Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Isotope Program”

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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Advancements in Multiphysics Microdepletion Analysis of an eVinci TM -like Microreactor Leveraging OpenMC-CRAB Workflow

Nuclear microreactors (MRs) are a class of nuclear reactor technology, characterized by reduced dimensions, modular design, and reduced power output in contrast to conventional Light Water Reactors (LWRs). MRs are proposed for supplying electricity and eventual process heat to remote locations, such as military installations and disaster-affected areas. Current research work sponsored by the US Department of Energy Microreactor Program (MRP) is devoted to the development of novel modeling and simulation tools to better support MR vendors and regulatory bodies. Notably, the NRC is projected to utilize the CRAB multiphysics software driver for executing both design and beyond-design-basis accident analyses. Furthermore, the NRC has been utilizing the MELCOR code to calculate mechanistic source terms during accidents. Since MELCOR relies on isotopic inventory and reactor temperature/power profiles under accident conditions, which theoretically can be derived from CRAB, the goal is to establish a comprehensive CRAB-MELCOR computational framework. Past work was focused on testing and demonstrating CRAB's capability to generate results that can be used to inform mechanistic source term calculations in MELCOR. In particular, a computational workflow leveraging OpenMC-generated microscopic cross sections and CRAB was first applied to perform multiphysics microscopic depletion calculation followed by an accident scenario for a stylized microreactor problem. In fiscal year 2024, the research work has been focused on applying the OpenMC-CRAB workflow, which was first tested in fiscal year 2023, to a realistic 3D heat-pipe cooled MR problem representative of the eVinci TM design. The latter computational problem was developed with inputs from WEC to conserve selected neutronic and thermal characteristics of the eVinci TM design without releasing proprietary data. The results of this simulation, encompassing isotopic inventory, power density distribution, and kinetic parameters, will inform both MELCOR and the WEC-developed FATE code for mechanistic source terms calculations. The results from the two codes will then be compared for code verification purposes. This report contains the design characteristics of the realist heat pipe cooled microreactor developed as a use-case for the verification exercise, and the current results for the multiphysics microscopic depletion performed with the OpenMC-CRAB workflow. The results include eigenvalue as a function of time, power distribution at EOL, in addition to nuclides inventory's time evolution and spatial distribution. Finally, we report improvements to the workflow efficiency achieved through a collaboration with the NEAMS programs. Through this collaborative effort, we were able to strongly decrease the computational time for the multiphysics microdepletion calculation (i.e., from 17.4 hours to 5.7 hours on 280 processors) in addition to simplifying the interface to generate isotopics spatial distribution utilizable by FATE and MELCOR. Future work, including the improvement of the current microscopic cross-sections' library and the simulation of an accident scenario at EOL, is also discussed.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2017

Heat deposition analysis for the High Flux Isotope Reactor’s HEU and LEU core models

The High Flux Isotope Reactor at Oak Ridge National Laboratory is an 85 MW th pressurized light-water-cooled and -moderated flux-trap type research reactor. The reactor is used to conduct numerous experiments, advancing various scientific and engineering disciplines. As part of an ongoing program sponsored by the US Department of Energy National Nuclear Security Administration Office of Material Management and Minimization, studies are being performed to assess the feasibility of converting the reactor’s highly enriched uranium fuel to low-enriched uranium fuel. To support this conversion project, reference models with representative experiment target loading and explicit fuel plate representation were developed and benchmarked for both fuels to (1) allow for consistent comparison between designs for both fuel types and (2) assess the potential impact of low-enriched uranium conversion. These high-fidelity models were used to conduct heat deposition analyses at the beginning and end of the reactor cycle and are presented herein. This article (1) discusses the High Flux Isotope Reactor models developed to facilitate detailed heat deposition analyses of the reactor’s highly enriched and low-enriched uranium cores, (2) examines the computational approach for performing heat deposition analysis, which includes a discussion on the methodology for calculating the amount of energy released per fission, heating rates, power and volumetric heating rates, and (3) provides results calculated throughout various regions of the highly enriched and low-enriched uranium core at the beginning and end of the reactor cycle. These are the first detailed high-fidelity heat deposition analyses for the High Flux Isotope Reactor’s highly enriched and low-enriched core models with explicit fuel plate representation. Lastly, these analyses are used to compare heat distributions obtained for both fuel designs at the beginning and end of the reactor cycle, and they are essential for enabling comprehensive thermal hydraulics and safety analyses that require detailed estimates of the heat source within all of the reactor’s fuel element regions.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS1991

