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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

The source and distribution of Galactic positrons

The oriented scintillation spectrometer experiment (OSSE) observations of the Galactic plane and the Galactic center region were combined with observations acquired with other instruments in order to produce a map of the Galactic 511 keV annihilation radiation. Two mapping techniques were applied to the data: the maximum entropy method, and the basis pursuit inversion method. The resulting maps are qualitatively similar and show evidence for a central bulge and a weak galactic disk component. The weak disk is consistent with that expected from positrons produced by the decay of radioactive Al-26 in the interstellar medium. Both maps suggest an enhanced region of emission near l = -4 deg, b = 7 deg, with a flux of approximately 50 percent of that of the bulge. The existence of this emission appears significant, although the location is not well determined. The source of this enhanced emission is presently unknown.

Purcell, W. R.↗
NASA NTRS1997

Implications of the broad Al-26 1809 keV line observed by GRIS

The astrophysical implications of the large width of the 1809 keV gamma ray line from the decay of radioactive Al-26, recently observed with the gamma ray imaging spectrometer (GRIS), are discussed. While there may be no apparent single mechanism that can explain the observed broadening, high speed dust grains, extremely hot superbubbles and a large, low density gaseous halo were identified in the Galactic center region as the possible origins. The implications of these observations on the hot gas content in the interstellar medium are discussed.

Chen, Wan↗
NASA NTRS1997

Continuum Background in Space-Borne Gamma-Ray Detectors

The background measured with space-borne gamma-ray spectrometers (GRS) in the 100 keV-10 MeV energy region consists of both discrete lines and continuum. The discrete lines originate in the decay of radioactive species. The continuum originates from a number of different processes and can be an important factor in the detection, for example, of weak gamma-ray lines from a planetary surface. Measurements of the gamma-ray background have been made during the cruise portion of a number of planetary missions. The three missions described here are the Apollo 15 and 16 missions each of which carried a 7 cm x 7 cm NaI scintillation detector, the Mars Observer (MO) mission which used a 5.5 cm X 5.5 cm high-purity germanium (HPGe) detector, and the Near Earth Rendezvous Asteroid (NEAR) mission that has a 2.54 cm x 7.6 cm NaI detector. A comparison of the intensity and spectral shape of these background spectra can be useful to help understand how these backgrounds vary with spacecraft size, detector position, and detector size. The use of shields to reduce the background components on these three missions is a test of the effectiveness of different shield designs.

Larry G. Evans↗
NASA NTRS2004

MGGPOD: a Monte Carlo Suite for Modeling Instrumental Line and Continuum Backgrounds in Gamma-Ray Astronomy

Intense and complex instrumental backgrounds, against which the much smaller signals from celestial sources have to be discerned, are a notorious problem for low and intermediate energy gamma-ray astronomy (approximately 50 keV - 10 MeV). Therefore a detailed qualitative and quantitative understanding of instrumental line and continuum backgrounds is crucial for most stages of gamma-ray astronomy missions, ranging from the design and development of new instrumentation through performance prediction to data reduction. We have developed MGGPOD, a user-friendly suite of Monte Carlo codes built around the widely used GEANT (Version 3.21) package, to simulate ab initio the physical processes relevant for the production of instrumental backgrounds. These include the build-up and delayed decay of radioactive isotopes as well as the prompt de-excitation of excited nuclei, both of which give rise to a plethora of instrumental gamma-ray background lines in addition t o continuum backgrounds. The MGGPOD package and documentation are publicly available for download. We demonstrate the capabilities of the MGGPOD suite by modeling high resolution gamma-ray spectra recorded by the Transient Gamma-Ray Spectrometer (TGRS) on board Wind during 1995. The TGRS is a Ge spectrometer operating in the 40 keV to 8 MeV range. Due to its fine energy resolution, these spectra reveal the complex instrumental background in formidable detail, particularly the many prompt and delayed gamma-ray lines. We evaluate the successes and failures of the MGGPOD package in reproducing TGRS data, and provide identifications for the numerous instrumental lines.

