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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Baseline CGMF Calculations for Pu Isotopes

Updates were made to CGMF to run neutron-induced fission calculations on Pu isotopes of A =238, 239, 240, 241, and 242 (the release version of CGMF can calculate 239,241 Pu(n,f) and 238,240,242 Pu(sf) only). Here, we show the baseline calculations from CGMF for these neutron-induced fission reactions, including updates made for total kinetic energy systematics and fission barriers fit to be more consistent with the neutron-induced fission cross section.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Predicted thermophysical properties of UN, PuN and (U,Pu)N

Molecular dynamics and density functional theory simulations are used to predict the lattice and electronic contributions of thermophysical properties for UN, PuN, and mixed (U,Pu)N systems. The properties predicted include the lattice parameter, linear thermal expansion, enthalpy, and specific heat capacity, as a function of temperature. The simulation predictions for high temperature specific heat capacity are compared against experimental measurements to understand the behavior, and why differences in the experimental measurements are observed. The influence of adding U vacancies, N interstitials, and Pu to UN is also examined. For this, a new PuN potential parameter set is developed and used with the Kocevski UN potential, enabling the dynamics of mixed (U,Pu)N systems to be studied. How defects impact the thermophysical properties is important for understanding fuel behavior under different reactor conditions, and these mechanistic predictions can be used to support fuel performance codes where data is scarce.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Dark Matter Search in Pu-241 Beta Decays

Our universe is predominantly composed of mysterious unknowns: Dark Matter (DM) and Dark Energy. DM constitutes approximately 27% of the universe, yet its nature and origins remain elusive. Among the various candidates for dark matter, this project focuses on the search for keV-scale sterile neutrinos. A sterile neutrino is a hypothetical particle that belongs to the neutrino family and may possess a higher mass than ordinary neutrinos. They are considered a compelling warm dark matter candidate if their mass is on the order of kilo-electronvolts. Existence of sterile neutrinos can be investigated via high precision beta spectroscopy. Sterile neutrinos can be produced during nuclear beta decay processes, similar to ordinary active neutrinos, but they uniquely alter the beta decay spectrum. The emission of sterile neutrinos will introduce a distinctive "kink" structure in the middle of the beta spectrum. This project investigated the existence of sterile neutrino dark matter by employing high-precision decay energy spectroscopy of Pu-241 beta decays using magnetic microcalorimeters (MMCs). The Pu-241 source material is embedded within the microcalorimeter detectors, enabling the measurement of full beta decay energies with ultra-high energy resolution. In this project, the most precise Pu-241 spectrum to date was obtained by collecting a total of 1 billion beta decay events in the MMC detectors. This extensive data set allows us to investigate evidence of keV sterile neutrino emission in beta decays with unprecedented sensitivity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

From Cryogenic to High Temperatures: A Microstructural Evolution of δ-phase Pu-Ga Alloys Investigated by Time-of-Flight High-resolution Neutron Diffraction

Phase stability and phase transformations in binary Pu alloys are critical for multiple applications. Long-term phase stability affects mechanical properties, microstructure, corrosion behavior, and structural integrity. A clear and detailed understanding of phase transformations and phase stability mechanisms is necessary to assess the behavior and response to unexpected stimuli. Gaining advanced knowledge on the behavior of Pu and Pu alloys at a variety of temperatures, pressures, and time will ensure better predictions and control on evolution outside laboratory measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2026

FY26 MID-YEAR REPORT 238 Pu Measurement in Bulk Environmental Samples by Thermal Ionization Mass Spectrometry (TIMS)

Funding was received in December 2026 to optimize a nascent measurement capability for mass spectrometry of 238 Pu, as it would apply to relevant environmental collections in safeguards applications, i.e. NWAL swipes or other bulk collections such as soil, sediment, waters, or air filters. The measurement relies on differing ionization temperatures for U and Pu during thermal ionization and therefore leverages TIMS to partially separate and measure these elements. Collected counts of 238 Pu can be mathematically corrected for interfering counts of background 238 U, by addition of a U tracer (e.g. 235 U) to account for the 238 U present. The method has undergone initial characterization at LANL regarding detection limit, precision, and accuracy but requires further applicability-testing for possible use in safeguards.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Spectroscopic analysis of Pu-bearing compounds in double-walled cells

Spectroscopic analysis of radiological materials has been historically limited to radiological labs with older or less advanced scientific instrumentation. The development of double-walled cells (DWCs) at the Savannah River National Laboratory (SRNL) has enabled Pu-bearing compounds to be removed from radiological laboratories and studied in our radiologically clean spectroscopy laboratory with state-of-the-art instrumentation. In this manuscript, we discuss the contributions of DWCs that have allowed the application of Raman spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), diffuse reflectance spectroscopy (DRS) in the shortwave infrared, and gamma spectroscopy at SRNL. Significant advances have been made in the understanding of the thermal decomposition of Pu(III) and Pu(IV) oxalates, alpha-induced damage to the PuO 2 crystal lattice, and the effect of calcination temperatures on the quality of PuO 2 . These techniques have enabled methods to conduct PuO 2 age dating since last calcination and estimate the calcination temperature with Raman spectroscopy and DRS. Additional spectroscopic information measured with DRIFTS has enabled the observation of the evolution of carbon species with calcination temperature, while gamma spectroscopy provides information on age dating since last purification.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Inhomogeneous Enrichment of Radioactive Nuclei in the Galaxy: Deposition of Live 53 Mn, 60 Fe, 182 Hf, and 244 Pu into Deep-sea Archives. Surfing the Wave?

