PSI - Issue 16

Peter Trampus / Procedia Structural Integrity 16 (2019) 161–168

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Peter Trampus / Structural Integrity Procedia 00 (2019) 000 – 000

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greenhouse gas emission. Decarbonization of the energy systems is crucial, and the nuclear power plants (NPPs) providing about 5% of the entire primary energy production are one of the major options for it. Despite the attractive feature, the prospects for the expansion of nuclear energy remain decidedly dim in many parts of the world. One of the fundamental problems seems the cost of the new build plants. Also, experiences of nuclear construction projects have demonstrated repeated failures of construction management practices in terms of their ability to deliver products on time and within budget. Consequently, the value of operating NPPs have increased, and NPP life management, especially service life extension became a worldwide issue. The goal of this paper is to place non-destructive evaluation (NDE) in the context of NPP life management, life extension and to show its increasing role in ensuring plant long-term operation. Life management is a complex of conscious and integrated technical measures and complementary economic planning to (i) optimize the operation, maintenance and service life of technological systems, structures and components (SSCs), (ii) maintain an acceptable level of performance and the quality/safety of production, and (iii) maximize return on investment over the plant service life. Service life (operating life) extension is one of the most frequent goal of life management. Today, it became a routine activity worldwide. Chance for it has been given by the typically conservative design of the NPPs, the huge and rapid development in the area of production technology, informatics, micro- and nanoelectronics, as well as a large extension in knowledge basis of materials science, fracture mechanics, non-destructive testing (NDT) and NDE, technical diagnostics and other disciplines. Fig. 1 shows the age of the world’s operating reactors, IAEA (2017). Of the 450 nuclear power reactors, 293 have been in service for 30 years or more. When a reactor reaches the end of its design life, it undergoes a safety review and an ageing assessment of its essential SSCs for validating or renewing its license to operate for terms beyond the originally intended service period. 2. Life management and life extension of NPPs

Fig.1. Distribution of operational power reactors by age, as of 31 December 2016.

3. Ageing management, in-service inspection, NDE

Typically, the NPPs operate a comprehensive ageing management program which is a harmonized activity of engineering, operations, maintenance and inspection actions to control within acceptable limits the ageing degradation of SSCs. One of the substantial elements of the ageing management program is the in-service inspection (ISI). ISI is basically a periodic NDT/NDE of the passive SSCs to provide information about their possible deterioration so as to determine whether they are acceptable for continued safe operation or whether remedial measures should be taken. NDE as the major area of ISI delivers essential input in terms of existence, size and other characteristics of flaws to assess the components’ structural integrity on the basis of fracture mechanics principles.