Document: NUREG-0800
Document ID: eb0ea00d-43e4-45d1-8a5e-4daa4263d2cf
Document Type: srp
Title: EMERGENCY CORE COOLING SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550068.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.3
CFR Part: 
CFR Title: 

Content:
the SSCs to perform their safety functions, including, in the event of an accident in one unit, and orderly shutdown and cooldown of the remaining units. GDC 5 is applicable because the ECCS provides an important safety function in its ability to provide emergency core cooling and shutdown capability following postulated accidents. The ECCS system must be designed such that the ability to perform this and other designated safety-related functions are not compromised for each unit regardless of equipment failures or other events that may occur in another unit. Meeting the requirements of GDC 5 provides assurance that unacceptable effects of equipment failures or other events occurring in one unit of a multi-unit site will not propagate to the unaffected unit(s). 4. Compliance with GDC 17 requires that an on-site and off-site electric power supply system be provided to permit functioning of SSCs important to safety. GDC 17 is applicable, as it relates to the ECCS systems, because it requires that each power supply system have sufficient capacity and capability to ensure that the core can be cooled in the event of an accident, and that the fuel design limits and the design conditions of the reactor coolant pressure boundary are not exceeded during anticipated operational occurrences (AOOs). The ECCS is dependent upon the availability of electrical power supplied from the Class IE emergency electrical busses. The power supplies for the ECCS must maintain voltages at electrical equipment within the design limits. With voltages below design limits, electric equipment may not have sufficient capacity or capability to reliably perform their intended safety function during a design basis event. Meeting the requirements of GDC 17 enhances plant safety by ensuring that the ECCS capacity and capabilities will be sufficient to ensure that the fuel design limits and 6.3-9 Revision 3 - March 2007 reactor coolant pressure boundary integrity are maintained during AOOs and that the