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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

High Temperature Stability of Aqueous Foams for Potential Application in Enhanced Geothermal System (EGS)

Enhanced Geothermal Systems (EGS) are typically constructed by injecting high-pressure water into the deep hot dry rocks (HDR) under carefully controlled conditions to create new or re-open existing fractures, which usually utilizes an immense quantity of water. Alternatively, aqueous foam-based fracturing fluids may offer potential advantages over conventional water-based fracturing fluid, including reduced consumption of water and environmental impact. Although foam-based fracturing has shown promising results in oil and gas industries, its applicability to EGS is unknown. Foams are complex mixtures of liquids with gaseous phases that are thermodynamically unstable. Their stability will decrease over time due to liquid drainage, bubble coarsening, and coalescence. Therefore, it is essential to stabilize foam fluids at high temperatures for EGS related applications such as fracking of HDRs.This paper is focused on investigating high-temperature stability of N2-in-water or N2 foams containing different surfactants and stabilizing agents. Foam stability was characterized by the half-life, which is defined as the time a foam decreases to 50% of its original height due to drainage. Surfactants with various concentrations dissolved in deionized water were investigated, including alfa olefin sulfonate (AOS), sodium dodecyl sulfonate (SDS), TergitolTM (NP – 40), and cetyltrimethylammonium chloride (CTAC). Also, the effects of other stabilizing agents, including guar gum, bentonite clay, crosslinker, graphene oxide (GO) dispersion on foam stability were tested. Initial results showed that foam stability decreased dramatically as temperature increased. On the other hand, foams became relatively more stable as pressure increased. Certain stabilizing agents, such as guar gum and crosslinker, can enhance foam stability at a wide range of temperatures. Our results indicate that it may be possible to obtain stable foams at high-temperature, high-pressure conditions with appropriate stabilizing agents.

Thakore, Virensinh↗
DOE OSTI2021

Quantity of 135I Released from the AGR 5/6/7 Experiment

A series of four Advanced Reactor Technologies (ART) experiments have been conducted in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL). From 2006 through 2020, these experiments supported the development and qualification of the new U.S. tristructural isotropic (TRISO) particle fuel for Very High Temperature Reactors (VHTR). Each Advanced Gas Reactor (AGR) experiment consisted of multiple fueled capsules, each plumbed for independent temperature control using a mix of helium and neon gases. The gas leaving a capsule was routed to individual Fission Product Monitor (FPM) detectors. For intact fuel particles, the TRISO particle coatings provide a substantial barrier to fission product release. However, particles with failed coatings, whether because of a minute percentage of initially defective particles, those which fail during irradiation, or those designed to fail (DTF) particles, can release fission products to the flowing gas stream. Because reactive fission product elements like iodine and cesium quickly deposit on cooler capsule components and piping structures as the effluent gas leaves the reactor core, only the noble fission gas isotopes of Kr and Xe tend to reach FPM detectors. The FPM system utilizes High Purity Germanium (HPGe) detectors coupled with a thallium activated sodium iodide NaI(Tl) scintillator. The HPGe detector provides individual isotopic information, while the NaI(Tl) scintillator is used as a gross count rate meter. During irradiation, the 135mXe concentration reaching the FPM detectors is from both direct fission and by decay of the accumulated 135I. About 2.5 hours after irradiation (ten 15.3 minute 135mXe half lives) the directly produced 135mXe has decayed and only the longer lived 135I remains as a source. Decay systematics dictate that 135mXe will be in secular equilibrium with its 135I parent, such that its production rate very nearly equals the decay rate of the parent, and its concentration in the flowing gas stream will appear to decay with the parent half life. This equilibrium condition enables the determination of the amount of 135I released from the fuel particles by measurement of the 135mXe at the FPM following reactor shutdown. In this paper, the 135I released will be reported.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

Integral Measurement of the 237 Np($n$, γ) 238 Np Cross Section with Fast Neutrons

