05000352/LER-1996-018, :on 960925,single Train HPCI Sys Was Declared Inoperable Due to Loose Signal Cable Connector.Connector Was Replaced on 970102 & Common HPCI Turbine Maint Procedures Have Been Revised

:on 960925,single Train HPCI Sys Was Declared Inoperable Due to Loose Signal Cable Connector.Connector Was Replaced on 970102 & Common HPCI Turbine Maint Procedures Have Been Revised

ML20134E797
Person / Time
Site:	Limerick
Issue date:	02/03/1997
From:	Kantner J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:
Shared Package
ML20134E792	List: 05000352/LER-1996-018, :on 960925,single Train HPCI Sys Was Declared Inoperable Due to Loose Signal Cable Connector.Connector Was Replaced on 970102 & Common HPCI Turbine Maint Procedures Have Been Revised 05000352/LER-1996-018-01, Forwards LER 96-018-01 Which Discusses Event That Occurred on 960925 Re Inoperability of HPCI Sys Due to Loss of HPCI Turbine Speed Signal Caused by Loose Speed Sensor Connector
References
LER-96-018, LER-96-18, NUDOCS 9702070097
Download: ML20134E797 (3)

LER-1996-018, on 960925,single Train HPCI Sys Was Declared Inoperable Due to Loose Signal Cable Connector.Connector Was Replaced on 970102 & Common HPCI Turbine Maint Procedures Have Been Revised

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(1) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(x)
3521996018R00 - NRC Website

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NRC FORM 366 U.S. NUCLEAR REGULATORY C0m lSS10N APPROVED BY OMB NO. 3150 0104 (5;92)

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U.S. NUCLEAR REGULATORY C0 m lSS10N.

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(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 MANAGEMENT AND BUDGET. WASH]NGTON. DC 20503

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Limerick Generating Station, Unit 1 0 000 352 10 4

l TITLE (4) Loose Speed Signal Cable Connector Renders the Singla Train High Pressure Coolant Iniection System Inonerable EVENT DATE (5)

LER NUp6ER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

SEQUENTIAL REVISION FAClLlTV NAME DOCKET NUMBER MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NUMBER 05000 FACILIIY NAME DOCKET NUMBER 09 25 96 96 -- 018 01 02 03 97 05000 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Cnect one or more) (11)

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MODE (9) 1 20.402(D) 20.405(c) 50.73(a)(2)(iv) 73.71(b) i 20.405(a)(1)(1) 50.36(c)(1)

POER y

50.73(a)(2)(v) 73.71(c)

LEVEL (10) 100 20.405(a)(1)ni) 50.36(c)(2) 50.73(a)(2)(vii)

OTHER i

20.405(a)(1)(i n )

50.73(a)(2)(1) 50.73(a)(2)(v111)(A)

(Specify in I

20.405(a)(1)ov) 50.73(a)(2)(ii) 50.73(a)(2)(vni)(B) ht c b low i

20.405(a)(1)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x)

NRC Fonn 366A) 4 LICENSEE CONTACT FOR THIS LER (12)

M.'1E TELEPHONE NUMBER lincluce Area Code)

J. L. Kantner, Manager - Experience Assessment LCS (610) 718-3400 i

COMPLETE ONE LINE FOR EACH COMPONENT F AILURE DiSCRIBED IN lHIS REPORT (13)

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CAUSE

SYSTEM COMPONENT MANUFACTURER

CAUSE

$YSTEM COMPONENT MANUFACTURER R

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SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MUNTH DAY YEA I YES SUBMISSION NO

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X DATE (15) j ABSTRACI (Limit to 1400 spaces, i.e., approximately 15 single-spacea typewritten eines) (16)

U At 1104 hours0.0128 days <br />0.307 hours <br />0.00183 weeks <br />4.20072e-4 months <br /> on 09/25/96, during performance of a surveillance test, the High Pressure Coolant Injection (HPCI) system shutdown on an l

overspeed condition and restarted, cycling several times until the i

operators tripped the system.

The HPCI system was then declared j

inoperable.

A loss of the HPCI turbine speed signal caused the turbine control problem.

Manual control of the HPCI system was also not fully available.

This resulted in the inoperability of a single train safety system.

A loose speed sensor connection was tightened and at 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br />, the HPCI system was declared operable after satisfactory completion of a surveillance test.

There was no accident requiring HPCI system injection and sufficient Emergency Core Cooling Systems were operable to mitigate the consequences of an accident.

The speed sensor cormector was replaced 1/2/97.

Analysis determined that the connector mechanically failed.

The failure was caused by personnel error during maintenance performed in February, 1996 Completed corrective actions include repair of the connector, review of the other unit, and procedu.e revisions.

Ongoing actions include review of this event with appropriate station personnel and

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'U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150 0104 i

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EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATLON COLLECTION REQUEST: 50.0 HRS.

LICENSEE EVENT REPORT (LER)

NNFORMA NA EC DS V E

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j 0FFICE OF MANAGEMENT AND BUDGET WASHINGTON.

FACILITY NAME (1)

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PAGE (3) yg SEQUENTIAL REVISION Ne NuMen 05000 2 0F 4 Limerick Generating Station, Unit 1 352 96

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Unit Conditions Prior to the Event:

Unit 1 was in Operational Conditicn 1 (Power Operation) at 100% power level.

There were no systems, structures or components inoperable that contributed to the event.

Description of the Event:

At 1104 hours0.0128 days <br />0.307 hours <br />0.00183 weeks <br />4.20072e-4 months <br /> on September 25, 1996, licensed Operations personnel l were performing Surv illance Test (ST) procedure ST-6-055-230-1, "HPCI Pump, Valve and Flow Test."

