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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Risk of Skin Cancer from Space Radiation

We review the methods for estimating the probability of increased incidence of skin cancers from space radiation exposure, and describe some of the individual factors that may contribute to risk projection models, including skin pigment, and synergistic effects of combined ionizing and UV exposure. The steep dose gradients from trapped electrons, protons, and heavy ions radiation during EVA and limitations in EVA dosimetry are important factors for projecting skin cancer risk of astronauts. We estimate that the probability of increased skin cancer risk varies more than 10-fold for individual astronauts and that the risk of skin cancer could exceed 1 % for future lunar base operations for astronauts with light skin color and hair. Limitations in physical dosimetry in estimating the distribution of dose at the skin suggest that new biodosimetry methods be developed for responding to accidental overexposure of the skin during future space missions.

Cucinotta, Francis A.↗
NASA NTRS2002

Shuttle radiation dose measurements in the International Space Station orbits

The International Space Station (ISS) is now a reality with the start of a permanent human presence on board. Radiation presents a serious risk to the health and safety of the astronauts, and there is a clear requirement for estimating their exposures prior to and after flights. Predictions of the dose rate at times other than solar minimum or solar maximum have not been possible, because there has been no method to calculate the trapped-particle spectrum at intermediate times. Over the last few years, a tissue-equivalent proportional counter (TEPC) has been flown at a fixed mid-deck location on board the Space Shuttle in 51.65 degrees inclination flights. These flights have provided data that cover the expected changes in the dose rates due to changes in altitude and changes in solar activity from the solar minimum to the solar maximum of the current 23rd solar cycle. Based on these data, a simple function of the solar deceleration potential has been derived that can be used to predict the galactic cosmic radiation (GCR) dose rates to within +/-10%. For altitudes to be covered by the ISS, the dose rate due to the trapped particles is found to be a power-law function, rho(-2/3), of the atmospheric density, rho. This relationship can be used to predict trapped dose rates inside these spacecraft to +/-10% throughout the solar cycle. Thus, given the shielding distribution for a location inside the Space Shuttle or inside an ISS module, this approach can be used to predict the combined GCR + trapped dose rate to better than +/-15% for quiet solar conditions.

NASA Discipline Radiation Health↗
DOE OSTI2021

Effect of the sample work function on alkali metal dosing induced electronic structure change

Alkali metal dosing (AMD) has been widely used as a way to control doping without chemical substitution. This technique, in combination with angle resolved photoemission spectroscopy (ARPES), often provides an opportunity to observe unexpected phenomena. However, the amount of transferred charge and the corresponding change in the electronic structure vary significantly depending on the material. Here, we report study on the correlation between the sample work function and alkali metal induced electronic structure change for three iron-based superconductors: FeSe, Ba(Fe 0.94 Co 0.06 ) 2 As 2 and NaFeAs which share a similar Fermi surface topology. Electronic structure change upon monolayer of alkali metal dosing and the sample work function were measured by ARPES. In this work, our results show that the degree of electronic structure change is proportional to the difference between the work function of the sample and Mulliken's absolute electronegativity of the dosed alkali metal. This finding provides a possible way to estimate the AMD induced electronic structure change.

36 MATERIALS SCIENCE↗
NASA NTRS1997

Biodosimetry results from space flight Mir-18

Astronauts are classified as radiation workers due to the presence of ionizing radiation in space. For the assessment of health risks, physical dosimetry has been indispensable. However, the change of the location of dosimeters on the crew members, the variation in dose rate with location inside the spacecraft and the unknown biological effects of microgravity can introduce significant uncertainties in estimating exposure. To circumvent such uncertainty, a study on the cytogenetic effects of space radiation in human lymphocytes was proposed and conducted for Mir-18, a 115-day mission. This study used fluorescence in situ hybridization (FISH) with whole-chromosome painting probes to score chromosomal exchanges and the Giemsa staining method to determine the frequency of dicentrics. The growth kinetics of cells and sister chromatid exchanges (SCEs) were examined to ensure that chromosomal aberrations were scored in the first mitosis and were induced primarily by space radiation. Our results showed that the frequency of chromosomal aberrations increased significantly in postflight samples compared to samples drawn prior to flight, and that the frequency of SCEs was similar for both pre- and postflight samples. Based on a dose-response curve for preflight samples exposed to gamma rays, the absorbed dose received by crew members during the mission was estimated to be about 14.75 cSv. Because the absorbed dose measured by physical dosimeters is 5.2 cGy for the entire mission, the RBE is about 2.8.

