Howard Hall | University of Tennessee Knoxville (original) (raw)

Papers by Howard Hall

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Apr 24, 2018

Journal of Radioanalytical and Nuclear Chemistry, Jul 8, 2017

No nuclear weapon has ever been detonated in a United States city. However, this also means the n... more No nuclear weapon has ever been detonated in a United States city. However, this also means the nuclear forensic community has no actual debris from which to develop analytical methods for source attribution, making the development of surrogate nuclear debris a vital undertaking. Moreover, the development of marine-urban debris presents an unusual challenge because unlike soil and urban structures, which remain compositionally consistent, the elemental composition of harbor and port waters fluctuates considerably due to natural phenomenon and human activity. Additionally, marine vessel composition and cargo can vary dramatically. While early US nuclear tests were carried out in shallow-water coastal areas, they did not represent the marine-urban environments of large cities and any residual debris will be ill suited for the development of modern forensic techniques. Given these technical complexities, it is critical to understand the environmental variations in order to develop realistic surrogate nuclear marineurban debris. This project seeks to build a robust model for the New York/New Jersey harbor, the Port of Houston, and the Long Beach/Los Angeles harbor that statistically define the elemental composition of vaporized debris for follow-on neutron-activation and debris formation analysis. Analysis of these neutron and fractionation effects will support the development of unique surrogate debris samples that mimic the elemental content of actual nuclear debris from a marineurban detonation. These samples can then be utilized for the development of the analytical methods for post-detonation analysis and attribution. v

Physical review applied, Sep 15, 2017

Eu 2+ doped alkali or alkali earth iodide scintillators with energy resolutions ≤3% at 662 keV pr... more Eu 2+ doped alkali or alkali earth iodide scintillators with energy resolutions ≤3% at 662 keV promise the excellent discrimination ability for radioactive isotopes required for homeland security and nuclear non-proliferation applications. To extend their applications to X-ray imaging, such as computed tomography scans, the intense afterglow which delays the response time of such materials is an obstacle that needs to be overcome. However, a clear understanding of the origin of the afterglow and feasible solutions is still lacking. In this work, we present a combined experimental and theoretical combined investigation of the physical insights of codoping-based defect engineering which can reduce the afterglow effectively in KCaI 3 :Eu 2+ single crystal scintillators. We illustrate that Sc 3+ codoping greatly suppresses the afterglow, whereas Y 3+ , Gd 3+ , or La 3+ codoping enhances the afterglow. Meanwhile, a light yield of 57,000 photons/MeV and an energy resolution of 3.4% at 662 keV can be maintained with the appropriate concentration of Sc 3+ codoping, which makes the material promising for medical imaging applications. Through our thermoluminescence techniques and density functional theory calculations, we are able to identify the defect structures and understand the mechanism by which codoping affects the scintillation performance of KCaI 3 :Eu 2+ crystals. The proposed defect-engineering strategy was further validated by achieving afterglow suppression in Mg 2+ codoped KCaI 3 :Eu 2+ single crystals.

Transactions of the American Nuclear Society, 2016

Journal of Applied Clinical Medical Physics, Dec 1, 2022

This editorial pertains to the current status and future outlook of selected professions involved... more This editorial pertains to the current status and future outlook of selected professions involved in radiation protection, summarizing the methods used, and presenting selected key results and recommendations. The team of authors includes members from the professions of health physics, medical physics, medicine, nuclear engineering, radiation biology, and radiation and nuclear chemistry. Chapters 2 through 7 of this special issue review the characteristics of each profession and its workforce, as well as recommending actions to ensure their future adequacy to meet the nation's needs.

Journal of Radioanalytical and Nuclear Chemistry, Oct 7, 2017

A method for producing realistic surrogate debris characteristic of those that would be expected ... more A method for producing realistic surrogate debris characteristic of those that would be expected to be found following a nuclear detonation in an urban environment is tested. The melt glass samples are benchmarked against synthetic trinitite via electron microscopy and X-ray diffractometry analysis. The surrogates produced proved to be similar to trinitite and synthetic nuclear melt glass, but showed differences indicative of the calculated precursor matrix for each city modeled. The synthetic debris produced may serve as a tool to advance and validate existing rapid nuclear forensic analysis methods.

