TIME-DEPENDENT UNAVAILABILITY OF AGING STANDBY COMPONENTS BASED ON NUCLEAR-PLANT DATA

The time-dependent unavailability of periodically tested and repaired aging components which have first failure densities satisfying the nor mal and the Weibull distributions with aging threshold are investigate d using a generalized formula for surveillance testing and repair. The formalism is applied to the case of periodic, good-as-old surveillanc e testing with good-as-new repair. Actual aging data are used. The res ults show that aging can have significant impacts on the availability and reliability of a component and the system containing the component . More specifically: a) the time dependent unavailability of aging com ponents can go through large swings with varying magnitude in time bef ore stabilizing to the standard saw-tooth behavior of periodically tes ted components with constant failure rates, and b) approximating the u navailability by a constant failure rate can lead to large differences even when an average unavailability is calculated.