Abstract While modeling the galactic chemical evolution (GCE) of stable elements provides insights to the formation history of the Galaxy and the relative contributions of nucleosynthesis sites, modeling the evolution of short-lived radioisotopes (SLRs) can provide supplementary timing information on recent nucleosynthesis. To study the evolution of SLRs, we need to understand their spatial distribution. Using a three-dimensional GCE model, we investigated the evolution of four SLRs: 53 Mn, 60 Fe, 182 Hf, and 244 Pu with the aim of explaining detections of recent (within the last ≈1–20 Myr) deposition of live 53 Mn, 60 Fe, and 244 Pu of extrasolar origin into deep-sea reservoirs. We find that core-collapse supernovae are the dominant propagation mechanism of SLRs in the Galaxy. This results in the simultaneous arrival of these four SLRs on Earth, although they could have been produced in different astrophysical sites, which can explain why live extrasolar 53 Mn, 60 Fe, and 244 Pu are found within the same, or similar, layers of deep-sea sediments. We predict that 182 Hf should also be found in such sediments at similar depths.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Spectroscopic Analysis of Pu-bearing Compounds in Double-Walled Cells

Spectroscopic analysis of radiological materials has been historically limited to radiological labs with 11 older or less advanced scientific instrumentation. The development of double-walled cells (DWCs) at 12 the Savannah River National Laboratory (SRNL) has enabled Pu-bearing compounds to be removed 13 from radiological laboratories and studied in our radiologically clean spectroscopy lab with state-of14 the-art instrumentation. In this manuscript, we discuss the contributions of DWCs that have allowed 15 the application of Raman spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy 16 (DRIFTS), diffuse reflectance spectroscopy (DRS) in the shortwave infrared, and gamma 17 spectroscopy at SRNL. Significant advances have been made in the understanding of thermal 18 decomposition of Pu(III) and Pu(IV) oxalates, the alpha-induced damage to the PuO2 crystal lattice, 19 and the effect of calcination temperatures to the quality of PuO2. These techniques have enabled 20 methods to conduct PuO2 age dating since last calcination and estimate the calcination temperature 21 with Raman and DRS. Additional spectroscopic information measured with DRIFTS has provided a 22 path to observe the evolution of carbon species with calcination temperature while gamma 23 spectroscopy provides information on age dating since last purification.

Villa-Aleman, Eliel↗
DOE OSTI2020

Materials Data on Pu(SiPd)2 by Materials Project

Pu(PdSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pu4+ is bonded to eight equivalent Si4- atoms to form PuSi8 hexagonal bipyramids that share corners with sixteen equivalent PdSi4 tetrahedra, edges with four equivalent PuSi8 hexagonal bipyramids, edges with eight equivalent PdSi4 tetrahedra, and faces with four equivalent PuSi8 hexagonal bipyramids. All Pu–Si bond lengths are 3.08 Å. Pd2+ is bonded to four equivalent Si4- atoms to form PdSi4 tetrahedra that share corners with eight equivalent PuSi8 hexagonal bipyramids, corners with four equivalent PdSi4 tetrahedra, edges with four equivalent PuSi8 hexagonal bipyramids, and edges with four equivalent PdSi4 tetrahedra. All Pd–Si bond lengths are 2.48 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Pu4+, four equivalent Pd2+, and one Si4- atom. The Si–Si bond length is 2.30 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu(CuSi)2 by Materials Project

Pu(CuSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pu6+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All Pu–Si bond lengths are 3.05 Å. Cu1+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing CuSi4 tetrahedra. All Cu–Si bond lengths are 2.39 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Pu6+, four equivalent Cu1+, and one Si4- atom. The Si–Si bond length is 2.35 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu(SiAu)2 by Materials Project

Pu(AuSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pu3+ is bonded to eight equivalent Si4- atoms to form PuSi8 hexagonal bipyramids that share corners with sixteen equivalent AuSi4 tetrahedra, edges with four equivalent PuSi8 hexagonal bipyramids, edges with eight equivalent AuSi4 tetrahedra, and faces with four equivalent PuSi8 hexagonal bipyramids. All Pu–Si bond lengths are 3.25 Å. Au+2.50+ is bonded to four equivalent Si4- atoms to form AuSi4 tetrahedra that share corners with eight equivalent PuSi8 hexagonal bipyramids, corners with four equivalent AuSi4 tetrahedra, edges with four equivalent PuSi8 hexagonal bipyramids, and edges with four equivalent AuSi4 tetrahedra. All Au–Si bond lengths are 2.58 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Pu3+, four equivalent Au+2.50+, and one Si4- atom. The Si–Si bond length is 2.31 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu(SeO3)2 by Materials Project

