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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Additively-manufactured monocrystalline YBCO superconductor

Abstract Single-crystal microstructures enable high-performance YBa 2 Cu 3 O 7-x superconductors which are however limited to simple shapes due to their brittleness. Additive manufacturing can fabricate YBa 2 Cu 3 O 7-x superconductor with complex shapes, albeit with a polycrystalline microstructure. Here, we demonstrate a route to grow single-crystals from 3D-ink-printed, polycrystalline, sintered superconducting YBa 2 Cu 3 O 7-x (YBCO or Y123) + Y 2 BaCuO 5 (Y211), manufacturing objects with complex architectures displaying both high critical current density (J c =2.1 × 10 4 A . cm –2 , 77 K) and high critical temperature (T c = 88-89.5 K). An ink containing precursor powders (Y 2 O 3 , BaCO 3 , and CuO) is 3D-extruded into complex geometries and then reaction-sintered to obtain polycrystalline Y123 + Y211. A seed is then utilized to transform these 3D-printed parts from polycrystal to monocrystal via the melt growth method. The geometric details of 3D-printed parts survive the process without slumping, sagging or collapse, despite the long-term presence of liquid above the peritectic temperature. Origami structures can be created by sheet folding after 3D-printing. This additive approach enables the facile fabrication of superconducting devices with complex shapes and architectures, such as advanced undulator magnets to generate synchrotron radiation and microwave cavities for dark-matter axion search. This work highlights the potential of additive manufacturing for producing monocrystalline cuprate superconductors and opens the door to additive manufacturing of other monocrystalline functional ceramic or semiconductor materials.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

An ICME Modeling Framework for Metal Matrix Composites Focusing on Ultrahigh Temperature Matrix Material and Tungsten Carbide Reinforcement Particulate (Final CRADA Report)

Ultra High Temperature Metal Matrix Composites (UHT-MMCs) are of interest to the due to their potential defense and aerospace applications. These materials consist of a metal matrix reinforced with a stiff ceramic or cermet. Based on a preliminary literature survey, this project will focused on a pure titanium (Ti) matrix reinforced with tungsten carbide-cobalt (WC-Co). UHT-MMC technology is still at a nascent stage of development and requires extensive experimental work to optimize the structure and resulting material properties of a particular UHT-MMC material system. An accurate and complete high-performance computing (HPC) model of the Ti/WC-Co material system could greatly accelerate the development and deployment Ti/WC-Co materials by connecting processing parameters to material properties. This type of model could then be used in an integrated computational materials engineering approach to optimize the material structure to achieve a targeted level of performance.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Flame-Sprayed Pure and Ce-Doped TiO 2 Photocatalysts

Pure and Ce-doped TiO 2 nanoparticles were successfully synthesized in one step by means of the scalable flame spray pyrolysis (FSP) process. Complete structural and chemical characterization of these materials revealed that the majority of the nanoparticles are crystalline and spherical, ranging from 5 to 45 nm in diameter. Furthermore, the band gap of TiO 2 was reduced by doping with Ce from 2.43 to 3.06 eV and the Ce–TiO 2 nanoparticles exhibit a strong photoelectrical response to visible light illumination. Ce–TiO 2 nanoparticles obtained with this scalable method are trivially scalable to industrial level manufacturing, granting and enabling additional approaches for the actual application of ceramic oxide nanomaterials to combat challenges such as environmental cleanup and energy production from the visible part of solar inputs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Remote Fiber Laser Cutting System for Dismantling Glass Melter - 13071

