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DOE OSTI2024

Titanium Wire Arc Additive Manufacturing Inert Enclosure and Material Handling Safety Considerations

Wire arc additive manufacturing (WAAM) via metal inert gas (MIG)/gas metal arc welding (GMAW) is a viable option for fabrication of large-scale titanium parts; however, it introduces new safety hazards associated with both the material and the additional system hardware required for the process. Localized gas shielding of the weld arc via standard GMAW torch is inadequate for titanium due to its affinity for oxygen; thereby requiring the use of an inert enclosure to protect the weld from entraining oxygen. The use of the inert enclosure presents potential safety hazards such as operator asphyxiation and brings up discussion of confined space considerations. In addition, the titanium welding process creates pyrophoric titanium soot residue around the deposit, which can undergo deflagration during part cleaning and part removal. This paper provides an overview of the titanium WAAM process along with safety considerations for the design and operation of the inert enclosure as well as functional solutions for the safe handling of the titanium soot by-product.

Walters, Alex↗

DOE OSTI2023

Drying of Spent Nuclear Fuel: Considerations and Examples

A recently revised American Society for Testing and Materials consensus standard guide for drying of spent nuclear fuel (SNF) provides considerations and guidance for preparing SNF for its safe storage in a sealed dry storage system. The standard discusses (1) needs for drying, (2) techniques to dry, and (3) demonstration of adequate dryness. No specific approach is prescribed since the effective techniques and needs for drying depend on the specifics of the fuel and dry storage system. Here, this paper discusses these topics using examples for both Zr-alloy-clad commercial SNF and for aluminum-alloy-clad research reactor SNF. Residual water can include free water (liquid and/or vapor), physisorbed water bound to internal surfaces, and chemisorbed water incorporated into surface films, such as (oxy)hydroxides. The potential impacts of these residual waters are corrosion/oxidation, radiolytic breakdown into gaseous and/or reactive species, and canister pressurization. For commercial SNF, inadvertent free water, even up to large amounts (e.g., 10+ mol), is not predicted to cause adverse corrosion degradation, except possible fuel oxidation for breached SNF. For aluminum-clad SNF, the production of radiolytic hydrogen with contribution from the chemisorbed water in its hydrated oxides is a primary consideration. For both SNF systems, canister pressurization is predicted to be well within the canister design, and flammability would not pose a safety concern using an oxygen limit of 5 vol % criterion. (Flammability control can be achieved by limiting either hydrogen or oxygen, and an oxygen limit is expected to be easier to meet in the presence of radiolytic H 2 generation.) The two primary technologies for SNF drying, vacuum drying and forced-gas dehydration, are described herein, and drying tests and campaigns using these methods are cited. Dryness criteria and the methods used to detect and measure residual (free) water are also discussed.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

NASA NTRS1997

An overview: recycling nutrients from crop residues for space applications

Without some form of regenerative life support system, long duration space habitation or travel will be limited severely by the prohibitive costs of resupplying air, water, and food from Earth. Components under consideration for inclusion in a regenerative life support system are based on either physicochemical or biological processes. Physicochemical systems would use filtration and elemental phase changes to convert waste materials into usable products, while biological systems would use higher plants and bioreactors to supply crew needs. Neither a purely biological nor strictly a physicochemical approach can supply all crew needs, thus, the best each approach can offer will be combined into a hybrid regenerative life support system. Researchers at Kennedy Space Center (KSC) Advanced Life Support Breadboard Project have taken the lead on bioregenerative aspects of space life support. The major focus has been on utilization of higher plants for production of food, oxygen, and clean water. However, a key to any regenerative life support system is recycling and recovery of resources (wastes). In keeping with the emphasis at KSC on bioregenerative systems and with the focus on plants, this paper focuses on research with biologically-based options for resource recovery from inedible crop residues.

Biomass↗

NASA NTRS1977

Development and testing of a wet oxidation waste processing system

The wet oxidation process is considered as a potential treatment method for wastes aboard manned spacecraft for these reasons: (1) Fecal and urine wastes are processed to sterile water and CO2 gas. However, the water requires post-treatment to remove salts and odor; (2) the residual ash is negligible in quantity, sterile and easily collected; and (3) the product CO2 gas can be processed through a reduction step to aid in material balance if needed. Reaction of waste materials with oxygen at elevated temperature and pressure also produces some nitrous oxide, as well as trace amounts of a few other gases.

