ML17311A881

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LER 94-008-00:on 941126,controlled Reactor Shutdown Commenced to Isolate & Repair Leaking Pressurizer Vent Valves,Per TS Limiting Condition for Operation 3.4.10,action (A).Valves reworked.W/941223 Ltr
ML17311A881
Person / Time
Site: Palo Verde Arizona Public Service icon.png
Issue date: 12/23/1994
From: Grabo B, James M. Levine
ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
192-00917-JML-B, 192-917-JML-B, LER-94-008-02, LER-94-8-2, NUDOCS 9505190265
Download: ML17311A881 (20)
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Text

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DEACCESSION NBR:9505190265 DOC.DATE: 94/12/23 NOTARIZED: NO DOCKET FACZL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528 AUTH. NAME AUTHOR AFFILIATION GRABO,B.A. Arizona Public Service Co. (formerly Arizona Nuclear Power LEVZNEgJ.M. Arizona Public Service Co. (formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION P

SUBJECT:

LER 94-008-00:on 941126,controlled reactor shutdown commenced to isolate & repair leaking pressurizer vent valves,per TS limiting condition for operation 3.4.10,action (a ) . Valves reworked. W/941223 1 tr .

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL'IZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), ncident Rpt, etc.

NOTES:STANDARDIZED PLANT 05000528 R RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME'D4-2 LTTR ENCL ID CODE/NAME LTTR 'ENCL PD 1 1 HOLIAN, B 1 1 TRAN,L 1 1 INTERNAL: ACRS 1 1 2 2 AEOD/SPD/RRAB 1 1 1 1 NRR/DE/ECGB 1 1 NRR/DE/EELB 1 1 NRR/DE/EMEB 1 1 NRR/DISP/PIPB 1 1 NRR/DOPS/OECB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DSSA/SPLB 1 1 NRR/DSSA/SPSB/B 1 1 D NRR/DSSA/SRXB 1 1 RES/DSIR/EIB 1 1 RGN4 FILE 1 1 p

L ST LOBBY WARD LITCO BRYCE,J,H 01'XTERNAL:

1 1 NOAC MURPHY,G.A 1 1 NOAC POORE,W.

NRC'DR 1 1 NUDOCS FULL TXT VOTE TO ALL"RI DS" RECIPIENTS:

PLEASE HELP US TO REDUCE O'ASTE! COiNTACTTHE DOCL'MEi! COi'TROL i

DESK. ROOih! Pl.37 (EXT. 504-T033 ) TO ELIWIIYATE YOUR YAihIE FROiI DIS'I'Rl Dl."I'ION LIS I S FOR DOC!.'NIEY, I'S YOU DOi "I EED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 28 ENCL 28

AY GS '9S 11t36 CONPLI CE 1

Arizona Public Service Company

, PALO VEROE NUCLEAR GENERATING STATION P.O, 2OX 5~334 - PFIOENIX. ARIZONA II5072-'2334 192-0091 7-JML/BAG/DLK, JAMES M: LEVINE December 23, 1994 VICE PAESIOENT 4tICI.Eett PnOIIVC((Oe U. S. Nuclear Regulatory. Commission ATTN: Document Control Desk Mail Station P1-37 Washington, DC 20555

Dear Sirs:

Sub)ect:

Vnits 1 License.Event Report File: 94420-404

~

Palo Verde Nuclear Generating Station (PVNGS),

Docket No. STN 50-828 {Ucenee No.-NPF<1)

P Attached please find License Event Report (LER) 94-008-00. prepared and submitted pursuant,to 10 CFR 50.73. 'Unit 1 intentionally isolated a. Reactor: Coolant System (RCS) vent path and entered Technical Specication'Limiting Condition for Operation,(TS LCO) 3.4.10, ACTlON, (a) to repair seat leakage on the pressurizer solenoid operated vent valves (RCA-HV-103.and RCB-HV-105). Unit 1 shut down and cooled down to comply with Technical Specifications white repairing RCA-HV-103 and, RCB-HV-105.

ln accordance with 10 CFR 50.73(d), a copy of this LER is being forwarded to the Regional Administrator,, NRC Region, fV.

lf you have any questions, please contact Burton A. Grabo, Section, Leader, Nuclear Regulatory Affairs, at (602) 393-6482.

