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Normal operation of a nuclear power plant (NPP) generates cyclic changes of medium temperature, pressure and mechanical stresses or vibrations. Rapid shutdowns and / or load-following modes intensify the cyclic changes. The design lifetime of power plant components and equipment is limited by a conservatively defined number of such cycles of specific character. New design code requirements, the operator’s own safety management processes and regulatory demands specify increasing targets for fatigue safety margins. If the operational lifetime of a component is nearing the end of its design life it needs to be replaced.

AREVA NP‘s Nuclear Steam Supply System (NSSS) Advanced Fatigue Solution (AFS) extends the operational lifetime of components. AFS combines the high-accuracy local load monitoring system FAMOSi with graded fatigue assessment methods and the utmost level of expertise in fatigue assessment. The Simplified Fatigue Estimation (SFE) permits a basic decision about fatigue relevance. The Fast Fatigue Evaluation Module (FFE) offers a direct and highly automated way to calculate design code conforming cumulative usage factors (CUF) based on the simplified elasto-plastic fatigue analysis. Most accurate CUF’s are provided by application of the Detailed Fatigue Calculation (DFC) using high-end elastoplastic fatigue and ratcheting assessment methods.

AFS includes rainflow cycle counting with consideration of Environmentally Assisted Fatigue (EAF) according to NUREG/CR-6909 and ASME, RCC-M and KTA. It reduces in-service inspections and avoids replacement of components and is an excellent support for long-term operation (LTO) projects.

Interested in NSSS Fatigue Assessment and Evaluation?

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AREVA NP Germany

AREVA Fatigue Concept – a three stage approach to the fatigue assessment of power plant components

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