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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Projected network performance for multiple isotopes using next-generation xenon monitoring systems

Since about 2000 (Bowyer et al., 1998), radioxenon monitoring systems have been under development and testing for the verification of the Comprehensive Nuclear Test-Ban Treaty (CTBT). Operation of the systems since then has resulted in development of a next-generation of systems that are nearly ready for operational deployment. By 2010, the need to screen out civilian sources was well known (Auer et al., 2010; Saey, 2009), and isotopic ratio approaches were soon considered (Kalinowski et al., 2014) to identify specific sources. New generation systems are expected to improve the ability to verify the absence of nuclear tests by using isotopic ratios when multiple isotopes are detected. In this work, thousands of releases were simulated to compute the global detection probability of 131m Xe, 133m Xe, 133 Xe, and 135 Xe at 39 noble gas systems in the International Monitoring System (IMS) for both current and next-generation systems. Three release scenarios are defined at 1 h, 1 d, and 10 d past a 1 kt TNT equivalent 235U explosion event. Multiple cases using from one part in a million to the complete release of the xenon isotopic activity are evaluated for each scenario. Coverage maps and global integrals comparing current and next-generation monitoring systems are presented showing that next-generation noble gas systems will create measurable improvements in the IMS. The global detection probability for 133 Xe is shown to be strong in all scenarios, but only modestly improved by next-generation equipment. However, the detection probability for 131m Xe and 133m Xe increased to about 50% in different scenarios, providing a second detectable isotope for many events. As anticipated from shorter sampling intervals, the expected number of detecting samples roughly doubled and the expected number of detecting stations rose by approximately 50% for all release scenarios. Thus, it might be anticipated that future events would consist of multiple 133 Xe detections and one or more second isotope detections. In conclusion, signals of this nature should increase detection confidence, tighten release location estimates, improve rejection of civilian signals, and lessen the impacts from individual systems being offline for maintenance or repair reasons.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2020

UNESE Data Analysis-Disko Elm Gas Transport Characteristics (NA-22 Quarterly Report)

Recently published papers have demonstrated the impact of sorption mechanisms on gas transport in the subsurface following an underground nuclear explosion. To include sorption processes in the multi-physics models of noble gas production and transport, researchers have conducted experiments of gas sorption in geologic materials and calibrated a linear (Henry’s law) sorption model for all gases in various geologic materials. As a part of Task #4, we requested the experimental data from Sandia Laboratories and derived a dual-mode (Henry’s absorption and Langmuir adsorption) sorption model. The derived model better describes the nonlinear sorption mechanism with much higher fitness with the experimental data. When gas concentrations are relatively low (in the conditions of field experiments or underground nuclear explosions) compared to those used sorption experiments, the nonlinear sorption model can be approximated as a linear sorption model. The equivalent Henry’s constant, which equals the product of Langmuir capacity and affinity, is systematically higher than the literature values. Further analyses and comparison of sorption models are planned in FY2020 Q4 and the sorption model will be coupled in models of nonisothermal multiphase transport for studying noble gas detectability.

58 GEOSCIENCES↗
DOE OSTI2022

On the adsorption and reactivity of element 114, flerovium

Flerovium (Fl, element 114) is the heaviest element chemically studied so far. To date, its interaction with gold was investigated in two gas-solid chromatography experiments, which reported two different types of interaction, however, each based on the level of a few registered atoms only. Whereas noble-gas-like properties were suggested from the first experiment, the second one pointed at a volatile-metal-like character. Here, we present further experimental data on adsorption studies of Fl on silicon oxide and gold surfaces, accounting for the inhomogeneous nature of the surface, as it was used in the experiment and analyzed as part of the reported studies. We confirm that Fl is highly volatile and the least reactive member of group 14. Our experimental observations suggest that Fl exhibits lower reactivity towards Au than the volatile metal Hg, but higher reactivity than the noble gas Rn.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Frequency shifts in the electron paramagnetic resonance spectrum of 39 K due to spin-exchange collisions with polarized 3 He and precise 3 He polarimetry

