Document: NUREG-0800
Document ID: 4a295d6b-937a-429e-8fe4-1470b992d859
Document Type: srp
Title: Rev. 0 – November 2009
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0929/ML092950353.pdf
Revision Date: 2023-06
Chapter: 18
Section ID: 18
CFR Part: 
CFR Title: 

Content:
and time required decreases, confidence in the analysis decreases. In an April 21, 2009, letter to then Chairman Dale E. Klein, the ACRS provided these observations with associated recommendations to revise the guidance in DI&C-ISG-05, Revision 1. On June 5, 2009, the staff issued DI&C-ISG-02, Revision 2. Consistent with the ACRS observations and recommendations regarding DI&C-ISG-05, the NRC staff revised DI&C-ISG-02 to note that “for actions with limited margin, such as less than 30 minutes between time available and time required for operators to perform the protective actions, a more focused staff review will be performed. Similarly, the NRC staff reviewed the ACRS recommendations relative to the guidance in DI&C-ISG-05, Section 3. Accordingly, this Appendix incorporates, with limited modifications, the guidance contained in Section 3 of DI&C-ISG-05, Revision 1. 18-A-3 Rev. 0 – November 2009 C. STAFF POSITION A diversity and defense-in-depth (D3) analysis should include the justification of any operator actions that are credited for response to an AOO/PA concurrent with software CCF as described in BTP 7-19. Manual operator actions for these scenarios should be based upon, and ultimately included within, the Emergency Operating Procedures (EOPs) and executed from the main control room (MCR). To credit operator actions, an acceptable method would be to demonstrate that the manual actions in response to a BTP 7-19 software CCF are both feasible and reliable, given the time available, and that the ability of operators to perform credited actions reliably will be maintained for as long as the manual actions are necessary to satisfy the D3 analysis. The time available for manual actions should be based upon the methods and criteria prescribed in BTP 7-19. The time required for operator action should be estimated and validated using the guidance of this Appendix. To demonstrate that the manual actions are both feasible and reliable, and that the ability to