Using supercritical CO₂ (sCO₂) as a working fluid has increasingly gained attention in the energy industry. sCO₂ power cycles has various advantages, such as high cycle efficiency, compact turbomachinery, and potential zero CO₂ emission. Along with these benefits, materials degradation issues have also been emphasized in the last decade. Aqueous...
The thermal degradation of structural materials is considered to be a key factor for evaluating the lifetime of current nuclear power plants. Ni-based and Fe-based alloys, such as 690, 625, 304, and 316, are widely used in nuclear industry as structural components due to the extraordinary corrosion resistance and mechanical...
New low enriched uranium (LEU) fuels are being developed for replacement of high enriched uranium (HEU) fuels in high power research reactors. U-Mo LEU plate fuels have been identified as a candidate for replacement of current HEU fuels. However, U-Mo fuels tend to exhibit accelerated swelling typically at fission densities...
The corrosion resistances of several alloys were investigated to optimize performance and cost in seawater and supercritical CO2 environments. Many alloys are prone to corrosion in seawater and/or supercritical CO2 containing impurity environments. Exposure and electrochemical experiments were conducted in both environments to evaluate alloys’ corrosion resistance. In seawater corrosion...
The corrosion behaviors of carbon and stainless steels were investigated in supercritical CO₂ (sCO₂ ) containing H₂O and O₂ simulating conditions that exist in direct sCO₂ power cycle heat exchangers. Thermodynamic properties of CO₂-H₂O-O₂ systems related to the corrosion phenomena were determined using NIST software. The exposure tests of the...
Mechanical property degradation due to isothermal ageing is of potential concern for alloys based on the Ni-Cr binary system (e.g., Inconel 690, 625), particularly in nuclear power applications where component lifetimes can exceed 40 years. In the present research, the disorder-order phase transformation, which is the primary mechanism of ageing,...
CPM-M4 tool steel is a commonly used knife blade material due to its high strength and wear resistance. The goal of this thesis is to understand how heat treatment parameters affect blade performance and microstructure.Five heat treatments were applied to CPM-M4 steel by varying austenitizing and tempering temperatures. The microstructures...
This work explores the mechanical properties of single-phase niobium alloy C103 from room temperature to 600°C for the purpose of expanding safe uses of the material into new applications. The study utilizes a symmetrically notched triaxial tensile specimens to manipulate the internal stress field in order to observe the changes...
Nickel (Ni)-based alloys with a high chromium (Cr) content are frequently employed in applications where elevated temperatures and/or corrosive environments are present due to their excellent corrosion resistance and mechanical properties. However, a gap exists around the formation, and kinetics of long-range order (LRO) Ni2Cr phase in both model binary...
This work explores the hypothesis that proton irradiation is a feasible alternative to simulate accelerated thermal aging for Ni2Cr long-range ordered phase formation within NiCr and NiCrFe alloys. In this study, various model alloys and commercial alloys 690 and 690+P (0.01 wt.% P) were subject to 2 MeV proton irradiation...
Directed energy deposition and laser cladding technologies are suitable advanced manufacturing techniques for applying corrosion-resistant claddings to large carbon steel components. In this work, we clad 309L stainless steel wire onto carbon steel substrates and examine the effects of cladding parameters (laser power and travel speed) on metallurgical bonding, composition,...
The corrosion resistance of steels and nickel based alloys was investigated in supercritical CO2 (sCO2). Two types of experiments were conducted. The first set of experiments were conducted in a low temperature aqueous environment to simulate conditions that would exist in direct sCO2 power cycle low temperature heat exchangers. The...
The advent of supercritical CO2 as a new heat-exchange medium has seen strong interest from the power industry and the energy research field recently. It is advan- tageous in comparison with other heat-exchange cycles, as it can be operated safely at much higher temperatures and pressures, thus increasing the thermal...
High purity niobium metal is used in the construction of superconducting radio frequency (SRF) cavities in superconducting particle accelerators, such as the Large Hadron Collider (LHC) at CERN or the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. The usual method for characterizing the impurities in this niobium, the...
Duplex stainless steels (DSS) are an attractive potential material in nuclear power generation systems due to an excellent combination of corrosion resistance, strength, toughness, and affordability. Thermal embrittlement caused by phase instability in the temperature range of ~300-550°C severely limits the service temperature of DSS. The rate of embrittlement varies...
Variations in heat treatments have significant effects on the microstructure of tool steels. For CPM-M4 tool steel, the changes in microstructure and mechanical properties were observed based off of variations in temperature. Five heat treatments with constant exposure time and variable austenitizing and tempering temperatures were performed on samples of...
Molten salts have been targeted as a promising coolant for next generation reactors due to their high boiling point, heat capacity, and thermal conductivity. Despite these benefits, molten salt systems present unique materials compatibility issues, highlighted by the aggressive corrosion attack and dealloying typically seen on materials in these environments....
The monolithic (plate type) Uranium 10 wt.\% Molybdenum (U-10Mo) fuel system is promising for a variety of applications, most notably for the replacement of highly enriched uranium (HEU) fuels with low enriched uranium (LEU) fuel in United State High Performance Research Reactors (U.S. HPRRs).
Phase transformations and secondary phase formation...
Oxide growth is a common phenomenon on aluminum alloy cladding surfaces in nuclear research and test reactors. Without better understanding of oxide growth, excessive oxide build up on the cladding surface reduces heat transfer capability from fuel to coolant and causes safety concerns due to the potential cladding rupture or...
There is a growing need for individualized instructional designs in 4-year institutions due to: 1) growing undergraduate enrollment trends across the U.S., 2) broader diversity in students backgrounds, and 3) the growing prevalence of asynchronous remote learning. With the growth in computer technology in education, tools such as adaptive intelligent...
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Julie D. Tucker Milo D. Koretsky
There is a growing need for individualized instructional
Time-dependent crack growth mechanisms in Alloy 617 at 800°C in air were studied using compact tension samples machined in the L-T direction, cracked at temperature using an induction furnace and servo-hydraulic load frame. The application of different loading waveforms, including triangular, hold time, and sustained loading, were studied with relation...