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At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Probe nuclear structure using the anisotropic flow at the Large Hadron Collider

Abstract Recent studies have shown that the shape and radial profile of the colliding nuclei have strong influences on the initial condition of the heavy ion collisions and the subsequent development of the anisotropic flow. Using A Multi-Phase Transport model (AMPT) model, we investigated the impact of nuclear quadrupole deformation $$\beta _2$$ β 2 and nuclear diffuseness $$a_0$$ a 0 of $$^{129}$$ 129 Xe on various of flow observables in Xe–Xe collisions at $$\sqrt{s_{\textrm{NN}}}=$$ s NN = 5.44 TeV. We found that $$\beta _2$$ β 2 has a strong influence on central collisions while $$a_0$$ a 0 mostly influences the mid-central collisions. The relative change of flow observables induced by a change in $$\beta _2$$ β 2 and $$a_0$$ a 0 are also found to be insensitive to the values of parameters controlling the strength of the interaction among final state particles. Our study demonstrates the potential for constraining the initial condition of heavy ion collisions using future system scans at the LHC.

Physics↗
DOE OSTI2022

Improving the laser performance of ion beam sputtered dielectric thin films through the suppression of nanoscale defects by employing a xenon sputtering gas

Laser damage-prone precursors in high index materials such as hafnia are believed to be the primary limiter in the performance of dielectric multilayer films to advance ultra-high power and energy laser applications. Removing or suppressing these precursors is the key to fabricating laser damage resistant thin films for the enabling technologies. Early work has revealed that nanobubbles formed by entrapped argon (Ar) working gas in ion beam sputtering (IBS) produced hafnia films are primarily responsible for the onset of laser damage upon exposure to UV, ns-laser pulses. In this study, we demonstrate that the UV ns-laser damage onset of IBS produced hafnia films can be improved to 3.1 +/- 0.2 J/cm 2 by substituting the conventional Ar working gas with xenon (Xe), a nearly 1 J/cm 2 increase from that of the Ar produced hafnia films. In addition to the suppression of the overall point-defect density of the hafnia films, the reduction of the Xe entrapment eliminates the nanobubbles and the generation of plasmas that initiates the laser damage. The defect suppression and its correlation to the increase in laser damage threshold is revealed by the combined analysis of Rutherford backscattering spectroscopy, electron paramagnetic resonance spectroscopy, transmission electron microscopy, and laser damage testing. Monte Carlo simulations suggest a much smaller entrapment of Xe gas by comparison to Ar, which is attributed to the significant difference in the energy of the reflected neutrals (3X) which are likely to be implanted. These results provide an effective process route with a fundamental understanding for producing high laser damage resistant dielectric films for high power and high energy laser applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Impact of Glass Irradiation on Laser-induced Breakdown Spectroscopy Diagnostics in the Visible and NIR Range

Increased absorption of optical materials arising from the exposure to ionizing radiation must be accounted for to accurately analyze the laser-induced breakdown spectroscopy (LIBS) data retrieved from high-radiation environments. We evaluate this effect on a specifc example that mimics the diagnostics placed within a gas-cooled fast reactor coolant stream. Analysis is performed on the LIBS data measured with 1% Xe gas in an ambient He environment and the measured optical absorption from the gamma- and neutron-irradiated low-OH fused silica and sapphire glasses. No significant change in the number of shots required to reach a 3σ detection level was observed up to 10 Mrad gamma dose and exposure to a 1.7×10 17 n/cm 2 neutron fluence. In contrast, the spectral dependence of absorption results in either a systematic overestimation or underestimation of line intensity ratios, depending on the line of interest selected for analysis. Moreover, if lines from different spectral regions are used to create Boltzmann plots, this attenuation also leads to statistically significant changes in the calculated temperatures for calculations using Xe II lines only, lowering them from 8000±610 K to 6800±810 K for the case of exposure to the 1.7×10 17 n/cm 2 flux, and broadening the temperature range required for a 95% confidence interval. In the case of measuring the Xe spectrum, these effects may be mitigated using only the longer-wavelength spectral region, where radiation-attenuation is relatively small, or through analysis using the iterative Saha-Boltzmann method.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Integrated Off-gas System: A Preconceptual Design of an Integrated Off-Gas Treatment System