Since 2008, the equipment for dismantling the used glass melter has been developed in High-level Liquid Waste (HLW) Vitrification Facility in the Japanese Rokkasho Reprocessing Plant (RRP). Due to the high radioactivity of the glass melter, the equipment requires a fully-remote operation in the vitrification cell. The remote fiber laser cutting system was adopted as one of the major pieces of equipment. An output power of fiber laser is typically higher than other types of laser and so can provide high-cutting performance. The fiber laser can cut thick stainless steel and Inconel, which are parts of the glass melter such as casings, electrodes and nozzles. As a result, it can make the whole of the dismantling work efficiently done for a shorter period. Various conditions of the cutting test have been evaluated in the process of developing the remote fiber cutting system. In addition, the expected remote operations of the power manipulator with the laser torch have been fully verified and optimized using 3D simulations. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Acoustic sensors for fission gas characterization: R and D skills devoted to innovative instrumentation in MTR, non-destructive devices in hot lab facilities and specific transducers for measurements of LWR rods in nuclear plants

First of all, we will present the main principle of the method. A piezoelectric transducer, driven by a pulse generator, generates the acoustic waves in a cavity that may be the fuel rod or a chamber connected to an instrumented rod. The composition determination consists in measuring the time of flight of the acoustic signal emitted. The pressure can be estimated by a calibration process, above the measurement of the amplitude of the signal. Two projects will then be detailed. The first project consists in the development of advanced instrumentation for in-pile experiments in Material Testing Reactor. It constitutes a main goal for the improvement of the nuclear fuel behavior knowledge. This acoustic method was tested with success during a first experiment called REMORA 3, and the results were used to differentiate helium and fission gas release kinetics under transient operating conditions. This experiment was lead at OSIRIS reactor (CEA Saclay, France). As a first step of the development program, we performed in-pile tests on the most sensitive component, i.e., the piezoelectric transducer. For this purpose, the active part of this sensor has been qualified on gamma and neutron radiations and at high temperature. Various industrial piezo-ceramics were exposed to a high activity Cobalt source for few days. The cumulated dose was ranged from 50 kGy up to 2 MGy. Next, these devices were placed inside a Material Test Reactor to investigate their reliability towards neutron fluence. The final fluence after 150 days of irradiation was up to 1.6.10{sup 21}n/cm{sup 2} (for thermal neutron). Irreversible variations have been measured. Next, a specific sensor has been implemented on an instrumented fuel rod and tested in the frame of a REMORA 3 Irradiation test. It was the first experiment under high mixed, temperature neutron and gamma flux. A first irradiation phase took place in March 2010 in the OSIRIS reactor and in November 2010 for the second step of the irradiation. The instrumented fuel rod incorporating the ultrasonic gas composition sensor was finally irradiated during 2 weeks in nominal conditions. Neutronics calculation will be performed in order to calculate the thermal and fast neutron fluence and the gamma dose absorbed by acoustic sensor. A first evaluation gives a thermal fluence about 4,5.10{sup 19} n/cm{sup 2}, a fast neutrons fluence about 4,5.1018 n/cm{sup 2} and a total gamma dose up to 0,25 MGy The maximal temperature during the irradiation test was about 150 C. Although the ultrasonic sensor appears to be damaged, the optimization of the electrical attack parameters and the development of a new signal processing maintain the measurement feasibility up the end of the irradiation campaign. It was the first time that the composition of fission gas has been monitored all along an irradiation experiment in a MTR, giving access to the gas release kinetics. New researches involve thick film transducers produced by screen-printing process in order to propose piezoelectric structures for harsh temperature and irradiation measurements. The second project consists in the development of a non-destructive device that can be directly applied on a LWR fuel rod. The problem to be solved relates to the measurement of the fission gas pressure and composition in a fuel rod using a non-destructive method. Fuel rod internal pressure is one of the safety criteria applied in nuclear power analyses. This criterion must be verified in order to avoid any fuel-cladding gap reopening risk and therefore any local clad ballooning. Apart from the safety implications, this parameter is also a fuel behaviour indicator and reflects the overall fuel performance in operation, but also during shipping and long-term storage. Rod internal pressure is one criterion amongst others, like cladding corrosion, against which the acceptable fuel burn-up limit is set. A sensor has been achieved in 2007. A full-scale hot cell test of the internal gas pressure and composition measurement by an acoustic sensor was conducted successfully between 2008 and 2010 on 5 high burn-up MOX fuel rods and 2 very high burn-up UO{sub 2} fuel rods in LECA Facility at Cadarache Centre. An improvement of this sensor has been proposed, allowing us to divide by two the uncertainty on the pressure measurement. In the case of hot-cell measurements, viscous liquid can be used to couple the sensor with the rod. For gas content with a pressure exceeding 15 bars and a 10% Xe/Kr ratio, such coupling may reduce relative acoustic method accuracy by ±7% for pressure measurement result and ±0.25 % for the assessment of gas composition. These results make it possible to demonstrate the feasibility of the technique on LWR fuel rods. The transducer and the associated methodology are now operational for non-destructive measurements in hot lab facilities and allow characterising the fission gas without puncturing the fuel rods. Up to now, any other non-destructive method can be proposed. A next step will be the development of an industrial application in a fuel storage pool in order to perform a large number of measurements on a fuel assembly in nuclear plants.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2015

