve the Curie temperature, especially if combined with W.
Hermetic machinery utilizing gas bearings for MW-scale supercritical CO 2 (sCO 2 ) machinery applications can have significantly lower power loss and enable improved cycle efficiency compared to conventional machinery with oil-lubricated bearings. Active magnetic bearings (AMBs) are another option anticipated to have similar power loss and load capacity to gas bearings as well as offering larger mechanical tolerances, the ability to tune properties, and high reliability due to lack of mechanical wear. AMBs also have proven commercial experience at MW-scale, though environments for high-temperature sCO 2 power cycle machinery conditions are novel. Besides the potential impact of AMBs for sCO 2 turbomachinery, the technology also offers promising benefits for steam and gas turbines for power generation, compressors and expanders for industrial heat and power, and in other oil and gas and space applications. The goals of this project were to conceptual design an AMB and perform material testing. Conceptual designs for radial and thrust AMBs were produced based on a hermetically-sealed sCO 2 machinery waste-heat recovery (WHR) application for sizing and loads, and choosing a target design temperature of 540°C useful for high-temperature sCO 2 turbines for concentrating solar power (CSP) applications. Conceptual designs were initially developed for multiple radial and thrust AMBs with spreadsheet-based calculations before selecting one of each to develop further using higher-fidelity design methods for magnetic and structural performance. It was found that the radial AMB at 540°C was feasible, but the thrust AMB needed to be limited to 315°C for high-speed operation. The decision for a reduced-temperature thrust AMB was the result of several significant conclusions: 1) Hiperco 50A, originally chosen for good magnetic performance at high temperature, had insufficient strength for high-speed operation, so it was replaced with 17-4 PH. 2) The reduced magnetic performance from 17-4 PH yielded a larger bearing size, reducing the strength margin. 3) This ultimately led to a creative design implementing a more-compact E-core topology, compared to the original (conventional) C-core, and an integral shaft-disk with Hirth joint connection. These conceptual designs are unique for the size and temperature in CO 2 , relevant for MW-scale CSP applications. Long term, high temperature test data was generated for several materials, filling a void in the current body of literature. Corrosion and magnetic performance measurements were produced for PM materials (Alnico 5-7C, Alnico 9C, and SmCo) with and without nickel-coating for environments of high-temperature CO 2 up to 550°C at atmospheric pressure and 450°C at 103 bar for up to 6,000 hours. Corrosion measurements were also produced for Hiperco 50, a SM material relevant for AMB laminations, with and without C5 coating. Comparisons were also made for 450°C and 550°C, atmospheric pressure air exposures up to 5,000 hours. Results generally show that coatings can be effective at improving oxidation resistance of the bare materials, and Alnicos generally outperformed SmCo after high-temperature exposure. In addition to technical feasibility demonstrated by the design, economic feasibility was demonstrated by updating the TEA from the reference machine, re-evaluating it with CAPEX and OPEX to reflect estimated changes from process-lubricated bearings to AMBs. AMBs were shown to be comparable in performance to process-lubricated bearings, still showing a notable improvement over conventional machinery architecture with oil-lubricated bearings.