Regulatory Guide 1.41

Preoperational Testing of Redundant on Site Electric Power Systems to Verify Proper Load Group Assignments

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Issue date:	03/16/1973
From:	Office of Nuclear Regulatory Research
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3/16/73 U.S. ATOMIC ENERGY COMMISSION

REGULATORY GUI DE

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1. DIRECTORATE OF REGULATORY STANDARDS

REGULATORY GUIDE 1.41 PREOPERATIONAL TESTING OF REDUNDANT ON-SITE ELECTRIC POWER

SYSTEMS TO VERIFY PROPER LOAD GROUP ASSIGNMENTS

A. INTRODUCTION

in one load group from causing the loss of equipment in another load group." The independence among General Design Criterion 1, "Quality Standards aiAd redundant on-site power sources and their load groups Records," of Appendix A to 10 CFR Part 50, "Genei .al should be such that the successful operation of any Desigu' Criteria for Nuclear Power Plants," requires th at power source and its load group is in no way affected by structires, systems, and components important to safety the partial or complete failure of any other power source be tested to quality standards commensurate with t]he and its load group.

importance of the safety functions to be performe d.

Criterion Xl, "Test Control," of Appendix B to 10 CF'R Since the reliability of an on-site power system of Part 50, "Quality Assurance Criteria for Nuclear Pow er the kind discussed in this guide is predicated on the Plants and Fuel Reprocessing Plants," requires that a te.st existence of this independence, a suitable preoperational program be established to assure that all testing requiri-d test to detect any lack of independence should be to demonstrate that structures, systems, ajid performed. As a minimum, a suitable test should assure components will perform satisfactorily in service is that each redundant on-site power source and its load identified and performed. For on-site emergency pow er group can function without any dependence upon any systems designed in accordance with Regulatory Guid es other redundant load group or portion thereof.

1.6 and 1.32 (Safety Guides 6 and 32) this gui4de describes an acceptable method of complying with tlhe Commission's regulations with respect to verifying tl lie

C. REGULATORY POSITION

proper assignments of redundant load groups to tihe related on-site power sources. The Advisory Committ,De As part of the initial preoperational testing program, on Reactor Safeguards has been consulted concerniinig and also after major modifications or repairs to a this guide and has concurred in the Regulatory positio n. facility, those on-site electric power systems designed in accordance with Regulatory Guides 1.6 and 1.32 (Safety

B. DISCUSSION

Guides 6 and 32) should be tested as follows to verify the existence of independence among redundant on-site An on-site electric power system designed in power sources and their load groups.

accordance with Regulatory Guides 1.6 and 1.32 (Safeity 1. The plant electric power distribution system, Guides 6 and 32) will consist of redundant pow er not necessarily including the switchyard and the startup sources and load groups that are independent of eac:h and auxiliary transformers, should be isolated from the other. Such a design will conform to the provisions 4of off-site transmission network. Preferably, this isolation Section 5.2.2(5) of IEEE Std 308-1971.' Secticin should be effected by direct actuation of the

5.2.2(5) states: "Auxiliary devices that are required I.0 undervoltage-sensing relays within the on-site system.

operate dependent equipment shall be supplied from a 2. Under the conditions of C.1. above, the on-site related bus section to prevent the loss of electric powier electric power system should be functionally tested successively in the various possible combinations of I IEEE Std 308-1971, "Criteria for Class IE Electric Systeins power sources and load groups with all d-c and on-site for Nuclear Power Generating Stations." Copies may be obtain ed a-c power sources for one load group at a time from the Institute of Electrical and Electronics Enginee rs, completely disconnected. Each test should include United Engineering Center, 345 East 47th Street, New Yoi *k, injection of simulated accident signals, startup of the N.Y. 10017.

USAEC REGULATORY GUIDES Copies of published guides nmy be obtained by request indicating the divisions desired to the US. Atomic Energy Commission, Washington, D.C. 20645, Regulatory Guides ar issued to describe and make available to the public Attention: Director of Regulatory Stendards. Comments and sUggestions for methods amccptable to the AEC Regulatory staff of implementing specific parts of Improvements in thee guides "a encouraged end should be sent to the Secretary the Commission's regulations, to delineate techniques used by the staff in of the Commission. US. Atomic Energy Commission, Washington, D.C. 20645,

"evluating spedfic problems or postulated accidents, or to provide guidance to Attention: Chief, Public Proceedings Staff.

applicants. Regulatory Guides are not substitutes for regulations and compliance with them is not required. Methods and solutions different from those set out in The guides are issued in the following tan broad divisions:

the guides will be acceptable if they provide a basis for the findings requisite to the issuance or continuance of a permit or license by the Commission. 1. Power Reactors

6. Products

2. Research and Test Reactors

7. Transportation

3. Fuels and Materials Facilities 8. Occupalional Health Pullo*ed guides will be revised periodically, asappropriate, to accommodate 4. Environmental and Siting 9. Antitrust Review coronst and to reflect new information or experience. 5. Materials and Plant Protection 1

0. General

on-site power source(s) and load group(s) under test, result from improper assignment of loads, e.g., the lack sequencing of loads, and the functional performance of of forced cooling of a vital device.

the loads. Each test should be of sufficient duration to 3. During each test, the d-c and on-site a-c buses achieve stable operating conditions and thus permit the and related loads not under test should be monitored to onset and detection of adverse conditions which could verify absence of voltage at these buses and loads.

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