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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Improved Hybrid Modeling of Spent Fuel Storage Facilities

This work developed a new computational method for improving the ability to calculate the neutron flux in deep-penetration radiation shielding problems that contain areas with strong streaming. The “gold standard” method for radiation transport is Monte Carlo (MC) as it samples the physics exactly and requires few approximations. Historically, however, MC was not useful for shielding problems because of the computational challenge of following particles through dense shields. Instead, deterministic methods, which are superior in term of computational effort for these problems types but are not as accurate, were used. Hybrid methods, which use deterministic solutions to improve MC calculations through a process called variance reduction, can make it tractable from a computational time and resource use perspective to use MC for deep-penetration shielding. Perhaps the most widespread and accessible of these methods are the Consistent Adjoint Driven Importance Sampling (CADIS) and Forward-Weighted CADIS (FW-CADIS) methods. For problems containing strong anisotropies, such as power plants with pipes through walls, spent fuel cask arrays, active interrogation, and locations with small air gaps or plates embedded in water or concrete, hybrid methods are still insufficiently accurate. In this work, a new method for generating variance reduction parameters for strongly anisotropic, deep penetration radiation shielding studies was developed. This method generates an alternate form of the adjoint scalar flux quantity, Φ Ω , which is used by both CADIS and FW-CADIS to generate variance reduction parameters for local and global response functions, respectively. The new method, called CADIS-Ω, was implemented in the Denovo/ADVANTG software. Results indicate that the flux generated by CADIS-Ω incorporates localized angular anisotropies in the flux more effectively than standard methods. CADIS-Ω outperformed CADIS in several test problems. This initial work indicates that CADIS- may be highly useful for shielding problems with strong angular anisotropies. This is a benefit to the public by increasing accuracy for lower computational effort for many problems that have energy, security, and economic importance.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Final Technical Report

Southern Africa is the world’s largest emitter of biomass burning aerosols. Their westward transport over the remote southeast Atlantic ocean colocates some of the largest atmospheric loadings of absorbing aerosol with the least examined of the Earth’s major subtropical stratocumulus decks. Global aerosol model results highlight that the largest positive top-ofatmosphere forcing in the world occurs in the southeast Atlantic, but this region exhibits large differences in magnitude and sign between reputable models, in part because of high variability in the underlying model cloud distributions. Many uncertainties contribute to the highly variable model radiation fields: the aging of the shortwave-absorbing aerosol during transport, how much of the aerosol mixes into the cloudy boundary layer, and how the low clouds adjust to smokeradiation and smoke-cloud interactions. In addition, the ability of the biomass burning aerosol to absorb shortwave radiation is known to vary seasonally as the fuel type on land changes. LASIC (Layered Atlantic Smoke Interactions with Clouds) is a strategy to improve our understanding of aged carbonaceous aerosol, its seasonal evolution, and the mechanisms by which clouds adjust to the presence of the aerosol. The observational strategy centers on deploying the AMF1 cloud, aerosol, and atmospheric profiling instrumentation to Ascension Island, located within the trade-wind shallow cumulus regime (14.50W, 80S) 3000 km offshore of continental Africa. The location is within the latitude zone of the maximum outflow of aerosol, with the deepening boundary layer known to entrain free-tropospheric smoke. The primary activities for LASIC are: 1) to improve current knowledge on aged biomass burning aerosol and its radiative properties as a function of the seasonal cycle; 2) to use surface-based remote sensing to sensitively interrogate the atmosphere for the relative vertical location of aerosol and clouds; 3) to improve our understanding of the cloud adjustments to the presence of shortwave-absorbing aerosol within the vertical column, both through aerosol-radiation and through aerosol-cloud interactions; 4) to aid low cloud parameterization efforts for climate models. The measurements span June 1, 2016 - October 31, 2017, encompassing two July-October biomass burning seasons. The August-September, 2016, months include an Intensive Observing Period (IOP) with 8x/daily radiosondes. In 2017, from 16 August through 7 September, the UK FAAM Bae- 146 plane was deployed from Ascension, providing complementary data on the atmosphere’s vertical structure as part of the CLARIFY project, with similar scientific goals. The NASA ORACLES aircraft campaign, sharing similar objectives to LASIC, deployed from Namibia in September, 2016, and Sao Tome in August, 2017. The latter included a suitcase flight to Ascension spanning August 18-21. In 2017 a CAPS-SSA instrument belonging to Aerodyne was brought to Ascension, gathering data primarily for August, towards providing a second, independent measurement of aerosol absorption. Ascension Island is also an AERONET site.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Prototype Stilbene Neutron Collar II

