The development of AMPs has to begin with the identification of the ageing mechanisms, critical locations and effect of ageing on the intended safety function. When an AMP is developed for a complex structure or compo­nent, like the reactor or steam generator, several mechanisms and critical locations can be identified. The material, conditions and stressors are con­sidered at this step of the AMP development. Examples for the mechanisms are listed in the Table 8.4.

As a matter of fact, the structuring of the AMPs together with the identifi­cation of the commodities is not independent from the identification of ageing mechanisms. For example, a commodity group can be defined as follows, see Table 8.7 : Safety Class 3 + Piping and pipe elements + working in prepared water (e. g. feed-water line) + carbon steel. From experience, the dominating ageing mechanism of this group is flow-accelerated corrosion (FAC), a deg­radation process resulting in wall thinning of piping, vessels, heat exchanger and other equipment made of carbon and low alloy steel. This degradation mechanism of the identified commodity group should be addressed by proper AMP, which can be developed for example via application of the COMSY system (Zander, Nopper, Roessner, 2007) used by several VVER operators.