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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Demonstration of Selective Single-Barium Ion Detection with Dry Diazacrown Ether Naphthalimide Turn-on Chemosensors

Single-molecule fluorescence imaging (SMFI) of gas-phase ions has been proposed for “barium tagging,” a burgeoning area of research in particle physics to detect individual barium daughter ions. This has potential to significantly enhance the sensitivity of searches for neutrinoless double-beta decay (0νββ) that is obscured by background radiation events. The chemistry required to make such sensitive detection of Ba 2+ by SMFI in dry Xe gas at solid interfaces has implications for solid-phase detection methods but has not been demonstrated. Here, we synthesized simple, robust, and effective Ba 2+ -selective chemosensors capable of function within ultrapure high-pressure 136 Xe gas. Turn-on fluorescent naphthalimide-(di)azacrown ether chemosensors were Ba 2+ -selective and achieved SMFI in a polyacrylamide matrix. Here, fluorescence and NMR experiments supported a photoinduced electron transfer mechanism for turn-on sensing. Ba 2+ selectivity was achieved with computational calculations correctly predicting the fluorescence responses of sensors to barium, mercury, and potassium ions. With these molecules, dry-phase single-Ba 2+ ion imaging with turn-on fluorescence was realized using an oil-free microscopy technique for the first time—a significant advance toward single-Ba 2+ ion detection within large volumes of 136 Xe, plausibly enabling a background-independent technique to search for the hypothetical process of 0νββ.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Materials Data on P6Pb3Xe11F58 by Materials Project

XeF2Pb3P6(Xe5F28)2 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two XeF2 clusters and one Pb3P6(Xe5F28)2 sheet oriented in the (0, 0, 1) direction. In each XeF2 cluster, Xe is bonded in a linear geometry to two equivalent F atoms. Both Xe–F bond lengths are 2.07 Å. F is bonded in a single-bond geometry to one Xe atom. In the Pb3P6(Xe5F28)2 sheet, there are three inequivalent Xe sites. In the first Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.08 Å) and one longer (2.10 Å) Xe–F bond lengths. In the second Xe site, Xe is bonded in a linear geometry to two equivalent F atoms. Both Xe–F bond lengths are 2.08 Å. In the third Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.08 Å) and one longer (2.09 Å) Xe–F bond lengths. There are two inequivalent Pb sites. In the first Pb site, Pb is bonded in a 9-coordinate geometry to nine F atoms. There are a spread of Pb–F bond distances ranging from 2.53–2.79 Å. In the second Pb site, Pb is bonded in a body-centered cubic geometry to eight F atoms. There are four shorter (2.52 Å) and four longer (2.57 Å) Pb–F bond lengths. There are three inequivalent P sites. In the first P site, P is bonded in an octahedral geometry to six F atoms. There are a spread of P–F bond distances ranging from 1.62–1.71 Å. In the second P site, P is bonded in an octahedral geometry to six F atoms. There are a spread of P–F bond distances ranging from 1.63–1.68 Å. In the third P site, P is bonded in an octahedral geometry to six F atoms. There are a spread of P–F bond distances ranging from 1.63–1.68 Å. There are nineteen inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one P atom. In the second F site, F is bonded in a distorted single-bond geometry to one Xe and one Pb atom. In the third F site, F is bonded in a linear geometry to one Xe and one Pb atom. In the fourth F site, F is bonded in a distorted bent 150 degrees geometry to one Xe and one Pb atom. In the fifth F site, F is bonded in a single-bond geometry to one P atom. In the sixth F site, F is bonded in a distorted single-bond geometry to one Pb and one P atom. In the seventh F site, F is bonded in a bent 150 degrees geometry to one Xe and one Pb atom. In the eighth F site, F is bonded in a single-bond geometry to one P atom. In the ninth F site, F is bonded in a bent 150 degrees geometry to one Xe and one Pb atom. In the tenth F site, F is bonded in a single-bond geometry to one P atom. In the eleventh F site, F is bonded in a single-bond geometry to one P atom. In the twelfth F site, F is bonded in a single-bond geometry to one P atom. In the thirteenth F site, F is bonded in a single-bond geometry to one P atom. In the fourteenth F site, F is bonded in a single-bond geometry to one P atom. In the fifteenth F site, F is bonded in a single-bond geometry to one Pb and one P atom. In the sixteenth F site, F is bonded in a single-bond geometry to one P atom. In the seventeenth F site, F is bonded in a single-bond geometry to one P atom. In the eighteenth F site, F is bonded in a single-bond geometry to one P atom. In the nineteenth F site, F is bonded in a single-bond geometry to one Pb and one P atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Fracture behavior of irradiation induced nanocrystalline UO 2 studied by in-situ mechanical testing in transmission electron microscopy