A neutron collar using stilbene organic scintillator cells for fast neutron counting is described for the assay of fresh low enriched uranium (LEU) fuel assemblies. The prototype stilbene collar has a form factor similar to standard He-3 based collars and uses an AmLi interrogation neutron source. This report describes the simulation, using a custom LLNL developed MCNPX, of list mode neutron correlation data on various fuel assemblies. Some of these fuel assemblies have neutron absorbers (burnable Gd poisons) and partial defect s (DU, Fe, Pb pins). Calibration curves (doubles vs 235 U linear mass density) are presented for fast (with Cd lining) mode of operation. The modeling incorporates LLNL developed neutron crosstalk correction algorithms and stilbene light output detector response quench function. Pileup issues are addressed using the LLNL code GamGen / RadSrc to estimate the flux of alpha decay gammas from the fuel assemblies on the stilbene cells with and without Pb shielding. One panel of the prototype collar using 10 high-efficiency 4”x2” stilbene cells from Inrad Optics, using LLNL developed technology, has been constructed and calibrated for optimal PSD and data acquisition electronics. Several sources (AmLi, AmBe, Cf, DD, and DT) have been measured with the single panel and the measured data is consistent with the modeling. A novel part of our work was to determine the light output (LO) quench function for the Inrad 4” x 2” stilbene crystals through a LLNL-MCNPX simulation based optimized fitting of the measured LO data.

42 ENGINEERING↗
DOE OSTI2018

Feasibility of Single-sided 3D elemental imaging

We present single-sided 3D image reconstruction and neutron spectrum of non-nuclear material interrogated with a deuterium-tritium neutron generator. The results presented here are a proof-of-principle of an existing technique previously used for nuclear material, applied to non-nuclear material. While we do see excess signatures over background, they do not have the expected form and are currently un-identified.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Defining Fe and H Speciation During Olivine Carbonation Under Highly Reducing Conditions

The overarching goal of this DOE EC project has been to examine the connections among the geochemical behavior of iron, and the extent of hydrogen, methane or carbonate mineral formation during the aqueous alteration of olivine and pyroxene bearing rocks at near surface temperatures and pressures. We used an integrated suite of microscale x-ray scattering and spectroscopic techniques to interrogate the reactivity and progressive alteration of peridotites during water/rock interaction. We also identified microbial communities in alkaline subsurface fluids, and their role in H 2 -consumption and methane production. A third research thrust integrated these themes, and involved measuring the stable isotope composition (δD and δ 13 C) of hydrogen, water and methane from subsurface fluids and our peridotite hydration experiments to determine whether the water-rock reaction pathways (including biologically influenced systems) can be detected and interpreted in-situ.

58 GEOSCIENCES↗
DOE OSTI2014

Determination of battery stability with advanced diagnostics

The increasing demand of lithium ion batteries for vehicle electrification is changing the typical use conditions that batteries may see. Over time, batteries may develop defects that are difficult to detect with traditional measurements. It is also possible that batteries may be left in an unknown state after failure of the monitoring system, loss of communication, or a potentially damaging event (such as an auto accident). It is therefore useful to explore other monitoring and interrogation methods that can better determine the stability of a battery in an unknown state. This work explores the use of electrochemical impedance spectroscopy as a method to determine the stability of batteries by observing changes in the complex impedance measurement as the cell is exposed to abusive conditions. Very dramatic changes to the internal resistance were observed when single cells were exposed to abusive conditions, suggesting that even single frequency impedance measurements could be effective with single cells. However tests on three cell series and parallel strings yielded smaller changes, primarily to the charge transfer resistance, showing that complex impedance measurements are more appropriate as the system increases in complexity. A rapid impedance tool developed at Idaho National Laboratory was tested and compared to traditional potentiostat tools as well. This was shown to yield similar data to the traditional tools, providing a potential method for continuous monitoring of a battery system. It was observed, however, that shifts in the data are difficult to detect in very transient systems.

