Corrosion in nuclear power plants and it implication in the leak before break criteria

The corrosion in a general way can be defined like a chemical or electrochemical reaction, which is carried out in the surface of the metallic materials exposed to a specific medium. Due to the operation conditions in the nuclear power plants are practically fixed and its modification in most of the cases is difficult or expensive, the natural tendency to prevent the corrosion has been generally directed toward the selection of materials. Numerous materials have been employees as substitute of the traditional steels, among other the stabilized stainless steels, those of extra low carbon and numerous nickel base alloys. The basic evaluation that establishes the approach Leak before break (LBB) it involves the analysis by means of 'fracture mechanics' of a postulated crevice that it crosses the thickness of the material, which causes a same flight, with a margin of safety, to the detection limit that it has for a shutdown of the reactor. Due to the crevice size postulated, it cannot be established highly starting from the mechanical properties of the material since these its will be affected by the corrosion mechanisms that can settle down, it was determined that the implementation of the LBB criteria, it cannot be established for components or systems that its are susceptible of suffering corrosion. (Author)