By William E Berger Jr., Senior Vice President, Fauske &
Associates, LLC When designing systems whose failure can result
in unacceptable losses, reliability becomes an important
consideration. Reliability is implemented through redundant
design and strict performance requirements for the components
used in these systems. This however may not be enough as
witnessed by the beyond design basis events at Fukushima, whose
consequences could not be protected against through redundancy.
There will be many lessons learned from this tragic event of
which one will be a closer examination of potential common cause
failures. It is these mechanisms which defeat the intent of a
redundant system design, one such mechanism is degradation due
to aging. Even though we analyze and test under accelerated
aging conditions, not all elements related to aging can be
addressed in the laboratory. Programs are needed which
investigate and analyze components in situ to ensure degradation
mechanisms are held in check. There are required