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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

A framework for understanding efficient diurnal CO 2 reduction using Si and GaAs photocathodes

Integrated solar fuels and photoelectrochemical (PEC) CO 2 reduction (CO 2 R) are promising pathways toward producing value-added chemicals from CO 2 . However, improvements are needed in activity and selectivity as well as in fundamental understanding of device behavior to engender wide deployment. Here, we report two single-junction, integrated photocathodes for PEC CO 2 R based on TOPCon Si and GaAs substrates, which achieve -10 mA cm -2 at -0.33 V vs. RHE with 41% selectivity to C 2+ products and at -0.03 V vs. RHE with 27% selectivity to C 2+ products, respectively. We investigated the viability of a light-mediated strategy to direct selectivity in buried-junction PEC devices and confirmed that these devices could be optimized independently and described by the physics-based models of the individual components. Finally, we designed a framework to assess operational modes for PEC CO 2 R devices and demonstrated this framework under continuous galvanostatic control and variable illumination conditions.

14 SOLAR ENERGY↗
DOE OSTI2022

Effect of Annealing Conditions on Recovery of Lattice Damage in a High-Energy-Implanted 4H-SiC Superjunction PIN Diode

A high energy ion implantation system has been recently developed at the Tandem Van de Graaff facility at Brookhaven National Laboratory with tunable energy to 150 MeV capable of multi-step, deep implantation in 4H-SiC wafers with dopant atoms, such as B, P, Al, and N. Medium and high voltage devices with deep junctions can be fabricated using this system. Lattice strain introduced by the implantation process needs to be recovered and dopant atoms activated by appropriate annealing process as the device performance is strongly associated with the extent of recovery of the lattice. Using Synchrotron X-ray Rocking Curve Topography (SXRCT) and Reciprocal Space Mapping (RSM), the strain induced by high energy implantation of Al and N in 4H-SiC in different patterns are measured and mapped. It is observed that the strain levels correlate with the total fluence levels. PiN diodes fabricated on these implanted wafers were then annealed at temperatures ranging from 1700 °C to 2000 °C for 60 min. The SXRCT and RSM analysis of the annealed samples suggests that for the same annealing duration, higher temperature leads to better lattice recovery.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Encapsulating High–Temperature Superconducting Twisted van der Waals Heterostructures Blocks Detrimental Effects of Disorder

High-temperature cuprate superconductors based van der Waals (vdW) heterostructures hold high technological promise. One of the obstacles hindering their progress is the detrimental effect of disorder on the properties of the vdW-devices-based Josephson junctions (JJs). Here, a new method of fabricating twisted vdW heterostructures made of Bi 2 Sr 2 CuCa 2 O 8+δ , crucially improving the JJ characteristics and pushing them up to those of the intrinsic JJs in bulk samples, is reported. The method combines cryogenic stacking using a solvent-free stencil mask technique and covering the interface by insulating hexagonal boron nitride crystals. Despite the high-vacuum condition down to 10 –6 mbar in the evaporation chamber, the interface appears to be protected from water molecules during the in situ metal deposition only when fully encapsulated. Comparing the current-voltage curves of encapsulated and unencapsulated interfaces, it is revealed that the encapsulated interfaces' characteristics are crucially improved, so that the corresponding JJs demonstrate high critical currents and sharpness of the superconducting transition comparable to those of the intrinsic JJs. Finally, it is shown that the encapsulated heterostructures are more stable over time.

2D materials↗
DOE OSTI2024

Engineering Small HOMO–LUMO Gaps in Polycyclic Aromatic Hydrocarbons with Topologically Protected States

Topological phases in laterally confined low-dimensional nanographenes have emerged as versatile design tools that can imbue otherwise unremarkable materials with exotic band structures ranging from topological semiconductors and quantum dots to intrinsically metallic bands. The periodic boundary conditions that define the topology of a given lattice have thus far prevented the translation of this technology to the quasi-zero-dimensional (0D) domain of small molecular structures. Here, we describe the synthesis of a polycyclic aromatic hydrocarbon (PAH) featuring two localized zero modes (ZMs) formed by the topological junction interface between a trivial and nontrivial phase within a single molecule. First-principles density functional theory calculations predict a strong hybridization between adjacent ZMs that gives rise to an exceptionally small HOMO–LUMO gap. Scanning tunneling microscopy and spectroscopy corroborate the molecular structure of 9/7/9-double quantum dots and reveal an experimental quasiparticle gap of 0.16 eV, corresponding to a carbon-based small molecule long-wavelength infrared (LWIR) absorber.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Revealing the Nano-Scale Structure and Properties of Pinholes in SiOx Layers for POLO Contacts

