ML17308A509

LER 90-005-00:on 901112,component Cooling Water HX Pinhole Leak Discovered Due to Shell to Tube Sheet Weld Degradation. Sample of West End Weld Removed & Sent to Lab for Failure analysis.W/901218 Ltr

ML17308A509
Person / Time
Site:	Saint Lucie
Issue date:	12/18/1990
From:	Sager D, Weeks J FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-90-448, LER-90-005-03, NUDOCS 9012260310
Download: ML17308A509 (7)

Text

ACCELERATED ?ATTRIBUTION DEMONSATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9012260310 DOC.DATE: 90/12/18 NOTARIZED: NO DOCKET FACIL:50-389 St. Lucie Plant, Unit 2, Florida Power & Light Co. 05000389 AUTH. NAME AUTHOR AFFILIATION WEEKS,J.W. Florida Power & Light Co.

SAGER,D.A. Florida Power & Light Co.

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 90-005-00:on 901112,component cooling water HX pinhole leak discovered due to shell to tube sheet weld degradation.

Sample of west end weld removed & sent to lab for failure analysis.W/901218 ltr.

DISTRXBUTXON CODE: IE22T COPIES RECEIVED:LTR ENCL SXZE:

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 NORRIS,J 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DS P ,2 2 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFBll .1 1 NRR/DLPQ/LPEB1 0 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB 7E 1 1 NRR DST SPLB8D1 1 1 NRR/DST/SRXB 8E 1 1 G FI 02 1 1 RES/DSIR/EIB 1 1 RGN2 FILE 01 1 1 EXTERNAL EG&G BRYCE I J H 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MAYS,G 1 1 NSIC MURPHY,G.A 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE IVASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOih! P !-37 (EXT. 20079) TO ELIMINATEYOUR NAiVIE FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

P FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUXRED: LTTR 33 ENCL 33

December 18, 1990 L-90-448 10'CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

Re: St. Lucie Unit 2 Docket No. 50-389 Reportable Event: 90-05 Date of Event: November 14, 1990 Component Cooling Water Heat Exchanger Pinhole Leak Due to Shell to Tube Sheet Weld De radation The attached voluntary Licensee Event Report is being submitted to provide notification of the subject event.,

Very truly yours, D. A. ger Vice r sident St. L ie Plant DAS:GRN:kw Attachment cc: Stewart D. Ebneter, Regional Administrator, USNRC Region Senior Resident Inspector, USNRC, St. Lucie Plant II DAS/PSL 4303 90122603]0 903.218 PDR AOOC:K 05000.89 PDR

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/o'n 114 el U.S. NUCLEAR REGULATORY COMMSSION (l~ APPROVEO 0MB NO. 31500104 LICENSEE EVENT REPORT (LER) EXPIRES 8/31/85 FACILITYNAME (1) DOCKET NUMBER (2 PAGE 3 St. Lucie Unit 2 0 500038 91OFO 3 COMPONENT COOLING WATER HEAT EXCHANGER PINHOLE LEAK DUE TO SHELL TO TUBE SHEET WELD DEGRADATION EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) 'THER FACILITIES INVOLVED(8)

MONTH DAY YEAR YEAR $ SEQU N IALjR VISION MONTH FACILITYNAMES DOCKET NUMBER(S)

.NUMBER 'UMBER DAY YEAR N/A 0 5000 2 9 0 9 0 0 0 5 001218 9 0 THIS REPORT IS SUBM ITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR OPERATING Check one or more of the followin 11 MODE (9) 20.402(b) 20.405(c) 50.73(a)(2)(lv) 73.71(b)

POWER LEVEL 20.405(a)(1)(i) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c)

(10) 0 0 0 20.405(a)(1 )(Ii) 50.73(a)(2) (vii) 50.36(c)(2) X OTHER 20.405(a)(1)(ili) 50 73(a)(2)(I) 50.73(a)(2)(vill)(A) (Specify in Abstract below andin Text 20.405(a)(1)(iv) 50.73(a)(2)(II) 50.73(a)(2)(vlii)(B) NRC Form 366A) 20.405(a)(1)(v) 50.73(a)(2)(iII) 50.73(a)(2)(x) Voluntary Report LICENSEE CONTACT FOR THIS LER (12)

M R J. W. Weeks, Shift Technical Advisor AREA CODE COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 13 4 0 7 4 6 5- 3 550 CAUSE SYSTEM COMPONENT MANUFAC- REPORTABLE CAUSF SYSTEM COMPONENT MANUFAC- REPORTABLE TURER TO NPRDS TURER TO NPRDS C C H X Y 0 3 0 Y I I I SUPPLEMENTAL REPORT EXPECTED 14 EXPECTED MONTH DAY Y AR SUBMISSION YES (Ifyes, complete EXPECTED SUBMISSION DATE) NO DATE (15)

ABSTRACT (Limit to 1400 spaces. i.e. approximately fifteen single-space typewritten lines)(16)

On Monday, November 12, 1990, St. Lucie Unit 2 was in Mode 5 after completing scheduled refueling. The 2B Component Cooling Water (CCW) Heat Exchanger had completed testing after refueling outage maintenance had been completed on it. A post-maintenance in service leak test had been performed when a pinhole leak was discovered on the west end of the heat exchanger.

