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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI1994

Nuclear Safety [Vol. 35, No. 1, January-June 1994]

Nuclear Safety is a review journal that covers significant developments in the field of nuclear safety. Its scope includes the analysis and control of hazards associated with nuclear energy, operations involving fissionable materials, and the products of nuclear fission and their effects on the environment. Primary emphasis is on safety in reactor design, construction, and operation; however, the safety aspects of the entire fuel cycle, including fuel fabrication, spent-fuel processing, nuclear waste disposal, handling of radioisotopes, and environmental effects of these operations, are also treated. Table of Contents for this issue follows. THE CHERNOBYL ACCIDENT: 1 Chernobyl Accident Management Actions, A. R Sich; GENERAL SAFETY CONSIDERATIONS: 25 The IAEA-ASSET Approach to Avoiding Accidents is to Recognize the Precursors to Prevent Incidents, F. Reisch; ACCIDENT ANALYSIS: 36 A Review of the Available Information on the Triggering Stage of a Steam Explosion, D. F. Fletcher; 58 Analysis and Modeling of Flow-Blockage-Induced Steam Explosion Events in the High-Flux Isotope Reactor, R. P. Taleyarkhan, V. Georgevich, C. W. Nestor, U. Gat, B. L. Lepard, D. H. Cook, J. Freels, S. J. Chang, C. Luttrell, R. C. Gwaltney, and J. Kirkpatrick; 74 An Analysis of Disassembling the Radial Reflector of a Thermionic Space Nuclear Reactor Power System, M. S. El-Genk and D. V. Paramonov; CONTROL AND INSTRUMENTATION: 86 Standards for High-Integrity Software, D. R. Wallace, D. R. Kuhn, L M. Ippolito, and L. Beltracchi; DESIGN FEATURES: 98 Adoption of New Design Features for the Next Generation Nuclear Power Reactors, L. S. Tong; 114 Review of Nuclear Piping Seismic Design Requirements, G. C. Slagis and S. E. Moore; ENVIRONMENTAL EFFECTS: 128 PC-Based Probabilistic Safety Assessment Study for a Geological Waste Repository Placed in a Bedded Salt Formation, S. A. Khan; OPERATING EXPERIENCES: 142 Managing Aging in Nuclear Power Plants: Insights from NRC’s Maintenance Team Inspection Reports, A. Fresco and M. Subudhi; 150 Reactor Shutdown Experience, Compiled by J. W. Cletcher; 153 Selected Safety-Related Events, Compiled by G. A. Murphy; RECENT DEVELOPMENTS: 158 Reports, Standards, and Safety Guides, D. S. Queener; 168 Proposed Rule Changes as of Dec. 31, 1993; ANNOUNCEMENTS: 177 Symposium on Radioactive and Mixed Waste—Risk as a Basis for Waste Classification; 177 1995 Incineration Conference 178 Ninth Power Plant Dynamics Control and Testing Symposium; 174 The Authors

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Superallowed 0 + → 0 + nuclear β decays: 2020 critical survey, with implications for V ud and CKM unitarity

A new critical survey of all half-life, decay-energy and branching-ratio measurements related to 23 superallowed 0 + → 0 + β decays is presented. Included are 222 individual measurements of comparable precision obtained from 174 published references. Compared with our last survey in 2015, we have added results from 28 new publications and eliminated an approximately equal number whose results have been superseded by much more precise modern data. We obtain world-average ft values for each of the 21 transitions that have a complete set of data, then apply radiative and isospin-symmetry-breaking corrections to extract “corrected” Ft values. Fifteen of these Ft values now have a precision of 0.3% or better and all take the same value within statistics, as expected from conservation of the vector current. Their average, Ft¯, when combined with the muon lifetime, yields the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa matrix, V ud = 0.97373 ± 0.00031. This is lower than our 2015 result by one standard deviation and its uncertainty is increased by 50%. This is a consequence, not of any shifts in the experimental data, but of new calculations for the radiative corrections. The lower V ud value now leads to greater tension in the top-row test of unitarity in the CKM matrix. Updates in experimental data have independently led to a factor-of-two tighter limit being set on the possible existence of a scalar interaction. In conclusion, the new limit on Fierz interference is b F ≤ 0.0033 at the 90% confidence level.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2016

