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MATERIALS ENGINEERING

SEMINAR

“Evaluation of Radiation Damage in Materials Using Extended X-ray Absorption Fine Structures (EXAFS)”

By

Gyuchul Park

Purdue MSE Ph.D. Preliminary Exam

Advisor: Professor Maria A. Okuniewski

ABSTRACT

With an effort to substitute low-enriched uranium (defined as less than 20% ²³⁵U) for highly enriched uranium (defined as more than 20% ²³⁵U) by Reduced Enrichment for Research and Test Reactors program launched in 1978, uranium molybdenum (U-Mo) alloy has been considered as a promising nuclear fuel material for future research reactors. U-Mo alloy fuel displays great irradiation behavior because, γ-phase uranium, stable above 771°C, can be obtained at the operating temperature of research reactors (below 250°C) by alloying molybdenum in uranium under quenching conditions. An understanding of the irradiation behavior of U-Mo alloy fuel is crucial in order to improve the fuel performance. Accordingly, Extended X-ray Absorption Fine Structure (EXAFS), which uses a synchrotron x-ray source, is a useful experimental technique to study radiation damage on the atomic level in materials because changes in local structure such as atomic distance and coordination number can be probed within 5-6 Å from an absorbing atom. In the following document, the general radiation-induced defects observed in irradiated materials are reviewed. Then, the background of EXAFS is briefly introduced and followed by a discussion of how EXAFS can be utilized to investigate radiation damage in materials.

Keywords: Radiation Damage, Uranium-Molybdenum Monolithic Fuel Alloys, Extended X-ray Absorption Fine Structure (EXAFS).

Date: Friday, December 8, 2017

Time: 8:30 A.M.

Place: ARMS 1028