ML20244C294

Advises Tht Util 890329 Request for Approval to Use Fuses for Electrical Isolation of non-Class 1E Dc Power Sys Acceptable Provided That Circuit Breaker in Parallel to Two Fuses Locked Open

ML20244C294
Person / Time
Site:	Byron, Braidwood, 05000000
Issue date:	06/09/1989
From:	Olshan L Office of Nuclear Reactor Regulation
To:	Kovach T COMMONWEALTH EDISON CO.
References
TAC-72847, TAC-72848, TAC-72849, TAC-72850, NUDOCS 8906140201
Download: ML20244C294 (6)

Text

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. June 9, 1989 l

DISTRIBUTION Docket Nos. 50-454, 50-455, 50-456, and 50-457 (UEreTTTTF"@ NRC & Local PDR PDIII-2 r/f PShemanski MVirgilio LLuther L01shan~ EJordan Mr.z Thomas. J. Kovach BGrimes ACRS(10)

. Nuclear Licensing Manager SSands

< Commonwealth Edison Company Post Office Box 767 Chicago, Illinois .60690

SUBJECT:

USE OF FUSES FOR ELECTRICAL ISOLATION AT BYRON /BRAIDWOOD (TAC NOS. 72847,72848,72849,AND72850)

.By letter dated March 29, 1989, you requested approval to use fuses'for electrical isolation of non-class 1E de power systems at Byron /Braidwood.

Enclosed is our Safety Evaluation which concludes that your proposal-.is acceptable provided that the circuit breaker which is in parallel to the two fuses is locked open. An acceptable alternative is to physically remove this breaker.

This completes action on TAC Numbers 72847, 72848, 72849, and 72850.

7 Leonard N. Olshan, Project Manager Project Directorate III Division of Reactor Projects III, IV, V, and Special Projects

Enclosure:

As stated cc w/ enclosure:

See next page PDIII-2 PDIII-2 f5

~PDIII-2 A PDIII-2 f/U L01shan:km SSands LLuthe jr PShemanski 6/ 7 /89 6/ p /89 6/ F /B9' 6/ f /89 f.0

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UNITED STATES E

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4*o% NUCLEAR REGULATORY COMMISSION is i $ WASHINGTON, D. C. 20555 e

'g / June 9, 1989 Docket Nos. 50-454, 50-455, 50-456, and 50-457 Mr. Thomas J. Kovach Nuclear Licensing Manager Commonwealth Edison Company Post Office Box 767 Chicago, Illinois 60690

SUBJECT:

USE OF FUSES FOR ELECTRICAL ISOLATION AT BYRON /BRAIDWOOD (TACNOS. 72847,72848,72849,AND72850)  ;

By letter dated March 29, 1989, you requested approval to use fuses for electrical isolation of non-class 1E de power systems at Byron /Braidwood.

Enclosed is our Safety Evaluation which concludes that your proposal is acceptable provided that the circuit breaker which is in parallel to the two fuses is locked open. An acceptable alternative is to physically remove this breaker.

This completes action on TAC Numbers 72847, 72848, 72849, and 72850.

[@ N. phA Leonard N. 01shan, Project Manager Project Directorate III-2 Division of Reactor Projects III, IV, V, and Special Projects

Enclosure:

As stated cc w/ enclosure:

See next page

l Mr. Thomas J. Kovach Byron /Braidwood Power Station Commonwealth Edison Company Units 1 and 2 cc:-

Mr. Jack Tain Dr. Bruce von Zellen Atomic Power Distribution Department of Biological Sciences Westinghouse Electric Corporation Northern Illinois University Post Office Box 355 DeKalb, Illinois 61107 Pittsburgh, Pennsylvania 15230 U. S. Nuclear Regulatory Commission Joseph Gallo, Esq. Byron / Resident Inspectors Office Hopkins and Sutter 4448 North German Church Road 1050 Connecticut Ave., N.W. Byron, Illinois 61010 Suite 1250 Washington, D.C. 20036- Ms. Lorraine Creek Rt. 1, Box 182 C. Allen Bock, Esquire Manteno, Illinois 60950 Post Office Box 342 Urbana, Illinois 61801 Mrs. Phillip B. Johnson 1907 Stratford Lane Regional Administrator Rockford, Illinois 61107 U. S. NRC, Region III 799 Roosevelt Road, Bldg. #4 Douglass Cassel, Esq.

