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Strategies for efficient and reliable texture measurements have been explored using the Nanoscale Ordered Materials Diffractometer (NOMAD) at the Spallation Neutron Source located at Oak Ridge National Laboratory (ORNL). To test these strategies, the texture of an Al alloy was also investigated using another neutron diffraction instrument, a constant-wavelength neutron diffractometer (NRSF2) located at the High Flux Isotope Reactor, also at ORNL. Reasonable agreement was found across the two experimental methods, but differences in overall texture strength and the symmetry of some components were noted, depending on the data reduction and analysis method selected. On the basis of these results, potential improvements are identified which would enhance the texture measurement capability on NOMAD.

Efforts to reestablish a domestic 238Pu production capability in support of National Aeronautics and Space Administration mission objectives are ongoing throughout the U.S. Department of Energy com...

The sensitivity of Neutron Macromolecular Crystallography to the presence of hydrogen makes it a powerful tool to complement X-ray crystallographic studies using protein crystals. The power of this technique is currently limited by the relative low neutron flux provided by even the most powerful neutron sources . The strong polarization dependence of the neutron scattering cross section of hydrogen will allow us to use Dynamic Nuclear Polarization to dramatically improve the signal to noise ratio of neutron diffraction data, delivering order of magnitude gains in performance, and enabling measurements of radically smaller crystals of larger protein systems than are possible today. We present a prototype frozen spin system, built at Oak Ridge National Laboratory to polarize single protein crystals on the IMAGINE beamline at the High Flux Isotope Reactor (HFIR). Details of the design and construction will be described, as will the performance of the system offline and during preliminary tests at HFIR.

We describe a generalized means of isotopic assay and quantification of multicomponent fissile mixtures based on the observation of short-lived fission-product gamma signatures. Given that the characteristic mass yield curves differ for individual fissile species, this can be used to construct an overdetermined system of equations corresponding to the observed photopeak yields, the solution of which yields information on the individual isotopic masses of parent fissile isotopes within the system. This method is then demonstrated for single-isotope samples of 233U, 235U, and 239Pu; binary fissile mixtures of U and Pu; and trace fissile samples contained within intact typical environmental sampling media, each irradiated and measured using the High Flux Isotope Reactor at the Oak Ridge National Laboratory. Our findings indicate that this method can reliably be used to quantify nanogram-level fissile masses in binary mixtures with uncertainties on the order of 2%–7%. Finally, observed discrepancies with individual fission-product indicators and likely sources of bias are discussed.

This paper describes the modeling and simulation of fluid structure interactions (FSI) of involute-shaped fuel plates used in nuclear research reactors. We believe this to be the first time that this type of application is described in the literature using a fully-coupled, and monolithic, finite element approach. The simulations are validated against plate deflection data for the conceptual design of the Advanced Neutron Source Reactor (ANSR), which was envisioned to be the world’s most powerful nuclear research reactor for neutron scattering and other applications, but was ultimately never completed. The high performance of the ANSR creates a bounding envelope for involute-shaped research reactors such as that used in the High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) which is undergoing research for the conversion from highly-enriched uranium (HEU) to low-enriched uranium (LEU) fuel. As such, the findings from the present FSI analyses carried out herein for the ANSR plates provide good guidelines and inform designers what should be expected for the next generation of plates in the HFIR. It is shown herein that the current approach can accurately capture the leading-edge deflections of the involute-shaped plates and simulations can predict the ‘S-shaped’ deflection of the first mode instilling confidence in the methodology.

