ML18065A329

LER 95-013-00:on 951103,circuit Fuse Coordination Deficiency Which Affects App R Safe Shutdown Equipment Noted.Design of Fuse Coordination in Potential Transformer Circuits Will Be Evaluated & Modified as required.W/951204 Ltr

ML18065A329
Person / Time
Site:	Palisades
Issue date:	12/04/1995
From:	Smedley R, Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-95-013, LER-95-13, NUDOCS 9512110171
Download: ML18065A329 (6)

Text

consumers

• Power POWERING lllllCHlliAN-S PROGRESS Palisades Nuclear Plant: 27780 Blue Star Memorial Highway, Covert, Ml 49043 December 4, 1 995 U S Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT LICENSEE EVENT REPORT 95-013 - CIRCUIT FUSE COORDINATION DEFICIENCY WHICH AFFECTS APPENDIX R SAFE SHUTDOWN EQUIPMENT Licensee Event Report (LER)95-013 is attached. This event is reportaQle to the NRC in accordance with 1OCFR50.73(a)(2)(ii)(B) as a condition outside *the plant design basis.

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SUMMARY

OF COMMITMENTS This letter contains two new commitments as follows:

• 1 .* Evaluate the design of fuse coordination in the Diesel Generator 1-1

. potential transformer circuits and modify the design as required to provide proper coordination. *

2. Continue hourly fire tours in the Cable Spreading Room or other appropriate

• compen.satory measur~s until the potential transformer fuse coordination deficiency is resolved for Diesel Generator 1-1 .

CC Administrator, Region Ill, USN RC Project Manager, NRR, USNRC NRC Resident Inspector - Palisades Attachment ..... ~ ~ _

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e. *.' *. ~ . . *' '** . ....

A CMS ENER6Y COMPANY

• ATTACHMENT CONSUMERS POWER COMPANY PALISADES PLANT DOCKET 50-255 CIRCUIT FUSE COORDINATION DEFICIENCY WHICH AFFECTS APPENDIX R SAFE SHUTDOWN EQUIPMENT

NRC Form 366 U.S. NUCLEAR REGULATORY COMMISSION (9-83) APPROVED OMB NO. 3150-0104 EXPIRES: 8131185 LICENSEE EVENT REPORT (LERI FACILITY NAME 11 I DOCKET NUMBER 121 PAGE 131 Palisades Plant o s I Io Io Io I Is Is 2 1 I OF 0 14 TITLE l4J LICENSEE EVENT REPORT 95-01 3 - CIRCUIT FUSE COORDINATION DEFICIENCY WHICH AFFECTS APPENDIX R SAFE SHUTDOWN EQUIPMENT EVENT DATE 151 LEA NUMBER (61 REPORT DATE (6) OTHER FACILITIES INVOLVED (Bl MONTH DAY YEAR YEAR SEQUENTIAL NUMBER I REVISION NUMBER MONTH DAY YEAR FACILITY NAMES

• • • • • • • • • • • • N/A o I Io Io Io I I 5

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, I, 013 9 5 915 o I , 13 01*0 , I2 ol4 915 N/A 0151010101 I THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR I: (Check one or more of the !~/lowing/ (11)

OPERATING N 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73.71(b)

MODE 19)

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POWER LEVEL (10) ., I o lo -

20.405(a)(1 )(ii 20.405(a)(1)(ii) 20.4051aH1Hiiil

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50.36(c)(1) 50.361cH21 50.73laH2Hil

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50. 73(ali2Hvl

50. 73(a)(2)(vii)

50. 73(all2Hviii)(A)

-- 73.71(cl OTHER (Specify in *Abstract below and in Text.

