ML20006A866

LER 89-041-00:on 891221,automatic Actuation of Emergency Feedwater Sys Initiated.Caused by Lack of Adequate Procedural Guidance.Valve Positioners CV-2623 & CV-2673 Adjusted & Guidance Procedures developed.W/900122 Ltr

ML20006A866
Person / Time
Site:	Arkansas Nuclear
Issue date:	01/22/1990
From:	Ewing E, Taylor L ARKANSAS POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
1CAN019013, 1CAN19013, LER-89-041, LER-89-41, NUDOCS 9001300377
Download: ML20006A866 (4)

Text

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January 22, 1990 j ICAN019013 {

U. S. Nuclear Regulatory Commission Document Control Desk i Mail Station P1-137

• Washington, D. C. 20555

SUBJECT:

Arkansas Nuclear One - Unit 1 k Docket No. 50-313 License No. OPR-51 Licensee Event Report No. 50-313/89-041-00 Gentlemen:

In accordance with 10CFR50.73(a)(2)(IV), attached is the subject report concerning an Emergency Feedwater System actuation due to a low level in the 'B' Once Through Steam Generator which resulted from inadequate guidance with respect to calibration of control valves. .'

Very truly yours,

( E. C. Ewing l General Manager, Technical Support and Assessment ECE/RHS/abw attachment cc: Regional Administrator Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011

'NPO Records Center 1500 Circle 75 Parkway

• Atlanta, GA 30339-3064 b

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1. '- . i Fore 1062.03A NRC Form 366 U.S. Nuclear Regulatory Commission (9 83) Approved OMB No. 3160-0104

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FACILITY NAME (1) Arkansas Nuclear One. Unit One IDOChET NJM6fR (2) iPAGE (3) 10151010101 31 11 Siller!0l}

TITLE (4) Emergency Feepwater System Actuation Due to a Low Level In the 'B' Once Through 5 team Generator Which Resulted From Inadeguate Guidance With Respect To Calibration of Control Ys1ves

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LICENSEE CONTACT FOR THI6 LER (12)

Name l Telephone NJmber lArea l Larry A. Talyor. Nuclear safety and Licensing specialist ICode l 1Q01119f6141-13filQLQ COMPttit ONE LINF FOR ( ACH COMPON(NT F AILUPI DESCN!B(D IN THIS REPORT (13) l l l lReportabiel l l l l lReportablel Causelsysteel Component inanufacturert to NPRDS 1 ICauselsycteel Component IManuf acturert to NPRDS I i 1 l l l l 1 l l l 1 1 1 l I I I i 1 1 I I I i 1 I I I I i 1 1 I I I I l l l l l l l l l l 1 1 I I I I i f f I i 1 I I i i I I I I f f I I I i '

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. . I SUBM15510N I I l 1 I Yes (Tf ves complete troected Submission Date) lxl No i DATI (15) i I I i 1 1 ABSTRACT (Limit to 1400 spaces, i.e. , approximately fif teen single space typewritten Itnes) (16)

On December 21, 1989, at apprcximately 0140, an automatic actuation of the toergency Foodwater System (EFW) was initiated as a result of a low level in the 'B' Once through steam Generators (0T50). At the time of the trW actuation, the plant was at hot shutdown with decay heat being removed by steaming both OT5Gs to the condenser betwell. The auxilliery feedwater pump was in operation supplying feedwater to the CT5Gs through startup feedwater control valves CV 2623 and CV-2673. However, due to leakage through these valves it had become necessary to throttle open manual feedwater recirculation valves FW-8A and B to maintain CTSG 1evels. The 'A' OT5G was above its' programmed level and its associated control valve was closed. However, when the ' A' 0750 level decreased to its low level control limit, its' control valve began to open. With both rectre valves open and feedwater being supplied to both OT5Gs.

the capacity of the aux 1111ery feedwater pump was exceeded. Feedwater pressure decreased and 0T50 levels continued to fall until LFW was initiated. The EFW system actuated as designed and the feed-water system parameters and 0T50 levels were expeditiously returned to normal. This event was caused by CV-2623 and CV 2673 leaking by their seats with the valves in the closed position. This leakage resulted from a lack of adeQucte guidance with respect to setup and calibration of the control valves.

The valves were calibrated with tr.e feedwater system at pressure and were verified not to be leaking.

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f Fem 1062.018

. NRC Fom 366A U.S. Nuclear Regulatory Commission (9 23) Approved OMP No. 3150-0104 Expires: 8/31/85 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACitlTY hAME (1) 100CKET NUS ER (2) l L(R Nue BER (6) l PAGE (3) l l l l$equentiali IRevisionl Arkansas Nuclear One, Unit one l l Yearl i Number l I Number l 10lbl010101 31 11 31 et 91--t of al 11--I of Ol01210Fl0l3 tex 1 (It more space is required, use additional NRC Fore 366A's) (17)

A. Plant Status At the time of this event. Arkansas Nuclear One, Unit 1 (AND-1) was in the Hot Shutdown condition. Reactor Coolant System (RCS)[AB) tes;perature was approximately 539 degrees with RCS pressure at 2155 psig.