Weitzmann, A. L.↗

DOE OSTI2026

Measuring the neutrino-oxygen neutral current quasielastic cross section using the accelerator neutrino neutron interaction experiment

The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) is a 26-ton gadolinium-doped water Cherenkov detector located on-axis to Fermilab’s Booster Neutrino Beam (BNB). ANNIE is uniquely positioned to perform high-statistics measurements of neutrino-nucleus interactions in water, benefiting from a large neutrino flux due to a short (100-meter) baseline. A central focus of ANNIE’s physics program is the measurement of both charged current (CC) and neutral current (NC) cross sections on water, including neutral current quasielastic (NCQE) and CC-inclusive channels. The NCQE measurement is particularly critical for constraining uncertainties in rare-event searches such as the Diffuse Supernova Neutrino Background (DSNB), where atmospheric $\nu$NCQE interactions constitute a significant and poorly constrained background. This dissertation presents a measurement of the flux-averaged neutrino-oxygen neutral current quasielastic ($\nu$NCQE) cross section using $2.573 \times 10^{20}$~POT of BNB exposure from the 2022 and 2023 beam years. The $\nu$NCQE interaction is identified through the primary $\gamma$-rays produced by nuclear de-excitation of the residual $^{15}$N$^*$ or $^{15}$O$^*$ nucleus following nucleon knockout from $^{16}$O. A dedicated Monte Carlo (MC) re-tuning campaign was conducted using an americium-beryllium (AmBe) calibration source, Michel electrons from stopped muons, and throughgoing dirt muons originating upstream of the detector. This multi-sample approach provided a wide-ranging $\mathcal{O}(\text{MeV})$--$\mathcal{O}(\text{GeV})$ dataset for tuning the simulated detector response, which was subsequently validated against AmBe neutron and Michel electron data for use in the $\nu$NCQE analysis. A dedicated laser calibration campaign was carried out to reduce timing uncertainties across the PMT system, enabling reconstruction of the BNB bunch substructure with sufficient resolution to serve as a background rejection tool. By selecting events in-time with individual neutrino bunches, beam-correlated $\nu$NCQE events are separated from diffuse and accelerator-induced backgrounds, notably skyshine neutrons and externally-originating events, that would otherwise dominate traditional charge-based selections within a small-scale, surface-level, short-baseline detector. A data-driven estimation of the skyshine neutron and external background rates was performed and incorporated into the systematic uncertainty budget. The flux-averaged $\nu$NCQE cross section on oxygen is measured to be $1.57 \pm 0.06\,(\text{stat.})$ $^{+0.91}_{-0.67}\,(\text{syst.})$ $\times 10^{-38}\ \text{cm}^{2}$. A full systematic budget is constructed by propagating uncertainties in the secondary hadronic interaction modeling, background cross section normalizations, detector response, neutrino flux, and the primary $\gamma$-ray emission probabilities from oxygen nuclear de-excitation. An idealized de-excitation model, constructed from existing measurements in the literature is developed to benchmark the predictions of the \textsc{GENIE} event generator. A comparison reveals that \textsc{GENIE} systematically overpredicts the primary $\gamma$-ray emission probability from oxygen de-excitation by a factor of $1.49\times$ for $E_\gamma > 6$~MeV and $3.07\times$ in the $3$--$6$~MeV band. This comparison motivates the dominant systematic uncertainty in this analysis, where a conservative uncertainty of $^{+39.9\%}_{-0\%}$ on the primary $\gamma$-ray signal prediction is assigned. The ANNIE result is consistent with and complementary to existing flux-averaged $\nu$NCQE cross section measurements from T2K and Super-Kamiokande, providing an independent measurement with a different detector, neutrino beam, and analysis methodology. Looking ahead, an upgrade to the ANNIE DAQ infrastructure enabling continuous extended readout will allow a complementary $\nu$NCQE neutron multiplicity measurement, directly relevant to constraining the NCQE background in DSNB searches, competitive with the recent T2K measurement at SK-Gd. The planned Super-SANDI upgrade, deploying a large Water-based Liquid Scintillator (WbLS) volume, will further extend ANNIE's reach to hadronic final states and exclusive NC channels, and enable joint measurements with liquid argon detectors sharing the BNB beamline ahead of DUNE and Hyper-Kamiokande.