Isotopic compositions of carbonates and organic carbon from upper Proterozoic successions in Namibia: stratigraphic variation and the effects of diagenesis and metamorphism

The carbon isotope geochemistry of carbonates and organic carbon in the late Proterozoic Damara Supergroup of Namibia, including the Nama, Witvlei, and Gariep groups on the Kalahari Craton and the Mulden and Otavi groups on the Congo Craton, has been investigated as an extension of previous studies of secular variations in the isotopic composition of late Proterozoic seawater. Subsamples of microspar and dolomicrospar were determined, through petrographic and cathodoluminescence examination, to represent the "least-altered" portions of the rock. Carbon-isotopic abundances in these phases are nearly equal to those in total carbonate, suggesting that 13C abundances of late Proterozoic fine-grained carbonates have not been significantly altered by meteoric diagenesis, although 18O abundances often differ significantly. Reduced and variable carbon-isotopic differences between carbonates and organic carbon in these sediments indicate that isotopic compositions of organic carbon have been altered significantly by thermal and deformational processes, likely associated with the Pan-African Orogeny. Distinctive stratigraphic patterns of secular variation, similar to those noted in other, widely separated late Proterozoic basins, are found in carbon-isotopic compositions of carbonates from the Nama and Otavi groups. For example, in Nama Group carbonates delta 13C values rise dramatically from -4 to +5% within a short stratigraphic interval. This excursion suggests correlation with similar excursions noted in Ediacaran-aged successions of Siberia, India, and China. Enrichment of 13C (delta 13C> +5%) in Otavi Group carbonates reflects those in Upper Riphean successions of the Akademikerbreen Group, Svalbard, its correlatives in East Greenland, and the Shaler Group, northwest Canada. The widespread distribution of successions with comparable isotopic signatures supports hypotheses that variations in delta 13C reflect global changes in the isotopic composition of late Proterozoic seawater. Within the Damara basin, carbon-isotopic compositions of carbonates provide a potentially useful tool for the correlation of units between the Kalahari and Congo cratons. Carbonates depleted in 13C were deposited during and immediately following three separate glacial episodes in Namibia. The correspondence between ice ages and negative delta 13C excursions may reflect the effects of lowered sea levels; enhanced circulation of deep, cold, O2-rich seawater; and/or the upwelling of 13C-depleted deep water. Iron-formation is additionally associated with one of the glacial horizons, the Chuos tillite. Carbon-13 enriched isotopic abundances in immediately pre-glacial carbonates suggest that oceanographic conditions favored high rates of organic burial. It is likely that marine waters were stratified, with deep waters anoxic. A prolonged period of ocean stratification would permit the build-up of ferrous iron, probably from hydrothermal sources. At the onset of glaciation, upwelling would have brought 13C-depleted and iron-rich deep water onto shallow shelves where contact with cold, oxygenated surface waters led to the precipitation of ferric iron.