25 ENERGY STORAGE↗
DOE OSTI2018

Multimodal Nondestructive Dry Cask Basket Structure and Spent Fuel Evaluation

This NEUP-IRP assembled a team from diverse institutions and a diverse set of expertise to examine the problem of assessing the structural health of dry nuclear fuel storage casks, specifically the TN-32 design. With no physical access designed into these storage casks and the high cost and risk associated with opening casks for direct inspection, the technical difficulty of structural assessment of the basket structure and fuel assemblies is high. In response to this challenge, this IRP brought together experts in both traditional and novel NDE methodologies: active acoustics (University of Mississippi), emissions tomography (University of Florida), muon tomography (Oregon State University), and passive-active ultrasonics (University of South Carolina). Further, our industry partners in the Electric Power Research Institute (EPRI) and AREVA provided invaluable insight into technical design details for the cask, practical knowledge of operating parameters at a storage facility, and key relationships that enabled activities unforeseen at the time of the proposed work but were critical in guiding the path of the research. The team decided early in the project that we had a collective goal of laying the technical ground work for practical solutions that could be implemented in the field with reasonable cost, time, and reliability. A fortunate opportunity arose early in this IRP project to obtain access to a new TN-32 cask at Columbiana High Tech. Both acoustics teams were given access for testing concepts in the first year of the project. This ended up providing critical guidance in the design of subsequent laboratory experiments. Specifically, it became clear that the only reliable acoustic pathways to the interior were through the trunnions, base plate, and top ring of the cask. Based on these field tests and discussions about what would be of practical interest, the team as a whole decided a realistic goal was to detect catastrophic failure of a single fuel assembly, or one that was missing. It is clear from this work that the active acoustics / resonance and muon tomography methodologies would be capable of detecting interior structural integrity problems at this level. The other two areas of investigation (emissions tomography and passive/active ultrasonics) would need more testing to determine a successful implementation, but each may also have other applications such as long term monitoring and monitoring during transportation. This IRP project resulted in technical advances with applications that extend beyond the problem at hand, supported the training of 10 graduate students + 1 post doc, 21 publications, and 13 conference presentations. The remainder of this summary highlights significant activities and achievements in each of the methodologies and a brief discussion on how they can be combined to leverage strengths. Active Acoustics The active acoustics team at UM used both linear and non-linear structural resonance methods to infer information about the internal structure of a cask. Significant activities were a set of four field test measurements on a full scale TN-32 cask at the Columbiana Hi Tech facility in Greensboro, NC and the design and fabrication of a 1/6th scale model TN-32 cask for laboratory measurements. A significant set of acoustic data has been acquired on both the full scale and laboratory scale casks. It was determined early in the project that mechanical resonance techniques were not going to be sensitive to small scale (centimeter) cracks and structural defects in the basket structure or fuel assemblies. We were able to ascertain that both the energy and complexity of the resonance spectra were sensitive to “bulk state” of the fuel assemblies – an intact assembly versus a severely degraded assembly. By developing a novel combination of metrics, we are able to measure a statistically significant shift due to one out of the 32 fuel assemblies being either missing or degraded to a point of complete loss of structural coherence (i.e. “rubble”). We believe this combination of resonance metrics is new to the field and will have applications beyond the fuel storage problem. Emissions Tomography The Emissions Tomography team at the University of Florida explored the concept of using scattering of radiation emissions from the stored fuel as method of evaluating the internal structural health of the cask. Due to the need for emissive fuel assemblies and the difficulties of gaining access to storage facilities, this team primarily relied on simulations to inform feasibility. A key question was the flux estimates of neutrons with a small enough number of scattering events to retain spatial information. Some key conclusions from the transmission component of this work are that the number of scattering events falls rapidly with energy – setting a 11MeV threshold, the average number of scattering events is 8∓4. Rough estimates of scanning times using an ideal detector array would be 1 week. The team also explored the case of significant structural failure resulting in a shift of the source material (fuel). The result is that a +/- 2% mass shift results in a detectable (5.13%) shift in the correlated 2 neutron emission counts and thus may be a candidate as an initial survey. Finally, simulations for predicting the azimuthal dependence of the flux based on specific loading patterns were conducted. Due to self-shielding effects of the assemblies, a periodic pattern results and could potentially be used to identify missing or severely degraded assemblies. This work forms a basis for proper detector placement with the goal of optimizing sensitivity. Muon Tomography Muon tomography (MT) is a relatively novel method of interrogating interior structure on a large scale. One of the advantages of this technique is that the exciting energy source (cosmic muons) is ubiquitous and relatively stable in time. Challenging aspects are relatively low flux rates and appropriate detector technologies. The efforts of the muon group at Oregon State University focused on two areas: (1) simulation of various combinations of muon scattering events and detection schemes to assess sensitivities and time scales for image construction and (2) building a prototype muon detection system applicable to the dry storage cask problem as well as many other similar systems. Significant accomplishments in this area are: (1) demonstration that MT is a viable method for detecting missing or severely degraded rod assemblies, (2) a scintillation based detector with 4 panels and 32 channels of position data each were constructed, tested, and calibrated. Testing of the panels using natural muon background and no scattering objects yielded largely expected results – a straight line path for the muon through the four panels. However some anomalies (paths deviating from a line) were also detected. A redesign of the board improved the signal which greatly improved the muon tracking through the panels. Testing with lead bricks as scattering bodies showed a reduction in the coincidence rate with increasing bricks indicating increased scattering events. A refinement of the scintillator detector design resulted in a spatial image resolution of around 2 cm based on lead brick spacing tests lasting 24 hours. Passive/Active Ultrasonics This team at the University of South Carolina investigated the feasibility of combining passive ultrasonics, in which an elastic pulse is generated by a degradation process (such as a crack extending), and active ultrasonics, in which a known excitation is introduced into the structure and detected by an array of transducers. Significant accomplishments in this area include the development of elastic wave propagation simulation in relevant materials, development of diagnostic algorithms, and laboratory testing and validation using laser doppler vibrometry. This group demonstrated the applicability of various non-contact vibration detection methodologies such as air-coupled ultrasonic transducers and scanning laser doppler vibrometry. While passive acoustic emissions monitoring will likely have a role during the transportation of a fuel storage cask, the level of detailed information about the defect generating the event which can be ascertained from the detections in a complex structure remains for future work. Thermography The EPRI team contributed early in the project a series of thermography measurements in which various levels of water pooled in a mock-up canister were analyzed using commercially available infrared imaging technologies. While large levels of water (100 L, ~10 cm deep) were observable in the thermograms, more realistic levels of pooled water (1 L) were not detectable whether localized or distributed.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Extreme Temperature Sample Environment for Materials Research Using Neutron Scattering

