Probabilistic analysis of safety: Increasing the reliability and safety of nuclear power plant components - Probabilistic Safety Assessment for Optimum Nuclear Power Plant Life Management (PLiM) - page 202

6.3 Relative increase of the rate of failure with time for different
groups of equipment: 1) RWST level sensors; 2) pumps of the
spray system.

Time, years

6.4 Relative increase of the probability of failure on demand
for electric drives of centrifugal pumps: 1) log-linear model; 2)
Weibull model.

reliability parameters in 40 years of operation varies in the range 2-10. An
exception is the group of equipment 'electric drives of centrifugal pumps'
for which the reliability models indicate a large increase of the probability
of failure demand with time (Fig. 6.4). For this group, the best extrapolation
of the primary data is obtained by the log-linear model ( P = 0.98). The
relative increase of the probability of failure at 40 years in operation is
more than three orders of magnitude. At the same time, the Weibull model,
which is also characterised by good extrapolation of the primary data with
the significance level of 0.96, shows the relative increase of the probability
of failure at 40 years in operation by approximately 20 times.
For all the components for which the ageing effects were taken into
account, it was assumed that technical maintenance is carried out without
reconditioning.
Calculations were performed for units operated for 10, 20, 30 and 40
years. The results were compared with the basic data (section 6.1).

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