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:
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 core is cooled during accidents. 5. Compliance with GDC 27 establishes requirements regarding the combined reactivity control system capability. GDC 27 is applicable because upon actuation the ECCS in PWRs provides rapid injection of borated water to ensure reactor shutdown and adequate core cooling with appropriate margins for stuck control rods. Injection of borated water provides negative reactivity to reduce reactor power to residual levels and ensures sufficient cooling flow to the core. Meeting the requirements of GDC 27 for the ECCS augments the protection for the primary fission product barrier by providing a means to ensure that the core, under postulated accident conditions, can be safely shutdown and will be maintained in a coolable geometry. 6. Compliance with GDC 35 requires that an emergency core cooling system be provided that is capable of transferring heat from the reactor core, following a loss of reactor coolant, at a rate sufficient to ensure that the core remains in a coolable geometry and that the clad metal-water reaction is limited to negligible amounts. GDC 35 is applicable because following a breach in the reactor coolant pressure boundary, reactor coolant is lost at a rate determined by several factors, including break size and RCS pressure. The emergency core cooling systems are relied upon to inject adequate cooling water into the RCS during a LOCA and to circulate the water through the core to provide for core cooling. The ECCS systems must inject cooling water at a rate sufficient to ensure that the calculated changes in core geometry will be such that the core remains amenable to cooling, and that the calculated cladding oxidation and hydrogen generation meet the specified performance criteria. Meeting the requirements of GDC 35 ensures