Application of computational fluid dynamics for the simulation of cryogenic molecular sieve bed absorber of hydrogen isotopes recovery system for Indian LLCB-TBM

One of the most challenging tasks in the design of the fuel cycle system lies in the effective design of Tritium Extraction System (TES) which involves proper extraction and purification of tritium in the fuel cycle of the fusion reactor. Indian Lead Lithium cooled Ceramic Breeder Test Blanket Module (LLCB-TBM) would extract hydrogen isotopes through Cryogenic Molecular Sieve Bed (CMSB) adsorber system. A prototype Hydrogen Isotopes Recovery System (HIRS) is being developed to validate the concepts for tritium extraction by adsorption mass transfer mechanism. In this study, a design model has been developed and analyzed to simulate the adsorption mass transfer kinetics in a fixed bed adsorption column. The simulation leads primarily to effective design of HIRS, which is a state-of-the-art technology. The paper describes the process simulation approach and the results of Computational Fluid Dynamics (CFD) analysis. The effects of different operating conditions are studied to investigate their influence on the hydrogen isotopes adsorption capacity. The results of the present simulation study would be used to understand the best optimized transport phenomenon before realizing the TES as a system for LLCB-TBM. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Preparation and Characterization of YBa 2 Cu 4 O 8 Superconductor

Solid-state reaction of appropriate amounts of Y 2 O 3 , BaCOs, and CuO for 2 h at 800°C in flowing oxygen with a total pressure of 2.7 x 10 2 Pa (2 mm Hg), followed by cooling and annealing at 750°C for 10 h in oxygen at ambient pressure, has produced orthorhombic YBa 2 Cu 4 O 8 (124) as the main phase with YBa 2 Cu 3 O x (123) as an impurity phase. After the as-calcined powder was annealed in oxygen at 800°C for 24 h under ambient pressure, the phase purity improved considerably. Calcined 124 powder was pressed into pellets and rapidly annealed at temperatures from 870°C to 935°C. At these temperatures, the 124 decomposed into 123. The superconducting transition temperature, T c , of the annealed samples depended upon the annealing temperature and atmosphere. The decomposed samples have been characterized by low field RF SQUID magnetometer and high resolution transmission electron microscopy.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Accelerated Testing of Selected Filler Compositions

