Rabbat R. (ed.). Heavy component replacement in nuclear power plants: experience and guidelines

Vienna : International Atomic Energy Agency, 2008. 109 p. — (IAEA nuclear energy series, ISSN 1995–7807 ;no. NP-T-3.2). — ISBN 978–92–0–109008–9.The world’s fleet of nuclear power plants is, on average, more than 20 years old. Even though the design life of an nuclear power plant is typically 30–40 years, it is quite feasible that many nuclear power plants will be able to operate in excess of their design lives, provided that they operate safely.
Different material degradation mechanisms have been identified on components resulting from the ageing phenomenon. Time dependent changes in the mechanical and physical properties of system, structure and components (SSCs) are referred to as ageing. The effects of ageing lead to changes, with time, in the SSC materials, which are caused and driven by the effects of erosion, corrosion, varying loads, flow conditions, temperature and neutron irradiation.
Component replacement is often the most feasible solution to solve the effects of ageing associated with primary water stress corrosion cracking of alloy
600. Even if mitigation and/or repair were a local solution, replacement offers many advantages when addressing the assortment of potentially susceptible parts contained in a major component.
This publication is dedicated on heavy components replacement considered strategic for nuclear power plants life management, but not included in current maintenance activities carried out by utilities. The major and heavy components to be considered are: Steam generators of PWRs;
Reactor vessel head of PWRs; Reactor vessel internals of PWRs; Pressurizer of PWRs;
Reactor internal components of BWRs; Reactor coolant piping/recirculation piping of PWRs and BWRs; Steam generators and fuel channel and feeder pipes of PHWRs.