location of piping class breaks
location of isolation valves
location of seismic class breaks
location of test features
Some supporting features may be outside the system boundary, such as electrical power,
instrument air, lubricating oil, and ventilation. In addition, some complete systems may
cross multiple facility and activity boundaries, such as ventilation systems.
Identifying and Documenting Design Requirements
Once the set of CM SSCs is identified, the contractor must identify and document the
design requirements for this set of SSCs. The contractor must assess the effects of
changes to the design requirements of CM SSCs through the configuration management
process. Furthermore, the contractor must maintain the design requirements for CM
SSCs throughout the life of the nuclear activity.
The documentation should identify which of the design requirements are required for
safety and which are necessary for cost, environmental, or other considerations, so the
impacts of changes can be better assessed.
The design requirements to be documented include those that affect:
3.3.1 Design Process
Figure 3-4 illustrates the process of identifying design requirements for CM SSCs. The
design process has three elements:
Design Inputs consist of those specific criteria, limits, bases, or other initial
requirements (such as specific functional requirements, specific codes and
standards, and specific regulatory commitments) upon which the detailed final
design is based. In comparison to design constraints, design inputs are specific in
nature; i.e., they are specific to one design activity. For example, a design input
for a given air-operated valve might be that it needs to open in ten seconds against
a differential pressure of 100 psig. Design inputs should consider the effects of
the operating environment (e.g., radiation, temperature, pressure, humidity,
chemical spray), material condition, and aging (e.g., erosion, corrosion, fatigue,
chloride stress or intergranular stress corrosion cracking, and embrittlement).
For example, the design requirements should consider the effects of radiation