ML20155E582

PNO-OSP-88-010:on 880608,reactor Tripped During Startup When Operators Attempted to Place Main Feed Pumps in Automatic Speed Control.Caused by Operator Error.Prior to Resumption of Startup Activities,Util Will Meet NRC to Discuss Trips

ML20155E582
Person / Time
Site:	Sequoyah
Issue date:	06/09/1988
From:	Richardson S NRC OFFICE OF SPECIAL PROJECTS
To:
References
PNO-OSP-88-010, PNO-OSP-88-10, NUDOCS 8806160154
Download: ML20155E582 (2)

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June 9, 1988 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PHO-0SP-88-010 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 all that is known by the OSP staff on this date.

FACILITY: Tennessee Valley Authority Licensee Emergency Sequoyah Unit 2 Classification:

Docket No. 50-328 Notification of Unusual Soduy-Daisy, Tennessee Event Alert Site Area Emergency General Emergency X Not Applicable

SUBJECT:

SEQUOYAH UNIT 2 REACT 0P TRIPS At 1319 EDT on June 8, Unit 2 tripped from 15% power on a 10-1o steam generator level in SG #2. The trip occurred during startup when the operators attempted to place the main feed pumps in automatic speed control. Operator error was determined to be the root cause of the trip. The feed pump speed controller was placed in automatic before the contr 'ler had stabilized properly, which caused the feed pump speed to be reduced to minimum. This in turn resulted in feed pressure being reduced below steam generator pressure and a subsequent loss of feed flow. Attempts to recover from this condition initiated an oscillatory feed flow and steam generator level transient which subsequently resulted in the reactor trip. All systems functioned as required, and the plant was brought to Hot Standby (Mode 3).

Unit 2 was returned to critical at 2300 on June 8. At 0512 EDT on June 9, the Unit again tripped from 17% power on a 10-10 steam generator level in SG #2.

The trip occurred when SG level oscilletions began while the feed control valves were still in manual. The oscillations were caused by feedwater heater strings "A" and "B" isolating due to heater level control probler.s. When the heaters isolated, the feed pump began experiencing suction pressure changes, and this resulted in a temporary loss of feed flow. Again, attempts to recover from this condition initiated a feedwater flow and steam generator level transient which subseouently resulted in the reactor trip. There were no anomalies associated with the trip, and all systems functioned as required. The plant is presently in Mode 3.

OSP has notified TVA by letter dated June 9, 1988, that prior to resumption of startup activities, a meeting must be held between the senior management of the NRC and TVA to discuss each of the five reactor trips that have occurred during Sequoyah's restart effort, the causet of the trips, and the adequacy of corrective actions taken. This meeting will be held at White Flint when TVA determines it is ready to discuss the events, probably during the week of June 13, 1988.

CONTACT: S. Richardson (301) 492-3289 Distribution: see next page D

l 9806160154 880609 PDR I&E PNO-OSP-88-010 DCn ___

l PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PN0-0SP-88-010 DISTRIBUTION 5520: Mail:

thiTman Zech - INRC1718/Leadop XGI Commissioner Roberts - 1NRC1718/Leadop DCS Commissioner Bernthal - INRC1718/Leadop 01A-MNBB-8607 Commissioner Carr - INRC1718/Leadop 01 - 3E4-DLewis Commissioner Rogers - INRC1718/Leadop OSP SECY - INRC1718/Leadop CA - INRC1718/Leadop PA - INRC02/Leadop

, ARM - NRCRM/ Brown Reatonal Offices A0ED - NRCRMPN Region I - Rl/Leadop Hqs Oper. Office - NRCRMPN Region II - RII/Leadop NRR - INRC1112/Berean Sequoyah Resident Inspector OE - INRC0708/ Summers Licensee: TVA NMSS - INRC0506/Leadop Region III - RIII/Leadop OGC - INRC1516/Leadop Region IV - RIV/Leadop SP - 1NRC0304/SGindes Region V - RV/Loadop E00 - INRC1718/Leadop l DEORO - INRC1718/Leadop GPA - INRC1718/Leadop l

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