Extreme temperatures and non-equilibrium materials are both central to Department of Energy’s (DOE) mission of addressing grand challenges in emerging energy and advanced materials technologies. The goal of this project is to develop and perfect a system for studying materials in extreme and non-equilibrium conditions using neutron scattering. Neutron scattering has many advantages in the study of materials structure including the ability to use isotopic substitution to determine partial structure factors. When used at a pulsed neutron source, the potential for event-based detection can enable a stroboscopic technique to interrogate very short lived metastable states in supercooled liquids. The work performed in this Phase I project included: (i) literature reviews and discussions with beamline scientists to establish key requirements for the instrument, (ii) laboratory-based research at Materials Development, Inc. (MDI) to test design concepts, modify control software and model designs, (iii) feasibility experiments and measurements on a prototype sample at the Spallation Neutron Source, and (iv) analysis of the results and design of the proposed Phase II instrument. The results of the work show that the proposed approach is viable and provides a strong basis for the Phase II instrument design and Phase III commercialization. MDI participated in the DOE Commercialization Assistance Program with the Larta Institute (Larta) to accelerate commercial sales of the instruments. The market research identified a served available market of ~13M including sales to beamlines, university research laboratories, and industrial glass and materials businesses. Over the ca. 10 year product life cycle, MDI expects to sell instruments with a cumulative net present value profit of approximately 5M.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Electrochemical Detection of Single Molecules in Nanogap Electrode Fluidic Devices

The purpose of this project was to gain a fundamental understanding of molecular diffusion in nanogap electrodes and the diffusive behavior of single molecules undergoing electron transfer. Electrochemical methods for single molecule detection have remained elusive due to the vanishingly small currents involved in single molecule electron transfer. Electrochemical detection of single molecules undergoing redox cycling would enable detection of single enzymes, proteins, and DNA strands resulting in new and improved ultrasensitive sensing devices impacting Detection At The Limits research challenge (DATL), supporting needs in DHS and DoD. We attempted to integrate orthogonal validation techniques, Total Internal Reflection Fluorescence Microscopy (TIRF), and molecular simulation to clarify (1) the mechanism leading to current build up due to redox cycling and (2) diffusion and adsorption of single molecules undergoing redox reactions. While creation of nanogap electrodes with transparent windows was ultimately successful in this project (along with TIRF demonstration of single molecule imaging), time and methods constraints did not allow final electrochemical measurements to be coupled for simultaneous interrogation.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Imaging LIDAR through Fog and Dust for Maritime Surveillance

