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Evaluation Methods for Flow Accelerated Corrosion and Liquid Droplet Impingement in Nuclear Power Plants
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Authors : Shunsuke Uchida1, Masanori Naitoh1
Hidetoshi Okada1, Seiichi Koshizuka2
Derek H. Lister3
Company : 1 Institute of Applied Energy, Japan
2 Graduate School of Engineering,
University of Tokyo, Japan
3 Department of Chemical Engineering,
University of New Brunswick, Canada
Country : Japan
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Topics :
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FAC Prediction tools
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ABSTRACT :
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Overlapping effects of flow dynamics and corrosion are important issues to determine reliability and lifetime of major structures and components in light water reactor plants. Flow accelerated corrosion (FAC) and liquid droplet impingement LDI are typical phenomena due to both interactions. In order to evaluate local wall thinning due to FAC and LDI, a 6-step evaluation procedure for each has been proposed.
| (1) For FAC wall thinning evaluation, |
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(i) Obtain the flow pattern along the flow path with a 1D computational flow dynamics (CFD) code, and then, calculate corrosive conditions, e.g., oxygen concentration along the flow path, with a hydrazine oxygen reaction code. |
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(ii) Calculate the mass transfer coefficients at the structure surface with a 3D CFD code to evaluate high risk zones for FAC occurrence by coupling major parameters, and then, calculate wall thinning rates with the coupled model of static electrochemical analysis and dynamic double oxide layer analysis at the identified high FAC risk zones. |
| (2) For LDI local wall thinning evaluation, |
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(i) Calculate the flow pattern of liquid droplets in high velocity steam, determine the possibility of their collision with the pipe inner surface, and then, calculate the frequency of oxide film rupture due to droplet collision. |
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(ii) Evaluate high risk zones for LDI occurrence by coupling major parameters, and then, calculate wall thinning rates at the identified high LDI risk zones. For the region with higher steam velocity than 200 m/s wall thinning rate is determined mainly by erosion (LDI (mechanical)), while for that with lower velocity than 100m/s it is determined by corrosion process (LDI (corrosion)).
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(3) Make a final evaluation of residual life and the effectiveness of countermeasures.
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Speaker Biographical Information
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Shunsuke Uchida (B.S., Physics, Osaka University, PhD, Nuclear Engineering, University of Tokyo) has been a research fellow at Institute of Applied Energy and a research consultant at Japan Atomic Energy Agency after he retired from Tohoku University in 2005. He has 30 year experience with water chemistry of nuclear power systems, especially related to shutdown radiation reduction and mitigation of corrosive conditions for core internal materials and fuel claddings. His latest concerns are on the effects of hydrogen peroxide on corrosion of stainless steel in high temperature pure water. He is a fellow of the Atomic Energy Society of Japan. He was the previous chair of "Water Chemistry" Division of the Atomic Energy Society of Japan. |
Schedule : not yet available
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