Journal of Applied Clinical Medical Physics, Dec 1, 2022

Journal of Visualized Experiments, Jan 4, 2016

Transactions of the American Nuclear Society, 2016

This paper presents a study of the 7 rays from the electron capture decay of 3.63 d looPd. Single... more This paper presents a study of the 7 rays from the electron capture decay of 3.63 d looPd. Singles and coincidence measurements provided an accurate determination of 7-ray intensities and an improved knowledge of the 100Rh level scheme. Experimental evidence supports excitation of levels in lOORh at 86-, 136and 154 keY, not previously reported from the decay of 100Pd .

Nuclear Instruments and Methods in Physics Research, Jun 1, 1992

Journal of Radioanalytical and Nuclear Chemistry, 2020

Cu metal, surrogate for metallic actinide materials, was subject to accelerated aging through the... more Cu metal, surrogate for metallic actinide materials, was subject to accelerated aging through thermal treatment. A multiphase oxide-layer (Cu 2 O, CuO) was detected, varying with temperature (250-400 °C) and aging time (1-3.5 h). Isotope ratio mass spectrometry revealed temperature-dependent isotopic fractionation of O, evidenced by the enrichment of Cu oxide in 16 O isotopes with increasing temperature. Isotopic fractionation occurred initially with atmospheric O, and later through exchange with water vapor. Raman spectra contributed insight on phase fraction and local bonding of Cu oxides. O isotopes could serve as a useful tracer for studying oxide layer growth from aging metallic systems.

Applied Optics, 2017

A hand-held device for laser-induced breakdown spectroscopy has been investigated for the determi... more A hand-held device for laser-induced breakdown spectroscopy has been investigated for the determination of uranyl fluoride surface contamination. This research demonstrates the ability to successfully detect uranium on surfaces when using a low resolving power (λ∕Δλ 4000) spectrograph, with a 5 mJ energy per 1 ns pulsed laser radiation, available as a commercially packaged hand-held system. Sand/uranyl fluoride mixtures are prepared to simulate residue likely encountered during decontamination efforts at facilities that handle uranium hexafluoride. Detection limits are described for four uranium lines with one revealing the capability to detect uranium at a level of 250 parts per million. Advantages of the studied compact device include that location specific information can be obtained on-site to augment contamination identification.

International Journal of Modern Physics: Conference Series, 2018

The ability to determine the origin of a specific spent-fuel sample from a commercial nuclear rea... more The ability to determine the origin of a specific spent-fuel sample from a commercial nuclear reactor was studied using the Origen-S simulation code by calculating the plutonium and uranium isotopic concentration data for a range of nuclear power reactors. This range of reactors is based on a typical Westinghouse PWR fuel assembly with a fuel type of W17 X 17, having individual operating histories. Isotopic ratios of plutonium in nuclear reactors during the fuel-cycle period provide information on how the plutonium grows into the fuel as a function of burnup, as well as its attractiveness to proliferators. Using the results from the calculation of uranium and plutonium isotopic ratios, the origin of each spent-fuel assembly for a particular reactor can be predicted and documented for a future nuclear forensics reference database.

ACS Omega, 2018

Knowledge-based design of extracting agents for selective binding of actinides is essential in st... more Knowledge-based design of extracting agents for selective binding of actinides is essential in stockpile stewardship, environmental remediation, separations, and nuclear fuel disposal. Robust computational protocols are critical for in depth understanding of structural properties and to further advance the design of selective ligands. In particular, rapid radiochemical separations require predictive capabilities for binding in the gas phase. This study focuses on gasphase binding preferences of cyclic imide dioximes to uranyl, neptunyl, plutonyl, and americyl. Structural properties, electron withdrawing effects, and their effects on binding preferences are studied with natural bond-order population analysis. The aromatic amidoximes are found to have a larger electron-donation effect than the aliphatic amidoximes. It is also found that plutonyl is more electron withdrawing than uranyl, neptunyl, and americyl when bound to the cyclic imide dioximes studied.