An iterative design process involving neutronic and thermal-hydraulic modeling and simulation has been employed to assess the feasibility of converting the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) from high-enriched uranium (HEU) to low-enriched uranium (LEU) silicide dispersion fuel. ORNL is funded by the National Nuclear Security Administration to evaluate HFIR conversion. Previous HFIR conversion studies focused on U-10Mo monolithic fuel; however, due to potential fabrication issues with the complex HFIR U-10Mo fuel design, ORNL is evaluating U3Si2-Al dispersion fuel as an alternative LEU fuel system. Fueled by 10.1 kg of HEU and operated at 85 MW, HFIR provides one of the highest steady-state neutron fluxes of any research reactor in the world. Retrofitting a compact, high-power density, HEU-based core with LEU is a challenging problem to solve, especially when considering the conversion requirements. Neutronic and thermal-hydraulic analyses were performed with Shift and HSSHTC, respectively, to predict reactor performance and thermal safety margins. A number of designs were proposed and evaluated using an iterative approach in an effort to show that reactor performance could match that obtained using HEU fuel and that thermal safety margins were adequate. This study concludes that conversion of HFIR with U3Si2-Al LEU fuel is feasible if, among other requirements, the fuel meat region is centered and symmetric about the fuel plate thickness centerline, the active fuel zone length is increased from 50.80 cm to 55.88 cm, the proposed fabrication tolerances can be met, and the fuel can be qualified for HFIR conditions.

We report the results of an experiment conducted near the High Flux Isotope Reactor of Oak Ridge National Laboratory, designed to address the question of whether a flux of reactor-generated electron antineutrinos ( ν ¯ e ) can alter the rates of weak nuclear interaction induced decays of 54Mn, 22Na, and 60Co. This experiment has small statistical errors but, when systematic uncertainties are included, has null results. Perturbations greater than one part in 104 are excluded at 95% confidence level in β ± decay and electron capture processes, in the presence of an antineutrino flux of 3 × 1012 cm−2s−1. The present experimental methods are applicable to a wide range of radionuclides. Improved sensitivity in future experiments can be anticipated as we continue to better understand and reduce the dominant systematic uncertainties.

Neutron irradiation in mixed spectrum reactors is an effective approach to investigate the synergistic effects of solid transmutations and atomic displacement damage in tungsten. In this article the findings and interpretations from a large-scale tungsten irradiation campaign conducted using the High Flux Isotope Reactor of Oak Ridge National Laboratory are summarized. The response of originally-unalloyed tungsten to mixed spectrum neutron irradiation is characterized by enormous hardening, degradation of modulus of toughness eventually leading to embrittlement, and decreased thermal conductivity. These property changes may be attributed primarily to production, segregation, and precipitation of rhenium and osmium and assisted by displacement damage. The stages describing the evolution of the microstructural development and property changes with the neutron dose and the accompanying accumulation of transmutation products are proposed. This manuscript has been co-authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).

PubMed: 30978655, 2-s2.0-85064014804, Tungsten-188 (t1/2 = 69.4 d) is routinely produced by double neutron capture using highly enriched 186W target, 186W(n,?)187W(n,?)188W reaction, at the ORNL 85 MWt High Flux Isotope Reactor. While the thermal neutron cross section for the first reaction, 186W(n,?)187W, is well known, the single reported 64 b cross-section for the second reaction, 187W(n,?)188W, cannot be validated by experimental results that yield lower than expected activities of 188W. In this study, we report a new value for the thermal neutron capture cross section of 187W. After confirming the neutron capture cross section of 186W (?0 = 37.8 ± 1.8 b for thermal and I0 = 476 ± 25 b for resonance integrals with ?0/I0 = 12.6 ± 0.4) in two short irradiations, longer irradiations (1–10 d) were performed to obtain a value of 6.5 ± 0.8 b for the ?0 of 187W, which is lower than the adopted value by a factor of 10. Due to the short half-life of 187W (t1/2 = 23.7 d), the ?0 for 187W was obtained empirically by comparing the 188W experimental yields with the theoretical yields generated by code IsoChain and varying the 187W cross section while keeping all other parameters constant. © 2019, U.S. Department of Energy, USDOE Nuclear Physics, NP: DE-AC05-00OR22725 Türkiye Bilimsel ve Teknolojik Araştirma Kurumu, TÜBITAK: 1059B141600608, This research was supported by DOE , Office of Nuclear Physics, Isotope Program, under contract DE-AC05-00OR22725 and TÜBITAK (The Scientific and Technological Research Council of Turkey) and Project Number: 1059B141600608 . The authors acknowledge the efforts and support of the High Flux Isotope Reactor staff, especially Greg Hirtz, for scheduling the irradiations of the targets, and staff of Nuclear and Radiochemistry Group for help in many aspects of this project, especially Allison Peacock and Lance Wyant for handling the irradiated targets in the hot cell. The authors thank James Gaugler II and Riley Hunley for their critical review of the manuscript.