NASA Program Exobiology↗
DOE OSTI2016

Comparison of Laboratory Analytical Methods for Uranium Analysis Superior Steel FUSRAP Site - 16606

The Superior Steel Site processed uranium metal in support of the Atomic Energy Commission's fuel-element development program in the 1950's, and was subsequently classified as a Formerly Utilized Sites Remedial Action Program (FUSRAP) Site. Previous investigations at the site identified uranium contamination both inside and outside the buildings associated with historic uranium metalworking activities. The U.S. Army Corps of Engineers (USACE) is currently engaged in the Remedial Investigation (RI) phase in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, as amended. As part of the RI, gamma spectroscopy analysis of environmental samples was performed on-site using a laboratory-grade, high-purity germanium (HPGe) spectrometer. The gamma spectroscopy analysis included isotopes of uranium and their progeny. As a quality assurance measure, a subset of samples already analyzed on-site were sent to a certified, commercial, off-site laboratory for analysis using a suite of analytical methods including gamma spectroscopy, alpha spectroscopy, and mass spectroscopy. As an element of the quality assurance program implemented for the RI, an assessment of the correlations between the various analytical methods employed by both the on-site and off-site laboratory was performed. This assessment revealed inconsistencies between on-site and off-site gamma spectroscopy analytical results, which raised concerns about the appropriateness and suitability of the analytical data. To resolve the data quality concerns and better understand the source(s) of analytical results variability, the Superior Steel RI team (USACE together with its contractor, Amec Foster Wheeler) developed a quality control test whose design objective was to control or practically eliminate sampling and sample preparation variability in order to focus more clearly on analytical variability. This paper discusses the results of this supplemental quality control test, showing the differences in the various analytical methods (both on-site and off-site). It demonstrates in a practical and real world setting how sample preparation and analytical variability, if not controlled and understood can impact data quality and data defensibility. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Formation of ketene (H{sub 2}CCO) in interstellar analogous methane (CH{sub 4})-carbon monoxide (CO) ices: A combined FTIR and reflectron time-of-flight mass spectroscopic study

The formation of ketene (H{sub 2}CCO) in methane-carbon monoxide (CH{sub 4}-CO) ices was investigated upon its exposure to ionizing radiation in the form of energetic electrons at 5.5 K. The radiation-induced nonthermal equilibrium processing of these ices was monitored online and in situ via infrared spectroscopy complimented with post-irradiation temperature programmed desorption studies exploiting highly sensitive reflectron time-of-flight mass spectrometry (ReTOF) coupled with single photon fragment-free photo ionization (PI) at 10.49 eV. The detection of ketene in irradiated (isotopically labeled) methane-carbon monoxide ices was confirmed via the ν{sub 2} infrared absorption band and substantiated during the warm-up phase based on sublimation profiles obtained from the ReTOF-PI spectra of the corresponding isotopic masses. The experiments conducted with the mixed isotopic ices of {sup 12}CD{sub 4}-{sup 13}CO provide clear evidence of the formation of at least two ketene isotopomers (D{sub 2} {sup 12}C{sup 13}CO and D{sub 2} {sup 13}C{sup 13}CO), allowing for the derivation of two competing formation pathways. We have also proposed underlying reaction mechanisms to the formation of ketene based on kinetic fitting of the temporal evolution of the ketene isotopomers.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

SU-E-T-329: Tissue-Equivalent Phantom Materials for Neutron Dosimetry in Proton Therapy

Purpose: To characterize tissue equivalence of phantom materials in terms of secondary neutron production and dose deposition from neutrons produced in radiation therapy phantom materials in the context of proton therapy using Monte Carlo simulations and measurements. Methods: In order to study the influence of material choice on neutron production in therapeutic proton beams, Monte Carlo simulations using the Geant4 and MCNPX-PoliMi transport codes were performed to generate the neutron fields produced by protons of 155 and 200 MeV. A simple irradiation geometry was used to investigate the effect of different materials. The proton beams were stopped in slab phantoms to study the production of secondary neutrons. The investigated materials were water, Lucite, and tissue-equivalent phantom materials (CIRS Inc., Norfolk, VA). Neutron energy spectra and absorbed dose by neutrons and their secondary particles were scored. In addition, simulations were performed for reference tissues (ICRP/ICRU) to assess tissue equivalence with respect to neutron generation and transport. In order to benchmark the simulation results, measurements were performed with a system developed at the University of Michigan; organic liquid scintillators were used to detect the neutron emissions from the irradiation of tissue-equivalent materials. Additionally, the MPPost code was used to calculate the scintillator response from the MCNPX-PoliMi output. Results: The simulated energy spectra and depth dose curves of the neutrons produced in different phantom materials showed similar shape. The differences of spectra and fluences between all studied materials and reference tissues were well within the achievable precision of neutron dosimetry. The shape of the simulated detector response of the liquid scintillators agreed well with measurements on the proton beamline. Conclusion: Based on Geant4 and MCNPX-PoliMi simulations, the investigated materials appear to be suitable to study the production of neutrons in proton therapy. MC simulations were verified with neutron measurements in therapeutic proton beams. This work was funded in part by the ANDANTE grant of the European Commission in the 7th Framework Program.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2014