Doran, Steven [Iowa State U.]↗

DOE OSTI2020

Distonic radical anion species in cysteine oxidation processes

Oxidation of cysteine residues constitutes an important regulatory mechanism in the function of biological systems. Much of this behavior is controlled by the specific chemical properties of the thiol side-chain group, where reac-tions with reactive oxygen species take place. Herein, we in-vestigated the entire cysteine oxidation cycle Cys-SH ? Cys-SOnH (n = 1, 2, 3) using cryogenic negative ion photoelectron spectroscopy and quantum-chemical calculations. The conven-tional view on the first reversible oxidation step (n = 1) is as-sociated with sulfinate species. Yet our results indicate that an alternative option exists in the form of novel distonic radical anion •OS-CH2CH(NH2)-COO- with an unpaired electron on the thiol group and excess negative charge on the carboxylate. Higher order oxidation states (n = 2, 3) are thought to be asso-ciated with irreversible oxidative damage, and our results show that excess negative charge in those cases migrates to -SOn- group. Furthermore, these species are stable towards 1e oxidation, as opposed to the n = 1 case that undergoes intra-molecular proton transfer. The molecular level insights report-ed in this work provide direct spectroscopic evidences towards unique chemical versatility of Cys-sulfenic acid (Cys-SOH) in post-translational modifications of protein systems. This research was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences (X.-B. W. and M. V.) and was performed at the EMSL, a national scientific user facility sponsored by DOE's Office of Biological and Environmental Research and located at the Pacific Northwest National Laboratory. Z. B. Q. acknowledges additional support from the National Natural Science Foundation of China (Grant No. 21873003 and 21503003) and the Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund (the second phase) (Grant No. U1501501) and Super Computation of Shenzhen.

Qin, Zhengbo↗

DOE OSTI2021

Structure and assembly of the diiron cofactor in the heme-oxygenase–like domain of the N-nitrosourea–producing enzyme SznF

In biosynthesis of the pancreatic cancer drug streptozotocin, the tridomain nonheme-iron oxygenase SznF hydroxylates N δ and N ω ' of N ω -methyl- L -arginine before oxidatively rearranging the triply modified guanidine to the N-methyl-N-nitrosourea pharmacophore. A previously published structure visualized the monoiron cofactor in the enzyme’s C-terminal cupin domain, which promotes the final rearrangement, but exhibited disorder and minimal metal occupancy in the site of the proposed diiron cofactor in the N-hydroxylating heme-oxygenase–like (HO-like) central domain. We leveraged our recent observation that the N-oxygenating µ-peroxodiiron(III/III) intermediate can form in the HO-like domain after the apo protein self-assembles its diiron(II/II) cofactor to solve structures of SznF with both of its iron cofactors bound. These structures of a biochemically validated member of the emerging heme-oxygenase–like diiron oxidase and oxygenase (HDO) superfamily with intact diiron cofactor reveal both the large-scale conformational change required to assemble the O 2 -reactive Fe 2 (II/II) complex and the structural basis for cofactor instability—a trait shared by the other validated HDOs. During cofactor (dis)assembly, a ligand-harboring core helix dynamically (un)folds. The diiron cofactor also coordinates an unanticipated Glu ligand contributed by an auxiliary helix implicated in substrate binding by docking and molecular dynamics simulations. The additional carboxylate ligand is conserved in another N-oxygenating HDO but not in two HDOs that cleave carbon–hydrogen and carbon–carbon bonds to install olefins. Among ~9,600 sequences identified bioinformatically as members of the emerging HDO superfamily, ~25% conserve this additional carboxylate residue and are thus tentatively assigned as N-oxygenases.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2022

Stellar Populations in type Ia supernova host galaxies at intermediate-high redshift: Star formation and metallicity enrichment histories

