ML19350E492

Updated LER 80-050/03X-4:on 800717,steam Driven Emergency Feedwater pump,2P7A,turbine driver,2K3,tripped on Overspeed Following Manual Start.Caused by Design Deficiency.Governor Valve Control Modified

ML19350E492
Person / Time
Site:	Arkansas Nuclear
Issue date:	06/19/1981
From:	Shively C ARKANSAS POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19350E481	List: ML19350E480 ML19350E483 ML19350E487 ML19350E490 ML19350E491 ML19350E492
References
LER-80-050-03X, LER-80-50-3X, NUDOCS 8106230169
Download: ML19350E492 (3)

Text

.

REVISE 0 REPORT - PREVIOUS REPORT DATE 11/7/80 9 seRC f ORM 3s4 U.S. AduCLE AR REGULATORY COMMIS&l0*e 1.10ENSES EVENT REPORT EXHIBIT A (PLE ASE PRIPdT OR TYPE ALL REQUtRED INFORMATIONI CONTROL BLOCK: , l l l l l 1 .lh 8

l9 AIRL.CENstl lAlNl0lJ.g)[$0 cod 4 8 l0 l - 10 LtCGNst l0 l 0jNUM,(R 0l 0 l- l 0 l0M lg 3l1 l LKkNSE 1l1 }tv,4 1lglJO clAI 68gg bl CON"1 L% Lt.j@l015' p 10 l Oj31618 l@l 60 Gl DQCatrN(,wege 68 017 59 flEvtNT 17 oaygI B 10 l@l 01 6111

2. FS 9181180l@

HE,oMi o AT E EVENT DESCRIPflON AND PROSA8LE CONSEQUENCES h o 2 IDurino Mode 1 operation, the Steam Driven Emergency Feedwater (EFW) Pump, i o l?p7A turhino drivor. WL trinned nn nvorspond on the followino dates: I l][E) 17/17/80, 8/4/80, and 10/14/80. The electric driven EFW Pump, 2P78 and as-1

~

o 5 ise:iated valves were verified operable. This occurrence is similar to I o . ILER's50-36fs/7S-032,79-055, 79-072,79-081, 79-104,80-022, 80-030, 80- ,

I 8 In E and related to 80-039. Reportable per T.S. 6.9.1.9.b. I lola i i I

'E't" *[*! '

su 5^

• 8 I HIH;l@ h@ s' bet @ l Tl$='ll'l3ac lN i g {,$.g @U3eg N'

@,q.;...oIv.~,,[..

u

" if.?"c,'0 "a"['" "l' "

I 810 i L,-J I Q 510 I ld 10 13i L)LJ L-j [4J 2% 27 2 2 26 2F 78 19 JO at >J TAs N A ,o (fpf,LA T M i Houns s .T D ,04 L R U.h .ACTURER

[IJ@l.LJ@ LZJ@ l 010 l 01 d L.,rtj@ gj@ IT I 11417 I@

a > >> L.IJ@

2 v .. L.Y_J@

. n .. ,,

, CAVSE DESCRIPTION AND CORRECflVE ACTIONS 27

[_TTg] ICause of the EFW turbine overspeed trips was determined to be design re ,

frTr1 lated. Modifications to the governor valve control optimized governor i i 7 1 valve resoonse to speed sianals. A testino prooram verified EFW turbine i

, , i reliability. See attached for further information. ,

EE) i I

N,%s' . o. a o,sco sco,, c,o, i s LEJ@ l 110 l 0"l@l" Nk' ta si.,vsl @ J"fd"??.%[k gl Control Room EdYcation@ l can,.1 " " a a

' .!n ,,, ,y

,u.s.o o, maise toc.,,o,.o,,,ni.sc@

i o [Zj @ [Zj @l NA . ov~r o, .crivin @ l l NA l

' ' ' " a a

...s ~a ..os,'J,.s uo.o. . 1,n om..1,o @

i i 10101 Ol@[Z J@[_NA "

l l

' n so.~d'. ;u'a'ics a  !

i a e.... o.sc.....

NA 101 010l@}' l a

'os,s,o, on,ce[ o,"osaciurvg i o

[1)@l NA l NRc use oNov 2 o , so,'"@o l NA'sc.,,rio @ 1 l;lllg,;;j;;)

NAufOPPREPARER Chris N. Shively ,, 501/968-2519 8106230U/t

Page 1 of 2 ATTACHMENT TO LER 50-368/80-050/03x-4 Investigation in6 cated that the overspeed trips always occurred during the initial speed transient. .The turbine governor valve position has been visually observed either to have never moved during the transient or to have begun to move only at about the same time as the turbine speed reached the overspeed trip setpoint. Unsuccessful attempts to start the turbine could usually be followed by successful attempts The likelihood of producing an overspeed trip with a rapid start was seen to be time related. The longer the time span between successive starts, the greater the likelihood of an overspeed trip.

Initially, condensate in the steam line feeding the turbine was con-sidered to be the probable cause for the overspeed trips. Steam traps were added to the low points 'n the-line, but the problem persisted.

Vendor representatives from Terry Turbine and Woodward Governor were brought on site. Preventive Maintenance was performed, adjustments were made, and questionable components were replaced. Subsequent testing resulted in an overspeed trip.

Plant Engir.eering personnel reduced the idle speed setting from 1100 RPM to 800 RPM, delayed the initiation of the ramp signal by six seconds, and

, reduced the governor valve travel f rom 7/8" to 5/8". The testing program was restarted, initially starting' the EFW turbine at one hour intervals, and doubling the interval for each successive start. The turbine started successfully until the elapsed time between starts reached 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, at which time it tripped on overspeed. Subsequent testing indicated that these adjustments enhanced the governor valve response.

An outside consultant was contacted to investigate the overspeed trip problem and make recommendations. Their conclusion was that a design j modification was required to increase the margin to overspeed trip on startup of the EFW pump. The following modifications were made based ,

on the consultant's recommendations: '

(1) Replace the governor actuator hydraulic fluid sump with one of like design as a preventive measure.

(2) Increase tubing internal size (from existing 0.065" wall thickness tubing to 0.035" thickness tubing)

. from governor actuator (electric to hydaulic signal convertor) to the remote Servo (governor valve oper-ator) which effectively reduced hydraulic flow re-sistance.

(3) Install a sight glass on the hydraulic sump to allow

! monitoring of oil level in the sump during and be-tween startups.

I i

ATTACHMENT TO LER 50-368/80-050/03-4' Pags 2 of 2 A new testing program was begun. Elapsed time between starts was initially one day. Two starts were made at each interval and then the time was in-creased. The. test program was completed when two starts at one month

' intervals were successfully completed. Test results indicate that the slow response of the governor valve was no longer noted. The amount of overshoot, which is the highest RPM reached by the turbine during the initial speed transient, was no longer seen to increase as time intervals increased.

The EFW turbine driver governor responsiveness is considered to be optimum.

Through surveillanc' testing and preventive maintenance, this condition

, should be acceptably maintained.

4 4

)

l i

e i

i

(

l

,_ .c., , ,_- _ - , . , , . - - - . - - -.y,