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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Development of Chemical Procedures for Isotope Harvesting: Separation of Trace Hafnium from Tungsten

The separation of trace hafnium from bulk tungsten alloys is of interest for isotope harvesting at the National Superconducting Cyclotron Laboratory and the Facility for Rare Ion Beams because 172 Hf, the parent of 172 Lu, accumulates in tungsten alloy beam blockers at these facilities. In this work, a procedure for the separation of trace hafnium from a bulk tungsten alloy (454 g) was established using tracer isotopes ( 175 Hf, 88 Zr, 173 Lu, and 88 Y). Here, the procedure employed dissolution in an HF–HNO 3 solution followed by a calcium fluoride precipitation, and then extraction chromatography was used for more selective separation steps. Two stages of column separations using LN resin (HDEHP based) and TRU resin (CMPO based) were performed. Gamma-ray spectroscopy and mass spectrometry were used to analyze the final hafnium sample and follow the steps in the chemical processing. Furthermore, the final recovery of hafnium was high (90 ± 8)%, and the mass of tungsten and other transition metals was reduced to near background levels (as determined by ICP-MS of the blank acid solutions). Zirconium follows hafnium quantitatively in this procedure; there was no detectable 173 Lu in the final hafnium sample.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Multiple chiral bands in $^{137}$Nd

Two new bands have been identified in 137 Nd from a high-statistics JUROGAM II gamma-ray spectroscopy experiment. Constrained density functional theory and particle rotor model calculations are used to assign configurations and investigate the band properties, which are well described and understood. It is demonstrated that these two new bands can be interpreted as chiral partners of previously known three-quasiparticle positive- and negative-parity bands. The newly observed chiral doublet bands in 137 Nd represent an important support to the existence of multiple chiral bands in nuclei. Overall, the present results constitute the missing stone in the series of Nd nuclei showing multiple chiral bands, which becomes the most extended sequence of odd-even and even-even nuclei presenting multiple chiral bands in the Segre chart.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Evaluation of Compton suppression for enhancing trace element identification in neutron activation analysis of reference materials

Neutron activation analysis (NAA) is a powerful technique for identifying and quantifying trace elements in materials. However, challenges such as high dead times, spectral interferences, and high Compton continuum often arise. This study employs a Compton suppression system (CSS) to enhance NAA sensitivity by reducing the Compton continuum, thereby improving the peak-to-Compton ratio. National Institute of Standards and Technology certified reference materials 1632d, 1633c, and Canadian National Research Council TORT-1 were irradiated in a thermal and epithermal neutron flux under various irradiation, decay and counting times and analyzed using high-resolution gamma-ray spectroscopy with and without Compton suppression. The reduction factor was calculated to evaluate the effectiveness of the CSS, demonstrating significant background reduction and improved detection limits for trace elements. Additional experiments with a 137Cs point source demonstrated the impact of detector-source geometry on system performance, showing a decrease in the reduction factor as the source was moved further from the NaI detector. An optimum distance between the source and HPGe detector was observed, yielding the highest peak-to-Compton ratio. The results highlight the CSS's ability to minimize spectral interference and enhance elemental identification.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Study of correlation effects in nuclei at the limit of stability. Final report

Exotic nuclei far from the valley of stability are a particularly exciting testing ground to probe nucleon-nucleon correlations in a regime where the numbers of constituent protons and neutrons are out of balance and the influence of isospin-dependent terms within the nuclear force becomes amplified. The grant DE-FG02-08ER41556 has supported from 2008 to 2019 an MSU graduate student research assistantship at the heart of a research program that explored the evolution of nuclear structure in exotic nuclei with gamma-ray spectroscopy experiments in the N=40 region of neutron-rich nuclei at NSCL and at ATLAS at Argonne National Laboratory and that mounted a new low-energy Coulomb excitation program at NSCL’s ReA accelerator within the PI’s research program. This final scientific/technical report describes the results and outcomes resulting from the support by the Department of Energy, Office of Science, Office of Nuclear Physics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Random Forest Optimization for Radionuclide Identification

Radionuclide identification through gamma-ray spectroscopy is an indispensable tool in combatting the illicit smuggling of nuclear material. The radionuclide identification devices used in the field need to provide ready-made answers to non-experts, and therefore require sophisticated algorithms that can interpret the underlying data. We investigated the Random Forest classifier as a tool for identifying the radionuclide that is consistent with the data. We were provided with training and validations data sets and used them to optimize the two hyperparameters of the classifiers: maximum features required, and minimum samples used to split each node. The F1 score, a harmonic mean of precision and recall, was used to evaluate the performance of each built classifier. We found the optimal performance with minimum samples of 5 and maximum features of 50, with the F1 score of 0.95.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
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 OSTI2023

Density Measurement of NaCl-MgCl 2 -PuCl 3 and NaCl-UCl 3 -PuCl 3 Molten Salt Systems by Neutron Radiographic Dilatometry