Uranium Dioxide (UO 2 ) is widely used as a fuel in current light water reactors (LWRs). Upon accumulation of radiation damage, LWR UO 2 fuel pellets start to develop a different microstructure at the pellet periphery when fuel burnup exceeds 45–50 GWd/tHM. The resulting porous, nanocrystalline microstructure is one of the most prominent microstructural changes occurring in such fuel. Its fracture mechanisms, which causes fuel fine fragmentation, could impact safety limits when the cladding breaches. Direct measurements of these properties are challenging, therefore a surrogate obtained via ion irradiation can be used. In this study, multiple microcantilevers were fabricated by focused ion beam from both fresh UO 2 and UO 2 irradiated with 84 MeV Xe 26+ ions to a peak dose of 1357 displacements per atom (dpa). Further, the irradiation produced a pseudo high burnup structure approximately 2 µm below the surface. In-situ nano-mechanical bending tests were conducted to investigate the fracture behavior and the effect of the surrogate UO 2 high burnup structure on local fracture properties. Fresh UO 2 fuel was observed to fracture in transgranular mode without nucleation or movement of dislocations. However, the Xe-irradiated nanocrystalline microcantilevers fractured along the grain boundaries, with no influence from the pre-existing micro-cracks in the microcantilever. Fracture toughness for this type of surrogate high burnup UO 2 structure is reported for the first time in literature. Both the fracture stress and toughness show degradation for UO 2 as a result of Xe-irradiation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2000

Reduced xenon diffusion for quantitative lung study--the role of SF(6)

The large diffusion coefficients of gases result in significant spin motion during the application of gradient pulses that typically last a few milliseconds in most NMR experiments. In restricted environments, such as the lung, this rapid gas diffusion can lead to violations of the narrow pulse approximation, a basic assumption of the standard Stejskal-Tanner NMR method of diffusion measurement. We therefore investigated the effect of a common, biologically inert buffer gas, sulfur hexafluoride (SF(6)), on (129)Xe NMR and diffusion. We found that the contribution of SF(6) to (129)Xe T(1) relaxation in a 1:1 xenon/oxygen mixture is negligible up to 2 bar of SF(6) at standard temperature. We also measured the contribution of SF(6) gas to (129)Xe T(2) relaxation, and found it to scale inversely with pressure, with this contribution approximately equal to 1 s for 1 bar SF(6) pressure and standard temperature. Finally, we found the coefficient of (129)Xe diffusion through SF(6) to be approximately 4.6 x 10(-6) m(2)s(-1) for 1 bar pressure of SF(6) and standard temperature, which is only 1.2 times smaller than the (129)Xe self diffusion coefficient for 1 bar (129)Xe pressure and standard temperature. From these measurements we conclude that SF(6) will not sufficiently reduce (129)Xe diffusion to allow accurate surface-area/volume ratio measurements in human alveoli using time-dependent gas diffusion NMR.