Accurate knowledge of the 237 Np($n$; γ) 238 Np cross section at fast neutron energies is important for applied nuclear science. The presently available experimental data has large disagreements in the fast neutron region. A measurement of the 237 Np($n$; γ) 238 Np cross section was performed using a well characterized fast neutron source and the results was compared with previous measurements and current nuclear data evaluations. This will provide an integral measurement that can be used as a benchmark for current evaluations. Multiple samples of 237 Np were irradiated in the Godiva-IV critical assembly. Following the irradiation, the samples placed in a γ-ray counting setup and the γ-rays emitted from the decay of 238 Np were measured over a time period of approximately 7 days. Multiple γ-ray decay branches of 238 Np were observed. The observed activity of 238 Np was used to calculate the amount of 238 Np produced during the irradiation via the 237 Np($n$; γ) 238 Np and an integral cross section of 359(10) mb was measured. The 238 Np half-life has been measured with a result of 50.34(7) hours. An integral measurement of the 237 Np($n$; γ) 238 Np cross section has been measured. This result has been compared to the calculated integral cross section using the ENDF/BVIII.0 and JENDL-4.0 evaluated cross sections and found to be in good agreement with ENDF/BVIII.0 value of 367 mb. The JENDL-4.0 evaluation yields a value of 312 mb, which is significantly lower than the measured cross section.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Latest results from the CUORE experiment

The CUORE experiment is searching for the neutrinoless double β decay of the 130Te using cryogenic calorimeters. The CUORE detector consists of 988 TeO2 crystals packed in 19 towers and placed in a cryogenic facility with a base temperature of 10 mK. Crystals are enriched in the isotope 130Te which is the candidate for the neutrinoless double β decay. It is taking data since 2017 at the Laboratori Nazionali del Gran Sasso in Italy. Such a long operation of a bolometric experiment in stable condition has no precedent: by reaching 1 tonne-year of exposure CUORE set a fundamental milestone for any future experiment using this technology. The CUORE collaboration investigated the neutrinoless double β decay of 130Te exploiting the updated 1 tonne-year of statistics, setting a limit of 2.2 × 1025 yr at the 90% of credibility interval on the half-life, with a median sensitivity of 2.8 × 1025 yr.

Adams, DQ↗
DOE OSTI2023

High temperature and high beam current compatible targets and methods thereof for generating noble gas/radiohalogen generators for medical isotopes

A method of providing alpha particle emitters and materials suitable for use in generating the alpha particles for medical treatment is disclosed. Metal oxide targets, preferentially Bi 2 O 3 pellets and Bi 2 O 3 coatings on metallic or metal oxide substrates are formed. The targets placed in a heated vacuum chamber subjecting to irradiation using a 6 Li beam at an elevated temperature below the melting point of the target generate a radioactive gas, such as 211 Rn, the radioactive gas is carried by an inert gas which is delivered a carrier for, such as a carbon column or oil for delivery to a treatment facility. The radioactive gas such as 211 Rn generates 211 At, which has a useable half-life of at least about 14 hours, in turn releases alpha particles which are effective for use in medical procedures.

Sampathkumaran, Uma↗
DOE OSTI2020

Reveal of Uranium Bioremediation Mechanisms by Bacillus Species through Proteomics Studies