M31N 2008-12a-The Remarkable Recurrent Nova in M31-Panchromatic Observations of the 2015 Eruption

The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption 10 times, including yearly eruptions from 2008 to 2014. With a measured recurrence period of Prec = 351+/-13 days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground- and space-based follow-up programs. In this paper we present the 2015 detection, visible to near-infrared photometry and visible spectroscopy, and ultraviolet and X-ray observations from the Swift observatory. The LCOGT 2 m (Hawaii) discovered the 2015 eruption, estimated to have commenced at August 28.28 +/- 0.12 UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities approx. 13,000 km/s, possibly collimated outflows. Photometric and spectroscopic observations of the eruption provide strong evidence supporting a red giant donor. An apparently stochastic variability during the early supersoft X-ray phase was comparable in amplitude and duration to past eruptions, but the 2013 and 2015 eruptions show evidence of a brief flux dip during this phase. The multi-eruption Swift/XRT spectra show tentative evidence of high-ionization emission lines above a high-temperature continuum. Following Henze et al. (2015a), the updated recurrence period based on all known eruptions is Prec 174 +/- 10 days, and we expect the next eruption of M31N 2008-12a to occur around 2016 mid-September.

cataclysmic variables – stars: individual (M31N ↗
NASA NTRS2016

Seasonal Variation of Total Mercury Burden in the American Alligator (Alligator Mississippiensis) at Merritt Island National Wildlife Refuge (MINWR), Florida

Seasonal variation of mercury (Hg) is not well studied in free-ranging wildlife. Atmospheric deposition patterns of Hg have been studied in detail and have been modeled for both global and specific locations with great accuracy and correlates to environment impact. However, monitoring these trends in wildlife is complicated due to local environmental parameters (e.g., rainfall, humidity, pH, bacterial composition) that can affect the transformation of atmospheric Hg to the biologically available forms. Here, we utilized an abundant and healthy population of American alligators (Alligator mississippiensis) at Merritt Island National Wildlife Refuge (MINWR), FL, and assessed Hg burden in whole blood samples over a span of 7 years (2007 2014; n 174) in an effort to assess seasonal variation of total [Hg]. While the majority of this population is assumed healthy, 18 individuals with low body mass indices (BMI, defined in this study) were captured throughout the 7 year sampling period. These individual alligators exhibited [Hg] that were not consistent with the observed overall seasonal [Hg] variation, and were statistically different from the healthy population of alligators. The alligators with low BMI had elevated concentrations of Hg compared to their age/sex/season matched counterparts with normal BMI. Statistically significant differences were found between the winter and spring seasons for animals with normal BMI. The data in this report supports the conclusion that organismal total [Hg] do fluctuate directly with seasonal deposition rates as well as other seasonal environmental parameters, such as average rainfall and prevailing wind direction. This study highlights the unique environment of MINWR to permit annual assessment of apex predators, such as the American alligator, to determine detailed environmental impact of contaminants of concern.

Hg↗
NASA NTRS1961

ANALYSIS OF CRYOGENIC PROPELLANT FEED SYSTEMS FOR ELECTROTHERMAL ENGINES.

An analytical investigation was made of the problems associated with the long-term storage and control of flow of cryogenic propellants for electrothermal engines. Storage of 35 to 174 pounds of propellant for three years is made difficult by the high ratio of surface area to storage tank volume, and the resulting high rate of heat leak. Vented and non-vented storage, storage as high pressure gas, and the use of refrigeration were considered. Recommended storage methods are: for ethane and ammonia vented storage - by venting propellant stored in excess of mission requirements; for hydrogen and helium - by non-vented storage of cold supercritical vapor; and for methane by storage as a non-vented two-phase mixture. The optimum propellant density in the storage tank and optimum insulation thickness were also determined. Design charts were developed for hydrogen and helium, for estimating the maximum pressure expected in non-vented storage tanks, as function of mission requirements. Separation of the constituent phases of liquid-vapor mixtures is achieved by throttling the two-phase mixture to a lower pressure (and temperature) and vaporizing the liquid in the mixture by heat exchange with the contents of the storage tank. The time limitations for continuous use of this method are discussed. Linde super insulations SI-44 or SI -91 are recommended for insulation. Precooling the insulation to temperatures below the steady state level with cold helium vapor before or during fueling of the storage tank eliminates the flow of heat to the tank contents during countdown and take-off. The masses, sizes, and power requirements of the recommended systems are low. The controls are simple and reliable. From the equations and charts in this report the components of the system for a particular mission can be sized. Recommendations are given for experimental work required for the development and testing of such components.