Non-NASA Center↗
DOE OSTI2020

Materials Data on MgAs2(XeF9)2 by Materials Project

MgAs2(XeF9)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of one MgAs2(XeF9)2 sheet oriented in the (-1, 0, 2) direction. there are two inequivalent Xe sites. In the first Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.02 Å) and one longer (2.13 Å) Xe–F bond lengths. In the second Xe site, Xe is bonded in a rectangular see-saw-like geometry to four F atoms. There are a spread of Xe–F bond distances ranging from 1.99–2.15 Å. Mg is bonded to six F atoms to form MgF6 octahedra that share corners with four AsF6 octahedra. The corner-sharing octahedra tilt angles range from 30–38°. There are a spread of Mg–F bond distances ranging from 1.98–2.05 Å. There are two inequivalent As sites. In the first As site, As is bonded to six F atoms to form AsF6 octahedra that share corners with two equivalent MgF6 octahedra. The corner-sharing octahedra tilt angles range from 35–38°. There are a spread of As–F bond distances ranging from 1.75–1.84 Å. In the second As site, As is bonded to six F atoms to form AsF6 octahedra that share corners with two equivalent MgF6 octahedra. The corner-sharing octahedral tilt angles are 30°. There are a spread of As–F bond distances ranging from 1.75–1.84 Å. There are eighteen inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one As atom. In the second F site, F is bonded in a bent 150 degrees geometry to one Mg and one As atom. In the third F site, F is bonded in a bent 150 degrees geometry to one Mg and one As atom. In the fourth F site, F is bonded in a bent 150 degrees geometry to one Mg and one As atom. In the fifth F site, F is bonded in a single-bond geometry to one As atom. In the sixth F site, F is bonded in a single-bond geometry to one Xe atom. In the seventh F site, F is bonded in a bent 150 degrees geometry to one Xe and one Mg atom. In the eighth F site, F is bonded in a single-bond geometry to one Xe atom. In the ninth F site, F is bonded in a single-bond geometry to one As atom. In the tenth F site, F is bonded in a single-bond geometry to one As atom. In the eleventh F site, F is bonded in a single-bond geometry to one As atom. In the twelfth F site, F is bonded in a single-bond geometry to one Xe atom. In the thirteenth F site, F is bonded in a linear geometry to one Xe and one Mg atom. In the fourteenth F site, F is bonded in a single-bond geometry to one As atom. In the fifteenth F site, F is bonded in a single-bond geometry to one As atom. In the sixteenth F site, F is bonded in a bent 150 degrees geometry to one Mg and one As atom. In the seventeenth F site, F is bonded in a single-bond geometry to one Xe atom. In the eighteenth F site, F is bonded in a single-bond geometry to one As atom.

36 MATERIALS SCIENCE↗
NASA NTRS1976

Widths of atomic 4s and 4p vacancy states, Z between 46 and 50

X-ray photoelectron and Auger spectra involving N sub 1, N sub 2, and N sub 3 vacancy states of Pd, Ag, Cd, In, and Sn were measured and compared with results of free-atom calculations. As previously observed in Cu and Zn Auger spectra that involve 3d-band electrons, free-atom characteristics are found, with regard to widths and structure, in the Ag and Cd M sub 4-N sub 4,5 N sub 4,5 and M sub 5-N sub 4,5 N sub 4,5 Auger spectra that arise from transitions of 4d-band electrons. Theoretical N sub 1 widths computed with calculated free-atom Auger energies agree well with measurements. Theory, however, predicts wider N sub 2 than N sub 3 vacancy states (as observed for Xe), while the measured N sub 2 and N sub 3 widths are nearly equal to each other and to the average of the calculated N sub 2 and N sub 3 widths. The calculations are made difficult by the exceedingly short lifetime of some 4 p vacancies and by the extreme sensitivity of super-Coster-Kronig rates, which dominate the deexcitation to the transition energy and to the fine details of the atomic potential.

