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At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
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Accessing Icy World Oceans using Lattice Confinement Fusion Fast Fission

Exploring the oceans of icy moons and planets requires a robust robotic probe powered by an energy source that can operate under icy world ocean conditions and be self-contained. We propose a non-fissile, compact, scalable nuclear energy source to electrically power untethered, autonomous probes to melt or bore through icy world crusts. The probe can be used for planetary (i.e. Pluto, lunar (i.e., Europa), or asteroid exploration (i.e. Ceres) where ice caps are encountered. This new approach may yield a variable output fission power source with a higher performance than 238Pu and a non-fissile alternative to a highly enriched uranium (HEU) core. This approach saves uranium enrichment expense, and both HEU and 238Pu security and launch safety costs. The reactor will produce electrical power with thermal waste heat to melt through the ice crust with possible sonic assistance. This paper will introduce the hybrid fusion-fission reactor concept, explore the potential for and benefits of this new type of nuclear reactor, and discuss the technical approach to developing this new technology.

Theresa L Benyo↗
NASA NTRS2023

Accessing Icy Worlds Using Lattice Confinement Fusion (LCF) Fast Fission

Exploring the oceans of icy moons and planets requires a robust robotic probe powered by an energy source that can operate under icy world ocean conditions and be self-contained. We propose a non-fissile, compact, scalable nuclear energy source to electrically power untethered, autonomous probes to melt or bore through icy world crusts. The probe can be used for planetary (i.e. Pluto, lunar (i.e., Europa), or asteroid exploration (i.e. Ceres) where ice caps are encountered. This new approach may yield a variable output fission power source with a higher performance than 238Pu and a non-fissile alternative to a highly enriched uranium (HEU) core. This approach saves uranium enrichment expense, and both HEU and 238Pu security and launch safety costs. The reactor will produce electrical power with thermal waste heat to melt through the ice crust with possible sonic assistance. This NIAC funded proposal and presentation will introduce the hybrid fusion-fission reactor concept applied to the Saturnian moon, Enceladus, explore the potential for and benefits of this new type of nuclear reactor, and discuss applying this new technology.

Icy Worlds↗
DOE OSTI2020

A Bayesian analysis of nuclear deformation properties with Skyrme energy functionals

In spite of numerous scientific and practical applications, there is still no comprehensive theoretical description of the nuclear fission process based solely on protons, neutrons and their interactions. Furthermore, the most advanced simulations of fission are currently carried out within nuclear density functional theory (DFT). In spite of being fully quantum-mechanical and rooted in the theory of nuclear forces, DFT still depends on a dozen or so parameters characterizing the energy functional. Calibrating these parameters on experimental data results in uncertainties that must be quantified for applications. This task is very challenging because of the high computational cost of DFT calculations for fission. In this paper, we use Gaussian processes to build emulators of DFT models in order to quantify and propagate statistical uncertainties of theoretical predictions for a range of nuclear deformations relevant to describing the fission process.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Application of MELCOR for Simulating Molten Salt Reactor Accident Source Terms

Molten Salt Reactor (MSR) systems can be divided into two basic categories: liquid-fueled MSRs in which the fuel is dissolved in the salt, and solid-fueled systems such as the Fluoride-salt-cooled High-temperature Reactor (FHR). The molten salt provides an impediment to fission product release as actinides and many fission products are soluble in molten salt. Nonetheless, under accident conditions, some radionuclides may escape the salt by vaporization and aerosol formation, which may lead to release into the environment. Here, we present recent enhancements to MELCOR to represent the transport of radionuclides in the salt and releases from the salt. Some soluble but volatile radionuclides may vaporize and subsequently condense to aerosol. Insoluble fission products can deposit on structures. Thermochimica, an open-source Gibbs Energy Minimization (GEM) code, has been integrated into MELCOR. With the appropriate thermochemical database, Thermochimica provides the solubility and vapor pressure of species as a function of temperature, pressure, and composition, which are needed to characterize the vaporization rate and the state of the salt with fission products. Since thermochemical databases are still under active development for molten salt systems, thermodynamic data for fission product solubility and vapor pressure may be user specified. This enables preliminary assessments of fission product transport in molten salt systems. In this paper, we discuss modeling of soluble and insoluble fission product releases in a MSR with Thermochimica incorporated into MELCOR. Separate-effects experiments performed as part of the Molten Salt Reactor Experiment in which radioactive aerosol was released are discussed as needed for determining the source term.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS2007

