05000327/LER-1987-001, :on 870106,trip Setpoint for Acbs on Shutdown Boards That Feed Control & Auxiliary Bldg Vent Boards Discovered Incorrect.Caused by Design Error.Breaker Trip Settings Will Be Corrected

:on 870106,trip Setpoint for Acbs on Shutdown Boards That Feed Control & Auxiliary Bldg Vent Boards Discovered Incorrect.Caused by Design Error.Breaker Trip Settings Will Be Corrected

ML20210E513
Person / Time
Site:	Sequoyah
Issue date:	02/05/1987
From:	Long J, Nobles L TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-87-001, LER-87-1, NUDOCS 8702100316
Download: ML20210E513 (4)

LER-1987-001, on 870106,trip Setpoint for Acbs on Shutdown Boards That Feed Control & Auxiliary Bldg Vent Boards Discovered Incorrect.Caused by Design Error.Breaker Trip Settings Will Be Corrected

Event date:
Report date:
3271987001R00 - NRC Website

text

...

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 loFl0 l3 "Tfi'p Setpoints For ACBs On Shutdown Boards That Feed Control And Auxiliary Building 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 0l1 O!6 8

7 8l7 O !0 l 1 0l0 0l 2 0 l5 8l 7 o isto go ioi 1 i THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR l (Chere one er more of,ne,enowmph (111 OPE R ATING MODE W q

20 402ft) 20 405tel 60.73(s'12Hrvi 73 71161 ER 20 406teH11bl 50 361cH16 50 73teH2Hvl 73.71 tel i101 (j glg 20 405(eH1Het 50 34teH2) 60 73teH2Hval HE S,or a Aa,ree, 20 408ieH1Hml 50 73teH2H4 50 731eH2Hveult Al J66A1 20 405teH1Hwl SO 73teH2Hal 60 73(eH2HomHB) 20 400 tall 1Het 50 73ieH2Hml 50.73teH2Hal LICENSEE CONTACT FOR TMit LER 4121 NAME TELEPHONE NVM9ER ARE A CODE J. L. Long. Plant Operations Review Staff 61115 817101-1 7121514 COMPLETE ONE LINE FOR EACM COMPONENT F AILURE DESCRIBED IN TMit REPORT 1131

^ C.

REPORTA LE

• ^

C REPORTA LE

CAUSE

Sv' TEM COMPONENT

CAUSE

Sv 5TtM COvPONENT p

7 I

I I I I I I I

I I I I I I I

I f I I I I I

I I I I I I SUPPLEMENTAL REPORT EXPECTED (1er MONTH DAY vfAR vf 5 (19 vn som, tere EXPECTED $UGwSSION DA TE)

NO l

l l

A.n R AC T a,m,, M r = e,-., e. e,,..-->, u-o., e -ce,oew-,w. e.m.>

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

The root cause of this event was a design error.

Sargent and Lundy was contracted to review TVA's minimum set of calculations for electrical equipment needed before restart of unit 2.

One deficiency that was identified was the lack of ampacity calculations and coordination. After this deficiency was identified, the Division of Nuclear Engineering performed the required calculations and determined that the trip settings for the ACBs that feed three of the Control and Auxiliary Building vent boards were incorrect.

It has been determined that the present trip settings of the feeder breakers could not be exceeded except following a safety injection (SI) and a Phase A or Phase B isolation. Currently the automatic SI signal is blocked, and with both units in mode 5, insufficient energy exists in the reactor coolant system to attain a containment pressure equal to the Phase A or Phase B isolation setpoint.

Additionally, it is highly improbable that all of the connected loads on any given Control and Auxiliary Building vent board would be up and running at any given time. Therefore, no immediate operability problems exist.

