Document: NUREG-0800
Document ID: 5e40cf60-028d-44c3-b9b8-735a6a68a48a
Document Type: srp
Title: Revision 6 - August 2016
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1602/ML16020A036.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
uires in part high functional reliability of safety systems. Timely operation is necessary for high functional reliability of safety systems. GDC 23, “Protection System Failure Modes,” requires in part the protection system to be designed so that if it fails, it fails into a safe state given the anticipated failure modes and conditions in which the failure occurs. This is a design architectural issue aimed at staying within timing limits. GDC 25, “Protection System Requirements for 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. 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. GDC 29, “Protection against Anticipated Operational Occurrences,” requires in part defense against anticipated operational transients to assure an extremely high probability of accomplishing safety functions. To assure this, the protection system must be demonstrated to operate within the time constraints of each anticipated operational transient. 2. Relevant Guidance IEEE Std 603-1991 is a system-level standard that contains 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: • Clause 4.4 - limits, ranges, and rates of change of variables should be included in the documented design basis. • Clause 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. • Clause 6.1 - timely automatic control action is required