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RuN6CrF6 is Halite, Rock Salt structured and crystallizes in the cubic Pa-3 space group. The structure is zero-dimensional and consists of four chromium hexafluoride molecules and four hexaami-noruthenium molecules.
N2SF6 crystallizes in the trigonal P-3m1 space group. The structure is zero-dimensional and consists of two ammonia molecules and one sulfur hexafluoride molecule.
UF6N2(NF)2 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of eight ammonia molecules, eight monofluoroamine molecules, and four uranium hexafluoride molecules.
(WF6)2(N2)3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is zero-dimensional and consists of twelve ammonia molecules and four tungsten hexafluoride molecules.
ReF6 is beta Np structured and crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of four rhenium hexafluoride molecules. Re6+ is bonded in an octahedral geometry to six F1- atoms. All Re–F bond lengths are 1.87 Å. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Re6+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Re6+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one Re6+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one Re6+ atom.
CrF6CrCu3(O2F)6 crystallizes in the triclinic P-1 space group. The structure is three-dimensional and consists of one chromium hexafluoride molecule and one CrCu3(O2F)6 framework. In the CrCu3(O2F)6 framework, Cr is bonded to six F atoms to form CrF6 octahedra that share corners with six CuO4F2 octahedra. The corner-sharing octahedra tilt angles range from 33–52°. There are a spread of Cr–F bond distances ranging from 1.85–1.89 Å. There are three inequivalent Cu sites. In the first Cu site, Cu is bonded to four O and two equivalent F atoms to form CuO4F2 octahedra that share corners with two equivalent CrF6 octahedra. The corner-sharing octahedral tilt angles are 39°. There is two shorter (1.90 Å) and two longer (1.91 Å) Cu–O bond length. Both Cu–F bond lengths are 2.28 Å. In the second Cu site, Cu is bonded to four O and two equivalent F atoms to form CuO4F2 octahedra that share corners with two equivalent CrF6 octahedra. The corner-sharing octahedral tilt angles are 33°. All Cu–O bond lengths are 1.92 Å. Both Cu–F bond lengths are 2.22 Å. In the third Cu site, Cu is bonded to four O and two equivalent F atoms to form CuO4F2 octahedra that share corners with two equivalent CrF6 octahedra. The corner-sharing octahedral tilt angles are 52°. All Cu–O bond lengths are 1.90 Å. Both Cu–F bond lengths are 2.39 Å. There are six inequivalent O sites. In the first O site, O is bonded in a 2-coordinate geometry to one Cu and one O atom. The O–O bond length is 1.29 Å. In the second O site, O is bonded in a 2-coordinate geometry to one Cu and one O atom. In the third O site, O is bonded in a 2-coordinate geometry to one Cu and one O atom. The O–O bond length is 1.29 Å. In the fourth O site, O is bonded in a 2-coordinate geometry to one Cu and one O atom. In the fifth O site, O is bonded in a 2-coordinate geometry to one Cu and one O atom. The O–O bond length is 1.29 Å. In the sixth O site, O is bonded in a 2-coordinate geometry to one Cu and one O atom. There are three inequivalent F sites. In the first F site, F is bonded in a distorted bent 150 degrees geometry to one Cr and one Cu atom. In the second F site, F is bonded in a bent 150 degrees geometry to one Cr and one Cu atom. In the third F site, F is bonded in a distorted bent 120 degrees geometry to one Cr and one Cu atom.
Los Alamos National Laboratory’s (LANL’s) compliance with Radionuclide NESHAP 1 regulations is managed by the Radionuclide Air Emissions Management (RAEM) team, part of LANL’s Compliance Programs group (EPC-CP). One area of the Radionuclide NESHAP addresses requirements for siting a stack sample system. This memo documents the most recent performance tests of the sulfur hexafluoride detectors for use in stack gas mixing tests, as well as the functional trending test on a pair of optical particle counters, comparing results from a non-calibrated instrument to a calibrated instrument.
Commercial light-water reactor (LWR) operators and fuel vendors are pursuing advancements in fuel and reactor design that include increasing 235 U enrichment from low enrichment (<5 wt.% 235 U) to low-enriched uranium+ (LEU+) (10 wt.% > 235 U > 5 wt.%) and high-assay low-enriched uranium (HALEU) (20 wt.% > 235 U > 10 wt.%). These advancements will necessitate the ability to transport LEU+ and HALEU fuel materials. Assessment of Existing Transportation Packages for Use with HALEU(ORNL/TM-2020/1725) assesses the potential to use currently licensed transportation packages for the transportation of HALEU by evaluating a representative package for each uranium fuel form category (for example, oxide and/or metal in fuel assemblies, fuel pins, powder, pellets, and uranium hexafluoride [UF 6 ].) This report expands on the UF 6 analysis.
