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NnC Form 384 U S NUCLE A31 kEGULATORY COMMISSION

APPROVED OMB NO 3160 0104

LICENSEE EVENT REPORT (LER) '"''a' 8 8 2' "

F ACILITY NAME Ill DOCKET NUMSER (21 PAGEi3a

S=quoyah, Unit 1 o is I o Io I o 131217 1 loF|0 |3"Tfi'p Setpoints For ACBs On Shutdown Boards That Feed Control And AuxiliaryBuilding Vent Boards Were Incorrect Due To A Design Error

EVENT DATE Ill LER NUMSER ($1 REPORT DATE 171 OTHER F ACILITIES INVOLVED (St

MONTH DAY vtAR VEAR IEf Ab : MONTH DAY vfAR F ACILIT v NaadES DOCKET NUMBERill

haucyske Unit 2 015101010131218

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LICENSEE CONTACT FOR TMit LER 4121

NAME TELEPHONE NVM9ER

ARE A CODE

J. L. Long. Plant Operations Review Staff 61115 817101- 1 7121514COMPLETE ONE LINE FOR EACM COMPONENT F AILURE DESCRIBED IN TMit REPORT 1131

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On January 6, 1987, at 1600 EST with units 1 and 2 in mode 5 (cold shutdown), itwas discovered that the trip setpoints for continuous overcurrent were incorrectfor the feeder breakers supplying power to three Control and Auxiliary Buildingvent boards. The deficiency was discovered as a result of the "SQN Auxiliary PowerSystem Class 1 Equipment Ampacity Study."

The root cause of this event was a design error. Sargent and Lundy was contractedto review TVA's minimum set of calculations for electrical equipment needed beforerestart of unit 2. One deficiency that was identified was the lack of ampacitycalculations and coordination. After this deficiency was identified, the Divisionof Nuclear Engineering performed the required calculations and determined that thetrip settings for the ACBs that feed three of the Control and Auxiliary Buildingvent boards were incorrect.

It has been determined that the present trip settings of the feeder breakers couldnot be exceeded except following a safety injection (SI) and a Phase A or Phase Bisolation. Currently the automatic SI signal is blocked, and with both units inmode 5, insufficient energy exists in the reactor coolant system to attain acontainment pressure equal to the Phase A or Phase B isolation setpoint.Additionally, it is highly improbable that all of the connected loads on any givenControl and Auxiliary Building vent board would be up and running at any giventime. Therefore, no immediate operability problems exist.

An Engineering Change Notice will be issued, and the breaker trip settings will becorrected before the restart of unit 2.

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8eRC Form 384A U.S. NUCLEAR EEIULATORY COMMIS810N*

LICENSEE EVENT REPURT (LER) TEXT CONTINUATION AreaovEo oug no aiso-oto.

EXPIRES; 8/31/88

FACILITY NAME (1) DOCKET NUMSER (2) ggg g

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DESCRIPTION OF EVENT

On January 6, 1987, at 1500 EST with unit 1 in mode 5 (0 percent power, 0 psig,111 degrees F) and unit 2 in mode 5 (0 percent power, 300 psig, and 126 degreesF), it was discovered that the trip setpoints for continuous overcurrent wereincorrect for the feeder breakers supplying power to three Control and AuxiliaryBuilding vent boards (EIIS Code ED). The three feeder breakers, trip setpoints,and total connected loads are: (1) ACB 10B on 480 volt shutdown board 1Al-A hasa trip setting of 392 amperes and feeds Control and Auxiliary Building ventboard 1Al-A which has a total connected load of 444 amperes; (2) ACB 10B on 480volt shutdown board 2Al-A has a trip setting of 348 amperes and feeds Controland Auxiliary Building vent board 2Al-A which has a total connected load of 417amperes; and (3) ACB 10B on 480 volt shutdown board 2B1-B has a trip setting of348 amperes and feeds Control and Auxiliary Building vent board 2B1-B which hasa total connected load of 367 amperes. This deficiency was discovered as aresult of the "SQN Auxiliary Power System, Class 1 Equipment Ampacity Study" andwas documented under Condition Adverse To Quality Report SCR SQNEEB86124 R0.

Upon discovery of incorrect breaker setpoints, the loads that fed from Controland Auxiliary Building vent boards were examined to determine if immediateoperability problems existed. It was determined that the current trip settings

of the feeder breakers could not be exceeded, except following a safetyinjection (SI) and a Phase A or Phase B isolation. Currently the automatic SIsignal is blocked, and both units are in mode 5. Insufficient energy exista inthe reactor coolant system to attain a containment pressure equal to the Phase Aor Phase B isolation setpoint. Therefore, no immediate operability problemsexist.

CAUSE OF EVENT

The root cause of this event was a design error. Sargent and Lundy wascontracted to review TVA's minimum set of calculations for electrical equipmentneeded before restart of unit 2. One deficiency that was identified was thelack of ampacity calculations and coordination. After this deficiency wasidentified, the Division of Nuclear Engineering performed the requiredcalculations and determined that the trip settings for the Control and AuxiliaryBuilding vent boards were incorrect.

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NRC Form 306A U.S. NUCLEUR KETUL ATORY COMMIS$10N* ' ' '

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION omovEO ous No siso-oio.

EXPIRES: 8/31/88

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ANALYSIS OF EVF.NT

This condition is reportable under 10 CFR 50.73, paragraph a.2.ii.

As stated before, no immediate operability problems exist. The load currentsfor the various connected loads were conservatively estimated. Additionally, itis highly improbable that all of the connected loads on any given Control andAuxiliary Building vent board would be up and running at any given time. Infact, surveillances have been performed every 18 months which simulate an SIsignal. During this test the equipment associated with an SI starts and runswith the Control and Auxiliary Building vent boards normally loaded. Thebreakers on the shutdown boards that feed the Control and Auxiliary Buildingvent boards have never tripped during these surveillances. Therefore, based onthe above, there was no effect on the health and safety of the public as aresult of this event.

CORRECTIVE ACTION

An Engineering Change Notice will be issued and the breaker trip settings willbe corrected before the restart of unit 2. Design standards and criteria havebeen developed to ensure that conditions similiar to this do not reoccur.

ADDITIONAL INFORMATION

The ACBs are Westinghouse, Type DS-206.

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TENNESSEE VALLEY AUTHORITYSequoyah Nuclear PlantPost Office Box 2000

Soddy-Daisy, Tennessee 37379

February 5, 1987

U. S. Nuclear Regulatory ConunissionDocument Control DestWashington, DC 20555

Gentlemen:

TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO.50-327 - FACILITY OPERATING LICENSE DPR-77 - REPORTABLE OCCURRENCE REPORTSQRO-50-327/87001

The enclosed licensee event report provides details concerning incorrecttrip setpoints for air circuit breakers on the shutdown boards that feed theControl and Auxiliary Building vent boards due to a design error. Thisevent is reported in accordance with 10 CFR 50.73, paragraph a.2.ii.

Very truly yours,

TENNESSEE VALLEY AUTHORITY

L. M. NoblesActing Plant Manager

Enclosurecc (Enclosure):

J. Nelson Grace, Regional AdministratorU. S. Nuclear Regulatory CommissionSuite 2900101 ' aria.ita Street, NWdAtlanta, Georgia 30323

Records CenterInstitute of Nuclear Power OperationsSuite 15001100 Circle 75 ParkwayAtlanta, Georgia 30339

NRC Inspector, Sequoyah Nuclear Plant

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An Equal Opportunity Employer