ML18040A261

Submits Response to 970516 Telcon RAI Re Restart Following Repair of Weld Overlay.Calculation Re Size of Overlay,Encl

ML18040A261
Person / Time
Site:	Nine Mile Point
Issue date:	05/19/1997
From:	Mccormick M NIAGARA MOHAWK POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML17059B563	List: ML17059B562 ML17059B568 ML18040A261
References
GL-88-01, GL-88-1, NMP1L-1222, NUDOCS 9705280085
Download: ML18040A261 (13)

Text

CATEGORY 1 REGUDATOI ENEORMA.TON DESTRTBUTiON 3TEM (RZDS)

I ACCESSION NBR:9705280085 DOC.DATE: 97/05/19 NOTARIZED: NO DOCKET ¹

. FACI'50-220 Nine Mile Point Nuclear Station, Unit 1, Niagara Powe 05000220 AUTH. NAME AUTHOR AFFILIATION MCCORMICK,M.J. Niagara Mohawk Power Corp.

RECIP.NAME RECiPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Submits response to 970516 telcon RAI re restart following repair of weld overlay. Calculation re size of overlay,encl.

DISTRIBUTION CODE: A018D COPIES RECEIVED:LTR ENCL SIZE:

TITLE: GL 94-03 Intergranular Stress Corrosion Cracking of Core Shrou s in B NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL HOOD,D 1 1 INTERNA LE CENTER 01 1 1 NRR/DE/EMCB 1 1 NRR D K 1 1 NRR/DRPM/PECB 1 1 NRR/DSSA/SRXB 1 1 RES/DET/EMMEB 1 1 EXTERNAL: NRC PDR 1 1 NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM OWFN 5D-5(EXT. 415"2083) TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER'F COPIES REQUIRED: LTTR . 8 ENCL 8

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NIAGARA MOHAWK C EN E RATION NINE MILE POINT NUCLEAR STATION/LAKEROAD, P.O. BOX 63, LYCOMING, NEW YORK 13093/TELEPHONE (315) 349 2660 FAX (315) 349-2605 BUSINESS CROUP MARTINJ. McCORMICKJR. P.E.

Vice President May 19, 1997 Nuctear Engineering NMP1L 1222 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 RE: Nine Mile Point Unit 1 Docket No. 50-220

Subject:

Generic Letter (GL) S8-01, "NRC PosMon on IGSCC in BWR AustenMc Stainless Steel Piping Gentlemen:

By letter dated May 15, 1997, Niagara Mohawk Power Corporation (NMPC) indicated that a through-wall pin hole leak at a bimetallic weld (33-FW-22) in the Nine Mile Point Unit 1 (NMP1) Reactor Water Cleanup System (RWCU) had been discovered. This leak resulted from a 7/16" axial crack that was classified as Intergranular Stress Corrosion Cracking (IGSCC). NMPC proposed to repair this weld by performing a weld overlay to restore the structural strength of the weldment. The purpose of that letter was to request NRC approval of the weld overlay repair.

Based on information provided in our May 15, 1997 letter and by telephone conversation on May 16, 1997, the NRC approved restart of NMP1 following repair of the weld.

Additionally, the NRC requested that additional information be provided via written communication. This letter provides that additional information.

Generic Letter (GL) 88-01, "NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping", was issued by the NRC on January 25, 1988 to make recommendations regarding the mitigation and identification of IGSCC. NMPC provided responses to GL 88-01 in the 1988 through 1991 time frame. By letter dated May 15, 1990 and June 24, 1991 the NRC issued its Safety Evaluations (SE) for GL 88-01 based on our responses. Included in the NRC's SE dated May 15, 1990 is the following statement:

"As a reminder, GL 88-01 requires that ifany cracks are identified that do not meet the criteria for continued operation without evaluation given in Section XI of the Code, NRC approval of flaw evaluations and/or repairs in accordance with IWB-3640 and IWA-4130 is required before resumption of operation. Please note that weld overlay iE repair is considered as a non-Code repair, which requires NRC approval."

PDR ADQCK 05000220

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Page 2 Since this SE was issued, Code Case N-504, "Alternate Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Section XI, Division 1", was written and endorsed by the NRC (i.e., referenced in Regulatory Guide (RG) 1. 147). Code Case N-504 finds that the "acceptability of a defect in austenitic stainless steel piping may be established in accordance with IWB-3640 by deposition of weld reinforcement (weld overlay) on the outside surface of the pipe", provided that certain requirements are met. As stated in the May 16, 1997 telephone conversation, the weld overlay repair design for the RWCU system meets the requirements of N-504 with the following exceptions from items (f)(1) and (g)(2)(3) of the Code Case:

(f)(1) The Code Case requires that the full thickness length extends "axially at least 0.75 KRt beyond each end of the observed flaws where R and t are the outer radius and nominal wall thickness of the pipe". Because of physical restrictions, the overlay was extended as far as possible, until it butted up to the nozzle to heat exchanger shell weld. This resulted in less than a 0.25 inch reduction of the weld overlay length on the stainless steel end of the weld (calculated length, is 1.25 inches, achieved length is approximately 1 inch). Full overlay length was achieved on the opposite side of the crack tips.

(g)(2) An evaluation of flaw growth due to fatigue; as well as shrinkage effects on (g)(3) welds and components in the system affected by the weld reinforcement, willbe performed. These evaluations willbe completed approximately one month from plant restart and the results of the evaluations submitted to the NRC within the following 60 days.