Weidenspointner, G.↗
NASA NTRS2008

Radioisotope Power: A Key Technology for Deep Space Exploration

A Radioisotope Power System (RPS) generates power by converting the heat released from the nuclear decay of radioactive isotopes, such as Plutonium-238 (Pu-238), into electricity. First used in space by the U.S. in 1961, these devices have enabled some of the most challenging and exciting space missions in history, including the Pioneer and Voyager probes to the outer solar system; the Apollo lunar surface experiments; the Viking landers; the Ulysses polar orbital mission about the Sun; the Galileo mission to Jupiter; the Cassini mission orbiting Saturn; and the recently launched New Horizons mission to Pluto. Radioisotopes have also served as a versatile heat source for moderating equipment thermal environments on these and many other missions, including the Mars exploration rovers, Spirit and Opportunity. The key advantage of RPS is its ability to operate continuously, independent of orientation and distance relative to the Sun. Radioisotope systems are long-lived, rugged, compact, highly reliable, and relatively insensitive to radiation and other environmental effects. As such, they are ideally suited for missions involving long-lived, autonomous operations in the extreme conditions of space and other planetary bodies. This paper reviews the history of RPS for the U.S. space program. It also describes current development of a new Stirling cycle-based generator that will greatly expand the application of nuclear-powered missions in the future.

Schmidt, George↗
NASA NTRS2009

Radioisotope Power: A Key Technology for Deep Space Explorations

A Radioisotope Power System (RPS) generates power by converting the heat released from the nuclear decay of radioactive isotopes, such as Plutonium-238 (Pu-238), into electricity. First used in space by the U.S. in 1961, these devices have enabled some of the most challenging and exciting space missions in history, including the Pioneer and Voyager probes to the outer solar system; the Apollo lunar surface experiments; the Viking landers; the Ulysses polar orbital mission about the Sun; the Galileo mission to Jupiter; the Cassini mission orbiting Saturn; and the recently launched New Horizons mission to Pluto. Radioisotopes have also served as a versatile heat source for moderating equipment thermal environments on these and many other missions, including the Mars exploration rovers, Spirit and Opportunity. The key advantage of RPS is its ability to operate continuously, independent of orientation and distance relative to the Sun. Radioisotope systems are long-lived, rugged, compact, highly reliable, and relatively insensitive to radiation and other environmental effects. As such, they are ideally suited for missions involving long-lived, autonomous operations in the extreme conditions of space and other planetary bodies. This paper reviews the history of RPS for the U.S. space program. It also describes current development of a new Stirling cycle-based generator that will greatly expand the application of nuclear-powered missions in the future.

Schmidt, George R.↗
NASA NTRS2009

NASA Radioisotope Power System Program - Technology and Flight Systems

NASA sometimes conducts robotic science missions to solar system destinations for which the most appropriate power source is derived from thermal-to-electrical energy conversion of nuclear decay of radioactive isotopes. Typically the use of a radioisotope power system (RPS) has been limited to medium and large-scale missions, with 26 U,S, missions having used radioisotope power since 1961. A research portfolio of ten selected technologies selected in 2003 has progressed to a point of maturity, such that one particular technology may he considered for future mission use: the Advanced Stirling Converter. The Advanced Stirling Radioisotope Generator is a new power system in development based on this Stirling cycle dynamic power conversion technology. This system may be made available for smaller, Discovery-class NASA science missions. To assess possible uses of this new capability, NASA solicited and funded nine study teams to investigate unique opportunities for exploration of potential destinations for small Discovery-class missions. The influence of the results of these studies and the ongoing development of the Advanced Stirling Radioisotope Generator system are discussed in the context of an integrated Radioisotope Power System program. Discussion of other and future technology investments and program opportunities are provided.