Sincerely, JML/BAG/DLK/pv Attachment cc: L J. Callan (all with attachment)

K. E. Perkins K E. Johnston INPO Remrds Center 9505190265 94%223 PDR ADQCK 05000528 S PDR

41 V

MAY 85 '95 11)36 CONPLIA CE P.3

~ e ~~ w LICENSEE EVENT REPORT (LER)

ACILITYRANE (I) DOCKET NVMOCR (2) 0 5 0 0 0 5 2 8 t <' 8 I Palo Verde Unit 1 ITLS (e)

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~ CONTACT FOR TIFS LER (12)

'urton A. Grabo, Section Leader, Nvciear,Regulatory Affairs FALURE DESCRSED M TNT REPORT PO) 8.02393-6 ~ 92 IlANUFAC REPORTASLS REPORTASLE TURER TO NFROS TO IA%

sQppLAAIRNTALREpoRT ExpEOTED (Ie) hXFKCZED MOttDI DAY YEAR SUSMSSION bATE (1S)

TRAcT (Len>> nI 1cx) epeaee. Le., AFFKet~lz hneen ano1eeaece TFewnaen Lace) (Ia)

On November 25, 1994, at approximately 0220 MST, Unit 1 Control Room personnel elected to. voluntarily enter Technical Specification Limiting Condition for operation (TS LCO) 3'.4.10, II) ACTION (a) to isolate and repair the pressurizer vent, valv>s (RCA-HV-103 and RCB-HV-105) which ware exhibiting symptoms of abnormal valve position indication and seat leakage.

i(I On November 26, 1994, at approximately 0103 MST, Palo Ver'de Unit 2 was in Mode 1 (POWER OPFRATION), operating at, approximately 1

98 percent power when control Room personnel commenced a controlled reactor shutdown to comply with TS LCO 3.4.10, ACTXON (a). At 0440 MST, the reactor was manually tripped .from 19 percent reactor power in accordance with approved procedures and the plant was stabilized in Mode 3 (HOT STANDBY) by approximately 0538 MST. Control Room personnel continued the Reactor Coolant System (RCS) cooldown and entered Mode 4 (HOT SHUTDOWN) at 1400 MST on November 26, 1994. The plant shutdown and cooldown to Mode 4 were uncomplicated.

Thex'e have been no previous similar events xaported'ursuant to 10 CPR Soe73 in the last three years.

I t'1AY GS '95 1,1:37 CONPLI E P.4 LlCENSEE EVENT REPORT (LER) TEXT CONTlNUATION QOCKET NUMBER yEAR LER NUMBER SEQvEMllAL NUMBER R&ASlo NUMBER

'A Palo Verde Unit 1 0 5 0 0 0 5 2 8 9 4 - 0 0 8 - 0 0 0 2 o 0 8 X- DESCRXPTXON OF .WHAT OCCURRED:

A. Xnitial Conditions:

On November 26, 1994, at 0103 MST, Palo Verde Unit 1 was in Mode 1 (POWER OPERATION), operating at approximately 98 percent power.

B- Reportable Event Description (Xncluding Dates and Approximate Times of Major Occurrences):

Event Classification: Completion of a plant shutdown required by Technical Specifications (TS).