NASA Discipline Radiation Health↗
NASA NTRS1998

Effect of track structure and radioprotectors on the induction of oncogenic transformation in murine fibroblasts by heavy ions

The oncogenic potential of high-energy 56Fe particles (1 GeV/nucleon) accelerated with the Alternating Gradient Synchrotron at the Brookhaven National Laboratory was examined utilizing the mouse C3H 10T1/2 cell model. The dose-averaged LET for high-energy 56Fe is estimated to be 143 keV/micrometer with the exposure conditions used in this study. For 56Fe ions, the maximum relative biological effectiveness (RBEmax) values for cell survival and oncogenic transformation were 7.71 and 16.5 respectively. Compared to 150 keV/micrometer 4He nuclei, high-energy 56Fe nuclei were significantly less effective in cell killing and oncogenic induction. The prostaglandin E1 analog misoprostol, an effective oncoprotector of C3H 10T1/2 cells exposed to X rays, was evaluated for its potential as a radioprotector of oncogenic transformation with high-energy 56Fe. Exposure of cells to misoprostol did not alter 56Fe cytotoxicity or the rate of 56Fe-induced oncogenic transformation.

NASA Discipline Radiation Health↗
DOE OSTI2022

Cavity evolution and void swelling in dual ion irradiated tempered martensitic steels

Microstructural evolutions in two variants of the F82H 8 wt%Cr tempered martensitic steel under dual (He + plus Fe 3+ ) ion irradiations at 500 °C have been characterized by transmission electron microscopy. Emphasis is on understanding the combined effects of displacements per atom (dpa) and the helium/dpa ratio (He/dpa) on cavity evolution and void swelling (f v ). The dual ion database includes 231 alloy-dpa-He/dpa conditions for irradiations up to ~ 82 dpa and 3700 appm helium. Here, we hypothesize that the large “scatter” observed in the f v data is primarily due to local microstructural variations, especially those that shield regions at shallower depths from the effects of injected interstitial atoms, which would otherwise reduce f v . More generally, our hypothesis is that the highest f v data, at a specified dpa and He/dpa, provides the most appropriate estimate of swelling for fusion neutron irradiation conditions. The dose dependence of f v can be described by an incubation dpa i , marking the onset of significant void growth, and a post-incubation swelling rate, f v ’ = Δf v /Δdpa. Both dpa i and f v ’ decrease with increasing He/dpa. The f v ’ data are quantitatively consistent with a simple model for defect partitioning between evolving bubble, void, and dislocation sinks strengths and biases. Most notably, the model correctly predicts both the incubation dpa i , and the subsequent f v ’, in spite of the fact that they reflect somewhat different physics. Our analysis also suggests that defect recombination is modest at 500 °C. Along with other considerations, this supports the hypothesis that, even at high dpa rates, dual ion irradiations can be used to reasonably emulate void nucleation and growth for a range of fusion-relevant neutron irradiation service conditions. A companion paper incorporates the results of this study in a reduced-order, data-driven void swelling model.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Determining reference standard strength for neutron-irradiated reduced activation ferritic/martensitic steel F82H by Bayesian method

The deterministic approach widely adopted in the design of structural components relies on systematically defined design limits using empirically determined safety factors. However, this approach is not always appropriate because structures are subjected to a variety of loads in the practical environment, which may result in excessively conservative design limits. In recent years, a more rigorous probabilistic approach that incorporates material strength distributions has become an important solution. In the probabilistic approach, the probability density functions of material strength properties underpin the design criteria. Here, the objective of this study is to identify the density distribution functions that best describe tensile properties of irradiated F82H to define a reference strength for DEMO design. Due to the limited number of existing data, this study specifically employs a Bayesian prediction method based on Monte Carlo simulations to determine a material reference value with statistical reliability and to investigate its effectiveness. For example, the dependence of tensile properties of 300 °C irradiated materials on irradiation damage and the range predicted by 95% Bayesian estimation was evaluated. As a statistical model for the dose dependence of statistical parameters, the normal distribution exhibited a better fit for 0.2% proof strength and tensile strength, whereas the distribution of total elongation data gave comparable reference values for both the normal and Weibull distribution models. Both models gave comparable criteria for the distribution of total elongation data. The Weibull model also gave better results for uniform elongation. The function best describing the model was a logarithmic law for both 0.2% proof strength and tensile strength, while a power law for both total and uniform elongation, which allowed for more comprehensive data prediction of irradiation data with statistical accuracy for DEMO reactor design.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Lithium indium diselenide — An advanced material for neutron detection