This work supports Airborne Intelligence, Surveillance, and Reconnaissance (ISR) for tactical situational awareness in challenging environments with modified imaging LIDAR (light detection and ranging). LIDAR produces an irradiance-based scene with high, three-dimensional, spatial resolution; differentiating reflecting surfaces and surface textures not just for target detection, but also target recognition. LIDAR is generally prevented from working through all weather; as the traditional source wavelengths are scattered and/or absorbed by fog, clouds, and dust known as degraded visual environments (DVEs). This work identifies and quantifies improved optical wavelength regimes and polarization strategies that should open this otherwise denied operating window for LIDAR. We demonstrate modified imaging LIDAR's utility and ability to produce images in environments that have been challenging for traditional LIDAR (fog, dust) systems. We utilize a state-of-the-art Geiger mode avalanche photodiode (GMAPD) 32X32 detecting array for imaging with an integrated fast timing circuit ROIC per imaging detector pixel. This GMAPD is equivalent to 1024 radar receivers and produces a 3-D point cloud scene for each <lnsec laser interrogation pulse. Through this work, we have demonstrated Sandia's first imaging LIDAR system. We developed significant software to scan the GMAPD array, control data acquisition, and stitch an arbitrary number of images for greater lateral spatial resolution. We designed and built an optical system to evaluate performance, in the laboratory and in field tests, and relate to the performance at tactically important distances. Our use of this system is to study and characterize techniques that extend the range of useful imaging through fog for applications in a maritime environment. We quantify, with simulations, broad wavelength regimes and illuminating polarizations that have benefit in propagating through fog. In particular, we identify circular polarization over broad wavebands as a superior persisting signal technique in extending the useful range of active LIDAR in forward-scattering environments. Finally, we characterize the performance of our LIDAR system and confirm our theoretical predictions in the field and directly evaluate this system as a function of polarization in Sandia's medium-range Fog Tunnel Facility. This technology has potential impacts in improved ISR in maritime environments, but with further development could be revolutionary in tactical ISR by providing real-time three-dimensional full motion video (3D FMV) in DVEs.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Colloid-Facilitated Transport: Studies Related to CFM Project at GTS

Presentation Summary: Insights have been gained as to how to obtain defensible answers to predict radionuclide transport in fractured granites. However, site specific studies still need to be performed to to gain confidence in the prediction; The CFT ladder should be applied to evaluate the potential for enhanced transport with colloids, but most indications are that only very small fractions of strongly-sorbing radionuclides will be capable of CFT over repository time and distance scales; CFT requires very slow desorption from colloids AND very slow filtration of the RN-bearing colloids (relative to time scales of interest); Interrogating such slow processes is a challenge, especially if they are associated with a very small fraction of colloids or very small fraction of sorption sites on colloids (or both); Intuitively, one might expect that stable colloids generated from wasteform degradation that have radionuclides incorporated into their structure (as opposed to asorption association) might pose the biggest risk; Experiments have informed generic modeling approach, including GDSA; Experiments have provided insights into how experimental designs can be tailored and improved to address site-specific and scenario-specific issues; Different host rocks, EBS vs. natural system, and DPC concept can all, in principle, be addressed via different parameterizations of the generic model, with the understanding that parameterizations must be developed through site- and scenario-specific experimental testing

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2019

Neutron Rodeo Phase II Final Report

The ability to perform nondestructive assay (NDA) of fresh fuel assemblies with high precision in reasonable measurement times is significant for nuclear nonproliferation and safeguards. The current methodology used by the International Atomic Energy Agency (IAEA) for NDA of fresh fuel assemblies involves a He-3 based Uranium Neutron Collar (UNCL) system, which is an active coincidence counting system designed to measure time-correlated neutron doubles from induced fissions within the assembly. The UNCL system provides an easily implementable process of quantifying the 235 U linear density of the fresh fuel assemblies; however, operational limitations of the UNCL include long assay times and adverse sensitivity to poisoned assemblies. This has engendered investigation in alternative detector materials for fast-neutron counting to rectify some of these current limitations in the UNCL. The potential improvements of using fast-neutron organic scintillators (e.g. liquid scintillators, stilbene, PSDcapable plastics, etc.) was compared directly to the original Uranium Neutron Collar (UNCL) in-detail during the initial Advanced Neutron Detection Technology Rodeo. The simulation results showed that these alternative detector materials can provide an improvement in the assay time required to reach a suitable precision due to both their lower sensitivity to the interrogation source neutrons (i.e. AmLi neutrons) and their inherently shorter coincidence gate widths. The IAEA has developed a liquid scintillator-based Fast-Neutron Collar (FNCL) as a potential replacement system for the UNCL.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Fundamental Properties of Confined Enzymes