ABSTRACT We present a summary of our project that studies galaxies hosting type Ia supernova (SN Ia) at different redshifts. We present Gran Telescopio de Canarias (GTC) optical spectroscopy of six SN Ia host galaxies at redshift z ∼ 0.4–0.5. They are joined to a set of SN Ia host galaxies at intermediate-high redshift, which include galaxies from surveys SDSS and COSMOS. The final sample, after a selection of galaxy spectra in terms of signal-to-noise and other characteristics, consists of 680 galaxies with redshift in the range 0.04 < z < 1. We perform an inverse stellar population synthesis with the code fado to estimate the star formation and enrichment histories of this set of galaxies, simultaneously obtaining their mean stellar age and metallicity and stellar mass. After analysing the correlations among these characteristics, we look for possible dependencies of the Hubble diagram residuals and supernova features (luminosity, colour and strength parameter) on these stellar parameters. We find that the Hubble residuals show a clear dependence on the stellar metallicity weighted by mass with a slope of −0.061 mag dex−1, when represented in logarithmic scale, log 〈ZM/Z⊙〉. This result supports our previous findings obtained from gas oxygen abundances for local and SDSS-survey galaxies. Comparing with other works from the literature that also use the stellar metallicity, we find a similar value, but with more precision and a better significance (2.08 versus ∼ 1.1), due to the higher number of objects and wider range of redshift of our sample.

Millán-Irigoyen, I. (ORCID:0000000341155140)↗

NASA NTRS1986

Iron oxide and hydroxide precipitation from ferrous solutions and its relevance to Martian surface mineralogy

Experiments were performed to examine if the ubiquitousness of a weak magnetic component in all Martian surface fines tested with the Viking Landers can be attributed to ferric iron precipitation in aqueous solution under oxidizing conditions at neutral pH. Ferrous solutions were mixed in deionized water and various minerals were added to separate liquid samples. The iron-bearing additives included hematite, goethite, magnetite, maghemite, lepidocrocite and potassium bromide blank at varying concentrations. IR spectroscopic scans were made to identify any precipitates resulting from bubbling oxygen throughout the solutions; the magnetic properties of the precipitates were also examined. The data indicated that the lepidocrocite may have been preferentially precipitated, then aged to maghemite. The process would account for the presumed thin residue of maghemite on the present Martian surface, long after abundant liquid water on the Martian surface vanished.

Posey-Dowty, J.↗

NASA NTRS2016

Liquid Oxygen/Liquid Methane Integrated Power and Propulsion

The proposed paper will cover ongoing work at the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) on integrated power and propulsion for advanced human exploration. Specifically, it will present findings of the integrated design, testing, and operational challenges of a liquid oxygen / liquid methane (LOx/LCH4) propulsion brassboard and Solid Oxide Fuel Cell (SOFC) system. Human-Mars architectures point to an oxygen-methane economy utilizing common commodities, scavenged from the planetary atmosphere and soil via In-Situ Resource Utilization (ISRU), and common commodities across sub-systems. Due to the enormous mass gear-ratio required for human exploration beyond low-earth orbit, (for every 1 kg of payload landed on Mars, 226 kg will be required on Earth) increasing commonality between spacecraft subsystems such as power and propulsion can result in tremendous launch mass and volume savings. Historically, propulsion and fuel cell power subsystems have had little interaction outside of the generation (fuel cell) and consumption (propulsion) of electrical power. This was largely due to a mismatch in preferred commodities (hypergolics for propulsion; oxygen & hydrogen for fuel cells). Although this stove-piped approach benefits from simplicity in the design process, it means each subsystem has its own tanks, pressurization system, fluid feed system, etc. increasing overall spacecraft mass and volume. A liquid oxygen / liquid methane commodities architecture across propulsion and power subsystems would enable the use of common tankage and associated pressurization and commodity delivery hardware for both. Furthermore, a spacecraft utilizing integrated power and propulsion could use propellant residuals - propellant which could not be expelled from the tank near depletion due to hydrodynamic considerations caused by large flow demands of a rocket engine - to generate power after all propulsive maneuvers are complete thus utilizing previously wasted mass. Such is the case for human and robotic planetary landers. Although many potential benefits through integrated power & propulsion exist, integrated operations have yet to be successfully demonstrated and many challenges have already been identified the most obvious of which is the large temperature gradient. SOFC chemistry is exothermic with operating temperatures in excess of 1,000 K; however, any shared commodities will be undoubtedly stored at cryogenic temperatures (90-112 K) for mass efficiency reasons. Spacecraft packaging will drive these two subsystems in close proximity thus heat leak into the commodity tankage must be minimized and/or mitigated. Furthermore, commodities must be gasified prior to consumption by the SOFC. Excess heat generated by the SOFC could be used to perform this phase change; however, this has yet to be demonstrated. A further identified challenge is the ability of the SOFC to handle the sudden power spikes created by the propulsion system. A power accumulator (battery) will likely be necessary to handle these sudden demands while the SOFC thermally adjusts. JSC's current SOFC test system consists of a 1 kW fuel cell designed by Delphi. The fuel cell is currently undergoing characterization testing at the NASA JSC Energy Systems Test Area (ESTA) after which a Steam Methane Reformer (SMR) will be integrated and the combined system tested in closed-loop. The propulsion brassboard is approximately the size of what could be flown on a sounding rocket. It consists of one 100 lbf thrust "main" engine developed for NASA by Aerojet and two 10 lbf thrusters to simulate a reaction control system developed at NASA JSC. This system is also under development and initial testing at ESTA. After initial testing, combined testing will occur which will provide data on the fuel cell's ability to sufficiently handle the power spikes created by the propulsion system. These two systems will also be modeled using General-Use Nodal Network Solver (GUNNS) software. Once anchored with test data, this model will be used to extrapolate onto other firing profiles and used to size the power accumulator.