The U.S. has a vested interest in the advancement of nuclear energy to achieve aggressive net-zero goals, with reprocessing and recycling of used nuclear fuels (UNF) playing a vital role. It will not be possible to meet U.S. regulatory requirements without robust off-gas treatment, so it is crucial to advance treatment technologies to facilitate the design of future reprocessing facilities. For many years, teams of researchers across the U.S. Department of Energy (DOE) National Laboratory complex have been investigating off-gas treatment technologies for the capture and removal of volatile radionuclides (i.e., 85 Kr, Xe, 14 C, and 129 I) and oxides of nitrogen (NO X ) that are produced from reprocessing. These investigations have been focused on developing individual technologies for the capture of Kr, Xe, iodine, and CO 2 . Capture technologies for each constituent were tested independently from one another by utilizing nonradioactive surrogates to simulate simplified off-gas streams. The tests have been relatively small, laboratory-scale experiments of up to approximately 1 L/minute total gas flow rate. To increase the readiness of these technologies for deployment, an integrated test system with a larger-scale capacity is needed to bridge the gap between promising bench scale and fully scalable UNF reprocessing off-gas treatment. This document contains the goals, design basis, functional requirements, preconceptual design, and cost estimates for an integrated off-gas demonstration system for the capture and removal of NO x , Kr, Xe, CO 2 , and iodine at 10× higher throughput than earlier laboratory studies. The order-of-magnitude cost estimate for this system is approximately $\$$886,000. Next phases include conceptual design, detailed design, fabrication, and commissioning.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Krypton Concentration using HZ-PAN

Idaho National Laboratory (INL) has developed and tested engineered sorbents to separate and capture volatile fission products such iodine, xenon (Xe), and krypton (Kr) from off-gas streams. As noble gases, Xe and Kr can be difficult to capture and separate. Historically, cryogenic distillation has been used to execute the separation. However, performing this separation from bulk air streams is expensive and can pose significant hazards. INL has successfully developed two different sorbents for Xe and Kr capture, silver mordenite polyacrylonitrile and hydrogen mordenite polyacrylonitrile (HZ-PAN). Adsorption studies to date successfully separated and captured Kr from carrier gas streams, but those studies focused primarily on initial separation and capture. Successful utilization in a used nuclear fuel (UNF) reprocessing facility, however, requires further concentration of the Kr to minimize long term storage volumes. This study focuses on the concentration of Kr utilizing HZ PAN as the concentrating media. Concentrating Kr during desorption is ideal for two reasons: one, to produce Kr that can be used for commercial and research applications, or two, to minimize the volume of the radioactive gaseous waste stream for disposal. This report investigates the Kr concentrating potential of HZ-PAN by running multiple Kr adsorption-desorption cycles, collecting the desorbed effluent from a saturated HZ-PAN column, and loading it onto a fresh column. This study demonstrates that four adsorption-desorption cycles can transform a 150 ppmv Kr stream into a 37.5% Kr stream, an overall concentration factor of 2497. Each concentration step results in successively smaller volumes desorbed, reducing volume by a factor of approximately 40,000. Depending on the operational goals, during desorption one could collect smaller volume fractions of high concentration Kr (~ 67%). This demonstration should be considered proof-of-concept. Further refinement is necessary to develop optimum operating schemes to integrate into UNF off-gas treatment.