When the High Pressure Coolant Injection (HPCI, EIIS:BJ) system was started, the operators observed i

l valve motion and an increase in HPCI Pump discharge pressure but the HPCI turbine speed still indicated zero (0) rpms. The HPCI turbine shutdown on an overspeed condition, automatically restarted at the turbine overspeed reset point, and shutdown again on an overspeed condition.

This cycling occurred several times until the operators tripped the system. Tne HPCI system was then declared inoperable.

Maintenance / Instrumentation and Controls (I&C) personnel determined that a loose speed sensor connector at the HPCI Turbine caused the loss of turbine speed signal and Main Control Room (MCR) speed indication.

The connector was tightened and maintenance and engineering personnel determined that the connector could still perform its intended function.

Operations personnel declared the HPCI System operable at 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br /> following successful completion of the ST procedure.

An evaluation was performed and concluded that the connector was capable of performing its design function provided that the connector is re-connected and tight.

A four hour notification was made to the NRC at 1448 hours0.0168 days <br />0.402 hours <br />0.00239 weeks <br />5.50964e-4 months <br /> on September 25, 1996, in accordance with the requirements of 10CFR50.72 (b) (2) (iii) (D) since this event resulted in a condition which alone could have prevented the HPCI system frcm fulfilling its intended safety function to mitigate the consequences of an accident.

This report is being submitted in accordance with the requirements of 10CFR50.73 (a) (2) (v) (D).

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• U.S. NUCLEAR REGULATORY COMM15S10N APPROVED BY OMB No. 3150 0104 (5 92)

EXPIRES 5/31/95 l

ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

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WASHINGTON DC 20555-0001. AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104),

0FFICE OF MANAGEMENT AND BUDGET. WASHINGTON. DC 20503.

j FACILilY NAME (1)

DOCKET NUMBER (2)

LER NUPBER (6)

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• 05000 3 op 4 Limerick Generating Station, Unit 1 352 96

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Analysis:

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The consequences of this event were minimal in that no radioactive material was released to the environment as a result of the HPCI system being inoperable.

Additionally, an accident condition did not occur during the time period in which the HPCI system was inoperable, and therefore, the HPCI system was not called upon to perform its intended safety injection function. Sufficient Emergency Core Cooling i

Systems and the Reactor Core Isolation Cooling (RCIC, EIIS:BN) system were available to ensure safe shutdown of the reactor, and to mitigate the consequences of an accident if the HPCI System was not available.

If the HPCI system had been required to operate, HPCI flow would have oscillated above and below its design flow (corresponding to overspeed and reset). Additionally, manual control of the HPCI system was not fully available without the HPCI turbine

] speed indication.

The HPCI system was restored expeditiously by Maintenance /I&C and Operations personnel.

The overspeed shutdown and automatic restart of the HPCI turbine occurred as expected to a loss j

of speed signal feedback in the control system.

1 HPCI system operability was restored at 2100 on September 25, 1996, when the speed connector was properly tightened.

Analysis of the connector upon removal on January 2, 1997, indicated that it had retained sufficient integrity to support system operability from the time it was tightened on September 25, 1996 to its replacement on Jaluary 2, 1997.

Cause of the Event

The loss of speed signal to the HPCI control logic was caused by improper reconnection of the speed sensor connection (personnel error)in February 1996 during a routine turtine inspection.

The improper connection caused a mechanical failure of the speed sensor connector plug.

Subsequent vibration from HPCI turbine operation ultimately caused an electrical discontinuity.

The exact cause of the improper reconnection could not be determined.

The probable cause was misalignment of the connector as it was tightened.

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. c, NRC f 0M 366A U.S. NUCLEAR REGULATORY C0pmISSION APPROVED BY OMB NO. 3150 0104 (5;92)

EXP!RES 5/31/95 ESTIMATED BURDEN PER RESPONSr TO COMPLY WITH THl$ INFORMATION COLLECTION REQUEST: 50.0 HRS.

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REDUCTION PR(1)ECT (3150 0104),

0FFICE OF MANAGEMENT AND BUEET. WASHINGTON. DC 20603.

FACILITY NAE (1)

DOCKET NUISER (2)

LER NUMER (6)

PAE (3)

YEAR SEQUENEAL REVISION

"""BE" 05000 4 OF 4 Limerick Generating Station, Unit 1 352 96

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Interviews with the technicians involved with the February 1996 maintenance indicated that no difficulties were noticed reconnecting the speed sensor connector, nor were any tools used to assist tightening the connection.

The connection seemed to them to be properly made.

Satisfactory post-maintenance testing in February 1996 confirmed the adequacy of the connection at that time.

The technicians also conveyed their understanding that these style connectors must be hand-tightened.

Existing procedural guidance for maintenance involving these style connectors was deemed to be adequate.

Based on a review of the simplicity of the connector, no special instructions or training are necessary.

Use of this style connector is addressed by standard technician training and is considered skill of the craft.

Corrective Actions

The following corrective actions have been completed.

The connector was replaced on January 2, 1997.

The connesdor continuity checks described in revision 0 to this LER were not required to be performed since the connector was replaced before the next HPCI system operation.

The common HPCI Turbine maintenance procedures that disturb the speed sensor connection have been revised to include a caution statement regarding proper assembly of the connection.

Ongoing and future corrective actions include evaluation of the HPCI speed connection for possible design change and dissemination of information, to station personnel who work with these style and similar connectors, about this event and proper cannon plug connector manipulation techniques.

Previous Similar Occurrence:

None