Sutliff, Thomas J.↗
NASA NTRS2008

Thermal Expansion Studies of Selected High Temperature Thermoelectric Materials

Radioisotope thermoelectric generators (RTGs) generate electrical power by converting the heat released from the nuclear decay of radioactive isotopes (typically plutonium-238) into electricity using a thermoelectric converter. RTGs have been successfully used to power a number of space missions and have demonstrated their reliability over an extended period of time (tens of years) and are compact, rugged, radiation resistant, scalable, and produce no noise, vibration or torque during operation. System conversion efficiency for state-of-practice RTGs is about 6% and specific power less than or equal to 5.1 W/kg. Higher specific power would result in more on-board power for the same RTG mass, or less RTG mass for the same on-board power. The Jet Propulsion Laboratory has been leading, under the advanced thermoelectric converter (ATEC) project, the development of new high-temperature thermoelectric materials and components for integration into advanced, more efficient RTGs. Thermoelectric materials investigated to date include skutterudites, the Yb14MnSb11 compound, and SiGe alloys. The development of long-lived thermoelectric couples based on some of these materials has been initiated and is assisted by a thermo-mechanical stress analysis to ensure that all stresses under both fabrication and operation conditions will be within yield limits for those materials. Several physical parameters are needed as input to this analysis. Among those parameters, the coefficient of thermal expansion (CTE) is critically important. Thermal expansion coefficient measurements of several thermoelectric materials under consideration for ATEC are described in this paper. The stress response at the interfaces in material stacks subjected to changes in temperature is discussed, drawing on work from the literature and project-specific tools developed here. The degree of CTE mismatch and the associated effect on the formation of stress is highlighted.

silicon germanium↗
NASA NTRS2021

HARM3D+NUC: A New Method for Simulating the Post-merger Phase of Binary Neutron Star Mergers with GRMHD, Tabulated EOS, and Neutrino Leakage

The first binary neutron star merger has already been detected in gravitational waves. The signal was accompanied by an electromagnetic counterpart including a kilonova component powered by the decay of radioactive nuclei, as well as a short γ-ray burst. In order to understand the radioactively powered signal, it is necessary to simulate the outflows and their nucleosynthesis from the post-merger disk. Simulating the disk and predicting the composition of the outflows requires general relativistic magnetohydrodynamical (GRMHD) simulations that include a realistic, finite-temperature equation of state (EOS) and self-consistently calculating the impact of neutrinos. In this work, we detail the implementation of a finite-temperature EOS and the treatment of neutrinos in the GRMHD code HARM3D+NUC, based on HARM3D. We include formal tests of both the finite-temperature EOS and the neutrino-leakage scheme. We further test the code by showing that, given conditions similar to those of published remnant disks following neutron star mergers, it reproduces both recombination of free nucleons to a neutron-rich composition and excitation of a thermal wind.

Ariadna Murguia-Berthier↗
NASA NTRSDate not supplied

Phosphate (U-Th)/He Thermochronology of Apollo 14 Melt Breccia 14311

Our ability to confidently characterize the impact history of the inner solar system is limited by discrepancies in radiometric dates and age interpretations for lunar rocks, impact melts, and recovered meteorites. It is therefore important to explore different thermally sensitive radiometric systems to unravel the timing and extent of the long term impact flux. Low-temperature thermochronology of lunar samples has the potential to provide more complementary geochronological datasets and further test dynamical models related to the evolution of the inner solar system (e.g., [1]). (U-Th)/He dating is based on the production of 4He atoms by radioactive alpha decay of U and Th (and to a lesser extent, Sm) in a crystal and the thermally activated volumetric diffusion of those 4He nuclides. At high temperatures, the crystal is an open system from which 4He can escape; at lower temperatures, 4He may be retained. This retention temperature depends on factors such as crystal structure and volume fraction of radiation damage in the crystal (e.g., [2, 3]), but is significantly lower for phosphate minerals compared to the diffusion of the radiogenic daughter products in other widely used chronometric systems (e.g., ~75°C in terrestrial apatite (U-Th)/He vs. ~500°C in apatite U-Th-Pb vs. ~900°C in zircon U-Th-Pb chronometry). Phosphate (U-Th)/He dating has been used to decipher peak temperatures and cooling rates related to terrestrial impact events (e.g., [4]). Pairing a low-temperature thermochronometer with higher-temperature approaches (i.e., a combined 207Pb-206Pb and (U-Th)/He approach), can therefore resolve multiple impact ages within a given sample or even grain. However, despite its potential, phosphate (U-Th)/He dating has not been reported on any lunar samples. Here we present the first lunar phosphate (U-Th)/He thermochronology on an Apollo 14 impact melt-breccia.

