Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Fuels”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Advanced Fuel Cycle Cost Basis – 2017 Edition

This report, commissioned by the U.S. Department of Energy (DOE) Office of Nuclear Energy (NE), provides a comprehensive set of cost data supporting a cost analysis for the relative economic comparison of options for use in the DOE Nuclear Technology Research and Development (NTRD) Program (previously the Fuel Cycle Research and Development (FCRD) and the Advanced Fuel Cycle Initiative (AFCI)). The report describes the NTRD cost basis development process, reference information on NTRD cost modules, a procedure for estimating fuel cycle costs, economic evaluation guidelines, and a discussion on the integration of cost data into economic computer models. This report contains reference cost data for numerous fuel cycle cost modules (modules A-O) as well as cost modules for a number of reactor types (R modules). The fuel cycle cost modules were developed in the areas of natural uranium mining and milling, thorium mining and milling, conversion, enrichment, depleted uranium disposition, fuel fabrication, interim spent fuel storage, reprocessing, waste conditioning, spent nuclear fuel (SNF) packaging, long-term monitored retrievable storage, managed decay storage, recycled product storage, near surface disposal of low-level waste (LLW), geologic repository and other disposal concepts, and transportation processes for nuclear fuel, LLW, SNF, transuranic, and high-level waste. Since its inception, this report has been periodically updated. The last such internal document was published in August 2015 while the last external edition was published in December of 2009 as INL/EXT-07-12107 and is available on the Web at URL: www.inl.gov/technicalpublications/Documents/4536700.pdf. This current report (Sept 2017) is planned to be reviewed for external release, at which time it will replace the 2009 report as an external publication. This information is used in the ongoing evaluation of nuclear fuel cycles by the NE NTRD program.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Preliminary modeling of accident tolerant fuel concepts under accident conditions

In this paper, we present simulations of two proposed accident tolerant fuel systems for light-water reactors: U{sub 3}Si{sub 2} fuel with Zircaloy-4 cladding, and UO{sub 2} fuel with FeCrAl cladding. The simulations investigate the fuel performance response of the proposed ATF systems under Loss of Coolant (LOCA) and Station Blackout (SBO) conditions using the BISON code. It was observed that U{sub 3}Si{sub 2}/Zircaloy4 and UO{sub 2}/FeCrAl have superior performance during a 90 s LOCA than traditional UO{sub 2}/Zircaloy4 fuel rods. This is based upon reduced fuel centerline temperatures and lower cladding strains experienced during the LOCA. For the postulated SBO analyzed in this work, it was found that the centerline temperature and cladding strains remained well below any values of concern. This is attributed to the shortness of the rod studied and how the coolant channel model treats the inlet as the bottom of the rod. An analysis of a full-length fuel rod is required to obtain improved qualitative comparisons between the 3 systems under SBO conditions. Sensitivity analyses have been performed using Sandia National Laboratories' DAKOTA software to determine which input parameters (e.g., fuel specific heat) have the greatest influence on the output metrics of interest (e.g., fuel centerline temperature). Early results indicate that each concept has significant advantages as well as areas of concern. Further work is required prior to formulating the proposition report for the Advanced Fuels Campaign.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

EDF's used fuel management french policy - 15199

Regarding back-end fuel cycle, EDF's strategy, implemented from the very beginning of French nuclear production, consists in reprocessing of used fuel; decision to recycle plutonium in French PWR was taken from 1984. This reprocessing and recycling strategy, relying on existing industrial facilities (AREVA La Hague and Melox plants), has proven to be reliable and efficient. Treatment leads to a stabilization of used fuel total inventory in interim storage. Vitrification process ensures a safe packaging for high level and long-lived waste under a reduced volume. Recycling of fissile materials saves natural uranium requirements. Concentration of Pu in MOX used fuel leaves open the option to reuse it for starting next Generation IV systems beyond 2040. In 2008, EDF and AREVA, supported by French Government, agreed on commercial terms covering long term fuel reprocessing and recycling (up to 2040). Currently, EDF fuel management strategy relies on flow equilibrium in order to respect fuel cycle consistency and sustainability. The underlying principle is to strictly adjust separated plutonium production to recycling possibilities (i.e. licensed reactors and MOX fuel fabrication facilities). Given that fuel cycle policy, any trend in NPP core management that may impact the fuel cycle should be anticipated within times in order to avoid technical or administrative incompatibilities, and guarantee a high level of safety and robustness. In collaboration with industrial operators, EDF have to perform periodic 'Cycle Impact' analyses and report to the French Nuclear Safety Authority (ASN); next exercise is scheduled by the end of 2016. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Neutronics analysis of fuel-in-fiber concept