To collect data for fusion applications and understand the basic properties of tungsten, single-crystal tungsten was neutron irradiated in the mixed-spectrum High Flux Isotope Reactor at the Oak Ridge National Laboratory at temperatures of 90–830 °C to fast fluences of 0.01–9 × 1025 n/m2 (E > 0.1 MeV). For tensile tests at room temperature of the irradiated material in both orientations, and tensile orientation, initially there was strengthening that peaked at 0.02 dpa and was followed by progressive modulus of toughness reduction, approaching zero at higher doses. For all irradiation temperatures, in elevated temperature tensile tests there was a distinct transition from ductile-to-brittle behavior between 0.1 and 0.4 dpa, accompanied by an increase in indentation hardness. The ductile-to-brittle transition with increasing dose was particularly critical because it presented as a total loss in elongation and modulus of toughness. The critical transition dose was well below the dose (∼1 dpa) where irradiation-induced precipitates are visible in the TEM. The extent of Vickers microhardness increase was significant at higher doses and did not depend on irradiation temperature or crystal orientation, reaching 12.9 GPa after 2.8 dpa. The significant mechanical property degradation above 0.1 dpa is believed to have been caused by the accumulation of irradiation-induced clusters and eventually precipitates of the transmutation elements Re and Os.

Zircaloy-2 and Zircaloy-4 were neutron irradiated at 358 °C in the high flux isotope reactor (HFIR) to a neutron fluence of 29.6 × 1024 n/m2 (E > 1 MeV) and the resultant irradiation hardening was measured by tensile testing. Irradiation at the relatively high temperature of 358 °C resulted in about 25–45% less hardening than observed in the literature for irradiations at 260–326 °C. The lower irradiation hardening was shown to result from a coarser loop distribution. The measured irradiation hardening was closely related to the 〈a〉 loop size and number density (ND) using an Orowan hardening model when the loops were assumed to be strong barriers like voids. In this work Atom Probe Tomography (APT) was used to detect the clustering of Fe, Sn, and Cr at features consistent with loops. The tendency for clustering of Fe, Sn, and Cr at loops could result in the apparent high barrier strength for these features. These clusters are also an additional hardening barrier. However, local variation in the distribution of clusters is observed from region to region in the irradiated material that appears to be related to factors such as the proximity to precipitates, local variations in microstructure, and/or microchemistry. Keywords: Zircaloy, Irradiation Effects, Hardening, Clustering

H-Canyon at Savannah River Site has started dissolving High Flux Isotope Reactor (HFIR) fuel as part of the Spent Nuclear Fuel (SNF) processing campaign. Each HFIR fuel core contains inner and outer fuel elements fabricated from uranium oxide (U3O8) dispersed in a continuous Al phase. Fuels fabricated in this manner, like other SNF’s processed in H-Canyon, dissolve by the same general mechanisms with similar gas generation rates including the production of H2. The objective of this work was to identify flowsheet conditions through literature review and laboratory experimentation to safely and efficiently dissolve the HFIR fuel in H-Canyon. The work showed that a full HFIR core could be dissolved using nominally 0.002 M Hg to catalyze the dissolution and the margin between the predicted H2 concentration and the calculated Lower Flammability Limit (LFL) was greater when the dissolving solution was allowed to boil for 45 min prior to initiating the Hg addition.

