ML20202F893

Rev 0 to SIC-98-009, Evaluation of Limiting Flaws for Structural Adequacy in CRDM Repair Adapter Plug Fillet Weld Evaluation at Prairie Island Unit 2

ML20202F893
Person / Time
Site:	Prairie Island
Issue date:	02/12/1998
From:	STRUCTURAL INTEGRITY ASSOCIATES, INC.
To:
Shared Package
ML20202F889	List: ML20202F883 ML20202F893
References
CON-NSP-27Q SIC-98-009, SIC-98-009-R00, SIC-98-9, SIC-98-9-R, NUDOCS 9802200011
Download: ML20202F893 (10)

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STRUCTURAL CALCULATION FILE No: NSP-27Q-301 "NN PACKAGE PROJECT No: NSP-27Q Associates, Inc.

PROJECT NAME: CRDM Repair Adapter Plug Fillet Weld Evaluation CLIENT: Northern States Power CALCULATION TITLE: Evaluadon of Limiting Flaws for Stmetural Adequacy in CRDM Repair Adapter Plug Fillet Weld Evaluation at Prairie Island Unit 2 i-PROBLEM STATEMENT OR OBJECTIVE OF THE CALCULATION:

Demonstrate that the through-wall flaw si7s detectable by visual exarnination is less than the critical flaw size for both axially and circumferentially or':nted flaws.

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1.0 INTRODUCTION

in support of the use of visual r=tration rather than dye penetrant examination of tbc completed fillet weld for the adapter plug at Prairie Island Unit 2, Structural Integrity Associates (SI) performed an evaluation to determine the critical flaw size in the repaired location. The purpose of this analysis is to demonstrate that a through-wall flaw could be detected by visual examination having a size which is sufficiently smalle- than the critical flaw size, thus assuring sufficient safety margins. NSP wi!! review the critical flaw sizes determined in this calculation to confimi that the resulting sizes are detectable with margin by the visual technique.

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20 GEOMETRY The design geometry of the repair is illustrated in Figure 1. For the purpose of the present evaluation, the component was modeled as a pipe with outside radius equal to the distance from the drive centerline to the outer most fillet weld radius (3.44 inches). The wall thickness of the cylinder was made equal to the minimum anticipated fillet weld thickness (0.44 inches with effective thickness of 0.265 inch), as shown on Figure 1. This geometry is considered a -

reasonable representation of the actual design geometry. Through wall axial and circumferential -

I flaws were evaluated. The model geometry is shown in Figure 2.

3.0 APPLIED STRESSES I

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For conservatism, the applied stresr as assurned to act as a membrane stress at the Code allowable membrane stress magnitude (P. = S.). No distinction was made between the hoop and axial directions in this regard, although italistically, the axial direction ..iould be closer to half of this value and is primarily composed of stress due to pressure. Bending stresses are small compared to the membmne stress since no loads, which would induce primary bending stresses, are present at this locatior.

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• MAT ' RIAL PROPERTIES

'1he allowable stress, S,,, was taken to be 16.2 kai at 650' F which is typical of 304 stainless steel.

The Alloy 625 to be used in the fillet wefd has a significantly higher allowable stress at this temperatue so use of the stainless steel value is conservative. A Jow stress for this component was taken as ?S, per ASME Code Section XI Appendix C [1].

5.0 , AM AIXrICAL APPROACH L

4 The : Limit load (net section collapse) method is used to detemene the allowable through-wall flaw leng h at the Silet weld location. LEFM is not necessary at this locadon because the fluence is I

well below that required to significantly reduce the material fracture toughness. This me** iis described in ASME Code Section XI Appendix C [1].

Two cases were studied. These were:

1. Through wull axial flaw: Limit load.

2. Through wallcircumferentialflaw: Limitload.

No Code safety margins were included in this evaluadon, since the objective is to get a reasonable view of the relationship between detectable and critical Daw sizes.

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6.0 RESULTS These cases follow the methodology presented in ASME Section XI,IWB-3641 and Appendix C (1).