Here, this paper describes the synthesis, crystal growth, detector fabrication, radiation hardening studies, MCNP modeling, and characterization of lithium indium diselenide or LiInSe 2 . This newly-developed room temperature thermal neutron detector has semiconducting and scintillating properties and it is suitable for neutron detection application. LiInSe 2 was synthesized starting from elemental Li, In, Se in two steps due to high reactivity of Li. A single crystal of LiInSe 2 was grown using the Vertical Bridgman method. The room temperature band gap was found to be 2.8 eV using optical absorption measurements. Bulk resistivity was measured at ∼5 × 10 11 Ωcm. Photoconductivity measurements of LiInSe 2 wafers identified a peak in the photocurrent around 445 nm. Nuclear radiation detectors were fabricated from single crystal wafer and the responses to alpha particles at various biases were measured. The mobility-lifetime product was estimated. Gamma irradiation studies were performed with calculated absorbed doses ranging from 0.2126 to 21,262 Gy. The characterization of the two wafers for their scintillator performance was conducted after each irradiation. The gamma irradiation produced a reduction of the light yield that translated to a lower channel number for the centroid of alpha detection spectra. It also showed a considerable reduction of the decay time after the first irradiation. These are the first studies on gamma radiation hardening with this material.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Calculation for T Plant Estimated PTE with Receipt of K Basin Sludge and Filter Media

The purpose of this environmental calculation is to: (1) show compliance with the WAC 173-400-110, New Source Review (NSR) for Sources and Portable Sources requirements and (2) provide the methodology, assumptions and calculation used to estimate the potential to emit (PTE) and Total Effective Dose Equivalent to the Maximally Exposed Individual (TEDE to the MEI) radionuclide airborne emissions associated with the receipt of K Basin sludge and filter media for storage at T Plant.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

In Silico Prediction of the Toxicity of Nitroaromatic Compounds: Application of Ensemble Learning QSAR Approach

In this work, a dataset of more than 200 nitroaromatic compounds is used to develop Quantitative Structure–Activity Relationship (QSAR) models for the estimation of in vivo toxicity based on 50% lethal dose to rats (LD 50 ). An initial set of 4885 molecular descriptors was generated and applied to build Support Vector Regression (SVR) models. The best two SVR models, SVR_A and SVR_B, were selected to build an Ensemble Model by means of Multiple Linear Regression (MLR). The obtained Ensemble Model showed improved performance over the base SVR models in the training set (R 2 = 0.88), validation set (R 2 = 0.95), and true external test set (R 2 = 0.92). The models were also internally validated by 5-fold cross-validation and Y-scrambling experiments, showing that the models have high levels of goodness-of-fit, robustness and predictivity. The contribution of descriptors to the toxicity in the models was assessed using the Accumulated Local Effect (ALE) technique. The proposed approach provides an important tool to assess toxicity of nitroaromatic compounds, based on the ensemble QSAR model and the structural relationship to toxicity by analyzed contribution of the involved descriptors.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1988

Radiation safety in commercial air traffic - A need for further study

The problem of radiation exposure of crewmembers in high altitude supersonic commercial aircraft is addressed. As a result of recent changes in the quality factors for radiological protection, it is found that worst case estimates of radiation exposure are now well above the exposure limits of the general population, and a reassessment of radiation impact on commercial aviation is needed, if the proposed quality factors are adopted. Calculations are presented from a study on neutron dosage equivalent rates. It is shown that a crew flying at altitudes near 13 km (43,000 ft) for 40 hr/mo would receive exposure levels of 47-75 Sv/yr, and it is suggested that such crewmembers be considered as radiation workers, rather than general population members. However, since present exposure estimates need to be improved, and the maximum permissible dose limits are currently under revision, the final exposure limits are, as yet, unclear, suggesting the need for further study to clarify the work status of commercial aircrews.