The fillers R&D program, mostly experimental, is part of a broader R&D program that includes new process modeling and performance assessment of criticality effects and the overall importance of criticality to repository performance (consequence screening). A literature research and consultation effort with experts by Hardin and Brady (2018) identified several potentially effective and workable filler materials including cements (primarily phosphate based), molten-metal alloys, and low-temperature glasses. Filler attributes were defined and the preliminary lists were compared qualitatively. Further comparative analysis will be done (e.g., cost estimates) after experimental screening has narrowed the list of alternatives. The following cement filler compositions were selected for experimental development work and accelerated testing in FY19: Aluminum phosphate cements (APCs); more specifically aluminum oxide / aluminum phosphate (Al 2 O 3 / AlPO 4 ) cements in which Al 2 O 3 serves as the filler material bound by an AlPO 4 binder formed by the reaction of Al 2 O 3 with H 3 PO 4 ; Calcium phosphate cements (CPCs); more specifically composed of pure or nearly pure hydroxyapatite (Ca 5 (PO 4 ) 3 (OH)); Magnesium potassium phosphate cements (MKPs) composed of magnesium oxide / magnesium potassium phosphate (MgO / MgKPO 4 ) cements in which MgO serves as the filler and MgKPO 4 serves as the binder formed by the reaction of MgO with monopotassium phosphate (KH 2 PO 4 ) and tricalcium phosphate ((Ca 3 (PO 4 ) 2 ); Two additional potential cement materials were explored preliminarily as the result of: (1) continued literature investigations into other filler candidates (wollastonite-based phosphate ceramic) and (2) the experimental discovery of a well-consolidated fly ash phosphate cement during the evaluation of fly ash as a potential filler material with Al 2 O 3 in APCs. Fly ash phosphate cements, more specifically in which a fly ash material composed primarily of mullite and quartz serves as the filler and is reacted with H 3 PO 4 to form amorphous phosphate phase(s) as the binder; Wollastonite aluminum phosphate cements (WAPC), specifically wollastonite / aluminum phosphate (CaSiO 3 / AlPO 4 ) in which CaSiO 3 serves as the filler material and AlPO 4 serves as the binder formed by Al(OH) 3 or metakaolin as Al sources and H 3 PO 4 or ammonium dihydrogen phosphate (ADP) (NH 4 H 2 PO 4 ) as phosphate sources. The FY19 effort focused on the optimization of compositions and subsequent processing of these five materials to achieve dense and well-consolidated monolithic samples with relatively low porosity. Once these goals were met basic material properties screening evaluations were performed including an assessment of dissolution resistance in water at elevated temperature (200 °C) and mechanical testing including unconfined compressive strength (UCS) testing. To date, the aluminum phosphate cements (APCs) appear to show the most promise for continued development. They are easily prepared and form smooth pourable slurries that remain stable for days with relatively low viscosities of several thousand centipoise (cP). They are then set at elevated temperatures (e.g., 170 °C) under ambient (0.1 MPa) or elevated pressure (~1MPa). Overall, they demonstrate the best dissolution resistance in water at elevated temperature (200 °C) and good compressive strengths. However, additional effort is required to optimize the APC slurry formulations and the process used for thermal curing these materials. The calcium phosphate cements (CPCs) can be formed at room temperature to produce a well-consolidated body. However, their slurry viscosities are very high (and difficult to measure) and they exhibit relatively short cure times of 2 to 3 hours. Also, dissolution resistance is very poor, the poorest of all the cements examined The same is the case for the small number of MKP cements fabricated; they cure very quickly (10 minutes or less) and disintegrate within a few hours upon immersion in distilled water. Surprisingly, fly ash reacts with phosphoric acid to form dense and well-consolidated cements but the mixture rapidly sets at room temperature (less than 30 minutes) and the subsequent conversion of the binder to an amorphous phosphate phase(s) as a function of temperature is complicated. Finally, the wollastonite aluminum phosphate cements (WAPC) are easily prepared and form smooth pourable slurries that remain stable for several hours. They are then set at 130 °C. A WAPC sample exhibited the highest compressive strengths of all the materials we evaluated but in general their dissolution resistance to water is poor.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Investigation of thermal transport in composites and ion beam irradiated materials for nuclear energy applications

Thermal transport in materials used for energy applications is a physical process directly tied to performance and reliability. As a result, a great deal of effort has been devoted to understanding thermal transport in materials whose ability to conduct heat is critical. Here in this paper, our objective is to discuss the utility of laser-based thermoreflectance (TR) approaches that provide microscale measurement of thermal transport. We provide several examples that implement the TR technique to investigate thermal transport in materials used in nuclear energy applications. First, we discuss utility of this technique to measure thermal conductivity in ion irradiated ceramic materials during investigations where the primary objective is to understand the impact of radiation induced crystalline structure defects on thermal transport. We also present the capability of TR approach to resolve thermal conductivity of each layer in tristructural isotropic fuel, silicon carbide fiber composites, and 2nd phase precipitates in uranium silicide. Finally, the ability to measure interface thermal resistance between adjacent layers in composites is demonstrated.

