ML20085L931

AO BFAO-7414W:on 740311,during Planned Load Rejection Test from 75% Power,Hpci Actuated Automatically W/Pressure 100 Psi Above Normal.Cause Unknown.Hpci Response During Test Will Be Closely Monitored

ML20085L931
Person / Time
Site:	Browns Ferry
Issue date:	03/21/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085L932	List: ML20085L931 ML20085L936
References
AO-BFAO-7414W, NUDOCS 8311070025
Download: ML20085L931 (3)

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l-TENNESSEE VALLL: AUTHO AITY MD CHATTANOOGA, TENNESSEE i i Q

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Mr. John F. O' Leary, Director s 1.i 2 Y,1fpc . .

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Directorate of Licensing Office of Regulation

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Dear Mr. O' Leary:

i TENIiESSES VALLEY AUTEORITY - BRO.d!S FERRY NUCLEAR PLANT UNIT 1 -

DOCKST I:0. 50-259 -- FACILITY OPERATING LICDISE DPR AMORMAL '

OCCURREECE REFOr *A0-7414W i

The enclosed report is to provide details concerning possible I meloperation of SCI which occurred on Browns Ferry IIuclear Plut  ;

unit 1'on llarch 11, 1974, and is submitted in accordence with i Appendix A to Regulatory Guide 1.16, Revision 1, October 1973.

Very truly yours, ,

TEIETESSEE VALLEY AUTHORITY

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E. F. Thonas -l

Director of Power Production i '

Enclosure l CC (Enclosure):

Mr. Horman C. I'oceley, Director Region II Regulator / Operations Office, USAEC i 230 Peachtree Street,17.1.,- Suite 818 Atlanta, Georgia .30303 l 1

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ABNORMAL OCCURRENCE REFORT Report No.: BFAO-7414W Report Date: l' arch 21,1974 ,

Occurrence Date: March 11, 1974 Facility: Brouns Ferry nuclear Plant unit 1 Identification of Occurrence Possible caloperation of h7CI.

Conditions Prior to Occurrence i

l A plcnned load rejection test from the 75-percent power level plateau was in progrecs.

Description of Occurrence In the review of data collected concerning the load rejection test, conflict l exists as to the events which transpired concerning the F2CI. T-adiately l following test initiation, the main turbine control cnd step valves chut end l the reactor scra ed. Reactor unter level decreased rapidly because of the sudden pressure increase; cnd, at approximately eight seconds after the initiating event, a low water level was reached causing the 1*SIV's to isolate and the FICI to start. At approximately 15 seconds after initiation, a peak pressure between 1,070 end 1,080 pcis wa: reached. Reactor water level had returned to above its norcal level within 30 seconds. At approximately 5 minutes and 30 seconds in the trcnsient with the water level at 52", the operator manually opened a relief valve to decrease pressure. The reactor' water level swelled above the 54" h7CI trip point and recained there sfnile the relief valve was opened--approximately 1 minute. Conflict exists as to HPCI operation during this interval. The operator logged that the F2CI tripped on overspeed five nin=es after the rmin turbine trip. This cannot be substantiated by recorder charts of water level cnd HPCI injection flow.

It is believed that the operator actucaly observed.the F2CI high water level trip signal which accompanied the manual relief valve cperation.' Uu=erous individuals observed the F2CI ctart at the be5 nning 1 of the transient when

! a reactor water level depression uns experienced. One plant electrical

engineer states that he sau the HPCI isolate because of high steam flow l

within seconds of its initiation. The control room operator, who had nany l

events recuiring his attention, states that coon after the low reactor water level recovered, he set the HPCI controller for mini-m flow but 'did net actun11y observe FTCI running. The hTCI injection flow recording chcrt chews a flow spike of moderate intensity near the beginning of the transient followed by a 15-minute period of ::ero flow, and then a period of flow higher then the initial spike of a duration of perhaps five minutes. _ This later spike occurred when HPCI was =anually operated.

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Desirmation of Annerent Cause of Occurrence The recorded data and the statc=ent of one plant engineer that he saw the equipment trip on high steam flow is cause for concern. From the data co11ceted during the transient, it is highly irprobable that EPCI performance .

during this test will ever be known with certainty. The purpose of the test was not to observe EPCI performance, and its action was only of peripheral interest. Tne HPCI has previously operated correctly when started with nor=al reactor pressure. This is the first tire EPCI has ever been actuated automatically with pressure appror' tely 100 psi above normal. Because there is a possibility that starting the HPCI with abnormally high pressure will in fact result in an excessive stesn flow above the trip setpoint, this must be investigated further.

The operator logged that ECI tripped on overspeed five minutes after the main turbine trip. Tnis is high];y unlikely and cannot be substantiated by recorder charts of reactor water level and EPCI injection flow. It is believed that. at approximately five ni .utes after the main turbine trip, the hTCI was not operating; but, if it were, it would have tripped on the high water level which acco panied the ra.nual relief valve actuation.

Analysis of Occurrence The reactor was never jeopardized durirq this test by EPCI performance. Reactor water levels were such that injection was never regaired, and the EPCI and RCIC were available for canual operation if regaired.

Corrective Action Conditions similar to those which existed at the time of irterest cannot be duplicated during normal reactor operation. The plant startup test program requires a s4-i'ar load rejection test to be conducted from the 80-percent power level. EPCI response during this test will be closely monitored, and corrective action will be based upon the results found at thet time.

Failure Data Investigation subsequent to abnor=al occurrence BFAO-7338 has shoun that a high steen flow EPCI isolation will occur if the EPCI auxiliary oil pu=p is placed in operation before the EPCI stcan supply valve is opened. This investigation has also shown that EPCI isolation does not occur on automatic actuation of the EPCI system if the auxiliary oil purp is started si=1tencously with the open4 g of the stean supply valve. These observations can be explained by analycing the operation of the EPCI steam turbine control system. The control systen operates such that, when oil pressure is made available to the control '

systen (starting the auxiliary oil purp), the system will open the turbine control valve even though the turbine is not running. With the turbine control valve open, the initial surge of steca, when the steca supply valve is open, is large enough to initiate EPCI steen flow isolation. The steam flow isolation design setpoint thus cppears to be targina13,y low. After careful consideration of potential pipe break problems as well as EPCI startup transients, both TVA cnd GE design have previously reco ended not increasing the high flow d/P switch

' setting so as to give maxi =n protection for all high energy pipe breaks. A calibration check of EPCI stcon flow isolation instrumentation was performed following this occurrence and instrument calibration was found to be within acceptable limits.

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