The Zeeman splittings and electron paramagnetic resonance frequencies of alkali-metal atoms are shifted in the presence of a polarized noble gas. For a spherical geometry, the shift is enhanced over what is expected classically by a dimensionless atomic parameter 𝜅 0 that is unique to each alkali-metal-atom–noble-gas pair. Here, we present a precise measurement of 𝜅 0 for the 39 K − 3 He system with a relative accuracy of better than 1%. A critical component of achieving subpercent accuracy involved characterizing the shape of our samples using both MRI and CT medical-imaging techniques. The parameter 𝜅 0 plays an important role in establishing the absolute polarization of 3 He in a variety of contexts, including polarized targets for electron-scattering experiments and MRI of the gas space of the lungs. Our measurement more than doubles the accuracy possible when using 𝜅 0 for polarimetry purposes. Just as important, the work presented here represents a direct measurement of 𝜅 0 for the 39 K − 3 He system; previous values for 𝜅 0 in the 39 K − 3 He system relied on a chain of measurements that were benchmarked by previous measurements of 𝜅 0 in the Rb- 3 He system.

Zeeman effect↗
DOE OSTI2025

First experimental determination of the ⁴⁰Ar(𝑛, 2𝑛)³⁹Ar reaction cross section and ³⁹Ar production in Earth’s atmosphere

The cosmogenic ³⁹Ar(t1∕2 = 268 years) isotope of argon is used for geophysical dating and tracing of underground and ocean water, as well as ice owing to its appropriate half-life and chemical inertness as a noble gas; ³⁹Ar serves also in nuclear weapon test monitoring. We measured for the first time the total cross section of the main ³⁹Ar cosmogenic production reaction in the atmosphere, namely ⁴⁰Ar(𝑛, 2𝑛)39 Ar, using 14.8 ± 0.3 MeV neutrons. The neutrons, produced by a deuterium-tritium generator, impinged on a stainless steel sphere filled with Ar gas highly enriched in the ⁴⁰Ar isotope and were monitored by a stack of fast-neutron activation foils. The reaction yield was measured by atom counting of long-lived ³⁹Ar with noble gas accelerator mass spectrometry and, independently, by decay counting relative to atmospheric argon (³⁹Ar/Ar= 8.12 × 10−16 ). A total ⁴⁰Ar(𝑛, 2𝑛)39 Ar cross section of 610 ± 100 mb was determined at 14.8 ± 0.3 MeV incident neutron energy. This result serves as a benchmark for recent theoretical calculations and evaluations, found to reproduce well the experimental total cross section. We use these energy-dependent theoretical cross sections together with experimental spectra of cosmogenic neutrons at different altitudes to calculate the global average rate of neutron-induced ³⁹Ar atmospheric production, resulting in 770 ± 240 39 Ar atoms/cm²/day. The secular equilibrium between the ³⁹Ar calculated production rate and radioactive decay rate leads to a partial isotopic abundance ³⁹Ar/Ar = (5.9 ± 1.8) × 10−16 , showing that ≈73% of atmospheric ³⁹Ar is produced by cosmogenic neutrons, the remaining part believed to be induced by muons and high-energy 𝛾 rays. The ⁴⁰Ar(𝑛, 2𝑛)³⁹Ar cross section at 14 MeV is also a key parameter for quantifying the anthropogenic contribution to atmospheric 39 Ar produced during the thermonuclear tests of the 1960s. We estimate that anthropogenic ³⁹Ar accounts for roughly 20% of the present atmospheric inventory.

39 Ar atmospheric production↗
DOE OSTI2023

Constraining Bedrock Groundwater Residence Times in a Mountain System with Environmental Tracer Observations and Bayesian Uncertainty Quantification: Modeling and Data Package

Groundwater residence times provide fundamental descriptions of hydrologic dynamics and mixing processes in mountainous watersheds. Yet, few observational datasets that can constrain groundwater residence times over broad timescales are available in high elevation mountain systems. Here we present field observations from May 2021 of dissolved noble gases (He, Ne, Ar, Kr, and Xe), Chloroflourcarbons (CFCs), Sulfurhexaflouride (SF6), and tritium (3H) sampled from the Pumphouse Lower Montane study site (wells PLM1, PLM6, and PLM7) within the East River Watershed, Colorado. The presented noble gas (PLM_noblegas_2021.csv) and environmental tracer (PLM_tracers_2021.csv) observation datasets, along with the associated modeling scripts, aide in quantifying groundwater residence times and recharge conditions in a high elevation mountain system. Furthermore, the modeling scripts quantify groundwater residence time and noble gas recharge condition uncertainties using a novel Markov-chain Monte Carlo approach. All data modeling scripts are written in the Python code.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Technical note: 21 Ne in the CoQtz-N quartz standard material

