Operational experience provides the basis for preparing the strategy of age­ing management. The experiences of the plants regarding degradation of the lifetime-limiting structures and components have primary importance. These are the non-replaceable long-lived structures and components. In the VVER-440 plant design, lifetime-limiting structures and components are the containment building, reactor pressure vessel and the steam gen­erator (Katona et al. , 2005, 2009b; Katona and Ratkai, 2008). Unlike the VVER-1000 and PWRs, the steam generators are practically irreplaceable in the VVER-440/213 design. In the case of the VVER-1000, the most impor­tant lifetime-limiting structures and components are the containment and the reactor pressure vessel. The proven design solutions of the VVER-440 were incorporate in the VVER-1000 design: the horizontal steam generator and also materials selection.

Alongside this, ageing the mechanical commodities, structures other than containment and electrical equipment, are also important for the develop­ment of an ageing management strategy. With this in mind, the operational experience of the plants varies because of the design variation of these com­ponents and structures at different plants.