Rapid, autonomous analysis of HPGe gamma-ray spectra II: Uranium identification and characterization

RadID is a gamma-ray spectrum analysis program originally written to assist in the detection of the illicit movement of nuclear material. In this second of the three-document series we discuss how RadID detects the presence of uranium isotopes and determines a number of its characteristics, most notably or processed material and enriched estimates.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Prototype Demonstration of Gamma- Blind Tensioned Metastable Fluid Neutron/Multiplicity/Alpha Detector – Real Time Methods for Advanced Fuel Cycle Applications

The content of this report summarizes a multi-year effort to develop prototype detection equipment using the Tensioned Metastable Fluid Detector (TMFD) technology developed by Taleyarkhan [1]. The context of this development effort was to create new methods for evaluating and developing advanced methods for safeguarding nuclear materials along with instrumentation in various stages of the fuel cycle, especially in material balance areas (MBAs) and during reprocessing of used nuclear fuel. One of the challenges related to the implementation of any type of MBA and/or reprocessing technology (e.g., PUREX or UREX) is the real-time quantification and control of the transuranic (TRU) isotopes as they move through the process. Monitoring of higher actinides from their neutron emission (including multiplicity) and alpha signatures during transit in MBAs and in aqueous separations is a critical research area. By providing on-line real-time materials accountability, diversion of the materials becomes much more difficult. The Tensioned Metastable Fluid Detector (TMFD) is a transformational technology that is uniquely capable of both alpha and neutron spectroscopy while being “blind” to the intense gamma field that typically accompanies used fuel – simultaneously with the ability to provide multiplicity information as well [1-3]. The TMFD technology was proven (lab-scale) as part of a 2008 NERI-C program [1-7]. The bulk of this report describes the advancements and demonstrations made in TMFD technology. One final point to present before turning to the TMFD demonstrations is the context for discussing real-time monitoring of SNM. It is useful to review the spectrum of isotopes generated within nuclear fuel during reactor operations. Used nuclear fuel (UNF) from a light water reactor (LWR) contains fission products as well as TRU elements formed through neutron absorption/decay chains. The majority of the fission products are gamma and beta emitters and they represent the more significant hazards from a radiation protection standpoint. However, alpha and neutron emitting uranium and TRU elements represent the more significant safeguards and security concerns. Table 1.1 presents a representative PWR inventory of the uranium and actinide isotopes present in a used fuel assembly. The uranium and actinide isotopes (chiefly the Pu, Am and Cm elements) are all emitters of alpha particles and some of them release significant quantities of neutrons through spontaneous fissions

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

JMOCUP Physics Depletion Calculations for the As-Run AGR-5/6/7 TRISO Particle Experiment in ATR Northeast Flux Trap