ELECTROTHERMAL ENGINE↗
NASA NTRS2000

New Alloys for Electroformed Replicated X-Ray Optics

The process of electroforming x-ray mirror shells off a superpolished mandrel has been widely used. The recently launched XMM mission is a good example of this, containing 174 such mirror shells of diameters ranging from 0.3-0.7 m and thicknesses of 0.47-1.07 mm. To continue to utilize this technique for the next generation of x-ray observatories, where ever-larger collecting areas will be required within the constraints of tight weight budgets, demands that new alloys be developed that can withstand the large stresses imposed on very thin shells by the replication and handling processes. Towards this end, we began a development program in late 1997 to produce a high-strength alloy suitable for electroforming very thin high-resolution x-ray optics. The requirements for this task are quite severe; not only must the electroformed deposit be very strong, it must also have extremely low residual stresses to prevent serious figure distortions in large thin-walled shells. Further, the electroforming must be performed at near room temperature, as large temperature changes will modify the figure of the mandrel, in an environment that is not corrosive for the mandrel. The figure of merit for the strength of the electroformed deposit is its Precision Elastic Limit (PEL). This is a measure of permanent strain, at the few parts per million level, under applied stress. Pure nickel is very ductile and will permanently deform, at the parts-per-million level under loads of a few x 10(exp 7) Pa. These stresses are easily exceeded when thin-walled shells (150 micron thick) are replicated. Our goal was to develop an alloy an order of magnitude stronger than this. We will present the results of our development program, showing the evolution of our plating baths through to our present 'glassy' nickel alloy that satisfies the goals above. For each we will show the electroforming characteristics of the bath and the PEL measurements for the resulting alloys. We estimate the ultimate limit on shell thickness and mass for x-ray mirrors produced in these baths.

Engelhaupt, D.↗
DOE OSTI2021

Global transpiration data from sap flow measurements: the SAPFLUXNET database

Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land–atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations. Here we introduce the first global compilation of whole-plant transpiration data from sap flow measurements (SAPFLUXNET, https://sapfluxnet.creaf.cat/, last access: 8 June 2021). We harmonized and quality-controlled individual datasets supplied by contributors worldwide in a semi-automatic data workflow implemented in the R programming language. Datasets include sub-daily time series of sap flow and hydrometeorological drivers for one or more growing seasons, as well as metadata on the stand characteristics, plant attributes, and technical details of the measurements. SAPFLUXNET contains 202 globally distributed datasets with sap flow time series for 2714 plants, mostly trees, of 174 species. SAPFLUXNET has a broad bioclimatic coverage, with woodland/shrubland and temperate forest biomes especially well represented (80 % of the datasets). The measurements cover a wide variety of stand structural characteristics and plant sizes. The datasets encompass the period between 1995 and 2018, with 50 % of the datasets being at least 3 years long. Accompanying radiation and vapour pressure deficit data are available for most of the datasets, while on-site soil water content is available for 56 % of the datasets. Many datasets contain data for species that make up 90 % or more of the total stand basal area, allowing the estimation of stand transpiration in diverse ecological settings. SAPFLUXNET adds to existing plant trait datasets, ecosystem flux networks, and remote sensing products to help increase our understanding of plant water use, plant responses to drought, and ecohydrological processes. SAPFLUXNET version 0.1.5 is freely available from the Zenodo repository (https://doi.org/10.5281/zenodo.3971689; Poyatos et al., 2020a). The “sapfluxnetr” R package – designed to access, visualize, and process SAPFLUXNET data – is available from CRAN.

58 GEOSCIENCES↗