ML19354E018

LER 89-024-00:on 891223,manual Trip of Plant Initiated in Response to Decreasing Level in Steam Generator.Caused Probably by Anomaly in Main Feed Regulating Valve Pneumatic Control Sys.Tent Erected Around valve.W/900122 Ltr

ML19354E018
Person / Time
Site:	Waterford
Issue date:	01/22/1990
From:	Mcgaha J, Packer D LOUISIANA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-024, LER-89-24, W3A90-0106, W3A90-106, NUDOCS 9001250231
Download: ML19354E018 (8)

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Ref:1 10CFR50.73(a)(2)(iv)

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January 22, 1990, 'i U.S. Nuclear Regulatory Commission- ,

ATTENTION - Document Control Desk ,

Washington, D.C.- 20555.

Subjects.' Waterford 3.SES Docket No. 50-382~

. License No. NPF-38 Reporting of Licensee Event-Report.

Gentlemen Attached is Licensee Event Report Number LER-89-024-00 for Waterford Steam Electric-Station Unit 3. This Licensee Event Report is submitted pursuant to 10CFR50.73(a)(2)(iv).-

Very truly yours, i

J.R. McGaha- ( '

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Plant Manager' . Nuclear cJRM/KTW/rk -

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cci Messrs. R.D. Martin

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E.L.-Blake W.M. Stevenson j ,. 'D.L. Wigginton- . .;

NRC Resident' Inspectors Office, '

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F ACILITY NAME (1) DOCKE T NUMSER (2) PAGE G hterford Steam Electric ' Station Unit 3 0 15101010l 31812 1 lOFl 017 flTLE tes Renetor Trin due to Loss of Feedwater Flow to Steam Generator #1 EVENT DATE (S) LER NUMBER (61 REPORT DATE (h OTHER F ACILITIES INVOLVED (el MONTH DAY YEAR YEAR S'OU$f 75 % MONTH DAY YEAR f aciuTV NAMES DOCKET NUMBER 151 N/A 015l0l0l0l l l

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1l2 2b 89 8l9 0l 2 l4 0l0 0 l1 2 l2 9 l0 N/A 0l5l0 1 0gog l l OPE R ATING THIS REPORT IS SUOMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR % ICn.d oa, er . nog er the to,/owrapf 111)

"'# 1 20 4021st 20 4051e1 X 50.736el(2Hol 73.71M power 20 406deH1Hil 50.30 teHil 90.73teH2 Het 73.711s1 10 ' 110l0 20 40si.HiMei s0 m.im son.H2H. i OTHER GewW M AMmn to 40 Blah 1 Heit 60.78 tall 2HG S0.73(aH2 HvdiHA) 4A 20 404teH1Hlv) 50.73 eH2Hul so.73(aH2HeniHBI 20.405 eH1Het 50.78taH210ii) to 73lal(2Hal LICENSEE CONT ACT FOR THl$ LER (12)

NAME TELEPHONE NVM8ER ARE A CODE D.F. Packer, Assistant Plant Manager O M 51014 4l 614l-13 111314 COMPLETE ONE LINE FOR E ACH COMPONENT F AILURE DESCRISED IN TH18 REPORT 113) k REPORTA E  ;

CAUSE SYSTEM COMPONENT "'yj'f g "fD NPR S' CAUSE SYSTEM COMPONENT MAMC 1

l I I I I i1 l l t l l l l t I I I I I I I I I I i l i l SUPPLEMENTAL REPORT E XPECTED (14) MONTH DAY YEAR

~5 vEs m ,... . ,.. emerso sU,wss,0N oA m -"]NO 0l5 3l 0 910 Aes,R ACT a,-,, M uoo Ma... . . . mm.w, un., ,,, Ma. n erw,1-.,> n e, At 1109 hours0.0128 days <br />0.308 hours <br />0.00183 weeks <br />4.219745e-4 months <br /> on December 23, 1989, control room operators initiated a manual reactor trip of Waterford Steam Electric Station Unit 3 while operating at 100%

power. The trip was initiated in response to decreasing level in Steam Generator (SG) #1 after Main Feed Regulating Valve (MFRV) #1 unexpectedly failed shut. Shortly after the reactor trip MTRV #1 opened inadvertently. A Reactor Coolant System (RCS) cooldown and a corresponding RCS pressure drop to approximately 1640 psia resulted, generating a Safety injection Actuation Signal (SIAS). An Emergency Feedwater Actuation Signal (EFAS) was also generated during the post-trip transient.

