Definition:
Design Bases Specifications are statements that define how your facility will comply with a specific Design Requirement.
Design Bases Specifications are facility-specific. They restate Design Requirements into statements that specify what your unique facility will do to comply with a specific requirement. They are as made as specific as possible and still address how the requirement is met by the facility as whole, not by the system, component or structure.
Example 1:
At the West Bend Nuclear Plant, residual heat will be removed under normal conditions by using the High Pressure Core Spray System when vessel pressure is above 700 psig, Low Pressure Core Spray when system pressure is 700 psig or below, and transferred through the Residual Heat Removal System to the Essential Service Water System and ultimately through the cooling towers to atmosphere.
Example 2:
At the West Bend Nuclear Plant, the Auxiliary Feedwater System is used to remove residual heat from the reactor core in conjunction with the Reactor Coolant System and the Main Steam System when the Main Feedwater System is unavailable.
Example 3:
At the West Bend Nuclear Plant, the AFW system will be designed with sufficient redundancy of components so that under accident conditions the safety function can be performed assuming a single active component failure. (This may be coincident with the loss of offsite power for certain events.) Branch Technical Position ASB 10-1 46 as it relates to AFW pump drive and power supply diversity shall be used in meeting these criteria.
Example 4:
At the West Bend Nuclear Plant, the AFW system will be designed to include the capability to isolate components, subsystems, or piping if required so that the system safety function will be maintained.
Example 5:
At the West Bend Nuclear Plant, the AFW system will include design provisions to permit appropriate functional testing of the AFW components to assure operability and performance of active components during normal, shutdown, and accident conditions.
Note that general requirements can often produce very complex and convoluted DBSs necessary to specify the range of plant systems and configurations necessary to comply with the requirement. In the past, these complex conditional statements would be found in the Final Safety Analysis Report (FSAR) or similar document, but in the new CM taxonomy, these descriptions are placed to provide direct design guidance.
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