Radionuclides, such as Uranium (U) and heavy metals continue to pose threats to the ecosystem health and processes at the Department of Energy (DOE) managed, Savannah River Site (SRS), located along the Savannah River near Aiken, SC. Such co-contaminated environments are difficult to remediate using conventional excavation and disposal or pump-and-treat approaches. Globally, more than 109 tons of uranium contaminated areas pose a long term threat to human and ecological health. Even with presented low concentrations in the brain, central nervous effects are still observed. Uranium and depleted uranium (DU) have long term effects on the kidneys. Some small general health effects include severe headaches and breathing problems. Uranus ions are toxic to living cells because they inhibit metabolism of carbohydrates by blocking ATP binding sites. Bioremediation by microorganisms represents an alternative solution, which is advantageous because of the possibility of biosorbent regeneration, cost-effectiveness, increased metal removal and easy recovery of some valuable metals. Bacillus sp. bacterium was previously used in the bioremediation of heavy metals in coal mine run off waters of SRS. However, its ability to bioremediate uranium was unknown so far. Hence, in the present study, uranium bioremediation by Bacillus sp. bacterium was investigated. The mechanism of bioremediation was also revealed through proteomics studies. Heavy metals contamination poses a serious threat to water, soil and human health. Soil and water are contaminated due to excessive exploitation of uranium mines for generation of nuclear energy and weaponry. It is not degradable easily and persist in soil and water for a long period of time due to its long half- life. Savannah river site (SRS) is one of the uranium contaminated sites. The physical or chemical remediation techniques are costly and complex. Microbial system approaches with competent bacteria has received increased attention due to its adaptability in various environmental matrices and cost effectiveness. However, even though there are multiple suggested pathways (F1), the specific mechanisms that drive this behavior are still unclear, especially with popular microorganisms such as Bacillus species. In a previous research (Ibeanusi et al, 2003) Bacillus sp. was shown to detoxify and precipitate a variety of heavy metals in coal pile runoff waters of SRS site. Additionally, genomic analysis demonstrated that this microorganism posses multiple attributes for chemical transport regulation and metabolic pathways. U remediation occurs during the first 20 hours of exposure. During this time period, Bacillus sp. may work primarily under two mechanisms - sorption and accumulation. These two mechanisms simultaneously work to protect the microorganism from high concentrations. Figure 10 demonstrates that certain proteins are up regulated and down regulated under extreme stressful conditions. Membrane fraction proteins were up regulated. Cytosolic fraction proteins were down regulated. This protein information coincides with the adsorption behavior. Bacillus sp. is a good candidate for U remediation at various concentrations.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

The Nature and State of Groundwater Contamination at the Nevada National Security Site: What Have We Learned from Decades of Groundwater Analysis? - 20337

The regulatory framework for remediating radionuclide contamination from underground nuclear testing at the Nevada National Security Site (NNSS) is based on a combination of characterization and modeling studies, monitoring, and institutional controls [1]. Currently, tritium is the largest contributor (∼90%) to the estimated 44.6 million-curie radionuclide inventory resulting from underground testing [2]. Because of its short half-life (12.32 years), its relative contribution reduces below 10% of the total radiologic inventory over the next 120 years as a result of radioactive decay. Although tritium levels are observed well above the Safe Drinking Water Act (SDWA) maximum contaminant levels (MCLs) in groundwater, other radionuclides are well below their MCLs except within the nuclear test near-field (nuclear test cavity and chimney) environment. In fact, most device-derived radionuclides are below their MCL in groundwater even in samples collected from this near-field environment. The distribution of radionuclides following the nuclear detonation greatly influences the availability of potential contaminants for groundwater transport. Tritium is initially distributed in the gas phase, later as tritiated water in steam, and finally as liquid water, and is available to groundwater transport away from the near-field environment. Other radionuclides that are mobile in groundwater are {sup 14}C, {sup 36}Cl, {sup 99}Tc, and {sup 129}I though their radiologic inventory is small when compared to tritium. Many radionuclides (e.g. U, Pu, Am) are incorporated to a significant extent into the melt glass at the bottom of the cavity and are accessible to groundwater primarily through the slow process of glass dissolution. These radionuclides are also adsorbed to the surfaces of the crushed rock within the cavity and chimney which limits their migration in groundwater. Although colloid facilitated transport of radionuclides at the NNSS has been observed [3], radionuclide concentrations decrease with time and migration distances due to desorption and colloid filtration processes. Current studies indicate that radionuclides associated with colloids are unlikely to migrate downgradient from NNSS underground nuclear tests at concentrations above the SDWA MCL [4][5]. The results of over 50 years of sampling, along with an understanding of these post detonation processes, indicate that tritium is the only contaminant of concern downgradient of testing and that even tritium will not exceed its MCL in groundwater after ∼120 years. Although other longer-lived radionuclides may continue to be released slowly from the near-field environment they will likely never reach levels exceeding their MCLs in groundwater downgradient of the NNSS. Groundwater monitoring will continue to verify these observations. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Novel Photonuclear Methods to Produce an Argon-37 Standard

