PNO-IV-89-048, on 890713,main Transformer 2A Locked Out Due to Transformer Bursting,Causing Mineral Oil to Spill Into Transformer Oil in Recovery Pit.Caused by Loss of Power to Auxiliary Bus.Unit Will Not Be Restarted for 2 to 3 Days

PNO-IV-89-048:on 890713,main Transformer 2A Locked Out Due to Transformer Bursting,Causing Mineral Oil to Spill Into Transformer Oil in Recovery Pit.Caused by Loss of Power to Auxiliary Bus.Unit Will Not Be Restarted for 2 to 3 Days

ML20246N000
Person / Time
Site:	South Texas
Issue date:	07/14/1989
From:	Holler W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
References
PNO-IV-89-048, PNO-IV-89-48, NUDOCS 8907190275
Download: ML20246N000 (2)

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1 July 14, 1989 P'REUMINARYNOTIFICATIONOFEVENTORUNUSUALOCCURRENCE--PN0-IV-89-48  ;

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 all that is known by the Region IV staff on this date.

FACILITY: Houston Lighting 8 Power Company Licensee Emergency Classification: >

South Texas Project, Unit 2 Notification of Unusual Event '

l Docket: 50-499 < Alert Site Area Emergency General Emergency X Not Applicable

SUBJECT:

SHUTDOWN GREATER THAN 48 HOURS BECAUSE OF MAIN TRANSFORMER PROBLEM At 8:02 p.m. (CDT) on July 13, 1989, with South Texas Project, Unit 2 (STP-2),

at 99 percent reactor power, Main Transformer "2A" locked out because of a bursting of the transformer. There was no fire, but the transformer is bulged and the mineral oil in the transformer spilled into the transformer oil

-recovery pit. Cause of>the transformer failure is unknown and is under investigation. Main Transformer "2B" and the South Texas Project, Unit 1, main transformers were not damaged. (There are two main transformers for each unit at South Texas Project. Each of the transformers is three-phase and capable of carrying 50 percent of a unit's main generator electrical output.

The transformers were manufactured by McGraw Edison.)

The STP-2 main transformer lockout caused a main turbine trip which caused areactortrip)(P-9 reactor power. Interlock;reactortripon.turbinetripabove50 Systems percent functioned normally on the trip. Loss of the STP-2 main transformer also caused a loss of non class-1E electrical power and the reactor coolant pumps. Operators used SG PORVs and auxiliery feedwater to control reactor coolant system temperature while STP-2 was on natural circulation. A reactor coolant pump was started approximately 52 minutes after the trip when the non class-1E busses were reenergized. No pressurizer code safety valve or PORVs opened. Pressurizer level stayed within its ,

expected level band. All reactor coolant system parameters remained within their expected bands for a reactor trip from high power.

The main transformer lockout caused a loss of power to the STP-2 auxiliary bus. At the time, "A" ESF train was supplied from the auxiliary bus and "B" and "C" ESF trains were supplied from the standby bus which was supplied from offsite power. The standby diesel generator for the "A" ESF train started and sequenced on loads. The "A" ESF train was supplied by the diesel generator for approximately 45 minutes. The other two ESF trains remained supplied by offsite power throughout the event.

(HL&P) will rct restart STP-2 for at least 2 Houston or 3 days.Lighting STP-2 &is Power in Mode Company 3 (bot standby). STP-2 could be operated at l 50 percent of rated electrical capacity with the undamaged Nain Transformer "2B". HL&P estimates lead times for a new transformer from 40 to l 72 weeks.

South Texas Project, Unit 1, remained at 100 percent reactor power throughout the event. Unit 1 is scheduled to begin a 55-day refueling outage on /d August 4, 1989.

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i e f *- YN0-'IV-89 . . .

The SRI is mohitoring the licensee's. initial recovery action. - RIV inspectors will monitor the licensee's investigation of the transformer failure.

~

Neither the licensee nor the NRC plans to issue a press release.

The state of Texas has been informed.

Region IV received notification of this occurrence by telephone call from the STPPlantManagerat9:25p.m.(CDT)onJuly 13, 1989.- Detailed information was received from the SRI and licensee personnel at 9 a.m. (CDT) on July 14, 1989.

Region IV,has informed EDO, NRR, AE00, and PA.

This information has been confirmed with a licensee representative.

CONTACT: E. Holler, FTS 728-8287 DISTRIBUTION:

0WFN NMBB NL MAIL: DCS (Orig. IE34)

Chmn. Carr SEGY NM55 XEDU KES DOT (Transp.Only)

Comm. Roberts CA NRR ARM-Comm. Rogers OGC OIG 000 _ FAX: (5520: 07/14/89 0 11:30 a.m.

Comm. Curtiss GPA 01 IlWO Regions & HQ)

ACRS PA SLITP -H-St PDR EDO DE FF NSAC EW-W RRI X5TXP NRC Ops Ctr Licensee (Reactor)

DISTRIBUTION:

NRCRES,'RESPN Research(PaulaDorm)

NRCRM, AEOD AEOD .(Patty Wilson)

NRCRM, BROWN ARM (Karer. Brown)

NRCRMP, 01GDW Inspector & Auditor '(Displaywriter/PC)

NRCRMP, 01DW Investigations (Displaywriter/PC)

INRC02, OPAPN GPA:Public Affairs (Glady Ordaz)

INRC0304, SLIPN GPA: State / Local Indian Tribes Program (Brenda Hill) 1 Nuclear Material Safety & Safeguards (Pat Graaf)

INRC0304,liMSSPN INRC0506, NMSSPN Nuclear Material Safety & Safeguards (Cathy Jenkins)

INRC0708, OEPN INRC1112, NRRPN Enforcement Nuclear Reactor(BettySummers)(DonnaBerean)

Regulation INRC1516, OGCPN General Counsel (Edna Downs)

INRC1718, CARRPN Chairman (Lois Altoft)

INRC1718, ED0PN Executive Director for Operations (Doris Day)

-INRC1718, OCAPN GPA:CongressionalAffairs(JaniceHester)

NRCRI, RIPN Region I NRCRII, RIIPN Region II NRCRIII, RIIIPN Region 111 NRCRIV, RIYP!! Region IV NRCRV, RVPN Region V l

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