Glen Ellyn, Illinois 60137 109 N. Dearborn Street Suite 1300 Ms. Bridget Little Rorem Chicago, Illinois 60602 Appleseed Coordinator 117 North Linden Street Ms. Pat Morrison Essex, Illinois 60935 913 N Main Street #707 Rockford, Illinois 61103-7058 Mr. Edward R. Crass Nuclear Safeguards and Licensing David C. Thomas, Esq.

Division 77 S. Wacker Drive Sargent & Lundy Engineers Chicago, Illinois 60601 55 East Monroe Street Chicago, Illinois 60603 Mr. Charles D. Jones, Director Illinois Emergency Services U. S. Nuclear Regulatory Connission and Disaster Agency Resident Inspectors Office 110 East Adams Street RR#1, Box 79 ' Springfield, Illinois 62706 Bracev111e, Illinois 60407 l

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Mr. Thomas J. Kovach _ Byron /Braidwood j; Consnonwealth Edison Company cc:

. Mr. Michael C. Parker, Chief

. Division of Engineering Illinois Department of Nuclear Safety 1035' Outer Park Drive Springfield, Illinois 62704 Michael Miller, Esq.

Sidley and Austin-One First National Plaza Chicago, Illinois 60603 George L. Edgar

.Newman & Holtzinger, P.C.

1615 L Street, N.W.

Washington, D.C. 20036 Commonwealth Edison Company Byron Station Manager 4450 North German Church Road Byron, Illinois 61010

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> ENCLOSURE 1 USE OF FUSES FOR ELECTRICAL ISOLATION COMMONWEALTH EDISON BYRON 1&2, BRAIDWOOD 1&2 DOCKET N05. 50-454/455/456/457 l

1.0 INTRODUCTION

In the existing 125V de design, the separation of non-Class IE circuits from Class 1E system is provided by two Class 1E breakers. These breakers are co-ordinated with their upstream breaker and are periodically tested to verify coordination. In order to eliminate the periodic testing required to verify coordination, the licensee, by letter dated March 29, 1989, has proposed modi-fication to install two fuses (in series) connected in parallel with the main feed breaker.

. 2.0- EVALUATION:'

Commonwealth Edison has proposed a design modification to the 125V dc system that utilizes fuses for isolation of the non-Class 1E loads from the Class 1E buses. In the proposed modification, two fuses (in series) will be connected in parallel with the main feed breaker servicing the non-safety loads. The licensee states that this main feed breaker would then be normally operated in theopen(N.O.) position. This operation of breaker would be controlled by ad-ministrative procedure allowing it to be closed only when necessary for main-tenance, inspection, replacement of the fuses. The licensee will provide two Class 1E fuses connected in series and coordinated with their upstream breaker.

Periodic testing of fuses in de power circuits, to verify coordination is not required provided that each fuse is tested (for example, resistance measurement) to verify overcurrent protection as designed. In lieu of periodic testing, a documented periodic inspection and maintenance procedure shall be implemented which will ensure:

a) that the proper size and type of fuse is installed, b) that the fuse shows no physical sign of deterioration, and c) that the fuse connections are tight and clean.

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We have reviewed the licensee's submittal and have found that a fuse will provide power circuit isolation reliability which may be higher than that for a circuit breaker tripped by fault current as supported by the data on fuses and breakers in IEEE Std. 500-1977 forlowvoltage(upto1000V) power systems. Therefore, it is acceptable to use two fuses in series for electrical isolation in de power circuits. However, the circuit breaker across which the fuses will be installed should be locked open.

3.0 CONCLUSION

We have reviewed the licensee's submittal and have concluded that a fuse will provide power circuit isolation reliability which may be higher than for a circuit breaker as supported by the data on fuses and breakers in IEEE Std. 500-1977 and, thdrefore, the use of two fuses as isolation device for dc circuits is acceptable. However, the breaker across which these fuses will be installed should be locked open.

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