Banker, Brian↗

NASA NTRS2020

Oxygen and carbon stable isotope composition of the weathering Mg-carbonates on the surface of the LEW 85320 ordinary chondrite: Revisited

New δ13C and δ18O values were measured to constrain the formation mechanisms of two previously identified generations (Antarctica and Houston) of terrestrial weathering carbonates, nesquehonite, which formed on the surface of the Lewis Cliff 85320 ordinary chondrite. These two nesquehonite generations exhibit a characteristic carbon and oxygen isotopic trend which starts with a linear δ13C-δ18O covariation followed by a continuous increase in δ18O with little to no change in δ13C. Based upon the newly developed nesquehonite-water oxygen isotope thermometry and the measured δ18O value of melted ice from Antarctica, the formation temperature of the Antarctic nesquehonite generation was estimated to be -1.9 ± 3℃. Houston nesquehonite generation was most likely formed from an evaporative residue of the melted Antarctic ice at 30 ± 4℃. Modeling the isotopic trend of the two generations suggests that evaporation created large δ18O variations in the nesquehonite while carbon isotopes were stabilized by exchange between the parent liquid and atmospheric CO2. Thus, we suggest that carbonates formed by terrestrial weathering in Antarctica should possess a widespread in δ18O values and a narrow range in δ13C values under dry and cold conditions. Finally, the observed wide spread of δ18O in Martian carbonates (e.g., Allan Hills 84001 and Nakhla) can be explained by evaporation near 0℃ and may have formed by a similar mechanism to that of the nesquehonite in the LEW 85320. Meanwhile, the wide spread of δ13C suggests that two carbon reservoirs with distinct isotope compositions on Mars (e.g., the atmospheric carbon and magmatic carbon) may be actively participating in the formation process.

weathering↗

DOE OSTI2024

Carotenoid cleavage enzymes evolved convergently to generate the visual chromophore

The retinal light response in animals originates from the photoisomerization of an opsin-coupled 11-cis-retinaldehyde chromophore. This visual chromophore is enzymatically produced through the action of carotenoid cleavage dioxygenases. Vertebrates require two carotenoid cleavage dioxygenases, β-carotene oxygenase 1 and retinal pigment epithelium 65 (RPE65), to form 11-cis-retinaldehyde from carotenoid substrates, whereas invertebrates such as insects use a single enzyme known as Neither Inactivation Nor Afterpotential B (NinaB). RPE65 and NinaB couple trans–cis isomerization with hydrolysis and oxygenation, respectively, but the mechanistic relationship of their isomerase activities remains unknown. Here we report the structure of NinaB, revealing details of its active site architecture and mode of membrane binding. Structure-guided mutagenesis studies identify a residue cluster deep within the NinaB substrate-binding cleft that controls its isomerization activity. Our data demonstrate that isomerization activity is mediated by distinct active site regions in NinaB and RPE65—an evolutionary convergence that deepens our understanding of visual system diversity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1982

