in the frequency with which any performance metric occurs. The resulting information and knowledge base could complement and contribute to the credibility of the QMU process. As noted in Appendix A, probabilistic risk assessments greatly expand the knowledge base of systems while facilitating their analysis and fundamental understanding.

Recommendation 1-7. The national security laboratories should investigate the utility of a probability of frequency approach in presenting uncertainties in the stockpile.12

As noted in the simplified example illustrated in Figure 2-1 and further discussed in Appendix A, representing failure modes in terms of probability of frequency could provide decision makers with a richer understanding of the uncertainties—and a clearer notion of how to address them—than could estimating the reliability or M/U.


See, for example, J.C. Helton and R.J. Breeding, Calculation of Reactor Accident Safety Goals, Reliability Engineering and System Safety 39(2)(1993): 129-158.

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