Mission-Critical Functions

DOE-STD-1036-93

4.1.3

Mission-Critical Functions

Independent verification is more than just an adjunct to the facility safety

or environmental control programs; it is a tool that can be used to

enhance the reliability of facility operations. Applying independent

verification to production-related systems and components helps reduce

unscheduled shutdowns and other unplanned reductions in the facility

output. Systems, structures, and components that are critical to the

performance of the facility's mission should be considered for

independent verification.

In addition to the systems, structures, and components that fill nuclear

safety, ES&H, and mission critical functions, independent verification

should also be considered for systems or components that could

challenge a safety system or mission critical system. For example, testing

or changing the alignment of certain components in a non-safety,

non-critical system may cause spurious actuation of a safety system or a

transient upset in a mission-critical system.

4.1.4

Components Excluded from Independent Verification Requirements

In some systems where independent verification is required, specific

components may be excluded from the requirement if certain conditions

are met. Independent verification may not be required for a particular

component if:

C Mispositioning the component would not affect system performance

(i.e., the system could perform its intended function even if the

particular component were mispositioned). For example, a cooling

system may be able to perform its intended function even though an

air vent or water drain valve in a heat exchanger is not properly