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Page Title: Regeneration of Design Requirements
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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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