ML19325D247

LER 89-012-01:on 890502,main Feedwater Isolation Valve to Steam Generator a Found Inoperable Due to Improperly Set Torque Switch.Caused by Inadequate Program for Maint of Motor Operated Valves.Torque Switches reset.W/891013 Ltr

ML19325D247
Person / Time
Site:	Fort Calhoun
Issue date:	10/13/1989
From:	Hollingsed M, Morris K OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-012, LER-89-12, LIC-89-863, NUDOCS 8910190284
Download: ML19325D247 (6)

Text

. ., . . .

.o:

J Omaha Public Power Olstrict )

1623 Harney Omaha, Nebraska 68102 2247 i 402/536 4000 ]

October 13, 1989 i LIC-89 863 l I

U. S. Nuclear Regulatory Commission l Attn: Document Control Desk .

Mail Station P1-137 l Washington, DC 20555 j

Reference:

1. Docket No. 50 285  !

2.- Licensee Event Report 89-012, June 2, 1989 (LIC-89 536)  ;

Gentlemen:

SUBJECT:

Licensee Event Report 89 012, Revision 1 for the Fort Calhoun l Station i Please find attached Licensee Event Report 89 012, Revision 1 dated October 13,  !

1989. The revised information includes the results of an evaluation of  !

motor-operated valve operator parameters, and the status of the revised i motor operated valve maintenance program. This information is provided as  ;

committed to in Reference 2 and is noted by vertical bars in the margin. This >

report is being submitted per requirements of 10 CFR 50.73(a)(2)(ii)(B).  !

Sincerely, l l

. . is t vision Manager <

Nuclear Operations l KJM/pje c: R. D. Martin, NRC Regional Administrator A. Bournia, NRC Project Manager P. H. Harrell, NRC Senior Resident Inspector INPO Records Center 4

American Nuclear Insurers

$s j l

89101902G4 891013 FDR ADOCK 05000285 o PDC ds s:24 tmaioumen Iou oppmiunnu

. o,c N== ses v4 wucten uov64toay oo.mun.o= ,,,,,,,,c,,,,,,,,,,,,  ;

earmis usos i N u Teow C at to e. O tti 60 ms 8 maamb

, UCENSEE EVENT REPORT (LER) go,i,=,v4a40,*g= ggt,gry,vga,4 ag i "f",7"JJ "n* ,

of MahA06wtNTDuoAN.e" A'.m",1;?'hE*" 07,1?

0ET WADMINGTON.OC 20603. l

. .un ni ooc.e, vueea ai . - - . .

Fort Calhoun Station Unit No. 1 o 15 l 0 Io l o 12 I gi s t jorl015 TITLE 4.) [

Feedwater Valve HCV-1386 inoperable Due To Maintenance Proaram Deficiency evem a n . n . u . .., .. n o.n i,, ov t enciuvies .=vo6v o .i MOhfM Dat Vlam vtam "80 '46 may y9 9,, pay gg , ..cigeg, hawas pocatt Nuestemisi N o15101010 1 ii

~ ~

Ol5 Ol 2 8 9 8l9 0l 1l 2 0l1 1l 0 1l3 8l 9 otsfolotel l I

,,,,,,,,,, vae ...on . .u irn o eva.u.c to v ..ou. .w n o, io c. i fe ., .. .. , n1.

1 m semi n .ni.i m n.H:H.i nmi g _

m nHii w n .ini u n =H.i n.,ii.i nei Of 110 = = inHai eo mi.=>

u ni.H H .

_ g y, g g. .

30.Eti.H1Hel te 136.HRHit 00 734.HtH.eslHAl Jesas 30.mt.H1 Heel 90 734.H3Hei 90 734.H38teamHDI M .ISt.H1 H.6 90 734.H3Huli 90 736.lGHai LICSNDtl Co.tT ACT FoA TMis Lim till Nawl ittarucht vueen ,

anta copt  !

Mark Hollinased. Shift Technical Advisor 41012 513131 16 in i 111 co-a n . t ... .c., co-o . . .itvu .c. .. . .o. n.on n3i CAunt sv$1iv "'"y' ' C ' ' couPohlhi "'"y'g AC m a E COMP 0h t hf "k'o *'m8 CAVst systtw y 1 I I I I I l i I I I I I I  ;

I 1 l l I l l l l l ! I l I

.v,.o u.6 u,on e me,.o n.,

,,,,,,, ou- ..v v...

