Hess et al. (ICONE18, 2009) suggest research is needed in
support of the Risk-Informed Safety Margin Characteristic (RISMC)
methodology in order "to address completeness of analysis,
treatment of uncertainty, and efficiency of computation so that
more accurate and cost-effective techniques can be used to address
safety margin characterizations." The proposed project directly
supports all three elements of this call, in the following manner.
Task 1 builds upon previous work of the investigators (Shawn
Rodgers et al., "Toward Quantification of the Uncertainty in
Estimating Frequency of critical station Blackout," Procs. of the
International Conference on Mathematics and Computational Methods
Applied to Nuclear Science and Engineering (M&C 2011), Rio de
Janeiro, May 8-12, 2011, in press) to improve the efficiency of
computational estimates of the frequency of potential initiating
events arising from the very important issue of Loss of Offsite
Power (LOOP) events. The efficiency issue arises because this
previous work obtains these estimates in the form of computational
evaluation of a multidimensional "nonrecovery integral" having
dimensionality equal to the number of backup power trains.
Evaluation of multiple integrals can be a computationally very
intensive process. (In the prior work cited it is shown that all
previously developed approaches known to the investigators are
based upon approximations that in one manner or another approximate
the recovery integral in terms of single integrals; results in that
work also suggest frequency estimates from numerical evaluation of
the multidimensional reentry integral are capable of significantly
reducing excess overconservatism inherent in even the most
realistic of those prior approaches.)
Task 2 is directed toward analysis of completeness of the RISMC
approach. Initially (Subtask 2.a) the focus will be upon
exploration of issues, especially precision in the associated
definitions of "capacity" and "loading," arising in the mapping of
specific safety-related issue into the abstract RISMC framework (S.
Hess, "Framework for Risk-Informed Safety Margin Characterization,"
EPRI Report Number 1019206, December 2009.). The subsequent Subtask
2.b will explore the utility of an expanded taxonomy for
safety-related analyses that classifies different approaches not
only by the deterministic or stochastic nature of the related
safety margins, but also by the corresponding properties of the
associated estimates of capacity and loading.
Task 3 will further treat improved computational methodologies,
but rather then efficiency (as in Task 1) the focus will be upon
expanding the domain of application, especially beyond LOOP events.
Task 4 will address the important (and difficult) issue of
quantifying uncertainty, again with LOOP events taken as a primary
The STP Facility
- S. Rodgers, C. Betancourt, E. Kee, P. Nelson, and P. Rodi,
"Toward Quantification of the Uncertainty in Estimating Frequency of Critical Station Blackout,"
International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2011), Rio de Janeiro, Brazil, May 8-12, 2011. See Document
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