Multi-Tiered Design Process

DOESTD107393

Multi-Tiered Design Process. The design process produces both design requirements and the

associated design basis. Changes to design requirements need to be supported by the design basis.

The design process identifies, documents, categorizes, and sorts by SSC every new facility design

requirement, as well as changes or modifications to existing design requirements. The design process

also identifies and documents the design basis of every new facility design requirement, in addition to

changes or modifications to existing design requirements.

The design process is called upon whenever a change to the facility design requirement is

contemplated. Permanent and temporary facility physical changes need engineering design if they

involve potential changes to design requirements. Changes to final designs, field changes, facility

physical changes, and nonconforming items dispositioned use-as-is or repair should be evaluated, and

subject to design control measures commensurate with the original design. Requests for, engineering

design may be initiated from within the design organization, and also from non-design organizations,

such as operations, maintenance, and technical support.

Design controls may vary based on the complexity and significance of the design change. For

example, some commercial nuclear facilities employ a three-tiered design process. Once the design

process is initiated, a scope assessment is conducted to determine which tier the design change will

take. This assessment reviews the technical complexity, the magnitude of the change, and the

potential impact on previous commitments, including the authorization basis. Based on the scope

assessment, the engineering management decides which of the three tiers the design task will pursue.

These three tiers might be designated: Field Change Notices (for simple drawing changes to reflect as-

built conditions); Minor Modification Packages (for minor facility changes such as component re-

designs, with minor systems impact or systems interaction, and minor safety significance); and Design

Change Packages (for other facility changes). Within DOE, an important distinction is between those

changes managed as projects under DOE 4700.1, and those not managed as projects. The facility

may also establish separate design control provisions to accommodate those changes to documents

only, without any associated physical changes.

The specific design control measures to ensure that the design process is correctly implemented may

vary depending on which tier is appropriate for a design change. However, regardless of the level of

design control applied, the design process needs to produce both new/revised design requirements and

associated design basis. The design process is the same at the different levels. Without proper

controls, designs performed on the lower tiers often do not produce the necessary design basis and

design outputs. The design authority needs to carefully control and monitor each design tier to ensure

the design inputs, design constraints, design analysis and calculations, and design requirements are

identified, accurate, complete, and documented.

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