In 2007, the American Society of Mechanical Engineers (ASME) Committee on Nuclear Risk Management (CNRM) formed a working group (WG) to develop probabilistic risk assessment (PRA) requirements for advanced light water reactors (ALWRs). Existing PRA Standard language (internal events, fire and external events) was developed for operating plants. The requirements in the existing, and possibly in the planned Standards, are not fully applicable for an ALWR from the design through initial operational phases. Furthermore the WG had a goal to determine if additional requirements were appropriate for design and operational features which might differ from operating plants. Consider for example: • Prior to completion of construction and initial operation, final design and operational information may not be available, and walkdowns of final, as constructed, features will not be possible; • Plant-specific operating experience will not be available; and • ALWRs may have features, such as passive systems and digital instrumentation and control (I&C), which may not be adequately addressed. The initial scope of this project has addressed internal events at power requirements. To identify new or revised requirements, the ASME Standard, Regulatory Guide 1.200 rev. 01, Regulatory Guide 1.206, and Draft Regulatory Guide 1.200 rev. 02 were reviewed in detail. In addition the results of a peer review of an ALWR in the design stage using the ASME Standard were considered. Draft requirements have been developed and are currently in review by the CNRM. The paper describes the approach, results and future actions to modify the combined Standard to address ALWRs.

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