On November 26, 1994, at approximately 0103 MST, Palo Verde Unit 1 Control Room personnel (utility, licensed).

commenced a controlled reactor (AC) shutdown to comply with TS Limiting Condition for Operation (LCO) 3.4.10, ACTION (a). At 0440 MST, the reactor was manually tripped from 19 percent reactor power in accordance with approved procedures, and the plant was stabilized in Mode 3 (HOT STANDBY) by approximately 0538 MST. Control Room personnel continued the Reactor Coolant System (RCS (AB) cooldown and entered Mode 4 (HOT SHUTDOWN) at, 1400 MST on November '26, 1994. The plant shutdown and cooldown to Mode 4 were uncomplicated.

Prior to the event, control Room personnel observed valv position indication (V)(ZI) for RCA-HV-103 and RCB-HV-10 functioning abnormally (e.g., periodic dual position indication, full open indication, and flickering closed indication) and momentary indication of increased pressure in the reactor drain tank (RCT)(DRN)(TK) along with a corresponding pressure drop in the RCS. Control Room personnel performed 40ST-9RC02, "Computer Calculation of RCS Water Inventory Balance 4.4.5.2.-1.c,"

to verify total RCS leakage was within acceptable limits Total RCS leakage was calculated to be 0.14 gpm (within

0 Cl NAY GS '9S 11:38 CONPLI E P.S LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER LER NUMBER PA BMVEMIIAI. REV~

NUMBER NUMBER Palo Verde Unit 1 0'5 0'0 0 5 2 8 94'-008-0003 c 0 8 the maximum, allowable TS 3.4,.5.2 limits of 1.0 gpm UNIDENTIFIED LEAKAGE or 10 gpm IDENTIFIED LEAKAGE). The safety function of RCA-HV-103 and RCB-HV-105 is to open and provide a vent path for the Reactor Coolant System via the pressurizer (AB),. Minor valve seat leakage by itself will not prevent the valves from performing their safety function or cause the valves to be INOPERABLE.

Based on the abnormal valve position indication and the pressure, fluctuations in the reactor drain tank and RCS, a containment (NH) entry was made at power on November 25, 1994 to isolate the pressurizer steam space vent (AB) path (close RCE-V090). The pressurizer steam space vent path was declared INOPERABLE at 0220 MST. On November 25, 1994, Unit 1 elected to voluntarily enter TS LCO 3 4.10, ACTION, (a) to isolate and repair the pressurizer vent valves (RCA-HV-103 and RCB-HV-105) whic, were exhibiting symptoms of abnormal valve position indication and seat leakage. TS LCO 3.4.10 ACTION (a) states:

"With only one of the above required reactor coolant system vent (AB) paths [reactor vessel head (AB) and pressurizer steam space] OPERABLE, from either location restore both paths at that location to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least -HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in HOT SHUTDOWN within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />."

On November 26, 1994, at 0103., Unit 1 commenced a controlled reactor shutdown and cooldown to Mode 4.

Following the reactor shutdown, Operations personnel (utility, non-licensed) isolated the remaining,RCS vent path (reactor vessel vent path) to completely isolate RCA-HV-103 and RCB-HV-105 for maintenance. With both RC vent paths INOPERABLE, on November 26, 1994, at 1525 NST Control Room personnel exited TS LCO 3.4.10, ACTION (a) and entered TS LCO 3.4.10, ACTION (b), which states:

"With none of the above required reactor coolant system vent paths OPERABLE, from either location .restore at

45 II MAY QS '9S 11I38 COHPLI CE LlCENSEE EVENT REPORT (LER) TEXT CONTINUATION OOCKET NUMBER LER NUMSER SEQUENAAL EVISO NUMBER NUMBER Palo Verde Unit 1 0 5 0 0 0 5 2 8 9 4 - 0 0 8 - 0 0 04o 38 least one path at that location to OPERABLE status withi the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> or be in at least HOT STANDBY within th next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in HOT SHUTDOWN within the following 6 hours."

