Regeneration of Design Requirements

DOESTD107393

Second priority should be given to those design requirements necessary for facility operations, such as

set point data.

Two options exist for prioritization of remaining regeneration activities: (1) prioritize by requirement type-

safety requirements, followed by environmental requirements, and so on; or (2) prioritize by grade

(importance) of the SSCs involved. If option 2 is indicated, missing design requirements of every type

would be regenerated first for the most important SSCs (i.e., safety and then environmental SSCs).

Other possible bases for prioritization include modification history, future plans for modification, and

design pedigree.

Several methods have proven successful for reestablishing missing design requirements:

Performing reanalysis. This approach is basically equivalent to redesign; it applies the design

process to determine design requirements. Although the most technically acceptable method

for regenerating missing requirements, it is typically the most expensive. This approach

should be used for the most important missing design requirements.

Gathering and documenting information from the experience of knowledgeable engineering

and operations personnel. Their memory is a valuable (and frequently undocumented)

source of information, and that information could be lost through attrition, transfers, retirement

and death. This activity should start promptly to prevent any further loss of knowledge.

Reenacting the original design process to decide which design outputs or portions of the

equipment specifications are essential and which are optional. A combination of the first two

approaches, this method may not go as far as reanalysis, but does carefully consider the

likely design inputs, constraints, analysis and calculations, and outputs. After reanalysis, this

is the most technically acceptable method.

Testing equipment to determine its current functionality and accepting the results as design

requirements after a technical evaluation by the engineering organization. Testing might be

the only practical method for showing that system performance remains adequate.

Reenacting the original design process calls for envisioning that original process. Hypothetically, after

having established the fundamentals of the system design, the designer could discuss options with

various component vendors. At the beginning of such a discussion, the designer might explain the

general application and the functional requirements for the system. Attention would focus on a

particular component, such as a valve, and the designer would explain what the valve needed to be able

to do. For example, during normal facility operation, the valve has to remain closed to provide

intersystem isolation with minimum leakage. During accident conditions, the valve has to stroke open

against a differential pressure as high as 500 psid and be fully open within 10 seconds. For failure

considerations, the valve has to fail in its as-is position. In response, the vendor might suggest a certain

valve for the application. Through an iterative process, the designer and vendor would arrive at the final

selection. Recreating this type of hypothetical discussion and capturing the pertinent points is part of

reenacting the original design process.

The selection of regeneration method is based on available information, the importance of the SSCs,

feasibility, and resources. A combination of methods is often a cost-effective approach.

Throughout design requirements regeneration, the design basis resulting from the regeneration efforts

should be documented. After regeneration, a management review should be conducted to approve the

completed set of requirements. As with the other stages, the regenerated design requirements feed to

the CM equipment database and might affect system and component grading. Design requirements

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