One of the consequences of Fukushima was the increase in interest in development of safer, more accident tolerant fuels and claddings. Accident tolerant fuels (ATF) are defined by the Nuclear Regulatory Committee (NRC) as fuels that, in comparison with the standard UO{sub 2}- Zircaloy system, can tolerate loss of active cooling in the core for a considerably longer time period while maintaining or improving the fuel performance during normal operations. One of the ideas being considered is tri-isotropic (TRISO) fuel particles. TRISO fuel pebbles consist of several layers - the outermost being graphite. TRISO pebbles are considered to be accident tolerant, because of their ability to retain fission products at high temperatures. One of the ideas implementing TRISO pebbles is Fully Ceramic Microencapsulated fuel where the pellet is comprised of TRISO pebbles in a matrix. TRISO particles though have a low maximum packing fraction when put in the spherical or cylindrical configuration with the current fabrication techniques (hot and cold press). This leads to considerable increase in enrichment to maintain cycle length for today's Light Water Reactors (LWR). The Fuel-in-Fiber concept, developed by FreeForm-Fiber (FFF), has the advantages of TRISO particles while utilizing a novel additive direct manufacturing technique for rapid fabrication. Fuel-in-Fiber are small fibers made of layers just like TRISO particles but because of their cylindrical nature, they can be packed with a tighter packing fraction than the TRISO particles. The fibers are woven within a SiC matrix and used to replace a typical pellet in a fuel pin. This means that they can easily be placed into LWR's without having to change the assembly or core structures. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Towards a Neutronic and Thermal-Hydraulic Safety Analysis of PWR Fuel Bow with SIMULATE5 and COBRA-TF

In the 1990's, collective fuel assembly bow was observed in the Ringhals PWRs in Sweden. Back then fuel vendors reinforced the fuel assemblies' dashpot, decreased hold-down spring forces, increased guide tube wall thickness, and introduced guide tube materials with higher creep resistance in order to improve dimensional stability. Nevertheless, twenty years later in 2010, the same kind of collective bow with S and C shape patterns started to appear in most of Germany's PWRs. At this time the SIMULATE5 (S5) core simulator with its delta-gap bow model (DGA) which was originally developed for safety analysis at Ringhals, could be used as an off-the-shelf solution to assess the impact of bow on Fq and FH. However, these two quantities are of secondary importance in German PWRs in normal operation because the most restricting licensing criteria set limits on DNBRmin values. For this purpose, a method was developed to extract S5 pin powers from DGA calculations and automatically generate COBRA-TF input files (CTF) to analyze DNBR values in the cores. In the following two sections, it is shown how the S5 model for DGA calculations has been verified with independent MCNP6 calculations in order to check its predictions on pin power changes for delta gaps up to 1 cm in size and how the existing licensed DNBR calculation methodology has been updated to bowed fuel assembly situations with the help of CTF. Finally, the applicability of the Doroschuk CHF correlation, which is the licensing standard in most German PWRs, is discussed. For the fuel bow patterns considered, it is assumed that only the gap between fuel assemblies change and that the pitch between fuel rods inside the assemblies remains largely unchanged. This approximation can be justified by the visual inspections conducted at the plants during the outages. Every calculation of the pin-power impact of delta-gaps in the core under operating conditions is only as good as the knowledge of the bow pattern. Measurements of fuel assembly bow at cold conditions have been made for some German PWRs for all the fuel assemblies in the core during plant outages. Together with methods developed by the fuel assembly vendors, a best-estimate bow pattern during operation could be reconstructed. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Study on Neutronics Calculation Method of SCWR with Annular Fuel Assembly