We recently developed an enzymatically active, ultra-thin, nano-stabilized liquid membrane for CO 2 separation from a mixture of gases, which was recognized by an international R&D 100 Award in 2015. The separation membrane is an approximately 18-nm thick water layer stabilized by capillary condensation within a hydrophilic mesoporous silica film and embedded with the metallo-enzyme carbonic anhydrase. The enzyme speeds CO 2 uptake and release from the membrane by catalyzing the rapid inter-conversion of carbon dioxide and water to bicarbonate and a proton. The membrane separates CO 2 from 1:1 gas mixtures at a rate of 2600 GPU with CO 2 /N 2 and CO 2 /H 2 selectivities exceeding 788 and 1500, the highest combined flux and selectivity yet reported. That membrane performance exceeds, for the first time, the U.S. Department of Energy standards for CO 2 capture technology. CO 2 flux depends sensitively on nanopore surface chemistry in the active region. To understand that dependence, we applied molecular simulations to interrogate enzyme behavior in the presence of varied surface chemistries. The results indicate that a polar surface chemistry within the membrane nanopores prevents aggregation of enzymes that would otherwise occur in both bulk liquid solution and non-polar nanopores. Additionally, the enzyme active site maintains a stable structure, even when the overall protein structure deforms within the nanopores. In summary, confinement in the ultra-thin layer of water within mesoporous silica nanopores facilitates a 15x higher enzyme concentration than in bulk conditions, without affecting the structure of the enzyme active site, when the nanopore surfaces are covered with polar functional groups. Thus, confinement of the carbonic enzymes in the membrane water-filled nanopores facilitates higher rates of CO 2 uptake and release than achievable in bulk solutions.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Experimental Evaluation of the Fast-Neutron Passive Collar (FNPC) Performance (Interim Report)

This report represents a deliverable in the Safeguards Technology WBS # Project Title, 24.1.3.1, Task 3 (Report on laboratory-based performance testing of the FNPC). A new, simplified method for the verification of the 235 U mass in fresh LEU fuel assemblies that is relatively independent of burnable poison content is being developed. LWR fresh fuel is currently verified using the uranium neutron coincidence collar (UNCL), which relies on an AmLi source to induce fission in the 235 U. AmLi neutrons are slowed down in polyethylene, so the induced fission is primarily due to thermal neutrons. Burnable poisons, which are added to nuclear fuel assemblies to extend the lifetime of the fuel, absorb neutrons that would otherwise have induced fission in the fuel, thereby reducing the neutron count rate and thus the measured 235 U mass. To remove this bias factor a correction is applied based on the operator’s declared burnable poison content. The new technique uses 238 U spontaneous fission in LWR fresh fuel rods to self-interrogate the 235 U mass. The 238 U spontaneous fission neutrons have a hard neutron energy spectrum, which means that the technique is less sensitive to burnable poisons than the AmLi based systems. This project has continued the work done over the past two years to study this new technique using the optimized 3 He based fastneutron passive collar (FNPC). Fabrication of the FNPC has been completed and measurements are in progress using the LANL mockup PWR fuel assembly. Also, preliminary evaluations of advanced analysis techniques and unattended mode operation have been performed. In FY18, the 3 He tube based detector was compared with a 10 B sealed cell based detector for the same set of PWR fuel assemblies in the Rodeo-II program. The results were that the optimized 3 He detector had higher efficiency and less weight than the 10 B based system where both systems had about the same cost. Thus, the FY19 work continued exclusively with the 3 He based detector; although, either system had the potential for future applications. However, the high efficiency of the FPNC (~24%) is critical for precise measurements of the triples rate necessary in the multiplicity advanced analysis technique which can solve for the burnable poison content.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Electrochemically-Driven Phase Transformations in Battery Compounds (Final Technical Report)