In this paper, we describe the 147Pm production yields and level of impurities from several targets that consisted of milligram quantities of highly enriched 146Nd oxide irradiated at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory for durations ranging from 24 to 180 h. A comparison between theoretical and experimental data are also presented, and attempts were made to empirically evaluate the neutron capture cross-sections of 41.3-d 148mPm and 5.4-d 148gPm. For a one-cycle irradiation (~24 days), 147Pm yield reaches a maximum value of 101.8 MBq/mg (2.75 mCi/mg) at 60 days after the end of bombardment. Because of large neutron capture cross-sections of 147Pm, the yield of 147Pm does not significantly increase with longer irradiation. Our estimates of the thermal neutron capture cross-section and resonance integral for 146Nd at 1.48 ± 0.05 b and 2.56 ± 0.25 b, respectively, were consistent with the reported values. The effective neutron capture cross-section of 147Pm to 148mPm was 53.3 ± 2.7 b–a factor of 2 lower than the 98.7 ± 6.5 b calculated from reported cross-sections. The measured σeff to the ground state (5.37-d 148gPm) was 82.0 ± 4.1 b; ~34% lower than the value of 139 ± 10 b calculated from reported cross-sections. In this work, we also describe the development of a chemical process based on extraction and ion-exchange chromatography for separation of 147Pm from milligram quantities of 146Nd and other impurities. Sequential separation of Pm from the Nd target and from other radioisotopic impurities (153Gd and 154&155Eu, 192Ir, and 60Co) was achieved using a LN extraction resin in HCl media followed by further purification of Pm from 60Co and 192Ir using a low cross-linking cation exchange resin. Based on these data, we estimated that two rounds of purification under our experimental conditions can provide a mass separation factor of >104 between Pm and Nd. Our data indicate that curie quantities of 147Pm with suitable chemical and radioisotopic purity for applications in beta voltaic batteries can be produced by irradiating gram quantities of highly enriched 146Nd in the flux trap of HFIR for one cycle.

Transmutation-induced precipitation in neutron-irradiated tungsten is an important performance concern for its application as plasma facing material in fusion reactors. In this study, segregation and precipitation of transmutant elements in single crystal and polycrystal tungsten irradiated at 460–1100 °C to 0.02–2.4 displacements per atom (dpa) in the High Flux Isotope Reactor were investigated using transmission electron microscopy. The results indicated that nanoscale W-Re-Os clusters were identified in the low dose regime from 0.02 to 0.44 dpa with irradiation temperature lower than 800 °C while acicular-shape precipitates formed when irradiation dose is higher than 1.5 dpa. A tentative roadmap of the kinetics process of the transmutation-induced precipitation in neutron-irradiated tungsten is presented characterizing the defect features (i.e., W-Re-Os clusters and precipitates) consisting of transmutant elements in tungsten irradiated to various doses. All TEM-visible voids were associated with the acicular-shape precipitates. Voids were formed prior to the formation of acicular-shape precipitates and act as strong trapping sites for mobile species involved in the precipitation together with dislocations. Thermal stability of W-Re-Os clusters was assessed by performing a 2-h anneal at 1200 °C on tungsten irradiated to 0.44 dpa at 705 °C. The kinetics process of transmutant elements and radiation defects are discussed to reveal the underlying mechanisms controlling the formation of precipitates in tungsten.

Neutrons have historically been used for a broad range of biological applications employing techniques such as small-angle neutron scattering, neutron spin echo, diffraction, and inelastic scattering. Unlike neutron scattering techniques that obtain information in reciprocal space, attenuation-based neutron imaging measures a signal in real space that is resolved on the order of tens of micrometers. The principle of neutron imaging follows the Beer-Lambert law and is based on the measurement of the bulk neutron attenuation through a sample. Greater attenuation is exhibited by some light elements (most notably, hydrogen), which are major components of biological samples. Contrast agents such as deuterium, gadolinium, or lithium compounds can be used to enhance contrast in a similar fashion as it is done in medical imaging, including techniques such as optical imaging, magnetic resonance imaging, X-ray, and positron emission tomography. For biological systems, neutron radiography and computed tomography have increasingly been used to investigate the complexity of the underground plant root network, its interaction with soils, and the dynamics of water flux in situ. Moreover, efforts to understand contrast details in animal samples, such as soft tissues and bones, have been explored. This manuscript focuses on the advances in neutron bioimaging such as sample preparation, instrumentation, data acquisition strategy, and data analysis using the High Flux Isotope Reactor CG-1D neutron imaging beamline. The aforementioned capabilities will be illustrated using a selection of examples in plant physiology (herbaceous plant/root/soil system) and biomedical applications (rat femur and mouse lung).