International Journal of Mass Spectrometry, 2017

Investigations of enhanced sample utilization in thermal ionization mass spectrometry (TIMS) usin... more Investigations of enhanced sample utilization in thermal ionization mass spectrometry (TIMS) using porous ion emitter (PIE) techniques for the analyses of trace quantities of americium and plutonium were performed. Repeat ionization efficiency (i.e., the ratio of ions detected to atoms loaded on the filament) measurements were conducted on sample sizes ranging from 10-100 pg for americium and 1-100 pg for plutonium using PIE and traditional (i.e., a single, zone-refined rhenium, flat filament ribbon with a carbon ionization enhancer) TIMS filament sources. When compared to traditional filaments, PIEs exhibited an average boost in ionization efficiency of ∼550 % for plutonium and ∼1100 % for americium. A maximum average efficiency of 1.09 % was observed at a 1 pg plutonium sample loading using PIEs. Supplementary trials were conducted using newly developed platinum PIEs to analyze 10 pg mass loadings of plutonium. Platinum PIEs exhibited an additional ∼134 % boost in ion yield over standard PIEs and ∼736 % over traditional filaments at the same sample loading level.

ract, 1992

Previous studies of the halide complex formation of element 105 and its anion exchange with triis... more Previous studies of the halide complex formation of element 105 and its anion exchange with triisooctyl amine (TIOA) were continued. The experiments were performed on a one-minute time scale with the computer-controlled liquid chromatography system ARCA II on a mixture of 34-s 262 Ha and 27-s 263 Ha produced in the 249 Bk(18 0,5n) and 249 Bk(18 0,4n) reactions at a beam energy of 99 MeV. The Ha isotopes were detected by measuring the spontaneous fission and α-activities associated with their decay, and the α-decays of their daughters, 4-s 258 Lr, and 6-s 259 Lr. Time-correlated pairs of parent and daughter α-particles were also registered. 262,263 Ha was absorbed on the TIOA columns from either 12 M HCl/0.01 M HF or 10 M HCl, and was subsequently eluted in 0.5 M HCl/0.01 M HF like its homolog niobium, and the pseudohomolog protactinium, and unlike the closest homolog, tantalum, which remains in the amine phase under these conditions. The effluent was divided into an early Pa fraction and a subsequent Nb fraction. By varying the cut between the Pa fraction and the Nb fraction in rough steps, it was shown that the elution of element 105 occurs closer to the Pa elution position, i.e., earlier than the elution of Nb. These results confirm the non-tantalum like behavior of element 105 in 0.5 M HCl/0.01 M HF, and corroborate previously suggested structural differences between the halide complexes of element 105, niobium, and protactinium, on the one hand, and those of tantalum on the other hand.

Physical Review C, 1992

Excitation functions have been measured for production of isotopes of Th through Fm in bombardmen... more Excitation functions have been measured for production of isotopes of Th through Fm in bombardments of Cm with 231to 323-MeV Ca ions and for the production of isotopes of Th through Cm in bombardments of ' Cm with 230to 291-MeV Ca ions, respectively, using radiochemical methods. Upper production cross section limits were established for nuclides that were not positively detected. The experimental data were compared with the results of previous reaction studies in the systems Ca+' 'Cm and 'Ca+ 'Cm. The half-widths of the Gaussian isotopic distributions were about 2.5 mass numbers for above-target elements and 5 to 5.5 mass numbers for below-target elements in all three systems. The majority of the cross section for the production of above-target nuclides was assigned to predominantly quasielastic reactions, whereas below-target nuclides were formed in deeply inelastic and asymmetric quasifission reactions. The maxima of the isotopic distributions were shown by others to closely follow the minimum of the potential energy surface in experiments with 'Ca, whereas in reactions with Ca and Ca we found that a transfer of 4 to 5 protons in either direction was required to reach the minimum in potential energy. The different neutron numbers of Ca, Ca, and 'Ca are only partly reflected in the target-like reaction products. Based on a simple model, excitation energies and the maxima of the excitation functions were calculated and compared with the actual data. The yields for production of the below-target elements Th, U, and Pu were found to be two orders of magnitude smaller in the reaction of Ca with Cm than with Ca. The differences for production of above-target elements were largest between the reactions of Ca and 'Ca ions with Cm. Differences in belowtarget yields have been attributed either to losses of reaction products due to prompt fission, and/or to dynamic effects due to fusion hindrance. The data for above-target elements seem to confirm the presence of a strong isospin driving force, which in combination with favorable reaction energies results in surprisingly high yields in reactions with Ca projectiles.