In this contribution, we report on the charge collection characteristics of silicon photovoltaic devices with passivated contacts based on the c-Si/SiOx /poly-Si structure. Using electron-beam induced current (EBIC) imaging in plan-view and cross-section orientations, we find that charge collection in a device with a 1.5-nm-thick SiOx layer is fairly uniform in the p-n junction region and does not appear to be influenced by pyramidal surface texture. In contrast, a device with a 2.2-nm-thick oxide layer shows significant spatial variation in the charge-collection signal. The locations where we observe preferential collection of excess carriers is very sensitive to the processing conditions used to grow and breakup the SiOx passivation layer. In some cases the apexes of the pyramids exhibit reduced EBIC signal as the valleys between adjacent pyramids show the strongest collection. Other conditions yield enhanced charge collection at well defined spots on pyramid faces with no observable collection in the valleys.

EBIC↗
DOE OSTI2026

Resilience of High-Efficiency CdSeTe:As and CdSeTe:Cu Solar Cells to Proton Irradiation

Power generation in space is currently dominated by expensive III-V multi-junction photovoltaic (PV) devices and cheap crystalline silicon (c-Si) PV devices. Both of these technologies degrade rapidly in proton-radiation-rich space environments, such as the Van Allen belt. The present study of cadmium selenide telluride- (CdSeTe-) based PV devices exposed to 150-to-1500 keV proton irradiation with fluences up to 9 x 1013 cm-2 reveal a more radiation-hard alternative to III-V and c-Si PV technologies. We report on measurement and analysis of current density vs voltage (JV), external quantum efficiency (EQE), external radiative efficiency, and capacitance vs voltage (CV) characteristics. JV characteristics of As-doped CdSeTe devices show 80% remaining power conversion efficiency (PCE) relative to unexposed controls when exposed to 650 keV protons at a fluence of 1012 cm-2. Under these same irradiation conditions, Cu-doped CdSeTe devices demonstrate an even better 95% PCE retention compared with unirradiated control devices. Evidence of radiation-induced absorber p-type doping compensation is observed in the glass-side EQE at 0 V and CV characteristics of most of the irradiated CdSeTe:As devices, but clear compensation is evident only for the most heavily irradiated CdSeTe:Cu devices. Elevated blue-green photocurrent in the film-side 0 V EQE suggests a buried junction in the most heavily irradiated CdSeTe:As devices. Although CdSeTe:Cu devices are the more resilient of the CdSeTe structures, both CdSeTe-based technologies are radiation-hard when compared to c-Si and III-V multi-junction PV.

14 SOLAR ENERGY↗
DOE OSTI2024

DC Microgrid Reliability Enhancement with Adaptive Converter Thermal Management

Due to the different device selections, aging levels, and thermal dissipation performance, some converters may take additional thermal stress on switching devices than others in paralleled converter systems, which will reduce system reliability. To address this problem, this paper proposes a power-sharing strategy with adaptive thermal management. First, the temperature-based power loss model and electrical-thermal model are established. Based on that, a high-accuracy IGBT junction temperature estimate considering the power loss-temperature coupling can be achieved. Further, the thermal-sharing for all the switching devices in paralleled converters can be achieved with the proposed adaptive thermal management strategy. The proposed strategy can change the power-sharing ratio adaptively according to the system operation conditions, which will contribute to the system reliability enhancement. The effectiveness of the proposed strategy is verified through PLECS thermal simulation and joint real-time simulation with Dspace and RT-box.

DC microgrid↗
DOE OSTI2023

Role of grain boundary crystallography on void growth in FCC metals

The growth of an isolated spherical void at and near a grain boundary or a triple junction is studied by means of full-field crystal plasticity simulations with explicit representation of the void. To examine the fundamental aspects of void/grain boundary interactions in these cases, a three-dimensional large-strain elasto-viscoplastic fast-Fourier transform (LS-EVP-FFT) model with axisymmetric tensile periodic boundary conditions was developed. We employ this model to reveal the role of crystallography (grain orientations, grain boundary misorientation and inclination angle with respect to the largest component of the applied stress) and type of loading on void growth. It was found that grain orientation was the primary crystallographic feature governing void growth in strain-rate controlled simulations. For strains small enough to not significantly alter the local geometry, the overall growth of the void in bicrystal boundaries was not strongly affected by grain boundary inclination angle. The relative amount of void growth experienced within each grain in a bicrystal or tri-crystal was strongly dependent on the grain boundary inclination angle. We found a subset of orientations that exhibit faster void growth in bicrystal boundaries than inside the constituent single crystals. Last, we show that when placed primarily in one grain but near the grain boundary, void growth was similar to void growth when placed at the grain boundary. Furthermore, the growing void remained in the original grain and did not grow into the other grain, regardless of crystallographic character.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Novel animal model of multiple sclerosis: The glial connexin gap junction as an environmental tuner for neuroinflammation

