Materials management strategies for VVER reactors - Materials' Ageing and Degradation in Light Water Reactors - page 316

better operational conditions for components of the feed-water system and
for the steam generators as well.

8.6 Conclusion

A complex picture of ensuring and justifi cation 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 compre-
hensive plant lifetime management systems have been developed to ensure
the safety of LTO of VVER-440 and VVER-1000 type plants. Detailed stud-
ies 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 devel-
oping 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 compo-
nents are identifi ed which are signifi cant for safe LTO. An appropriate level of
understanding of the ageing phenomena has been reached and adequate age-
ing management programmes developed for ensuring the required status and
intended function for the long term. Revalidation of time-limited ageing anal-
yses also justify the safety of LTO, which is completed by the monitoring of
maintenance on performance criteria combined with the maintenance of envi-
ronmental qualifi cation 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 justifi cation
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.

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8.7 References

Brumovsky M. and Zdarek J. (2005). Integrated surveillance specimen program for
WWER-1000/V-320 reactor pressure vessels, Technical Meeting on Material
Degradation and Related Managerial Issues at Nuclear Power Plants, Vienna,
15-18 February 2005, IAEA Proceeding Series, 2006, pp. 171-178.
Brumovsky, M. et al. (2007) Prediction of irradiation embrittlement in WWER-
440 reactor pressure vessel materials, Problems of Atomic Science and
Technology, Series: Physics of Radiation Effect and Radiation Materials
Science No 6, pp. 72-77.
Erak , D.Yu . et al . (2007). Radiation embrittlement and neutron dosimetry aspects
in WWER-440 reactor pressure vessels life time extension, Second IAEA