Document: NUREG-0800
Document ID: 2925ed14-c49b-459b-8786-e6bffd2c43c4
Document Type: srp
Title: AUXILIARY FEEDWATER SYSTEM (PWR)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070603.pdf
Revision Date: 2023-06
Chapter: 10
Section ID: 10.4.9
CFR Part: 
CFR Title: 

Content:
important to safety shall be designed to withstand the effects of earthquakes. Regulatory Guide 1.29 position C.1 identifies those structures, systems and components that should be designed as seismic Category I and that should remain functional following a Safe Shutdown Earthquake (SSE). Regulatory Guide 1.29 position C.2 provides criteria for those systems whose continued function is not required following a SSE, but whose failure could affect the functioning of those systems important to safety. The AFWS provides for heat removal from the reactor coolant system via the steam generators. The system performs this function during startup and shutdown under normal operations, and during emergency or accident conditions involving a loss of normal feedwater. In the event of an SSE, severe damage may occur to those systems not designed as seismic Category I, such as the main feedwater system. Compliance with GDC 2 provides assurance that the AFWS will perform its safety function in the event of a SSE. 2. GDC 4 requires the protection of SSCs important to safety from external missiles, internally generated missiles, and the dynamic effects of pipe breaks. The safety function of the AFWS 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. These accidents 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 lessor extent moderate energy systems, can result in pipe whip, jet impingement, flooding, and