Abstract Connexins, which comprise gap junctions (GJs) via homotypic/heterotypic oligomerization, act as channels to connect opposing cells, mainly in solid organs such as the skin, liver, heart, and central/peripheral nervous system. Connexins are synthesized in the endoplasmic reticulum, assembled in the Golgi apparatus as hexamers, and inserted into the cell membrane as hemichannels. These hemichannels are closed under normal conditions until they combine to form clusters and connect to neighboring cells via GJs in a head‐to‐head configuration. Opening of hemichannels, which depends on the intra‐ or extracellular environment, allows various bioactive molecules to enter into or be released from the host cells. Recent pathological studies on human demyelinating diseases have revealed alterations of connexin expression patterns in demyelinating lesions. To elucidate the molecular mechanisms of connexins in the pathomechanisms of inflammatory demyelination, we induced experimental autoimmune encephalomyelitis (EAE) in connexin 30 (Cx30)‐deficient mice, oligodendroglia‐specific Cx47‐ablated mice, and astroglia‐specific Cx43‐ablated mice. We found that both astroglial‐Cx30‐deficient mice and Cx43‐ablated mice showed amelioration of the clinical course of EAE, while oligodendroglial‐Cx47‐ablated mice showed aggravation. These findings indicate the distinct role of connexins expressed in different cell types and the substantial contribution of connexin‐mediated pathology to demyelinating disorders. The imbalance in connexin expression, which is caused by the inflammatory environment, results in an increase in hemichannels in glial cells. The release of proinflammatory molecules induced by the increase in hemichannels on activated glial cells is a crucial mechanism of demyelinating disorders.

Yamasaki, Ryo↗
DOE OSTI2026

Review on Perovskite Solar Cells: From Single‐Junction Devices to Tandem Deployment in Space

Perovskite solar cells (PSCs) have emerged as a transformative photovoltaic technology, offering high power conversion efficiency (PCE) and the potential for cost-effective manufacturing. However, stability and large-scale manufacturing remain critical challenges that must be addressed for widespread adoption. This review provides a roadmap from single-junction perovskite solar cells to tandem deployment in space. First, material-level innovations are discussed, including mixed-cation and low-dimensional perovskites, transport materials, and additives that improve thermal and structural stability while enhancing efficiency. Then, we examine both established industrial standards and emerging scientific protocols aimed at stabilizing PSCs under operational conditions, including tandem cell integration strategies and encapsulation techniques to mitigate performance degradation. Manufacturing scalability is a focal point, where deposition methods and green solvents are explored to improve large-area film uniformity and reduce environmental impact. Additionally, the increasing viability of PSCs in extraterrestrial environments is assessed, with emphasis on their performance in space applications, radiation resistance, and flexible lamination methods for deployment in extreme conditions. Progress across materials innovation, device architectures, stability testing protocols, and both terrestrial and extraterrestrial applications collectively drives perovskite photovoltaics toward higher efficiency, stability, and cost-effectiveness.

flexible PSCs↗
DOE OSTI2022

Thermal Optimization of a Silicon Carbide, Half-Bridge Power Module

This project describes the modeling process to design the packaging and heat exchanger for a half-bridge wide-bandgap (WBG) power semiconductor module. The module uses two silicon carbide, metal-oxide-semiconductor field-effect transistor (MOSFET) devices per switch position that are soldered to an aluminum nitride, direct-bond copper (DBC) substrate. A baseplate cooling configuration (e.g., no thermal grease) is used along with a water-ethylene glycol, jet-impingement-style heat exchanger. The heat exchanger was designed to be fabricated using prototyping equipment from the National Renewable Energy Laboratory, complies with automotive standards (for minimal channel sizes, flow rates, and coolant), and considers reliability aspects (i.e., erosion/corrosion). Device-scale computational fluid dynamics (CFD) is used first to design the slot jet impingement cooling configuration and compute the effective heat transfer coefficient (HTC) of the concept. The computed HTCs are then used as boundary conditions for a finite element study to optimize the package geometry (e.g., device layout and baseplate thickness) to minimize thermal resistance and minimize temperature variation between the module's four devices. Finally, a fluid manifold is designed to generate the slot jets and cool the devices. Module-scale CFD predicts a relatively low junction-to-fluid thermal resistance of 16.7 mm2 K/W, a 1.4 degrees C temperature variation between devices, and a total pressure drop of 5,860 Pa (0.85 psi) for the design. The thermal resistance of the module design is about 67% lower than the 2015 BMW i3 power electronics/modules thermal resistance.

