Search NASA⌕ Search

SEARCH · Search NASA

Results for “Radiation Standard”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records

Evaluation of standard radiation atmosphere aerosol models for a coastal environment

Calculations are compared with data from an experiment to evaluate the utility of standard radiation atmosphere (SRA) models for defining aerosol properties in atmospheric radiation computations. Initial calculations with only SRA aerosols in a four-layer atmospheric column simulation allowed a sensitivity study and the detection of spectral trends in optical depth, which differed from measurements. Subsequently, a more detailed analysis provided a revision in the stratospheric layer, which brought calculations in line with both optical depth and skylight radiance data. The simulation procedure allows determination of which atmospheric layers influence both downwelling and upwelling radiation spectra.

Whitlock, C. H.↗

Phase function, backscatter, extinction, and absorption for standard radiation atmosphere and El Chichon aerosol models at visible and near-infrared wavelengths

Tabular values of phase function, Legendre polynominal coefficients, 180 deg backscatter, and extinction cross section are given for eight wavelengths in the atmospheric windows between 0.4 and 2.2 microns. Also included are single scattering albedo, asymmetry factor, and refractive indices. These values are based on Mie theory calculations for the standard rediation atmospheres (continental, maritime, urban, unperturbed stratospheric, volcanic, upper atmospheric, soot, oceanic, dust, and water-soluble) assest measured volcanic aerosols at several time intervals following the El Chichon eruption. Comparisons of extinction to 180 deg backscatter for different aerosol models are presented and related to lidar data.

Whitlock, C. H.↗

Standardized Radiation Shield Design Methods: 2005 HZETRN

Research committed by the Langley Research Center through 1995 resulting in the HZETRN code provides the current basis for shield design methods according to NASA STD-3000 (2005). With this new prominence, the database, basic numerical procedures, and algorithms are being re-examined with new methods of verification and validation being implemented to capture a well defined algorithm for engineering design processes to be used in this early development phase of the Bush initiative. This process provides the methodology to transform the 1995 HZETRN research code into the 2005 HZETRN engineering code to be available for these early design processes. In this paper, we will review the basic derivations including new corrections to the codes to insure improved numerical stability and provide benchmarks for code verification.

Wilson, John W.↗

Provisional standards of radiation safety during flights

Radiation effects during space flights are discussed in the context of the sources and dangers of such radiation and the radiobiological prerequisites for establishing safe levels of radiation dosage. Standard safe levels of radiation during space flight are established.

Source record↗

JSC Avionics Ionizing Radiation Effects Standard (AIRES)

This document, the JSC Engineering Directorate Avionics Ionizing Radiation Effects Standard (AIRES), provides design, test, and analysis requirements to ensure electronic hardware meets functional, performance and reliability requirements in the mission ionizing radiation environment. This suite of activities is referred to as Radiation Hardening Assurance (RHA) and is an integral part of the hardware design process.

Ionizing Radiation↗

Provisional standards of radiation safety of flight personnel and passengers in air transport of the civil aviation

Provisional standards for radiation affecting passenger aircraft are considered. Agencies responsible for seeing that the regulations are enforced are designated while radiation sources and types of radiation are defined. Standard levels of permissible radiation are given and conditions for radiation safety are discussed. Dosimetric equipment on board aircraft is delineated and regulation effective dates are given.

Source record↗

Reevaluation of Radiation-Protection Standards for Workers and the Public Based on Current Scientific Evidence

President Trump’s recent executive orders to “Usher in a Nuclear Renaissance,” coupled with the global pledge to triple nuclear energy capacity by 2050, underscore nuclear energy’s importance to national security and economic prosperity. This renewed interest has prompted efforts to spur nuclear-energy deployment, including assessing factors impeding it. One issue that has previously been identified as adding to the cost of nuclear energy is excessively conservative requirements, including those related to radiation protection. This technical review, therefore, examines current radiation-protection standards that were established decades ago when more limited data were available and nuclear-energy expansion was not a national priority. The review focuses on scientific evidence regarding the health effects of ionizing radiation at annual doses of 10,000 mrem or less. The review evaluates epidemiological studies, radiobiological research, and positions of relevant professional organizations to assess whether such doses result in discernable or observable increases in negative health outcomes. The review also surveys the literature related to economic and practical implications of current radiation-protection standards and practices. Based on this assessment, we propose maintaining an annual occupational whole-body dose limit of 5,000 mrem/yr and eliminating all “as low as reasonably achievable” requirements and limits below this threshold. This change could potentially reduce radiation-protection costs by millions of dollars annually for each reactor, as well as decrease the overall costs and correct misconceptions about the risks associated with all nuclear technologies. The evidence further supports future consideration of a 10,000 mrem/yr limit that would maintain appropriate safety margins while further reducing protection costs. Similarly, given the data and that the average annual radiation dose per person in the U.S. is 620 mrem, we believe the public dose limits of 100 mrem/yr are unnecessarily restrictive; increasing to 500 mrem/yr would maintain substantial safety margins—a factor of 10 below the occupational limit—while reducing regulatory burdens and associated bureaucracy. While we acknowledge ongoing scientific debate and encourage continued research on the health effects of ionizing radiation, our review indicates current frameworks are overly conservative. These overly stringent limits not only impose unnecessary economic burdens without corresponding health benefits but also divert safety focus and resources from more important considerations. Although this study was motivated by nuclear-power considerations, reforms to radiation-protection requirements have significant positive implications for other areas, such as nuclear medical applications, environmental remediation, nuclear-waste management and disposal, and industrial applications of nuclear technologies.

