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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Testing effects of Lorentz invariance violation in the propagation of astroparticles with the Pierre Auger Observatory

Lorentz invariance violation (LIV) is often described by dispersion relations of the form E i 2 = m i 2 +p i 2 +δ i,n E 2+n with delta different based on particle type i , with energy E, momentum p and rest mass m. Kinematics and energy thresholds of interactions are modified once the LIV terms become comparable to the squared masses of the particles involved. Thus, the strongest constraints on the LIV coefficients δ i,n tend to come from the highest energies. At sufficiently high energies, photons produced by cosmic ray interactions as they propagate through the Universe could be subluminal and unattenuated over cosmological distances. Cosmic ray interactions can also be modified and lead to detectable fingerprints in the energy spectrum and mass composition observed on Earth. The data collected at the Pierre Auger Observatory are therefore possibly sensitive to both the electromagnetic and hadronic sectors of LIV. In this article, we explore these two sectors by comparing the energy spectrum and the composition of cosmic rays and the upper limits on the photon flux from the Pierre Auger Observatory with simulations including LIV. Constraints on LIV parameters depend strongly on the mass composition of cosmic rays at the highest energies. For the electromagnetic sector, while no constraints can be obtained in the absence of protons beyond 10 19 eV, we obtain δ γ,0 > -10 -21 , δ γ,1 > -10 -40 eV -1 and δ γ,2 > -10 -58 eV -2 in the case of a subdominant proton component up to 10 20 eV. For the hadronic sector, we study the best description of the data as a function of LIV coefficients and we derive constraints in the hadronic sector such as δ had,0 < 10 -19 , δ had,1 < 10 -38 eV -1 and δ had,2 < 10 -57 eV -2 at 5σ CL.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

DCIF Westerly Granite AE Stress Effect Test (Task 3-1)

Directional Cooling-Induced Fracturing (DCIF) experiments were conducted on rectangular Westerly granite blocks (width=depth=4.0", height=2.0"). Liquid nitrogen was poured in a small, 1"-diameter copper cup attached to the top of the sample, and the resulting acoustic emissions (AEs) and temperature changes on the surface of the sample were monitored. Several confining stresses were applied bi-axially to the sides of the samples so that the onset of AE activity and the stress applied to the sample were correlated. The obtained AEs were used to determine the microcracking source locations and amplitude, and the associated moment tensors. Included in this submission are the animations of the AE locations and graphics displaying the measured temperature-AE activity changes for different stresses.

15 GEOTHERMAL ENERGY↗
DOE OSTI2014

Thermal-Hydraulic Analysis of an Experimental Reactor Cavity Cooling System with Air. Part I: Experiments; Part II: Separate Effects Tests and Modeling

This experimental study investigates the thermal hydraulic behavior and the heat removal performance for a scaled Reactor Cavity Cooling System (RCCS) with air. A quarter-scale RCCS facility was designed and built based on a full-scale General Atomics (GA) RCCS design concept for the Modular High Temperature Gas Reactor (MHTGR). The GA RCCS is a passive cooling system that draws in air to use as the cooling fluid to remove heat radiated from the reactor pressure vessel to the air-cooled riser tubes and discharged the heated air into the atmosphere. Scaling laws were used to preserve key aspects and to maintain similarity. The scaled air RCCS facility at UW-Madison is a quarter-scale reduced length experiment housing six riser ducts that represent a 9.5° sector slice of the full-scale GA air RCCS concept. Radiant heaters were used to simulate the heat radiation from the reactor pressure vessel. The maximum power that can be achieved with the radiant heaters is 40 kW with a peak heat flux of 25 kW per meter squared. The quarter-scale RCCS was run under different heat loading cases and operated successfully. Instabilities were observed in some experiments in which one of the two exhaust ducts experienced a flow reversal for a period of time. The data and analysis presented show that the RCCS has promising potential to be a decay heat removal system during an accident scenario.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Development of Fast-Pulse Neutron Generation Capability by Beam-Target Interaction on HERMES-III for Radiation Effects Testing (Final Report)

The goal of this project is to produce an intense neutron pulse on HERMES III using the beam-target method with an intense proton beam. The potential advantage of proton use is that the generated neutron spectrum contains significantly more high-energy neutrons than that produced by electron-beam generated photoneutrons using the same facility. And compared to (D,T) facilities such as NIF, no tritium (or deuterium) is required for this process. To achieve the mid ~10 10 neutrons/cm 2 at a test object location listed as the goal in the Proposal, it was proposed that a radial ion diode previously developed and fielded at the 6 MeV - level be extended in performance to the full-power level on HERMES, with proton energies in the neighborhood of 15 MeV. This Report details the successful development of the radial ion diode at full power, which required more durable hardware which could be fielded at a one shot/day basis with minimal debris and activation (an important concern), and which could be substituted quickly into the normal negative-polarity bremsstrahlung source experiments without compromising the main HERMES validation mission. As direct measurement of proton beam characteristics proved challenging, the Project relied on an extensive series of simulations, LSP for beam dynamics and MCNP to characterize neutron output. Simulation results will be discussed, including the conclusion that neutron measurements made are consistent with an MCNP-predicted proton beam of 16 MeV peak energy, and 200 kA peak current. This Project also contributes to physics understanding of the use of inductive voltage adder (IVA) platforms to drive diode loads. Since such diodes operate independently of the physics of IVAs, the IVA-diode coupling requires matching of the MITL flow to the requirements of ion diode operation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

High Fluence Active Irradiation and Combined Effects Testing of Sapphire Optical Fiber Distributed Temperature Sensors [Slides]

All objectives have been completed. Heated irradiation indicates potential for sapphire fiber-based sensors to be used in extreme environments beyond silica fiber temperature limits. Sapphire optical fiber may not be appropriate for high fluence applications. Clad sapphire optical fibers have a temperature-dependent attenuation that has not been observed in unclad sapphire. With the appropriate pre-treatments and data post-processing, sapphire optical fiber has the potential to serve as a distributed sensor up to 1700ºC.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Status Report on Separate Effects Testing of Thermal Conductivity of U-Zr Alloy

Phases by definition in an alloy system have distinct physical and chemical properties, including thermal conductivity. The goal of this multi-year study is to show that the different phases present in the U-Zr system indeed do have different thermal conductivities. This study will provide meso-scale (10-100 µm) experimental observations using the Thermal Conductivity Microscope (TCM) of phase dependent thermal conductivity. The results of this study may indicate the need to reconsider the application of homogeneous medium assumption for metallic nuclear fuel that is currently used in fuel performance modeling, and could provide input for improving such model using a heterogeneous phase dependent assessment of thermal properties. The local thermal conductivity values from the TCM will be compared to the bulk measurements to validate this work. Twelve alloy samples with varying Zr compositions and heat treatments were fabricated for the initial phase of this study to characterize the individual phases present in the U-Zr system. The gamma body-centered cubic (BCC) phase was successfully identified in the appropriate size for TCM measurement. Next steps in this work will include identification of remaining phases in the U-Zr alloy system. Thermal conductivity will be measured in those phase areas of the materials and used to assess fuel performance codes for improvements.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