Unit 1 remained in Mode 4 until RCA-HV-103 and RCB-HV-1G were repaired, and both RCS vent paths were restored to OPERABLE status. Control Room personnel exited TS LCO 3.4.10, ACTION (b) on November 28, 1994, at 1804 MST, after satisfactory completion of post maintenance retesting and 73ST-1XI24, "Section XI Valve Stroke Timin:

and Position Indication Verification >> Mode 5 and 6 Reactor and Pressurizer Vent Valves" on RCA-HV-103 and RCB-HV-105. Unit 1 entered Mode 3 at approximately 2122 MST on November 28, 1994.

C. Status of structures, systems, or components that were inoperable at the start of the event that contributed to the event:

Prior to the event, RCA-HV-103 and RCB-HV-105 were exhibiting symptoms of abnormal valve position indicatio and seat leakage. Even though RCA-HV-.103 and RCB-HV-105 were able to perform their safety function, both valves were intentionally isolated to prevent abnormal operatio?

and repair the seat leakage. Isolating RCA-HV-103 and RCB-HV-105 rendered the pressurizer steam space vent pat!

INOPERABLE. Unit 1 shut down to Mode 4 to comply with TS LCO 3.4.10 ACTION (a) .

Cause of each component or system failure, if known:

Because RCA-HV-103 and RCB-HV-105 were able to perform their intended safety function, prior to being isolated for maintenance, neither valve was considered to have failed. Both valves did require maintenance to stop valve seat leakage which prompted isolating the pressurizer steam space vent path and shutting down Unit 1 to comply with TS LCO 3.4.10, ACTION (a); An independent investigation of this event, including an Ecgxipment Root Cause Failure Analysis (ERCFA) on

0 MAY 85 '95 11:39 CONPL CE P.7 L1CENSEE EVENT REPORT (LER) TEXT CONTlNUATlON ACILITYNAME DOCKET NUMBER LER NUMBER gEAR sEoUEHTNl. RENsio NUMBER MUSSED Palo Verde Unit 1 94-008-00 PA<'5000528 0 5 o ') 8 RCA-HV<<103 and RCB-HV-105, was initiated in accordance with the APS Incident Investigation Program. The preliminary findings of the ERCFA determined that the cause of the leakage was due to corrosion/erosion of the primary and secondary pilot valve seating surfaces. The reason for the degraded seating surfaces on the primary and secondary pilots was attributed to the harsh environment (i.e., high temperature, high pressure saturated steam, with boric acid carryovex) that the valves are exposed to.

RCA-HV-103 and RCB-HV-105 are Solenoid-Operated Valves (SOV) (PSV), designed with a seal welded bonnet. The condition of the seating surfaces on the primary and secondary pilots degraded, to the point of unacceptable leakage,'hereby prompting the unplanned reactor shutdown.

E. Failure Mode, mechanism,, and effect. of each failed component, if known:

Not applicable no component failures were involved.

Fox failures of components with multiple functions, list of systems, or secondary functions that were also affected:

Not applicable no failures of components with multiple functions were involved.

G. For a failure that xendered a train of a safety system inopexable, estimated time elapsed from the discovery of the failuxe until the txain was returned to service:

No failures occurred that rendered a train of a safety system INOPERABLE; however, the pressurizer steam space vent path was intentionally rendered INOPERABLE when RCE-V090 was closed to isolate RCA-HV-103 and RCB-HV-105 for repaixs. The pressurizer steam space vent path was INOPERABLE for approximately 88 hours0.00102 days <br />0.0244 hours <br />1.455026e-4 weeks <br />3.3484e-5 months <br />.

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NAY 85 '95 11:39 CONPLI CE P.S LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER LER NUMBER PA SEQUEHllAI. EVlQO Palo Verde Vnit1 05000528 94-.008-0006 0 8 H. Method of discovery of each component or system failure or procedural error:

There were no component or system failures or procedural errors identified. Pressurizer vent valves RCA-HV-103 and RCB-HV-105 did require maintenance to stop valve sea leakage. Prior to the event, valve position indication for RCA-HV-103 and RCB-HV-105 was observed functioning abnormally (e.g., periodic dual position indication, ful open indication, and flickering closed indication) and the valves were exhibiting symptoms of seat leakage.

