NPL-97-0100, Discusses Mcb Wiring Separation Operability Determination & Restoration Plan,Per LERs 91-001-01 & 96-007-00

Discusses Mcb Wiring Separation Operability Determination & Restoration Plan,Per LERs 91-001-01 & 96-007-00

ML20147J276
Person / Time
Site:	Point Beach
Issue date:	04/16/1997
From:	Dante Johnson WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20147J279	List: ML20147J282 NPL-97-0100, Discusses Mcb Wiring Separation Operability Determination & Restoration Plan,Per LERs 91-001-01 & 96-007-00
References
NPL-97-0100, NPL-97-100, NUDOCS 9704240142
Download: ML20147J276 (4)

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Wisconsin Electnc POWER COMPANY Poht Beoch Nuchear Pk2nt (414) 755-2321 6610 Nuclear Rd.. Two Rtvers. WI 54241 NPL 97-01C0 April 16,1977 U.S. NUCLEAR REGULATORY COMMISSION Document Control Desk Mail Station PI-137 Washington,DC 20555 Gentlemen: i

_D_OCKETS 50-266 AND 50-301 MAIN CODEROL BOARD WIRING SEPARATION OPERABILITY DETERMINATION AND RESTORATION PLAN l POINT BEACH NUCLEAR PLANT. UNITS 1 AND 2 l

As reported in LERs 301/91-001-01 and 266/96-007-00, the original design and wiring practices used inside the PBNP main control boards did not include rigorous application of physical separation criteria for wires associated with redundant trains of safety-related equipment and independent instrument channels. This physical separation is one of the important design features that ensure a single fault within one train or channel circuit does not cause damage to the other train or channel circuit and thereby disable a safety function.

Prior to the issuance of the above referenced LERs, we had not considered physical separation of redundant wiring in the main control boards as part of our design or licensing basis. Thisjud9ncat '

was based on the controlled environment provided for these circuits and the overcurrent protection which provided adequate assurance that a single fault would not affect more than one safety-related train or channel. As described in the LER, we determined that such physical separation was, m fact, part of the design basis for PBNP and that there existed a significant number of situatioris where the required separation did not exist. As a result of this discovery, several actions were 'dcr.

(1) Operability of the main control boards was evaluated with respect to a lack of physical separation. The control boards were determined to be operable based on the limited potential for fault initiation in the controlled environment and the existence of overcurrent protection for all circuits in the main control board. This operability determination has recently been

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revised and is enclosed for your review.

(2) As described in the enclosed operability determination, all circuits in the main control boards //

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were reviewed to ensure adequate overcurrent protection. For those circuits with inadequate protection, corrective action was taken to provide the appropriate protection. With one g6 M ,_

l exception noted in the operability determination, these actions have been completed.

, 9704240142 970416 f _ _ _ _

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NPL 97-0100 "

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' April 16,1997 I

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j- -(3) A long-term plan to provide physical separation inside the main control t mds was created.

l That plan included a pilot program to rewire a number of circuits during to 7all 19% Unit 2 outage (U2R22).

f Recently, we have accepted the position that physical separation criteria should be considered a j licensing basis requirement for wiring inside the main control boards. Therefore, we have revised

! our operability determination and developed a mem ambitious plan to restore the subject wiring to full compliance.

[ i On March 10,1997, we participated in a telephone conference with NRC Staff. The purpose of this j conference was to inform the staff of the status of our investigations and corrective actions related to

i. identified instances oflack of redundant train wire separation in the main control boards. During I the conference, we described the basis for our operability determination and our plan to restore the

! required separation for the non-conforming circuits. During the conference, we committed to i docket this information.

I h The plan for'the completion of wire separation in the main control boards (1C03,1C04,2003, j

2C04, C01, and CO2) is based on performing all necessary rewiring during the next refueling outage -I

for each unit. As-built walkdowns of control panel CO2 will be completed in time to provide wire

- routing information so wire rerouting within panel CO2 can occur during the next refueling outage s for each unit. We plan to correct all situations ofinadequate physical separation for the Unit I main

control board wiring during the next Unit I refueling outage (UIR24). This plan includes )

l correcting all situations in common panels C01 and C02 for Unit I and commori circuits. We plan

to correct all situations ofinadequate physical separation for the Unit 2 main control board wirmg

. including Unit 2 related wiring in common panels C01 and C02 during the next Unit 2 refueling outage (U2R23).

l. As discussed during our March 10,1997 telephone conference, we have established that Unit I and i Unit 2 are operable with the identified nonconforming condition associated with the main control board wiring physical separation. Our operability determination demonstrates that redundant safety-related circuits would not be degraded by a single fault. The qualification of wire terminations, wire insulation, and overcurrent protection provide the appropriate level of protection for those instances where separation criteria are not met. In addition, the ' protection provided by overcurrent devices and insulation is~supplemen:ed by the controlled environment of the main control boards, which minimi7es the poter.tial for fault initiation. Our corrective action plan and

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schedule were developed commensurate with the condition's importance to safety. Based on the '

existing protection provided for the circuits, and the aggressive schedule for effecting repairs, no additional compensatory measures have been deemed necessary. A copy of our operability -

determination is enclosed for your review.

l We have considered the guidance in Generic Letter 91-18 and have concluded that main control board wiring physical separation is not a Unit 1 or Unit 2 restart issue. We have also reviewed

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NPL 97-0100 April 16,1997

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i guidance in Generic Letter 91-18 regardmg the application of 10 CFR 50.59 and have reviewed 10 CFR 50.59 implementation guidance in SECY-97-035. We have concluded that a 10 CFR 50.59 evaluation is not required for this nonconforming condition. Pursuant to the requirements of 10 CFR 50, this condition will be appropriately corrected or resolved in accordance with our Appendix B corrective action program.

Please contact us ifyou have any questions.

Sincerely, Douglas F. Johnson-Manager -

Regulatory Services and Licensing hds' Enclosure cc:, NRC Resident Inspector NRC Regional Administrator PSCW

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