With the increasing international interest in using nuclear material as sources of energy, comes the growing concern that we may see an increase in proliferation threats. Uranium hexafluoride (UF 6 ) is used in the nuclear fuel cycle for uranium enrichment. Inspectors from the International Atomic Energy Agency (IAEA) monitor the enrichment levels of UF 6 stored in transportation cylinders, to ensure the enrichments match that of a facility operator’s declarations. However, only a characteristic subset of UF 6 cylinders can be measured by inspectors from the IAEA during these inspections. In turn, the inspector may not identify a cylinder whose enrichment levels do not match the facility declarations. Therefore, our team attempts to develop a machine learning network that could determine the enrichment percentage of cylinders as they enter and exit facilities. The machine learning model must be robust against spectral variations due to factors that are internal and external to the UF 6 cylinder. Such factors include but are not limited to the speed and distance of the moving vehicle, cylinder type, cylinder orientation, and fill level. Many features in the spectral continuum can be used to identify and correct for some of these variations. As a consequence, the model must extract numerous features in the continuum. We investigate new approaches in continuum subtraction to verify enrichment percentage: interpolation and extrapolation of lines at the notable characteristic spectral peaks. It was determined that there was no clear answer on which method proved superior, therefore the decision was made to implement both new methods into the current codebase. We currently rely on synthetic training and testing data to analyze the results and fine tune our models but hope to test the system on measured data soon.
A team at Oak Ridge National Laboratory tested various barcode sizes, materials, surface finishes, and marking techniques to determine suitable direct part marking techniques and barcode specifications for a new uranium hexafluoride (UF 6 ) cylinder global identifier. This paper describes testing those variables at different read distances and angles with several commercial off-the-shelf direct part mark or barcode readers. This research concluded that a 1.4 in. 2D Data Matrix barcode with a 0.1 in. quiet zone would be appropriate for the machine-readable feature on the proposed UF 6 cylinder global identifier. Testing suggests that this size barcode could be read from an angle of up to 30° over the range of 10–100 cm using multiple commercial off-the-shelf handheld direct part mark or barcode readers. Testing also suggested that barcodes marked on ball-blasted stainless steel with CerMark laser marking ink may be a good choice for the proposed UF 6 cylinder global identifier because they exhibited high contrast and were readable from a desirable range of distances and angles.
I’m nominating Shannon Blair from the Sustainability Program and Michael Moss from Pollution Prevention Program for the DOE Outstanding Sustainability Program/Project Award for their efforts in reducing sulfur hexafluoride (SF6) emissions at Los Alamos National Laboratory (LANL) and creating a system of accounting for improved tracking of SF6 emissions in the future.
I’m nominating Shannon Blair from Los Alamos National Laboratory’s (LANL) Sustainability Program and Michael Moss from LANL’s Pollution Prevention Program for the Phil Wirdzek Leadership Award for their efforts in reducing sulfur hexafluoride (SF 6 ) emissions at LANL and creating a system of accounting for improved tracking of SF 6 emissions in the future.
The U.S. Nuclear Regulatory Commission (NRC) is preparing for anticipated licensing applications requesting fuel enrichments of UO 2 ceramic fuels enriched in excess of 5 weight percent (w/o) 235 U for commercial light-water reactors (LWRs). PNNL has been tasked with providing technical assistance to the NRC related to the review and approval of requests for enrichment increases above the current 5 w/o 235 U enrichment limit. This report will provide the agency with technical assistance to enhance the staff’s knowledge base and to identify developmental needs required to support the licensing of greater than 5 w/o UO 2 ceramic fuels. This report provides a background on increasing enrichment of UO 2 LWR fuel beyond 5 w/o 235 U. The primary concern of increasing enrichment is the impacts to criticality safety. This report will focus on criticality safety as it relates to enrichment, conversion of uranium hexafluoride to UO 2 , fuel assembly fabrication, transportation of fresh/spent fuel assemblies, reactor operations, and storage of fresh/spent fuel assemblies. The report provides a general summary of each of the steps in the UO 2 fuel cycle starting from transportation of enriched UF 6 through dry cask storage of spent fuel assemblies. This report also discusses other impacts of increased enrichment during reactor operation and the surrounding fuel cycle activities. Current needs regarding both data and analytical codes to support the increase above 5 w/o 235 U are identified and discussed.
Los Alamos National Laboratory’s (LANL’s) compliance with Radionuclide NESHAP0F 1 regulations is managed by the Radioactive Air Emissions Management (RAEM) team, part of LANL’s Compliance Programs group (EPC-CP). One area of the Radionuclide NESHAP addresses requirements for siting a stack sample system. Prior to commissioning a new stack sampling system, the ANSI Standard for stack sampling requires that the stack sample location must meet several criteria, including uniform mixing of tracer gas (sulfur hexafluoride, SF 6 ) and tracer aerosol (liquid oil droplets) in the air stream. This memorandum will specifically focus on the tracer gas portion of the ANSI Standard. For these mix tests, tracer gas is injected into the stack air stream and the resulting air concentrations are measured across the plane of the stack at the proposed sampling location. The coefficient of variation of the media concentration must be under 20% when evaluated over the central 2/3 area of the stack or duct.