Intercomparison standards produced from mineral samples exposed to the natural cosmic ray flux are routinely used for interlaboratory comparison and normalization of measurements of the cosmogenic noble gases 3 He and 21 Ne. This effort is facilitated by the availability of multiple standard materials with a wide range of cosmogenic nuclide concentrations. The “CoQtz-N” quartz standard, which was originally produced and distributed as an intercomparison standard for cosmogenic 10 Be and 26 Al, has a significantly lower cosmogenic nuclide concentration than other mineral standards used for cosmogenic noble gas analysis and is therefore potentially useful for assessing the linearity of interlaboratory offsets across a wide range of concentrations. This paper reports 21 Ne analysis of 13 aliquots of CoQtz-N, interspersed with 14 aliquots of the commonly used CRONUS-A quartz standard, in three analytical sessions on two noble gas mass spectrometer systems. The excess 21 Ne concentration in CoQtz-N, normalized to the accepted value of 320 × 10 6 atoms g −1 for CRONUS-A, is 13.87 ± 0.24 × 10 6 atoms g −1 . Alternatively, the ratio of excess 21 Ne concentrations in CoQtz-N and CRONUS-A is 0.04330 ± 0.00077.

Balco, Greg [Lawrence Livermore National Laborator↗
DOE OSTI2022

Using STAX data to predict IMS radioxenon concentrations

The noble gas collection and measurement stations in the International Monitoring System (IMS) are heavily influenced by releases from medical isotope production facilities. The ability to reliably model the movement of radioxenon from the points of release to these IMS samplers has improved enough that a routine aspect of the analysis of IMS radioxenon data should be the prediction of the effect of releases from civilian nuclear facilities on the sample concentrations. In this work, predicted concentrations at IMS noble gas systems in Germany and Sweden based on measured releases from Institute for Radioelements (IRE) in Belgium and atmospheric transport modeling for a four-month period are presented and discussed.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2021

Direct Observation of the Depth of Active Groundwater Circulation in an Alpine Watershed

Abstract The depth of active groundwater circulation is a fundamental control on stream flows and chemistry in mountain watersheds, yet it remains challenging to characterize and is rarely well constrained. We collected hydraulic conductivity, hydraulic head, temperature, chemical, noble gas, and 3 H/ 3 He groundwater age data from discrete levels in two boreholes 46 and 81 m deep in an alpine watershed, in combination with chemical and age data from shallow groundwater discharge, to discern groundwater flow rates at different depths and directly observe active and inactive groundwater. Vertical head gradients are steep (average of 0.4) and thermal profiles are consistent with typical linear conductive continental geotherms. Groundwater deeper than ∼20 m is distinct from shallow groundwater and creek water in its chemistry, noble gas signature, and age (dominantly >65 years compared to <9 years). Together these results suggest low vertical groundwater flow velocities and a relatively shallow active circulation depth of ∼20 m. This hypothesis is tested with a simple 2‐D numerical fluid flow and heat transport model representing a hillslope transect through the two boreholes. The modeling indicates that the subhorizontally bedded sedimentary rocks underlying the basin are highly anisotropic with low vertical hydraulic conductivity, and at most ∼10% of bedrock recharge (equivalent to <2% of stream baseflow) flows below a depth of 20 m. The study demonstrates the considerable value of discrete‐depth hydrogeologic, chemical, and age data for determining active circulation depth, and illustrates an approach for maximizing the utility of individual boreholes drilled for mountain bedrock aquifer characterization.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Pressure Effects on the Relaxation of an Excited Ethane Molecule in High-Pressure Bath Gases

