Document: NUREG-0800
Document ID: 9fa7092c-7628-402d-9028-6601d5f5fdfb
Document Type: srp
Title: DC POWER SYSTEMS (ONSITE)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550063.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.2
CFR Part: 
CFR Title: 

Content:
ems that must be supplied by the onsite ac and dc power systems. In addition, these criteria state that safety-related system redundancy shall be such that, for onsite power system operation (assuming offsite power is not available), the system safety function can be accomplished, assuming a single failure. The acceptability of the onsite dc power system with regard to redundancy is based on conformance to the same degree of redundancy as that needed for safety-related components and systems required by these criteria. As endorsed by Regulatory Guide 1.153, IEEE Std. 603 provides a method acceptable to the staff to evaluate all aspects of the electrical portions of safety-related systems and the onsite power system, including criteria addressing redundancy. Compliance with IEEE Std. 603-1991 is only required for plants with construction permits issued after May 13, 1999. Operating nuclear power plants are encouraged, but not required, to comply with IEEE Std. 603 for future system-level modifications. The staff will review the descriptive information—including electrical single-line diagrams, functional P&IDs, and electrical control and schematics—to verify that the dc power system reflects this redundancy, both in power sources and in associated distribution systems. The reviewer will also coordinate with other branches to verify that (a) redundant safety-related loads are distributed between redundant distribution systems and (b) the instrumentation and control devices for the safety-related loads and power system are supplied from the related redundant distribution systems. The review verifies that reactor core cooling is maintained after the loss of any one dc power supply or bus and a single independent active failure in any other system required for shutdown cooling. 2. Conformance with the Single-Failure Criterion. As required by GDC 17, the dc power system must be capable of performing its safety function, assuming a single failure. In evaluating the