Appeal No. 1997-3205
Application 08/389,545
Appellants recognized that conventional tube array failure modeling techniques suffer from the
disadvantage that large uncertainties in values of deterministic (i.e., Weibull) parameters cause a
"subsequent inability to obtain quantifiable confidence estimates of the minimum and maximum tube
repair requirements" (see specification, page 2). Appellants’ claimed method and system involve
providing an improvement over prior art deterministic modeling (see appellants’ Figure 4, showing
conventional Weibull modeling) of incorporating a probabilistic variation to produce an uncertainty
index (see appellants’ Figure 5, showing confidence levels using Monte-Carlo technique). The method
and system of claims 1 to 10 on appeal calculate and display such an uncertainty index to better predict
failure rates of tubes in the steam generators so that unscheduled plant shut-downs can be avoided (see
specification, pages 1 to 2). As indicated in the specification (page 7), the method and system for
generating an uncertainty index performs a probabilistic computation on a constant parameter of the
prior art deterministic model. Thus, a key difference between the prior art and the invention recited in
representative independent claim 1 on appeal is that an uncertainty index is generated in the recited
invention, as opposed to a best estimate curve (as in the prior art).
In general, appellant’s invention recited in representative independent claim 1 on appeal
provides a method for generating an index commensurate with tube array degradation over time,
wherein the index is generated from a distribution of degradation values which are commensurate with
an uncertainty as computed by a deterministic failure (i.e., Weibull) model (see claim 1 on appeal). By
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