12 - MGMT OF RADIOACTIVE AND NON-RADIOACTIVE WASTE↗
DOE OSTI2022

Monitoring Xenon Capture in a Metal Organic Framework Using Laser-Induced Breakdown Spectroscopy

Molten salt reactor operation will necessitate circulation of a cover gas to remove certain evolved fission products and maintain an inert atmosphere. The cover gas leaving the reactor core is expected to contain both noble and non-noble gases, aerosols, volatile species, tritium, and radionuclides and their daughters. To remove these radioactive gases, it is necessary to develop a robust off-gas system, along with novel sensors to monitor the gas stream and the treatment system performance. In this study, a metal organic framework (MOF) was engineered for the capture of Xe, a major contributor to the off-gas source term. The engineered MOF column was tested with a laser-induced breakdown spectroscopy (LIBS) sensor for noble gas monitoring. The LIBS sensor was used to monitor breakthrough tests with various Xe, Kr, and Ar mixtures to determine the Xe selectivity of the MOF column. This study offers an initial demonstration of the feasibility of monitoring off-gas treatment systems using a LIBS sensor to aid in the development of new capture systems for molten salt reactors.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Impact of Glass Irradiation on Laser-Induced Breakdown Spectroscopy Data Analysis

Increased absorption of optical materials arising from exposure to ionizing radiation must be accounted for to accurately analyze laser-induced breakdown spectroscopy (LIBS) data retrieved from high-radiation environments. We evaluate this effect on two examples that mimic the diagnostics placed within novel nuclear reactor designs. The analysis is performed on LIBS data measured with 1% Xe gas in an ambient He environment and 1% Eu in a molten LiCl-KCl matrix, along with the measured optical absorption from the gamma- and neutron-irradiated low-OH fused silica and sapphire glasses. Significant changes in the number of laser shots required to reach a 3σ detection level are observed for the Eu data, increasing by two orders of magnitude after exposure to a 1.7 × 1017 n/cm2 neutron fluence. For all cases examined, the spectral dependence of absorption results in the introduction of systematic errors. Moreover, if lines from different spectral regions are used to create Boltzmann plots, this attenuation leads to statistically significant changes in the temperatures calculated from the Xe II lines and Eu II lines, lowering them from 8000 ± 610 K to 6900 ± 810 K and from 15,800 ± 400 K to 7200 ± 800 K, respectively, for exposure to the 1.7 × 1017 n/cm2 fluence. The temperature range required for a 95% confidence interval for the calculated temperature is also broadened. In the case of measuring the Xe spectrum, these effects may be mitigated using only the longer-wavelength spectral region, where radiation attenuation is relatively small, or through analysis using the iterative Saha–Boltzmann method.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1972

Noble gas studies on regolith materials from Apollo 14 and 15.

Abundances and isotopic compositions of the five stable noble gases, He, Ne, Ar, Kr, and Xe in soils and breccia were determined. The samples investigated included material from a range of depths in a trench and a core tube. Noble gas determinations were performed in a 6-inch all-metal mass spectrometer of high sensitivity. The grain size separates and stepwise heating experimental methods used give results that supplement each other. Calculated concentrations of spallation Xe-126 in many of the fines and gas-rich breccia are presented in a table. Bulk soil samples obtained by Apollo 14 show an inverse correlation of spallation Xe-126 with grain size.

Bogard, D. D.↗
NASA NTRS1975

Host phase of a strange xenon component in Allende

A description is presented for the isolation and characterization of the host phase from the Allende C3V chondrite and a mass spectrometric study of the five noble gases in this phase. It is though that the Xe component may have been produced by spontaneous fission of an extinct superheavy element. The fission Xe resides in a minor fraction comprising 0.5% of the meteorite. The fraction consists of chromite, an unknown Cr, Fe-mineral, and amorphous carbon. The gas components and the progenitor of the fission Xe may have been trapped in these minerals when they formed from the solar nebula.

Lewis, R. S.↗
NASA NTRS1977

Comments on 'Extinct radioactivities: Trapped residuals of presolar grains'

It has recently been suggested that extinct I-129 and Pu-244 were trapped in primitive-solar-nebula ('presolar') grains and decayed into radiogenic Xe-129 and fission Xe before the grains were incorporated into meteorite bodies. This idea is reconsidered in light of the thermal and metamorphic history of meteorites. The criteria that parent and daughter species should never separate and that minerals or grains containing the anomalous xenon should not be subjected to temperatures exceeding 500 C are applied to iron meteorites, achondrites, and chondrites to determine whether presolar grains could be the carriers of rare-gas anomalies to meteorites. The results strongly indicate that the xenon anomaly could not have originated in presolar grains. Other difficulties with the presolar-grain model are discussed, including insufficiently small grain sizes, large variations in Xe-129/I-127 ratios in various meteorites, and apparently unrealistic meteorite formation times and locations.

