ML18066A783

LER 96-013-00:on 961115,DC Breaker Failure During Testing for as-found Trip Setting Occurred.Cause Under Investigation.All molded-case Circuit Breakers in DC Distribution Panels Were Replaced

ML18066A783
Person / Time
Site:	Palisades
Issue date:	12/16/1996
From:	Engle D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
Shared Package
ML18066A781	List: ML18066A779 ML18066A783
References
LER-96-013, LER-96-13, NUDOCS 9612240199
Download: ML18066A783 (3)

Text

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (4195) EXPIRES 4130/98 ESTIMATED IUIDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 HRS. REPORTED LESSONS LEARNED ARE INCORPORATED LICENSEE EVENT REPORT (LER) INTO THE LICENSING PROCESS AND FED BACK TO INDUSTRY. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (T~ F33), U.S. IAJCLEAR REGULATORY COMMISSION, WASHINGTON, DC 2055$.

0001, AND TO THE PAPERWORK REDUCTION PROJECT (31~104, OFFICE OF (See reverse for required number of digits/characters for each block) MANAGEMENT AND BUDGET, WASHINGTON, DC 20503 FACILITY NAME (1)

CONSUMERS POWER COMPANY - PALISADES PLANT DOCKET NUMBER (2) 05000255 f**(3) 1of3 II TITLE(4) LICENSEE EVENT REPORT 96-013, DC BREAKER FAILURE DURING TESTING FOR AS-FOUND TRIP SETIING EVENT DATE (5) LER NUMBER (6) REPORT DATE (7)

• OTHER FACILITIES INVOLVED (8)

MONT:i DAY YEAR YEAR I SEQUENTIAL NUMBER REVISION NUMBER MONTH DAY YEAR

• FACILITY NAME DOCKET NUMBER 05000 FACILITY NAME DOCKET NUMBER 11 15 96 96 - 013 - 00 12 16 96 05000 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check one or more) (11)

MODE (9) N 20.2201(b) 20.2203(a)(2)(v) 50.73(a)(2)(i) 50.73(a)(2)(iii)

I I 20.2203(a)(1) 20.2203(a)(3)(i) 50.73(a)(2)(ii) 50.73(a)(2)(x)

I POWER LEVEL (10) 0 20.2203(a)(2)(i) 20.2203(a)(3)(ii) 50.73(a)(2)(iii) 73.71 0

lll~i-~~i 11~1~'1

20.2203(a)(2)(ii) 20.2203(a)( 4) 50.73(a)(2)(iv) OTHER Iii 20.2203(a)(2)(iii) 20.2203(a)(2)(iv) 50.36(c)(1) 50.36(c)(2)

LICENSEE CONTACT FOR THIS LER (12) x 50. 73(a)(2)(v) 50.l3(a)(2)(vii)

Specify in Abstract below or in NRC Form 366A NAME TELEPHONE NUMBER (Include Area Code)

DALE E. ENGLE, LICENSING ENGINEER (616) 764-2848 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER . REPORTABLE CAUSE SYSTEM COMPONENT . MANUFACTURER . REPORTABLE TONPRDS TONPRDS EC BKR W121 y SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR x

I YES If yes, COMPLETE EXPECTED COMPLETION DATE I NO EXPECTED SUijMISSION DATE (15) 2 18 97 ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On November 15, 1996, at 1400, with the plant shut down for refueling, testing of a DC molded-case circuit breaker revealed that the breaker would not trip on overcurrent. Subsequently, another breaker (72-228) was removed from the same panel for testing. Thi~ breaker also failed to trip." Two additional breakers (72-213 and 72-230) were then removed from the same distribution panel for testing. These breakers, which were installed spares, also failed to trip. These failures resulted in concerns that all 72 DC molded-case circuit breakers installed in certain DC distribution panels might fail to trip when subject to a short circuit. A large number of these breakers act as isolation devices betWeen 1E and non-1 E circuits. A fault in a non-1 E circuit could potentially cause the distribution panel supply fuse to blow, removing power from the panel and affecting power to class 1E circuits. As many of the non-1 E circuits powered from redundant DC distribution panels run in common cable trays, there was also a potential that a common mode failure could affect redundant trains of safety related equipment. All 72 circuit breakers of the type which failed to trip, located in the DC distribution panels, were replaced prior to returning the panels to service.

• --9612240199 *96i216 . --* 707 **-**.

