Assignment of SSC Grades

DOESTD107393

2.2.2 ASSIGNMENT OF SSC GRADES

The grading of SSCs can be performed efficiently by separating system and component grading. The

systems are graded first the components to systems and graded next. This approach to grading calls

for increasing levels of design requirements knowledge as the grading proceeds to the component level.

For example, it might be obvious that a given system is related to safety, but less obvious that a given

component within that system has a safety function.

2.2.2.1 System-Level Grading

Facility structures may be categorized as either systems or components, whichever makes the most

sense for the facility. The facility may choose to address structures collectively as a single overall

system and address individual structures as components. Alternatively, individual structures may be

associated with the systems they house and support. Similarly, computers and software important to

facility operation should be evaluated as either systems or components, as appropriate.

A flowchart showing the basic steps for system-level grading is presented as Figure 27. The initial step

of system grading is to identify the facility systems. System designations already exist at most facilities.

If such designations do not exist, the components that accomplish the same basic facility functions and

processes should be grouped into systems.

The second step is to identify the types of design requirements that apply to each system according to

the best information on the design requirements available. (The specific criteria for each requirement

type will have been established during program planning.) For the Initial system grading, experienced

personnel with key design documents on hand are capable of applying their design knowledge to make

this determination quickly and accurately. Such summary design references include the facility SAR, the

TSR, SDDs, fire protection analyses, criticality evaluations, and any other readily available general and

summary design documents deemed appropriate by experienced personnel. Later, as design

requirements are formally reconstituted, the Best Available Design Information might indicate a need to

refine these determinations.

The next step is to assign a system grade according to the types of design requirements that apply to

each system. The grade is based on the most important category of design requirements that applies.

For example, if a system has safety design requirements, it is a safety system. If it has mission design

requirements and neither safety nor environmental requirements, it is a mission system. For example, a

facility life-limiting component, as identified by the material condition and aging (MCA) adjunct program,

would be graded as mission if no higher grade applied.

2.2.2.2 SSC Inclusion In Configuration Management Program

Finally, the facility CM program equipment scope criteria are applied to determine which systems will be

included in the CM program. (These criteria should have been established by the program

management element equipment scope criteria function and documented in policy directives and the

CM program plan.) For example, the equipment scope criteria may be such that only safety,

environmental, and mission SSCs are within scope, in which case the optional systems are out of scope

and no further action is necessary for these systems. A facility may elect to include none, some, or all of

the optional systems. As another example, if only the safety SSCs were within the scope, the other

systems would not be included in the CM program.

New information relevant to system grading will be identified periodically in ongoing CM program

development and implementation as well as normal design and operations activities. This includes the

preparation of new designs. For example, the facility might add a new system that needs grading.

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