Document: NUREG-0800
Document ID: b351c30f-74b4-4d36-833e-939d23abae4e
Document Type: srp
Title: D-C POWER-SYSTEMS (ONSITE)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350494.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.2
CFR Part: 
CFR Title: 

Content:
fety- related loads are distributed between redundant distribution systems, and that the instrumentation and control devices for the safety-related loads and power system are supplied from the related redundant distribution systems. 2. Conformance with the Single Failure Criterion As required by GM( 17, the d-c power system must be capable of performing its safety function assuming a single failure. In evaluating the adequacy of this system to meet the single failure criterion, both electrical and physical separation of redundant power sources and distribution systems, including their connected loads, are reviewed to asses.s the independence between redundant portions of the system. To assure electrical independence, the design criteria, analyses, description, and implementation as depicted on functional logic diagrams, electrical single line diagrams, and electrical schematics are reviewed to determine that the design meets the requirements set forth in IEEE 8.3.2-6 Rev. 2 - July 1981 Std 308 and satisfies the positions of Regulatory Guide 1.6. Additional guidance in evaluating this aspect of the design is derived from IEEE Std 379, "Guide for the Application of the Single Failure Criterion to Nuclear Power Generating Station Protection Systems," as augmented by' Regulatory Guide 1.53. Other aspects of the design where special review attention is given to ascertain that the electrical independence and physical separation has not been compromised are as follows: a. The interconnections between redundant load centers through bus tie breakers and multi-feeder breakers used to connect extra redundant loads to either of the redundant distribution systems are examined' to assure that no single failure in the interconnections will cause the paralleling of the d-c power supplies. To assure this, the control circuits of the bus tie breakers or multi-feeder breakers must preclude automatic transferring of load centers or loads from the designated supply to the redundant