Introduction to DOE-STD-3024-98

DOE-STD-3024-98

Introduction to DOE-STD-3024-98

This section provides background information concerning the purpose and functions of System Design

Descriptions (SDDs) and the use of this standard in preparing SDDs. This section has been formatted

differently from the main body of this standard, which starts on page 1 with the outline for an SDD.

Purpose of a System Design Description

An SDD identifies the requirements associated with structures, systems, and components (SSCs),

explains why those requirements exist (that is, provides the bases for the requirements), and describes

the features of the system design provided to meet those requirements. As part of a configuration

management change control process, the SDD helps ensure consistency among the engineering

requirements for systems, the actual installed physical configuration, and the associated documentation.

The SDD is a central coordinating link among the engineering design documents, the facility

authorization basis, and implementing procedures. An SDD does not originate requirements or basis

information, but rather collects that information into a convenient usable form. The SDD consolidates

information about a particular system into one document. This provides the advantage that a reader

does not have to wade through many different documents and pull out the pertinent parts or have to

decipher the details in vendor technical manuals and engineering documents.

During the design and construction of a new facility or new system, the SDD might serve as the vehicle

for collecting and conveying the system requirements and their bases (i.e. the technical baseline). The

SDD should contain requirements that are derived from programmatic needs as well as from the

associated safety analyses. Accordingly, the development of the SDD must be coordinated with the

engineering design process and with the safety analysis development. The SDD may be used for

controlling changes as the design evolves from a concept through the preliminary design to the final

design. Sometimes this is accomplished in conjunction with Facility Design Descriptions (FDDs). In

an FDD, all the systems in a facility can be addressed with their top-level functions and requirements,

and the FDD refers to SDDs for more detailed information. An FDD provides a mechanism for

addressing simple, less important systems such as a potable water system, without having to develop

separate SDDs. The SDD is updated periodically and hence becomes more complete and detailed as the

design and safety analysis processes mature. Toward the end of the design phase, the SDD may be

used as a source document for the development of the facility authorization basis. Safety information in

the SDDs is extracted and placed into the SAR. In this case, the authorization basis mirrors the safety

information in the SDD. Even though the SDD may precede the development of the SAR, and hence

may become a source document for the authorization basis, an SDD is not a part of the authorization

basis. DOE does not rely upon information found uniquely in the SDD to make decisions regarding the

safety of the facility.

For an existing facility or system, when the development and approval of the authorization basis have

preceded the development of SDDs, the safety portions of the SDDs must mirror the authorization basis

documents. Accordingly, the SDD is not an authorization basis document. Controlling equipment

changes depends on recognizing changes, knowing what the existing requirements are, and

understanding why those requirements exist. The modification might involve a change in how the

requirement will be met, or might involve modifying a requirement or establishing a new requirement.

Evaluating the acceptability of a change in requirements is difficult if the reasons behind the

requirements are not understood. The SDD can help meet this change control need. When a change to

the system is proposed, the SDD can be consulted to identify the pertinent requirements and the

referenced engineering source documents. The results of the change would be reflected back into the

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