Formulation of SACs - Continued

DOE-STD-1186-2004

to be implemented (i.e., important procedural features, including interfaces with sensors, etc.)

should be presented. Pertinent aspects of the SAC that relate directly to the safety function,

such as qualifications of personnel required and time available to perform associated tasks,

should be described. Finally, an evaluation of the SAC that demonstrates its capability to

perform the expected safety function should be described for each SAC.

The DSA should provide information (generally Chapter 5 of a DSA based on DOE STD-3009)

to support the derivation of hazard controls described in the TSR document. This Chapter

content is the linking document between the DSA hazard analysis that results in the designation

of SACs and their required safety functions and attributes, and the TSR document. TSR and

SAC procedure writers will refer to the DSA through this chapter to identify the accident

scenarios that generated the need for the SAC (in Chapter 3), and information on its safety

function and required attributes. Chapter 5 should provide a summary description of this

information and references to the supporting information in Chapters 3 and 4.

The concepts of validation and verification are important to the formulation of SACs. These

concepts, as they apply to SACs, are discussed below.

Validation: The functional requirements and performance criteria for safety SSCs are

identified to support the safety functions identified in the DSA and to support subsequent

derivation of TSRs. The formulation of SACs should include a similar process that validates

plant operators can perform the task(s) called for in an SAC within the timeframes assumed

in the DSA. If SACs require operator action and perform a function similar to a safety SSC,

assurance should be provided that the operators can adequately perform their required

tasks by analyzing the following human performance factors at a minimum:

Adequacy of the description of the task in facility procedures

Level of difficulty of the task

Design of the equipment and feedback, e.g. indicators, alarms, etc.

Time available to do the task or recover an error

Stress levels induced by the external environment, e.g. noise, heat, light and

protective clothing worn.

Formal engineering calculations may be necessary to ensure that plant operators have the

appropriate time and resources to carry out the required tasks. For example, if it is

assumed that operators will take actions to detect and isolate a leak, flow rate calculations