V45 fit ,.e c m e im.f rfte spea.sstio4 o.til No j l l

.=1..c,a,--...,....-,.,-.~n.,

i l

l At 1610 hours0.0186 days <br />0.447 hours <br />0.00266 weeks <br />6.12605e-4 months <br /> on May 2, 1989, plant management of Fort Calhoun Station ,

l determined that the main feedwater isolation valve to the "A" steam e l generator was inoperable due to an improperly set torque switch on the i valve's motor operator. The valve would not have closed completely before being tripped by the switch during certain accident conditions, and was therefore outside the design basis of the plant. At the time of

• the determination, the plant was operating at 10% power and >reparing to ,

go back on-line following a 3 day outage. In accordance witi 10 CFR 50.72(b)(1)(ii)(B),theNRCOperationsCenterwasnotifiedat1625 hours on the same day. This LER is submitted pursuant to 10 CFR 50.73(a)(2)(ii)(B).

l The cause of this event is an inadequate program for maintenance of Motor Operated Valves. The torque switches on this valve and on three I identical valve operators have been reset to ensure adequate closing i thrust is available. An extensively improved motor-operated valve

maintenance program plan has been approved and is being implemented. l l

1 er ~.,

t eine pones sena u s. souctsa; meevoavoav onesmesions UCENSEE EVENT CEPORT (LER)  ?@^."? *$Me'ALTa51'av%*M.' E.".'*9 i TEXT CONTINUATION f,n',A'$i$k'diAMIUL'J'MM'0*!IN O,

u o wa#,'..",Mi'Te n oi eur a e%*t:2PJevo.JR voorv.w W% oc m07.11 n

.u n J

. n,

&..u. .v . .,

t , . .,0 . , ,. .

{

u aa " CM. '*f.O Fort Calhoun Station Unit No. 1 o [s lo j o j o l 21815 Ol1 01 2 0F 015 819 Ol112 -

vent v- mamm

. ,mic, i

At'1610 hours0.0186 days <br />0.447 hours <br />0.00266 weeks <br />6.12605e-4 months <br /> on May 2, 1989, plant management of Fort Calhoun Station determined that HCV-1386, the main feedwater isolation valve to the "A" i steam generator, was inoperable. The valve was inoperable because of an l improperly set torque switch on the valve's motor operator. The valve receives a signal to close from the Steam Generator Isolation Signal (SGIS) during a main steam line break inside or outside containment to minimize the resultant overcooling of the reactor coolant system due to the excessive heat extraction. With the improper torque switch setting, i it was determined that the valve could not be closed completely during a main steam line break, a condition outside the design basis of the plant. The plant was at approximately 10% power when inoperability of HCV-1386 was determined.

In accordance with 10 CFR 50.72(b)(1)(ii)(B), the NRC Operations Center was notified at 1625 hours0.0188 days <br />0.451 hours <br />0.00269 weeks <br />6.183125e-4 months <br /> on the same day. This LER is submitted ,

F rsuant to 10 CFR 50.73(a)(2)(ii)(B). ,

Investigation into the torque switch settings had been initiated when it t was discovered on May 1, 1989, that two other non-safety related main feedwater isolation valves, HCV-1103 and HCV-1104, could not be closed from the control room. The plant was preparing to increase power and re-synchronize the generator to the grid following a 3 day outage to test i the performance of the turbine overspeed trip. An initial condition of .

the start-up procedure in use was that HCV-1103 and HCV-1104 be closed. s At that point, it was discovered that the valves could be opened, but not closed, from the control room. The investigation of tne failure of these i valves to close determined that the torque switches on the valve motor  :

operators had been set at 1, which corresponds to a .ctem thrust ranging from approximately 18,000 pounds for a non-lubricateu palve stem to 21,600 pounds for a well-lubricated stem. The minimum stem thrust .

required for a 1500 psi differential across the valves is 47,700 pounds.

The torque switches on HCV-1103 and HCV-1104 were reset to 2.75, which ,

corresponds to a stem thrust ranging from approximately 55,700 to 66,800 pounds (non-lubricated to well-lubricated stem).

