Quantifying Oxide Layer Growth at Low Pressures and Temperatures for Aluminum Alloy 6061
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IN nuclear research and test reactors (RTRs), aluminum alloys are often used as cladding material for fuel elements. These RTRs sit in pools of subcooled light water that remove heat from the fuel during reactor operation. Over time, the aluminum cladding exposed to coolant corrodes and creates an oxide layer, which acts as a form of thermal insulation. The growing thermal insulation results in an increase in the fuel temperature
JULIE D. TUCKER, YOURAN WEI, PRATIK V. MURKUTE, and BRADY J. GIBBONS are with the School of Mechanical, Industrial and Manufacturing Engineering, Oregon State University, 204 Rogers Hall, Corvallis, OR 97331. Contact e-mail: [email protected] WADE R. MARCUM is with the School of Nuclear Science & Engineering, Oregon State University, 116 Radiation Center, Corvallis, OR 97331. Contact e-mail: [email protected] O. BURKAN ISGOR is with the School of Civil and Construction Engineering, Oregon State University, 101 Kearney Hall, Corvallis, OR 97331. Manuscript submitted July 11, 2016. Article published online May 13, 2019 3388—VOLUME 50A, JULY 2019
and is a cause for preventive action due to safety concerns resulting from potential clad blistering, breach, and most extremely—fuel melt. The purpose of this project is to identify the oxidation rate of an aluminum alloy 6061 under low-temperature and pressure conditions, similar to those found in many RTRs. The design guidelines of RTRs are set from data collected and correlations formed for high-temperature and high-pressure systems. Some RTRs, such as those at universities, operate at much lower temperatures and pressures but are held to the same design guidelines. In this paper, we generate corrosion data under similar conditions relevant to lower temperature/pressure RTRs and compare it to the correlations developed for high-temperature/pressure RTRs to assess the accuracy of this current practice. Identifying conservatism in the existing approach may warrant design guideline changes and development of new correlations. This paper also studies the oxidation rate differences between as-received 6061 samples to those treated with a process to form a boehmite (c-AlO(OH)) oxide layer prior to use. This prefilming process is standard practice in the RTR industry and is performed by exposing aluminum alloy plates to deionized water at a high temperature in an autoclave.[1] This prefilming process is METALLURGICAL AND MATERIALS TRANSACTIONS A
5913 ; k ¼ 1:2539 105 exp Tx
expensive, and if the results of this project show that it is unnecessary, its elimination could provide substantial cost savings.
II.
BACKGROUND
The corrosion rate of aluminum alloys has been studied under high-heat flux, high-temperature, and high-pressure conditions to support several RTR safety analyses such as the High-Flux Isotope Reactor (HFIR) and the Advanced Test Reactor (ATR).[2–7] However, the corrosion rate of aluminum alloys has not been studied under low-temperature and low-pressure conditions, which are the explicit conditions that ma
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