Ion-insertion compounds for advanced batteries frequently exhibit phase transformations as the concentration of the working ion varies. Under the large electrochemical driving forces inherent to practical use, systems are often driven far from equilibrium and exhibit phase transition behavior not seen in other materials. An improved understanding of phase transformation pathways in electrode materials upon cycling will lead to new materials design concepts and electrochemical duty cycle management strategies that improve capacity utilization at high charge/discharge rates, reduce voltage and capacity hysteresis, and extend battery life. The main goal of this project is to develop a predictive understanding of the phase transition behavior of battery compounds when electrochemically driven far from equilibrium through a combined experimental- theoretical approach. Research focuses on elucidating how the phase transition behaviors in a diverse group of selected model systems (olivines, lithium metal, etc.) are regulated by various factors including transformation strains, plasticity, metastable transformation pathways, electrode microstructure, surface reaction and ion diffusion kinetics, and what are the unique features of phase transitions in battery compounds. To this end, operando X-ray-based characterization techniques are applied to interrogate the structure and composition evolution of electrode materials and interfaces at nano- and meso-scales. Mesoscale modeling techniques such as phase-field simulation are employed to shed light on the experimental observations and establish a unified framework for describing phase transition behaviors in battery compounds.

25 ENERGY STORAGE↗
DOE OSTI2021

Advancing Pressure Gain Combustion for Terrestrial Turbine Systems

The principal objectives of this project were to demonstrate the operability of a natural gas - air RDE at gas turbine engine cycle conditions. To achieve these goals, our specific tasks were to 1) characterize the dynamic injection and mixing performance of candidate injectors, 2) assess the engine operability via interrogation of spatio-temporal dynamics of combustor inlet and exit flows, 3) measure the engine emissions, and 4) complete an overall assessment of the pressure gain potential of the device. In order to advance RDE technology to the greatest extent possible, the reactants and experimental conditions were chosen to replicate combustor and injector conditions in a terrestrial power generation system. This path was taken because the scaling of combustion devices is, in general, an immature area given the challenges of interrelated mixing and chemical kinetics processes both of which scale with operating conditions.

03 NATURAL GAS↗
DOE OSTI2020

Scale Invariance of the Homentropic Inviscid Euler Equations with Application to the Noh Problem

We investigate the inviscid compressible flow (Euler) equations constrained by an ”isentropic” equation of state (EOS), whose functional form in pressure is an arbitrary function of density alone. Under the aforementioned condition, we interrogate using symmetry methods the scale-invariance of the homentropic inviscid Euler equations. We find that under general conditions, we can reduce the inviscid Euler equations into a system of two coupled ordinary differential equations. To exemplify the utility of these results, we formulate two example scale-invariant, self-similar solutions. The first example includes a shock-free expanding bubble scenario, featuring a modified Tait EOS. The second example features the classical Noh problem, coupled to an arbitrary isentropic EOS. In this case, in order to satisfy the conditions set forth in the classical Noh problem, we find that the solution for the flow is given by a transcendental algebraic equation in the shocked density.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Experimental Evaluation of the Fast-Neutron Passive Collar (FNPC) Performance and Comparison with Scintillation Based Collars

This report describes a new method for the verification of fresh low enrichment uranium (LEU) fuel assemblies that can reduce International Atomic Energy Agency (IAEA) inspection time in the field and be completely independent of operator declared burnable poison content. The passive measurement makes unattended mode operation practical, and thus provides the potential for reducing inspector time in the field for future applications. The new simplified passive neutron measurement uses the 238 U spontaneous fission in LEU fresh fuel rods to self-interrogate the 235 U mass in the neighboring rods. The measured response increases linearly with the increase in the linear density (LD) of 235 U. The relatively high efficiency of the passive neutron detector (24%) provides good statistical precision (~ 2%) for the singles, doubles, and triples counting rates in the thermal-neutron mode. The three observables makes possible multiplicity analysis so that both the 235 U LD and the effective burnable poison content can be determined independent of the operator declarations. This closes the potential diversion path of miss-declaration the burnable poison content. This report presents the detector design, the as-built system, the detector parameter measurements, the calibration, and the assay uncertainty estimates. The calibration measurements were performed using the Los Alamos Laboratory mockup PWR fuel assembly. The measurements were made in both the fastneutron mode (with Cd/Gd metal liners) and the thermal-neutron mode (no Cd/Gd liners).

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