Advanced Stirling Technology Development at NASA Glenn Research Center

The NASA Glenn Research Center has been developing advanced energy-conversion technologies for use with both radioisotope power systems and fission surface power systems for many decades. Under NASA's Science Mission Directorate, Planetary Science Theme, Technology Program, Glenn is developing the next generation of advanced Stirling convertors (ASCs) for use in the Department of Energy/Lockheed Martin Advanced Stirling Radioisotope Generator (ASRG). The next-generation power-conversion technologies require high efficiency and high specific power (watts electric per kilogram) to meet future mission requirements to use less of the Department of Energy's plutonium-fueled general-purpose heat source modules and reduce system mass. Important goals include long-life (greater than 14-yr) reliability and scalability so that these systems can be considered for a variety of future applications and missions including outer-planet missions and continual operation on the surface of Mars. This paper provides an update of the history and status of the ASC being developed for Glenn by Sunpower Inc. of Athens, Ohio.

Shaltens, Richard K.↗
DOE OSTI2026

Radiation damage in tungsten under high-energy He-ion irradiation

Tungsten (W) is a primary candidate for plasma-facing components (PFCs) in fusion reactors and hybrid fission-fusion reactors. However, W suffers from severe microstructural damage under Helium (He) ion irradiation in operation conditions. Key irradiation parameters, including incident ion energy, fluence, and irradiation temperature, are known to determine the formation of He bubbles and dislocation loops, which ultimately lead to the degradation of mechanical properties, such as radiation hardening and ductile-to-brittle transition temperature (DBTT) shifts. Various strategies, for instance, interface engineering and alloying, have been developed to enhance He irradiation tolerance in W to address these challenges. Studies in the recent two decades have enhanced the understanding of the underlying mechanisms that drive defect evolution and mechanical performance degradation, thereby offering more insights into the design of more resilient W-based materials for extreme environments.

Liu, Yinghang [Purdue University]↗
DOE OSTI2021

Signature Analysis Utilizing a Dynamic Molten Salt Reactor Model for MC&A

Moving from traditional fixed fuel nuclear reactor systems to a mobile, dynamic fuel system that has dissolved special nuclear material in a molten salt is a paradigm shift in several respects. One major consideration is how to develop effective nuclear material controls and accounting for these novel reactor systems. The Molten Salt Reactor Experiment is one example of a critical molten salt system and provided a significant reference library based on the documented effort. But it was low thermal power that was not intended to reflect a commercial scale electricity production design. Therefore, to facilitate and assist vendors with domestic licensing considerations, research is underway to identify methods that could be used for domestic safeguards approaches for these novel reactor systems. This research presents the results of a signature analysis of data generated from three simulated scenarios using the molten salt demonstration reactor model defined in the Transient Simulation Framework of Reconfigurable Modules. Each scenario provides 1 hour isotope inventories over a 180 day period. The scenarios investigated provide test cases to examine if direct gamma-ray spectroscopy of the fuel can be used to identify changes comparing a base case (no reactivity control and fixed fission contribution) to an insertion of reactivity (10 pcm no change in fission composition) and a change in fission composition. The analysis demonstrates that monitoring the total count rate in a highly collimated high-resolution photon energy spectrum is sensitive to perturbations imposed into the reactor model. The total photon count rate changes ≈2% for the fission composition change and ≈4.5% for the reactivity insertion compared to the base case. However, both scenarios show an increase in the total photon count rate. The total photon count rate can be used to identify changes due to power (number of fissions) but not due to a change in the material undergoing fission. To distinguish between the two cases of increased power, the photon spectrum would require an intensive analysis technique. A photon peak count rate ratio analysis could be used to identify changes in the fissile material fission generation in the core through identification of a static peak that shows little variation to the source of fission and a highly varying peak. The photon peak strength will ultimately be determined by the isotope’s fission yield. A preliminary analysis investigating the coupling of the isotope’s fission yield and its concentration in the fuel salt derived from the modeling has been performed. A ratio analysis of the photon peak count rates of 140 La to 99 Mo demonstrated that the reactivity insertion creates a distinct difference in the ratio compared to the fission composition change scenario.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2024