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Apr 24, 2018

Journal of Radioanalytical and Nuclear Chemistry, Jul 8, 2017

No nuclear weapon has ever been detonated in a United States city. However, this also means the n... more No nuclear weapon has ever been detonated in a United States city. However, this also means the nuclear forensic community has no actual debris from which to develop analytical methods for source attribution, making the development of surrogate nuclear debris a vital undertaking. Moreover, the development of marine-urban debris presents an unusual challenge because unlike soil and urban structures, which remain compositionally consistent, the elemental composition of harbor and port waters fluctuates considerably due to natural phenomenon and human activity. Additionally, marine vessel composition and cargo can vary dramatically. While early US nuclear tests were carried out in shallow-water coastal areas, they did not represent the marine-urban environments of large cities and any residual debris will be ill suited for the development of modern forensic techniques. Given these technical complexities, it is critical to understand the environmental variations in order to develop realistic surrogate nuclear marineurban debris. This project seeks to build a robust model for the New York/New Jersey harbor, the Port of Houston, and the Long Beach/Los Angeles harbor that statistically define the elemental composition of vaporized debris for follow-on neutron-activation and debris formation analysis. Analysis of these neutron and fractionation effects will support the development of unique surrogate debris samples that mimic the elemental content of actual nuclear debris from a marineurban detonation. These samples can then be utilized for the development of the analytical methods for post-detonation analysis and attribution. v

Physical review applied, Sep 15, 2017

Eu 2+ doped alkali or alkali earth iodide scintillators with energy resolutions ≤3% at 662 keV pr... more Eu 2+ doped alkali or alkali earth iodide scintillators with energy resolutions ≤3% at 662 keV promise the excellent discrimination ability for radioactive isotopes required for homeland security and nuclear non-proliferation applications. To extend their applications to X-ray imaging, such as computed tomography scans, the intense afterglow which delays the response time of such materials is an obstacle that needs to be overcome. However, a clear understanding of the origin of the afterglow and feasible solutions is still lacking. In this work, we present a combined experimental and theoretical combined investigation of the physical insights of codoping-based defect engineering which can reduce the afterglow effectively in KCaI 3 :Eu 2+ single crystal scintillators. We illustrate that Sc 3+ codoping greatly suppresses the afterglow, whereas Y 3+ , Gd 3+ , or La 3+ codoping enhances the afterglow. Meanwhile, a light yield of 57,000 photons/MeV and an energy resolution of 3.4% at 662 keV can be maintained with the appropriate concentration of Sc 3+ codoping, which makes the material promising for medical imaging applications. Through our thermoluminescence techniques and density functional theory calculations, we are able to identify the defect structures and understand the mechanism by which codoping affects the scintillation performance of KCaI 3 :Eu 2+ crystals. The proposed defect-engineering strategy was further validated by achieving afterglow suppression in Mg 2+ codoped KCaI 3 :Eu 2+ single crystals.

Transactions of the American Nuclear Society, 2016

Journal of Applied Clinical Medical Physics, Dec 1, 2022

This editorial pertains to the current status and future outlook of selected professions involved... more This editorial pertains to the current status and future outlook of selected professions involved in radiation protection, summarizing the methods used, and presenting selected key results and recommendations. The team of authors includes members from the professions of health physics, medical physics, medicine, nuclear engineering, radiation biology, and radiation and nuclear chemistry. Chapters 2 through 7 of this special issue review the characteristics of each profession and its workforce, as well as recommending actions to ensure their future adequacy to meet the nation's needs.

Journal of Radioanalytical and Nuclear Chemistry, Oct 7, 2017

A method for producing realistic surrogate debris characteristic of those that would be expected ... more A method for producing realistic surrogate debris characteristic of those that would be expected to be found following a nuclear detonation in an urban environment is tested. The melt glass samples are benchmarked against synthetic trinitite via electron microscopy and X-ray diffractometry analysis. The surrogates produced proved to be similar to trinitite and synthetic nuclear melt glass, but showed differences indicative of the calculated precursor matrix for each city modeled. The synthetic debris produced may serve as a tool to advance and validate existing rapid nuclear forensic analysis methods.

