Document: NUREG-0800
Document ID: 96afb1d6-6ce9-41e4-b4ec-1fc7747bc0b2
Document Type: srp
Title: Revision 8 – January 2021
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML2033/ML20339A647.pdf
Revision Date: 2023-05
Chapter: 7
Section ID: 7
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on would occur only under certain plant conditions. Such a spurious operation is still self-announcing (by the actuated system), even if failure did not occur on initial test or BTP 7-19-18 Revision 8 – January 2021 startup. Because of the potential consequences of a spurious operation, a system’s failure to actuate might not be the most limiting failure. This is especially true in view of the time needed to identify and respond to conditions resulting from spurious operation in DI&C systems. In some cases, a failure to trip might be less limiting than a partial actuation. For example, a partial actuation of an emergency core cooling system (i.e., spurious operation of a single division), together with a false indication of a successful actuation, may take an operator longer to evaluate and correct than a total failure to send any actuation signal would. Therefore, the reviewer should consider the possibilities of both partial actuation and total failure to actuate, together with false indications, stemming from a CCF. Sources of Spurious Operation Spurious operations originating from CCFs due to latent design defects are considered beyond-design-basis events and are within the scope of this BTP.11 As stated in the background section of this BTP, CCFs should be evaluated in a manner consistent with SRM-SECY-93-087. Therefore, the reviewer may apply the methodologies described in this BTP when evaluating spurious operations resulting from CCFs. Spurious Operation and Integrated Systems12 As stated in the background section of this BTP, the integration of design functions in a DI&C system makes it challenging to identify CCF vulnerabilities and evaluate their potential consequences. System integration and interconnectivities, including shared resources, may reduce a plant’s overall defense in depth (e.g., by reducing independence). When evaluating integrated systems, the reviewer should focus primarily on NSR SSCs that are integrated with safety-related SSCs.