Optimal preparation of the ECC ozonesonde

The ECC background current was identified as the removal of residual tri-iodide (iodine) as the cell approaches equilibrium. The altitude dependence of this source of the background current is expected to be only slowly changed in the troposphere with a more rapid decrease in the stratosphere. Oxygen does not play a role in the background current except in the unlikely situation where the electrodes have had all forms of iodine removed from them and the electrodes have not re-equilibrated with the sonde solutions before use. A solution mass transport parameter in the ECC was identified and its altitude dependence determined. The mass transport of tri-iodide dominates in the chemical transduction of ozone to electrical signal. The effect of the mass transport on the ECC background current is predicted. An electrochemical model of the ECC has been developed to predict the response of the ECC to various ozone vertical profiles. The model corresponds very closely to the performance of the ECC in the laboratory. Based on this model, an ECC with no background current is predicted to give total ozone values within 1% of the correct value, although the vertical profile may be in error by as much as + or - 15%.

Thornton, D. C.↗

NASA NTRS2004

Mission Cycle Life Prediction for C/SiC Composites

The residual strength and life of C/SiC is dominated by carbon interface and fiber oxidation if thermal and mechanical stresses combine with thermal expansion mismatch in a manner such that seal coat and matrix cracks are open to allow oxygen ingress. Under these circumstances life can be predicted by simple oxidation based models based on reaction controlled kinetics at low temperature and gas phase diffusion controlled kinetics at high temperature. Key life governing variables in these models include temperature, applied stress, initial strength, oxygen partial pressure and total pressure. In this paper these models are described and extended to mission cycle life prediction.

Levine, Stanley R.↗

DOE OSTI2021

Is Deprotonation of the Oxygen-Evolving Complex of Photosystem II during the S 1 → S 2 Transition Suppressed by Proton Quantum Delocalization?

We address the protonation state of the water-derived ligands in the oxygen-evolving complex (OEC) of photosystem II (PSII), prepared in the S 2 state of the Kok cycle. We perform quantum mechanics/molecular mechanics calculations of isotropic proton hyperfine coupling constants, with direct comparisons to experimental data from two-dimensional hyperfine sublevel correlation (HYSCORE) spectroscopy and extended X-ray absorption fine structure (EXAFS). We find a low-barrier hydrogen bond with significant delocalization of the proton shared by the water-derived ligand, W1, and the aspartic acid residue D1–D61 of the D1 polypeptide. The lowering of the zero-point energy of a shared proton due to quantum delocalization precludes its release to the lumen during the S 1 → S 2 transition. Retention of the proton facilitates the shuttling of a proton during the isomerization of the tetranuclear manganese–calcium–oxo (Mn 4 Ca–oxo) cluster, from the “open” to “closed” conformation, a step suggested to be necessary for oxygen evolution from previous studies. Our findings suggest that quantum-delocalized protons, stabilized by low-barrier hydrogen bonds in model catalytic systems, can facilitate the accumulation of multiple oxidizing equivalents at low overpotentials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1993

Diffusion-controlled magnesium isotopic fractionation of a single crystal forsterite evaporated from the solid state

Though the origin of calcium- and aluminum-rich inclusions (CAI's) in carbonaceous chondrites is till a disputed issue, evaporation is no doubt one of the most important processes for the formation of CAI's in the early solar nebula. The mechanism for production of large isotopic mass fractionation effects in magnesium, silicon, oxygen, and chromium in CAI's can be better understood by examining isotopic fractionation during the evaporation of minerals. New evaporation experiments were performed on single-crystal forsterite. The magnesium isotopic distribution near the evaporating surfaces of the residues using a modified AEI IM-20 ion microprobe to obtain rastered beam depth profiles was measured. A theoretical model was used to explain the profiles and allowed determination of the diffusion coefficient of Mg(++) in forsterite at higher temperatures than previous measurements. The gas/solid isotopic fractionation factor for magnesium for evaporation from solid forsterite was also determined and found to be nearly the same as that for evaporation of liquid Mg2SiO4.