Chen, M. H.↗
DOE OSTI2020

Materials Data on BaP2(XeF5)4 by Materials Project

BaP2(XeF5)4 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of two BaP2(XeF5)4 sheets oriented in the (0, 0, 1) direction. there are eight inequivalent Xe sites. In the first Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.07 Å) and one longer (2.09 Å) Xe–F bond lengths. In the second Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.07 Å) and one longer (2.08 Å) Xe–F bond lengths. In the third Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.07 Å) and one longer (2.08 Å) Xe–F bond lengths. In the fourth Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.06 Å) and one longer (2.10 Å) Xe–F bond lengths. In the fifth Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.06 Å) and one longer (2.11 Å) Xe–F bond lengths. In the sixth Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.07 Å) and one longer (2.09 Å) Xe–F bond lengths. In the seventh Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.07 Å) and one longer (2.08 Å) Xe–F bond lengths. In the eighth Xe site, Xe is bonded in a linear geometry to two F atoms. Both Xe–F bond lengths are 2.08 Å. There are two inequivalent Ba sites. In the first Ba site, Ba is bonded in a 10-coordinate geometry to ten F atoms. There are a spread of Ba–F bond distances ranging from 2.67–3.22 Å. In the second Ba site, Ba is bonded to twelve F atoms to form distorted BaF12 cuboctahedra that share a cornercorner with one PF6 octahedra and a faceface with one PF6 octahedra. The corner-sharing octahedral tilt angles are 22°. There are a spread of Ba–F bond distances ranging from 2.76–3.05 Å. There are four inequivalent P sites. In the first P site, P is bonded to six F atoms to form PF6 octahedra that share a cornercorner with one BaF12 cuboctahedra. There are a spread of P–F bond distances ranging from 1.62–1.67 Å. In the second P site, P is bonded to six F atoms to form PF6 octahedra that share a faceface with one BaF12 cuboctahedra. There are a spread of P–F bond distances ranging from 1.61–1.67 Å. In the third P site, P is bonded in an octahedral geometry to six F atoms. There are a spread of P–F bond distances ranging from 1.62–1.67 Å. In the fourth P site, P is bonded in an octahedral geometry to six F atoms. There are a spread of P–F bond distances ranging from 1.63–1.69 Å. There are forty inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one Xe atom. In the second F site, F is bonded in a single-bond geometry to one P atom. In the third F site, F is bonded in a single-bond geometry to one Ba and one P atom. In the fourth F site, F is bonded in a single-bond geometry to one Ba and one P atom. In the fifth F site, F is bonded in a single-bond geometry to one P atom. In the sixth F site, F is bonded in a distorted single-bond geometry to one Ba and one P atom. In the seventh F site, F is bonded in a bent 150 degrees geometry to one Xe and one Ba atom. In the eighth F site, F is bonded in a single-bond geometry to one Xe atom. In the ninth F site, F is bonded in a distorted bent 150 degrees geometry to one Xe and one Ba atom. In the tenth F site, F is bonded in a single-bond geometry to one P atom. In the eleventh F site, F is bonded in a single-bond geometry to one Ba and one P atom. In the twelfth F site, F is bonded in a single-bond geometry to one P atom. In the thirteenth F site, F is bonded in a distorted bent 120 degrees geometry to one Xe and one Ba atom. In the fourteenth F site, F is bonded in a single-bond geometry to one P atom. In the fifteenth F site, F is bonded in a linear geometry to one Xe and one Ba atom. In the sixteenth F site, F is bonded in a single-bond geometry to one Ba and one P atom. In the seventeenth F site, F is bonded in a distorted bent 120 degrees geometry to one Xe and one Ba atom. In the eighteenth F site, F is bonded in a distorted bent 150 degrees geometry to one Xe and one Ba atom. In the nineteenth F site, F is bonded in a single-bond geometry to one P atom. In the twentieth F site, F is bonded in a single-bond geometry to one P atom. In the twenty-first F site, F is bonded in a bent 150 degrees geometry to one Xe and one Ba atom. In the twenty-second F site, F is bonded in a single-bond geometry to one Ba and one P atom. In the twenty-third F site, F is bonded in a single-bond geometry to one Ba and one P atom. In the twenty-fourth F site, F is bonded in a single-bond geometry to one P atom. In the twenty-fifth F site, F is bonded in a distorted bent 150 degrees geometry to one Xe and one Ba atom. In the twenty-sixth F site, F is bonded in a distorted bent 150 degrees geometry to one Xe and one Ba atom. In the twenty-seventh F site, F is bonded in a single-bond geometry to one P atom. In the twenty-eighth F site, F is bonded in a single-bond geometry to one P atom. In the twenty-ninth F site, F is bonded in a distorted bent 150 degrees geometry to one Xe and one Ba atom. In the thirtieth F site, F is bonded in a single-bond geometry to one P atom. In the thirty-first F site, F is bonded in a single-bond geometry to one P atom. In the thirty-second F site, F is bonded in a single-bond geometry to one P atom. In the thirty-third F site, F is bonded in a distorted bent 150 degrees geometry to one Xe and one Ba atom. In the thirty-fourth F site, F is bonded in a 2-coordinate geometry to one Xe and one Ba atom. In the thirty-fifth F site, F is bonded in a single-bond geometry to one P atom. In the thirty-sixth F site, F is bonded in a single-bond geometry to one P atom. In the thirty-seventh F site, F is bonded in a distorted bent 150 degrees geometry to one Xe and one Ba atom. In the thirty-eighth F site, F is bonded in a single-bond geometry to one P atom. In the thirty-ninth F site, F is bonded in a bent 150 degrees geometry to one Xe and one Ba atom. In the fortieth F site, F is bonded in a distorted single-bond geometry to one Ba and one P atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Tailoring the Gating Effect of Organic Cage via a Porous Liquid Approach

