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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Impact of Grain Size on Performance Degradation of TREAT LEU

We argue that radiation damage induced degradation of thermal conductivity does not set a lower limit on fuel grain sizes for the low enriched uranium fuel design of the Transient Reactor Test Facility (TREAT). Earlier work reports that smaller grains cause a larger degradation of thermal conductivity than larger grains constraining the smallest feasible size of fuel grains. This work assesses TREAT’s transient performance in the presence of radiation damage. The difference between the two studies is in treating damaged and fresh graphite as serial (this work) or parallel (previous) heat resistors. We use a multiphysics model of TREAT fuel grains to compute the reduction in transient capability measured by the total deposited energy as a function of irradiation dose. We find that radiation damage has a negligible effect on energy deposition.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Impact of GW170817 for the nuclear physics of the EOS and the r-process

The recent LIGO/Virgo detection of gravitational radiation from GW170817 bears the clear signature of a binary neutron star merger and has validated a number of theoretical predictions. High-energy radiation in the form of a short gamma-ray burst was observed 1.7 s following the merger, and an extended optical/infrared afterglow lasting weeks was observed by dozens of observatories. Short gamma-ray bursts had been thought to be produced by mergers, and the afterglow is the predicted signal of radioactive decays from decompressing neutron-rich matter catastrophically ejected from the merging stars. The afterglow provided solid evidence that neutron star mergers are a major, if not primary, source of r-process nuclei, that half of all nuclei heavier than iron formed from the rapid capture of neutrons. Although this idea was proposed nearly 45 years ago, it was largely ignored in favor of a supernova mechanism. Over the last decade, however, evidence has been accumulating that supernovae are not the primary r-process source. GW170817 may have finally settled this question, which has been one of the thorniest problems in nuclear physics and astrophysics. This article presents my personal perspective of this paradigm shift.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Impact of Structural Defects and Hydronium Ion Concentration on the Stability of Zeolite BEA in Aqueous Phase

The presence of fluoride anions in the synthesis gel leads to zeolite BEA with high hydrothermal stability. This longer lifetime is caused by a lower concentration of internal silanol defects that are sites of the initial framework hydrolysis eventually destroying the lattice structure. The lifetime of these zeolites was the higher the lower the concentration of framework bridging hydroxyl groups that form hydronium ions was. While lattice hydrolysis was initiated at defect sites in all cases, the role of defects became less important as the concentration of hydronium ions increased. At higher concentration of hydrated hydronium ions, the presence of water associated with the hydrated hydronium ions limits the useful lifetime of zeolite catalysts in water. For such materials, the selective hydrophobization of the external surface extends the lifetime. Acknowledgments: S.P. and M.A.D. acknowledge support by the Materials Synthesis and Simulation Across Scales (MS3 Initiative) conducted under Laboratory Directed Research & Development Program at PNNL. H.S. and H.W. were supported by the Chemical Transformation Initiative (CTI) conducted under Laboratory Directed Research & Development Program at PNNL. J.A.L. was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.

Prodinger, Sebastian↗