Supercritical Water-Cooled Reactor (SCWR) is one of Gen-IV reactor systems for its advantages over LWRs, such as high thermal efficiency, simplified reactor system and economics. Annular fuel was proposed by MIT to supplant conventional solid fuel and improve power density in LWRs. Annular fuel is cooled from both inside and outside of the fuel. Thus a lower fuel temperature and cladding surface temperature can be achieved with higher power density. SCWRs will benefit from this advantage because high cladding temperature (usually over 650 degree C) is one challenge of SCWRs. Using annular fuel in SCWRs is very promising. This is also because the inner hole of the annual fuel can provide extra neutron moderation. Supercritical water density is too low to provide enough moderation. Different analysis codes have been developed all over the world to carry out SCWR pre-conceptual core design. Yamaji et al. developed SRAC/ASMBURN/COREBN to study Japan version of SCWR. Monti et al. used ERANOS to analyze HPLWR (High Performance Light Water Reactor). WIMS-D4/CITATION was also used to calculate HPLWR by Tashakor et al.. These codes employ a two-step method used in PWRs calculation. Lattice/Assembly calculation is carried out as the first step. In the second step, few group constant of different fuel assembly types is then used in core calculation. MCNP had also been used to study SCWR by Watta et al.. Due to large computation time cost, it's used mostly to analyze fuel assembly or core performance rather than pre-conceptual design, in which much optimization is needed. In this research, a neutronics calculation code for SCWR is developed using two-step method. This code is verified by comparing with Monte-Carlo code. Fuel assembly homogenization method is studied to improve the code accuracy.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Distinguishing Research Reactor Fuels Using Neutron Multiplicity - 25615

Neutron measurements are one of the reliable means of interrogation of fissile material. Neutron measurements are used for total counting (pure metal fissile samples) or counting coincidence/multiplicity (for impure fissile samples). Various flavors of neutron measurement are used routinely by the IAEA to determine the fissile mass of an unknown sample. The objective of this work is to design an experiment to distinguish the two different fuel types using neutron multiplicity method. The design of experiment is performed using Monte Carlo N- Particle (MCNP) transport code. General Electric (GE) designed 1-MWt pool-type research reactor at UMass Lowell (UMLRR) uses Materials Testing Reactor (MTR) plate-type fuel consisting of 19 full and 2 partial fuel assemblies, controlled by four boron control blades and one regulating control rod. Two different fuel types are available at the UMLRR facility. In 2008, UMass Lowell obtained slightly burnt fuel assemblies from the decommissioned WPI research reactor. The simulation results discussed in this paper show that within the limits of statistical error, the single and double moments for the WPI and UMLRR fuels can be measured. The two fuels have very similar composition and enrichments resulting in very similar neutron multiplicity moments. This implies that neutron multiplicity measurements alone would not be sufficient to distinguish between the two fuel types at low burnups. The change in the observed single-double ratio between each fuel type is less than 6 % which falls below the uncertainty in the efficiency of the JCC71 slab detectors. The neutron signature from low burnup and low enriched uranium fuel are not strong, however, these can be measured under low background and long measurement times. This would be an important consideration in designing the experiments and parallel gamma measurements will also be planned. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

End-of-injection fuel dribble of multi-hole diesel injector: Comprehensive investigation of phenomenon and discussion on control strategy

