In-service Inspection Requirements. Discussion of in-service inspection (ISI) and in-service
testing (IST) as specified by Section XI of the ASME Code. These requirements should be
summarized and the procedures that implement the specific ISI and IST requirements should
be listed or referenced.
Testing and Testability Requirements. Describe testing requirements established by design
engineering. Describe unique system testing requirements that resulted in special system
Material Condition and Aging Management. Describe additional testing or operational
measures specified by the MCA program. May include both those measures specified for life
extension and other measures for general aging management.
In addition to sections described above, the following provides information that may be useful in
understanding existing configuration and evaluating proposed changes. The users and uses of the
facility DISs may influence the selection and content of these sections. These sections are optional.
Change History. Description of the design change history. The change history section is
either a narrative or a listing of changes to the system since facility startup with an
explanation of the need for each change. This information serves several purposes: (1)
provides a ready source of rationale for past changes to systems, structure, and
components; (2) aids the review process to ensure design basis and requirements are
updated and design continuity is maintained; and (3) assists the process of root cause
determination of operational problems.
Design Margin. Design margin is the conservatism between the specified design requirement
and the minimum requirement that could be developed from the design basis. This section
could be presented as a table that shows the specified design requirement compared to the
possible design requirement if margin was removed. It could be invaluable when evaluating
operability concerns. In addition, this section could be a key input to the preparation of USQ
safety reviews, since this information addresses the impact of changes on the margin of safety.
However, this can be a difficult section to develop in that system sensitivity analyses, which
would enable identifying component margins, may not have been performed. It is important
not to identify margin that was added for calculational uncertainty as usable design margin.
Identifying and documenting margins when specific design basis information is being
developed, or as subsequent analyses are performed, could be a valuable reference.
Summary of Critical Calculations. Summaries of the most important system calculations could
be provided along with basic assumptions, calculational methods, relationship to other
calculations, and general conclusions of calculations.
Postulated Failures. Description of failure modes considered in the system design. It could
include passive failures, such as pipe breaks, and active failures, such as failure of a valve to
close or pump to start on demand. A discussion of the impacts of a postulated support
system failure, (such as a valve repositioning on a loss of instrument air) could also be
included. Facility events may lead to special tests or analyses that can be used as inputs to
Response to Transients. The specific response of the system could be described for facility
transients and accidents.