Lognormal probability fragility distributions have been traditionally used to develop fragilities in nuclear plant probabilistic risk assessments. An enhanced non-parametric code-based (NPCB) methodology is presented in this paper for fragility analysis with application to wind pressure fragilities. Arbitrary probability distributions (i.e., non-parametric) can be used in the modeling of the individual factors and the uncertainty parameters. The method incorporates pressure zone and enclosure state (internal pressure) logic that is based on well-established wind code design principles. The NPCB methodology provides for more accurate modeling of wind pressure fragilities and reduced conservatisms in the important lower tail of the fragilities.
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