C A Diaz↗
DOE OSTI2013

The Majorana Project

Working as part of a collaborative team, PNNL is bringing its signature capability in ultra-low-level detection to help search for a rare form of radioactive decay-never before detected-called "neutrinoless double beta decay" in germanium. If observed, it would demonstrate neutrinos are Majorana-type particles. This discovery would show neutrinos are unique among fundamental particles, having a property whereby the matter and anti-matter version of this particle are indistinguishable. Physicist John L. Orrell explains how they rely on the Shallow Underground Laboratory to conduct the research.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Why SRS Matters - Tritium

A video series presenting an overview of the Savannah River Site’s (SRS) mission and operations. Each episode features a specific area/operation and how it contributes to help make the world safer.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2015

Predicting Activation of Experiments Inside the Annular Core Research Reactor

The objective of this thesis is to create a program to quickly estimate the radioactivity and decay of experiments conducted inside of the Annular Core Research Reactor at Sandia National Laboratories and eliminate the need for users to write code. This is achieved by model the neutron fluxes in the reactor’s central cavity where experiments are conducted for 4 different neutron spectra using MCNP. The desired neutron spectrum, experiment material composition, and reactor power level are then input into CINDER2008 burnup code to obtain activation and decay information for every isotope generated. DREAD creates all of the files required for CINDER2008 through user selected inputs in a graphical user interface and executes the program for the user and displays the resulting estimation for dose rate at various distances. The DREAD program was validated by weighing and measuring various experiments in the different spectra and then collecting dose rate information after they were irradiated and comparing it to the dose rates that DREAD predicted. The program provides results with an average of 17% higher estimates than the actual values and takes seconds to execute.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Classifiers for Dissolution Events in Processing Facility Using Effluents Measurements

Inferring occurrences of dissolutions at a radiochemical processing facility using measurements from an independent monitoring system has potential for verifying operator declarations and compliance with nuclear technology use agreements. We consider the identification of such dissolution events using measurements of radioactive effluents collected at the facility’s off-gas stack. By using simple models for the source term based on radioactive decay-chains and sensor measurements of transported effluents, we formulate a simplified on/off classification problem. There are many available machine learning classification methods applicable to this problem, but they are subject to potential over-fitting. We mitigate this effect by fusing four promising but disparate classifiers: the ensemble of trees, support vector machines, naive Bayes, and k-nearest neighbors. Each classifier is trained to distinguish using effluents measurements between dissolutions of irradiated 237Np/238Pu and Cm/Cf targets from other (or no) radiochemical processing activities. We present Chow and ensemble of trees methods to fuse the classifier outputs to produce a single classification output, and thereby incorporate their diversity of design. We study the performance of these classifiers and fusers using measurements of87Kr,135Xe,138Xe, and138Cs isotopes,and present their training accuracy estimates using individual isotope measurements and all four isotopes taken together.