B. Event Description On December 21, 11,89 31 0140, an Emergency Feedwater Initiation and Control (EFIC) actuation of the Emergency Feedwater System (EFW) [BA) was initiated as a result of a low level in the 'B' Once Thr9 ugh steam Generator (OT5G).

At the ties of the EFW actuation AND-1 was in Hot Shutdown, with decay heat being removed by steaming both OT5Gs to the cohdenser hotwell. The auxiliary feedweter pump (P-75) was in operation supplying feedwater to the OTSGs. The 'A' OTSG was being boiled down following a fill and drain for OT5G cleanup, and the 'B' OTSG 1evel was being maintained at its low level limits by the Integrated Control System (ICS) (JA) control of the 'B' startup feedwater control valve (CV 2673). Since the 'A' OT5G 1evel was above its low level control limit, the 'A' startup feedwater control valve (CV 2623) was closed. However, due to leakage through CV-2623 and CV 2673, which was greeter than the boll off rate, it had become necessary to throttle open manual feedwater startup recirculation valves FW-BA and FW-8B to maintain feedwater header pressure at approximately 900 psig. Turbine bypass valve CV-6688 was placed in automatic operation to limit OTEC pressure as heatup continued. When the ' A' OT5G reached its low level control point, the ' A' startup control valve (CV 2623) began to open to maintain level. Due to the valve lineup (FW-8A, B open) and the limited capacity of P-75, feedwater pressure to both OT5Gs began to drop. CV-2673 opened in response to this pressure decrease and feedwater pressure dropped to approximately 600 psig (less than OT5G pressure). Since feedwater pressure was less than 0T53 p* essure, no feedwater was being added to the OT5Gs and levels continued to decrease. An operator was immediately dispatched to close FW-8A and B. FW-8A was closed quickly. However, FW-88, tne recirculation valve for the 'B' 075G, took longer to close due to its location and type of operator. During this time, the 'B' OT5G 1evel continued to decrease untti EFIC actuated the EFW system on OT5G 'B' low level. 1he EFW system actuated as designed, with both the steam driven (F 7A) and the motor driven (P 78) EFW pumps starting. The steam admission valves for P-7A were immediately placed in manual and closed. Feedwater system pressure and OTSG 1evels were quickly restored to normal. At approximately 0146. P-78 was secured. EFIC was reset and normal feer

• water flow was restored to the OT5Gs.

C. Safety Significance The EFW system was automatically actuated due to a low level in the 'B' OTSG, as designed. There were no malfunctions of any safety related eqt ipment during the response to this event. The reacto* wad suberitical and remained suberitical throughout the event. Adequate OTSG 1evels and decay beat removal were maintained throughout the event.

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0. Root Cause l

The cause of this event was determined to be a lack of adequate procedural guidance with respect to the proper ' setup' of the startup feedwater control valves. This lack of guidance resulted in the valves (CV 2623 CV-2673) not being properly seated with a zero demand signal applied to the valve positioner. Conseguintly, the valves leaked by when they should have been closed, requiring the opening of FW BA and B to contec1 OTSG 1evels.

E. Basis for Reportability The automatic actuation of the EFW system on low OT5G 1evel is considered reportable pursuant to 10CFR50.73 (a)(2)(IV) as the automatic actuation of an Engineered Safety Feature.

This event was also reported in accordance with 20CFR50.72 at 0305 on December 21, 1989.

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Fors 1062.018 NRC Fore 366A U.S. Nuclear Regulatory Copeission (9 83) Approved OMB No. 3150-0104 Empires: 8/31/65 LICEN$tt EVENT REPORT (LER) TEXT CONTINVAT10N IATIIIIYhAMI(11 100Ch[1 NUM8[k (2) l MR N@S[R (6) l PAGE (3) '

l l l l$equentiell IRevisioni Arkansas Nuclear One, Unit One l l Yeart i Number l ! Number l 10!$1010101 31 11 31 81 91--I 01 41 Il--t Of 0101310F1013 TEAT (If more space is required, use additional NRC Fore 366A's) (17)

F. Corrective Actions The valve positioners for CV 2623 and CV 2673 were adjusted to provide a positive seat with the feedweter systee at operating pressure. After the adjustment, the valves were verified not to be leaking.

Procedural Guidance is being developed to provide specific instructions regarding the proper method of calibration for control vehes CV 2623 and CV-2673. This guid.nce is expected to be completed by August 1,1990, which is prior to the next required calibraticn of the valves.

In addition, a review is being concocted to deterwine if additional guidance is required for the setup and calibration of other plant control valves. This review and any procedure changes that may be required will be completed by March 30, 1990.

G. Additional Information A similar event involving a leaking startup feedwater control valve in which the IFW system was manually initiated was reported in LER 50 313/89-020-00. The evaluation of that event identified equipment problems but failed to identify the lack of adequate calibration and setup guidance for the control valves.

Energy Industry adentification System ([115) codes are indicated in the text as (XX).

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