Document: NUREG-0800
Document ID: bc7e4c14-0eaa-4591-a506-23d7893f8a00
Document Type: srp
Title: as establishing acceptable guidance for meeting the requirements of this criterion.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070498.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
to that supplying non-Class 1E loads, are not the most reliable configurations. Such configurations make it difficult to obtain suitable voltage regulation at the Class 1E buses and subject the Class 1E loads to transients caused by non-Class 1E loads (e.g., Reactor Coolant Pump). Such configurations also result in additional failure points between the offsite power source and the Class 1E buses/loads. Therefore, for new applications, the staff has concluded that the design should include at least DRAFT Rev. 3 - April 1996 8.3.1-18 one offsite circuit be supplied directly to each redundant safety division from one of the offsite power sources with no intervening nonsafety buses in such a manner that the offsite source can power the safety buses in the event of failure of any nonsafety bus. In plants where there is no alternate source to supply power to balance of plant loads such as Reactor Coolant Pumps, Reactor Recirculation Pumps, Feedwater Pumps, etc.; the loss of power to these loads due to a plant trip or a 100% load rejection caused by the opening of the main generator high-side circuit breaker will result in a loss of forced circulation in the reactor coolant system and reduced feedwater flow. Therefore, for new applications, the electrical drawings should also be examined to ensure that the design includes an alternate power source for nonsafety loads, unless it has been demonstrated that the design margins will result in transients for loss-of- nonsafety-power events that are no more severe that those associated with the turbine-trip-only event in existing plant designs.96 In assessing the adequacy of the electrical ties between the onsite and offsite power systems, and the capability of the preferred power circuits to deliver power to the safety-related buses, both primary and secondary backup protective relaying schemes and their coordination, relay settings, and assigned control power supplies are reviewed by PSBEELB to assureensure that, in the event