ML20028H712

LER 90-035-00:on 901224,14 Valves Associated W/Various Sys & Required to Perform Function of Isolating Primary Containment Determined Inoperable.Caused by Installation Error During Initial const.W/910122 Ltr

ML20028H712
Person / Time
Site:	Limerick
Issue date:	01/22/1991
From:	Doering J, Madsen G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-035-01, LER-90-35-1, NUDOCS 9101290050
Download: ML20028H712 (6)

Text

10 CFR 50.73

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PHILADELPHIA ELECTRIC COMPANY LIMERICK GENER ATING ST ATION P. O. BO X A SAN ATOG A. PENNSYLV ANI A 19464

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'J.?,l1'17. .'."' January 22, 1991 u...................*" Docket Ho. 50-35?

License No, t4PF-39 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

SUBJECT:

Licensee Event Report Limerick Generating Station - Unit 1 This LER reports a condition prohibited by lechnical Specifications (TS) in that Primary Containment isolation valves associated with various systems and required for Unit 1 operation weie inoperable and the Actions required by is were not taken in the appropriate time period. This condition was due to inadequate physical electrical separation between cables due to an original installation error.

Reference:

Docket No. 50-352 Report Number: 1-90-035 Revision Number: 00 Discovery Date: November 29, 1990 Reportability Date: December 24, 1990 Report Date: January 22, 1991 facility: Limerick Generating Station P.O. Box A. Sanatoga, PA 19464 This LER is being submitted pursuant to the requirements of 10 CFR 50.73 (d)(2)(i)(0).

Very truly yours,

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WGS:rgs cc: T. T. Martin, Administrator, Region 1. USNRC

1. J. Kenny, USNRC Senior Resident inspector, LGS 2

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These PC isolation valves were determined to be inoperable due to deficiencies in the physical separation between different divisions of Class 1E wires in Unit i panels 10C609 and 10C623. The appropriate wiring was subsequently sleeved to

, comply with separation requirements. We have concluded that this condition, affecting the operability of the above mentioned PC isolation valves, has existed since October 26, 1984, the date of issuance of the Unit 1 Low Power Operating License. This condition resulted from a failure by construction personnel to properly install the wiring during original construction of LGS

,- Unit 1. lhe consequences of this event were minimal in that no electrical fault condition actually occurred. Corrective actions committed to in LGS Unit 1 LER l-90-024 are currently being implemented, and will adequately address the concerns associated with the potential for future electrical separation deficiencies. Therefore, no further corrective actions are planned.

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Unit 1 Operating Condition was 1 (Power Operation) at a Power Level of 100%.

There were no other structures, systems or components out of service which contributed to this event.

Descripth a of the Event:

On November 29, 1990, during physical electrical separation panel inspections on timerick Generating Station (LGS) Unit 1 initiated as a result of LER 1-90-024, potential physical electrical separation deficiencies between different Class 1E (Ells:ED) electrical division wires were discovered. The deficiencies were located in Unit 1 panels (Ells:PL) 10C609 and 10C623. These deficiencies were documented on administratively controlled Equipment Trouble Tags (ETT). The ETTs resulted in the generation of a Maintenance Request form-(MRF) to implement corrective actions (sleeving of the appropriate wiring with thermal insulating material) for the affected wiring.

LCS Updated final Safety Analysis Report (UFSAR), Chapter 8 " Electrical Power,'

Section 8.1.6.14, states that LGS conforms with the guidance of Regulatory Guide (RG) 1.75, Revision 2, 1978, " Physical independence of Electrical Systems," and also states that except for specific cases delineated in UFSAR Section 8.146.14, a minimum spatial separation distance of six inches will be maintained between Class 1E wiring of_one electrical division and Class 1E wiring of a different electrical division unless barriers are installed. The basis for_this position is to prevent damage to more than one Class 1E divisional circuit that could result from the propagation of a fault condition in another Class 1E divisional circuit during accident conditions.

We initiated an analysis of the configuration of each oi the identified physical electrical separation deficiencies between divisional Class 1E wires. This analysis evaluated the failure of the affected wires during a postulated fault condition to determine whether these wires would droop or sag and result in contact with other wiring such that multiple safety-related systems could be affected. The analysis was completed on December 10, 1990 and plant personnel were informed that specific Class 1E wires in panels 10C609 ano 10C623 could not be satisfactorily analyzed due to their physical configuration and could fail if a fault condition occurred.