Trivedi, B. M. P.↗
NASA NTRS1978

Targets for producing high purity I-123

Tellurium powder in improved targets is bombarded with a cyclotron beam to produce Xe-123. Flowing gas streams carry the Xe-123 through one cold trap which removes Xe-123 that subsequently decays to I-123. During this bombardment energy is deposited in the target material causing its temperature to rise. Some of the tellurium vaporizes and subsequently condenses on surfaces that are cooler than the vaporization temperature. Provision is made for the repeated bombardment of this condensed tellurium.

Blue, J. W.↗
NASA NTRS1977

Anomalous krypton in the Allende meteorite

The reported investigation provides important new data for the heavy noble gases, especially Kr, in the Allende meteorite. The data are used to criticize the original model of Lewis et al. (1975) based on the noble gas data of these researchers. The conclusions reached in the investigation support alternative models which have been mainly based on Xe data by Lewis et al. (1975, 1977). Because of the relatively high noble gas abundances in the separates studied, disturbance from nuclear effects occurring in situ such as spallation and neutron capture is insignificant, offering an opportunity to study primordial Ar, Kr, and Xe. The isotopic and abundance data obtained from the samples largely confirm the noble gas results of Lewis et al. (1975, 1977) where isotopic correlations agree with the correlations of the considered samples. It is found that both Kr and Xe data are consistent with a two component mixture of 'ordinary' as well as 'anomalous' planetary gases.

Frick, U.↗
NASA NTRS1979

Clues to the origin of sulfide minerals in CI chondrites

The dominant sulfide in CI carbonaceous chondrites is an Fe-deficient pyrrhotite containing about 1% Ni, Alais, Ivuna, and Orgueil also contain minor cubanite, CuFe2S3, and Alais minor pentlandite, (Fe,Ni)9S8. All pyrrhotites contain 39.4 + or - 0.1% S; Ni contents range from 0.7 to 1.3%. The phase diagrams reveal no temperature at which the observed pentlandite-pyrrhotite assemblage is at equilibrium. Similarly, the pyrrhotite composition alone are inconsistent with equilibrium formation from a gas of solar composition. In Xe from high-purity submilligram Orgueil pyrrhotite separates, the ratios Xe-129/Xe-132 are not significantly larger than those in trapped meteoritic Xe. The lack of positive evidence for extinct I-129 in pyrrhotite does not permit any inferences regarding cooling rates in the early solar nebula. It is concluded that sulfides in CI chondrites cannot be nebular condensates formed under equilibrium conditions. Argon isotopic abundances reveal the presence of significant spallation and trapped gas components in Orgueil pyrrhotite. The Orgueil exposure age is calculated to be at least about 10 m.y.

Kerridge, J. F.↗
NASA NTRS1979

Xenon from intermediate zones of supernovae

The paper examines the photodisintegration and neutron capture in massive stars which show that the bulk of the p-isotopes of Xe is formed during the gamma-process of Woosley and Howard (1978) by stripping of the Xe + Be seeds. The environments in which the chondrites can be formed were determined by the neutron-capture calculations; they show that the Xe-124-rich gas must be associated at the sources with anomalously large overabundances of Nd-142, Sm-144, and possibly Ba-130, and with anomalously small overabundances of the p-isotopes of Se, Kr, Sr, and Mo.