' 6,1 Thmugh Wall Axial Fisw: Limit Load The I progrwn pc-CRACK [2] was used to perform the analysis. The pe-CRACK results are a ed in Appendix A to this report. He conclusion is that an axial flaw could be at least 4.17 inches long before leading to incipient collapse. This is much longer than is physically achievable, since cracking would be expected to be confined to the weld material and vicinity, which, in the axial direction, extends less than 1 inch.

6.2 Through Wall CircumferentialFlaw Limit Load The analysis was based on the methods of Section XI Appendix C. The EPRI program DLL [3]

was Iso used to perform the analysis, ne analysis assumed a through-wall circumferential flaw, and detr-mined the critical flaw length using limit load techniques. The conclusion is that such a flaw could be 131* around the cylinder before reaching a critical size. nis corresponds to a flaw approximately 6.95 inches long. Computer output is included in Appendix B of this report.

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7.0 CONCLUSION

S The above results demonstrate that, under a variety of conservative assumptions, the critical flaw size predicted for the repair geometry is in all cases significantly longer than the flaw length which is expected to be detectable by a visual examination under magnification, as proposed by NSP. This will be confirmed by NSP.

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• REFERENCES .

1. ASME Boiler and Pressure Vessel Code, Secilon XI, Appendix C,1989 Edition, No Addenda .

2. Structural Integrity Associates, pe-CRACK, for Windows, Version 3.0, March 1997.

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3. BWR Vessel and Internals Project,"BWR Core Shroud Distributed Ligarnent Length (DLL) Computer Program (BWRVIP 20), Electric Power Research Institute, APRI AP-107283, De< ember 1996 P

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. ATTACHMENT 2

SUMMARY

OF CAMERA TESTING WELDING SERVICES INCORPORATED 1

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June 21,1995 Mr. Dick Cooper Northe:rn States Power Corupany 1717 Wakonade Drive East Welch.MN $5089 FAX: 612-330-7603

SUBJECT:

Prairic Island Nuclear Plant WS1 Reference No.: 35049-2

Dear Mr. Cooper:

Per your request, we have perrocned several tests to evaluate the tapabilities of the camera system used in the performance of the wcld repair of Pndrie Island's CRDM Seals. The Intent of this testing is to provide data to be used by NSP to cvaluate the adequacy of this camera for the performan:e of adeounte visual inspection of the wcld overlay. The testing described was not performed as a safety related procedure. %e testing was performed as follows:

1. The video front end of the WSI weld head was connected to a VCR and monitor of tbc same make and model as the system used on site.

2. A mockup of a canopy seal housing dmilar in configuration to the Prairie Island design was ovedayed in a similar conGguradon as the repair performed at the site. A .0005 inch diameter wire and a .001 inch diamete wire each, .4 inches long, were taped to the surface of the weld overlay on the housing.

3. Tbn two wires were filmed using the weld besd front end, and the weld head lighting for illumination.

4. WSl's site QC representative, Gary Caul reviewed the tape and was able to see bcth wires on the surface of the weld.

A copy of the tape, samples of the two wires used, and additional camera information ate included with this letter for your review. Please !ct me know if you need additional information.

Sincerely, 9A 6./2A Pedro E. Amador

" SeniorProjectManager

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o ATTACHMENT 3 P

CONTROL ROD LOCATIONS t

1 2 3 4 5 6 7 8 9 10 11 12 13 i A A B RCCA RCCA B C RCCA RCCA RCCA C D. RCCA RCCA D ,

E RCCA RCCA E RC F RCCA RCCA stCCA RCCA 'F G RCCA RCCA RCCA G RC RC

.H- RCCA .RCCA RCCA RCCA H l- RCCA RCCA I RC J RCCA RCCA J K RCCA RCCA RCCA K L RCCA RCCA L M M 1 2 3- 4 5 6 7 8 9 10 11 12 13 ISM 3nSEALREO4.00C

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