05000265/LER-1983-021, Revised LER 83-021/01T-5:on 831028,ultrasonic Exams of Large Bore Stainless Steel Pipe Welds Identified 11 Welds W/Crack Indications.Caused by Intergranular Stress Corrosion Cracking.Weld Overlay Performed

Revised LER 83-021/01T-5:on 831028,ultrasonic Exams of Large Bore Stainless Steel Pipe Welds Identified 11 Welds W/Crack Indications.Caused by Intergranular Stress Corrosion Cracking.Weld Overlay Performed

ML20087G700
Person / Time
Site:	Quad Cities
Issue date:	02/28/1984
From:	Dunesia Clark, Kalivianakis N COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
LER-83-021-01T, LER-83-21-1T, NJK-84-68, NUDOCS 8403200106
Download: ML20087G700 (7)

LER-2083-021, Revised LER 83-021/01T-5:on 831028,ultrasonic Exams of Large Bore Stainless Steel Pipe Welds Identified 11 Welds W/Crack Indications.Caused by Intergranular Stress Corrosion Cracking.Weld Overlay Performed

Event date:
Report date:
2652083021R00 - NRC Website

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[TTTl I ouring the Quad-Cities Unit Twc Refuel Outage, ultrasonic examinations of large bore l

[7771 l stainless steel pipe welds performed to comply with the requirements of the NRC l All of the gl lGSCC Inspection Order identified 11 welds as having crack indications. l lO i s , g welds were Iccated on the Reactor Recirculation System piping. The slow growth rate,j iO is l l typical with tSis type of indications, combined with the reduced allowable j l 0 l 71 l Contalnment leakage .* ate would have been sufficient to readily identify any possible l

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42 43 l4401214 l 01@ 47 CAUSE DESCfuPTION AND CORRECTIVE ACTIONS h l i l 0 l l The cause of this occurrence is postulated as beinq Intergranular stress corrosion l i i l cracking. The weld repai r program involved either performino a weld overlav or i gl leaving the weld in its present condition. Induction Heat Stress improvement (IHSI) l

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• ID/TS8-R I. UER NUMBER: LER/R0 83-21/01T-5 II, LICENSEE NAME: Commonwealth Edison Company Quad Cities Nuclear Power Station III, FACILITY NAME: Unit T o IV , DOCKET NUMBER: 050-265 V. EVENT DESCRIPTION:

On September 4,1983, Quad Cities Unit Two was shut down in order to begin the Cycle 6 refueling outage. During the outage, numerous inspections of the Primary Coolant System were performed as required by the N,R.C. IGSCC Inspection Order. The ultrasonic testing was performed by Lambe rt, McGill and Thomas, Incorporated personnel and the results were reviewed by the Car.monwealth Edison Level III examiner. The results Indicated that eleven welds on large bore stainless steel pipe were Identified to contain linear indications in the heat-af fected zone. All of the w31ds we re located on the Reactor Recirculation Sys t em. A complete list of af fected welds, including a description of the indications and the final disposition, can be found on At tachment 1.

An additional eleven welds in the Reactor Recirculation System and the Residual Heat Removal (RHR) Shutdown Cooling Suction piping were also found to contain linear Indications. These welds were inspected as part of the N,R.C, I.E, Bulletin 83-02 and are reported under LER/R0 83-20/01T, VI, PROBABLE CONSEQUENCES OF THE OCCURRENCE The prof ble consequences of this occurrence were minimal. Crack indica tions 'his type tend to propagate at a slow rate. Therefo re, a 100 percen. ugh-wall crack could be easily detected using existing Primary Cont leakage monitoring systems before a complete failure would occur. '

the Operatlog Cycle, the allowable containment leakage rate L. 'n reduced in order to expedite the investigation of potential leakage a stainless steel piping. Ncne of the indications discovered extendea completely through the weld. Safe operation of the Reactor was not jeopardized as a result of this occurrence.

VII. CAUSE The exact cause of the crack Indications has not been determined; but it is postulated that intergranular stress corrosion cracking is the probabic mode of failure. The normal heat generated by welding causes a heat-af fected zone at the weld to piping interface. This, combined with coolant impu rities, high operating temperatures, and stresses experienced in the weld area, are factors encountered in the Reactor Recirculation System which are mechanisms necessary fot Intergranular stress corrosion cracking to occur.

The stainless steel piping was f abricated by the Dravo Corporation.

Type A358, Grade TP 304. The pipe fittings are Type A 403 Crade WP 304 The stainless steel used in all the original Recirculation System pipe and fittings contained carbon contenta between 0.05 and 0.08 pe rcent.

VII 1. CORRECTIVE ACTION The crack Indication evaluation and repair criteria determination was performed by NUTECil Engineers, Inc. Indications were evaluated based upon Indication depth, length, direction, and applied stresses.

Induction IIcat Stress Improvement (IHSI) was performed on many welds, both with and without crack indications in order to reduce weld residual stress. As a general rule, circumferential indications with a length greater than 120 degrees of the pipe circumference and/or a depth of greater than 25% of the pipe wall thickness were repaired by applying a weld overlay. All axial Indications were repaired by weld overlay.

All analyses were performed to the guidelines specified in the ASME Boiler and Pressure Vessel Code, Section XI, Paragraph IWB-3640,

" Acceptance Criteria for Austenttic Steel Piping." See Attachment 2 for a typical evaluation segrence.

