ML17348A541

LER 90-016-00:on 900801,Tech Spec 3.0.1 Entered to Repair Boric Acid Filter Discharge Isolation Valve 3-348.Caused by Exposure to Higher than Normal Temps.Diaphragm Replaced on Valve & Wrap of Heat Tracing rerouted.W/900830 Ltr

ML17348A541
Person / Time
Site:	Turkey Point
Issue date:	08/30/1990
From:	Harris K, Dawn Powell FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-90-308, LER-90-016, LER-90-16, NUDOCS 9009050417
Download: ML17348A541 (6)

Text

ACCELERATED DISTRIBUTION SYSTEM DEMONSTRATION REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9009050417 DOC.DATE: 90/08/30 NOTARIZED: NO DOCKET FACIL:50-250 Turkey Point Plant, Unit 3, Florida Power and Light C 05000250 AUTH. NAME AUTHOR AFFILIATION POWELL,D.R. Florida Power 6 Light Co.

HARRIS,K.N. Florida Power 6 Light Co.

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 90-016-00:on 900801,Tech Spec 3.0.1 entered to repair boric acid'filter discharge isolation vaLve 3-348. W/9 DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

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

NOTES RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL

,PD2-2 LA 1 1 PD2-2 'PD 1 1 EDISON,G 1 1

.INTERNAL: ACNW 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB9H3 1 1 NRR/DLPQ/LHFB11 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB11 1 1 NRR/DREP/PRPBll 2 2 NRR /SELB 8D 1 1 NRR/DST/SICB 7E 1 1 R~

REG FILE PLB8D1 02 1

1 1

1 NRR/DST/SRXB 8E RES/DSIR/EIB 1

1 1

1 LE 01 1 1 EXTERNAL: EGGG BRYCE,J.H 3 '3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MAYS,G 1 1 NSIC MURPHYIG.A 1 1 NUDOCS FULL TXT 1 1

'OTE TO ALL "RIDS" RECIPIENTS:

CONTROL DESK,,

PLEASE HELP US TO REDUCE %VASTE! CONTACT THE DOCUMENT ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 31 ENCL 31

P.O. Box14000, Juno Beach, FL 33408.0420 AUG ',",0 $ 990 L-90-308 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

Re: Turkey Point Unit 3 Docket No. 50-250 Reportable Event: 90-016 Date of Event: August 1, 1990 Technical Specification 3.0.1 Entered to Repair Boric Acid Filter Dischar e Isolation Valve 3-348 The attached Licensee Event Report is being provided pursuant to the requirements of 10CFR50.73 as notification of the subject event.

Very truly yours,

/g K. N.,Hkkri's

. Vice+resident Turkey Point Nuclear Plant KNH/DRP/dwh Attachment cc: Stewart D. Ebneter, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, Turkey Point Plant centi,t t:,

NRC Form 366 U.S. NUCLEAR REGULATORY COMMISSION r6 63 i APPROVEO OMB NO 3150.0104 LICENSEE EVENT REPORT ILER) EXPIRES'i3)iBE I'A 3(

FACILITY NAME Ill DOCKET NUMBER (2I E Turkey Point Uni t 3 02 5 01OF Technical Specification 3.0.1 Entered To Repair Boric Acid Filter Discharge Isolation Valve 3-348 OTHER FACILITIES INVOLVED (SI EVENT DATE IS) LER NUMBER I6) REPORT DA'TE (7(

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MONTH QAV YEAR 4VMSE4 4UVBE4 N/A 0 5 0 0 0 0 8 0 1 90 90 0 1 6 0 0 0 8 3 0 9 0 N/A 0 5 0 0 0 THIS REPORT IS SUBMITTED PURSUANT 7 0 THE REQUIREMENTs of 10 cFR 6, Ichtrc oht pr mo/t of Iht forlorn hpl (11 OPERATING MODE ISI 20.402((rl 20A05(cl 50.73(tH2Hivl 73.7) ((r )

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On July 29, 1990, with Unit 3 in Mode 1 at 100 percent in the power, a leak of approximately 1 drop/minute was noticed area of- boric acid filter discharge isolation valve 3-348. A flow path from the boric acid tanks to the Reactor Coolant System (RCS) was established via the boric acid filter bypass line and valve 3-348 was closed to reduce valve leakage. 'Valve 3-348 is a diaphragm valve. The diaphragm also serves as the gasket between the valve body and bonnet mating surfaces. Upon inspection, the -diaphragm exhibited waved edges on two sides which appeared significant enough to degrade the seal between the valve body and bonnet. This deformation was caused by exposure to higher than normal temperatures which reduced the normal life expectancy of the diaphragm. In order to repair valve 3-348, the boric acid filter bypass line must be the isolated. This configuration results in no flow path from boric acid tanks to the RCS. Technical Specification to operable (TS) 3.6 to requires system piping, interlocks and valves be the boric acid the extent of establishing one flow path from storage tank, tanks, and one flow path from the refueling water on August 1, to the RCS when the reactor is critical. At 0950,power, Unit 3 1990, with Unit 3 in Mode 1 at 100 percent entered TS 3.0.1 to repair valve 3-348. The valve was repaired and returned to service at 1038. Unit 3 exited TS 3.0.1 at this time.