Pu(SeO3)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Pu4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Pu–O bond distances ranging from 2.22–2.52 Å. There are two inequivalent Se4+ sites. In the first Se4+ site, Se4+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There are a spread of Se–O bond distances ranging from 1.71–1.78 Å. In the second Se4+ site, Se4+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There are a spread of Se–O bond distances ranging from 1.72–1.75 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Pu4+ and one Se4+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Pu4+ and one Se4+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Pu4+ and one Se4+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Pu4+ and one Se4+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pu4+ and one Se4+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Pu4+ and one Se4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu(BRu)4 by Materials Project

Pu(RuB)4 crystallizes in the tetragonal I4_1/acd space group. The structure is three-dimensional. Pu3+ is bonded in a 12-coordinate geometry to twelve equivalent B3- atoms. There are a spread of Pu–B bond distances ranging from 2.96–3.20 Å. Ru+2.25+ is bonded to five equivalent B3- atoms to form a mixture of distorted edge and corner-sharing RuB5 trigonal bipyramids. There are a spread of Ru–B bond distances ranging from 2.13–2.26 Å. B3- is bonded in a 6-coordinate geometry to three equivalent Pu3+, five equivalent Ru+2.25+, and one B3- atom. The B–B bond length is 1.76 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu(Mo3Se4)2 by Materials Project

Pu(Mo3Se4)2 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Pu3+ is bonded in a body-centered cubic geometry to eight Se2- atoms. There are two shorter (2.88 Å) and six longer (3.17 Å) Pu–Se bond lengths. Mo+2.17+ is bonded to five Se2- atoms to form a mixture of edge and corner-sharing MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.54–2.77 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 1-coordinate geometry to one Pu3+ and three equivalent Mo+2.17+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to one Pu3+ and four equivalent Mo+2.17+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu(MoO4)2 by Materials Project

Pu(MoO4)2 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Pu4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Pu–O bond distances ranging from 2.28–2.47 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.77–1.83 Å. In the second Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.78–1.80 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pu4+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pu4+ and one Mo6+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pu4+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Pu4+ and one Mo6+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pu4+ and one Mo6+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pu4+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pu4+ and one Mo6+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pu4+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Configuration–Interaction Perturbation Theory Calculations of Pu II

Configuration–interaction perturbation theory (CI–PT) is applied to calculations of low-energy states of Pu II. This ion is quite challenging due to a large number of possible determinants arising from seven valence electrons and strong relativistic effects. The CI–PT calculations agree with experiments for the energies and g-factors for many low-energy states that allowed positive identification of the theoretical levels. Isotope shifts were also used to aid in identification, and, in case of the odd states, fitting with three independent parameters was used to match theoretical isotope shifts to the experimental values with good accuracy. The CI–PT approach tested here on the Pu II ion can be generally used to calculate properties of many complex atoms, including U I that can find application in fundamental and applied science.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Conceptual Spacer Design for the ATR GEN I Target for Pu-238 Production in the Advanced Test Reactor at Idaho National Laboratory

The initial target design used for Pu-238 production at Idaho National Laboratory was designed by Oak Ridge National Laboratory to optimize the production of Pu-238 in the High Flux Isotope Reactor (HFIR) and are referred to as HFIR GEN II targets. To take advantage of the Advanced Test Reactor’s (ATR) taller active core region a redesign of the HFIR GEN II targets was needed. It was proposed to stack two HFIR GEN II targets nose to nose about the core center line; however, this resulted in excessive neutron and photon heating in the pellets located in the center. This peak heating was not desirable so three alternative designs were investigated for the ATR GEN I targets. The python-based code, MCNP to ORIGEN2 in Python (MOPY), was used to calculate the heating rates after 40 days of irradiation to capture the effects of each configuration. The purpose of this paper is to document the details of these conceptual design calculations and comparisons for the ATR GEN I targets.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2024

Conceptual Spacer Design for the ATR GEN I Target for Pu-238 Production in the Advanced Test Reactor at Idaho National Laboratory

The initial target design used for Pu-238 production at Idaho National Laboratory was designed by Oak Ridge National Laboratory to optimize the production of Pu-238 in the High Flux Isotope Reactor (HFIR) and are referred to as HFIR GEN II targets. To take advantage of the Advanced Test Reactor’s (ATR) taller active core region a redesign of the HFIR GEN II targets was needed. It was proposed to stack two HFIR GEN II targets nose to nose about the core center line; however, this resulted in excessive neutron and photon heating in the pellets located in the center. This peak heating was not desirable so three alternative designs were investigated for the ATR GEN I targets. The python-based code, MCNP to ORIGEN2 in Python (MOPY), was used to calculate the heating rates after 40 days of irradiation to capture the effects of each configuration. The purpose of this paper is to document the details of these conceptual design calculations and comparisons for the ATR GEN I targets.

07 ISOTOPE AND RADIATION SOURCES↗