Long Term Strategy for Pipeline Replacement due to FAC Degradation at EDF Using BRT-CICERO™ Software

Abstract

The lifetime extension program of nuclear power plants (NPPs) requires the maintaining of its construction materials and equipment integrity with the respect to safety, availability and maintenance costs over the long term. Electricite de France (EDF) is aiming to extend the operation of its NPPs beyond 40 years. The surveillance of the Flow Accelerated Corrosion (FAC) degradation in the steam/water loop is one of the key issues for a safe and cost effective operation of NPPs. Indeed the pipe thinning may cause failures of components with the risks of the plant availability loss and personal injuries. FAC is a chemical corrosion mechanism resulting in wall thinning of piping, vessels and equipments made of carbon and low-alloy steel carrying liquid water or wet steam. BRT-CICERO™ software, originally developed by EDF in the early 90’s, is a FAC prediction tool taking into account all the known influencing parameters to identify the most susceptible pipe elements to FAC and calculate their remaining lifetime to reach the minimum allowable thickness. In the context of the NPPs lifetime extension, BRT-CICERO™ provides the capability to calculate the residual thickness at very long term for each component and to classify the pipe lines according to FAC susceptibility in order to conduct the long term maintenance strategy. The operating feedback (thickness and chemical alloy composition measurement) and the modification of parameters such as chemical conditioning and operating rate are also taken into account in the pipe lines ranking. The long-term strategy is systematically optimized by taking into account the rate of inspected components to determine, according to safety and cost considerations, the interest for replacing lines with FAC-resistant materials.© 2012 ASME