NRC Form 366 66)

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~ <<UM ~ << 'M Turkey Point Unit 3 o s o o o 2,5 0 9 0 0 1 6 0 0 2 oF TEx 5 rrr mo~ ssr<<r<< il ~v<<od. vw <<ddrt<<ro<<r sr Ac <drrrr!66A'll II!I DESCRIPTION OF THE EVENT On July 29, 1990, with Unit 3 in Mode 1 at 100 percent power, a leak of approximately 1 drop/minute was noticed in the area of boric acid filter discharge isolation valve 3-348 (EIIS:CB, Component:ISV). Upon investigation, a leak of approximately 5 drops/second was confirmed to be coming from the 3-348 valve bonnet gasket. Valve 3-348 is a diaphragm valve. The diaphragm also serves as the gasket between the valve body and bonnet mating surfaces. A flow path from the boric acid tanks to the Reactor Coolant System (RCS) was established via the boric acid filter bypass line and valve 3-348 was closed to reduce valve leakage.

In order to repair valve 3-348, the boric acid filter bypass line must be isolated. This configuration results in no flow.

path from the boric acid tanks to the RCS during valve repair.

Technical Specification (TS) 3<<6 requires system piping, interlocks and valves to be operable to the extent of establishing one flow path from the boric acid tanks, and one flow path from the refueling water storage tank, to the RCS when the reactor is critical.

Replacement of the diaphragm on valve 3-348 was estimated to take less than one hour. At 0950, on August 1, 1990, with Unit.

3 in Mode 1 at 100 percent power, TS 3.0.1 was entered to replace the diaphragm on boric acid filter discharge isolation valve 3-348. At 1038, on August 1, 1990, valve 3-348 was repaired and returned to service. Unit 3 exited TS 3.0.1 at this time.

CAUSE OF THE EVENT The cause for the diaphragm failure on valve 3-348 is exposure to higher than normal temperatures. This condition reduced the normal life expectancy of. the diaphragm.

An inspection of the valve 3-348 diaphragm revealed no evidence of cracking or tearing. The valve body and bonnet mating surfaces were not. observed to be degraded. However, the diaphragm did exhibit rippled or waved edges on two sides which appeared significant enough to degrade the seal between the valve body and bonnet.

The as-found condition of the diaphragm was conveyed to a representative of the valve- vendor. Based on the information available, the vendor representative stated that the waved

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• WC I ITI o o o 2 5 0 9 0 1 6 0 0 OF edges of the diaphragm was indicative of exposure to higher than normal temperatures over the life of the diaphragm which would reduce the diaphragm life expectancy. Two possible causes for this condition were suggested: (1) an overheating event, and (2) the valve bonnet being heat traced.

A review of documented problems with the heat tracing circuit associated with valve 3-348 revealed an over-temperature event in November 1987. The affected. heat tracing circuit was to be operating between 188 degrees Fahrenheit (F) andfound 192 degrees F. The normal temperature range for this circuit is between 160 degrees F and 170 degrees F. Additionally, one wrap of heat tracing was discovered on the valve 3-348 bonnet upon disassembly for repair.

Under the operational conditions experienced by valve 3-348, the normal service life of the diaphragm is expected to be approximately five years. The last diaphragm replacement on valve 3-348 occurred about three years and four months ago.

i ANALYSIS OF THE EVENT No credit is taken for the concentrated boric acid contained in the boric acid tanks in any of the Design Basis Accidents described in the Turkey Point Final Safety Analysis Report (FSAR). Sufficient shutdown margin under hot shutdown conditions for the most severe anticipated cooldown transient (main steam line break (MSLB) ), assuming the most reactive rod control cluster to be fully withdrawn, is achieved via the use of boron from the refueling water storage tank through the Safety Injection System. The MSLB analysis does allow the reactor to return to criticality due to positive reactivity inserted from cooldown, provided no core damage occurs. A Westinghouse analysis demonstrates that no core damage- will occur during cooldown. The boric acid tanks and the boric acid transfer pumps provide a source of concentrated boric acid to be added to the RCS to offset reactivity changes caused by .

normal plant operating transients, changes in power level, and in order to attain and maintain cold shutdown conditions. An additional means of providing borated water is from the refueling water storage tank through the charging pumps to the RCS. These flow paths (refueling water storage tank to the charging pumps and to the safety injection pumps) were available throughout the event.

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vE J ~ SSOMSVT>AL 4SV'S>ov vga 4 v/4 S4 Turkey Point Unit 3 o s o o o 2 5 0 9 0 01 6 00 4 oF TEXT UI ~W I4rCr 4 tarvia~, vW Sad tm~ AIIC f~ J66A'I) 1171 CORRECTIVE ACTIONS

1. The diaphragm has been replaced on valve 3-348. The one wrap of heat tracing was re-routed away from the valve 3-348 bonnet.

2. The diaphragm on valve 4-348 will be replaced during the next Unit 4 refueling outage. The associated heat tracing circuit will be verified not to be wrapped around the valve bonnet after the diaphragm is replaced.

3. On May 8, 1990, Corrective Maintenance Electrical procedure O-CME-048.3, "Heat Tracing Circuit Maintenance," was revised to indicate that only valve bodies need to be heat traced.

4. This event has been discussed during a weekly electrical maintenance shop meeting.

ADDITIONAL INFORMATION Similar events have been reported to the NRC in LER 50-250/89-013 and LER 50-251/89-009. However, these events did not share the same root cause as this event.

Valve 3-348 is a 2 inch Grinnell diaphragm valve, drawing number WREF-4-SS or Westinghouse designation 2-X42D.

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