This ECAR documents the as-run Jim Sterbentz’s MCNP ORIGEN Coupled Utility Program (JMOCUP) physics depletion calculation and the calculated results for the AGR-5/6/7 irradiation experiment in the Advanced Test Reactor (ATR). AGR 5/6/7 was irradiated for nine power cycles in the northeast flux trap. The depletion calculations were performed to provide input data for a variety of other engineering analyses supporting the AGR-5/6/7 experiment along with post-irradiation characterization of the tri-structural isotropic (TRISO) particle fuel compacts. Detailed full-core MCNP models and Oak Ridge Isotope Generation (ORIGEN2) radionuclide generation models were specifically developed as part of the JMOCUP Monte Carlo depletion calculations. The MCNP ORIGEN2 computer codes were coupled using the well-established JMOCUP utility modules to couple the two codes and run the depletion calculations. The physics calculations were performed in support of the Advanced Gas Reactor (AGR) program.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1992

An isotopic biogeochemical study of the Green River oil shale

Thirty-five different samples from three different sulfur cycles were examined in this stratigraphically oriented study of the Shell 22x-l well (U.S.G.S. C177 core) in the Piceance Basin, Colorado. Carbon isotopic compositions of constituents of Green River bitumens indicate mixing of three main components: products of primary photoautotrophs and their immediate consumers (delta approximately -30% vs PDB), products of methanotrophic bacteria (delta approximately -85%), and products of unknown bacteria (delta approximately -40%). For individual compounds synthesized by primary producers, delta-values ranged from -28 to -32%. 13C contents of individual primary products (beta-carotane, steranes, acyclic isoprenoids, tricyclic triterpenoids) were not closely correlated, suggesting diverse origins for these materials. 13C contents of numerous hopanoids were inversely related to sulfur abundance, indicating that they derived both from methanotrophs and from other bacteria, with abundances of methanotrophs depressed when sulfur was plentiful in the paleoenvironment. gamma-Cerane coeluted with 3 beta(CH3),17 alpha(H),21 beta(H)-hopane, but delta-values could be determined after deconvolution. gamma-Cerane (delta approximately -25%) probably derives from a eukaryotic heterotroph grazing on primary materials, the latter compound (delta approximately -90%) must derive from methanotrophic organisms. 13C contents of n-alkanes in bitumen differed markedly from those of paraffins generated pyrolytically. Isotopic and quantitative relationships suggest that alkanes released by pyrolysis derived from a resistant biopolymer of eukaryotic origin and that this was a dominant constituent of total organic carbon.

Non-NASA Center↗
NASA NTRS1990

Climate and atmospheric modeling studies. Climate applications of Earth and planetary observations. Chemistry of Earth and environment

The research conducted during the past year in the climate and atmospheric modeling programs concentrated on the development of appropriate atmospheric and upper ocean models, and preliminary applications of these models. Principal models are a one-dimensional radiative-convective model, a three-dimensional global climate model, and an upper ocean model. Principal applications have been the study of the impact of CO2, aerosols and the solar 'constant' on climate. Progress was made in the 3-D model development towards physically realistic treatment of these processes. In particular, a map of soil classifications on 1 degree x 1 degree resolution has been digitized, and soil properties have been assigned to each soil type. Using this information about soil properties, a method was developed to simulate the hydraulic behavior of soils of the world. This improved treatment of soil hydrology, together with the seasonally varying vegetation cover, will provide a more realistic study of the role of the terrestrial biota in climate change. A new version of the climate model was created which follows the isotopes of water and sources of water (or colored water) throughout the planet. Each isotope or colored water source is a fraction of the climate model's water. It participates in condensation and surface evaporation at different fractionation rates and is transported by the dynamics. A major benefit of this project has been to improve the programming techniques and physical simulation of the water vapor budget of the climate model.

