Phased Approach

DOE-STD-3024-98

Another way in which the graded approach can be applied to the development of SDDs is the level of effort

that would be expended in retrieving, compiling, and assembling existing design information (that is,

requirements and bases information). See Attachment 2 to this standard.

The topics that need to be addressed in an SDD may be adjusted using the graded approach. The most

important systems would have SDDs that are the most comprehensive. Less important systems might not

warrant the cost of developing such comprehensive SDDs. For example, sections of the outline such as

"Operations" (Section 4.2) and "Testing and Maintenance" (Section 4.3) might be considered for omission.

Having determined which topics of the outline need to be addressed in an SDD for a particular system, the

next consideration is the level of detail to which a topic should addressed. For important systems, a

particular topic in the outline may warrant a page or more of discussion. For a less important system, that

same topic may warrant only one short paragraph or simply a reference to appropriate procedures. This is

particularly pertinent with regard to Section 4 of the SDD.

The graded approach must not be used to justify inaccuracies in SDDs. Bad information is worse than no

information. Care must be exercised to ensure that all statements, tables, drawings, and other information in

an SDD is accurate, regardless of the system classification and the graded approach.

PHASED APPROACH

In addition to the decisions regarding which systems warrant SDDs and the extent of the content of particular

SDDs, another important consideration is whether to schedule or divide the development of those SDDs into

time phases. For example, SDDs for safety-class systems might be developed during the first year, followed

by SDDs for safety-significant systems the second year. The remaining SDDs would be scheduled for

subsequent years.

The content of the SDDs might be scheduled for development in stages. For example, the most important

sections of the SDD (such as the System Requirements and Bases) would be developed for all SDDs during

the first phase and issued as Revision 0 of those SDDs. Then during the subsequent phase, those SDDs

would be revised (completed) by developing the remaining sections (such as the System Description) and

issuing them as Revision 1 of the SDDs.

Att 1-2