Journal of Applied Clinical Medical Physics, Dec 1, 2022

Journal of Visualized Experiments, Jan 4, 2016

Transactions of the American Nuclear Society, 2016

This paper presents a study of the 7 rays from the electron capture decay of 3.63 d looPd. Single... more This paper presents a study of the 7 rays from the electron capture decay of 3.63 d looPd. Singles and coincidence measurements provided an accurate determination of 7-ray intensities and an improved knowledge of the 100Rh level scheme. Experimental evidence supports excitation of levels in lOORh at 86-, 136and 154 keY, not previously reported from the decay of 100Pd .

Nuclear Instruments and Methods in Physics Research, Jun 1, 1992

Journal of Radioanalytical and Nuclear Chemistry, 2020

Cu metal, surrogate for metallic actinide materials, was subject to accelerated aging through the... more Cu metal, surrogate for metallic actinide materials, was subject to accelerated aging through thermal treatment. A multiphase oxide-layer (Cu 2 O, CuO) was detected, varying with temperature (250-400 °C) and aging time (1-3.5 h). Isotope ratio mass spectrometry revealed temperature-dependent isotopic fractionation of O, evidenced by the enrichment of Cu oxide in 16 O isotopes with increasing temperature. Isotopic fractionation occurred initially with atmospheric O, and later through exchange with water vapor. Raman spectra contributed insight on phase fraction and local bonding of Cu oxides. O isotopes could serve as a useful tracer for studying oxide layer growth from aging metallic systems.

Applied Optics, 2017

A hand-held device for laser-induced breakdown spectroscopy has been investigated for the determi... more A hand-held device for laser-induced breakdown spectroscopy has been investigated for the determination of uranyl fluoride surface contamination. This research demonstrates the ability to successfully detect uranium on surfaces when using a low resolving power (λ∕Δλ 4000) spectrograph, with a 5 mJ energy per 1 ns pulsed laser radiation, available as a commercially packaged hand-held system. Sand/uranyl fluoride mixtures are prepared to simulate residue likely encountered during decontamination efforts at facilities that handle uranium hexafluoride. Detection limits are described for four uranium lines with one revealing the capability to detect uranium at a level of 250 parts per million. Advantages of the studied compact device include that location specific information can be obtained on-site to augment contamination identification.

International Journal of Modern Physics: Conference Series, 2018

The ability to determine the origin of a specific spent-fuel sample from a commercial nuclear rea... more The ability to determine the origin of a specific spent-fuel sample from a commercial nuclear reactor was studied using the Origen-S simulation code by calculating the plutonium and uranium isotopic concentration data for a range of nuclear power reactors. This range of reactors is based on a typical Westinghouse PWR fuel assembly with a fuel type of W17 X 17, having individual operating histories. Isotopic ratios of plutonium in nuclear reactors during the fuel-cycle period provide information on how the plutonium grows into the fuel as a function of burnup, as well as its attractiveness to proliferators. Using the results from the calculation of uranium and plutonium isotopic ratios, the origin of each spent-fuel assembly for a particular reactor can be predicted and documented for a future nuclear forensics reference database.

ACS Omega, 2018

Knowledge-based design of extracting agents for selective binding of actinides is essential in st... more Knowledge-based design of extracting agents for selective binding of actinides is essential in stockpile stewardship, environmental remediation, separations, and nuclear fuel disposal. Robust computational protocols are critical for in depth understanding of structural properties and to further advance the design of selective ligands. In particular, rapid radiochemical separations require predictive capabilities for binding in the gas phase. This study focuses on gasphase binding preferences of cyclic imide dioximes to uranyl, neptunyl, plutonyl, and americyl. Structural properties, electron withdrawing effects, and their effects on binding preferences are studied with natural bond-order population analysis. The aromatic amidoximes are found to have a larger electron-donation effect than the aliphatic amidoximes. It is also found that plutonyl is more electron withdrawing than uranyl, neptunyl, and americyl when bound to the cyclic imide dioximes studied.

