[en] As the field of probabilistic risk assessment (PRA) has matured, the trend has been toward larger and more expensive studies. A state-of-the-art PRA now includes complex reactor system models; sophisticated quantification methods; and detailed analyses of human errors, dependent failures, and external events. For many applications, however, such full-scope assessments may not be cost effective. Sandia National Laboratories has evaluated how the scope of probabilistic risk assessments might be reduced when the primary desire is to develop insights into the risk-significant aspects of nuclear reactor design