A novel neutron radiographic technique was developed and implemented to measure the change in volume as a function of temperature of select plutonium-containing liquid chloride mixtures from melt to 1250 K. These measurements were performed at Los Alamos National Laboratory by members of the molten salt research group under support from Gateway for Accelerated Innovation in Nuclear (GAIN) voucher NE-21-25117: “Density Measurements of Plutonium Bearing Salts via Neutron Beam Dilatometry”. This technical report contains a description of the experimental method and a summary of the results. Initial characterization of the {NaCl, MgCl 2 , UCl 3 , PuCl 3 } salts used in this experiment includes a combination of x-ray diffraction, differential scanning calorimetry, gamma ray spectroscopy, and inductively coupled plasma mass spectrometry. Four samples of NaCl + MgCl 2 + x mol% PuCl 3 and four samples of NaCl + UCl 3 + x mol% PuCl 3 were prepared at the Plutonium Facility, shipped to the Los Alamos Neutron Science Center (LANSCE), and radiographed with the density via neutron radiography (DvNR) apparatus. Density data in the form of meniscus heights were recorded as a function of temperature. The results show a linear dependence of density with temperature and a third order polynomial dependence of density with composition as a function of PuCl 3 addition in the corresponding halide salt mixture. Additions of PuCl 3 result in a significant increase in density of the salt mixture and a slight reduction in the coefficient of volumetric expansion. These results represent a first measurement of the density of plutonium chloride salt mixtures and, in combination with additional measurements, may lead to a generalized description of the density of such salt systems for arbitrary compositions and temperature.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Analysis of Radioactive 65 Zn Contamination using 3D Position Sensitive CdZnTe Detectors

SRNL NMG Goal: In collaboration with ORNL, the aim is to identify and explore innovative technology opportunities that accelerate disposition, reduce life cycle costs, minimize worker radiation exposure, and improve worker safety and minimize program risks. • This process will include 3 glovebox systems that require personnel to dilute and package the plutonium for safe storage at WIPP. • For holdup monitoring and verification, gamma ray spectroscopy and imaging are the methods employed to achieve real time analysis of the plutonium waste. 2

Nwadeyi, Valerie E.↗
DOE OSTI2025

Nuclear Material Accounting and Control (NMAC) for a Commercial Fuel Debundling Facility in the United States

The concept of fuel debundling proposes that all non-fuel components of a fuel assembly be removed prior to beginning the recycling process. It was introduced to reduce the quantity of and cost of disposing high level radioactive waste during recycling in the United States. However, nuclear material accountancy and control programs could also benefit from fuel debundling due to a reduction in self-shielding material for individual fuel rods compared to a fuel assembly. Current NRC regulations and guidance point to an independent fuel debundling facility with a material-possession-only license as the best option for implementing this concept into a used fuel recycling scheme in the United States. This allows the facility to comply only with simple NMAC requirements under Subpart B of 10 CFR Part 74 without the need to submit an NMAC plan to the NRC, exempting it from more tedious and complex NMAC requirements. However, a recycling facility may desire a Pu mass estimate from measurements of each individual fuel rod to improve accountancy into the dissolver. Many technologies and methodologies were considered for performing NMAC in an independent fuel debundling facility in the United States. Few were able to meet anticipated throughput demands of up to 3,300 rods/day and achieve measurement uncertainties suitable for input accountancy for a recycling facility. The best option was a combination of passive gamma-ray spectroscopy and neutron coincidence counting to meet all requirements for the proposed Fuel Debundling Detector (FUDD). Follow-on work will include a full uncertainty analysis to inform what assumptions can be made to meet input accountancy objectives before beginning experimental activities.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

Quantum enabled precision measurements of the 229Th nuclear isomer transition (final report)

The existence of the nuclear isomer transition in thorium-229 was first inferred from keV lines in the gamma spectrum of uranium-233 decay more than 40 years ago. Over the years, the value of the transition energy has been refined with indirect measurements using nuclear physics techniques, and the current evidence points to transition energy in the laser-accessible vacuum ultra-violet region of the spectrum. At the start of this project, the two best measurements of the transition energy were 7.8±0.5 eV and 8.28±0.17 eV from high precision gamma ray spectroscopy and kinetic energy of internal conversion electrons, respectively. This project aimed to reduce the uncertainty in the transition energy to 10 meV using direct calorimetric measurements of the decay energy with superconducting nanowire single photon detectors (SNSPDs). Specifically, the method that was pursued was to generate thorium-229 in the excited isomer state by the alpha decay of uranium-233, embed the excited state thorium into an SNSPD, then detect the energy released when the isomer deexcites.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Assembly and Initial Testing of the Gamma-Ray Emission Tomography Assessment Prototype for Irradiated Fuel

The following report documents the final development, assembly, and initial testing of the gamma-ray emission tomography assessment system (GRETA-1) for post-irradiation examination of irradiated fuel. It includes descriptions of the system components, including the high-purity germanium gamma-ray detector, the surrounding shield and collimator, the sample scanning hardware, and the control and collection software package. A series of MCNP6 simulations were performed that modeled a fuel rod scan to test image reconstruction algorithms with a complex and understood source distribution. A bench-top scan of isotopic check sources was also performed and analyzed using standard image reconstruction algorithms. The system is currently awaiting deployment at Idaho National Laboratory’s Hot Fuel Examination Facility.