The needle shutdown of fuel injectors leads to an undesired fuel dribble that forms unburned hydrocarbons and decreases the engine thermal efficiency in modern engines. Understanding of the fuel dribbling process is of great importance to establish its minimization strategy for optimal use of conventional fuels. However, the detailed needle dynamics and in- and near-nozzle flow characteristics governing the fuel dribble process have not been thoroughly understood. In this study, the needle dynamics, in- and near-nozzle flow characteristics and fuel dribble of a mini-sac type three-hole diesel injector were investigated using a highspeed X-ray phase-contrast imaging technique at different injection pressures. The results showed that an increase in injection pressure increased the flow evacuation velocity at the needle close that induced a more intense fuel cavitation and air ingestion inside the nozzle. The fuel dribbling process showed a high shot-toshot deviation. A statistical analysis of 50-shot results exhibited two breakup modes of fuel dribble determined by the flow evacuation velocity at the needle close and presence of air ingestion. In the first mode, the fast breakup with a short residence time of fuel dribble occurred. Meanwhile, the dripping of undisturbed liquid column with a long residence time of fuel dribble occurred in the second mode. An increase in injection pressure increased the population of the first mode due to more intense air ingestion that primarily caused by an increase in needle closing speed other than an increase in peak injection velocity. Based on the results, the formation mechanism and control strategies of the fuel dribble from modern diesel injectors were discussed.

Moon, Seoksu↗
DOE OSTI2016

Bio-derived Fuel Blend Dilution of Marine Engine Oil and Imapct on Friction and Wear Behavior

To reduce the amount of petroleum-derived fuel used in vehicles and vessels powered by internal combustion engines, the addition of bio-derived fuel extenders is a common practice. Ethanol is perhaps the most common bio-derived fuel used for blending, and butanol is being evaluated as a promising alternative. The present study determined the fuel dilution rate of three lubricating oils (E0, E10, and i-B16) in a marine engine operating in on-water conditions with a start-and-stop cycle protocol. The level of fuel dilution increased with the number of cycles for all three fuels. The most dilution was observed with i-B16 fuel, and the least with E10 fuel. In all cases, fuel dilution substantially reduced the oil viscosity. The impacts of fuel dilution and the consequent viscosity reduction on the lubricating capability of the engine oil in terms of friction, wear, and scuffing prevention were evaluated by four different tests protocols. Although the fuel dilution of the engine oil had minimal effect on friction, because the test conditions were under the boundary lubrication regime, significant effects were observed on wear in many cases. Fuel dilution also was observed to reduce the load-carrying capacity of the engine oils in terms of scuffing load reduction.

Ajayi, Oyelayo O.↗
DOE OSTI2014

GENCO Infrastructure Solutions, Inc. Fuel Cell-Powered Lift Truck Fleet Deployment Projects (Final Technical Report)

The overall objectives of this project were to evaluate the performance, operability and safety of fork lift trucks powered by fuel cells in large distribution centers. This was accomplished by replacing the batteries in over 350 lift trucks with fuel cells at five distribution centers operated by GENCO. The annual cost savings of lift trucks powered by fuel cell power units was between $\$$2,400 and $\$$5,300 per truck compared to battery powered lift trucks, excluding DOE contributions. The greatest savings were in fueling labor costs where a fuel cell powered lift truck could be fueled in a few minutes per day compared to over an hour for battery powered lift trucks which required removal and replacement of batteries. Lift truck operators where generally very satisfied with the performance of the fuel cell power units, primarily because there was no reduction in power over the duration of a shift as experienced with battery powered lift trucks. The operators also appreciated the fast and easy fueling compared to the effort and potential risk of injury associated with switching heavy batteries in and out of lift trucks. There were no safety issues with the fueling or operation of the fuel cells. Although maintenance costs for the fuel cells were higher than for batteries, these costs are expected to decrease significantly in the next generation of fuel cells, making them even more cost effective.