Porous liquids (PLs) represent a new frontier in material design combining the merits of solid porous host and liquid phase in gas separation and catalysis. Herein, the PL construction approach is harnessed to tailor the gating effect of organic cages toward enhanced gas separation. A type-II fluorinated PL (F-PL) is developed via liquifying a fluorinated organic cage (F-cage) by a fluorinated ionic liquid (F-IL). The F-cage is featured by a small window size (≈5.1 Å), high surface area, good stability under highly ionic conditions, and abundant fluorine moieties. The F-IL possesses high steric hindrance (bulky cation) and structure similarity with the F-cage (fluorinated alkyl chain in the anion). The existing status structure integrity of F-cage in F-IL upon F-PL formation is illustrated via spectroscopy and X-ray-based techniques. The existence of rigid voids in F-PL is illustrated by positron annihilation lifetime spectroscopy (PALS) and the improved gas uptake capacity than F-IL via pressure-swing CO 2 uptake isotherms (0–40) bar. Further, the comparison of the gas uptake behavior (CO 2 , N 2 , CH 4 , and Xe) of F-PL and F-cage, combining the computational simulation, highlights that the PL construction can be leveraged to tune the window size of porous scaffolds, leading to enhanced gas selectivity.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Sub‐5 Ångstrom Porosity Tuning in Calixarene‐Derived Porous Liquids via Supramolecular Complexation Construction

Abstract Sub‐Ångstrom‐level porosity engineering, which is appealing in gas separations, has been demonstrated in solid carbon, polymer, and framework materials but rarely achieved in the liquid phase. In this work, a gas molecular sieving effect in the liquid phase at sub‐5 Ångstrom scale is created via sophisticated porosity tuning in calixarene‐derived porous liquids (PLs). Type II PLs are constructed via supramolecular complexation between the sodium salts of calixarene derivatives and crown ether solvents. The chemical structure variation and assembly behavior of the porous host upon PL construction are monitored by spectroscopy‐, X‐ray‐, and neutron‐scattering techniques. The presence of permanent porosity in calixarene‐derived PLs is verified by pressure swing gas uptake, altered CO 2 physisorption behavior, and molecular simulations. Sub‐5 Ångstrom porosity tuning within the PL phase is achieved by introducing bulky substituted groups on the benzene ring of the calixarene host, which then greatly affects the dynamic motion and transport behavior of CO 2 molecules and the Xe uptake performance. The approach being demonstrated in this work represents a promising pathway to tune and leverage the porosity effect for enhanced gas uptake capacity and selectivity in liquid sorbents.

