ML20046C779

LER 93-009-00:on 930715,receipt of Annunciator Charging Pump 12 Overload Trip Observed by CR Operators,Resulting in Unplanned Closure of Containment Isolation Valve.Standby Charging Pump Started Immediately

ML20046C779
Person / Time
Site:	Prairie Island
Issue date:	08/05/1993
From:	Hunstad A NORTHERN STATES POWER CO.
To:
Shared Package
ML20046C775	List: ML20046C774 ML20046C779
References
LER-93-009, LER-93-9, NUDOCS 9308120100
Download: ML20046C779 (3)

Text

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NRC FORQ 366 ~ U.S. CUCLEAR REGULAT O Y Cupe(ISSI O APPROVED BY OMB No. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

LICENSEE EVENT REPORT (LER) FORWARD COMMENTS REGARDING BURDEN ESilMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, (See reverse for required number of digits / characters for each block) WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGFMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY KAME (1) DOCKET NUMBER (2) PAGE (3)

Prairie Island Nuclear Generating Plant U1 05000 282 1 OF 3 TITLE (4) Unplanned Closure of a Containment Isolation Valve EVENT DATE (5) trR NtMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

SEQUENTIAL REVISION MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NUMBER NUMBER

'#C' ""*' C 07 15 93 93 --

09 --

00 08 05 93 0 OPERATING THIS RrP RT IS SusMiTTrD PURSUANT TO THE REQUIRFMENTS OF 10 CFR l- (Check one or more) (11)

N EDDE (9) 20.402(b) 20.405(c) X $0.73(a)(2)(iv) 73.71(b)

POWER 20.405(a)(1)(1) SC.36(c)(1) 50.73(a)(2)(v) 73.71(c) 100 LEVEL (10) 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) OTHER 20.405(a)(1)(iii) 50.73(a)(2)(i) 50.73(a)(2)(viii)(A> (Specify in Abst et ow 20.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B) 20.405(a)(1)(v) 50.73(a)(2)(lii) 50.73(a)(2)(x) NRC Form 366A)

LICENSEE CONTACT FOR THIS LFR (12)

NAME TELEPHONE NUMBER (include Area Code)

Arne A Hunstad 612-388-1121 COMPLETE ONE LINE FOR EACH COMPONENT FAltuRF DESCRIBFD IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER 0 S B CB MO U150 Yes B CB MCC G080 Yes SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY W SUBMISSION yes, complete EXPECTED SUBMISSION DATE). X WO DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten Lines) (16)

On July 15, 1993, Unit 1 was operating at 100% power. At 0157, control room operators observed receipt of the annunciator "12 Charging Pump Overload Trip". Within seconds several other alarms were received (Letdown Orifice Isolation Valve - CLOSED, Low RCP Seal Injection Flow, Low RCP Labyrinth Seal DP) as a result of the trip of No. 12 Charging Pump. Since the pump was the only charging pump operating at the time, trip of the pump caused letdown isolation; the open letdown orifice isolation valve closed.

Letdown orifice isolation valves also function as containment isolation valves. This unplanned closure of the letdown orifice isolation valve was a non-ESF actuation of ESF equipment. The operators started No. 13 Charging Pump, restoring charging flow and reactor coolant pump seal injection flow, and within 2 minutes they restored letdown. The outplant operator investigated the cause of the trip and found that the breaker for No. 12 Charging Pump had tripped. Since No. 11 and 13 Charging Pumps were available, no LCO was entered.

The breaker for No. 12 Charging Pump had tripped when the A phase motor lead grounded to the junction box.

9308120100 930805 "

PDR ADOCK 05000282 to S PDR w

NRC f 0RM 366 (5-92)

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. l NRC FORM 36(d U.S. OCLEAR REGULATc;Y COPMISSIC% APF;0VED BY OMB NO. 3150-0104 .

l (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO LICENSEE EVENT REPORT (LER) THE INroRMATION AND RECORDS MANAGEMENT BRANCH TEXT CONTINUATION (PWBB 7714), U.S. NUCLEAR REGULATORY COMMIS$10N, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

I FACl$TYNAME(1) DOCKET NLMBER (2) LER NUMBER (6? PAGE (3)

YEAR SEQUENTIAL REVISION Prairie Island Unit 1 NUMBER NUMBER 05000 282 93 __ 99 __ 00 TEXT (if more space is reouired, use soditional copies of NRC Form 366A) (17)

EVENT DESCRIPTION On July 15, 1993, Unit 1 was operating at 100% power. At 0157, control room operators observed receipt of the annunciator "12 Charging Pump overload Trip". Within seconds several other alarms were received (Letdown Orifice Isolation Valve - CLOSED, Low RCP Seal Injection Flow, Low RCP Labyrinth Seal DP) as a result of the trip of No. 12 Charging Pump (EIIS Component Identifier P). Since the pump was the only charging pump.

operating at the time, trip of the pump caused letdown isolation; the open letdown orifice isolation valve closed. Letdown orifice isolation valves also function as containment isolation valves. This unplanned closure of the letdown orifice isolation valve was a non-ESF actuation of ESF equipment. The operators started No. 13 Charging Pump, restoring charging flow and reactor coolant pump seal injection flow, and within 2 minutes they restored letdown.

The outplant operator investigated the cause of the trip and found that the circuit breaker (EIIS Component Identifier 52) for No. 12 Charging Pump had tripped and there was a smoky haze in the pump room. Since No. 11 and 13 Charging Pumps were available, no LCO was entered. A Work Request was issued to investigate and repair the cause of the breaker trip.

CAUSE OF THE EVENT The breaker for No. 12 Charging Pump tripped when the A phase motor lead grounded to the junction box. The junction box is mounted on the side of the motor (EIIS Component Identifier MO). During normal pump operation, the motors experience consistent vibration, which caused wear on a motor lead splice.

ANALYSIS OF THE EVENT The event is reportable pursuant to 10CFR50.73 (a) (2) (iv) since a single containment isolation valve experienced an unplanned closure.

This was a non-ESF actuation of a dual function component. The letdown orifice isolation valves are used for routine plant operation and also function as containment isolation valves. The valves are interlocked with the charging pumps; at least one charging pump must be running in order to open a valve. The pump trip caused loss of the open permissive, and the valve closed. The valves are designed for thousands of operations; this one unplanned operation had no deleterious effcet on the equipment. The letdown orifice isolation valves were, at all times, available for their ESF function. Health and safety of the public were unaffected.

e NRC FOAM 366A U.S. I'JCLEAR REGULATORY COPMISSION APP 20VED BY OMB No. 3150-0104

($ -921. EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO

' LICENSEE EVENT REPORT (LER) THE INFORMATION AND RECORDS MANAGEMENT BRANCH TEXT CONTINUATION (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGFMENT AND BUDCET, WASHINGTON, DC 20503.

FAcitITY NAME (1) DOCKET NtMBER (2) LER NLMBER (6'l PAGE (3)

YEAR SEQUENTIAL REVISION Prairie Island Unit 1 NUMBER NUMBER 3@ 3 05000 282 93 __ og __ 00 TEET (if more space is recuired. use additional copies of NRC Form 3663 (17)

CORRECTIVE ACTION A standby charging pump was started immediately and the letdown orifice isolation valve was reopened within 2 minutes.

An outplant operator was sent to investigate cause of the trip.

The motor lead was repaired with a glass tape splice and heat shrunk end caps.

Similar charging pump motor wiring installations are being inspected.

FAILED COMPONENT IDENTIFICATION None.

PREVIOUS SIMILAR EVENTS Several unplanned closures of single containment isolation valves have occurred, but had not been considered reportable until now.

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