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0l0 0l3 or 0l5 ine inadequately separated wiring was evaluated by LGS plant personnel. Thit evaluation identified the systems and valves affected. This evaluation was completed on December 24, 1990 and these wiring deficieacies were determined to affect the following list of motor operated valves designed to automatically close and isolate Prim:ry Containment (PC) in the event of an accident.

onit 1 Panel System Valve 10C609 Reactor Enclosure Cooling Water (RECW) HV-13-108 HV-13-111 Drywell Chilled Water (DCW) HV-87-122 HV.87-123 HV-87-128 HV-87-129 10C623 Main Steam HV-lf022A,8,C,and D HV-lf028A,8,C,and D Rework (i.e., wrapping of ihe appropriate wiring with tnermal insulated sleeving) was initiated in accordanca with a MRF and was completed on December 6, 1990. We have concluded that these electrical separation deficiencies ef f ected the operability of the above mentioned PC isolation valves. Therefore, tnese Unit 1 PC isolation valves should have been considered inoperable. This condition has existed since October 26, 1984, the date of the issuance of the Unit 1 Low Power Operating License. The " Action" required by Technical Specification (TS) Sections 3.4.7 and 3.6.3 were not taken within the specified time period constituting a condition prohibited by TS. This report is being submitted in accordance with the requirements of 10CFR 50.73(a)(2)(1)(B).

Analysis of the Event:

The consequences of this condition were minimal in that no electrical fault condition occurred which resulted in cable degradation and subsequent interaction. Additionally, the cables used at LGS meet the flame test

acceptance criteria of the IEEE-383-1974 Standard and therefore, ignition of l cables resulting in electrical interaction or f ault propagation is extremely unlikely. There was no release of radioactive material as a result of this event, in the event that an actual electrical fault condition occurred in the Unit 1 panel 10C609, and the condition affected the Class 1E wires, the following PC isolation valves could fail to close thereby being unable to perform their designed PC isolation function.

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rut n, . . <. me w m ., nn o HV-13-111 Outboard) o HV-87-122 Inboard) o HV-87-123 Inboard) o HV-87-128 Inboard o HV-87-129 Inboard however, the PC isolation system is designed with redundancy such that for each PC isolation valve listed above, there is an unaffected redundant valve in place to ensure the isolation of the associated PC penetrations. These redundant PC isolation valves ensure that no single failure _(i.e., fault condition) in the PC isolation system can prevent the system from performing its intended function, if an actual electrical fault condition had occurred on the Unit 1 panel 10C609, the fault condition could have potentially affected the ability of an inboard and an outboard main steam isolation valve on the same steam line to automatically close. Therefore, these valves could have failed to perform their designed PC isolation function. However, Main Control Room (MCR) licensed operators would have been able to manually close the affected inboard main steam isolation valve from the NCR, thereby isolating PC.

Additionally, if an actual transient had occurred, MCR operations personnel would have initiated imediate follow up actions to this type of event in accordance with emergency operating procedures. Licensed operators receive requalification training to review and perform operator response to transients of this type. This training provides practice on immediate operator actions and minimizes the length of time certain systems are isolated reducing the impact on the plant. Therefore, as a result of adequate procedural guidance, training, and prompt operator actions, the duration of this type of event would be limited and would have maintained the plant within its design basis.

Cause of the Event:

The cause of this event was an original installation error during the initial construction of Unit 1 in that construction pe sonnel failed to properly install the cabling and the Quality Control (QC) personnel failed to identify this physical separation deficiency.

During Unit 1 construction, panels 10C609 and 10C623 did receive an integrated iinal physical separation inspection. The installation specification E-1412, which provided instruction to construction personnel on the implementation of I divisional physical separation in accordance with the commitments in the UFSAR, l was adequate. However, the construction personnel involved did not properly install this cabling. Subsequently, the QC inspector failed to identify these deficiencies during the integrated final physical separation inspections of these panels.

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based upon the submittal of LGS Unit 1 LER 1-90-024 and associated corrective actions currently being incorporated and implemented, no further corrective actions are planned. These corrective actions are summarized below, o The Installation Section at LGS has developed and implemented a speciel training program that explains the requirements of electrical separation at LGS and the acceptable methods by which physical separation is maintained.

This training is presented to the applicable personnel being processed into the plant for unit refuel outages. In addition, this training was incorporated into the orientation training provided to personnel involved with equipment installations.

o The level of detail and content of the special training program is also being reviewed and appropriately incorporated into existing training programs for other plant personnel having the potential to perform internal panel work.

o inspections of Unit 1 electrical panels were finished and rework has been completed during the Unit 1 third refuel outage.

The corrective actions referenced in LER 1-90-024 will adequately address the cause of this LER.

Previous Similar Occurrences:

LERs 1-88-037, 1-88-042, 1-89-008, 1-89-009, 1-89-022, and 1-89-025 reported conditions involving physical separation deficiencies which resulted in a system

.becoming inoperable. These corrective actions could not have prevented this event due to these wire deficiencies existing since original construction of Unit 1. LER 1-90-024 also reported conditions involving physical separation deficiencies. The corrective actions for LER l-90-024 are currently being implemented and will prevent recurrence.

Tracking Codes: (B) Construction / Installation Deficiency

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