Document: NRC Regulatory Guide
Document ID: d940ffea-1d07-4cc8-b0f2-64d5495912d7
Document Type: regulatory_guide
Title: Criteria for Power Systems for Nuclear Power Plants + HISTORY - HISTORY DG-1420 , Proposed Revision 4, published 08/2024 DG-1079 , Proposed Revision 3, published 04/2003 (Rev. 4)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2415/ML24158A060.pdf
Revision Date: 2024-08
Chapter: 
Section ID: RG-1.32
CFR Part: 
CFR Title: 

Content:
20 criteria for sharing safety-related dc power systems in multi- unit or multi-module nuclear power plants. 3. With the withdrawal of RG 1.41, its provisions for preoperational testing of load groups and proper redundant source independence are herein consolidated with the following supplement to Section 6.3, “Preoperational system test,” of IEEE Std. 308-2020: As part of the initial preoperational testing program and after major modifications or repairs to a nuclear facility, those onsite electric power systems designed in accordance with RG 1.6 (Safety Guide 6) and RG 1.32 should be tested as follows to verify the existence of independence among redundant onsite power sources and their load groups. I. The plant electric power distribution system, not necessarily including the switchyard and the startup and auxiliary transformers, should be isolated from the offsite transmission network. Preferably, this isolation should be initiated by direct actuation of the undervoltage-sensing relays within the onsite system. II. Under the conditions of I above, the onsite electric power system should be functionally tested successively in the various possible combinations of power sources and load groups with all DC and onsite AC power sources for one load group at a time completely disconnected. Each test should include injection of simulated accident signals, startup of the onsite power source(s) and load group(s) under test, sequencing of loads, and the functional performance of the loads. Each test should be of sufficient duration to achieve stable operating conditions and thus permit the onset and detection of adverse conditions that could result from improper assignment of loads (e.g., the lack of forced cooling of a vital device). III. During each test, the DC and onsite AC buses and related loads not under test should be monitored to verify absence of voltage at these buses and loads. DG-1420, Page 8 D. IMPLEMENTATION The NRC staff may use this regulatory guide as