Figure 3-1 identifies the specific point where the analyst must move beyond the
general outline of this Standard and use the graded approach to specifically
determine appropriate hazard analysis methodology. Application of a graded
approach is based on the judgment and experience of the analysts and results in the
selection of a hazard evaluation technique such as Preliminary Hazard Analysis
(PHA), HAZOP, etc. As previously noted, more elaborate techniques will
generally be associated with more complex processes. Experience and capabilities
of analysts are also a major consideration in efficient performance of a
comprehensive hazard evaluation.
Systematic application of the chosen techniques to the operations in a facility
generates a number of basic accidents based on types of events and system
performance in response to the events. These accidents can be binned in
accordance with predefined consequence and frequency ranking thresholds.
Products of the hazard evaluation include:
Identification of planned design and operational safety improvements.
Summary of defense in depth including identification of safety-significant
SSCs and other items needing TSR coverage, including relevant programs
covered under TSR administrative controls.
Summary of significant worker protection features including identification
of safety-significant SSCs and relevant programs covered under TSR
Summary of design and operational features that reduces the potential for
large material releases to the environment.
Selection of a limited set of bounding accidents (i.e., DBAs) to be further
developed in Section 3.4, "Accident Analysis."