20.405(a)(1 )(iv) -x 5.0.73laH2Hiil * - 50. 73(a)(2)(viii)(B) NRC Form 366A)

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• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • .. *************************** 20.405(a)(11M

- 50.73(a)(2)(iii) - 50. 73(a)(2Hxl

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LICENSEE CONTACT FOR THIS LEA (12)

NAME TELEPHONE NUMBER

. Robert A Vincent, Licensing Supervisor :R,EA,CI°~ I 7 I 6 I 4 I - I 8 I I , I 9 3 COMPLETE ONE LINE, FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 113)

MANUFAC- REPORTABLE MANUFAC- REPORTABLE i **

CAUSE SYSTEM COMPONENT TURER TO NPRDS CAUSE SYSTEM COMPONENT TURER TO NPRDS ................

• • • • • • • • • • • • • • • • • • • • • • ***

I I I I I I I I I I I I I I I / }

I I I I I I I *, I I I I I I I .I SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR

• 1***1**********:************

.. EXPECTED

- - - , YES (If yes, complete EXPECTED SUBMISSION DATE).

ABSTRACT (limit to 1400 speces, i.e., approximately fifteen single-spece typewrirten lines) (16) hlNO SUBMISSION DATE (151 I I r On November 3, 1995 at 11 :00 a.m., with the plant operating at full power, it was discovered that fuses in the potential transformer (PT) circuit for Diesel Generator 1-1 were not properly coordinated. The lack of coordination* could result in the' PT primary side fuse blowing when Appendix R fire-related faults appear on a PT secondary si~e circuit. Failure of the primary side fuse would cause a loss of voltage regulation on 1-1 Diesel Generator. The PT secondary side fuse should blow first to prevent fire-induced circuit faults from affecting diesel generator operability.

This condition was identified as a part of-the Pal.isades Plant Appendix R Enhancement Program.

The Appendix R Enhancement Program is reassessing compliance strategies for each fire area, and verifying adequacy of existing analyses and procedural guidance. When this condition was discovered, compensatory measures (hourly fire to.urs of the Cable Spreading Room) were already in place as a precautionary measure in conjunction with the Appendix R Enhancement Project.

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION (9-83) APPROVEO OMB NO. 3150-0104 EXPIRES: 8/31185 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY_ NAME I., I DOCKET NUMBER (2J LEA NUMBER (3) PAGE (4)

SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0 5 0 0 0 2 5 5 9 5 0 1 3 0 0 Q 2 OF 0 4 EVENT DESCRIPTION On November 3, 1995 at .11 :00 a.m., with the plant operating at full power, it was discovered that fuses FUZ/A 1020-1 did not properly coordinate with fuses FUZ/A 1107-4 in the potential transformer (PT) circuit for Diesel Generator 1-1. FUZ/A 1107-4 is the primary fuse set for the Diesel Generator 1-1 PT circuit, and FUZ/A 1020-1 is a fuse set on a secondary side PT circuit which is located in the Control Room and Cable Spreading Room. A fire occurring in either the Control Room or Cable Spreading Room could cause faults in this circuit which, due to the lack of fuse coordination, could cause the primary side fuse to blow before the secondary side circuit fuse. Failure of a primary side fuse would cause a loss of automatic and manual voltage cont~ol on the generator. The PT secondary circuit fuses should blow first to prevent fire-induced circuit faults from affecting diesel generator operability.

The coordination problem within this circuit is not due to improper sizing of the fuses, but rather the improper selection of fuse types. The secondary side fuses in question are 6-1 /4A dual e'ement time delay type. The primary side fuses are 1A (equivalent to 20A secondary current when adjusted for 20: 1 turns ratio of the transformer) fast acting types. The time-curr~nt characteristics of these fuse types are such that a large secondary current could translate into a primary current high enough to blow the primary fuses before the secondary fuses have time to blow.

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This event is postulated only for a theoretical exposure fire occurring in the Control Room or Cable Spreading Room in accordance with 1OCFR50 Appendix R. No other conditions are postulated to cause this event. It should also be noted that Diesel Generator .1-2 has a similar design, but that the Palisades Appendix R safe shutdown analyses only credit the operation of Diesel Generator 1-1 for these fire areas. -

This condition was identified as a part of the Palisades Plant Appendix R Enhancement Program.

