ML17349A565

LER 92-014-00:on 921125,small Steam Leak Discovered on Abandoned Bellows Rupture Telltale Line on Pressurizer Spray Valve.Caused by Inappropriate Application of Matl from Which Cap Fabricated.Pipe Cap replaced.W/921217 Ltr

ML17349A565
Person / Time
Site:	Turkey Point
Issue date:	12/17/1992
From:	Mowrey C, Plunkett T FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-92-345, LER-92-014, LER-92-14, NUDOCS 9212290173
Download: ML17349A565 (5)

Text

ACCELERATED DOCUMENT DIST VTION SYSTEM REGULAT~ INFORMATION DISTRIBUTIO YSTEM (RIDS)

ACCESS10N NBR:9212290173 DOC.DATE: 92/12/17 NOTARIZED: NO DOCKET FACIL:50-256 Turkey Point Plant, Unit 3, Florida Power and Light C 05000250 AUTH. NAME AUTHOR AFFZLIATION MOWREY,C.L. Florida Power S Light Co.

PLUNKETT,T.F. Florida Power a Light Co.

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 92-014-00:on 921125,small steam leak discovered on abandoned bellows rupture telltale line on pressurizer D spray valve. Caused by inappropriate application of matl from which cap fabricated. Pipe cap replaced.W/921217 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR/ ENCL / SIZE:

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

NOTES:NRR RAGHAVAN,L 05000250 RECIPIENT COPIES RECIPIENT COPIES D ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 LA 1 1 PD2-2 PD 1 1 D AULUCKgR 1 1 INTERNAL: ACNW 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB10 1 1 NRR/DLPQ/L'PEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB SD 1 1 NRR/DST/SICBSH3 1 1 NRR DST/SPLBSD1 1 1 NRR/DST/SRXB 8E 1 1 EG - --E 02 1" 1 RES/DSIR/EIB 1 1 RGN2 FILE 01 1 1 EXTERNAL: EG&G BRYCEgJ.H 2 2 L ST LOBBY WARD 1 1 R NRC PDR 1 1 NSIC MURPHY,G.A 1 1 NSIC POOREiW. 1 1 NUDOCS FULL TXT 1 1 NOTES: 1 1 D

D NOTE TO ALL"RIDS" RECIPIENTS:

F PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESV, ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

L FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 30 ENCL 30

P.O. Box 029100, Miami, FL, 33102-9100 PI-:C 17 1993 L-92-345 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: 92-014-00 Reactor Coolant S stem Pressure Bounda Leaka e The attached Licensee Event Report 250/92-014-00 is being provided in accordance with 10 CFR 50.73 (a) (2) (i) (B) .

3 If there are any questions, please contact us.

Very truly yours, i rrv 'i~~-

T. F. Plunkett Vice President Turkey Point Nuclear TFP/CLM/3k enclosure cc: Stewart D. Ebneter, Regional Administrator, Region II, USNRC Ross C. Butcher, Senior Resident Inspectori USNRCI Turkey Point Plant

$ 90073 9212290173 'F21217 PDR ADQCK 05000250 S PDR ApnP'li i'." FFi 0(v)lf. $ 0a;p~,q1

LICENSEE EVENT REPORT (LER)

FACII ITY NAME (1)

DOCKET NUMBER (2) PACE (3)

TURKEY POINT UNIT 3 05000250 OF 3

TITLE (4) REACTOR COOLANT SYSTEM PRESSURE BOUNDARY LEAKAGE; P IPE CAP ON PRESSURIZER SPRAY VALVE EVENT DATE (5) LER NUMBER(6) RPT DATE (7) OTHER FACILITIES INVOLVED (8)

MON DAY YR YR SEO 6 R( MON DAY YR FACILITY NAMES DOCKET 9 (S) 25 92 92 014 00 12 17 92 OPERATING MODE (9) 3 10 CFR 50.73 a 2 i B PONER LEVEI (10) 000 LICENSEE CONTACT FOR THIS LER (12)

C. L. Mowrey, Licensing OEF Engineer/Analyst TELEPHONE NUMBER 305-246-6204 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER NPRDS7 CAUSE SYSTEM COMPONFNT MANUFACTURER NPRDST PSF X999 SUPPLEMENTAL REPORT EXPECTED (14) NO 0 YES 0 EXPECTED SUBMISSION MONTH DAY DATE (15)

(if yes, complete EXPECTED SUBMISSION DATE)

ABSTRACT (16)

During inspections for the Reactor Coolant System (RCS) overpressure test following a refueling outage, a small leak was discovered. The leak was through a pipe cap on an abandoned bellows rupture telltale line on pressurizer spray valve PCV-3-455B. After an unsuccessful attempt to isolate the leak, an Unusual Event was declared for RCS pressure boundary leakage. The Unusual Event was terminated when the unit entered Mode 5.

