Engineering topics

Papesch, Cynthia

Publications and source records attributed to Papesch, Cynthia.

9 records

DOE OSTI2017

Metallic Fuels Handbook, Part 1: Alloys Based on U-Zr, Pu-Zr, U-Pu, or U-Pu-Zr, Including Those with Minor Actinides (Np, Am, Cm), Rare-earth Elements (La, Ce, Pr, Nd, Gd), and Y; and Part 2: Elements and Alloys not Based on U-Zr, Pu-Zr, U-Pu, or U-Pu-Zr

The Metallic Fuels Handbook summarizes currently available information about phases and phase diagrams, heat capacity, thermal expansion, and thermal conductivity of elements and alloys in the U-Pu-Zr-Np-Am-La-Ce-Pr-Nd system. Although many sections are reviews and updates of material in previous versions of the Handbook, this revision is the first to include alloys with four or more elements. In addition to presenting information about materials properties, the handbook attempts to provide information about how well each property is known and how much variation exists between measurements. Although it includes some results from models, its primary focus is experimental data. Because of its size, the Handbook has been split into two parts, which are presented as separate documents. This (the first) part contains introductory material and information about the U-Pu-Zr system (U-Zr, Pu-Zr, U-Pu, and U-Pu-Zr alloys, including those with minor actinides, rare-earth elements, and Y). The second part contains information about elements and the remaining alloys in the U-Np-Pu-Am-La-Ce-Pr-Nd-Zr system.

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DOE OSTI2017

The characterization of microstructure and chemistry of transmutation fuels

The goal of the fast reactor development programs is fabrication and certification of a nuclear fuel system that performs all functions of a conventional fuel while destroying recycled actinides. Metal fuels, such as U-Pu-Zr fuels, are considered to be candidates for this application. The physical and mechanical properties, as well as behavior laws and correlations of metal alloy fuel, all of which define the behavior and performance of metal alloy fuels has been investigated in detail. The results indicated that the prospect for fueling a future fast spectrum reactor using metal fuels is excellent. There are several challenges associated with the fuel implementation in reactor environment. One of the limiting factors in lifetime and safety of thermal and fast reactor systems is fuel swelling and resulting fission product transport to cladding. Understanding diffusion kinetics and phases formed between metal fuel and cladding upon exposure to high temperatures typical in reactor environment is critical for ensuring integrity, safety, and performance of the material, advancement of this type of fuel in the future, and securing long-term success of the nuclear fleet. The first step to understanding fuel-cladding interaction is investigation of an as-cast fuel microstructure. Despite the importance of these fuels, detailed description of microstructures in these materials is extremely limited. The majority of published results are based on characterization of as-cast microstructures of these fuels in scanning electron microscopes (SEM). In this work, we present the results from microstructural characterization of metallic Pu-based fuels, which is essential in the validation of current and future atomistic and meso-scale modeling efforts. A firm understanding of microstructural evolution in reactor materials is imperative and will lead to deeper understanding of in-reactor degradation behavior, creating a new generation of radiation-resistant materials and fuels with the potential for significant increases in burn-up.

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DOE OSTI2017

Coupling Experiments and Simulations to Understand Metallic Fuel Behavior

The development of metal alloy fuels for minor actinide transmutation in fast reactor systems is of high importance. However, it faces numerous technical challenges such as: i) fuel behavior has to be benign during core off-normal events; ii) fuel has to maintain integrity to high burnup; iii) low minor actinide fabrication loss under remote handling conditions; and iv) fuel has to lend itself to low-loss recycling process. Limited experimental fuel performance data is currently available to support the selection of a fuel type for a transmutation system. Metallic fuels are being considered for application in fast reactor environment due to the high burn-up, high fissile and fertile density capability, inherent safety characteristics, favorable thermal response, and relatively easy recycling process. The uranium-plutonium-zirconium (U-Pu- Zr) based alloys are considered as one of the most promising metallic fuels for such application. In this work, we present results of microstructural characterization of Pu-Zr and U-Pu-Zr alloys and provide much needed linkage between thermal properties and microscopic scale observation. A firm understanding of microstructural evolution in reactor materials is imperative and will lead to deeper understanding of in-reactor degradation behavior, creating a new generation of radiation-resistant materials and fuels with the potential for significant increases in burn-up.

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DOE OSTI2017

A Phase-Field Model for the U-Pu-Zr System

Modeling nuclear materials is a multi-scale, multi-physics endeavor. Researchers are currently investigating how bulk material properties are affected by the evolution of microscopic material structures, i.e. microstructures. Development of tools that can mechanistically predict the effects of processes like diffusion and grain growth on properties like thermal conductivity will transform nuclear material design, manufacturing, and use. Intermediate-scale, i.e. mesoscale, modeling is among the most promising tools available for this task. Expedited development of mesoscale models, however, will require structured collaboration between modelers and experimentalists. Coupling these fields promises to improve both model accuracy and experiment design. With these ideas in mind, a mesoscale model of the U-Pu-Zr system is being developed. Its development will accompany a series of experiments involving irradiation of metallic fuel samples.