Heymann, D.↗
NASA NTRS1981

Direct nuclear-pumped laser amplifier

A (He-3)-Xe gas mixture, excited by the He-3(n,p)H-3 reaction, has been employed to amplify the output of a (He-3)Xe direct nuclear-pumped laser. Lasing occurred at the 2.63 micron line of XeI in the oscillator. The oscillator output was reflected through 180 deg and passed through the amplifier system. Power measurements of the oscillator output and the amplifier output show the laser power to be amplified by a factor of 3 for the (He-3)-Xe system. Amplification by a factor of 5 was obtained for a (He-3)-CO system.

Jalufka, N. W.↗
NASA NTRS1981

Adsorption of xenon and krypton on shales

A method that uses a mass spectrometer as a manometer is employed in the measurement of Xe and Kr adsorption parameters on shales and related samples, where gas partial pressures were lower than 10 to the -11th atm, corresponding adsorption coverages are only small fractions of a monolayer, and Henry's Law behavior is expected and observed. Results show heats of adsorption in the 2-7 kcal/mol range, and Henry constants at 0-25 C of 1 cu cm STP/g per atmosphere are extrapolated. Although the adsorption properties obtained are variable by sample, the range obtained suggests that shales may be capable of an equilibrium adsorption with modern air high enough to account for a significant fraction of the atmospheric inventory of Xe, and perhaps even of Kr. This effect will nevertheless not account for the factor-of-25 defficiency of atmospheric Xe, in comparison with the planetary gas patterns observed in meteorites.

Podosek, F. A.↗
NASA NTRS1982

Sorption of noble gases by solids, with reference to meteorites. I - Magnetite and carbon

The trapping of meteoritic noble gases by solids is simulated through the synthesis of 18 Fe3O4 samples at 350-720 K in a noble gas atmosphere, by means of the reactions: (1) 3Fe + 4H2O yields Fe3O4 + 4H2, using Ne, Ar, Kr and Xe; and (2) 3Fe + 4CO yields Fe3O4 + 4C + carbides, using Xe. Etching experiments suggest an analogy with 'Phase Q' in meteorites. Adsorbed atmospheric gases are present in all samples, and dominate whenever the noble gas partial pressure in the atmosphere is greater than that in the synthesis. While many of the results of Lancet and Anders (1973) appear to have been dominated by such an atmospheric component, others are suspect. When the doubtful samples of Lancet and Anders are corrected or eliminated, the fractionation pattern no longer peaks at Ar, but rather, as in the present sample, rises monotonically from Ne to Xe. No evidence is found for the earlier study's claim of a strong temperature dependence.

Yang, J.↗
NASA NTRS1982

Sorption of noble gases by solids, with reference to meteorites. II - Chromite and carbon. III - Sulfides, spinels, and other substances; on the origin of planetary gases

The trapping of noble gases by chromite and carbon, two putative carriers of primordial noble gases in meteorites, was studied by synthesizing 19 samples in a Ne-Ar-Kr-Xe atmosphere at 440-720 K. Noble gas contents are found to approximately obey Henry's Law, but only slight correlations are found with composition, surface area, or adsorption temperature. Geometric mean distribution coefficients for bulk samples and HCl residues in 10 cu cm STP/g atm are: Xe 100, Kr 15, Ar 3.5, and Ne 0.62. Elemental fractionation data support the suggestion of Lewis et al. (1977) that chromite and carbon in C2 and C3 chondrites were formed by the reaction: Fe, Cr + 4CO yields (Fe, Cr)3O4 + 4C + carbides. In contrast to meteoritic minerals, the synthetic specimens show no isotopic fractionation of noble gases. In a subsequent study, attention is given to the cases of sulfides and spinels, on the way to consideration of the origin of planetary gases. Sulfides showed three distinctive trends relative to chromite or magnetite. The elemental fractionation pattern of Ar, Kr and Xe in meteorites, terrestrial rocks and planets resembles the adsorption patterns on the carbons, spinels, sulfides, and other solids studied. The high release temperature of meteoritic noble gases may be explained by transformation of the physisorbed or chemisorbed gas. The ready loss of meteoritic heavy gases on surficial oxidation is consistent with adsorption, as is the high abundance.

Yang, J.↗