Additional Inspections we re perfonned on welds 02F-F6, 02J-F6, 02AS-F14, 02BS-F7, and 02BS-S12 (ref. LEP/R0 83-20/0IT) to determine the actual size of the Indications. Second and third party inspections by Independent Testing laboratory and Universal Testing Lab. using the Shear Wave technique confirmed the original evaluation. A newer ultrasonic test technique, Identified as ID Creeping Wave, was also used by UTL.

The results of this inspection, contrary to the other inspecticn results, indicated that ne cracks existed in these welds.

n sample plug was then cut out of# weld 02BS-S12 to perform further analyses. The plug was examined visually and by dye penetrant testing but no evidence of a crack could be found. The plug was then sectioned, polished, etched and examined microscopically. No cracks were found on the sample. The renalnder of the weld was examined by radiography and the pipe I.D. was visually inspected with a borescope. Results of the sample plug and weld Inspections provided conclusive evidence that no ICSCC cracks existed in this weld.

The repair program consisted of either performing a weld overlay or leaving the weld as-is. All welds containing Indications that were l 1ef t as-is had IHSI performed on them. Four welds were repaired using l

weld overlay. The length and thickness of each overlay differed, depending upon the indication size, analysed stresses and pipe geometry.

A more detailed description of the Indication evaluation and repair

{ program can be found in a Commonwealth Edison letter from B. Rybak to

! Mr. Harold R. Denton, "Qned Cities Station Unit 2 Weld Inspection Results, NRC Docke t No. 50-265", dated January 27, 1984 Each weld overlay was dye penetrant tested; and an ultrasonic examination was performed to verify bonding between the base metal and weld material. A post-examination of each weld treated by IHSI was pe rformed by ult rasonic testing. Prior to the reactor si.artup, the i

l entire Recirculatlon Systen was hydrostatically tested in conjunction with the reactor vessel hydrostatie test at 1.1 times the system nominal operating pressure.

LER/R0 83-21/0lT Quad-Cities Station Indication Description & Repair Flaw Characterization (l)

Pipe Crack Max Weld Weld ID Location Diameter Type __ Depth Length Location Disposition IHSI'd 02 F-F6 F Recirc Riser Pipe to Pipe 12" Circ (1) 15% 360 Int Upstream Pipe Overlay Yes 02J-F6 J Recirc Riser Saddle to Pipe 12" Circ (1) 15% 15 0" Pipe Side Overlay Yes 02M-S3 M Recirc Riser Elbow to Pipe 12" Circ 13% 1.0" Pipe Side Leave As-Is Yes 30% 1.5" Elbow Side 02M-S4 M Recirc Riser Pipe to Elbow 12" Circ 9% 0.5" Elbow Side Leave As-Is Yes 02AS-S4 A Loop Suction Elbow to Pipe 28" Circ 13% 21.0" Elbow Side Leave As-Is Yes (total) 11% 4.0" Pipe Side 02AS-S6 A Loop Suction Pipe to Pipe 28" Circ 21% 7.0" Upstream Pipe Leave As-Is Yes 02AS-S9 A Loop Suction Valve to Elbow 28" Axial 10% 0.5" Elbow Side Overlay Yes. I Circ 22% 24.0" Elbow Side (total) 02AS-SI2 A Loop Suction Elbow to Pipe 28" Circ 9% 3.0" Elbow Side Leave As-Is Yes l (total)

, Circ 14% 8.0" Pipe Side l

'02AS-F14 A Loop Suction Pipe to Elbow 28" Circ (1)(2) 30% 43.0" Pipe Side Leave As-Is Yes 02BS-F7 8 Loop Su: tion Valve to Pipe 28" Circ (1)(2) 16% 3600 Int Pipe Side Overlay Yes 02A-S101 Ring Header Pipe to Cap 22" Circ 26% 4.0" Cap Side Leave As-Is Yes l

NOTE: (1) Flaw characterization based on composite of LMT/ITL resulis.

(2) Additional inspection by UTL and plug sample of 02BS-512 confirms that no flaw actually exists.

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TYPICAL FLAW DISPOSITION SECUENCE '

. (N Commonwealth Edison Ound Citi;s Nuctar Power Station 22710 206 Avenue North t Corcova, Illinois 61242 l Telephone 309/654-2241 NJK-84-68 l Februa ry 28, 1984 J. Keppler, Regional Administ rator Of fice of Inspection and Enforcement Region iIi U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137

Reference:

Quad-Cities Nuclear Power Station Docket Number 50-265, DPR-30, Unit Two Appendix A, Section 6.6.B.I.c Enclosed please find Reportable Occurrence Nmnber (RO) 83-21/0lT-5 for Quad-Cities Nuclear Power Station. Previous revisions to this Reportable Occurrence have identified welds containing linear indications found during the Inservice Inspection required by the inspection order of all large bore stainless steel piping. This revision identifies the final disposition of these indications.

This report is submitted to you in accordance with the requirements of Technical Speci fication 6.6.B.I.c; an abnormal degradation discovered in the Reactor Coolant Pressure Boundary.

Respectfully, COMMONWEALTH ED! SON COMPANY QUAD-CITIES NUCLEAR POWER STATION

/ l ss N. J. Kallvianakis Station Superintendent NJK:DGC/bb Enclosure cc B. Rybak A. Morronglello INPO Records Center en O r

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