Development of Lightweight Structural Materials with Improved Properties for Fission Batteries

The notion of a “fission battery” conveys a vision focused on realizing very simple “plug-and-play” nuclear systems that can be integrated into a variety of applications requiring affordable, reliable energy in the form of electricity and/or heat and function without operations and maintenance staff. Fission batteries require lightweight structural materials to increase their mobility, and the lightweight materials must demonstrate structural resilience under various conditions. The objective of this work is to develop lattice structured lightweight structural material featuring a good combination of mechanical properties using advanced modeling and simulation together with an advanced additive manufacturing technique such as laser powder bed fusion. The preliminary results show that different lattice structures and types can be successfully meshed using nTopology software, and the lattice structure data can be successfully transformed to Multiphysics Object-Oriented Simulation (MOOSE) Environment input. Finite Element Analysis (FEA) displays that, at macro/engineering scale simulation, the weight saving design has an obvious effect on tensile behavior such as effective elastic modulus and yield stress. The novel approaches of this work are (1) development of lattice structures for improved mechanical properties using advanced simulation and modeling techniques; and (2) model predictions of the mechanical properties (e.g., strength and stress distribution) of macroscopic materials in order to preliminarily select a lattice structure for additive manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2024

COMPUTER-AIDED LATTICE DESIGN AND ADVANCED MODELING FOR THE DEVELOPMENT OF LIGHTWEIGHT STRUCTURAL MATERIALS

The notion of a “fission battery” conveys a vision focused on realizing very simple “plug-and-play” nuclear systems that can be integrated into a variety of applications requiring affordable, reliable energy in the form of electricity and/or heat and function without operations and maintenance staff. Fission batteries require lightweight structural materials to increase their mobility, and the lightweight materials must demonstrate structural resilience under various conditions. The objective of this work is to develop lattice structured lightweight structural material featuring a good combination of mechanical properties using advanced modeling and simulation together with an advanced additive manufacturing technique such as laser powder bed fusion. The preliminary results show that different lattice structures and types can be successfully meshed using nTopology software, and the lattice structure data can be successfully transformed to Multiphysics Object-Oriented Simulation (MOOSE) Environment input. Finite Element Analysis (FEA) displays that, at macro/engineering scale simulation, the weight saving design has an obvious effect on tensile behavior such as effective elastic modulus and yield stress. The novel approaches of this work are (1) development of lattice structures for improved mechanical properties using advanced simulation and modeling techniques; and (2) model predictions of the mechanical properties (e.g., strength and stress distribution) of macroscopic materials in order to preliminarily select a lattice structure for additive manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Development of Lightweight Structural Materials with Improved Properties for Fission Batteries

The notion of a “fission battery” conveys a vision focused on realizing very simple “plug-and-play” nuclear systems that can be integrated into a variety of applications requiring affordable, reliable energy in the form of electricity and/or heat and function without operations and maintenance staff. Fission batteries require lightweight structural materials to increase their mobility, and the lightweight materials must demonstrate structural resilience under various conditions. The objective of this work is to develop lightweight structural material featuring a good combination of mechanical properties using advanced modeling and simulation together with an advanced additive manufacturing technique such as laser powder bed fusion. The preliminary results show that different lattice structures and types can be successfully meshed using nTopology software, and the lattice structure data can be successfully transformed to Multiphysics Object-Oriented Simulation Environment (MOOSE) input. Finite Element Analysis (FEA) displays that, at macro/engineering scale simulation, the weight saving design has an obvious effect on tensile behavior such as effective elastic modulus and yield stress. The novel approaches of this work are (1) development of optimized lattice structures for improved mechanical properties using advanced simulation and modeling techniques; and (2) model predictions of the mechanical properties (e.g., strength and stress distribution) of macroscopic materials in order to preliminarily select a lattice structure for additive manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Deciphering Nb 98 β decay with the Modular Total Absorption Spectrometer at ORNL

