Non-Destructive Testing for Ageing Management of Nuclear Power Components

Abstract

Worldwide a renaissance of the nuclear industry is obviously taken place and many countries favour nuclear power as one reliable opportunity to generate electrical energy at very low CO2 generating rates in order to avoid the green house effect in the earth atmosphere. However, since 1986 when the Tschernobyl accident was happening, nearly nowhere new nuclear power plants were established. The People Republic of China, India and in the last decade Japan, Finland and France are the exception. In other words, existing supply chains of former manufacturers were mainly destroyed or have changed its technical application field. Furthermore, a lot of technical expertise was lost as younger generations were influenced politically to find its interest in other scientific areas other than in nuclear physics or nuclear engineering. Even if we can observe today a change in mind in many countries concerning the acceptance of nuclear power the question seriously is to answer: Will we find enough well skilled technicians to reliably build all the planned nuclear power plants in the future? Therefore, life extension of existing plants the more plays an important role. This is truer as we have learnt in the last decades how many potential we have for life time extension even if we take into account ageing phenomena concerning the materials as thermal ageing, fatigue and neutron embrittlement when we think at steel components in the primary circuit; as there are the reactor pressure vessel, heat exchangers, surge line, pressurizer vessel, main cooling pumps and pipe lines. However, as in different countries life extension to an over all life time of 80 years is in discussion in future we have to take into account the infrastructure, i.e. bridges nearby, important for fluid traffic, emergency current generators, the concrete components of the containment and the cooling towers but also ageing phenomena of electric cable insulation, etc. Within these life time extension strategies the methodology of a continuously applied ageing management worldwide is seen as an important measure to guarantee nuclear safety. Besides the application of standardised non-destructive testing (NDT) technology during inservice inspection trials in order to perform a diagnosis of the material states online structural health monitoring of components by enhanced and intelligent NDT-sensors and sensor-networks will play a forthcoming future role. In Germany actually code-accepted procedures to perform ageing management were finally discussed and approved by the authorities. However, research and development in the last