International Journal of Mass Spectrometry, 2017

Investigations of enhanced sample utilization in thermal ionization mass spectrometry (TIMS) usin... more Investigations of enhanced sample utilization in thermal ionization mass spectrometry (TIMS) using porous ion emitter (PIE) techniques for the analyses of trace quantities of americium and plutonium were performed. Repeat ionization efficiency (i.e., the ratio of ions detected to atoms loaded on the filament) measurements were conducted on sample sizes ranging from 10-100 pg for americium and 1-100 pg for plutonium using PIE and traditional (i.e., a single, zone-refined rhenium, flat filament ribbon with a carbon ionization enhancer) TIMS filament sources. When compared to traditional filaments, PIEs exhibited an average boost in ionization efficiency of ∼550 % for plutonium and ∼1100 % for americium. A maximum average efficiency of 1.09 % was observed at a 1 pg plutonium sample loading using PIEs. Supplementary trials were conducted using newly developed platinum PIEs to analyze 10 pg mass loadings of plutonium. Platinum PIEs exhibited an additional ∼134 % boost in ion yield over standard PIEs and ∼736 % over traditional filaments at the same sample loading level.

ract, 1992

Previous studies of the halide complex formation of element 105 and its anion exchange with triis... more Previous studies of the halide complex formation of element 105 and its anion exchange with triisooctyl amine (TIOA) were continued. The experiments were performed on a one-minute time scale with the computer-controlled liquid chromatography system ARCA II on a mixture of 34-s 262 Ha and 27-s 263 Ha produced in the 249 Bk(18 0,5n) and 249 Bk(18 0,4n) reactions at a beam energy of 99 MeV. The Ha isotopes were detected by measuring the spontaneous fission and α-activities associated with their decay, and the α-decays of their daughters, 4-s 258 Lr, and 6-s 259 Lr. Time-correlated pairs of parent and daughter α-particles were also registered. 262,263 Ha was absorbed on the TIOA columns from either 12 M HCl/0.01 M HF or 10 M HCl, and was subsequently eluted in 0.5 M HCl/0.01 M HF like its homolog niobium, and the pseudohomolog protactinium, and unlike the closest homolog, tantalum, which remains in the amine phase under these conditions. The effluent was divided into an early Pa fraction and a subsequent Nb fraction. By varying the cut between the Pa fraction and the Nb fraction in rough steps, it was shown that the elution of element 105 occurs closer to the Pa elution position, i.e., earlier than the elution of Nb. These results confirm the non-tantalum like behavior of element 105 in 0.5 M HCl/0.01 M HF, and corroborate previously suggested structural differences between the halide complexes of element 105, niobium, and protactinium, on the one hand, and those of tantalum on the other hand.

Physical Review C, 1992

Excitation functions have been measured for production of isotopes of Th through Fm in bombardmen... more Excitation functions have been measured for production of isotopes of Th through Fm in bombardments of Cm with 231to 323-MeV Ca ions and for the production of isotopes of Th through Cm in bombardments of ' Cm with 230to 291-MeV Ca ions, respectively, using radiochemical methods. Upper production cross section limits were established for nuclides that were not positively detected. The experimental data were compared with the results of previous reaction studies in the systems Ca+' 'Cm and 'Ca+ 'Cm. The half-widths of the Gaussian isotopic distributions were about 2.5 mass numbers for above-target elements and 5 to 5.5 mass numbers for below-target elements in all three systems. The majority of the cross section for the production of above-target nuclides was assigned to predominantly quasielastic reactions, whereas below-target nuclides were formed in deeply inelastic and asymmetric quasifission reactions. The maxima of the isotopic distributions were shown by others to closely follow the minimum of the potential energy surface in experiments with 'Ca, whereas in reactions with Ca and Ca we found that a transfer of 4 to 5 protons in either direction was required to reach the minimum in potential energy. The different neutron numbers of Ca, Ca, and 'Ca are only partly reflected in the target-like reaction products. Based on a simple model, excitation energies and the maxima of the excitation functions were calculated and compared with the actual data. The yields for production of the below-target elements Th, U, and Pu were found to be two orders of magnitude smaller in the reaction of Ca with Cm than with Ca. The differences for production of above-target elements were largest between the reactions of Ca and 'Ca ions with Cm. Differences in belowtarget yields have been attributed either to losses of reaction products due to prompt fission, and/or to dynamic effects due to fusion hindrance. The data for above-target elements seem to confirm the presence of a strong isospin driving force, which in combination with favorable reaction energies results in surprisingly high yields in reactions with Ca projectiles.