Li, Errui [Department of Chemistry University of T↗
DOE OSTI2025

Sub-5 Ångstrom Porosity Tuning in Calixarene-Derived Porous Liquids via Supramolecular Complexation Construction

Sub-Ångstrom-level porosity engineering, which is appealing in gas separations, has been demonstrated in solid carbon, polymer, and framework materials but rarely achieved in the liquid phase. In this work, a gas molecular sieving effect in the liquid phase at sub-5 Ångstrom scale is created via sophisticated porosity tuning in calixarene-derived porous liquids (PLs). Type II PLs are constructed via supramolecular complexation between the sodium salts of calixarene derivatives and crown ether solvents. The chemical structure variation and assembly behavior of the porous host upon PL construction are monitored by spectroscopy-, X-ray-, and neutron-scattering techniques. The presence of permanent porosity in calixarene-derived PLs is verified by pressure swing gas uptake, altered CO 2 physisorption behavior, and molecular simulations. Sub-5 Ångstrom porosity tuning within the PL phase is achieved by introducing bulky substituted groups on the benzene ring of the calixarene host, which then greatly affects the dynamic motion and transport behavior of CO 2 molecules and the Xe uptake performance. Further, the approach being demonstrated in this work represents a promising pathway to tune and leverage the porosity effect for enhanced gas uptake capacity and selectivity in liquid sorbents.

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

Global Ocean Cooling of 2.3°C During the Last Glacial Maximum

Abstract Quantitative constraints on past mean ocean temperature (MOT) critically inform our historical understanding of Earth's energy balance. A recently developed MOT proxy based on paleoatmospheric Xe, Kr, and N 2 ratios in ice core air bubbles is a promising tool rooted in the temperature dependences of gas solubilities. However, these inert gases are systematically undersaturated in the modern ocean interior, and it remains unclear how air‐sea disequilibrium may have changed in the past. Here, we carry out 30 tracer‐enabled model simulations under varying circulation, sea ice cover, and wind stress regimes to evaluate air‐sea disequilibrium in the Last Glacial Maximum (LGM) ocean. We find that undersaturation of all three gases was likely reduced, primarily due to strengthened high‐latitude winds, biasing reconstructed MOT by −0.38 ± 0.37°C (1σ). Accounting for air‐sea disequilibrium, paleoatmospheric inert gases indicate that LGM MOT was 2.27 ± 0.46°C (1σ) colder than the pre‐industrial era.

Seltzer, A. M.↗
DOE OSTI2024

Electrical and thermal characteristics of LaB6 thermionic hollow cathodes operating in He, D2, Ar, and Xe at 4–200 Pa and 0.25–5 A cm−2

We report characteristics of lanthanum hexaboride (LaB6) cathodes for conditions relevant to a high-voltage, high-current switching device. LaB6 is selected because of its relatively low work function, stability in the presence of many common gas impurities, and a low evaporation rate (long life) at operating temperatures. We have investigated the effect of cathode geometry, gas type, pressure, and current on a LaB6 hollow cathode in a diode configuration with an opposing planar anode. The gas is stagnant at a relatively low pressure of 4–200 Pa (0.03–1.5 Torr) because of device high-voltage standoff requirements. In all cases, the plasma voltage decreases to a plateau value with increasing current where a practical device would operate. The plateau voltage aligns with the fill gas excitation or ionization voltage, depending on conditions. At high current, the cathode temperature exceeds that required for thermionic emission to supply the total current, a behavior that is understood by accounting for back-diffusing bulk electrons.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Lifetime measurement of excited states in 116 Xe

