PNO-I-96-086, on 961205,plant Engineers Identified Three Inadequate Cable Seperation Issues Affecting Reactor Protection Sys.Both Buttons of Either Pair of Trip Push Buttons Required to Be Depressed,To Initiate Manual Trip

PNO-I-96-086:on 961205,plant Engineers Identified Three Inadequate Cable Seperation Issues Affecting Reactor Protection Sys.Both Buttons of Either Pair of Trip Push Buttons Required to Be Depressed,To Initiate Manual Trip

ML20135E431
Person / Time
Site:	Maine Yankee
Issue date:	12/09/1996
From:	Conte R, Jimi Yerokun NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
GL-96-01, GL-96-1, PNO-I-96-086, PNO-I-96-86, NUDOCS 9612110264
Download: ML20135E431 (2)

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a DCS No.: 05000309961205 Date:

Dsctmbsr 9,1996 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PN1-96-086 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verification or evaluation, and is basically j

cll that is known by the Region I staff on this date.

Facility:

Licensee Emergency Classification:

I Maine Yankee Atomic Power Co.

Notification of Unusual Event I

Maine Yankee 1 Alert i

Wiscasset, Maine Site Area Emergency General Emergency X

Not Applicable Docket No.:

050-309 Event Location Code: POW

SUBJECT:

MAINE YANKEE SHUTDOWN DUE TO MANUAL REACTOR TRIP BUTTONS BEING INOPERABLE (SHUTDOWN GREATER THAN 72 HOURS)

On December 5,1996, plant engineers identified three inadequate cable separation issues affecting the reactor protection system. The identification was made during the licensee's review of NRC Generic Letter 96-01 issues. The three cable separation issues are as follows:

(1) 125 Volts DC control power to Reactor Trip Breakers (RTB) 3 and 7 was from Vital DC Bus 4 instead of the expected Vital DC Bus 3. The cables from Reactor Trip Breakers 3 and 7 are routed to the Reactor Protection System in the control room in a cable tray with other cables powered from DC bus 3 as expected, which presents a problem because the RTB control power j

was, incorrectly, from Bus 4.

I (2) 125 Volts DC control power to Reactor Trip Breakers (RTB) 4 and 8 was from Vital DC Bus 3 instead of the expected Vital DC Bus 4. The cables from Reactor Trip Breakers 4 and 8 are routed to the Reactor Protection System in the control room in a cable tray with other cables l

powered from DC bus 4 as expected, which presents a problem because the RTB control power was, incorrectly, from Bus 3.

(3)

Both pairs of Manual Reactor Trip Push Buttons in the Control Room had wires from all four safety channels wrapped together in the control board from where they exit their separate conduits to the Trip Push Button terminals. The wires should have been individually routed from their conduits to the Push Buttons.

Similar problems were not found in the DC Bus (1 and 2) alignment to their associated RTBs (RTB 1 and 5 from DC Bus 1, and RTB 2 and 6 from DC Bus 2).

To initiate a manual reactor trip, both buttons of either pair of trip push buttons are required to be depressed. The Reactor Trip Push Buttons were still functional, but because they were wired in a way that did not meet the cable separation requirement, they were outside design basis and therefore declared inoperable at 8:47 p.m. Because the Limiting Condition for Operations of Technical Specification 3.9A (at least one set of Manual Push Buttons must be operable) could not be met, the plant entered the remedial action statement of Technical Specification 3.0.A.2 which required a l

reactor shutdown to be initiated within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and the plant to be in Hot Shutdown within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. A reactor shutdown was initiated at 9:45 p.m. and the reactor was in Hot Shutdown condition (suberitical) at 2:21 a.m. on December 6,1996.

9612110264 961209 PDR I&E NM PNO-I-96-086 PDR

DCS No.: 05000309961205 Date:

December 9,1996 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PN1-96-86 The nine automatic trip safety functions of the Reactor Protection System per TS were not affected by this problem.

Other safety related systems have been reviewed for similar problems. The scope of this review over the weekend was: potential and known drawing error problems identified from the GL 96-01 review, interviews with long-time employees for similar logic inconsistencies that may be beyond drawing 1

error problems; and recent electrical modifications. As a result of this review, additional work and tssting was identified and the licensee should be completing those actions today. Startup is expected in the next 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

The State of Maine has been informed.

Contact:

Jimi Yerokun Richard Conte 4

207-882-7519 610-337-5183 l

DISTRIBUTION:

4 OWFN TWFN LST Mail: DCD Chairman Jackson AEOD PDR DOT:Trans only' Comm. Rogers IRM Comm. Dicus ACRS Comm. Diaz Comm. McGaffigan Jr.

OCAA NRC Ops Ctr OIP OCA NMSS OGC OlG INPO" OPA RES NSAC"*

EDO OE OSP NRR* * (Phone Verif: Violet Bowden 415-1168 or 415-1166)

SECY Regional Offices RI Resident Office Licensee:

(Reactor Licensees)

• • General hat for sardng PNs by FAX Region i Form 83 (Rev. August 1996)