Wilson, John W.↗
NASA NTRS1989

Approximate angular distribution and spectra for geomagnetically trapped protons in low-earth orbit

The highly anisotropic nature of the radiation in the low-earth orbit has been ignored for most spacecraft shielding calculations made to date because the standard environmental models describe the omnidirectional flux only, because the varying attitude of the spacecraft in the environment is assumed to average out the effect and because of the added complexity of the calculation. The Space Station is planned to be stabilized with respect to the velocity vector and local vertical. Thus it will pass through the South Atlantic Anomaly where most of the radiation flux is encountered in much the same attitude on each pass. Any calculation including a complex shielding geometry should thus consider the angular distributuon of the incident radiation. An approximate trapped proton angular distribution is presented which includes both the 'pan caked' distribution relative to the magnetic field direction and the east-west effect which is energy dependent. This distribution is then used with a planar shielding geometry to obtain an estimate of the effect of the anisotropy on radiation dose rates in spacecraft.

Watts, J. W.↗
NASA NTRS2001

Radiation breakage of DNA: a model based on random-walk chromatin structure

Monte Carlo computer software, called DNAbreak, has recently been developed to analyze observed non-random clustering of DNA double strand breaks in chromatin after exposure to densely ionizing radiation. The software models coarse-grained configurations of chromatin and radiation tracks, small-scale details being suppressed in order to obtain statistical results for larger scales, up to the size of a whole chromosome. We here give an analytic counterpart of the numerical model, useful for benchmarks, for elucidating the numerical results, for analyzing the assumptions of a more general but less mechanistic "randomly-located-clusters" formalism, and, potentially, for speeding up the calculations. The equations characterize multi-track DNA fragment-size distributions in terms of one-track action; an important step in extrapolating high-dose laboratory results to the much lower doses of main interest in environmental or occupational risk estimation. The approach can utilize the experimental information on DNA fragment-size distributions to draw inferences about large-scale chromatin geometry during cell-cycle interphase.

Chromatin/radiation effects↗
NASA NTRS1972

Electron and proton flux models for Jupiter's radiation belts

Estimates of the energetic particle distribution in Jupiter's radiation belts are presented and are compared with previous estimates. Mathematical expressions are developed for the equatorial electron and proton fluxes, shielded electron and proton dose rates, and radiation lifetimes of electronic circuits. It is calculated that a 1 g/sq cm aluminum shield will screen out all protons of energy less than 27.5 MeV, and a 2 g/sq cm shield will screen out protons less than 40.6 MeV. The radiation lifetimes are based on a maximum permissible dose value of 10 million rads, a value 1/2 to 1/3 of the flux at which electronic circuits begin to fail. Estimated increases in lifetimes by using a 3 x 50 orbit instead of a 3 x 3 orbit, and going from 1 to 2 g/sq cm are given.

Klopp, D. A.↗
NASA NTRS1990

Ecdysteroids affect in vivo protein metabolism of the flight muscle of the tobacco hornworm (Manduca sexta)

Ecdysteroid growth promotion of the dorsolongitudinal flight muscle of Manduca sexta was studied by measuring in vivo protein metabolism using both "flooding-dose" and "non-carrier" techniques. These procedures differ in that the former method includes injection of non-labelled phenylalanine (30 micromoles/insect) together with the [3H]amino acid. Injected radioactivity plateaued in the haemolymph within 7 min. With the flooding-dose method, haemolymph and intramuscular specific radioactivities were similar between 15 min and 2 h. Incorporation of [3H]phenylalanine into muscle protein was linear with either method between 30 and 120 min. Fractional rates (%/12 h) of synthesis with the flooding-dose technique were best measured after 1 h because of the initial delay in radioactivity equilibration. Estimation of body phenylalanine turnover with the non-carrier method showed 24-53%/h which was negligible with the flooding-dose method. Since the two methods yielded similar rates of protein synthesis, the large injection of non-labelled amino acid did not alter the rate of synthesis. Because the flooding-dose technique requires only a single time point measurement, it is the preferred method. The decline and eventual cessation of flight-muscle growth was mostly a consequence of declining protein synthesis though degradation increased between 76-86 h before eclosion and was relatively rapid. This decline in muscle growth could be prevented by treating pupae with 20-hydroxyecdysone (10 micrograms/insect). Protein accretion was promoted by a decline of up to 80% in protein breakdown, which was offset in part by a concurrent though much smaller decrease in protein synthesis. Therefore, ecdysteroids may increase flight-muscle growth by inhibiting proteolysis.

