Abstract: 
A probabilistic method for determining an operability interval for fasteners in a nuclear power plant assembly is provided. The probabilistic method includes determining or assuming a geometric distribution of a given initial condition of fasteners in the nuclear power plant assembly at an initial time T0; determining a future fastener failure probability model of the geometric distribution over time; generating a plurality of random future fastener failure patterns by applying the fastener failure model to the geometric distribution at a given time T1 > T0; postulating fastener spacing rules designed to evaluate the acceptability of fastener failure patterns for the fasteners in the nuclear power plant assembly; applying the fastener spacing rules to a plurality of randomly generated fastener failure patterns for the given time Tl to determine the probability of the randomly generated fastener failure patterns passing the fastener spacing rules at the given time T1; iterating, by a processor of a computer, the applying step for a given range of time values T2, T3,..., Tx >T0 and determining a maximum future time Tmax at which a predetermined acceptable probability of the fastener failure patterns passing the fastener spacing rules is met, thereby justifying the acceptability of the fasteners for continued operation of the nuclear power plant assembly; and determining the operability interval as being TmaxTO.