DIRECT ENERGY CONVERSION↗
DOE OSTI2024

Numerical Simulation and Experimental Comparison of System Analysis Module 1D Mixing Model for Cold Shock Transients in the Gallium Thermal-Hydraulic Mixing Facility

Abstract Liquid metals are being investigated as coolants in many advanced reactor designs because of their high thermal conductivity and effectiveness at high temperatures. However, they often pose challenges to reactor operation and safety because of the complex thermal mixing and stratification in the plenum of pool-type reactor designs. The advanced system analysis code System Analysis Module (SAM) currently under development at Argonne National Laboratory aims to develop and implement thermal mixing models to accurately capture these complex thermal fluid behaviors. In this study, the SAM thermal mixing model was compared against experimental data from the Gallium Thermal-Hydraulic Experiment facility, a scaled liquid metal test facility that uses gallium as a surrogate fluid to investigate the stratification and thermal mixing of low-Prandtl-number fluids in the upper plenum of a liquid metal-cooled reactor. Two cold shock transient cases were used: one with stable stratified flow (Ri = 32) and one with stronger thermal mixing (Ri = 0.5). The resultant temperatures were then compared with the experimental temperatures over the entire plenum to assess the ability of the mixing models to capture the thermal behavior and to better correspond mixing parameters to various flow scenarios. Generally, the zero-dimensional mixing model was more capable of capturing the bulk temperature of the component modeled assuming that an accurate mass flow rate was provided, but it was inherently unable to capture thermal gradients in space. The one-dimensional mixing model was capable of capturing that the thermal gradients provided accurate selection of the mixing coefficients. Further, the temperature at the outlet junction was compared over time for each of the mixing models with the recorded experimental temperature. The implemented mixing models demonstrated the ability to effectively capture the overall thermal behavior for stronger mixing scenarios but struggled with more stably stratified flows. It was found that a system analysis code's covering of the entire range of different operating conditions still remains a challenging task, and it is suggested that further model and closure improvements are necessary to accurately capture complex thermal mixing and stratification phenomena.

stratification↗
DOE OSTI2022

Electrical Analysis of Pulsed Laser Annealed Poly-Si:Ga/SiOx Passivating Contacts

High-efficiency single crystalline silicon (c-Si) solar cells require precise control of dopant diffusion profiles and highly active doping concentrations through thermal annealing. Conventional furnace annealing has been successfully employed for dopant diffusion in aluminum back-surface field (Al-BSF), passivated emitter and rear contact (PERC), and Topcon cells. However, furnace annealing limits some next-generation polycrystalline silicon (poly-Si) on SiOx passivating contacts. This limitation largely affects p-type passivating contacts by not being able to: 1) control the dopant diffusion accurately to prevent B segregation at the SiOx and c-Si interface; and 2) provide highly activated doping concentrations for low contact resistivity. In this contribution, we use a nanosecond excimer laser to examine the passivation quality and electrical performance of both B- and Ga-doped poly-Si/SiOx passivating contacts. The core of this method is to take advantage of the nonequilibrium nature of the anneal through rapid melting and recrystallizing the poly-Si in a short timescale and to achieve doping concentrations above the solid solubility limit. Simulations were performed on polished surfaces to visualize the doping diffusion profiles under different laser conditions, and secondary ion mass spectrometry (SIMS) was used to verify the experimental diffusion profiles post pulsed laser melting (PLM). The results show the dopant diffusion profiles can be tuned precisely through PLM. The electrical analysis using VdP-Hall measurements reveals that the active doping concentration reached 10^21 cm-3 for B and ~2×10^21 cm-3 for Ga in poly-Si, far exceeding their solid solubility limit in Si, with a nearly 100% dopant activation achieved for B, and 20% for Ga. This highly activated dopant profile results in a low contact resistivity of <15 mO·cm^2 for B-doped contacts and <40 mO·cm^2 for Ga-doped contacts. We demonstrate that the passivation quality of the laser annealed contacts shows a linear dependency with the laser energy density and the number of pulses. PLM was also performed on random pyramid textured samples, and we found that preferential melting exists for the tips of pyramids, which can be pursued further for selective pinhole opening. Additionally, we perform thermal stability tests of these hyperdoped passivating contacts and show that under certain laser conditions, the B-doped samples exhibit good thermal stability with near full activation for temperatures up to 800°C. Lastly, we transfer this technique to a larger area by overlapping laser spots and show uniform passivation quality and electrical performance. We are currently implementing this PLM annealed p-type passivating contacts into double-side back-junction poly-Si/SiOx passivating contact devices. Our results show that PLM can not only enable the next generation of high-efficiency c-Si photovoltaics technology but can also benefit the c-Si integrated circuit industry through hyperdoping other semiconductors with atoms that may otherwise have a low solubility.