08 HYDROGEN↗
DOE OSTI2017

Analysis of hydrogen as a Transportation Fuel FY17 Report

This report summarizes the results of literature reviews, surveys and analyses performed to evaluate the potential of hydrogen-fueled vehicles to be an economically viable transportation alternative. Five existing and important drivers of expanding hydrogen-fueled transportation adoption are multi-billion dollar sales reservations of Nikola Class 8 trucks, CALSTART viability analysis of hybrid-hydrogen drayage trucks in the shipyard cargo application, analysis showing economic advantages of Fuel Cell Electric Vehicles (FCEV)s over Battery Electric Vehicles (BEV)s beginning at 150-mile ranges, the announcement of a commercial 5kg electrolyzer, and commercial plans or vehicle availability by nine vehicle manufacturers of FCEV passenger vehicles. But hydrogen infrastructure availability needed to support broad adoption of hydrogen-fueled vehicles is limited to less than 50 publicly-available refueling stations, primarily in California. The demand side (consumer) economics associated with FCEV adoption showed strong economic sensitivity to the original vehicle’s fuel economy (mpg), distance traveled, and hydrogen (H2) generation costs. Seven use cases were used to evaluate the broad range of potential FCEV purchasers, including autonomous vehicle applications. Each consumer use case analysis resulted in a different hydrogen fuel cost that would be equivalent to the current fuel cost being paid by the consumer. The H2 generation costs (supply side) were sensitive to the volume of H2 supplied and H2 production costs needed to repay H2 supply facility capital costs and produce competitively-priced energy. H2FAST was used to more accurately incorporate capital, maintenance and production costs into a viable H2 supply cost to the consumer. When the H2 generation and consumer economics were combined, several applications with positive economics became clear. The availability of low-cost hydrogen pipeline connections, and therefore low-cost hydrogen, greatly benefits the California drayage truck application with hybrid-hydrogen retrofits being repaid within seven years. Class 8 trucks could also take advantage of these low-cost, but regional hydrogen supplies. In addition, the IVYS electrolyzer-based hydrogen generation product showed the potential to deliver hydrogen economically in an urban or freeway off-ramp setting to a limited number of passenger vehicles in areas with low-cost electricity. These positive, manually developed results show the need to develop more advanced tools to provide an expanded evaluation of the economics of hydrogen-based fuel applications. The use cases evaluated showed significant potential for hydrogen-fueled vehicles to have a sustainable impact as a transportation fuel. The positive impact is not limited to transportation fuels, but also grid resilience and flexibility through the use of controllable and variable electrolyzer output to rapidly adjust to changing grid conditions and enable greater integration of solar and wind generated power. This capability would directly enable alternative fuel vehicles to impact energy consumption, GHG emissions, and the economy at the regional and national levels.

08 HYDROGEN↗
DOE OSTI2020

Joint Development of SAS4A Code in Application to Oxide-fueled LFR Severe Accident Analysis

The scope of this project was to pursue specific SAS4A liquid-metal cooled reactor (LMR) safety analysis software extensions to simulate postulated accidents with fuel failures for oxide-fueled Lead-cooled Fast Reactors (LFRs). Since most U.S. LMR experience is on sodium-cooled fast reactor options based on past testing and operation experience with EBR-II and FFTF, the DOE’s legacy fast reactor safety analysis capabilities were focused on metal-fueled pool-type concepts with sodium coolant. In recent years, Westinghouse Electric Company (WEC) has decided to pursue an LFR design as one of their next generation nuclear technology options because of its favorable safety and economics attributes. Oxide fuel is considered among other fuel options due to previous WEC experience with this fuel form. Development of this new technology requires the availability of adequately accurate computational tools, some of which can be adapted from versions of similar software used for analysis of other LMRs. Although Argonne National Laboratory’s (ANL) SAS4A/SASSYS-1 safety analysis software suite (shortened as SAS4A code hereafter for brevity) has the basic capabilities to model LFR system designs, the SAS4A code modules used in the analysis of accidents with fuel/cladding failures lack appropriate models for the unique phenomena that govern as-irradiated oxide-fuel damage mechanisms in lead coolant. Therefore, the objective of this project was to extend the capabilities of SAS4A with mechanistic oxide-fuel failure models in lead coolant for margin to failure assessments, analysis of failure modes, location and timing of failures under different accident scenarios consistent with the whole-plant dynamic response including the reactivity feedback, and assessment of the potential for fuel damage propagation due to potential fission gas jet and fuel-fragment/molten fuel impingement to neighboring fuel pins in an assembly. This report provides mainly a summary of Argonne’s technical contributions in the joint project, but the reports and publications by the Participant team are included as references at the end of the report.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2019

