The purpose of this thesis is to broaden the tools and knowledge available for understanding the behavior of metals under irradiation to aid in the pursuit of advanced materials for deployment in Generation IV (Gen-IV) nuclear reactor designs. A mean-field study is conducted on a body-centered cubic (BCC) A-B binary metal alloy system. The performance of the simulated metal system is measured by assessing the degree of segregation that occurs at the grain boundary (GB) in the center of the one-dimensional simulation box. This mean-field method was developed using rate theory equations to observe the diffusion of defects and solute atoms in the binary BCC alloy modeled after a section of planes in the <100> direction of α-iron. The method in this thesis is adapted from a previous radiation-induced segregation (RIS) study that was similarly validated against thermal segregation isotherms.
This adapted simulation code was used to study RIS by varying the initial values and conditions across ranges relevant to Generation IV reactor designs. The simulations run with this code were centered around segregation energy and the diffusion coefficient relationships between defects and solute atoms. The most influential conditions applied to both the segregation energy and diffusion coefficient relationship test suites were the temperature and dose rate. The interplay of the various segregation energies, manipulated diffusion coefficients, temperatures, and dose rates is explored in this thesis. The code used in this thesis is presented as a modular framework for further parameter study with a clear direction for more complex alloys. / Master of Science / The growing electricity demand for more efficient, safe, reliable, and sustainable means of power generation requires research and subsequent implementation of advanced Generation IV (Gen-IV) nuclear reactor designs. These proposed designs operate under significantly more strenuous conditions from the perspective of materials used in constructing the reactor. Materials inside the reactor will experience temperatures, pressures, and radiation doses greatly exceeding those of previous generations: Gen II through III+. Metals are employed in almost every component inside a reactor and are particularly susceptible to the demanding conditions due to their tendency to lose their ductility under these stressors.
This thesis presents a diffusion-based code that models a binary metal alloy under conditions similar to those expected in Gen-IV reactors. The results of the code give insight into the prevalence of a phenomenon known as radiation induced segregation (RIS) in metals under these Gen-IV relevant conditions. The values input into the code have significant effects on the resulting RIS behavior of the metal alloy. This thesis presents correlations between the initial parameters and the amount of segregation this alloy experiences. The results of this thesis allow a sort of mapping of material parameters and operating conditions so that materials can be designed for optimal performance over the lifespan of the next generation of nuclear reactors. The code in this thesis was developed with the expectation that its modularity would be expanded upon to apply to more complex alloys under a broader range of initial conditions.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/96606 |
| Date | 29 January 2020 |
| Creators | Chan, Ryan James |
| Contributors | Mechanical Engineering, Hin, Celine, Farkas, Diana, Zhang, Jinsuo |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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