Rao, Nageswara S.↗
DOE OSTI2019

ORNL automates key process in plutonium-238 production

Oak Ridge National Laboratory scientists have automated part of the process of producing plutonium-238, which is used by NASA to fuel deep space exploration. Resolving this key bottleneck will help boost annual production of the radioisotope towards NASA’s goal of 1.5 kilograms of Pu-238 per year by 2025.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2023

PARTITIONING AND TRANSMUTATION OF USED NUCLEAR FUEL IN SUPPORT OF GEOLOGICAL WASTE DISPOSAL

Nuclear energy is a low-carbon technology that generates bulk baseload electricity and supports long-lasting eco-friendly sustainability goals. However, it still faces challenges, such as the securing and managing of long-lived nuclear actinides and fission products—most notably the used fuel, which is considered high-level waste (HLW). Direct geological waste disposal would be the most economical option for HLW but requires highly qualified sites whose geophysical behavior will remain stable for 10,000 years. Partitioning and transmutation (P&T) of used fuel reduces radioactivity and decay heat generation, enabling efficient geological waste disposal. P&T research and development, along with the prospects of P&T techniques such as wet/dry separation and accelerator-driven systems, were reviewed to identify critical needs that must be met to foster their successful implementation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

PARTITIONING AND TRANSMUTATION OF USED NUCLEAR FUEL IN SUPPORT OF GEOLOGICAL WASTE DISPOSAL

Nuclear energy is a low-carbon technology that generates bulk baseload electricity and supports long-lasting eco-friendly sustainability goals. However, it still faces challenges, such as the securing and managing of long-lived nuclear actinides and fission products—most notably the used fuel, which is considered high-level waste (HLW). Direct geological waste disposal would be the most economical option for HLW but requires highly qualified sites whose geophysical behavior will remain stable for 10,000 years. Partitioning and transmutation (P&T) of used fuel reduces radioactivity and decay heat generation, enabling efficient geological waste disposal. P&T research and development, along with the prospects of P&T techniques such as wet/dry separation and accelerator-driven systems, were reviewed to identify critical needs that must be met to foster their successful implementation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

An integrated equipment for massive segmentation and packaging of control Rod Guide Tubes - 15161

Over time, some utilities have decided to undergo safety upgrades that include replacement of some ageing components like control rod guide tubes (GT's). GT's are safety related components because they control the path of the control rods into and out of the core. These components are usually stored underwater in interim storage pools to decay their radioactivity. When the interim storage facility reaches saturation, treatment and final disposal of the retired Guide Tubes needs to be performed. Based on more than 30 years of experience and lessons learned in the development of segmentation and packaging technologies for nuclear components, Westinghouse has designed, commissioned and will operate a dedicated system for cutting and packaging retired GT's from 900 MW plants, currently stored in a EDF maintenance facility located in the south of France. The first main technical challenge was the waste volume optimization. Two separate waste streams had to be considered for coping with the highly irradiated portion of the GT's (lower part) and the very low level waste sections (upper part). The segmentation plan has been designed to minimize the waste volume of the highly irradiated waste and therefore develop a process which could be adapted to the container size specified by EDF. Metallic baskets have been designed to optimize the packaging and storage density in the containers. All cutting techniques previously used by Westinghouse in similar applications were assessed and underwater mechanical cutting with a band saw was selected as the preferred method. A turning stand positions the GT in front of the band saw. When the cut is completed, the remnant GT is inserted into the next turning stand for the next cut. Each cell of the turning stand positions the GT at the pre-defined cutting height. An integrated water filtration system is used to ensure good visibility during the cutting operations and to minimize water volume and limit the final liquid effluents. The whole process of GT insertion, cutting, packaging and waste conditioning is carried out in a hot cell and controlled remotely. The operator can therefore follow the packaging plan accurately and safely by using a four axis pick and place unit, while keeping personal radiation exposure low. This innovative process allows cutting and packaging large quantities of GT's in a safe and efficient manner. The pilot project covers the segmentation of 93 GT's but it can be further used for cutting larger quantities of retired GT's resulting from the upcoming GT replacement campaigns. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