Engineered safeguards systems components

In both approaches - SMA and seismic PSA - the focus is on the plant-level robustness, i.e., it is essential that the safeguard systems of the plant be able to fulfill their safety function, even if individual equipment items may have failed. The analysis of the plant-level robustness takes into account the multiple lines of defense and the safety concepts - such as redundancy and diversity - implemented in the engineered safeguards. Ultimately, however, the plant-level robustness can be traced back to the seismic margin of individual systems, structures, and components (SSC). Hence, before discussing seismic robustness in terms of plant-level safety functions, the concept of seismic margin is introduced for individual SSC. 

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