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:
es 21, 25, 29, 30, and 43 provide information for the reviewer regarding degraded transmission grid voltage and the effects of grid events on grid voltage at the plant switchyard. The applicant should include in the grid stability analysis the consideration of failure modes that could result in ac frequency variations exceeding the maximum rate of change determined in the accident analysis for loss of reactor coolant flow. Failure modes that could produce abnormal frequency events and the plant frequency protection schemes are reviewed. Abnormal frequency operating experience from the assessment of grid transient events (Reference 43) and industry standards (Reference 54) provide further information on abnormal frequency considerations at nuclear power plants. 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. 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 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. 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