Cause of Event:

The cause of the event (completion of a plant shutdown required by TS) was attributed to the voluntary entry into TS LCO 3.4.10, ACTION (a) to repair RCA-HV-103 and RCB-HV-105. Unit 1. shut down to Mode 4 to comply with TS LCO 3.4.10, ACTION (a) (SALP Cause Code x: Other).

No unusual characteristics of the work location (e.g.,

noise, heat, poor lighting) directly contributed to this event. There were no procedural errors or personnel errors which contributed to this event.

Safety System Response:

Not applicable there were no safety system responses and none were necessary.

K. Failed:Component Information:

Although no component failures were involved, the leakin pressurizer vent valves (RCA-HV-103 and RCB-HV-105) are SOVs, manufactured by Target Rock Corporation. The Node number for both valves is 76HH-008.

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NAY GS '95 11(48 CONPLI CE P.9 LICENSEE EVENT REPORT (LERj TEXT CONTINUA'nON DOCKETNUMBER LER NUMBER'~R PP sGoU&ETlAL Palo Verde Vnit1 0 5 0 0 0 5 2 8 9 4 - 0 0 8 - 0 0 0 7 ( 0 8 L. Assessment of the Safety Consequences and Xmplications c this Event:

The Unit 1 shutdown and cooldown to Node 4 were controlled evolutions. The manual trip of the reactor from low power (19 percent) and the resulting transient had minimal impact on the plant. The plant shutdown anG cooldown were uncomplicated. The event did not result i any challenges to the fission product barriers or result in any releases of radioactive materials. Therefore, there were no adverse safety consequences or implicatior.

as a result of this event. This event, did not adversely affect the safe operation of the plant or the. health anc safety of the public.

XXX. CORRECTIVE ACTION:

Xmmediate:

Control Room Personnel voluntarily entered TS LCO 3.4.3.0 ACTION (a) to isolate the pressurizer steam space vent path and subsequently performed a controlled shutdown to Mode, 4- An independent investigation of this event, including an ERCFA on RCA-HV-103 and RCB-HV-105, was initiated in accordance with the APS Xncident Investigation Program. RCA-HV-103 and RCB-HV-105 were reworked in accordance with the APS Maintenance Program and returned,to service.

As part of the ERCFA, the maintenance history for RCA-HV-103 and RCB-HV-105 and other SOVs of the. same design in similar applications was reviewed to determine transportability. The review identified other SOVs in Unit 1 as well as Units 2 and. 3 of the same design and i similar applications whose valve internals have not been inspected and refurbished. While some of the SOVs identified during the maintenance history review have some minor seat leakage, the analysis determined the valves are fully capable of performing their intended safety function and do not warrant further immediate corrective action.

0 MAY 85 '95 11:48 CONPLI CE P. 18 r

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER LER NUMBER PA<

YEAR sEQUEMTlAL REvlso NUMBER ~8ER Palo Verde Unit 1 0 5'0 0 0 5 2 8 9 4 - 0 0 8 - 0 0 0 8 o: l 8 B. Action to Prevent Recurrence; Additional actions to prevent recurrence are heing tracked under the commitment action tracking system.

These actions include inspecting and refurbishing the SOVs identified in the maintenance history review (discussed above) over the next two refueling outages in each respective unit.

IV. PREVIOUS SIMILAR EVENTS:

There have been no previous similar events reported pursuant to 10 CFR 50r73 in the last three years.

V. ADDITIONAL INFORMATION:

Unit 1 entered Mode 2 (STARTUP) at approximately 1601 MST an November 29, 1994 and returned to Mode 1 at approximately 0251 HsT, on November 30, 1994. Unit 1 was synchronized on the gric at approximately 1159 MST on November 30, 1994.

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