This primary purpose of this project was to evaluate alternative gas mixtures to sulfur hexafluoride (SF6) developed for high voltage power delivery applications for use in high voltage spark gap switches. These SF6 alternatives lower global warming potential emissions and enable improvements to the pressure-voltage design space. A combined experimental, computational, and theoretical study was used to quantify the impact of persistent breakdown products on the breakdown distribution of SF6-replacement gas mixtures. Viable SF6 replacements suitable for use in spark gap switches were studied to enable performance and agility improvements for next-generation pulsed power research relevant to national security missions. Experimental campaign included establishing parameters of switch gases as function of concentration. Various concentrations and pressures were tested for trends in breakdown voltage, repeatability, and durability, and breakdown constituents. A zero-dimensional plasma global model was used to simulate the plasma arc decay and recombination process in spark-gap switches relevant to the Z machine. Finally, a complete and consistent set of electron-neutral collision cross-sections for the novel insulating gas C4F7N is reported.
The physical and chemical transformation during atmospheric transport of radionuclides released into the environment has the possibility of impacting consequence modeling results. Accordingly, this report identifies physical and chemical transformations that may occur following release of chemically reactive radioactive species, how those transformations may affect modeling of consequences of release to the atmosphere and identifies current capabilities – in both MACCS and other state-of-practice atmospheric transport and dispersions models– to model those transformations. It was found that the inclusion of physical and chemical transformations is currently very limited in current state-of-practice codes for atmospheric dispersion of radionuclides. State-of-practice atmospheric dispersion codes appear to be typically limited to simulating either physical-chemical transformations or radioactive transformations, but not both. A state-of-practice atmospheric dispersion code capable of performing parallel physical, chemical, and radioactive transformation was not identified. A few atmospheric dispersion codes capable of modeling physical and chemical transport of specific species such as tritium or uranium hexafluoride were identified. Consequently, there is currently no information available that clearly suggests updates to the MACCS code are needed to bring it up to state-of-practice. However, investigations concluded that the MACCS computational framework can currently accommodate multiple physical/chemical forms in one simulation. Additionally, with some major assumptions, the computational framework in MACCS can accommodate parallel physical-chemical and radioactive transformations.
Depleted uranium hexafluoride (UF 6 ), a stockpiled byproduct of the nuclear fuel cycle, reacts readily with atmospheric humidity, but the gas-phase reaction mechanism and associated chemical kinetics are poorly understood. During the performance period we undertook development of a state-of-the-art ab initio gas-phase chemical kinetics simulation workflow to model the hydrolysis of uranium hexafluroride (UF 6 ). In doing so, we addressed several outstanding issues in the theoretical treatment of uranium-containing systems. At the outset it was unclear how to generate accurate estimates of kinetic and thermodynamic data for U-containing chemical reactions. Generation of such data has been made routine. Prior to our work, the literature associated with UF 6 hydrolysis were disparate and inaccurate. This body of work provides a modern and comprehensive theoretical assessment of the reaction mechanism, molecular clustering towards deposition, and chemical kinetics. New methodological implementations and software integrations resulting from this work are also highlighted. As much as possible, our predictions were validated against experimental data including particle morphologies, vibrational spectroscopy, atomization enthalpies, and kinetic rate constants. Nevertheless, we were unable to reconcile kinetic measurements with high-accuracy simulations.
Our project explores a new solution to complement current safeguards toolbox by independently, and noninvasively, determining the pressure inside uranium hexafluoride (UF 6 )-carrying Gas Centrifuge Enrichment Plant (GCEP) pipes. Proof-of-principle, non-invasive pipe pressure monitoring tests were conducted through measurements of hoop and axial strain using an optical-interference dilatometry technique based on fiber Bragg gratings (FBGs) inscribed in the core of telecommunication-type 125 µm diameter optical fibers. The fibers were affixed to commercial stainless steel and aluminum tubes and pipes of the type expected to be found at GCEP’s, each measuring four inches in diameter. When the internal air pressure in the pipes changes their external diameter and length follow, and the pitch in the FBG shrinks and/or expands accordingly. In turn, these changes result in a shift of the light wavelength reflected by the FBGs. Several FBGs physically attached to the pipe, as well as control FBGs not attached, were interrogated during the process using state-of-the-art commercial interrogators that operate on swept-wavelength laser technology. Strains measured were contrasted against calculations based on the known elastic and mechanical properties of the pipes. Good agreement is found, and strategies are proposed for further improvement of the experimental resolution as well as future implementation of this novel approach for GCEP safeguards.