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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Establishing Maximal Core Excess Reactivity Envelope for TREAT Test Vehicle Insertion

The Transient Reactor Test (TREAT) Facility is an air-cooled reactor composed of graphite-urania fuel encapsulated in zirconium alloy canisters and surrounded by ~2 ft (~61 cm) of nuclear grade graphite. The primary role of TREAT is to provide in-pile nuclear-heated safety research via transient testing [1]. The following work represents further analyses building upon previously reported work to support larger volume test vehicles within TREAT [2]. The Broad Use Specimen Transient Experiment Rig (BUSTER) provides ample versatility for numerous transient test concepts. However, future testing and experiment needs will require testing environments of different in-core footprints. The versatility of TREAT allows for the development of variegated core layouts with key limitations emplaced as operational safety temperature restrictions and available core reactivity. The focus of this current effort is to gauge core arrangements for TREAT core loadings to support centralized experimental testing of varying dimensional capacity. The total core excess reactivity (ER) was computed for different arrangements to establish comparison tables that enable ready assessment of core ER available for future experiment concepts. Test vehicle worths would then be necessary to establish available ER to support transient testing requirements and to perform reactor performance and safety calculations [3,4].

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2018

Maximizing the habitat restoration potential of controlled releases at hydropower dams; Understanding impacts of hydrograph form on sediment transport

Regulation of streamflow for hydropower often alters natural hydrographs, commonly reducing peak flows, increasing baseflows, and increasing ramping rates. Simultaneously, reservoirs typically trap sediment, reducing the supply to the reach downstream of the dam. These changes to the flow regime and sediment supply impact channel morphology and sediment transport processes in ways that reduce the diversity and suitability of instream habitat. A variety of restoration approaches have attempted to mitigate for some of these changes and a growing number include releases of high flows designed to mimic key characteristics of the pre-regulation hydrograph. One example is the Trinity River, CA, where the addition of augmentation gravel to the channel has been combined with high flows designed to restore portions of the pre-regulation hydrograph to improve channel conditions for spawning fish on the Trinity River, CA. Another example is the high-flow experiments on the Colorado River through the Grand Canyon that aim to restore eroding sand bars that not only provide habitat but camping for rafting groups. More projects that restore portions of the pre-regulation hydrograph are likely in the future because the Federal Energy Regulatory Commission (FERC) requires habitat mitigation efforts in the relicensing process for hydropower facilities. However, the outcomes of these costly restoration efforts are often hard to predict because little is known about how hydrograph form actually impacts channel morphology and bedload transport in rivers. Here we summarize the results of two flume experiments designed to investigate the impacts of hydrograph form on the morphology of a channel bar and bedload transport processes. The first experiment primarily investigated the impacts of hydrograph recession rate on the morphology of a channel-bar in a sand bed channel. Additional runs examined the combined effects of hydrograph recession and a dense patch of vegetation on bar form. The second flume experiment investigated bedload transport processes in an armored, gravel bed channel during hydrographs with varying form. It documented total bedload flux for a hydrograph, bedload flux rates, persistence of the coarse armor surface, and changes in bed surface structure. Both experiments observed links between hydrograph form and the resulting bar morphology or bedload transport processes, providing insight into ways that high flow hydrographs can be designed to better facilitate restoration goals downstream of hydropower facilities.

13 HYDRO ENERGY↗
DOE OSTI2020

Maximizing Yield with Improved Single-Axis Backtracking on Cross-Axis Slopes: Preprint

Many tracking PV systems avoid row-to-row shading by backtracking in morning and afternoon. Because the common single-axis backtracking implementation assumes the array is in a horizontal plane, it does not fully prevent row-to-row shading in arrays installed on cross-axis slopes. This paper simulates the effect of reduced self-shading on annual production with two modified backtracking strategies. Depending on the array geometry and the steepness of the cross-axis grade, using a modified backtracking strategy improved annual yield by 3-10%.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2022

Biomass to Biochar: Maximizing the Carbon Value - Executive Summary

Converting biomass to biochar presents exciting opportunities to mitigate climate change, improve forest and soil health, decrease wildfire risk, bolster ecosystem services, and revitalize rural economies. Our expert panel examined how biomass is harvested, converted to biochar and applied and where operational changes and funding could significantly magnify biochar's contributions. To advance knowledge and efficacies, we found that a rigorous combination of coordinated long-term research, market research and development and enhancement of business support infrastructure that leads to collaborative policy development is essential. We also identified how barriers to five specific biochar technology sectors could be overcome and provide guidelines for effective funding.

agriculture↗