Source record↗
NASA NTRS1988

34S/32S fractionation in sulfur cycles catalyzed by anaerobic bacteria

Stable isotopic distributions in the sulfur cycle were studied with pure and mixed cultures of the anaerobic bacteria, Chlorobium vibrioforme and Desulfovibrio vulgaris. D. vulgaris and C. vibrioforme can catalyze three reactions constituting a complete anaerobic sulfur cycle: reduction of sulfate to sulfide (D. vulgaris), oxidation of sulfide to elemental sulfur (C. vibrioforme), and oxidation of sulfur to sulfate (C. vibrioforme). In all experiments, the first and last reactions favored concentration of the light 32S isotope in products (isotopic fractionation factor epsilon = -7.2 and -1.7%, respectively), whereas oxidation of sulfide favored concentration of the heavy 34S isotope in products (epsilon = +1.7%). Experimental results and model calculations suggest that elemental sulfur enriched in 34S versus sulfide may be a biogeochemical marker for the presence of sulfide-oxidizing bacteria in modern and ancient environments.

Non-NASA Center↗
DOE OSTI2023

Fitting $\overline{ν}$ for Minor Pu Isotopes

After successful fitting of prompt ν for 235 U, 238 U, and 239 Pu(n,f) using CGMF, we have moved on to the minor plutonium isotopes. Minor isotopes pose a greater challenge both because there is less data available and we do not, by default, have parametrizations in CGMF already. Initially, we had planned to mitigate these challenges—and provide consistency within CGMF—by taking a stepped approach to the optimization. Continuing from the 239 Pu work, we would then fit 241Pu(n,f) $\overline{ν}$, where there is also a number of experimental measurements, keeping consistency between the parameters that are included in the calculation for 239 Pu and 241 Pu. With these parametrizations settled, we could consistently optimize 240 Pu(n,f) $\overline{ν}$. Following that step, we would move on to 242 Pu(n,f) (and increasing neutron number) and 238 Pu(n,f) (and decreasing neutron number). By including the fissioning systems in this manner, we should be able to minimize the unknown parameters in CGMF. We were also able to develop systematics for the CGMF input parameters along the Pu isotopic chain. However, after studies in the beginning of FY23, where we found reasonable agreement between CGMF and experimental prompt neutron multiplicities for 238−242 Pu, using a compound mass dependent parametrization from, and from discussions with I. Stetcu and P. Talou, we instead performed the evaluation of all five isotopes simultaneously. For all parameters in CGMF, they are either the same for each compound nucleus, or have a dependence on the compound mass. The details of these updates are given in. This report builds upon those details. In this short report, we first give an example of how we have updated CGMF to include 240 Pu(n,f) and 242 Pu(n,f), keeping consistency with the current 239 Pu and 241 Pu calculations, but without rigorous optimization (Sec. 2). Then, we will show in Section 3 what experimental data exist for the various isotopes to provide some insight into why 241 Pu and 239 Pu are used as anchor points. The evaluation is detailed in Section 4, and the comparison between CGMF calculations using the evaluated parameters and other prompt observables besides average neutron multiplicity are discussed in Section 2.2. Finally, we present conclusions and future work in Section 5.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2024

Consistent $\overline{ν}$ evaluation for minor Pu isotopes with CGMF

This report follows up on the evaluation work done in 2023 where we developed a procedure and performed the first consistent evaluation of the average prompt neutron multiplicity for minor Pu isotopes, including 238,240-242 Pu, using CGMF. Details on the necessary updates to the release version of CGMF, the experimental data and experimental uncertainty quantification that went into the evaluation, and this first evaluation effort are documented in and will not be repeated in this report. Instead, we discuss here the further investigations into the CGMF model space to improve the evaluation results from FY23. Additionally, we note that these evaluation results have been transformed into the ENDF format for mean values and covariances, and validation with critical assemblies has been performed; that work is documented elsewhere. In this short report, we discuss the updated evaluation efforts performed during FY24 in Sec. 2, show results from CGMF for other prompt fission observables in Sec. 3, and then briefly conclude in Sec. 4.

