Does the failure cause a power reduction greater than 10 percent or result in a
The amount of power reduction or other operational impact should
be established by plant management.
This question divides the nonsafety-related failures into two groups, operational and
Yes - Those failures that directly impact operations and power generation. These
failures affect the ability of an operations-critical system to perform its primary
Those failures that impact support functions or result in a power reduction less
than 10 percent, or those failures with a purely economic impact.
Does the failure cause a plant scram?
This question divides failures that impact operations into two groups, scram initiator
and operational impact:
Yes - Those failures that result in a plant scram.
Those failures that result in a forced outage, a power reduction less than 10
percent, or other operational impact.
8.1.1 Using the LTA, categorize each failure mode according to its consequence
and importance to the operation of the plant. The importance classes are
Class A (Safety) - Failure modes that affect personnel and/or reactor safety.
Scheduled maintenance is required and shall reduce the likelihood and severity
of the failure to an acceptable level; otherwise, the component/system should
Class B (Scram initiators) - Failure modes that may cause plant scrams.
Scheduled maintenance or a design modification is required to reduce
operational costs and limit challenges to safety systems.
Class B2 (Operational Impact) - Failure modes that result in a forced outage,
power reductions less than 10 percent power, or other operational impact.
Scheduled maintenance or a design modification is necessary to reduce
operational and corrective maintenance cost.
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