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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

A FEASIBILITY STUDY ON CRACK REPAIR IN AUSTENITIC STAINLESS STEEL DRY STORAGE CANISTERS USING ISOTHERMAL FRICTION STIR WELDING

In recent time, solid state crack repair techniques in spent nuclear fuel dry storage canisters (SNF-DSC) have garnered significant interest. Plates of austenitic stainless steels are usually arc welded to fabricate the cylindrical canisters which are prone to chloride-induced stress corrosion cracking. Friction stir welding (FSW) is considered to be a potential candidate for damage repair. In this work, electrical discharge machining was used to simulate cracks in 304L stainless steel plates of 12.7 mm thickness. Subsequently, isothermal FSW was carried out at two different temperatures (725 and 825°C) in order to repair the simulated crack. Microstructure-mechanical property correlations in FSWed plates were studied in detail. Significant grain refinement observed in the stir zone (SZ) was attributed to dynamic recrystallization occurring during FSW. A comparison of Vickers microhardness showed higher hardness and homogeneity in the 725°C SZ than its 825°C counterpart. The fraction of S3 boundary is found to be low in the SZ as compared to base metal (BM). Yield strength of the joints was found to be approximately 100 MPa higher than that of the BM accompanied by a drop in ductility by a factor of 2. Residual stress profile across 825°C weld was measured using x-ray diffraction.

Bhattacharyya, Madhumanti↗
DOE OSTI2020

On the Feasibility of Using Reduced-Precision Tensor Core Operations for Graph Analytics

Today’s data-driven analytics and machine learning workload have been largely driven by the General-PurposeGraphics Processing Units (GPGPUs). To accelerate dense matrix multiplications on the GPUs, Tensor Core Units (TCUs) have been introduced in recent years. In this paper, we study linear-algebra-based and vertex-centric algorithms for various graph kernels on the GPUs with an objective of applying this new hardware feature to graph applications. We identify the potential stages in these graph kernels that can be executed on the Tensor Core Units. In particular, we leverage the reformulation of the reduction and scan operations in terms of matrix multiplication [1]on the TCUs. We demonstrate that executing these operations on the TCUs, available inside different graph kernels, can assist in establishing an end-to-end pipeline on the GPGPUs without depending on hand-tuned external libraries and still can deliver comparable performance for various graph analytics.

Graph algorithms, GPU computing↗
DOE OSTI2021

BETO 2021 Peer Review - Feasibility Study of Utilizing Electricity to Produce Intermediates from CO2 and Biomass

Capturing and converting CO2 generated from bioethanol facilities into valuable products, leveraging renewable electricity as the primary energy input, could increase overall biorefinery carbon utilization by as much as 40% and provide a means to decarbonize fuels and chemicals production. However, significant uncertainty exists around the costs, carbon intensity, risks, and technical challenges associated with electron-driven CO2 reduction. Thus, the overarching objective of this project is to guide existing and future research and development efforts by addressing these knowledge gaps for utilizing renewable electricity and CO2 to improve biorefinery economics and carbon utilization. By September 2023, this project will develop and publish a comprehensive design report for the integration of CO2 utilization into two existing conceptual biorefinery designs, which will include conceptual process models, pioneer and nth plant economics, identification and quantification of technological risks, and projections for future cost reductions.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2021

Feasibility and Prospects of the High Resolution Rapid Refresh Model For Dynamic Line Rating

The ampacity of transmission lines is defined as the maximum amount of current the conductor can safely carry. It is necessary for transmission line operators to apply ampacity limits due to the thermal properties of the conductor. Dynamic Line Rating (DLR) is a technology and technique that uses the environmental conditions or a set of the conditions to calculate the ampacity of the conductor. The way the DLR is calculated has depended upon some amount of physical technology to implement the solution. The High Resolution Rapid Refresh (HRRR) Model is an atmospheric model that may provide enough resolution to perform dynamic line rating without any hardware at all. The objective is to use this model to perform Dynamic Line Rating. This will solve two of the most pervasive problems in Dynamic Line Rating, how to instrument a transmission line hundreds of miles long and then how to predict near future ampacity sufficient for transmission operators to effectively use, This technique will use the Idaho National Laboratory site as the test location for analysis. The High Resolution Rapid Refresh model is a reliable, freely available, and well-maintained weather forecasting model for the entire United States of America. The model provides enough special resolution that additional local weather monitoring devices at location are not necessary to conduct dynamic line rating. The HRRR ratings are lower on average than the locally measured ratings which allows for an additional margin of safety. The adoption of using purely digital methods for dynamic line rating could allow for wide scale adoption of the technology with very little overhead expenditure of implementation.

17 WIND ENERGY↗
DOE OSTI2022

Fast cycling HTS based superconducting accelerator magnets: Feasibility study and readiness demonstration program driven by neutrino physics and muon collider needs

Development of energy-efficient fast cycling accelerator magnets is critical for the next generation of proton rapid cycling synchrotrons (RCS) for neutrino research and booster accelerators of future muon colliders. We see a unique opportunity for having such magnets to be built on base of High Temperature Superconductors (HTS). Besides being superconducting at relatively high temperatures, rare-earth HTS tapes have shown very small AC losses compared to low-temperature NbTi superconductor cables. Recent tests of the HTS-based 0.5 m long two-bore superconducting accelerator magnet have shown record high dB/dt ramping rates of about 300 T/s at 10 Hz repetition rate and 0.5 T B-field span. No temperature rise in 6 K cooling He was observed within the 0.003 K error setting the upper limit on the cryogenic power loss in the magnet conductor coil to be less than 0.2 W/m. Based on this result we outline a possible upgrade of this test magnet design to 2 T B-field in the 10 mm beam gap with the dB/dt ramping rates up to 1000 T/s. The power test results of this short sample magnet will be used to project both cryogenic and electrical power losses as a function of the magnet B-field and the dB/dt ramping rates. Then these projections will be scaled to the range of expected accelerator magnet beam gaps and B-fields for the proton and muon RCS accelerators. We invite collaborators to join these studies and call for support of the R&D program aimed at comprehensive demonstration of this approach that includes design, construction, and power tests of a long prototype of the HTS-based fast-cycling accelerator magnet by 2028.

43 PARTICLE ACCELERATORS↗