36 MATERIALS SCIENCE↗
DOE OSTI2022

High temperature thick film sensor development based on doped lanthanum chromites refractory semiconductors materials

High temperature advanced sensing materials have generated high demand due the high accuracy temperature measurements requirements for process optimization, controlling and sensing. Some technological applications of harsh conditions sensing include monitoring tiles of space shuttles, rotating bearings in aircraft engines, turbines, jet engines dynamics and chemical reactors. High temperature conditions limit the sensing strategies, where typically traditional metal thermocouples are unstable, and the sensing options are limited to optical spectroscopy methods. Recently, refractory semiconductors thick- and thin-film thermocouples have been developed and, in many cases, preferred over conventional metallic thermocouples due their spatial resolution, and capability of direct deposition on any surface. Rare earth chromites ceramics materials, exhibit some properties of interest for high temperature sensing technologies development, such as: high microstructure and sintering stability, excellent conductive behavior at high temperatures, and matching thermal expansion coefficients relative to other conductors and refractory ceramics. In this work, high performance ultra-high temperature thermocouples using p-type and n-type doped lanthanum chromites materials were fabricated and tested at temperatures up to 1500 o C. Thermoelectric voltage, Seebeck Coefficients were established for all devices, evidencing high stability and performance in prolongated operational time and harsh conditions.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2016

Thermal Conductivity and Diffusivity for SiC Fibers for Use in ATF Cladding Composites

As part of the accident tolerant fuels (ATF) initiative, there is a need to understand the thermophysical properties of cladding for these fuels. One potential cladding material is silicon carbide (SiC) ceramic matrix composite reinforced with SiC fibers because of the corrosion resistance, resistance to hydrogen formation, high bulk thermal conductivity, and favorable mechanical properties of SiC. However, data about the thermal properties of individual SiC fibers in these composites is absent in the literature. This paper presents the measured axial thermal conductivity and thermal diffusivity of a leading SiC fiber (HiNicalon Type S) via a thermal measurement technique (transient electrothermal technique, TET) optimized for thin fibers. The results show that the measured properties are significantly lower than bulk values for SiC. Because of the low neutron absorption, as well as excellent thermal and mechanical properties, zircaloy has primarily been used for the fuel cladding in many nuclear reactors. A major drawback of the zircaloy is its hydrogen generation vulnerability. This issue has been known for some time, but the explosion of hydrogen accident in the Fukushima Daiichi nuclear disaster has motivated efforts for accident tolerant fuels (ATF) and their cladding as suitable substitutes for zircaloy. Fuel cladding made of silicon carbide (SiC) ceramic matrix composite (CMC) is an attractive alternative to the zircaloy. Investigation on the tubular monolithic a-SiC polytropes indicates that it has superior oxidation (hydrogen production) resistance (three orders of magnitude slower) than zircaloy. Additionally, it has well-documented, favorable mechanical properties, along with high temperature corrosion resistance. However, its bulk thermal properties can vary significantly depending on polytrope, the grain size, grain boundary, or impurities. At room temperature, SiC has a thermal conductivity as high as 490 Wm{sup -1}K{sup -1}, where the {sup 6}H polytrope has the highest conductivity. Thermal measurements of the SiC CMC are usually accomplished by laser flash method for thermal diffusivity (a) and thermal conductivity is indirectly calculated through the relationship k=aρcp. Depending on the manufacturing method and the reinforced fiber, the composite thermal conductivity varies from <10 Wm{sup -1}K{sup -1} to ∼70 Wm{sup -1}K{sup -1}. While the flash method is convenient for the measurement of the composite, it is difficult to apply to the measurement of individual fibers. Because of this, the thermal properties of individual SiC fibers is not present in the literature. Because the SiC fiber manufacturing process is different than that of the SiC matrix in the CMC, the properties of the bulk material might be erroneous when applied to the fiber. Being able to measure the fiber properties independently and directly allows for an understanding of the effect of the manufacturing process on the fiber and the opportunity to potentially improve or control the thermal properties of the composite. This improved accuracy can be achieved by measuring the fiber with a technique optimized for individual fiber measurement, known as the Transient Electrothermal Technique or TET. This paper presents the thermal conductivity and diffusivity of a leading SiC fiber (HiNicalon Type S). Measurements are performed with the TET, with the resulting properties being significantly lower than the bulk values of SiC, which is one possible explanation for relatively low CMC values. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2014