Lifetimes of excited states in 116 Xe were measured using the recoil-distance Doppler-shift technique. Excited 116 Xe nuclei were populated in the fusion-evaporation reaction 102 Pd( 16 O,2n) 116 Xe. Lifetimes of the $2^{+}_{1}$ and $4^{+}_{1}$ states were evaluated using the differential decay-curve method with $\gamma$-$\gamma$-coincidence data as well as lifetimes of the $6^{+}_{1}$ and $7^{-}_{1}$ states using simulations of spectra considering Doppler-shift attenuation effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Grain subdivision and structural modifications by high-energy heavy ions in UO 2 with different initial grain size

Irradiation with 84 MeV Xe ions at peak fluence above 7 × 10 17 ions/cm 2 has been carried out on two UO 2 samples with different initial grain sizes at 300 °C and 500 °C. Characterization of both grain structure and bubble morphology has been performed using transmission electron microscopy, image analysis and precession electron diffraction. The bubble size in the large-grained sample was smaller than that in the standard-grain sample, confirming fission gas precipitation resistance in the former. The ion irradiation in the high electronic energy deposition range has caused formation of a large density of dislocations which resulted in grain polygonization for the sample with standard grain size, which was observed in multiple lamellas extracted next to each other at peak dose. The sample with large grains showed inconsistent behavior. In one case, dislocation pile-up occurred, but no sub-grain formation was observed. An adjacent location showed sub-grain formation, even if to less extent compared to the standard grain-size sample. Furthermore, these findings suggest a limited polygonization resistance in large-grained UO 2 compared to standard-grain UO 2 . Recrystallization of both sample surfaces was present, leaving unclear if this is a surface effect or a consequence of the highest energy deposition rate in this area.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Development of bubble evolution model for new mechanistic transient fission gas release capability in BISON

This report summarizes efforts within NEAMS to investigate the mechanisms that govern fission gas behavior in UO 2 . In particular, the focus is on understanding how fission gas behavior causes transient fission gas release and fragmentation/pulverization of high burnup structure (HBS) in UO 2 . HBS forms in the periphery of the pellet where temperatures are relatively low. Previously, MD simulations were performed to determine the reaction energies for various Xe and U defects with bubbles, as a function of Xe to vacancy ratio or, equivalently, pressure. As had been shown in FY22, it was found that the unmodified version of the Simple Integrated Fission Gas Release and Swelling (SIFGRS) model within BISON greatly over-predicted the number gas atoms per vacancy in the bubbles in the outer rim of the pellet (a ratio of > 1 million). This was due to slow grain boundary vacancy diffusivity and not accounting for the pressure-dependent reaction energy for Xe interstitials with bubbles. The application of the pressure dependent reaction energies was able to restrict Xe to vacancy ratios to 2:1, which is far more realistic than those originally obtained from SIFGRS.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Xenon–metal pair formation in UO 2 investigated using DFT + U

A recent experimental study on a spent uranium dioxide (UO 2 ) fuel sample from Belgium Reactor 3 identified a unique pair structure formed by the noble metal phase (NMP) and fission gas [xenon (Xe)] precipitate. However, the fundamental mechanism behind this structure remains unclear. The present study aims to provide an understanding of the interaction between five different metal precipitates [molybdenum (Mo), ruthenium (Ru), palladium (Pd), technetium (Tc), and rhodium (Rh)] and the Xe fission gas atoms in UO 2 , by using density functional theory (DFT) in combination with the Hubbard U correction to compute the formation energies involved. All DFT + U calculations were performed with occupation matrix control to ensure antiferromagnetic ordering of UO 2 . The calculated formation and binding energies of the Xe and solid fission products in the NMP reveal that these metal precipitates form stable pair structures with Xe. Notably, the formation energy of Xe–metal pairs is lower than that of the isolated single defects in all instances, with Pd and Mo showing the most favorable binding energy, likely accounting for the observed pair structure formation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Microstructure evolution in U-10Zr alloy irradiated by swift Xe ions at 700 °C