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

8702100316 870205 gg

%C ** "*

PDR ADOCK 05000327 S

PDR V\\

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

"StlWt' "t?,7; "aa Sequoyah, Unit 1 0 l5 l 0 l 0 l 0 l3 l 2 l 7 8l7 0l @ 1 0l0 0l2 OF 0l 3 TEXT t# more epace i, soeunNf, W8, SMBURAf MC Ferm 3084's)(17)

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 degrees F), it was discovered that the trip setpoints for continuous overcurrent were incorrect for the feeder breakers supplying power to three Control and Auxiliary Building 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 has a trip setting of 392 amperes and feeds Control and Auxiliary Building vent board 1Al-A which has a total connected load of 444 amperes; (2) ACB 10B on 480 volt shutdown board 2Al-A has a trip setting of 348 amperes and feeds Control and Auxiliary Building vent board 2Al-A which has a total connected load of 417 amperes; and (3) ACB 10B on 480 volt shutdown board 2B1-B has a trip setting of 348 amperes and feeds Control and Auxiliary Building vent board 2B1-B which has a total connected load of 367 amperes. This deficiency was discovered as a result of the "SQN Auxiliary Power System, Class 1 Equipment Ampacity Study" and was documented under Condition Adverse To Quality Report SCR SQNEEB86124 R0.

Upon discovery of incorrect breaker setpoints, the loads that fed from Control and Auxiliary Building vent boards were examined to determine if immediate operability problems existed.

It was determined that the current trip settings of the feeder breakers could not be exceeded, except following a safety injection (SI) and a Phase A or Phase B isolation. Currently the automatic SI signal is blocked, and both units are in mode 5. Insufficient energy exista in the reactor coolant system to attain a containment pressure equal to the Phase A or Phase B isolation setpoint. Therefore, no immediate operability problems exist.

CAUSE OF EVENT

The root cause of this event was a design error. Sargent and Lundy was contracted to review TVA's minimum set of calculations for electrical equipment needed before restart of unit 2.

One deficiency that was identified was the lack of ampacity calculations and coordination. After this deficiency was identified, the Division of Nuclear Engineering performed the required calculations and determined that the trip settings for the Control and Auxiliary Building vent boards were incorrect.

zg:jOaM=..

=.

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 F ActLITV NAME (1)

DOCKET NUMSER (2) ggg gygggg ggg pggg ggg SE$8 mtyyis AL YEAR e

Sequoyah, Unit 1 o l5 l 0 l 0 l c l3 l 2 [7 8[7 0l0l1 0l0 0l 3 OF 0l 3 TaxT rs--..=.= w

- we % assaw nn 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 currents for the various connected loads were conservatively estimated. Additionally, it is highly improbable that all of the connected loads on any given Control and Auxiliary Building vent board would be up and running at any given time.

In fact, surveillances have been performed every 18 months which simulate an SI signal. During this test the equipment associated with an SI starts and runs with the Control and Auxiliary Building vent boards normally loaded. The breakers on the shutdown boards that feed the Control and Auxiliary Building vent boards have never tripped during these surveillances. Therefore, based on the above, there was no effect on the health and safety of the public as a result of this event.

CORRECTIVE ACTION

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

Design standards and criteria have been developed to ensure that conditions similiar to this do not reoccur.

ADDITIONAL INFORMATION

The ACBs are Westinghouse, Type DS-206.

0324Q 1

A TENNESSEE VALLEY AUTHORITY Sequoyah Nuclear Plant Post Office Box 2000 Soddy-Daisy, Tennessee 37379 February 5, 1987 U. S. Nuclear Regulatory Conunission Document Control Dest Washington, DC 20555 Gentlemen:

TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO.

50-327 - FACILITY OPERATING LICENSE DPR REPORTABLE OCCURRENCE REPORT SQRO-50-327/87001 The enclosed licensee event report provides details concerning incorrect trip setpoints for air circuit breakers on the shutdown boards that feed the Control and Auxiliary Building vent boards due to a design error. This event is reported in accordance with 10 CFR 50.73, paragraph a.2.ii.

Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Nobles Acting Plant Manager Enclosure cc (Enclosure):

J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission Suite 2900 101 ' aria.ita Street, NW d

Atlanta, Georgia 30323 Records Center Institute of Nuclear Power Operations Suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 NRC Inspector, Sequoyah Nuclear Plant f[ //

/

An Equal Opportunity Employer