doping diffusion profile↗
DOE OSTI2025

Assessment of Blocking Contacts in Suppressing Polarization Effects in CsPbBr 3 Perovskite Detectors

The CsPbBr 3 perovskite has garnered significant attention as a room-temperature semiconductor for hard radiation detection due to straightforward synthesis, scalable crystal growth, low cost, and excellent energy resolution. However, despite these advantages, at ambient temperature, CsPbBr 3 devices may experience performance deterioration and irreversible failure due to “polarization” induced by electromigration of ions to electrical connections on the device. In this study, we tested several contact materials and their optimization deposition techniques to assess the stability of high-performance CsPbBr 3 γ-ray detectors. Metals, with low work functions (Ti, In, Sn, Sb, Pb, Bi, Al, Au, and TiC) and high-work-function (Au or Pt) contacts, were used to form different Schottky junctions using vacuum thermal evaporation, electron-beam evaporation, and sputtering methods. These detectors were tested in intermittent and continuous modes to assess their stability. Among the tested detectors, the Bi/CLB/Pt electrode configuration demonstrated superior stability, operating effectively for 11 months under periodic testing and 16 days under continuous testing. In contrast, other configurations functioned only for a few months under intermittent conditions. Upon incorporating a ~40-nm-thick TiC passivation layer on the anode side (Bi/TiC/CLB/Pt), the CLB device operated continuously for 36 days without degradation. In many cases, the failure mode of the devices was due to the degradation of the anode. Here, the chemical changes in the fresh and deteriorated anodes were characterized using scanning electron microscopy and energydispersive X-ray spectroscopy

CsPbBr3 perovskite↗
DOE OSTI2021

Reference electrode for electrochemical measurements at high temperatures

A reference electrode which is stable over a wide range of temperatures, pressures and chemical conditions is provided. The subject reference electrode according to the present invention comprises a tubular enclosure composed of quartz having a distal, closed end and a proximal, open end. An insulating ceramic rod is seemingly connected to the opening in the closed distal end of the enclosure to form micro-cracks between the ceramic rod and the quartz enclosure (called a cracked junction, CJ). The CJ gives a very tortuous path for ion conduction from inside the reference electrode (RE) to a working electrode (WE). Inside the tubular enclosure is an electrical lead (e.g., a silver wire) disposed in an electrolyte comprising a mixture of alkaline metal salts (e.g., AgCl and KCl), extending from the electrolyte upward through a sealing means at the proximal end of the quartz enclosure.

Gervasio, Dominic Francis↗
DOE OSTI2025

Packaging a 650V/400A GaN Half-bridge Power Module with Ultra-low Parasitics for Electric Vehicle Drive Applications

This paper proposes a compact and efficient half-bridge power module with three 650 V / 150 A GaN dies in parallel. The power module incorporates a main power printed circuit board (PCB), an interface PCB, and a flex PCB to achieve low parasitics in both power loop and gate-side connection, resolving the issue of high parasitics typically encountered with wire bonding in high-current applications. Additionally, the interface PCB decouples the design constraints between the power loop and the gate loops. The proposed design is optimized with a vertical loop configuration to reduce power loop inductance through magnetic flux cancellation. Finite element analysis indicates that the power loop inductance is 0.58 nH at 100 MHz, while the maximum die junction temperature reaches 131 °C under an ambient temperature of 65 °C and a load current of 385 A. The proposed multi-piece PCB structure reduces the inductance of the drive circuit to minimize EMI and to mitigate false triggering. At the same time, it reduces impedance mismatches across different driver circuits, thereby achieving dynamic current sharing in multi-chip parallel configurations. Under simulation conditions of 400 V / 385 A, the current imbalance among chips was limited to 5 A. A 400 V / 385 A double-pulse test was conducted to experimentally validate the performance of the proposed power module.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2021