The post-irradiation examination (PIE) results of U-10Zr binary metallic fuel that was irradiated by 84 MeV Xe ions at 700 °C are reported here. The U-10Zr specimen was synthesized by homogenizing elemental U and Zr powders through arc-melting. The as-fabricated U-10Zr was dominated by the sub-micron acicular α+ δ phase. After being irradiated by 84 MeV Xe ions at 700 °C up to 2.19 ×10 17 ions/cm 2 fluence, the U-10Zr was speculated to evolve into micro-scale γ 1 + γ 2 phases as predicted by the U-Zr phase diagram. During post-irradiation cooling, the U-rich γ 1 phase was mainly transformed to the αphase, while the Zr-rich γ 2 phase was partially retained along with formation of hexagonal structure phase (δ or ω). Xe bubbles formed in the γ 1 and γ 2 phases have salient different morphologies, implying faster Xe diffusion in the γ 1 phase than the γ 2 phase. The quantitative bubble morphology data collected in this study can provide valuable references for the development and validation of fuel performance models for this fuel.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Search for double-beta decay of $$\mathrm {^{130}Te}$$ to the $$0^+$$ states of $$\mathrm {^{130}Xe}$$ with CUORE

Abstract The CUORE experiment is a large bolometric array searching for the lepton number violating neutrino-less double beta decay ( $$0\nu \beta \beta $$ 0 ν β β ) in the isotope $$\mathrm {^{130}Te}$$ 130 Te . In this work we present the latest results on two searches for the double beta decay (DBD) of $$\mathrm {^{130}Te}$$ 130 Te to the first $$0^{+}_2$$ 0 2 + excited state of $$\mathrm {^{130}Xe}$$ 130 Xe : the $$0\nu \beta \beta $$ 0 ν β β decay and the Standard Model-allowed two-neutrinos double beta decay ( $$2\nu \beta \beta $$ 2 ν β β ). Both searches are based on a 372.5 kg $$\times $$ × yr TeO $$_2$$ 2 exposure. The de-excitation gamma rays emitted by the excited Xe nucleus in the final state yield a unique signature, which can be searched for with low background by studying coincident events in two or more bolometers. The closely packed arrangement of the CUORE crystals constitutes a significant advantage in this regard. The median limit setting sensitivities at 90% Credible Interval (C.I.) of the given searches were estimated as $$\mathrm {S^{0\nu }_{1/2} = 5.6 \times 10^{24} \, \mathrm {yr}}$$ S 1 / 2 0 ν = 5.6 × 10 24 yr for the $${0\nu \beta \beta }$$ 0 ν β β decay and $$\mathrm {S^{2\nu }_{1/2} = 2.1 \times 10^{24} \, \mathrm {yr}}$$ S 1 / 2 2 ν = 2.1 × 10 24 yr for the $${2\nu \beta \beta }$$ 2 ν β β decay. No significant evidence for either of the decay modes was observed and a Bayesian lower bound at $$90\%$$ 90 % C.I. on the decay half lives is obtained as: $$\mathrm {(T_{1/2})^{0\nu }_{0^+_2} > 5.9 \times 10^{24} \, \mathrm {yr}}$$ ( T 1 / 2 ) 0 2 + 0 ν > 5.9 × 10 24 yr for the $$0\nu \beta \beta $$ 0 ν β β mode and $$\mathrm {(T_{1/2})^{2\nu }_{0^+_2} > 1.3 \times 10^{24} \, \mathrm {yr}}$$ ( T 1 / 2 ) 0 2 + 2 ν > 1.3 × 10 24 yr for the $$2\nu \beta \beta $$ 2 ν β β mode. These represent the most stringent limits on the DBD of $$^{130}$$ 130 Te to excited states and improve by a factor $$\sim 5$$ ∼ 5 the previous results on this process.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