Here, we use molecular dynamics to calculate the rotational and vibrational energy relaxation of C 2 H 6 in Ar, Kr, and Xe bath gases over a pressure range of 10 to 400 atm and at temperatures of 300 K and 800 K. The C 2 H 6 is instantaneously excited by 80 kcal/mol randomly distributed into both vibrational and rotational modes. The computed relaxation rates show little sensitivity to the identity of the noble gas in the bath. Vibrational relaxation rates show a non-linear pressure dependence at 300 K. At 800 K the reduced range of bath gas densities covered by the range of pressures do not yet show any non-linearity in the pressure dependence. Rotational relaxation is characterized with two relaxation rates. The slower rate is comparable to the vibrational relaxation rate. The faster rate has a linear pressure dependence at 300 K but an irregular, nonlinear pressure dependence at 800 K. To understand this, a model was developed based on approximating the periodic box used in the molecular dynamics simulations by an equal-volume collection of cubes where each cube is sized to allow only single occupancy by the noble gas or the molecule. Combinatorial statistics then leads to a pressure and temperature dependent analytic distribution of the bath gas species the molecule encounters in a collision. This distribution, the dissociation energy of molecule/bath gas complexes and bath gas clusters, and the computed energy release per collision combine to show that only at 300 K is the energy release sufficient to dissociate likely complexes and clusters. This suggests that persistent and pressure-dependent clusters and complexes at 800 K may be responsible for the non-linear pressure dependence of rotational relaxation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Exploration for Blind Geothermal Resources in the State of Hawaii Utilizing Dissolved Noble Gasses in Well Waters

This study is an extension of the Hawaii Play Fairway Analysis (PFA), a statewide geothermal exploration project funded by the United States Department of Energy. Based on results from prior phases of the PFA, this project targeted 66 wells on the islands of Hawaii, Maui, Lanai, Oahu, and Kauai for sampling of dissolved noble gases, trace metals, common ions, and the stable isotopes 2H and 18O. Ultimately, 23 of the 66 well targets were sampled. The noble gas helium is used as an indicator of geothermal heat when excess 3He and/or 4He is present when compared to the atmospheric ratio of those isotopes (R/Ra). R/Ra is minimally affected by dilution and transport, allowing even those wells not perfectly situated over a geothermal system to indicate a geothermal anomaly. R/Ra anomalies are present on every island in this study. There is a strong correlation between R/Ra anomalies and proximity to rift zones and calderas. Across the islands R/Ra ranged from 15-16 on Kilauea's lower east rift zone, which is a mantle plume value, to 0.37 on Lanai, which is a crustal value. The majority of anomalous well samples had R/Ra values consistent with an upper mantle source. Mixing between upper mantle and crustal helium is evident on all islands. Geographically, R/Ra decreases from the high at Kilauea to upper mantle values at Mauna Loa, and remains at upper mantle values for all wells across the other volcanoes, with the exception of two of four sampled wells on Lanai.

15 GEOTHERMAL ENERGY↗
DOE OSTI2022

Argon equation of state data to 1 TPa: Shock compression experiments and simulations

Argon is the most abundant noble gas on Earth and its noble, atomic fluid nature makes it an excellent candidate for comparison of experiment and theory at extreme conditions. For this study, we performed a combined computational and experimental study on shock compressed cryogenic liquid argon. Using Sandia's Z machine, we shock compressed liquid argon to 600 GPa and reshock states up to 950 GPa. Laser shock experiments at the Omega Laser facility extend the principal Hugoniot to 1000 GPa and provided temperature data along the principal Hugoniot. The plate impact experiments and laser shock experiments used well-characterized impedance matching standards and demonstrate consistent results between the two platforms over a common range. Density functional theory based molecular dynamics simulations provided additional data on the Hugoniot to 600 GPa. The combined experimental data and simulation results provide constraints on the development of new equation of state models at extreme conditions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Studies of Helium Behavior in Uranium Hexafluoride

Several issues have arisen from experimental observations and/or theoretical postulation related to the behavior of helium in uranium hexafluoride (UF 6 ) matrices and how it may impact the ability to use this noble gas to quantify the fill date of the cylinder. A series of experiments was conducted to address several such issues, and the results and implications are reported here. Two issues relate to bias in the helium measurement due to ambient air from extraneous sources such as atmospheric air or from potential holdup in a large, activated alumina chemical trap. These issues are really a question of differential retention of helium versus three other inert gas isotopes (representative of other noble gases found in air) used as a calibration for air in leakage. Discernable bias was not detected in either case. Another issue had to do with helium potentially brought into the cylinder by a liquid UF 6 fill and subsequently released as the material solidifies and/or during storage. The solubility of helium in liquid UF 6 was measured to investigate this theory. The experiment quantified the potential magnitude of the initial helium contribution if present. The final issue was that of retention of helium in solid UF 6 . Investigation of this theory necessitated quantifying both the solubility and the diffusivity of helium in UF 6 . In one experiment, the solubility was measured at cryogenic temperature, allowing quantification of helium in solid UF 6 such as would be found in a cold trap. In a second experiment, transport of helium into and through a macroscopic plug of solid UF 6 was examined. The transport was very slight although apparently detectible. Effectively, only an upper limit to the transport could be determined, but that limit implied that helium holdup in solid UF 6 is a real possibility.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Fission Product Gas Monitoring During Fuel Drying Operations - 20094