61 RADIATION PROTECTION AND DOSIMETRY↗

Standards for Radiation Effects Testing: Ensuring Scientific Rigor in the Face of Budget Realities and Modern Device Challenges

An overview is presented of the space radiation environment and its effects on electrical, electronic, and electromechanical parts. Relevant test standards and guidelines are listed. Test standards and guidelines are necessary to ensure best practices, minimize and bound systematic and random errors, and to ensure comparable results from different testers and vendors. Test standards are by their nature static but exist in a dynamic environment of advancing technology and radiation effects research. New technologies, failure mechanisms, and advancement in our understanding of known failure mechanisms drive the revision or development of test standards. Changes to standards must be weighed against their impact on cost and existing part qualifications. There must be consensus on new best practices. The complexity of some new technologies exceeds the scope of existing test standards and may require development of a guideline specific to the technology. Examples are given to illuminate the value and limitations of key radiation test standards as well as the challenges in keeping these standards up to date.

Test Standard↗

NASA Radiation Operations Sources, Models, and Standards

Space radiation is one of the major challenges of spaceflight. Astronauts spending time in low Earth orbit, the lunar surface, deep space, and elsewhere will all be exposed to multiple space radiation sources. These sources include trapped radiation in Earth’s upper atmosphere, solar energetic particles, and the omnipresent galactic cosmic radiation, as well as non-ionizing radiation from inside and outside a vehicle or habitat. The Space Radiation Analysis Group (SRAG) at Johnson Space Center is responsible for ensuring astronauts are protected from short- and long-term risks of radiation exposure. This talk details the radiation operational standards employed by NASA.

space radiation↗

A standard for ultraviolet radiation.

Photoemission diode standards for accurately measuring monochromatic ultraviolet light intensity (3000 A-1100 A) are described that are also blind to visible light. The standard uses an opaque photocathode of Cs2Te and is unique because of its combination of thinness (19 mm), high sensitivity, time stability, and uniformity of response. Design criteria, construction methods, and difficulties overcome in obtaining a stable, uniform, high yield photocathode responses are discussed. Cs2Te is discussed in terms of a model for high yield photoemitters.

Fisher, G. B.↗

Standardizing GPU Radiation Test Approaches

While some Graphical Processing Units (GPUs) are discrete components (i.e.GTX1050), others take the form of an IP block or embedded engine within a System on Chip (SoC) device such as the Qualcomm Snapdragon"TM" 820 which contains a Qualcomm Adreno"TM" 530 GPU. Within this device are various functional blocks which can be exercised with software payloads. NVidia's Jetson"TM" TX1 SoC is provided on a System on Module (SOM). Within it are Central Processing Unit (CPU) cores and an nVidia GPU which can be accessed similarly to a discrete GPU coprocessor. While the packaging is different, each one of these GPUs needs to be tested using the same standardized code.

Single Event Effects (SEE)↗

Ultraviolet photometry from the Orbiting Astronomical Observatory. XXI - Absolute energy distribution of stars in the ultraviolet

The absolute energy distribution in the ultraviolet is given for the stars alpha Vir, eta UMa, and alpha Leo. The calibration is based on absolute heterochromatic photometry between 2920 and 1370 A carried out with an Aerobee sounding rocket. The fundamental radiation standard is the synchrotron radiation from 240-MeV electrons in a certain synchrotron storage ring. On the basis of the sounding-rocket calibration, the preliminary OAO-2 spectrometer calibration has been revised; the fluxes for the three program stars are tabulated in energy per second per square centimeter per unit wavelength interval.

Bless, R. C.↗

Astronomical studies of the major planets, natural satellites and asteroids using the 2.24 m telescope

Directional features in the Jovian sodium torus, high quality CCD images of the major planets, methane bands in the spectrum of Triton, the central wavelength of the SO2 absorption band on Io, a component on the icy surfaces of the satellites of Uranus, fluctuation of Io's volcanic radiation, standard stars, and thermal radiation from the four brightest satellites of Uranus are discussed.

Jefferies, J. T.↗