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DOE OSTI2017

Phase Verification and Thermophysical Properties Evaluation of Pu-Zr alloys

Pu-Zr alloys have been investigated for almost 60 years, with much of the experimental data collected during the 1950's and 1960's'. Key features of the Pu-Zr phase diagram include continuous solubility between the body-centered cubic phases {beta}-Zr and {epsilon}-Pu, extensive solubility of Zr in {delta}-Pu and limited solubility in {alpha}-Pu, {beta}-Pu, {gamma}-Pu, and {delta}'-Pu, and the existence of {theta}-(Pu-Zr) as an intermediate phase that is stable at room-temperature. The available experimental data were synthesized by Okamoto to produce a single phase diagram. However, many details of the phase diagram remain poorly known, particularly those involving temperatures below {approx}400 deg. C or concentrations of Zr below {approx}30 at% or above {approx}65 at%. Thermal property measurements and microstructural characterization on Pu-Zr alloys are complicated by sluggish kinetics, high sensitivity to low concentrations of oxygen and other impurities leading to the possible formation of oxygen-stabilized low-temperature phases, and the metallurgical complexity and unique characteristics of Pu. As a result of these difficulties, the identities of some possible Pu-Zr phases are controversial, and there is little published data on phase transformations or thermophysical properties.

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DOE OSTI2016

Fundamental Properties for Evaluation of Uranium-free TRU-Zr Metal Fuel Performance

FR (Fast Reactor) is widely recognized to effectively burn plutonium and MA (Minor Actinides) (i.e., TRU: Transuranic) due to its higher fission-to-neutron-capture ratio compared to LWR. When TRU in LWR (Light Water Reactor) spent fuel is recycled into FR cycle, the radiotoxicity of the residual nuclear wastes from LWR spent fuel is reduced to natural uranium level after several hundred years instead of more than hundreds of thousand years for no recycling case. It could significantly improve public perception to nuclear waste disposal and might reduce the burden of the disposal. However, U-TRU-fueled fast reactors also produce TRU while burning TRU because they use uranium together with TRU. For example, FR, even with low conversion ratio of 0.75, burns only 0.18 t TRU/GWe/y, while LWRs produces about 0.22 t TRU/GWe/y. It is not a realistic scenario which needs almost the same capacity of fast reactors as that of LWRs to continuously burn TRU at LWR-dominant era in the near term at least. Therefore, a FR system to burn TRU from LWR with the minimum reactor units is desirable. The most effective way is to use uranium-free TRU fuel since it does not produce any new TRU. It can reduce the capacity of the TRU burner units and the associated fuel cycle facilities to about 1/5 and 1/8 respectively. Metal fuel FR cycle is considered to be one of the most promising ways because uranium-free TRU metal fuel could be recycled by pyro-process for U-Pu-Zr metal fuel without large modifications. This paper shows the recent research progress on fundamental properties of uranium-free TRU metal fuel. (authors)

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DOE OSTI2016

The Role of Electron and Atom Probe Tomography in Characterization of Nuclear Fuels

Dramatic advances in materials characterization capabilities over the last few years enabled microstructural and chemical 3D characterization of specimens at the atomic-scale with unprecedented quantitative precision and high data collection rates. These improvements allow for the transition of electron tomography (ET) and atom probe tomography (APT) techniques to a much broader research field and their implementation in the characterization of nuclear fuels and highly radioactive materials. Nanoscale characterization has been widely developed for non-nuclear applications, yet in the nuclear arena, particularly for fuels, these modern characterization techniques have not been applied in concert to elucidate fundamental material behavior in metal fuel. In this work, we present cross-correlated APT and ET data and provide atomic-scale representations of microstructure and chemistry of nuclear fuels, which is essential in the validation of current and future atomistic and meso-scale modeling efforts. A firm understanding of microstructural evolution in reactor materials is imperative and will lead to deeper understanding of in-reactor degradation behavior, creating a new generation of radiation-resistant materials and fuels with the potential for significant increases in burn-up. In summary, two complementary techniques were used to characterize phases formed as a result of interdiffusion between U-Pu-Zr metal fuel and cladding and fission gas bubbles produced in U-Mo fuel upon irradiation. Understanding in-reactor degradation behavior of these materials is critical to advancing nuclear energy technology. (authors)

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DOE OSTI2015

Thermal Properties Measurement Report

The Thermal Properties Measurement Report summarizes the research, development, installation, and initial use of significant experimental thermal property characterization capabilities at the INL in FY 2015. These new capabilities were used to characterize a U 3 Si 2 (candidate Accident Tolerant) fuel sample fabricated at the INL. The ability to perform measurements at various length scales is important and provides additional data that is not currently in the literature. However, the real value of the data will be in accomplishing a phenomenological understanding of the thermal conductivity in fuels and the ties to predictive modeling. Thus, the MARMOT advanced modeling and simulation capability was utilized to illustrate how the microstructural data can be modeled and compared with bulk characterization data. A scientific method was established for thermal property measurement capability on irradiated nuclear fuel samples, which will be installed in the Irradiated Material Characterization Laboratory (IMCL).

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DOE OSTI2015

Thermal Properties Capability Development Workshop Summary to Support the Implementation Plan for PIE Thermal Conductivity Measurements

The Department of Energy (DOE)-Office of Nuclear Energy (NE), Idaho National Laboratory (INL), and associated nuclear fuels programs have invested heavily over the years in infrastructure and capability development. With the current domestic and international need to develop Accident Tolerant Fuels (ATF), increasing importance is being placed on understanding fuel performance in irradiated conditions and on the need to model and validate that performance to reduce uncertainty and licensing timeframes. INL’s Thermal Properties Capability Development Workshop was organized to identify the capability needed by the various nuclear programs and list the opportunities to meet those needs. In addition, by the end of fiscal year 2015, the decision will be made on the initial thermal properties instruments to populate the shielded cell in the Irradiated Materials Characterization Laboratory (IMCL).

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