The Lifetime Of A Nuclear Power Plant Essay

776 WordsMar 2, 20164 Pages
The lifetime of a nuclear power plant is planned to be 40 years. Recently there are trails to raise this life in new constructions as well as the old ones to 60 years (1-4). During this prolonged lifetime components are exposed to degradation that may affect safe operation of the plant. Such influences affect pressure retaining items of the plant including reactor pressure vessel, reactor piping, bolting and threaded fasteners, steam generator materials and several other items (5). The Reactor Pressure Vessel (RPV) is the most critical component in the LWR pressure boundary. It is the only component in this boundary whose failure is considered to be of such low probability that it is considered essentially incredible. NRC regulations require that RPV steels maintain conservative margin for fracture toughness so that flaws do not threaten the integrity of a RPV during either normal operation and maintenance cycles or under accident transients such as Pressurized Thermal Shock (PTS) (6). The major technical issues regarding aging of RPV include: high fluences, for long times that may lead to high emrittlement creating large uncertainties for emrittlement predictions (7). Increasing nickel content in the RPV steel, all other factors being equal, causes increasing emrittlement (7). The degradation mechanisms that may affect RPV include Irradiation embrittlement, Thermal ageing, Temper embrittlement, Fatigue and Corrosion (8). Concerning nuclear piping the main degradation

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