Document: NUREG-0800
Document ID: 853719df-a6ea-408b-8d43-5956155abc38
Document Type: srp
Title: and 8.3.2.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1007/ML100740246.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
n turbine-trip-only events in current plants, and 2) at least one offsite circuit to each redundant safety division supplied directly from offsite power sources, with no intervening non-safety-related buses. Passive reactor designs incorporate passive safety-related systems for core cooling and containment integrity, and therefore, do not depend on the electric power grid connection and grid stability for safe operation. However, passive reactor designs also include active systems that can provide defense-in-depth capabilities for reactor coolant makeup and decay heat removal. The accident analysis and Probabilistic Risk Analysis (PRA) need to be reviewed to identify these non-safety related systems. Once identified, review of the electrical design of the plant needs to confirm that any offsite power requirements for thses systems are met. The AP1000 safety analyses, for example, assume that the reactor coolant pumps (RCPs) can receive power at 6.9 kV from either the main generator or the grid for a minimum of 3 seconds following a turbine trip assuming no electrical fault. Should a turbine trip occur during power operation, the generator will continue rotating at synchronous speed by acting as a synchronous motor. Anti-motoring protective relaying for the main generator will open the generator output breaker after a time delay of at least 15 seconds, during which time the rotating generator will provide voltage support for the grid. When the generator output breaker trips, the plant distribution system utilizes backfeed from the grid to maintain power to the RCPs. Therefore, grid stability analyses should verify that the grid remains stable for a minimum of 3 seconds following a turbine trip to support the assumptions made in the safety analyses for the passive reactor designs, such as the AP1000. IEEE Std 308, as modified/supplemented by the regulatory positions of RG 1.32, establishes acceptable guidance for meeting the requirements of GDC 17. Meeting the