PDR AOOCK 05000255 5 PDR

NRC FORM 366a U.S. NUCLEAR REGULATORY COMMISSION 4195 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION I

FACILITY NAME 11) DOCKET12l LER NUMBER Sl PAGE 13)

YEAR SEQUENTIAL REVISION CONSUMERS POWER COMPANY NUMBER NUMBER 05000255 20F3 PALISADES NUCLEAR PLANT 96 013 00 TEXT (If more space is required, use additional.. copies of NRC Form 366A) (17)

EVENT DESCRIPTION On November 15, 1996, at 1400, with the plant shut down for refueling, testing of a DC Circuit breaker (72-207) revealed that the breaker would not trip on overcurrent. Subsequently, another breaker (72-228) from the same distribution panel was removed from service for testing. This breaker also failed to trip. Two additional breakers (72-213 and 72-230) were* then taken from the same distrit?ution panel for testing. These breakers, which were installed spares, also faileq to

• trip. These failures resulted in concerns that all 72 DC molded-case circuit breakers (MCCBs) installed in the four DC distribution panels might fail to trip when subject to a short circuit. A large

• number of these breakers act as isolation devices between 1E and non-1 E circuits. A fault in a non-1 E circuit could potentially cause the distribution panel supply fuse to blow, removing power from the panel and affecting power to class 1E circuits. As many of the non-1.E circuits* powered from redundant DC distribution panels run in common cable trays, there was also a potential that a common mode failure could affect redundant trains of safety related equipment Consequently, the panels were declared degraded but operable for the existing plant conditions (refueling).*

.safety related functions which could be affected by a lack of 1E to non-1 E isolation in the ~ff!3cted DC panels include: *

-Power Operated Relief Valve (PORV) Actuation Circuitry

-Containment Hydrogen Monitoring System Power

-Reactor Head Vent Valve Power

-480 Volt Load Center Control Power

'-Main Steam Isolation Valve (MSIV) Control Power

.:.shutdown Cooling Valve Control Power *

-Diesel Generator Start Circuitry (auto start only)

--Diesel Generator* Breaker Auto *Close Circuit*

_ A review was performed to evaluate maintenance on other MCCB's. There are no other molded-case circuit breakers which perform a 1E to non-1 E isolation function in the plant.

SAFETY SIGNIFICANCE Until the remaining 68 breakers have been tested, the safety significance of the breaker failures cannot be ascertained. The safety functions potentially affected by the breaker failures are identified above. The most safety significant function that could be lost from a design basis event during plant operation is the automatic start and loading of the diesel generators. For this loss to be of consequence, the event would have to cause shorts in two or more non-Class 1E cables coincident with loss of offsite power. The probability of .such a combination of events is considered to be relatively low.

~' . NRC FORM 366a 4195 U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION I

FACILITY NAME 11 l DOCKET12\ LER NUMBER 16\ PAGE13l YEAR SEQUENTIAL REVISION CONSUMERS POWER COMPANY NUMBER NUMBER 05000255 30F3 PALISADES NUCLEAR PLANT 96 013 - 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

In the existing plant condition (refueling), only one circuit could have affected plant operations.

One valve in the Shutdown Cooling System could have closed due to a loss of DC power;

• however, a by-pass valve would have. allowed the Shutdown Cooling System' flow through the core to continue. An existing procedure addresses this event and provides operations personnel with direction to manually open the closed shutdown cooling valve. Operations personn~I were notified

,ofthis condition to develop a heightened awareness. '* -.

Currently it is known. that there was a loss of 1E to non-1 E isolation on one of the two redundant trains of DC power. If this had been discovered while at power, the associated DC train*would

- have been declared inoperable along with all .the associated safety* func:tions identified above.

A more detailed evaluation of the safety significance oft.his condition will be provided in. a

• supplement to this Licensee Event Report.

• CAUSE OF THE EVENT *

• .. The cause oft.his event is stillunder investigation and.. will be provided in a-supplement to this.

Licensee Event Report.

CORRECTIVE ACTION All molded-case circuit breakers in DC distribution panels were replaced. Replacement breakers were tested prior to installation.

-1nveStigatiori-wiH-corltfriUe to-test 1n*e remaining hlolded.:case GTrCuit-Breakers- ~emove*a*trom-o*c- -*- --

distribution panels D11-1, D11-2, D21-1 and D21-2 to determine a root cause for the failure to trip. Safety significance of the as-found conditions will be reassessed as part of that investigation.

PREVIOUS SIMILAR EVENTS Licensee Event Report 96-005 1

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