PNO-IV-93-003, on 930203,Unit 2 Tripped from Full Power on low-low Steam Generator Level Resulting in turbine-driven Auxiliary Feedwater Pump 24 Trip on Mechanical Overspeed. Cause Not Determined.Reactor Stabilized in Mode 3

PNO-IV-93-003:on 930203,Unit 2 Tripped from Full Power on low-low Steam Generator Level Resulting in turbine-driven Auxiliary Feedwater Pump 24 Trip on Mechanical Overspeed. Cause Not Determined.Reactor Stabilized in Mode 3

ML20128F188
Person / Time
Site:	South Texas
Issue date:	02/04/1993
From:	Howell A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
References
PNO-IV-93-003, PNO-IV-93-3, NUDOCS 9302110288
Download: ML20128F188 (1)

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.. , . Pcbruory. 4, 1993  ;

ERKhljiMAl3.Y tipTIFICATION OF EVENT OR UNUSillLL OCCURRENCE PNO-IV-93-003 Thio p'rollminary notification constitutes EARLY notico of events of POSSIBLE COfoty or public interest significance. The information is as initially reco1ved without vorification or ovaluation, and is basically all that is -

'known by the Region IV staff on this dato.

Facility Licensee Emeraency Classification Houcton Lighting & Power Co. X Notification of Unusual Evont South Texas 2 Alort W2d: Worth, Texas Site Area Emergency Dock 0ts: 50-499 General Emergency Not Applicablo Subjects UNIT 1 TECHNICAL SPECIFICATION REQUIRED SHUTDOWN; UNIT 2 REACTOR TRIP At 3:26 p.m. (CST) on February 3, 1993, South Texas Project, Unit 2, trippsd from full power on low-low steam generator levol. Loss-than 2 minutcs after receiving a start signal, Unit 2 Turbine-Driven Auxiliary ,

Fcodwater (AFW) Pump 24 tripped on mechanical overspoed. The causo'of the overspood trip has not yet boon datormined. At 9:38 a.m. on February 4,-a.

Notification of Unusual Event was declared when Unit 1 commenced shutting down as a result of not being able to satisfy the action required by.TS 3.7.12.b because Turbino-Driven AFW Pump 14 was inoperablo.

Prior to the Unit 2 trip, at 2:48 p.m., the Unit 2 control room received a high journal bearing turbino end temperature alarm for Steam Generator Fccdwater Pump 21. Foodwater Booster Pump 23 and Startup Foodwater; Pump 24 wore started 4 minutos after the alarm was received to allo; the plant oporators to removo Steam Generator Foodwater Pump 21 from service. Steam G:ncrator Foodwater Pump 21 was secured 8 minutos after the alarm was received.

'At 3:23 p.m., Startup Foodwater Pump 24 tripped while the pump lubo oil filters wore being switched because of high difforontial pressure. Since tho copacity of the two remaining feedwater pumps is 80 porcont reactor pow:r, plant operators-started ramping down the main turbino. The reactor-tripp:d on low-low Steam Generator 2C level loss than 1 second prior to a~

control' room. operator initiating a manual reactor trip. An AFW actuation cignal was generated because of the steam generator low-low level condition. Loss than 2 minutes after receiving a. start signal,.

Turbino-Driven AFW Pump 24 tripped on mechanical overspood. The control-room operators opened the cross-connect valvos to/ allow the motor-driven

AFW pumps to supply feodwater' flow to Steam Generator-2D._At 3

31 p.m.,_a ctort was attempted on the startup feedwater pump, but~the pump tripped

-cgnin on high lubo oil filter differential pressuro. Emergency boration of the reactor coolant system was initiated because of the potential;of a 300s of shutdown' margin (end of core life and xenon considerations).

Approximately 3500 gallons of boric acid was. injected into the reactor from the boric acid storage tanks.

Ths Unit 2 reactor was stabilized in Mode 3-(Hot Standby) following the trip and is currently still in Mo'de 3. The overspeed trip device was.

lrOcot on Turbine-Driven AFW Pump 24 but the pump has not been started as /.

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of this timo. The lubo oil is in the process of being changed out on Startup Foodwater Pump 24. Steam Generator Foodwater Pump 21 bearing inspoction and rework is also scheduled to be completed prior to returning the pump to service.

At the timo of the Unit 2 trip, the licensoo was-troubleshooting the Unit 1 turbino- driven AFW pump, which was declared inoperablo on February 1, 1993. On December 27, 1992, January 28, 1993, and February 1, 1993, this pump also tripped on overspeed following an initial start of the pump.

R2gion IV was conducting a special inspection of this issuo~as well as other turbino-driven auxiliary foodwater pump problems that woro idontified during a recently completed Operational Sofoty Toam

Inspection. The licensoo believes that they havo datormined the cause of the Unit 1 pump overspood trips to be the result of water accumulation-in

'tho turbino casing. The sourco of water is suspected to be condensed.

ctorm that is leaking by the seats of the turbine trip and throttle valvo. The water was unable to drain through tho turbino casing drain lines because of blockago of the drain 11nos by accumulated sand. The

courco of the sand is believed to be from sandblasting of the containmont .

walls which occurred about 3 years ago. The 11censoo_was unable to ,

cuccessfully test the pump and declaro it operable prior to the expiration of the Technical Specification allowed outage time.

An Augmented Inspection Team (AIT), consisting of members from Region IV cnd one member each from the offico for Analysis and Evaluation.of Oporational Data and the Office of Nuclear Roactor Regulation will be 1dispatchod lator today to jnvestigate the causes of multiplo turbine-driven AFW pump overspood events that have boon experienced

'during the past soveral wooks.

The NRC w111 issue an announcement regarding the AIT. -

The state of Texas has been informed.

I Region IV received notification of this occurrence'by telephono.from tho

'NRC Operations Contor at 5150 p.m. (EST) on February 3, 1993. Region IV has. informed the EDO, NRR, and PA.

-This information has. boon confirmed with a licensee representativo.

~ Contacts A. T. Howell (817)860-8100 L

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