Comprehensive analysis of differentially expressed mRNA and circRNA in Ankylosing spondylitis patients’ platelets

Highlights: • 4996 mRNAs and 2942 circRNAs were identified differentially expressed in platelets of AS patients. • Several platelet-derived immune mediators were upregulated to regulate the interaction between platelets and immune cells. • Two downregulated circRNA were identified, and the corresponding circRNA-miRNA-mRNA regulatory network was constructed. • mRNAs and circRNAs found herein could be used as diagnostic biomarkers or new therapeutic targets. Ankylosing spondylitis (AS) is a chronic inflammatory disease significantly decreasing the quality of life. Platelets play an important and active role in the development of AS. Accumulating evidence demonstrated platelets contain diverse RNA repository inherited from megakaryocytes or microvesicles. Platelet RNAs are dynamically affected by pathological conditions and could be used as diagnostic or prognostic biomarkers. However, the role of the platelet RNAs in AS is elusive. In this study, we compared mRNA and circRNA profiles in platelets between AS patients and healthy controls using RNA sequencing and bioinformatic analysis, and found 4996 mRNAs and 2942 circRNAs were differently expressed. The significantly over-expressed mRNAs in AS patients are involved in platelet activity, gap junction, focal adhesion, rap1 and toll and Imd signaling pathway. The previous identified platelet-derived immune mediators such as P2Y1, P2Y12, PF4, GPIbα, CD40L, ICAM2, CCL5 (RANTES), TGF-β (TGF-β1 and TGF-β2) and PDGF (PDGFB and PDGFA) are also included in these over expressed mRNAs, implying these factors may trigger inflammatory cascades and promote the development of AS. Additionally, we found two down-regulated circRNA (circPTPN22 and circFCHSD2) from the intersection analyses of platelets and spinal ligament tissues of AS patients. The circRNA-miRNA-mRNA regulatory network of these two circRNAs was constructed, and the target mRNAs were enriched in Th17 cell differentiation, inflammatory bowel disease, cell adhesion molecules, cytokine-cytokine receptor interaction, Jak-STAT and Wnt signaling pathway, all these pathways participate in the bone remodeling and pro/anti-inflammatory immune regulation in AS. Then, qRT-PCR was performed to validate the expression of selected key mRNAs and circRNAs and the results demonstrated that the expression levels of P2Y12, GPIbα, circPTPN22 and circFCHSD2 were consistent with the sequencing analysis. In addition, the high expression of five predicted miRNAs interacting with circPTPN22 and circFCHSD2 were also detected in AS by qRT-PCR. Taken together, our study presents a comprehensive overview of mRNAs and circRNAs in platelets in AS patients and offers new insight into the mechanisms of platelet involving in the pathogenesis of AS. The mRNAs and circRNAs identified in this study may serve as candidates for diagnosis and targeted treatment of AS.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Buffer-IPyC separation process in TRISO fuel particles simulated with Bison code

During High Temperature Gas-cooled Reactor (HTGR) operation, tristructural isotropic (TRISO) coated-particle fuel undergoes irradiation-induced changes in morphology and thermomechanical properties. Experimental results from the Advanced Gas Reactor (AGR) Fuel Development and Qualification Program show, among other things, the mechanism of gap formation between the buffer and inner pyrolytic carbon (IPyC) layers, which could be explored further via computational simulations using the Bison code. Two simulation models were developed, the debonding restricted model, where no gap formation between buffer and IPyC layers is permitted, and the debonding enabled model, where the gap between those layers is created. The inputs of the simulated models are based on the irradiation conditions from the AGR-1 experiment. The research included simulations on spherical and aspherical fuel types. Under the specific temperatures and fluences of the AGR-1 irradiation experiment, and the Bison simulations, it was concluded that the most common scenario is a gap formation along the buffer-IPyC interface, while the least possible scenario is the situation where there is no gap formation at the buffer-IPyC junction. The computational results confirmed that the sphericity of the fuel influences the thickness of the gap that occurs at the buffer-IPyC junction, in a way that with increasing aspect ratio the gap thickness increases. The results obtained for spherical and aspherical fuel are nearly identical. Finally, performed simulations match conclusions observed from the AGR-1 experiment, which as such shows that the Bison code is a good computational method for simulating the TRISO fuel. Future simulations will include the validation of performed research and comparison of the results between Bison and PARFUME codes.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