The Oak Ridge National Laboratory High Flux Isotope Reactor (HFIR) is an 85 MWt flux trap-type research reactor that supports key research missions, including isotope production, materials irradiation, and neutron scattering. The core consists of an inner and an outer fuel element containing 171 and 369 involute-shaped plates, respectively. The thin fuel plates consist of a U3O8-Al dispersion fuel (highly enriched), an aluminum-based filler, and aluminum cladding. The fuel meat thickness is varied across the width of the involute plate to reduce thermal flux peaks at the radial edges of the fuel elements. Some deviation from the designed fuel meat shaping is allowed during manufacturing. A homogeneity scan of each fuel plate checks for potential anomalies in the fuel distribution by scanning the surface of the plate and comparing the attenuation of the beam to calibration standards. While typical HFIR simulations use homogenized fuel regions, explicit models of the plates were developed under the Low-Enriched Uranium Conversion Program. These explicit models typically include one inner and one outer fuel plate with nominal fuel distributions, and then the plates are duplicated to fill the space of the corresponding fuel element. Therefore, data extracted from these simulations are limited to azimuthally averaged quantities. To determine the reactivity and physics impacts of an as-built outer fuel element and generate azimuthally dependent data in the element, 369 unique fuel plate models were generated and positioned. This model generates the three-dimensional (i.e., radial–axial–azimuthal) plate power profile, where the azimuthal profile is impacted by features within the adjacent control element region and beryllium reflector. For an as-built model of the outer fuel element, plate-specific homogeneity data, 235U loading, enrichment, and channel thickness measurements were translated into the model, yielding a much more varied azimuthal power profile encompassed by uncertainty factors in analyses. These models were run with the ORNL-TN and Shift Monte Carlo tools, and they contained upwards of 500,000 cells and 100,000 unique tallies.

The mission of the Neutron Sciences Directorate (NScD) at the U.S. Department of Energy’s Oak Ridge National Laboratory (ORNL) is the undertaking of high-impact research into the structure and properties of materials across the spectrum of biology, chemistry, physics, materials science, and engineering. NScD operates two world-leading neutron scattering facilities: the High Flux Isotope Reactor (HFIR) and the Spallation Neutron Source. HFIR achieved full power in 1966, and over a half century later, it continues to serve a variety of national missions. HFIR provides one of the highest steady-state neutron fluxes of any research reactor in the world to support scientific missions including cold and thermal neutron scattering, isotope production, and materials irradiation research. To sustain leadership in neutron sciences into the future, ORNL is exploring areas in which HFIR can be improved to enhance its performance. Many improvement areas are being explored including upgrading the cold source and neutron scattering facilities. The improvement areas discussed herein include replacing the reactor pressure vessel, upgrading the neutron reflector, and ensuring that reactor performance is maintained or enhanced after converting from high-enriched uranium to low-enriched uranium fuel.

Engineering design studies are underway to assess the feasibility of converting the High Flux Isotope Reactor (HFIR) to operate with low-enriched uranium silicide dispersion (LEU3Si2-Al) fuel. These studies are supported by the U.S. Department of Energy National Nuclear Security Administration’s Office of Material Management and Minimization. A systematic approach employing neutronic and thermal-hydraulic analyses has been performed with the ORNL Shift and HFIR Steady State Heat Transfer Code tools, respectively, to predict reactor performance and thermal safety margins for proposed LEU3Si2-Al fuel designs. The design process was initiated by generating an optimized design with fabrication features identified from previous studies that result in excellent performance and safety metrics. The approach continued by substituting a single fabrication feature anticipated to be difficult to manufacture with another feature expected to perform an analogous function to that of the removed feature. Four conceptual fuel element design candidates, with various fabrication features, for conversion of HFIR with 4.8 gU/cm3 LEU3Si2-Al fuel have been generated and shown to meet pre-defined performance and safety metrics. Results to date indicate that HFIR could convert with the subject fuel system and meet performance and safety requirements if, among other considerations, fabrication of the specific design features are demonstrated and qualification of the fuel is complete under HFIR-specific conditions.