The pipe cap was found to have been machined from rolled bar stock, unlike most pipe caps in similar applications which are forged fittings. The leak occurred as a result of gradually weakened ligaments surrounding laminations in the original rolled bar stock. It appears that the pipe cap has been in place since original installation of the pressurizer spray valve.

As corrective action, the pipe caps on PCV-3-455A and PCV-3-455B were replaced with ANSI Class B16.11 forged fittings. Similar pipe caps on Unit 4 will be inspected for replacement during the next outage of sufficient duration. No other non-isolable pipe caps -were found to be fabricated of similar material.

LICENSEE +ENT REPORT (LER) TEXT NTINUATION FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO.

TURKEY POINT UNIT 3 05000250 92-014-00 02 OF 03 I. DESCRIPTION OF THE EVENT On November 25, 1992, Turkey Point Unit 3 was in Mode 3 following a refueling outage. At about 1330, during the performance of" the Reactor Coolant System (RCS) [EIIS:AB] overpressure test, a small steam leak was discovered on an abandoned bellows rupture telltale line on the pressurizer spray valve which taps off the 3B RCS loop (PCV-3-455B)[EIIS:PCV]. The leak emanated from a pipe cap [EIIS:PSF] welded onto the end of the telltale line. An attempt was made to isolate the leak by backseating the spray valve and closing a manual upstream valve. The attempt was unsuccessful.

At about 1825, when it was apparent that the attempt to isolate the leak was unsuccessful, an Unusual Event was declared for pressure boundary leakage.

Technical Specification 3.4.6.2a requires that for any pressure boundary leakage, the plant must be in HOT STANDBY (Mode 3) within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN (Mode 5) within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. Since the leak could not be isolated, it was conservatively declared to be pressure boundary leakage, resulting in the Notification of an Unusual Event (NOUE) . The NRCOC was notified of the NOUE at 1838. Th'e unit entered Mode 5 at 0812 on November 26, 1992 and terminated the Unusual Event.

The original spray valve configuration used a bellows design. Although the telltale line was designed to indicate a bellows failure, this line was capped at Turkey Point Unit 3 during original installation. With the bellows installed, no pressure would be applied to the cap so long as the bellows remained intact. Due to a high failure rate, the bellows were eliminated and live load pa'cking installed. Elimination of the bellows rendered the original intended function of the line obsolete, and made the line and the pipe cap RCS pressure-containing components.

II. CAUSE OF THE EVENT The immediate cause of the Unusual Event was a leak through the end of a welded pipe cap. Since the leak could not be isolated, p'ressure boundary leakages it was considered The root cause of the leak appears to be an inappropriate application of the material from which the cap was fabricated. After the pipe cap was removed, it was destructively examined to determine the nature of the leak point.

Unlike most of the caps in use at Turkey Point Units 3 and 4, which are forged fittings, this cap was found to have been machined from bar stock.,

The root cause of failure was determined to be the presence of excessive laminations in the austenitic stainless steel material. These were original material defects introduced during the manufacture of the rolled bar stock.

The eventual leakage resulted from a gradual weakening of ligaments surrounding the laminations in the defective material while in high pressure (2235 psig) service.

Other than the large concentration of laminations, the material displayed a normal microstructure for an austenitic stainless steel material. There was no evidence of fatigue, stress corrosion cracking, or other active corrosion mechanism.

LICENSEE ENT REPORT (LER) TEXT %SINUATION FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO.

TURKEY POINT UNIT 3 05000250 92-014-00 03 OF 03 I1I. ANALYSIS OF THE EVENT The leak was discovered during a post-refueling pre-startup inspection for gust such leaks, and was ident'ified by very small wisps of steam coming from the cap. Such a small leak had no measurable effect on the RCS leak rate, and therefore was well within the capability of the installed plant systems.

This type of material defect will not result in catastrophic failure, but in small leakage which may gradually increase if unattended. Nevertheless, had the pipe cap suffered catastrophic failure, the size of the break would have been limited to the one-half inch diameter of the telltale line. Schedule 80 piping of size one-half inch nominal pipe size translates into a break area of 0.234 square inches. This size of break is bounded by the small break Loss Of Coolant Accident analyzed in the Updated Final Safety Analysis Report, Section 14.3.2.2, in which the limiting small break size is given as a two inch diameter cold leg break (3.142 square inch area) .

IV. CORRECTIVE ACTIONS The failed pipe cap, as well as the one installed on valve PCV-3-455A, was removed and replaced with appropriate ANSI Class B16.11 pipe caps forged from ASTM A312 Type 316 material.

2. The pipe caps on valves PCV-4-455A and PCV-4-455B will be inspected and/or replaced during the next outage of sufficient duration (next refueling outage, at the latest) .

3. A review was performed to identify other non-isolable RCS pipe caps fabricated from a similar material. No other pipe caps were found to be fabricated of a similar material.

4. A Drawing Change Request has been generated to add the pipe caps to the Bill of Materials on the vendor drawing, V. ADDITIONAL INFORMATION None.