ML20147E884

/99X-0 on 780914:shortly After Reactor Trip an Inadvertent Safety Injection Occurred from a False Delta P Steam Pressure Signal,Generated from Shock of Feedwater Hammer.No Damage Resulted from Safety Injection

ML20147E884
Person / Time
Site:	Zion File:ZionSolutions icon.png
Issue date:	12/11/1978
From:	Reiss J COMMONWEALTH EDISON CO.
To:
Shared Package
ML20147E868	List: ML20147E864 ML20147E884
References
LER-78-095-99X, LER-78-95-99X, NUDOCS 7812210239
Download: ML20147E884 (3)

Text

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I LICENSEE EVENT REPORT i 1

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7' .B 00 bl DOCKET NUMBEH LS 69 - - / E NT.D AT E 74 lb HEPORT DA1 E UU EVENT DESCRIPTION AND PROBADLE CONSEQUENCES h 10121[_12 minutes after a reactor tript_an inadvertant safety iniection l l

[ o i :(1 l occurred form a false dP stm pressure signal. T.S.3.3.2.F.3 requires a j l0 l4 l l 90~ day report of the event. Visual inspection indicated no damage as aj

[O isl l result of-the SI. The health and safety of the public were,not l'_

[O laj j jeopardized. Mine (9) previous water hammer SI's have o curred on 4 l0l7ll both units. l 1 O I H I 1. I 7 8 0 80 DE . CODE S BCO E COMPONENT CODE SUBC dE SU E 10101 7 b I d Fl@ l xl@ Iz l@ l zl zl zi zlz I z l@ I z i@ l zl@

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~ 4 ATTACHMENT.TO LER No. 78-9 5/ 9 9LX-0'

' COMMONWEALTH EDISON CO. q l

' ZION GENERATING STATION- )

.1 50-295

. Description of. Event.

. At 0817, on September 14, 1978 , while operating at'63%-

)j steady state power,.the Unit.1 turbine tripped which resulted in a_ reactor trip. ' Three. aux feedwaterLpumps.were. started and were .

feedingrat less than 150 gpm to each steam generator. AtLO829 )

hours, a. safety injection occurred for "Steamline high 'P"  !

signal on loops luk and IC. AtLthe timeLof'the safety. injection, j chart recorders showed'a1 spike on theifeed flow indicators on '

all-four steam generators.with the. spike on 1D steam generator

-chart being twice'the magnitude of the other three. In addition, an operator witnessed movement:of'the feedwater piping in the  :*

steam pipe tunnel. 'The cause for .the safety injection,is. thus

' determined to be.a.. water hammer on the'lD feedwater line. The shock produced by'the water hammer spiked loops B & D' steam line t

, pressure transmitters which are mounted in.near proximity to one l another. Experience has'shown that a sudden shock will cause j these transmitters to spike high. Thus, the A and C loops sensed a false "high .P" signal initiating safety injection.

Consequences of Occurrence .

J A visual inspection inside the Unit l' containment and feed- j water piping; indicated that no damage occurred as'a result of >a the safety injection or water hammer. .The magnitude of the water hammer shock appears to have been' low because evidence of the water hammer (broken insulation 'around the pipes, etc) was not present. The' effects of the~ thermal transient on the safety 1 injection ' nozzles.were evaluated, 'and it was concluded that they 7 were of minimal consequence. The integrity of the reactor coolant system remained intact. The health and safety of the public were not affected.  ;

Cause of Occurrence Past experience'andl technical bulletins indicate test steam.

generator origin water hammers occur when the feed ring is.being

-recovered with a high^ aux. feed flow. This water hammer occurred.

before theLfeed ring:was'being recovered and with_.non-high flow.

Data is- not. available to indicate whether the origin of the hammer Dwas in the steam' generator or from the turbine building.

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Corrective-Action A program of physical monitoring of the feedwater piping to the steam generators is in effect on Zion Unit 2 using accelero-meters in an attempt to gather data on water hammer effects.

However, no data is available at this time since there have been no recorded safety injections in Unit 2 since installation of the accelerometers. Unit 2 was chosen because of the past history of water- hammers on that unit.

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