Document: NUREG-0800
Document ID: 757b676a-0f71-4094-8677-ca3a50743281
Document Type: srp
Title: Revision 7 – August 2016
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1601/ML16019A344.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
Manual Action as a Diverse Means of Accomplishing Safety Functions If manual operator actions are used as the diverse means or as part of the diverse means to accomplish a safety function, a suitable HFE analysis should be performed by the applicant to demonstrate that plant conditions can be maintained within recommended acceptance criteria for the particular AOO or postulated accident. The acceptability of such actions is to be reviewed by the NRC staff in accordance with Appendix 18-A of SRP Chapter 18, “Crediting Manual Operator Actions in Diversity and Defense-in-Depth (D3) Analyses.” Note: As the difference between Time Available and Time Required for operator action is a measure of the safety margin and as it decreases, uncertainty in the estimate of the difference between these times should be appropriately considered. This uncertainty could reduce the level of assurance and potentially invalidate a conclusion that operators can perform the action reliably within the time available. For complex situations and for actions with limited margin, such as less than 30 minutes between time available and time required, a more focused staff review will be performed. Diverse manual initiation of safety functions should be performed on a system level or division level basis (depending on the design). Since single failures concurrent with a CCF are not BTP 7-19-17 Revision 7 – August 2016 required to be postulated and normal alignment of equipment is assumed, the capability for manual actuation of a single division is sufficient. For plants licensed to allow one division to be continuously out of service, the diverse manual actuation should apply to at least one division that is in service (see section B.3.1, Item 9, concerning addressing spurious actuation caused by the diverse means in the design of the diverse means). A CCF that affects normal displays or controls should not prevent the operator from manually initiating safety functions. Prioritization between