Neutron crystallography is a structural technique that allows determination of hydrogen atom positions within biological macromolecules, yielding mechanistically important information about protonation and hydration states while not inducing radiation damage. X-ray diffraction, in contrast, provides only limited information on the position of light atoms and the X-ray beam rapidly induces radiation damage of photosensitive cofactors and metal centers. Presented here is the workflow employed for the IMAGINE and MaNDi beamlines at Oak Ridge National Laboratory (ORNL) to obtain a neutron diffraction structure once a protein crystal of suitable size (> 0.1 mm3) has been grown. We demonstrate mounting of hydrogenated protein crystals in quartz capillaries for neutron diffraction data collection. Also presented is the vapor exchange process of the mounted crystals with D2O-containing buffer to ensure replacement of hydrogen atoms at exchangeable sites with deuterium. The incorporation of deuterium reduces the background arising from the incoherent scattering of hydrogen atoms and prevents density cancellation caused by their negative coherent scattering length. Sample alignment and room temperature data collection strategies are illustrated using quasi-Laue data collection at IMAGINE at the High Flux Isotope Reactor (HFIR). Furthermore, crystal mounting and rapid freezing in liquid nitrogen for cryo-data collection to trap labile reaction intermediates is demonstrated at the MaNDi time-of-flight instrument at the Spallation Neutron Source (SNS). Preparation of the model coordinate and diffraction data files and visualization of the neutron scattering length density (SLD) maps will also be addressed. Structure refinement against neutron data-only or against joint X-ray/neutron data to obtain an all-atom structure of the protein of interest will finally be discussed. The process of determining a neutron structure will be demonstrated using crystals of the lytic polysaccharide monooxygenase Neurospora crassa LPMO9D, a copper-containing metalloprotein involved in the degradation of recalcitrant polysaccharides via oxidative cleavage of the glycosidic bond.

The Oak Ridge National Laboratory (ORNL) has developed and tested a novel system architecture for acquiring high fidelity high-speed data. The approach uses a consumer grade audio recording device that is normally associated with “garage band” recording of music. ORNL has coupled this low-cost data acquisition hardware with computing technology running open-source software. The main advantage of this approach is per-channel cost; an instrument grade data acquisition system typically costs between $800 to $2000 per channel compared to less than $50 per channel for these consumer grade components. Three systems, each featuring four channels, have been deployed for acquiring data from geophones and the electrical supply system that supports the High Flux Isotope Reactor (HFIR) and the Radiochemical Engineering Development Center (REDC) at ORNL. Each channel samples at 96 kHz at 24-bit resolution. The deployed systems operate continuously 24/7 and produce about 4 terabytes of data per month per system. This paper provides a technical overview of this approach, its implementation, and some preliminary results from qualification testing. This work was conducted in support of the Multi-Informatics for Nuclear Operations Scenarios (MINOS).

Nuclear spin-polarized 3He is widely used in many scientific areas. One of the applications is used as a neutron spin filter to polarize neutrons. Among all the neutron polarizing techniques, nuclear-spin-polarized 3He neutron spin filters have shown great flexibility and versatility because of its highly spin-dependent neutron absorption cross section, large neutron acceptance angle and working over a broad neutron wavelength band. At the Oak Ridge National Laboratory, 3He is routinely polarized via spin-exchange optical pumping (SEOP). Over the last several years, various SEOP-based systems have been developed to suit the needs of different neutron instruments at the Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR). Particularly, much effort has been put in developing in situ systems to address the problem caused by 3He polarization decay in the widely used “drop-in cell” setup. Because most instruments at SNS and HFIR have very limited space, the in situ system development has been focused on having a compact form factor design tailored to each individual beamline while still achieving high 3He polarization. We report the development of polarized 3He neutron spin filters at ORNL.