The root cause of this event appears to be an anomaly in the MFRV pneumatic control system brought about by cold weather effects on system components._-A-vendor diagnostic team will be contracted to provide.an indepth investigation to aid in root cause determination.- If the root cause can be positively identified it will be described in a. revision to this report. All safety systems functioned as designed; therefore, this event did not threaten the health and safety of the general public or plant personnel.

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At 1103 hours0.0128 days <br />0.306 hours <br />0.00182 weeks <br />4.196915e-4 months <br /> on December 23, 1989, Waterford Steam Electric Station Unit 3 was operating at 100% power when a Steam Flow /Feedwater Flow signal deviation -

alarm (EIIS Identifier IB-FFA) was received for both steam generator's (SG) ,

(EIIS Identifier-SG), SG #1 level was observed decreasing with SG #2 level '

observed increasing. Control room. operators. assumed manual control of both main feedwater regulating valve (MFRV) (Ells Identifier SJ-FCV) and SG Feed e

Pump -(SGFP) (EIIS Identifier SG-P) controllers (EIIS Identifier-FCO). MFRV #2 responded'normally to operator input. signals; however,LMFRV #1' responded '

sluggishly by cycling between 5.0E6 and 8.0E6 lbm/hr..'At 1109 hours0.0128 days <br />0.308 hours <br />0.00183 weeks <br />4.219745e-4 months <br /> MFRV #1 ,

-unexpectedly failed shut and would not-respond-to manual input signals. Control room personnel tripped the reactor as'SG #1 level approached its reactor

. protection system (RPS) (EIIS Identifier-JC) low level trip setpoint, preempting a challenge to the RPS.

During the minute following the reactor trip, MFRV #1 opened to approximately 40%, inducing a reactor coolant system (RCS) (EIIS Identifier-AB) cooldown and l corresponding RCS pressure decrease. RCS pressure decreased below the safety injection actuation signal (SIAS) (EIIS ldentifier-JE) setpoint of 1684 psia (lowest pressure reached-1640 psia). All safety injection (SI) system (EIIS Identifier-BP/BQ) components started as designed; however, no SI flow was-injected into the RCS. Also initiated during the minute following'the reactor trip was an. emergency feedwater actuation signal'(EFAS) (EIIS Identifier-JE),

which started emergency feedwater system (EFW) (EIIS Identifier-BA) components.

After taking manual control of MFRV #1, control room personnel were able to shut MFRV #1, gain control of SG level and RCS pressure and stabilize plant conditions in Mode 3 (Hot Standby).

Earlier on December 23, 1989, at 0448 hours0.00519 days <br />0.124 hours <br />7.407407e-4 weeks <br />1.70464e-4 months <br />, a Steam Flow /Feedwater Flow signal deviation alarm was received and SG #2 level was observed to.be increasing.

Operators took manual control of MFRV #2 and SGFP controllers and were able to stabilize SG level. Instrumentation and Control (I&C) technicians were called in to investigate the problem but did not identify any abnormalities in the associated valve control circuitry. MFRV and SGFP control was placed in automatic at 0815 hours0.00943 days <br />0.226 hours <br />0.00135 weeks <br />3.101075e-4 months <br />.

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TEXT (# mom ausse 4 #seused ses asistaanst NNC Form 3E54 W IIM The root cause of the event is believed to_be a cold weather induced anomaly

'in the MFRV pneumatic positioning system.~ The MFRV's are 16-inch angle globe valves controlled by an electro-pneumatic. control. system.- An electrical signal

.from the feedwater control. system (FWCS) (EIIS Identifier-JB) is converted to '

a pneumatic signal in the electro-pneumatic (E/P) converter (EIIS: Identifier- ,

CNV) which in turn supplies instrument-air (IA) (EIIS Identifier-LD) to the valve positioner (Fisher Controls 'Inc. . .Model 3570) . Also in the pneumatic

. control system is an air regulator-(EIIS Identifier-RG),; volume booster relays, solenoid valves (EIIS Identifier SOL-V),- pneumatic valves, and a check valve. -

The majority of these components employ the use of ' diaphragms (primarily Buna-N .

and Viton) of which the most limiting are' designed.for temperatures in'the range of 0 to 150 degrees F. At the_ time of the MFRV failures,. ambient temperatures were 12-15 degrees F. Because these components.are externally mounted and were subjected'to abnormally low temperatures, it is-possible that MFRV response was affected by degraded-diaphragm performance (st1ffness) in one or more of the components mentioned above.

Another cause under investigation is ice particle formation in the,IA system which could have clogged small air flow passages-in the positioner or some other component. Valve filter regulator blowdowns conducted _after the trip did not indicate any moisture. Also, shiftly blowdowns of system low points had not indicated maisture content prior to or after this event. Dewpoint indications have routinely been well within allowed 1cvels-(-20 degree F p dewpoint alarm setpoint); however, due to the seriousness of this event the IA l

task force vill reexamine current practices to ensure that adequate measures exist to. preclude the presence of moisture in the IA system.