AOI [3] High-Temperature Nano-Derived Micro-H 2 and - H 2 S Sensors

The emissions from coal-fired power plants remain a significant concern for air quality. This environmental challenge must be overcome by controlling the emission of sulfur dioxide (SO 2 ) and hydrogen sulfide (H 2 S) throughout the entire coal combustion process. One of the processes which could specifically benefit from robust, low cost, and high temperature compatible gas sensors is the coal gasification process which converts coal and/or biomass into syngas. Hydrogen (H 2 ), carbon monoxide (CO) and sulfur compounds make up 33%, 43% and 2% of syngas, respectively. Therefore, development of a high temperature (>500°C) chemical sensor for in-situ monitoring of H 2 , H 2 S and SO2 2 levels during coal gasification is strongly desired. The selective detection of SO 2 /H 2 S in the presence of H 2 , is a formidable task for a sensor designer. In order to ensure effective operation of these chemical sensors, the sensor system must inexpensively function within harsh temperature and chemical environment. Currently available sensing approaches, which are based on gas chromatography, electrochemistry, and IR-spectroscopy, do not satisfy the required cost and performance targets. This work focused on the development microsensors that can be applied to this application. In order to develop the high- temperature compatible microsensor, this work addressed various issues related to sensor stability, selectivity, and miniaturization. In the research project entitled “High-Temperature Nano-Derived Micro-H 2 and -H 2 S Sensors”, the team worked to develop micro-scale, chemical sensors and sensor arrays composed of nano-derived, metal-oxide composite materials to detect gases like H 2 , SO 2 , and H 2 S within high-temperature environments (>500°C). The research was completed in collaboration with NexTech Materials, Ltd. (Lewis Center, Ohio). NexTech assisted in the testing of the sensors in syngas with contaminate levels of H 2 S. The idea of including nanomaterials as the sensing material within resistive-type chemical sensor platforms was to increase the sensitivity (as shown for room temperature applications). Unfortunately, nanomaterials are not stable at high temperatures due to sintering and coarsening processes that are driven by their high surface to volume ratio. Therefore, new hydrogen and sulfur selective nanomaterial systems with high selectivity and stability properties in the proposed harsh environment were investigated. Different nano-morphologies of zirconate, molybdate, and tungstate compounds were investigated. The fabrication of the microsensors consisted of the deposition of the selective nanomaterial systems over metal based interconnects on an inert substrate. This work utilized the chemi-resistive (resistive- type) microsensor architecture where the chemically and structurally stable, high temperature compatible electrodes were sputtered onto a ceramic substrate. The nanomaterial sensing systems were deposited over the electrodes using a lost mold method patterned by conventional optical lithography. The microsensor configuration with optimized nanomaterial system was tested and compared to a millimeter-size sensor e outcomes of this research will contribute to the economical application of sensor arrays for simultaneous sensing of H 2 , H 2 S, and SO 2 .

