Document: NUREG-0800
Document ID: eb1d19c1-686c-42f5-ba0a-c417c7b12b8e
Document Type: srp
Title: DC POWER SYSTEMS (ONSITE)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070499.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.2
CFR Part: 
CFR Title: 

Content:
s. Following this, it is verified that the tabulation of all safety-related loads to be connected to each dc supply is consistent with the information obtained in coordination with other branches. The characteristics of each load (such as motor horsepower and volt-amp ratings, inrush current, starting volt-amps, and torque), the length of time each load is required, and the basis used to establish the power required for each safety-related load (such as motor name plate rating, pump run out condition, or estimated load under expected flow and pressure) are utilized to verify the calculations establishing the combined load demand to be connected to each dc supply during the "worst" operating conditions. In reviewing the design of the thermal overload protection for motors of motor operated safety-related valves, the reviewer is guided by Regulatory Guide 1.106. Where the proposed design provides for the sharing of dc supplies between units at the same site, and connection and disconnection of nonsafety-related loads to and from the safety-related distribution buses, particular attention is given in the review to assureensure that the implementation of such design provisions does not compromise the capacity, capability, or reliability of these supplies. Regulatory Guide 1.81, Position C.1 recommends that dc systems in multi-unit nuclear power plants should not be shared.95 In the absence of specific criteria in IEEE Std 308 governing the connection and 96 disconnection of nonsafety-related loads to and from the safety-related distribution buses, the review of the interconnections will consider isolation devices as defined in Regulatory Guide 1.75 and engineering judgment to determine the adequacy of the design. In assuringTo ensure that the interconnections between nonsafety-related loads and safety-related buses will not result in the degradation of the safety-related system, the isolation device through which dc power is supplied to the nonsafety-related load,