Vehicle Technologies and Fuel Cell Technologies Office Research and Development Programs: Prospective Benefits Assessment for Medium- and Heavy-duty Vehicles

Through a diverse set of programs, the Vehicle Technologies and Fuel Cell Technologies Offices of the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) invest in early-stage vehicle and fuel cell research. The Vehicle Technologies Office (VTO) and the Fuel Cell Technologies Office (FCTO) are two offices that are encompassed within EERE’s Sustainable Transportation pillar. VTO conducts research and development (R&D) to provide low-cost, reliable, and efficient energy for the transportation of goods and people across America. FCTO has a comprehensive portfolio of activities that address the barriers facing the development and implementation of hydrogen and fuel cells, with the ultimate goals of decreasing our dependence on oil, reducing greenhouse gas (GHG) emissions, and enabling clean, reliable power generation through both transportation and stationary uses of hydrogen. This report quantifies the vehicle-level and national-level benefits of successful VTO and FCTO R&D applied to medium- and heavy-duty vehicles. The benefits estimated include reductions in energy use and GHG emissions from and changes in expenditures on medium- and heavy-duty vehicles on the road in the United States through the year 2050. The potential future benefits of successfully developing and implementing these technologies were analyzed by comparing a “Program Success” case to a base case (the “No Program” case). The Program Success case represents the future with successful implementation of VTO and FCTO technologies. The No Program case represents a future in which VTO or FCTO do not contribute to these technologies after Fiscal Year (FY) 2019. Three side cases were analyzed to assess the sensitivity of the projections of market adoption to future electricity prices (including infrastructure costs), the availability of electricity and hydrogen at public stations, and fuel cell system efficiency. Advanced vehicle technologies supported by VTO and FCTO programs can greatly increase the fuel economy of medium- and heavy-duty vehicles. As a result of EERE-supported technologies, the sales-weighted average fuel economy of the fleet of all new Class 7 and 8 trucks in the Program Success case is projected to be 1.2 times that of the trucks in the No Program case in 2035 and 1.3 times the baseline in 2050. These technologies in Classes 4–6 increase fuel economy by a factor of 1.46 in 2035 and 1.78 in 2050. The fuel economy of the entire on-road medium- and heavy-duty vehicle fleet, including all fuel types, is projected to be higher by 10%, reaching 9.1 mpgde in 2035, and by 25%, reaching 11.0 mpgde in 2050. The resulting petroleum savings in 2050 were estimated to be 0.75 million barrels per day, and reductions in GHG emissions in 2050 were estimated to 110 million metric tons of carbon dioxide equivalent (CO 2 -eq) per year. Such petroleum reductions result in significant reductions in fuel expenditure for medium- and heavy-duty vehicles, totaling approximately $37 billion annually by 2035. Figure ES-1 shows the difference in projected consumption of diesel fuel, electricity, and hydrogen in the No Program and Program Success cases. Negative values show the reduction in the Program Success case, relative to the No Program case.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2020

Preliminary Evaluation of Driver Fuel Plates and Reduced Sodium Temperature to Increase Fast Test Reactor Experimental Neutron Irradiation Capabilities