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01 0 Ol4 OF gl7 TEXT I# niere w 4 #soussif, see esMooas/ #RC form W W (D) i It is important to note that within 30 minutes of both MFRV abnormalities on December 23-(0448 and 1103 hours0.0128 days <br />0.306 hours <br />0.00182 weeks <br />4.196915e-4 months <br />), similar problems were observed with #1 High Pressure (HP) Feedwater Heater level control valve (LCV) (E1IS Identifier +

SJ-LCV) and Moisture Separator Reheater (MSR) temperature control valves (TCVs)

(E11S Identifier SB-TCV). HP.Feedwater lleater LCVs and MSR TCVs utilize a similar pneumatic operating system..

These valves along with the FWCS valves are the only major control type valves at Waterford'3 that are. unprotected from the environment.- Other major valves.

outside plant enclosures are normally open or closed valves and not subject to changing positions as a result of small variations in plant parameters or

(; operatir<B level. This further supports our theory of a cold'veather induced i

j anomaly, t

Fisher Controls, Inc. personnel have been contacted regarding this issue; however, no definitive conclusions can be drawn as to the exact cause of the anomaly. .A Fisher troubleshooting team which utilizes pneumatic system-diagnostic equipment will be contracted during-the next practicsl opportunity i

(2-3 day shutdown period) to aid in root cause determination.-- If further investigation leads to an exact cause, a revision to this report will describe the additional findings. An NPRDS search for similar malfunctions was conducted.

Several symptomatically similar events have occurred, but no significant developments which aid in cause determination have arisen.

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0l 0 0l 5 OF 0l7 The RCS cooldown and subsequent SIAS was caused by MFRV #1. opening independent  ;

of operator action. While attempting to gain control of MFRV #1 after it had inadvertently shut, the operator initiated a-demand signal'to open MFRV #1. '

Unresponsive to this demand signal, MFRV.#1 remained shut and the reactor.was tripped. After tripping the reactor, the operat' ors properly carried out. actions required by plant procedures which included verifying the MFRVs shut. .The. '

operator assumed MFRV #1 had; failed closed:- No consideration was-given for an intermittent-failure that would immediately' correct itself. When the effects of the anomaly that caused MFRV # 1 to' shut subsided. MFRV #1 operated according to its demand signal (approximately 40% open)'. This'feedwater flow together with a failure of MSR #2 TCVs to fully-shut caused'the~RCS cooldown that followed the trip. Although not specifically required by Emergency Operating Procedures, entering a 0% demand signal to the FWCS manual / automatic;(M/A) station as a precautionary measure would have prevented MFRV #1-from opening.

Because of the nature of this problem, the consideration of a. potential intermittent FWCS failure will-be=added to operator initial and requalification training programs to prevent future occurrences.

Immediately following the trip a tent was erected around the MFRVs'and portable  ;

heaters were installed to remove the effects of the low temperatures. After '

reactor startup with local temperatures still in the teens no further problems were observed with MFRV Control.

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j Plant systems (including SI and EFW) were aligned for startup and the plant

=vas placed back on the grid at 0634 hourc on December 24, 1989. To summarize, the following actions are being carried out to identify the cause and'to-prevent recurrence:

1. Evaluate the plant freeze protection procedure for possible enhancements that could preclude ~ future cold weather induced equipment malfunctions.

Any enhancements will be incorporated into procedures prior to July 31, ,

1990. A critique of this event has been prepared and applicabic portions will be implemented via an Operations department standing instruction if freezing temperatures'are encountered in the near term.

2. Reassemble-the IA task force to assess current practices pertaining to maintaining a moisture. free IA system. Changes to current practices-and/or plant design will be identified and a schedule for implementation:

established by March 15, 1990.

3.

Obtain vendor assistance during the next plant outage of at'least 2 to-3 days duration to aid in root cause determination.

4. Instruct operators to verify FWCS in automatic or to input a zero demand signal into the FWCS M/A station following a- trip as a precautionary measure when in manual control. These instructions-will befincorporated into operator initial and requalification training by March 23, 1990.

-Because all safety. systems functioned as designed, there was no threat-to the-

-health and safety of the general public or plant personnel during this event.

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1 LER 85-029 described a reactor trip which was caused.by high SG level due.to-MFRV positioners. being out of adjustment but was not cold weather < related.

PLANT CONTACT

.D.F. Packer., Assistant Plant Manager, Operations & Maintenance 504/464-3134. '

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