It was then decided to check the torque switch settings on HCV-1386 and t HCV-1385, since these are identical type valves to HCV-1103 and HCV-1104, and are the primary feedwater isolation valves for the SGIS. HCV-1386 is the isolation valve downstream of HCV-1103 on the main feedwater header to the "A" steam generator, and HCV-1385 is the isolation valve downstream of HCV-1104 on the main feedwater header to the "B" steam generator. The minimum required stem thrust on these valves is also 47,700 pounds. The torque switch on HCV-1386 was found set at 1.75, teRC ,esm astA 4640)

. ,, u,,......-,-- -

. r.c m o =0.. -

i i

n, . . m.=

UCENSEE EVENT CEPORT (LER) Un'.'!?,A""cM *,'Mo"'C's/%W.h' ,T.".J.Q  !

" TEXT CONTINUATION  !?f'.'",E'4*.'if!",i .'.0f'.M!,'cW12 'u"WTf! }

T, ,J .".Jo F.!""iWi"/,A'M' 0 WAh&GEMth? AND 0J000 f.mA.M..?"432.l e

1. 0f 04. DC 20 ,

,ett4sfV 8 AA.4 41, DOCast seum,Da,t iti Lth teuestga sei ,Aet (si f

~. ae = t' :ea: .

i Fort Calhoun Station Unit No. 1 o is 1o lo Io 121815 81 9 -

01112 -

011 01 3 0F 0 15 vorm . e w wim i

which corresponds to a stem thrust of approximately 34,200 to 41,000 f pounds (non-lubricated to well-lubricated). The torque switch on '

HCV-1385 was found set at 2.5, corresponding to a stem thrust of approximately 50 300 to 60,300 pounds (non-lubricated to well-lubricated),,whichwasacceptable. The torque switches on both valves were then reset to 2.75 to ensure adequate closing thrust, as on HCV-1103 and NCV-1104. >

Allfourvalves(HCV-1103,1104,1385,and1386)involvedreceivesignals to close from the SGIS; however, HCV-1385 was cons'dered able to perform l' its design function since its torque switches were net high enough (i.e.,

2.5)toclosethevalveunderthedesignbasisdifferentialpressure.  ;

Following these discoveries, a review was performed of maintenance  ;

records of all other safety-related valves with motor operators in the '

plant. The results of this review indicated that each torque switch was correctly set to provide the required stem thrust.

On the following day, May 3, 1989, vendor equipment was connected to measure the actual stem thrust on the valves, and the torque switches were reset as shown:

Torque switch Measured Thrust at settina Toraue Switch Trio  ;

HCV-1103 2.5 77,808 pounds (lubricated stem) ,

HCV-1104 2.5 70,434 pounds (lubricatedstem) ,

HCV-1385 2.5 64,232 pounds (lubricatedstem)

HCV-1386 2.75 76,568 pounds (lubricatedstem)

The relationship between torque switch setting and stem thrust is dependent on variables such as spring pack condition, packing tightness, and stem lubrication. Stem thrust is the critical parameter of the two; therefore, torque switches are set after the desired stem thrust is verified by measurement. Normally when measuring the stem thrust, a load cell is attached to the top of the operator. This method of measurement requires that the operator have an upper thrust bearing to support the i

loads imposed by the testing. The Limitorque SMB 4T operators, used on I the valves noted previously, do not have the required upper thrust l bearing. Therefore, the stem thrust could not be measured on these l valves in the past using available test equipment, and the torque l switches could not be reliably set as part of routine valve maintenance.

l

=ac . .

-,- -.- - - -_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ~ _ _ _ _ _ _ - _ _ _

. u.. e6 . ..... . -

UCENSEE EVENT REPORT (LER) Ws!?,c*r"e@iNo!'So"".r'k*f%Y G=".'58

• TEXT CONTINUATION f0",i?.M!k'dN!3f"?'.W.'#','l2M'EUU i OP'.'t'l?".TJ!?.hD .J*

.a,'22 Dup 04f,m n?"4m.03.Mi'ei 0F M h 08 het aff **WOTON.DC30 {

P&cettf y ,s.est m DDCEti Numet A W Lea Nuns.4m top P.te (m

"'" " 2 ." "'2.n i Fort Calhoun Station Unit No. 1 o l5 l0 l0 l0 I pl gls . 81 9 O l 112 -

0l 1 0l a OF n 18; vu,u . anca.-m. m m 1

s Recently, testing equipment became available which measures stem thrust using a strain page attached to the stem, and does not require the ,

operator to have an upper thrust bearing. This equipment was used on May ,

3, 1989, when the torque switches were reset to their present settings.  ;

A review of maintenance and test records related to torque switch '

settings for Limitorque valve operators was conducted and the results were evaluated. The thrust measurements and/or torque switch settings I were compared with originelly specified minimums. This evaluation concluded that the operator settings ensured availability of adequate thrust for operability of the associated valves.

