IAEA Coordinated Research Projects (CRP)

Review and Benchmark of Calculation Methods of Piping Wall Thinning due to Erosion-Corrosion in Nuclear Power Plants


Brief Summary

Even though industry efforts have been quite effective in reducing the number of piping and equipment failures caused by Flow Accelerated Corrosion (FAC), piping and components will continue to degrade as plants age. Guidelines on where and how to inspect (software predictions), how to perform chemistry improvements to reduce damage rates, and proposals of material upgrades for replaced components are challenged by new economic studies, reduced time outages, and personnel ageing. Events and benchmarking over the past years related to degradation and Flow Accelerated Corrosion incidents in Nuclear Power Plants (NPP), such as:

  • Mihama accident in 2004,
  • Benchmark by the Framatome's Owners Group in 2005 on existing prediction software,
  • IAEA International Conference on Flow Accelerated Corrosion in Moscow in 2009,
  • EdF's International Conferences on Flow Accelerated Corrosion in France in 2008, 2010 and 2013

have lead the International Atomic Energy Agency (IAEA) to organize a "Co-ordinated Research Project (CRP) on elaboration of Flow Accelerated Corrosion guidelines and benchmarking of prediction tools".


Background

The IAEA announced this project at the Moscow conference on FAC in April 2009 and at the French conference in 2010. In the early 1980s, several PWR plants experienced steam leakage due to piping erosion/corrosion. A pipe rupture accident at the USA Surry NPP in 1986 prompted utilities to work toward the development of a guideline for the management of pipe wall thinning.

Flow-accelerated corrosion is wall thinning of steel piping due to turbulent and fast flowing water or wet steam that wears away the protective film (oxide layer) and leads to continued corrosion of the underlying metal. FAC is a chemical effect that is primarily influenced by pH, hydrodynamics, oxygen, and temperature. The geometric aspects of the system design and piping layout play a big role in the occurrence of FAC. Wall thinning in piping and vessels because of FAC has caused sudden ruptures in high and moderate energy systems, resulting in plant transients and affecting safety/non safety related equipment by leaking steam and water and risking personnel safety.

All reactor types have experienced some type of FAC related events in their piping systems. Many utilities have started the analysis of pipe wall thinning phenomenon using the available large amount of measurement data from operating plants. Plants have had FAC campaigns implemented for many years, and even with a mature and established FAC approach, events continue to occur.


Overall Objective

The overall objective is to provide participants and the industry with:

  • references and boundary conditions for the use of the available prediction tools
  • a document to support the development of a solid technical base and serve as a guideline for FAC Programme

Recent Activities

  • Consultancy meeting (Jan 21 to 23, 2014) to develop FAC guidelines document and review benchmarking data to be sent to CRP participants;
  • Provision of initial FAC data for software model comparison under this CRP to CRP participants (Feb 12, 2014).
  • Research Coordination Meeting (RCM) for all CRP participants at AREVA headquarters in Erlangen, Germany (June 4 to 6, 2014). For RCM web page please click here. A consultancy meeting for CRP steering team members was held immediately prior to the RCM on June 2 and 3, 2014.


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