07 ISOTOPE AND RADIATION SOURCES↗
NASA NTRS1995

Terminal Proterozoic reorganization of biogeochemical cycles

The Proterozoic aeon (2,500-540 million years ago) saw episodic increases in atmospheric oxygen content, the evolution of multicellular life and, at its close, an enormous radiation of animal diversity. These profound biological and environmental changes must have been linked, but the underlying mechanisms have been obscure. Here we show that hydrocarbons extracted from Proterozoic sediments in several locations worldwide are derived mainly from bacteria or other heterotrophs rather than from photosynthetic organisms. Biodegradation of algal products in sedimenting matter was therefore unusually complete, indicating that organic material was extensively reworked as it sank slowly through the water column. We propose that a significant proportion of this reworking will have been mediated by sulphate-reducing bacteria, forming sulphide. The production of sulphide and consumption of oxygen near the ocean surface will have inhibited transport of O2 to the deep ocean. We find that preservation of algal-lipid skeletons improves at the beginning of the Cambrian, reflecting the increase in transport by rapidly sinking faecal pellets. We suggest that this rapid removal of organic matter will have increased oxygenation of surface waters, leading to a descent of the O2-sulphide interface to the sea floor and to marked changes in the marine environment, ultimately contributing to the Cambrian radiation.

Non-NASA Center↗
NASA NTRSDate not supplied

Am-241 Powered Dynamic Radioisotope Power System (DRPS) for Long Duration Lunar Rovers

For more than half a century most deep space and planetary missions have utilised Pu-238 as the isotope of choice for fuelling radioisotope thermoelectric generators and radioisotope heater units. In Europe, Am-241 based fuel has been selected and developed as part of the European Space Agency funded radioisotope power system program to provide technology solutions in the form of radioisotope thermoelectric generators and radioisotope heater units. A concurrent design study, in collaboration with NASA Glenn Research Centre, has been undertaken to design and develop a dynamic radioisotope power conversion concept that uses the European Large Heat Source. This is a 200 Wth Am-241 based heat source being developed for ESA and is an essential building block for the University of Leicester led radioisotope thermoelectric generator programme. This study aims to expand on the applications of the Am-241 based heat source within and outside Europe. The advancement in Am-241 power technologies could give rise to a suitable and sustainable addition to current Pu-238 based technologies, making the solar system and beyond more accessible for science and exploration mission.

Dynamic Radioisotope Power System↗
DOE OSTI2016

Analysis of dpa rates in the HFIR reactor vessel using a hybrid Monte Carlo/deterministic method

The Oak Ridge High Flux Isotope Reactor (HFIR), which began full-power operation in 1966, provides one of the highest steady-state neutron flux levels of any research reactor in the world. An ongoing vessel integrity analysis program to assess radiation-induced embrittlement of the HFIR reactor vessel requires the calculation of neutron and gamma displacements per atom (dpa), particularly at locations near the beam tube nozzles, where radiation streaming effects are most pronounced. In this study we apply the Forward-Weighted Consistent Adjoint Driven Importance Sampling (FW-CADIS) technique in the ADVANTG code to develop variance reduction parameters for use in the MCNP radiation transport code. We initially evaluated dpa rates for dosimetry capsule locations, regions in the vicinity of the HB-2 beamline, and the vessel beltline region. We then extended the study to provide dpa rate maps using three-dimensional cylindrical mesh tallies that extend from approximately 12 below to approximately 12 above the axial extent of the core. The mesh tally structures contain over 15,000 mesh cells, providing a detailed spatial map of neutron and photon dpa rates at all locations of interest. Relative errors in the mesh tally cells are typically less than 1%.

Blakeman, Edward↗
NASA NTRS1971

Ion microprobe mass analysis of lunar samples. Lunar sample program

Mass analyses of selected minerals, glasses and soil particles of lunar, meteoritic and terrestrial rocks have been made with the ion microprobe mass analyzer. Major, minor and trace element concentrations have been determined in situ in major and accessory mineral phases in polished rock thin sections. The Pb isotope ratios have been measured in U and Th bearing accessory minerals to yield radiometric age dates and heavy volatile elements have been sought on the surfaces of free particles from Apollo soil samples.

Anderson, C. A.↗