The mission of this research is to explore novel photonuclear-based pathways into the production of 37Ar. Above-background detection levels of 37Ar uniquely indicates the occurrence of an underground nuclear explosion, produced from fission neutrons interacting in the surrounding environment through the 40Ca(n,a)37Ar reaction. The half-life of 35 days allows on-site inspectors (OSI) adequate time following the nuclear event to detect 37Ar and verify compliance or defiance of non-proliferation treaties such as the Comprehensive Nuclear-Test-Ban Treaty (CTBT). An 37Ar standard would give OSI the ability to calibrate their detectors and measure detector efficiency allowing for the quantification of detected activity, give OSI authentic samples to test detectors in field exercises, and improve models predicting diffusion pathways of 37Ar through the underground environment.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

SARS-CoV-2 variant nanobodies and constructs comprising such nanobodies

A large and highly diverse nanobody library was constructed and screened against multiple variants of SARS-COV-2 to find nanobodies with high sensitivity and specificity for the variants. Four rounds of positive selection against a panel of six diverse SARS-COV-2 variant RBDs was performed with our high-diversity. At least 59 of these nanobodies were found to work well against Alpha, Beta, Gamma, Delta, Kappa, Lambda and Mu with some overlap efficacy against other variants. These nanobodies have efficacy as stand-alone nanobodies and as a construct comprising nanobodies linked to the human IgG1 constant fragment (Fc) (nanobody-hFc constructions or nb-hFcs) to make enhanced humanized sdAbs with all the attributes of nanobodies with improved half-life and optimized effector functions. Several promising nanobodies that neutralize the original SARS-COV-2 and several of its variants have been identified, including Delta, with high efficacy. In particular, a subset of these nanobodies bind to the Omicron RBD.

Harmon, Brooke Nicole↗
DOE OSTI2025

Tritium Breeder Composites for Fusion Applications

Due to the short half-life of tritium, all fusion reactors planned for long-term operation using a deuterium-tritium fuel cycle must produce sufficient tritium from reactions outside the core to maintain reactor operation. Typically, the core is surrounded by a tritium breeder blanket filled with lithium-containing materials which react under a neutron flux to form tritium that can then be collected. Here, reactor designers are forced to choose between using chemically reactive liquid breeders (e.g., Pb-Li, FLiBe, Li) or solid breeders, which often have lower lithium concentrations and questionable mechanical integrity under irradiation (e.g., Li4SiO4, Li2TiO3). To expand this pool of options, this work has sought to produce composite tritium breeder materials using lithium-containing ceramics and metal reinforcements. The resultant composite tritium breeders simultaneously feature higher lithium densities and improved mechanical integrity, including tensile strength and toughness, compared to other tritium breeders previously reported in literature.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Multiscale, mechanistic calculation of the effective silver diffusion coefficient in polycrystalline silicon carbide: application to silver release in AGR-1 TRISO particles

The silicon carbide (SiC) layer in tristructural isotropic (TRISO) fuel particles serves as a barrier to prevent the escape of fission from the fuel kernel. The release of silver (Ag) is a concern due to the long half-life of the 110mAg isotope. In this study, the effective diffusion coefficient of the fission product Ag through the grain boundary (GB) network is calculated using a combination of atomistic and phase-field methods. Atomistic calculations of Ag diffusivity in SiC bulk and GBs are leveraged to develop a mesoscale effective Ag diffusion coefficient (Deff) in SiC. Since GBs serve as pathways for Ag diffusion, Deff is defined as a function of temperature, microstructure variables, and fluence. Deff is implemented in the fuel performance code Bison to predict Ag release from AGR-1 TRISO fuel particles. We hereby quantify the impact of SiC grain size and irradiation on Ag release and improve Bison's predictions.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Understanding the effect of irradiation and silicon carbide microstructure on silver diffusion in TRISO particles

The silicon carbide (SiC) layer in tristructural isotropic (TRISO) fuel particles serves as a barrier to prevent the escape of fission from the fuel kernel. The release of silver (Ag) is a concern due to the long half-life of the 110mAg isotope. In this study, a combination of atomistic and phase-field methods focuses on quantifying the effect of irradiation and SiC microstructure on Ag diffusion. Atomistic calculations provide the Ag diffusivity in SiC bulk and GBs, also providing an estimate of the effect of irradiation defects on Ag diffusivity in bulk SiC. These lower length scale efforts are leveraged to develop a mesoscale effective Ag diffusion coefficient (Deff) in SiC. Deff is defined as a function of temperature, microstructure variables, and fluence. Deff is implemented in the fuel performance code Bison to predict Ag release from AGR-1 and AGR-2 TRISO fuel particles. We hereby quantify the impact of SiC grain size and irradiation on Ag release and improve Bison's predictions.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Absolute decay counting of 146 Sm with 4π cryogenic microcalorimetry