The cause of the incorrect torque switch settings is lack of an adequate MOV maintenance program, particularly the inability to measure stem thrust and properly set torque switches for SMB-4T operators. Because these operators can deliver enough torque to damage valves if improperly adjusted, maintenance emphasis in the past was on valve protection rather than insuring capabilities of valves to perform their intended function.

In this case, this emphasis probably resulted in low torque switch ,

settings. The settings were therefore not adequately controlled by the existing maintenance procedures.

An extensive MOV maintenance plan has been approved and is being implemented. The plan is designed to develop a data base of all MOV's, create training programs for engineering and craft personnel, perform baseline testing of all MOV's, procure necessary spare parts, and initiate preventive and predictive maintenance of all M0V's. When fully i implemented this new program will provide assurance that all plant M0V's ,

are properly tested, maintained, and adjusted, thereby assuring the operability of the valves. I i There are only 5 safety-related motor operated valves in the plant for which stem thrust had not been measured: HCV-1385 and HCV-1386, HCV-383-3 and HCV-383-4 (Containment Sump Isolation Valves), and HCV-308 (ChargingPumpDischargetoHPSIIsolationValve). HCV-383-3 and HCV-383-4 are closed during normal operations, and are opened only in the -

emergency condition of a loss of coolant accident, with a low level in the Safety Injection Refueling Water Tank, to supply the safety injection and containment spray pumps with water from the containment sump. These ,

butterfly valves are currently tested under the station Inservice Inspection Test Program. Any differential pressure across these valves during a design basis event will aid in the opening of the valves.

==c . . ,

+

q ,.,,,,

u.. . ... . , c i .. . m..

e- uCENSEE EVENT CEPORT ILER) '*'o'".^.'.'r%?""M".Mio' f,'.*Fo31/*.!?'"? Io'.".lO l

TEXT CONTINUATION F#.7.E"! .'fh!!a'"f'.U'.M^.'MP U;' L'EEEN O.f.t.~^.'..".'A=?.".Ai,',at=Mm.

o .oi. 1 .oe m t... otos oc men.&

W4tTV ts.t.t fl6 Docati s. Vest A (38 44 R t.uas.t n 1 1 P 4 (31

"^a "trul'." t'Jf.O Fort Calhoun Station Unit No. 1 015 l0 l0 lc l 21815 81 9 -

01112 -

0 11 01 S OF 015 wt u . - e w uw nn Motor operated valve HCV-308 has a non-locking operator gear set. As a result, it currently can not be tested. Modification package MR-FC-86-91 is being generated to eliminate this problem. This package is scheduled for completion during the 1990 refueling outage. In addition, an air operated valve provides an alternate flow path.

Valves HCV-1103 and HCV-110% are the redundant valves upstream of valves HCV-1386 and HCV-1385, respectively. These valves receive a Steam Generator Isolation Signal (SGIS), but are not taken credit for in the accident analysis and are not censidered safety grade. The safety function of HCV-1386 is to isolate main feedwater flow to steam generator RC-2A upon receipt of a SGIS. SGIS is designed to minimize the cooldown of the reactor coolant system in the event of a main steam line break.

ItisassumedintheUpdatedSafetyAnalysisReport(USAR)thatfeedwater isolates within 30 seconds after SGIS is actuated. Therefore, in the event of a steam line break, feedwater to steam generator RC-2A may not have isolated (prior to resetting of the torque switches) in the assumed time with HCV-1386 inoperable. No valid SGIS was initiated during the time period that HCV-1386 was inoperable.

Although reports of inability to remotely operate valves have been submitted in the past this is the first reported case of inability to closeavalveduetoImproperlysettorqueswitches.

I I

i l

I l

l l

l l- e cl'es.n sena ts i

- .___ -