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

Vacuum drying of spent fuel storage canisters/casks - 'just how much water could be left in there, anyway?' - 15233

The process of moving spent fuel assemblies from wet storage in the spent fuel pool to dry storage in an inert gas environment within a canister or cask typically involves two main stages. In the first stage, the bulk of the water is removed by a draining or siphoning operation, conducted with pressure inside the canister maintained at 1.3 to 2 atm. This process removes most of the water in the cask cavity, but residual water can be left behind, in three main regions. The largest region, typically, is the bottom of the cavity below the end of the siphon tube. A second general class of locations, also located at the bottom of the cask cavity, consists of the 'dashpots' at the ends of the various non-fuel tubular structures within the fuel assemblies. For PWR assemblies, these are the control rod guide sleeve tubes and instrumentation thimbles. For BWR assemblies, these are the water rods of various designs and control blade ends in some configurations. A third class of locations consists of porous material within the cavity that can absorb water, such as thin ceramic neutron poison plates, and ostensibly intact fuel rods that nevertheless might have pinholes or fine cracks in the cladding that could allow pool water to creep inside the fuel rod. To remove residual water from these locations, the second stage of drying operations utilizes vacuum drying, by reducing the pressure sufficiently to convert the water to vapor that can then be pumped out of the canister cavity. In this operation, the cask cavity pressure is slowly reduced from the nominal condition of (1.3-2.0 atm (1000-1520 torr), to a final target pressure below 3 torr (0.004 atm). This is typically accomplished in three to five stages, with prescribed 'hold' points defined in procedures or in the Technical Specifications, to preclude sudden pressure spikes due to flashing of water to steam, or development of large local temperature gradients in the fuel rods or other cask internal components. This paper discusses the various locations in the system where residual water may 'hang up' in the cask, and presents a discussion of the physical basis for the effectiveness of vacuum drying for removing it. Results and conclusions based on realistic qualitative and quantitative evaluations of the transient heat transfer behavior of the system are presented, based on detailed modeling of a range of spent fuel canister designs and decay heat loads, most notably the 24P Dry Shielded Canisters (DSCs) stored at the Rancho Seco Independent Spent Fuel Storage Installation (ISFSI), the NAC-MPC modules at Maine Yankee, the 24P DSCs stored at Calvert Cliffs, and the Holtec HI-STORM modules at Hope Creek. The evaluations presented here show that ice formation within a spent fuel canister is highly unlikely, due to the availability of a large thermal source term in the form of the decay heat load of the spent fuel. The formation of ice is an operational concern, since it mainly affects operation of equipment external to the canister (i.e., the hoses, valves, and fittings of the vacuum drying equipment.) Evaluations are presented for quantifying the amount of residual water that could remain in the cask cavity, even after successful drying operations, since vacuum drying is a limit process, and by definition, cannot remove all of the water from the cavity, no matter how long the operation goes on, even if all of it is in vapor form. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Direct Ink-Write Printing of Ceramic Clay with an Embedded Wireless Temperature and Relative Humidity Sensor

This research presents a simple method to additively manufacture Cone 5 porcelain clay ceramics by using the direct ink-write (DIW) printing technique. DIW has allowed the application of extruding highly viscous ceramic materials with relatively high-quality and good mechanical properties, which additionally allows a freedom of design and the capability of manufacturing complex geometrical shapes. Clay particles were mixed with deionized (DI) water at different ratios, where the most suitable composition for 3D printing was observed at a 1:5 w/c ratio (16.2 wt.%. of DI water). Differential geometrical designs were printed to demonstrate the printing capabilities of the paste. In addition, a clay structure was fabricated with an embedded wireless temperature and relative humidity (RH) sensor during the 3D printing process. The embedded sensor read up to 65% RH and temperatures of up to 85 °F from a maximum distance of 141.7 m. The structural integrity of the selected 3D printed geometries was confirmed through the compressive strength of fired and non-fired clay samples, with strengths of 70 MPa and 90 MPa, respectively. This research demonstrates the feasibility of using the DIW printing of porcelain clay with embedded sensors, with fully functional temperature- and humidity-sensing capabilities.

