ML20085G836

AO BFAO-50-260/7422W:on 741030,rod Sequence Control Sys Operability Not Verified Before Decrease Below 20% Power. Caused by Recirculation Pumps Run Back Due to Low Feedwater Flow Switch Actuating Prematurely

ML20085G836
Person / Time
Site:	Browns Ferry
Issue date:	11/07/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Case E US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085G837	List: ML20085G836 ML20085G839
References
NUDOCS 8308290423
Download: ML20085G836 (2)

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ABNORISL OCCURRCCE REPORT Report No.: BFAO-50-260/7422W 3 Report Date: November 7, 1974 .

Occurrence Ihte: October 30, 1974 Facility: Browns Ferry Nuclear Plant unit 2 Identification of Occurrence .

Failure to verify RSCS operability before decreasing belou 20-percent rated power.

Conditions Prior to Occurrence Reactor power was at 26 percent during startup testing.

Description of Occurrence During the performance of recirculation system startup test, cavitational scarch phase, the reactor power was lowered to 26 percent. At this point, the lor feed-water flow switch caused the recirculation pumps to prematurely run back; cnd reactor pcuer dropped to 17 percent. Tne runback occurred before performin; the surveillance test to verify RSCS operabilit'/ . Technical specification h.3.3.3.

requires verifiertion of the capability of the rod sequence control systen to properly function before attaining 20-percent rated power when decreasing power.

Designation of Antarant Cause of Occurrence The lov feedwater ficw switch actuating prematurely caused the reciret.lation pu=ps to run back, thereby lowering reactor power.

Analysis of Occurrence The reactor power decreased from 26- to 17-percent rated power without the RSCS having been functionally tested. The control rod pattern required for RSCS had been achieved but not tested at the time the runback occurred, and the RSCS did enforce at the proper power level during the power reduction. - Recirculation flow uns increased to restore power to greater than 20 percent. There un no equipnent Wanction or operator error. Tnere were no adverse effects to the public health or safety as a result of this occurrence.

s Corrective Action The low feedwater flow switch setpoint has been set to operate at 22-percent rated power.- In addition, the RSCS setpoint has been raised to give more cargin between the RSCS enforcement and the recirculation pump runback.

Failure Data None 8308290423 741107 PDR S ADOCK 0500026f pp- .

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e, r h ara Mr. Edcon G. Case . M i,n' (9'j s

Acting Director of Licensing /

Office of Regulation f){n'hV U.S. Atonic Enercr Cor ission Washington, DC 20545

Dear Mr. Case:

TEI!!IESSEE V/,TA'"? IJJTHORITI - BROICS FFRRY NUCLEAR PIAI!T UIIIT 2 -

DCCIET I!O. 50-260 - FACILIT" OPERATING LICE'ISE DPR ABHOR'ML OCCURFJJiCEREPORTBFAO-50-260/7h22W The enclored report is T,o provide details concerning failure to verify RSCS operability before decreasing below 20-percent rated power and is subnitted in accordance with lippendix A to RcGulatory .

Guide 1.16, hevision 1, October 1973 This event occurred on "'

Erowns Ferry I!uclear Plant unit 2 on October 30, 1974.

Very truly yours, TEI"IESSEE VALLEY AUTiiORITf

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E. F. Thomas p Director of Power Production Enclosure CC (Enclosure):

Mr. Hornan C. Ibseley, Director Region II Regulatory Operations Office, USAEC 230 Peachtree Street,1:W., Suite 818 Atlanta, Geor6 1a 30303 11535 w

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