The goal of the project was to devise and implement a method of accurately qualifying any noble gas emitted during fuel drying operations (part of the dry fuel storage process) in order to provide the data needed to validate the off-site dose calculations. The imputes of the project was the NRC publishing Information Notice 18-01, 'Noble Fission Gas Releases During Spent Fuel Cask Loading Operations' in February 2018. The information notice describes some industry events that occurred during vacuum drying operations as part of a dry fuel campaign. The solution was devised by Fort Calhoun Station staff in partnership with Mirion Technologies technical staff. The monitoring was accomplished by directing all the effluent from the fuel storage cask vacuum drying machine through a sample chamber containing a compact ISOCS characterized CZT based gamma spectrometer connected to a Mirion Data Analyst. This resulted near real-time quantification of the radionuclides of concern. (authors)

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2021

Laboratory Investigation of Gas Transport Through Variably Saturated Rock [Slides]

Project Overview: Noble gas fission products, such as xenon (Xe), are monitored to detect nuclear tests. For well-contained subsurface tests, transport to the surface will impact detected isotopic ratios, complicating event identification. Role of water saturation in subsurface transport is not well understood. Historic tests have taken place near or below the water table. To accurately predict breakthrough times and fractionation, gas transport must be characterized through intact rock with variable saturation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Fission gas trapped in Chornobyl fuel microparticles reveals details of reactor operations

The isotopic ratios of fission gas would provide important source information of a nuclear fuel sample found in the environment. However, it is believed that during a reactor accident like Chornobyl all fission gas is lost and that the radioactive particles found in the Chornobyl Exclusion Zone today are depleted in gases by the initial explosion and subsequent fire. We disprove this hypothesis by detection and analysis of trapped krypton and xenon in these particles. Our analysis of krypton and xenon isotopes by noble gas mass spectroscopy in combination with resonance ionization mass spectrometry establishes that important information about reactor operations like age, neutron flux and plutonium fission fraction can still be reconstructed from individual micrometer-sized particles even after decades of weathering in the environment.

Chornobyl↗
DOE OSTI2025

High Spatial Resolution Mapping of Retained Fission Gas

Fission gas isotopic analysis provides quantitative high precision determination of irradiated nuclear fuel burnup, offers diagnostic value, and informs fuel performance models. A measurement capability has been developed at Idaho National Laboratory (INL) for the release of retained fission gas using a focused laser and static noble gas mass spectrometry (MS) analysis. This high resolution (10s microns spot size) capability was demonstrated using Xe implanted metal foils.

07 - ISOTOPES AND RADIATION SOURCES↗
DOE OSTI2021

Radiation Stability of MOF Engineered Particles

Pacific Northwest National Laboratory (PNNL), in collaboration with Flibe Energy, demonstrated the fabrication of metal organic frameworks (MOFs) into engineered beads to manage off-gases released from advanced reactors, including molten salt reactors. Based on the commercial availability and easy to synthesis at scale, PNNL down-selected two MOF sorbents known as CuBTC and UiO-67. The sorbents were synthesized, characterized, and fabricated into mechanically robust engineered beads (composites) using wet granulation method using polymer as a binder. Further, MOF powders and and mechanically robust composites were exposed to gamma radiation using Co-60 source and characterized irradiated MOFs to demonstrate the structural stability. Among the two MOF sorbents identified, the CuBTC MOF was shown to be very promising for noble gas management at low temperature (193 K) compared to UiO-67 MOF. The high adsorption capacity of the synthesized composites was correlated to the high surface area and pore volume of the CuBTC MOF. Both MOFs retain structural integrity and long-range order even after exposure to 1000 kGy of radiation.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