We present a methodology for absolute activity counting of long-lived isotopes based on cryogenic Decay Energy Spectroscopy. A 146 Sm source was produced at the TRIUMF Laboratory and then processed and purified at Lawrence Livermore National Laboratory, yielding a pure sample. The source was embedded within a 4π thermal absorber coupled to a magnetic microcalorimeter achieving nearly 100% counting efficiency. Experimental uncertainties were studied and modeled, including thermal coupling of the source to the absorber, pulse pile-up, trigger, and event selection efficiencies. Here, the absolute activity of the pure 146 Sm source was measured to better than 1% uncertainty.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Solvent‐Phobic and Ionophilic Carboxylated Polythiophene Layer for Fluoride‐Rich Cathode Electrolyte Interphase

Abstract One focal area of contemporary organic mixed ionic‐electronic conductor (OMIEC) research relates to utilization of dual‐conductive properties to enhance the ion/electron transfer kinetics for energy storage applications. Insight regarding OMIEC response toward the electrolyte anion and solvent used in lithium‐ion batteries (LIBs), however, is limited. Here, for the first time, the solvent‐phobic and ionophilic (SP‐IP) properties of the OMIEC, poly[3‐(potassium‐4‐butanoate)thiophene‐2,5‐diyl] (P3KBT), are revealed through comprehensive evaluation and characterization. The solvent‐phobic characteristics arise from the cooperation of dispersive interaction, polar interaction, and hydrogen‐bonding between P3KBT and electrolyte solvent. The ionophilic nature is driven by electrostatic interactions between P3KBT side chain carboxylate groups and LiPF 6 , and the reversible electrochemical doping/de‐doping of the polythiophene backbone with PF 6 ⁻ . The SP‐IP properties induce formation of a LiF‐ rich , Li 2 CO 3 ‐ limited cathode electrolyte interphase (CEI) layer when a P3KBT coating layer is applied to the active material surface, significantly improving half‐cell life to over 1500 cycles at 2C.

Ren, Haoze [Department of Chemical and Bimolecular↗
DOE OSTI2022

FITEVT: A FORTRAN program for arrival-time analysis of nuclear-decay events

FITEVT is a FORTRAN program designed to analyze recorded arrival times of nuclear-decay events affected by dead-time. Here, the primary goal of the program is precise and accurate determination of half-lives. Its method involves imposition of a known sufficiently long extending dead-time to the recorded event sequence, so that the original dead-time effects are completely obliterated and the remaining live-times of the survived events are known exactly. Upon completion of the analysis, the arrival-time spectrum and the live-time spectrum are predicted and compared to those constructed from the survived events.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Branching ratio and γ -ray emission probabilities in the decay of the J π = 13 / 2 + isomer in 197Hg

Gamma rays following the decay of the 197 g Hg and 197 m Hg radionuclides were measured using chemically-purified sources and a planar HPGe detector. In the case of 197 m Hg, precise values of 94.68 (9)% and 5.32 (9)% were confirmed for the IT and EC branches, respectively, the latter discovered to differ significantly from previously published data. The half-lives of 197 g Hg and 197 m Hg were also measured as 64.81 (24) h and 23.82 (4) h.

197𝑔Hg↗
DOE OSTI2021

The NUBASE2020 evaluation of nuclear physics properties *

The NUBASE2020 evaluation contains the recommended values of the main nuclear physics properties for all nuclei in their ground and excited, isomeric (T-1/2 >= 100 ns) states. It encompasses all experimental data published in primary (journal articles) and secondary (mainly laboratory reports and conference proceedings) references, together with the corresponding bibliographical information. In cases where no experimental data were available for a particular nuclide, trends in the behavior of specific properties in neighboring nuclei were examined and estimated values are proposed. Evaluation procedures and policies that were used during the development of this evaluated nuclear data library are presented, together with a detailed table of recommended values and their uncertainties.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