An assessment done under the auspices of the Organization for Economic Co-operation and Developement Nuclear Energy Agency (OECD-NEA) in 2007 suggested that the β decays of many abundantly produced fission products in nuclear reactors may be incomplete. In this assessment, the fission product 98 Nb was assigned the highest priority for study by total absorption spectroscopy due to its large cumulative fission branching fraction and because the β-decay data from several experiments are discrepant. To obtain the complete β-decay feeding pattern of 98 Nb and determine the impact on the average γ energy per 98 Nb β decay and v¯e emission calculations. The complete 98 Nb β-decay feeding pattern includes ground-state to ground-state β feeding and direct β feeding to the 0 + first-excited state (both have no associated γ rays), and the ground-state to excited-state β transitions followed by γ transitions to the ground state of the daughter nucleus, 98 Mo. The complete β-decay intensities of 98 Nb were measured with the Modular Total Absorption Spectrometer at Oak Ridge National Laboratory (ORNL). Here, the 98 Nb was produced by the β decay of mass 98 fission fragments at ORNL's On-Line Test Facility (OLTF) using proton-induced fission of 238 U. We find that changes to the current ENSDF assessment of 98 Nb β-decay intensity are required. We report improved uncertainties for the β-decay feeding values and report new β feedings to high-energy levels in 98 Mo. A more complete 98 Nb β-feeding pattern with improved accuracy and precision is offered. The impacts of the measured changes to the 98 Nb β-feeding pattern on both reactor decay heat calculations and predicted detection rates of reactor v¯e are presented. The Modular Total Absorption Spectrometer measurements of 98 Nb demonstrate the importance of reexamining and remeasuring complex β-decaying fission products with total absorption spectroscopy, including nuclei very near β stability.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Shedding light on the 239Pu fission source term with new high-precision experiments and advanced fission modeling

In the last decade, there has been a renaissance of fission research resulting in new high-precision experiments and advanced fission modeling. For instance, the Chi-Nu and CEA teams supplied, for the first time, the 239 Pu prompt fission neutron spectrum (PFNS) for broad ranges of incident and outgoing neutron energies. The CEA team also measured 239 Pu average prompt neutron multiplicities, ν ̄ p , with lower statistical uncertainties and a technique significantly different than the one used in the past. The NIFFTE collaboration provided 239 Pu( n ,f)/ 235 U( n ,f) cross section shape ratios with uncertainties below 1% utilizing a novel detector type. Advanced fission event generators were developed, among them CGMF, FIFRELIN, FREYA, and GEF, which calculate post-scission fission observables in a correlated manner. These new experimental data and more consistent fission models change the evaluated PFNS, ν ̄ p , and ( n ,f) cross sections, some only modestly, compared to ENDF/B-VIII.0. In turn, the individual new nuclear data distinctly change simulated effective neutron multiplication factors of fast critical assemblies, but their combined impact is small, while affecting the prediction of LLNL pulsed sphere neutron leakage spectra and reaction rates only within experimental uncertainties. Also, the parameters obtained from fitting to ν ̄ p reproduce various post-scission fission observables within the uncertainties of experimental data. This indicates that new differential experiments and consistent fission modeling reduce compensating errors present in ENDF/B-VIII.0.

fission cross section↗
NASA NTRS1990

A new method for using Cf-252 in SEU testing

A system using Cf-252 and associated nuclear instrumentation has determined the single-event upset (SEU) cross section versus linear energy transfer (LET) curve for several 2K x 8 static random access memories (SRAMs). The Cf-252 fission fragments pass through a thin-film organic scintillator detector (TFD) on the way to the device under test (DUT). The TFD provides energy information for each transiting fragment. Data analysis provides the energy of the individual ion responsible for each SEU; thus, separate upset cross sections can be developed for different energy and mass regions of the californium spectrum. This californium-based device is quite small and fits onto a bench top. It provides a convenient and inexpensive supplement or alternative to accelerator and high-altitude/space SEU testing.

