Functional Requirements - doe-std-3009-94_cn3

DOE-STD -3009-94

When describing the SAC, provide a basic summation of the physical

information known about the SAC, including tables or drawings showing

relevant information, such as instrumentation and other SSCs, physical

boundaries, approved storage areas, and operator routes or locations.

4.5.X.3

Functional Requirements

This subsection identifies requirements that a re specifically needed to fulfill

safety functions. Such functional requirements are specified for both the SAC

and any needed support SSCs.

Limit functional requirement designation to those requirements necessary for

the SAC safety function. Functional requirements are provided for SACs for

the specific accident(s) or general rationales for which the SAC is needed.

For SACs, functional requirements may involve unimpeded access to specific

rooms or areas, use of certain instrumentation, written procedures or checklists,

and special tooling. The description of the functional requirement must fully

address all aspects important for ensuring the SAC can be accomplished.

4.5.X.4

SAC Evaluation

This subsection provides performance criteria imposed on the SAC so it can

meet functional requirements(s) and thereby satisfy its safety function.

Performance criteria characterize the specific operational responses and

capabilities necessary to meet functional requirements.

The formulation of SACs should include a pro cess that validates that plant

operators can perform the task(s) called for in a SAC within the timeframes

assumed in the safety basis. 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 and alarms

Time available to do the task or recover from 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 action to detect and

isolate a leak, flow rate calculations will need to be performed to substantiate

the available time interval necessary to accomplish the task. Consequences of

incorrect implementation of the control should be evaluated and measures to

prevent control failure should be factored into the control formulation.

Page 63