Document: NUREG-0800
Document ID: 2cb61281-91f4-400a-8eda-41e187e51d77
Document Type: srp
Title: AUXILIARY FEEDWATER SYSTEM (PWR)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070570007.pdf
Revision Date: 2023-06
Chapter: 10
Section ID: 10.4.9
CFR Part: 
CFR Title: 

Content:
uring emergency or accident conditions involving a loss of normal feedwater. In the event of an DBF or internal flooding, systems not designed to withstand these effects may be severely damaged. GDC 2 provides assurance that the AFWS will perform its safety function in the event of a DBF. 4. GDC 4 requires the protection of SSCs important to safety from external missiles, internally-generated missiles, and the dynamic effects of pipe breaks. The AFWS safety function is to remove decay heat from the reactor coolant system following a loss of normal feedwater, by providing an emergency source of feedwater to the steam generators. Normal feedwater may be lost as a result of numerous anticipated operational occurrences and design basis accidents that may involve missile generation or piping failures. External missiles may be generated by natural phenomena, such as tornados, or may result from onsite or nearby industrial accidents. The failure of systems with high internal or kinetic energies can generate internal missiles as a result of component failure and fragmentation. In addition to missiles, failure of high-energy piping systems, and to a lesser extent moderate-energy systems, can result in pipe whip, jet impingement, flooding, and other environmental conditions that can effect the operability of safety-related systems like AFWS. GDC 4 provides assurance of AFWS protection from anticipated environmental conditions and events so it can support removal of reactor decay heat. 10.4.9-9 Revision 3 - March 2007 5. GDC 5 prohibits the sharing of SSCs important to safety among nuclear power units unless such sharing can be demonstrated not to significantly impair their ability to perform safety functions including in the event of an accident in one unit, an orderly shutdown and cool-down of the remaining units. The AFWS safety function is emergency heat removal from and the shutdown and cool-down of the reactor coolant system to low-pressure residual heat removal system