Costantine, A.↗
DOE OSTI2020

Calculations of Astrophysical Reaction Rates Using ENDF/B-VIII.0 Library

Recent observations of neutron stars merger (GW170817) renewed interest in stellar nucleosynthesis. Stellar nucleosynthesis modeling requires fully traceable, unbiased, high fidelity nuclear data. The Evaluated Nuclear Data File (ENDF) libraries contain complete collections of reaction data sets over the nuclear industry standard 10 -5 eV - 20 MeV energy span. For the first time, the (n,γ), (n,fission), (n,p), and (n,α) astrophysical reaction rates were computed within the 0.01-10 GK range of temperatures using the ENDF/B-VIII.0 library, and nuclear Reaction rate Library for astrophysics (REACLIB) fit parameters were deduced. The present results were used to estimate the slow neutron capture timescale. These findings demonstrate the potential astrophysical applications of the ENDF libraries and the complementary relations between the nuclear industry and astrophysics data developments.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

H 2 generation by the 10 B(n,α) 7 Li reaction in high temperature water

H 2 produced in water from the 10 B(n,α) 7 Li fission reaction has been measured up to 300 °C. Thermal energy neutrons from the Rhode Island Nuclear Science Center's 2 MW reactor interact with boric acid-containing water in temperature-controlled high-pressure cells made from tubing of either titanium or zirconium alloy. After exposure for a minimum of 1 h, the solution sample is extracted and sparged with argon. The H 2 entrained by the sparging gas is sampled with a small mass spectrometer. A small amount of sodium is included in the boric acid solution so that after sparging, samples can be collected for 24 Na activation measurements in a gamma spectrometer to determine the neutron exposure and thus the total energy deposited in solution. The G-value (μmol/J) for H 2 production is obtained for water at a pressure of 25 MPa, over a temperature range from 20 °C to 300 °C. The weak temperature dependence of this yield between 150 °C and 200 °C demonstrates that the bimolecular reaction of pairs of e$^{–}_{aq}$ is a very minor source of H 2 in high LET tracks.

10B↗
DOE OSTI2022

First observation of isomeric states in 111 Zr, 113 Nb, and 115 Mo

Isomeric states in the neutron-rich nuclei 111 Zr [T 1/2 =0.10 (7) μs] , 113 Nb [T 1/2 =0.7 (4) μs], 115 Mo [T 1/2 =46 (3) μs] were first identified at the Radioactive Ion Beam Factory (RIBF) of RIKEN by using in-flight fission and fragmentation of a 238 U beam at an energy of 345 MeV/u. Here is a brief report of the γ transitions de-exciting from isomeric states and half-lives measurements, which provides the first spectroscopy in the nuclear region of prolate-to-oblate shape-phase transition around mass A ≈110.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1972

Artificial perturbations of the radiation belts

A review is given of the properties of the radiation belts which have been produced by high-altitude nuclear detonations. The low-yield, Argus devices, 1, 2, and 3, and the Soviet test of 1 November 1962 injected intense electron fluxes in narrow L-shell intervals, with peaks at L = 1.72, 2.11, 2.17, and 1.77, respectively. The energy spectra of the electrons were indistinguishable from the equilibrium fission beta spectrum, and the fluxes initially decayed at rates approximately proportional to (time) sup -1.1. The high-yield devices, Starfish and the Soviet tests of 22 October and 28 October 1962, injected electrons over wide ranges. At L values near the lower boundary, the electron spectra appeared to be softer at the higher L values.

Cladis, J. B.↗