The leak was at the 12 o'lock position at the tube sheet to shell weld joint. Subsequent to the repair of the leak, a second small leak was discovered at the opposite end of the heat exchanger in the same weld joint also at the 12 o'lock position.

The root cause of the event was due to a fabrication defect in conjunction with possible stresses induced due to the retubing of the heat exchanger during the refueling outage.

A sample was taken to metallurgically, examine the west end weld to determine the cause of the leaks. The welds were then repaired, inspected, and hydrostatically tested with no further evidence of leakage. The 2A CCW Heat Exchanger had an In-Service Leak Test performed with no leakage observed.

This Licensee Event Report is being submitted voluntarily for informational purposes. The 2B CCW Heat Exchanger was not in service at the time of the event and was not required for safe shutdown of the reactor. This event is not reportable under the requirements of 10CFR50.73.

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,'ICENSEE fpt,ttttelt tt NRC C~ ttl EVENT REPORT (LER) TEXT CONTINUATION V.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 31504104 EXPIRES 8/31/85 FACILITYNAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YFAR 'EQUENTIAL @ REVISION NUMBER 8 NUMBER St. Lucie Unit 2 0 500 038 9 9 0" 0 0 5 0 0 0 2 OF 0 3 TEXT (If more space is requfred, use additional NRC Form 366A's) (1 7)

DESCRIPTION OF THE EVENT On November 12,-1990, while Unit 2 was in Mode 5 following reactor refueling, a pinhole leak was discovered on the west end of,the 2B Component Cooling Water (EIIS:CC) (CCW) Heat Exchanger. Post-maintenance In-Service Leak testing had been completed when the leak was discovered. The heat exchanger was not in service at the time of the discovery of the leak. The leak was in the weld that joins the tube sheet to the shell. This leak was at the 12 o'lock (top) position.

After completion of this repair and the subsequent Hydrostatic Test, a similar small leak was discovered on the opposite (east) end of the heat exchanger. The leak was also at the 12 o'lock position. After the repair a Hydrostatic Test and a 100% visual inspection was performed on both end welds. Another In-Service Leak Test was performed satisfactorily. The 2A CCW Heat Exchanger was also In-Service Leak Tested on both end welds and no leakage was observed.

CAUSE OF THE EVENT The root cause of the event is due to a preexisting fabrication defect combined with possible stresses induced during the refueling outage. The stresses induced due to retubing of the heat exchanger (which took place during the refueling outage) including the removal and reinstallation of the channel heads, as well as the subsequent hydrostatic testing, may have contributed to overstressing the weldment.

ANALYSIS OF THE EVENT The failure of the 2B CCW Heat Exchanger is not a credible concern because there have been no industry examples of catastrophic failure of these type of heat exchangers. Also, the only credible mechanism for failure is a seismic event. This failure mode has been analyzed and the 2B CCW Heat Exchanger was found to have complied satisfactorily. The most likely degradation of the heat exchanger would be a gradual leak. A fracture mechanics analysis has been performed for this type of degradation and has been found acceptable. The CCW heat exchangers are redundant.

Any failure in one causes the other to be automatically isolated from the faulted one so that system availability is assured.

This Licensee Event Report is being submitted voluntarily for informational purposes. This event is not reportable under 10CFR50.73. The 2B CCW Heat Exchanger was not in service at the time of the event and was not required for safe shutdown of the reactor. Thus the health and safety of the public was not affected by this event.

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U.S. I/UCLEAR REGULATORY COMMISSIOM LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVEO 0MB ko. 31500104 EXPIRES 8/31/85 FACILITYNAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR SEQUENTIAL REVISION NUMBER NUMBER St. Lucie Unit 2 05000389 9 0" 0 0 5". 0 0 p 3OF p3 TEXT (I/more space is required, use additional NRC Form 366A's)(17)

CORRECTIVE ACTIONS

1. A sample of the west end weld was removed and sent to a laboratory for failure analysis.

2. Defective weld material was removed and rewelded in accordance with the disposition of Florida Power 8 Light Company 's Non-Conformance Reports 2-428 and 2-434, and ASME Code Section XI.

3. ASME required inspections of the 2A and 2B CCW Heat Exchangers were performed satisfactorily.

4. The vendor, Yuba Heat Transfer Corporation, was notified of this event.

5. FPL plans to conduct non-destructive examination of the full circumference of the 2B CCW Heat Exchanger shell / tube sheet welds during the next refueling outage to better characterize the condition of these welds.

ADDITIONALINFORMATION MP NENT FAIL RE Tube sheet to shell weld on 2B Component Cooling Water Heat Exchanger manufactured by the Yuba Corporation.

PREVIOUS SIMILAR EVENT There have been no previous LERs at St. Lucie involving weld cracks in the safety related heat exchangers.

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