Publication Date

8-2019

Date of Final Oral Examination (Defense)

6-13-2019

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Materials Science and Engineering

Department

Materials Science and Engineering

Supervisory Committee Chair

Brian J. Jaques, Ph.D., P.E.

Supervisory Committee Member

Michael Hurley, Ph.D.

Supervisory Committee Member

Clementè J. Parga, Ph.D.

Creative Commons License

Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

Abstract

The effect of sample geometry, welding strategies, atmosphere, plastic deformation, and rapid heating on the oxidation behavior of zirconium alloys has been investigated in this work. The goal of this work was to determine which zirconium alloy would be best suited as nuclear fuel cladding material in the Transient Reactor Test (TREAT) facility at the Idaho National Laboratory (INL), which has unique operating conditions compared to typical reactors. TREAT is air-cooled, operates at high temperatures (400-600 °C), and produces rapid transients (≤ 700 °C/s). Additionally, TREAT’s cladding geometry is unique in that it has chamfers and welds. Alloying elements such as Fe, Sn, Cr, and Nb are typically added to zirconium and can drastically alter the corrosion properties of the material. The effects of such fabrication on the oxidation behavior of zirconium alloys is not well documented in literature and no direct comparison is provided for the alloys of interest, thus it is unclear how these alloys will behave under TREAT’s conditions.

Isothermal and non-isothermal oxidation studies were completed on pure Zr, Zircaloy-3 (Zry-3), Zircaloy-4 (Zry-4), Zr-1Nb, and Zr-2.5Nb plate specimens in both Ar+20%O2 and N2+20%O2 to study the effect of nitrogen on the oxidation behavior. Electron beam welded (EBW) and tungsten inert gas (TIG) welded Zry-3, Zry-4, and Zr‑1Nb tube samples were oxidized under rapid heating and isothermal conditions in dry and humid N2+20%O2. Through these studies, the effect of chamfering, welding, humidity, and rapid heating were characterized. Macroscopic images of the samples were taken after oxidation, the oxide thickness was measured, and mass gain data was used to determine the oxidation rate constants and activation energies.

It was found that Zry-3, Zry-4, and Zr-1Nb experience faster oxidation in N2+20%O2 than Ar+20%O2 at 800 °C, while Zr and Zr-2.5Nb were relatively unaffected. Zry-3, Zry-4, and Zr-1Nb were found to experience accelerated oxidation in the weld region. Additionally, Zry-3 and Zry-4 experienced accelerated oxidation at the chamfers, while the chamfered region of Zr-1Nb experienced less oxidation. In all oxidation experiments, Zr‑1Nb had the most favorable oxidation behavior.

DOI

10.18122/td/1591/boisestate

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