All sodium-cooled fast test reactors operated so far have used essentially the same fuel geometrical ar-rangement, namely cylindrical fuel pins assembled into a triangular array in hexagonal fuel assemblies. Fuel compositions and dimensions may vary but the overall geometrical pattern remains identical. Fur-thermore, most sodium-cooled reactors have operated, and still operate, with core-average inlet and outlet sodium temperatures of, respectively, 350-400°C and 500-550°C. The present preliminary study revisits the standard fuel assembly geometry as well as operating tempera-tures to evaluate potential impact on fast test reactor neutron irradiation capabilities. The reference fuel is U-20Pu-10Zr. Pin (reference) and plate geometries are considered together with two sets of core-average sodium inlet/outlet temperatures: 350/500°C (reference) and 200/400°C. More prototypic environments could be obtained inside ad-hoc irradiation testing vehicles that are independent from the reactor primary coolant. Everything else being the same, fuel temperature is significantly lower in plates than in pins. Therefore, plates could in principle accommodate higher plutonium content, thus, reducing the need for uranium enrichment or allowing the use of lower quality plutonium (U-xPu-10Zr thermal conductivity and solidus temperature decrease as x increases, hence, necessitating additional thermal margins). For the reference pin configuration, lowering the inlet/outlet sodium temperatures from the reference 350/500°C down to 200/400°C provides additional thermal margins that can be used to increase the peak fast flux from about 4.5 × 10 15 n/cm 2 -s to 6 ×10 15 n/cm 2 -s for the same core power of 300 MW. Assuming 300 Equivalent Fuel Power Days (EFPD) of operation per calendar year, a (steel) test article could accu-mulate up to 75 dpa/year. The use of fuel plates provides even more thermal margins which may allow the peak fast flux to reach values as high as 8 × 10 15 n/cm 2 -s for both sets of inlet/outlet temperatures. In this environment, a test article could accumulate up to 95 dpa/year assuming 300 EFPD/year, hence greatly accelerating irradiation testing. Allowing a fast test reactor to operate over a wide range of inlet/outlet temperatures could add significant flexibility to its neutron irradiation capabilities. Steel present in the driver fuel assemblies is not expected to accumulate more than 90 displacements per atom (dpa) over its lifetime. Hence, steel alloys that are not suited for very high dpa but can operate over a wide range of temperatures (from low to high) would be appropriate for this application. Finally, because pin and plate assemblies fit on the same grid plate, a fast test reactor could in principle start-up with standard fuel pin assemblies and, later on, move to a plate-type Mark-II fuel to further in-crease its neutron irradiation capabilities while potentially reducing the level of uranium enrichment needed.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2021

Spill Behavior, Detection, and Mitigation for Emerging Nontraditional Marine Fuels

In this report, we describe the predicted impact of large spills or releases of alternative marine fuels. The fuels covered in this report are those that have been identified as potential future fuels for the marine shipping sector by industry experts and government agencies overseeing the development of renewable and low-carbon fuels. Several of these fuels are already in use, such as liquified natural gas, renewable diesel, ethanol, methanol, and biodiesel. Other fuels are hydrogen, dimethyl ether, ammonia, and bio-intermediates, such as catalytic fast pyrolysis biooils and hydrothermal liquefaction bio-crudes. The property databases of these fuels are extensive enough to form predictive assessments. Other potential marine fuels, such as lignin ethanol, have not been extensively evaluated and are therefore not included is this study. For each fuel chemistry, we have surmised the spill profiles and environmental impacts based on existing studies and relevant properties. The technologies used to detect spills (especially those for crude oil detection) are also reviewed for their applicability with alternative fuels, and in some instances, recommendations to improve these technologies for use with a particular fuel chemistry are put forward. Finally, current containment and remediation technologies are reviewed and assessed for their efficacy at handling these alternative fuels.