It was also noted that an in service leak test in accordance with ASME Section IWA-5000 (the original code of construction for this system was ASA B31.1-1955) would be performed with the system at nominal operating pressure. (This test has been performed and was considered appropriate as this weld is non-safety related and outside the ASME Section XI boundary for pressure testing. An in service leak test in lieu of a hydrostatic test is sufficient to detect any leaks through the repaired area).

Although not specifically discussed in our May 16, 1997 telephone conversation, alternate methods of meeting elements of Code Case N-504 were used. The RWCU system is designed as non-safety related and meets ANSI B31.1. NMPC will meet Code Case N-504, items (c),

and (k) by the use of alternate methods as follows:

(c) The performance of a liquid penetrant examination prior to the deposition of weld reinforcement was not performed because the pinhole is greater than 1/16" which would require the complete overlay defined in c(2) to be performed.

Therefore, a weld overlay was performed in accordance with c(2). The area to be reinforced by overlay was first prepared by application of an initial weld

Page 3 layer which was then examined as required by item (d) of the Code Case. The application of the initial layer effectively seals any potential indications in the overlayed area.

(k) Pipe supports near the repair area (primarily spring hangers) did not receive a VT-3. Because of the relatively smaH size of the overlay, no notable change in spring hanger position occurred. These pipe supports were marked and monitored for any relative change in spring setting from the application of the weld overlay. No recordable changes occurred. Because this is a non-ASME XI boundary, these pipe supports have not been visually preservice examined.

No physical anomalies in the pipe supports were observed during the comparison in spring support settings.

The subject weld (33-FW-22) is a non-safety related, non-ASME Section XI weld. As this Code Case is written for "Alternate Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Section XI, Division I", under strict compliance with the Code Case, it would not be applicable for this weld. Because the weld is not an ASME XI Class 1, 2, or 3 weld, neither an ASME Section XI repair plan nor a NIS-2 report will be generated for this repair.

However, as previously discussed, the NRC s Safety Evaluation regarding our position on GL 88-01 indicated that weld overlay repairs would require NRC approval. Accordingly, as required by the NRC's Safety Evaluation, NMPC requested approval of this repair. NMPC is not seeking approval under the requirements of 10CFR50.55a A diagram of the overlay repair and a description of the materials being used are provided in enclosed Figure 1. The analysis used to determine the size of the overlay is included as .

Very truly yours, Martin J. McCormick Jr.

Vice President Nuclear Engineering MJM/JMT/cmk Attachments XC: Mr. H. J. Miller, NRC Regional Administrator Mr. B. S. Norris, Senior Resident Inspector Mr. S. S. Bajwa, Acting Director, Project Directorate I-l, NRR Mr. D. S. Hood, Senior Project Manager, NRR Records Management

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33-FW-22 WELD OVERLAY REPAIR WELD OVERLAY 368 DEGREES AROUND EXISTING NOZZLE/PIPE APPROX. 2 I/2'IDE X MIN. 5/16'HICK.

WELD FILLER METAL TYPE E389L FOR INITIAL PASS 6'CH.88 PIPE 5/16'PPROX. LAYER (MIN. I/16'HK.). SUBSEOUENT LAYERS ALSO SEAMLESS TYPE E389L WELD MATERIAL TO YIELD A SECOND A186, GR. B LAYER (MIN. I/4'HK.).

'TOE'F EXISTING DISSIMILAR METAL WELD 11/4'IPE. WELD BETWEEN NOZZLE ANO STAINLESS STEEL SIDE OF WELD 33-FW-22 (E389) APPROX.

3/4'EAT T OIBTRHCE OETERHIHEO BY AHOUHT OF WELD REOUIREO TO TIE INTO EXISTING EXCHANGER NOZZLE WELD BETWEEN NOZZLE AND HTX SHELL 6'BW 384 SS EXISTING WELD BETWEEN PIN-HOLE LEAK Hl'X SHELL ANO NOZZLE HEAT EXCHANGER SHELL

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EI V NAGARA m LJ MOHAvnc NUCLEAR ENGINEERING Page Total ~

Last ~JR Next ~l NINE MILE POINT NUCLEAR STATION Unit (1, 2 or 0=Both): 1 Discipline: STRUCTURAL Caicuhtke No.

RWCU WELD 33.FW-22 OVERLAYDESIGN S14-33 M009 (Sub)system(s) Building Floor Elev. Index No.

33 RX 261 S14 Originator(s)

RANDYTRENCH (MPR)

Checker(s) /Approver(s)

PAUL KNITTLE PR JIM NESTELL MPR Acct/o< 4a Cc ~ao+ ~at'P<lt7 Des gn Rev Descrl tlon Chan eNo. B Date Chk Date A Date 0 INITIALISSUE K 5/~

P'EA PR/E / Fog- ~/R s/~~~a/.g Computer Output/Mlcrofllm Filed Separately (Yes / No / NA): NO Safety Class (SR / NSR/ Qxx): NSR Superseded Document(s): NONE Document Cross Reference(s) - For additional references see page(s): S1~3M008 Ref Doc No Document No. T Index Sheet Rev C-26852-C DR S14 General Reference(s):

SEE SECTION 6.0 Remarks:

WELD OVERLAY REPAIR OF SUSPECTED IGSCC Confirmation Required (Yes / No): No Final Issue Status File Location Operations Acceptance See Page(s): (APP /FIO/VOI ): APP ( Calc/Hold): Gale Required ( Yes/No): No Evaluation Number(s) / Revision: Component ID(s) / EPN(s) / Line Number(s):

Copy of Applicability Review Attached (Yes / N/R)? N/R NONE Key Words: SSFLAW, WELD OVERLAY DESIGN, RWCU FORMAT S NEP-DES48-F0140