42 ENGINEERING↗
DOE OSTI2022

Thermal properties of field-assisted-sintered SiCN–Y 2 O 3 composites

Polymer-derived amorphous SiCN has excellent high-temperature stability and properties. To reduce the shrinkage during pyrolysis and to improve the high-temperature oxidation resistance, Y 2 O 3 was added as a filler. In this study, polymer-derived SiCN–Y 2 O 3 composites were fabricated by mixing a polymeric precursor of SiCN with Y 2 O 3 submicron powders in different ratios. The mixtures were cross-linked and pyrolyzed in argon. SiCN–Y 2 O 3 composites were processed using field-assisted sintering technology at 1350°C for 5 min under vacuum. Dense SiCN–Y 2 O 3 composite pellets were successfully made with relative density higher than 98% and homogeneous microstructure. Due to low temperature and short time of the heat-treatment, the grain growth of Y 2 O 3 was substantially inhibited. The Y 2 O 3 grain size was ~1 μm after sintering. The composites’ heat capacity, thermal diffusivity, and thermal expansion coefficients were characterized as a function of temperature. The thermal conductivity of the composites ceramics decreased as the amount of amorphous SiCN increased and the coefficient of thermal expansion (CTE) of the composites increased with Y 2 O 3 content. However, the thermal conductivity and CTE did not follow the rule of mixture. This is likely due to the partial oxidation of SiCN and the resultant impurity phases such as Y 2 SiO 5 , Y 2 Si 2 O 7 , and Y 4.67 (SiO 4 ) 3 O.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Characterization of Highly Thermally Conductive Organic Substrates for a Double-Sided Cooled Power Module

Abstract Silicon-Carbide (SiC) power devices have become a promising option for traditional Silicon (Si) due to the superior material properties. To fully take advantage of the SiC devices, a high-performance power device packaging solution is necessary. This study proposes a cost-effective double-sided cooled (DSC) 1.2 kV SiC half-bridge power module using organic epoxy-resin composite dielectric (ERCD) substrates. The high mechanical and thermal performance of the power module is achieved by the low-modulus, moderate thermal conductivity, and relatively thin (120 μm) layer of ERCD material compared with traditional metal-clad ceramic approaches. This novel organic dielectric can withstand high voltage (5 kV @ 120 μm) and operate up to 250°C continuously, which is indispensable for high power applications. The thermal modeling results show that the equivalent thermal resistance junction-to-case (Rjc_eq) of the DSC power module using dual direct bonded copper (DBC) is 17% higher than the dual ERCD configuration. Furthermore, a non-insulated DSC power module concept is proposed for maximizing thermal performance by considering thermal vias in the ERCD substrate and direct-soldered heat sink. A thought process for optimization of thermal via design is demonstrated and it shows up to 24% of improvement on thermal performance compared with the insulated DSC power module.

Double-sided cooling, epoxy-resin composite dielec↗
DOE OSTI2019

Reaction-bond composite synthesis of SiC-TiB 2 by spark plasma sintering/field-assisted sintering technology (SPS/FAST)

High-density SiC-TiB 2 composites were fabricated using the displacement reaction spark plasma sintering/field-assisted sintering technology (SPS/FAST) and SiC, B 4 C, TiC, and Si powders. The reaction process was performed in a narrow time frame compared hot pressing. The SiC-TiB 2 composites were sintered with precursor SiC at various pressures to determine the effects of processing with SPS/FAST. The composites completed synthesis during SPS/FAST processing, which occurs more quickly than hot pressing. SEM, STEM, and Raman spectroscopy are used to show the conversion and microstructure. Finally, the composite of 53.6 wt.% SiC and 46.4 wt.% TiB 2 has 99 % theoretical density, hardness of 26.4 GPa, and fracture toughness of 5.12 MPa m 1/2 .

36 MATERIALS SCIENCE↗