46 - INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AN↗
DOE OSTI2022

Performance Study of Virtual Frisch Grid CdZnTeSe Detectors

Nuclear detectors for x-ray and gamma-ray spectroscopy and imaging are a vital tool in many homeland security, medical imaging, astrophysics and other applications. Most of these applications require room-temperature operation due to the operational constraints imposed by a cryogenic cooling system. CdZnTe (CZT) has been the main material with the desired detection properties, and CZT crystals have been used commercially for three decades. However, CdZnTe still suffers from long-standing issues of high densities of performance-limiting intrinsic defects such as Te inclusions and networks of dislocation walls (sub-grain boundaries). A recently invented new quaternary material CdZnTeSe showed excellent material properties for radiation detection. The material was found to be free from dislocation networks, possess reduced Te inclusions, and have better compositional homogeneity. Virtual Frisch grid detectors were fabricated from crystals taken from a CdZnTeSe ingot that was grown by the traveling heater method. The detectors were fabricated from an as-grown ingot, bypassing the post-growth annealing process commonly practiced for industrial-grade CZT. The performances of the detectors were studied with different Frisch grid lengths using an amplifier shaping time ranging from 1–6 µs. The detectors showed high-quality spectroscopic performance with an as-measured energy resolution of ~1.1% at 662 keV for an optimum Frisch grid length of 3 mm. The charge collection was observed to enhance for longer Frisch grids.

47 OTHER INSTRUMENTATION↗
NASA NTRS1972

Apollo 15 geochemical X-ray fluorescence experiment - Preliminary report.

Although only part of the information from the X-ray fluorescence geochemical experiment has been analyzed, it is clear that the experiment was highly successful. Significant compositional differences among and possibly within the maria and highlands have been detected. When viewed in the light of analyzed lunar rocks and soil samples, and the data from other lunar orbital experiments (in particular, the Apollo 15 gamma-ray spectroscopy experiment), the results indicate the existence of a differential lunar highland crust, probably feldspathic. This crust appears to be related to the plagioclase-rich materials previously found in the samples from Apollo 11, Apollo 12, Apollo 14, Apollo 15, and Luna 16.

Adler, I.↗
NASA NTRS1974

Skylab neutron environment experiment (Science Demonstration SD-34 (TV108)). Description and preliminary results

Neutron and proton induced radioactivity at various locations within Skylab were measured. Samples of five metals were formed into activation packets and deployed at the following locations on the Skylab 4 mission: orbital workshop film vault, water storage tank, and two opposing orbital workshop internal locations. Radioactive nuclides were produced in the packets by nuclear interactions of high-energy protons and secondary neutrons within Skylab. Low-level gamma ray spectroscopy measurements were made on the returned packets to determine the incident neutron and proton fluxes and spectra and their variations with mass distribution.

Fishman, G. J.↗
NASA NTRS1974

Determination of natural and cosmic ray induced radionuclides in Apollo 17 lunar samples

Natural and cosmic ray induced radionuclides have been determined in 15 rocks and 7 soils from the Apollo 17 mission by nondestructive gamma-ray spectroscopy. The Th and K contents of these rocks and soils are shown to be linear functions of the U contents. Large amounts of Co-56, Sc-46, and Mn-54 were found in these samples due to the large proton-accelerating flares which occurred between August 2 and 6, 1972. The behavior of the Co-56 activity as a function of the Mn-54 activity seems to be the result of variation in surface to volume ratios among the samples and exposure angle. It is not necessary to invoke an asymetric solar flare flux to explain this behavior.

Keith, J. E.↗
NASA NTRS1976

The Identification of Scientific Programs to Utilize the Space Environment

A program to identify and develop ideas for scientific experimentation on the long duration exposure facility (LDEF) was completed. Four research proposals were developed: (1) Ultra pure germanium gamma ray radiation detectors in the space environment, intended to develop and demonstrate an X-ray and gamma-ray spectroscopy system incorporating a temperature cyclable high-purity germanium detector and diode heat pipe cryogenic system for cooling, (2) growth, morphogenesis and metabolism of plant embryos in the zero-gravity environment, to investigate if the space environment induces mutations in the embryogenic cells so that mutants of commercial significance with desirable attributes may be obtained, (3) effect of zero gravity on the growth and pathogenicity of selected zoopathic fungi. It is possible that new kinds of treatment for candidiasis, and tichophytosis could eventuate from the results of the proposed studies, and (4) importance of gravity to survival strategies of small animals. Gravitational effects may be direct or mediate the selection of genetic variants that are preadapted to weightlessness.

Kulacki, F. A.↗