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Vol.4 No.1 previous AA 39 -40-SP6(41-42-43-44)-NT 46 -47

Academic Articles
Regular Paper Vol.4No.2 (2012) p.63 - p.78
 

The Role of Flow in Flow-Accelerated Corrosion under Nuclear Power Plant Conditions

 
John M. PIETRALIK
 
Atomic Energy of Canada Ltd., Component Life Technology Branch
Chalk River, ON, K0J 1J0, Canada
 
Abstract
In a mechanistic model of flow-accelerated corrosion (FAC), one of the steps affecting the FAC rate is the mass transfer of ferrous ions from the oxide-water interface to the bulk of the flowing water. This step is dominant under alkaline conditions and high temperature, an environment frequently occurring in piping of nuclear power plants (NPPs). When the flow effects are dominant, the FAC rate is proportional to the mass flux of ferrous ions, which is typically proportional to the mass transfer coefficient in the flowing water. The mass transfer coefficient describes the intensity of the transport of corrosion products (ferrous ions) from the oxide-water interface into the bulk water. Therefore, this parameter can be used for predicting the local distribution of the FAC rate. The current paper presents a brief review of plant and laboratory evidence of the relationship between local mass transfer conditions and the FAC rate with examples for bends. It reviews the most important flow parameters affecting the mass transfer coefficient and, as an example, shows correlations for mass transfer coefficients in bends under NPP conditions. The role of geometry, surface roughness, wall shear stress, upstream turbulence, and locally generated turbulence is discussed. An example of computational fluid dynamics calculations and plant artefact measurements for short-radius and long-radius bends are presented.
 
Keywords
Flow-accelerated corrosion, flow, mass transfer coefficient, turbulence, surface roughness, geometry, ferrous ion, mass flux, bends, wall thinning, nuclear power plants, piping
 
Full Paper: PDF EJAM Vol.4No. 2 pp.63-78 "The Role of Flow in Flow-Accelerated Corrosion under Nuclear Power Plant Conditions
Article Information
Article history:
Received 31 March 2012
Accepted 9 July 2012