The Appendix R Enhancement Program is* reassessing compliance strategies for each fire area, and verifying adequacy of existing analyses and procedural guidance. When the condition was discovered, compensatory measures (hourly fire tours of the Cable Spreading Room) were already in place as a precautionary measure in conjunction with the Appendix R Enhancement Project.

CAUSE OF THE EVENT The lack of fuse coordination in the Diesel Generator PT circuit appears to be an original design deficiency with one of two possible causes:

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION (9-1!3) APPROVEO OMB NO. 3150-0104

'*' EXPIRES: 8/31185 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME (') OOCKET NUMBER (21 LER NUMBER (31 PAGE (4)

SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0 5 0 0 0 ~ 5 5 9 5 0 1 3 Q Q Q 3 OF Q 4

1. The coordination problem within this circuit is due to the improper selection of fUse types during original plant design and construction. It is probable that the original designers of thi circuit did not perform a fuse coordination analysis which considered time-current characteristics. Fuse coordination at the instrumentation level did not have great visibility as a potential concern until the advent of 1OCFR50 Appendix R, well after Palisades was constructed.

2. Activities since original design which caused these fuses to be reviewed appear to have relied on judgement that the fuse sizes were coordinated, and did not review the actual time current characteristics.

ANALYSIS OF THE EVENT The fire areas of concern for this condition are the Control Room and Cable Spreading Room.

The Control Room is continuously manned during power operation and primarily contains control and monitoring equipment that is powered at relatively low voltages and currents. This type of equipment generally overheats before it develops into a fire, and the personnel stationed in this area would likely notice the characteristic aroma of overheated equipment before a fire could develop. In addition, the Control Room has general area automatic fire detection, fire detection located in the cabinets, and manual fire suppression capab_ility to ensure a fire is quickly identified and extinguished before significant damage could occur. The Cable Spreading Room has automatic fire detection, automatic fire suppression, and manual fire suppression capability. The fire detection system will give early notification to the Control Roo"m operators of a fire in this area. The construction materials and type of equipment used in these areas are designed to minimize the potential for a fire. A well trained plant fire brigade is also available to respond to plant fires* in any plant area; If a fire were to-occur, these fire protection features _and the existin electrical separation would limit the spread and size of the fire. Therefore, it is highly unlikely a

.fire could develop and grow to such a degree as to cause. damage to the specific diesel generator circuits in question.

A theoretical Appendix R fire in either the Control Room or Cable Spreading Room is postulated to occur concurrently-with a loss-of- all- offsite power, thus forcing reliance upon the installed diesel generators for 2400 VAC and 480 VAC power. Under a postulated Appendix R fire scenario, the assumption is made that all circuits in these areas will be damaged regardless of any protection features provided or any separation between circuits. Palisades currently has no analysis supporting the post fire safe shutdown of the plant which considers a loss of all 2400 V AC power. While analyses do exist for station blackout events, they are not assumed to occur coincident with an Appendix R fire in these areas.

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NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION

\ (9:83) APPROVED OMB NO. 3150-0104 EXPIRES: 8/31/85 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME 1i I DOCKET NUMBER (2) LER NUMBER (31 PAGE (4)

SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0 5 0 0 0 2 5 5 9 5 0 3 0 0 0 4 . OF 0 4 Based on the discussion above, we concluded that even though the exact potential consequences of this condition are not known, the probability of this condition actually occurring is extremely remote. Therefore, we do not consider this design deficiency as having significant safety implications.

CORRECTIVE ACTION The following corrective actions will be taken:

1. Evaluate the design of fuse coordination in the Diesel Generator 1-.1 potential transformer circuits and modify the design as required to provide proper coordination.

2. Continue hourly fire tours in the Cable Spreading Room or .other appropriate compensatory measures until the potential transformer fuse coordination deficiency is resolved for Diesel Generator 1-1 .