PNO-III-80-166, on 800903,unit Tripped from 93% Power Due to Low Steam Generator Level,Caused by Feedwater Pump Trip. Water Hammer Occurred While Steam Generator Level Was Below Feed Ring Causing Safety Injection Actuation

PNO-III-80-166:on 800903,unit Tripped from 93% Power Due to Low Steam Generator Level,Caused by Feedwater Pump Trip. Water Hammer Occurred While Steam Generator Level Was Below Feed Ring Causing Safety Injection Actuation

ML20148D712
Person / Time
Site:	Zion File:ZionSolutions icon.png
Issue date:	09/03/1980
From:	Heisman R, Kohler J, Spessard R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-80-166, NUDOCS 8010090255
Download: ML20148D712 (2)

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. A- PkEl.IMINARY NOTIFICATION

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. Date

• September 3,1980 PRELIMINARY NOTIFICAT10N OF EVENT OR UNUSUAL OCCURENCE..-PNO-III-80 166 Page 1 of 2 This preliminary notification constitutes EARLY notice of events of P05SI8lLE safety or public interest significance. The infonnation presented is as initially received without verification or evaluation and is basically all

,th,at is _kn'own by IE staff a_s _of this date.

Facilit.y: Commonwealth Edison Contpany Zion Unit 2 Docket No. 50-304 Zion IL Subj ect: REACIOR TRIP - FEEDWATER HA!CER/ SAFE 1Y INJECTION At approximately- 5:40 a.m. on 9/3/80, Zis.i Unit _2 tripped from 93% reactor power due to low secam generator level. The low level condition was caused by a trip of the 28 steam driven feudwater pumo. (The plant hts three feedwater pumps, two steam and one electric. driven.) At the time of the f med pump trip, the unit was operating with one steata and one electri.. pump. The third pump was out of service.

At the moment when th e la fcuduster pumu tripped, the oper. tor immcdiately ramped the EHC system down from 93% to below 50% power in an ef f ort to "save the unit."

(Steam productior above 50% power requires two f eedwater pumps Ir. order to maintain acceptat le steam generator level.) 'Ihis operator action caused the steam dumps La open and T average to decreasc.

operator action was subsequently unsucccasful, and the unit tripped on Tru neerg.:

generator level . Auxiliary feedwater started as designed (three pumps) and initially injected rt about 270 gpm. The flow rate was higher than expected and the operator throttled back aux feed flow to 220gpm as required proceduralty.

The pre tedure requires furcher throttling of auxiliary feed finw so narrow range steam generator level is recovered. Norma?ly, recovery of narrow range -level takes about two hours and the additional throttling in a precaution ageinst water hammer in the feed ring.

Well, bef ore the recovery of narrow range etcam generator icvel, a thunderu noinc was heard, followed by the actuation of the steam line 100 psi a P safety injection signal and an automatic saf ety injection (SI) . All safety systern operated as designen. SI was terminated by operator action when all primary,wecondary and radiation monitoring instrumentation ehewed normal values, i.e. , no unexpceted lenk-age van evident. The ST is believed to have been caused by a water hammer occurring while steam generator level was below the feed ring. Based on review of the steam generator feedwater flow strip charts and the indicated magnitudn of the iced-water spikes, the watcr hamnet occurred f a the B steam loop.

As a result of previous water haamers, Zion station has committed to the ".T-TUBE" modification on all steam generators, and, presently the C and D rencrators on Unit 2 have heer modified. The B generator doen not have this modificnrinn. However, it is important to acte that the 7-TUBE modification was installed to preclude water hammering in the f eed rin6 As indicated above, this sater hammer oscurred when the steam generator level was well below the feed ring. This in the first water hammer on Unit 2 in approximately 2 years.

PRELIMINARY NOTIFICATION THIS DOCUMENT CONTAINS POOR QUAUTY PAGES 8010090255 ,

PRELIMINARY N0ilflCATION Pege 2 of 2 PNO-!!!-80 f66 i

Unit 2 is being maintained in a stable, hot shutdown condition and is recovering i I

from the SI. No piping outside containment was damaged, and-inspections are

! underway inside containment. Additionally, the licensee plans to repair the B feedwater pump haf ore going back to power. The duration of the shutdown is presently unknown.

Unit 1 oparnted at 100% power throughout the Unit 2 trip.

The FRC residehi inspectors have reviewed the details of this event and thr. n licensee's actions / plans in accordance with program requirements and this wview is continuing.

J Neither the if cennee nor RIII (Chicago) are planning te issue a press release.

The State of Illinois is being notified.

The licenses reported this matter to the liRC via the Red Phone within one hour of the trip. Additional informaLlon was obtained frera the Resident Inspectors '

and in current as of nonn September 3,1980.

contact:

\:K( ') ~

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J.E.hh'ler, 312/746-23133 R. L. Rheard, 312/932-2547; R. F. lleishman, 312/932/2540 4

Distribution: Transmitted H St. -

Chairman Ahearne Comi~ssioner Hendrie S. J. _ Chilk SECY C. C. Kamerer, CA i Comissioner Gilinsky Comissioner Bradford ACRS (For Distribution)

P. Bldg. IE:XOOS (IE:HQ Cist.: i Transmitted: MN88 W. J. Dircks, EDO H. R. Denton, NRR R. H. Vollmer. NRR Landow (6 min /page) .

C. Michelson, AE00 J. J. Fouchard, PA R. J. Mattson, NRR J. J. Cummings OIA  ;

N. H. Haller. MPA D. F. Ross, NRR D. Eisenhut, NRR MAIL {

C. W. ? D inogue, 50 i H. K. Nrr, Ospapar ELD S. H. Hanauer IE:X005 i Willste Bldg. Document Mgt. Br. (For PDR/LP: '

J. G. Davis, Th T l Regional Offices T. E. Murley, RES ,

PRELIMINARY NOTIFICATION l

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