Document: NUREG-0800
Document ID: 97120913-d26f-4324-ab62-22f3f5b73925
Document Type: srp
Title: and 8.3.2.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0636/ML063600410.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
any of the remaining supplies as a result of, or coincident with, the loss of power generated by the nuclear power unit, the loss of power from the transmission network, or the loss of power from the onsite electric power supplies. The trip of the nuclear power unit is an anticipated operational occurrence that can result in reduced switchyard voltage, potentially actuating the plant’s degraded voltage protection and separating the plant’s safety buses from offsite power. It can also result in grid instability, potential grid collapse, inadequate switchyard voltages, and a subsequent LOOP due to loss of the real and/or reactive power support supplied to the grid from the nuclear unit. Plant technical specifications (TS) LCOs require the offsite power system to be operable. However, since the capability of the offsite power system cannot be tested except when challenged during an actual event, the design bases for the offsite power system can only be assured through analysis of the grid and plant conditions. Plant operators should therefore be aware of: (1) the capability of the offsite power system to supply power, as required by TS, during operation and (2) situations that can result in a LOOP following a trip of the plant. Plant operators are expected to declare the offsite power system inoperable in the event of degraded grid conditions that can not support adequate post-trip voltages. Additional information on the adequacy of grid voltage, grid stability and grid reliability challenges due to deregulation of the utility industry, and the effect of grid events on NPP performance are provided in References 21, 24, 25, 29, 30, and 43. 8.2-11 Revision 4 - March 2007 GDC 17 also requires that the onsite power supplies and the onsite electrical distribution system have sufficient independence, redundancy, and testability to perform their safety functions assuming a single failure. Therefore, no single failure will prevent the onsite power system from supplying