Application of the Graded Approach to the Development of SDDs

DOE-STD-3024-98

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Application of the Graded Approach

to the Development of SDDs

The graded approach provides substantial flexibility for the development of SDDs that can be meshed with

the priorities and resources available to the facility. This appendix addresses the systems for which SDDs

may be appropriate, and the application of the graded approach to SDDs including the phased approach to

such developments.

FACILITY CATEGORIZATION

The graded approach should be applied based on a number of considerations, including the hazard

categorization of the facility (in accordance with DOE-STD-1027) and the categorization of the system.

Appropriately graded levels of effort could then be established, each of which would provide system

requirements and system description information. At a Hazard Category 1 nuclear facility, it might be

decided, for example, that a Facility Design Description (FDD) will be developed and SDDs will be

developed for all safety and mission critical systems. At a Hazard Category 2 nuclear facility, it might be

decided, for example, that SDDs will be developed only for safety SSCs. At a Hazard Category 3 nuclear

facility, it might be decided, for example, that separate SDDs would not be developed, but instead an FDD

would be developed which describes the facility from an overall perspective and summarizes all the SSCs.

Such an FDD would most likely emphasize the system requirements and system descriptions for each System.

FACILITY REMAINING LIFETIME

The useful life of the completed SDD should be long enough to make it worth the resources expended to

develop the SDD. If the remaining operational lifetime of the facility is only a couple years, it might be

concluded that the development of SDDs is not worthwhile.

SSC CLASSIFICATION

The systems within the facility should be classified in accordance with DOE-STD-3009. The system

importance classification should be used to determine which systems need to have SDDs developed. All

safety SSCs should have SDDs developed (Safety SSCs include both Safety-Class SSCs and Safety-

Significant SSCs). Serious consideration should also be given to developing SDDs for environmental-

protection and mission-critical Systems.

GRADING WITHIN AN SDD

When the decision has been made to develop an SDD for a particular system, the graded approach determines

the level of effort to be applied during development.

The factor that will have the greatest effect on the level of effort involved in developing an SDD is the

complexity of the system involved. Simple systems might yield an SDD of only a few pages. Complex

systems might necessitate many pages to describe its requirements, bases, and operational aspects.

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