A complex picture of ensuring and justification of LTO of VVER plants has been given in this chapter. The VVER-440/213 model especially is discussed in detail.

In VVER operating countries, proper regulatory frameworks and compre­hensive plant lifetime management systems have been developed to ensure the safety of LTO of VVER-440 and VVER-1000 type plants. Detailed stud­ies and already approved cases of extension to plant operational lifetime demonstrate the feasibility of LTO of VVER plants.

Generally accepted principles for safety have been followed while devel­oping plant systems, which ensure that any SSCs will be covered by some of the plant programmes, and within the framework of the LTO programme, all conditions of safe operation will be ensured. Structures, systems and compo­nents are identified which are significant for safe LTO. An appropriate level of understanding of the ageing phenomena has been reached and adequate age­ing management programmes developed for ensuring the required status and intended function for the long term. Revalidation of time-limited ageing anal­yses also justify the safety of LTO, which is completed by the monitoring of maintenance on performance criteria combined with the maintenance of envi­ronmental qualification and replacement and reconstruction programmes.

Best international practice and state-of-the-art methodologies have been applied while performing the particular tasks for preparation and justification of LTO and licence renewal. However, as demonstrated, any good examples and experiences should be adapted in creative ways, taking into account the design features, national regulations and existing plant practice. In this way the strategy of VVER operators to operate safely for as long as possible with economic advantage and at higher power levels will be ensured.