04 OIL SHALES AND TAR SANDS↗
DOE OSTI2021

Post-irradiation examination of legacy high burnup fuel to support safety testing

Safety/transient testing to evaluate performance under off-normal conditions is an essential pillar for both the development of Accident Tolerant Fuels (ATF) and the optimization of fuel operation economics beyond current discharge burnups. Among other factors, the successful interpretation of the transient testing results relies upon the knowledge of the initial conditions of the test, including the characteristics of the fuel system under scrutiny. When testing pre-irradiated material, the assumptions that the fuel and the cladding still have the same properties as in the pre-irradiation stage is obviously wrong and could affect the results of the test. This is particularly true the more burnup accumulates in the fuel rod and irradiation progresses. The knowledge of the initial microstructure of both fuel and cladding allows a clearer interpretation of the subsequent transient testing results, provides validation of the physical phenomena underlying the model predictions and eliminates the uncertainties related to the limited knowledge of the sample status before the test. One example is the phenomenon of fine fragmentation that occurs in Light Water reactor (LWR) fuel. During a Loss of Coolant Accident (LOCA) or Reactivity Initiated Transient (RIA) the fuel can severely fragment. During LOCA, high burnup fuel tend to finely fragment, which has raised safety concerns due to the increased likelihood of dispersal of such small particles once the cladding has burst and due to the increased fission gas release. Therefore, efforts have been devoted to the assessment of a pulverization threshold that could determine the conditions under which fine fragmentation is predominant. However, the lack of information regarding the initial conditions of the fuel, and the connections between those conditions and the pre-transient irradiation history, have hindered the development of a fully mechanistic fragmentation and pulverization criterion. The empirical relationships rely on conservative estimations, due to the lack of information on critical material properties and characteristics. More generally, experimental evidence of the irradiation-induced modifications at microstructural scale are necessary to determine the behavior of the material at the macroscopic scale, with the latter being the one of technological interest. Significant progress has been made in the last two decades in the developments of analytical materials science techniques that can be applied to highly radioactive materials, such as high burnup fuels. The availability of new techniques and the improvement of existing ones has enabled investigations previously not possible that can deepen the understanding of the fuel characteristics and properties at high burnup. The better knowledge of material behavior and irradiation-induced phenomena could help the prediction of its performance. In this context, the scope of the present work is to apply a wide portfolio of advanced characterization techniques to determine properties that are relevant for safety and performance. The results are interpreted in the context of engineering scale post-irradiation examinations and available information on the irradiation conditions.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1982

Experiments on fuel heating for commercial aircraft

An experimental jet fuel with a -33 C freezing point was chilled in a wing tank simulator with superimposed fuel heating to improve low temperature flowability. Heating consisted of circulating a portion of the fuel to an external heat exchanger and returning the heated fuel to the tank. Flowability was determined by the mass percent of unpumpable fuel (holdup) left in the simulator upon withdrawal of fuel at the conclusion of testing. The study demonstrated that fuel heating is feasible and improves flowability as compared to that of baseline, unheated tests. Delayed heating with initiation when the fuel reaches a prescribed low temperature limit, showed promise of being more efficient than continuous heating. Regardless of the mode or rate of heating, complete flowability (zero holdup) could not be restored by fuel heating. The severe, extreme-day environment imposed by the test caused a very small amount of subfreezing fuel to be retained near the tank surfaces even at high rates of heating. Correlations of flowability established for unheated fuel tests also could be applied to the heated test results if based on boundary-layer temperature or a solid index (subfreezing point) characteristic of the fuel.

Friedman, R.↗
NASA NTRS1982

Hybrid fuel cell/diesel generation total energy system, part 2

Meeting the Goldstone Deep Space Communications Complex (DGSCC) electrical and thermal requirements with the existing system was compared with using fuel cells. Fuel cell technology selection was based on a 1985 time frame for installation. The most cost-effective fuel feedstock for fuel cell application was identified. Fuels considered included diesel oil, natural gas, methanol and coal. These fuel feedstocks were considered not only on the cost and efficiency of the fuel conversion process, but also on complexity and integration of the fuel processor on system operation and thermal energy availability. After a review of fuel processor technology, catalytic steam reformer technology was selected based on the ease of integration and the economics of hydrogen production. The phosphoric acid fuel cell was selected for application at the GDSCC due to its commercial readiness for near term application. Fuel cell systems were analyzed for both natural gas and methanol feedstock. The subsequent economic analysis indicated that a natural gas fueled system was the most cost effective of the cases analyzed.

Blazek, C. F.↗