Wang, Jianhua↗

DOE OSTI2023

Assessment of the quality of nuclear data for stable oxygen isotopes for Intentional Forensics applications

The Intentional Forensics (IF) project seeks to design a suite of tagging materials that can be used to unobtrusively “barcode” nuclear fuel. The idea being that, if the fuel leaves institutional controls and is later recovered, the “barcode” can be used to determine the provenance of the fuel. The IF project is investigating several schemes for this “barcode” and taggants with tailored isotopic compositions are once leading concept. Recently 18 O was suggested as a potential taggant [IF2023]. This report assesses the quality of 16,17,18 O evaluations in the ENDF/B-VIII.0 library [ENDF8.0]. In a neutron-rich environment such as a nuclear reactor, we are interested in two main processes – neutron scattering and neutron absorption (or capture). For the typical neutron energies encountered in a reactor, absorption is determined exclusively by the neutron radiative capture cross section (in which a neutron is absorbed, and the residual nucleus emits one or more gamma rays). The capture cross sections are described by and can be completely determined from R-matrix parameters in the ENDF evaluations. Therefore, it is sufficient to consider the quality of the neutron resonance part of these evaluations. Neutron scattering is determined mainly by the elastic scattering cross section which is very similar for all oxygen isotopes and is essentially constant until around 100 keV. The cross section varies from 3-4 barns, depending on the isotope, and 16 O has the largest elastic cross section of all isotopes. Therefore, we expect that significant amounts of 17 O and 18 O could diminish the moderating role of oxygen in fuel. We note that, in traditional power reactor, the hydrogen in the coolant water provides the vast majority of the moderation in the reactor, so the impact of 17 O and 18 O in any taggant would be minimal. At higher energies, neutron resonances start to play a role and the R-matrix parameters determine the cross sections. Fig. 1 shows the mass region near stable oxygen isotopes. As nuclei capture neutrons, they transmute into a different isotope, one unit to the right. In particular, 16 O transmutes to 17 O, 17 O transmutes to 18 O and 18 O transmutes to 19 O. 19 O, being unstable, beta decays in 27 s to 19 F. So, even if the 18 O neutron capture data is good, the fact that it transmutes into 19 F may be problematic and needs investigation. Fig. 2 from [NuDat] shows the thermal neutron capture cross sections for all nuclei in the ENDF/B-VII.1 library [ENDF7.1]. Clearly oxygen thermal capture values are quite small compared to other nuclei. Note, there is no 18 O evaluation in the ENDF/B-VII.1 library. In any event, given that neutron capture events lower the reactor reactivity and potentially induce chemical changes in the fuel, we will focus our attention on the capture part of the neutron resonances.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRSDate not supplied

Hydrogen Plasma Reduction of Silicates for Lunar Oxygen Liberation

As crewed missions to the moon become closer, the focus on in-situ resource utilization efforts has increased. Since lunar soil has abundant oxygen on the surface of the moon, work has been done to process this resource in an efficient manner. Hydrogen reduction of lunar regolith has emerged as a method of liberating oxygen that can be used for fuel and water production. Traditional reduction techniques require high temperatures and increased complexity when dealing with high amounts of silicates. Plasma can reduce silicates efficiently and thus has become of high interest for use in the lunar highlands where silicates exist in high quantities. NASA’s Kennedy Space Center is exploring the use of low temperature plasmas for the reduction of silicates. This work shows that exposing silicates to a hydrogen plasma produces water. Residual gas analysis and optical emission spectroscopy were used to measure the relative quantities of water vapor production and OH (A-X) emission for hydrogen plasma interactions with lunar highland simulant and silica. X-ray photo-electron spectroscopy and scanning electron microscopy/energy-dispersive X-ray spectroscopy were also used to observe surface modifications to the silicates that reflect the key chemical reactions that occurred. From this data, plasma has emerged as a promising solution to produce oxygen on the lunar surface. *Work supported by NASA's Science Technology Mission Directorate Center Innovation Fund.

R. P. Gott↗