NASA Discipline Developmental Biology↗
NASA NTRS1994

Radiation dosimetry measurements during U.S. Space Shuttle missions with the RME-III

Time-resolved radiation dosimetry measurements inside the crew compartment have been made during recent Shuttle missions with the U.S. Air Force Radiation Monitoring Equipment-III (RME-III), a portable battery-powered four-channel tissue equivalent proportional counter. Results from the first six missions are presented and discussed. Half of the missions had orbital inclinations of 28.5 degrees with the remainder at inclinations of 57 degrees or greater; altitudes ranged from 300 to 600 km. The determined dose equivalent rates ranged from 70 to 5300 microSv/day. The RME-III measurements are in good agreement with other dosimetry measurements made aboard the vehicles. Measurements indicate that medium- and high-LET particles contribute less than 2% of the particle fluence for all missions, but up to 50% of the dose equivalent, depending on the spacecraft's altitude and orbital inclination. Isocontours of fluence, dose and dose equivalent rate have been developed from measurements made during the STS-28 mission. The drift rate of the South Atlantic Anomaly is estimated to be 0.49 degrees W/yr and 0.12 degrees N/yr. The calculated trapped proton and GCR dose for the STS-28 mission was significantly lower than the measured values.

STS-28 Shuttle Project↗
DOE OSTI2022

Heavy-Ion-Induced Lung Tumors: Dose- & LET-Dependence

There is a limited published literature reporting dose-dependent data for in vivo tumorigenesis prevalence in different organs of various rodent models after exposure to low, single doses of charged particle beams. The goal of this study is to reduce uncertainties in estimating particle-radiation-induced risk of lung tumorigenesis for manned travel into deep space by improving our understanding of the high-LET-dependent dose-response from exposure to individual ion beams after low particle doses (0.03 - 0.80 Gy). Female CB6F1 mice were irradiated with low single doses of either oxygen, silicon, titanium, or iron ions at various energies to cover a range of dose-averaged LET values from 0.2 - 193 keV/µm, using 137Cs γ-rays as the reference radiation. Sham-treated controls were included in each individual experiment totally 398 animals across the 5 studies reported. Based on power calculations, between 40 - 156 mice were included in each of the treatment groups. Tumor prevalence at 16 months after radiation exposure was determined and compared to the age-matched, sham-treated animals. Results indicate that lung tumor prevalence is non-linear as a function of dose with suggestions of threshold doses depending on the LET of the beams. Histopathological evaluations of the tumors showed that the majority of tumors were benign bronchioloalveolar adenomas with occasional carcinomas or lymphosarcomas which may have resulted from metastases from other sites.

60 APPLIED LIFE SCIENCES↗
NASA NTRSDate not supplied

Analytical Calculation of the Energy Deposition Spectrum and Average Dose to A Spherical Target By Ion Tracks at All Impact Parameters

Microdosimetry is used to estimate quality factors for risk assessment in radiation protection [1] and to quantify relative biological effectiveness (RBE) for treatment planning of hadron radiation therapy [2]. Radiation physics has shown that energetic ions deposit energy in a complex manner: the track structure. The Local Effect Model (LEM) [3] is often used as an approximation to describe this complex track structure. We have previously calculated an analytical expression for the dose to a spherical target fully located in the penumbra of an ion track using the LEM [4]. In this work, the calculation has been extended to all impact parameters. Furthermore, using these analytical expressions, it was possible to obtain the theoretical energy deposition spectra to a sphere irradiated uniformly.

I Plante↗