Document: NUREG-0800
Document ID: 2dffe24e-cd37-4ffc-9c37-16faf25676b1
Document Type: srp
Title: Appendix 7-A
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500579.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
r Reactivity Control Malfunctions," requires, in part, reactivity control to prevent fuel design limits from being exceeded. This requires timely operation of the protection features of the reactivity control system. 10 CFR 50 Appendix A, GDC 28, "Reactivity Limits," requires in part a limited reactivity rate-of-change to prevent (1) fuel limits from being exceeded and (2) a non-coolable core geometry. The protection system must meet the timing requirements imposed by this criterion. 10 CFR 50 Appendix A, GDC 29, "Protection Against Anticipated Operational Occurrences," requires in part defense against anticipated operational transients to ensure an extremely high probability of accomplishing safety functions. To ensure this, the protection system must be demonstrated to operate within the time constraints of each anticipated operational transient. 2. Relevant Guidance Reg. Guide 1.153, "Criteria for Power, Instrumentation, and Control Portions of Safety Systems," endorses IEEE Std 603, "IEEE Standard Criteria for Safety Systems for Nuclear Power Generating Stations," which is a system-level standard that contains some requirements related to performance and timing. This standard requires in part that a reactor safety system have a documented design basis consisting of the following: • Section 4.4 — limits, ranges, and rates of change of variables should be included in the documented design basis. • Section 4.5 — minimum times should be specified for manual actions, below which such actions cannot be considered to be accomplished. • Section 4.10 — critical points in time should be specified for: – Initiation of protective action. – Completion of protective action. – Time when automatic control of protective action is required. – Time when protective system may be returned to normal. In addition, timely automatic control action is required when events occur too quickly for operator intervention. Reg. Guide 1.152, "Criteria for Power,