ML20247E635

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Rev 1 to GE-NE-B13-01935-LTR, Jet Pump Riser Welds Allowable Flaw Sizes Ltr Rept for Vermont Yankee
ML20247E635
Person / Time
Site: Vermont Yankee Entergy icon.png
Issue date: 04/30/1998
From: Caine T, Kaul M, Mallard L
GENERAL ELECTRIC CO.
To:
Shared Package
ML20247E613 List:
References
GE-NE-B13-01935, GE-NE-B13-01935-LTR, GE-NE-B13-1935, GE-NE-B13-1935-LTR, NUDOCS 9805180406
Download: ML20247E635 (11)
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Text

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. VERMONT YANKEE NUCLEAR POWER CORPORATION 4

Docket No. 50-271 BVY 98-67 l

Attachment 2 l

Vermont Yankee Nuclear Power Station Jet Pump Riser Circumferential Weld Inspections Jet Pump Riser Welds Flaw Handbook l

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l May 1998

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9905180406 990504 PDR ADOCK 05000271 P PDR

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GENuclearEnergy TEC1INICAL SERVICES GE-NE-B13-01935-LTR, Rev.1 GE Nuclear Energy April 1998 175 Curtner Avenue, San Jose, CA 95125 JET PUMP PlSER WELOS ALLOWABLE FLAW SIZES LETTER REPORT FOR VERMONT YANKEE April 1998 Prepared for Vermont Yankee Nuclear Power Corporation Prepared by GE Nuclear Energy 1

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GEN: clear Exergy GE-NE-B13-01935-LTR. Rev. I JET PUMP RISER WELDS ALLOWABLE FLAW SIZES LETTER REPORT FOR VERMONT YANKEE April 1998 Pret,ered by: sd 4/d-M Lerond Mallard, Engineer '

Structural Mechanics & Materials 1

Verified by: A . we Mdiaraj Kaul, Principal Engineer Structural Mechanics & Materials Reviewed by: bbM Tom A. Caine, Manager Structural Mechanics & Materials 1

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'3 GENcclear Energy - GE-NE B13-01935-LTR, Rev. I

1. Purpose / Objective The objective of this letter report is to provide maximum allowable flaw lengths forjet pump riser pipe circuniferential welds, in order to evaluate and accept indications that may be found during the 1998 outage for Vermont Yankee. Figure 1 is a schematic showing the welds of interest which are labeled Weld 1, Weld 2 and Weld 3.
2. Methods The methodology and procedure used in performing the jet pump riser pipe weld flaw evaluation is in accordance with BWRVIP-41 (Reference 1) and the steps are outlined below.
1. Determine the loading and load combinations as specified in BWRVIP-41 and calcul..te the membrane and bending stresses considering the load combinations.
2. Create a SAP 4G07V (Reference 2) finite element model for the jet pump riser. Anchor connection points are the recirculation inlet nozzle, shroud support plate and riser brace.
3. Use the limit load methods of BWRVIP-41 to determine the allowable flaw lengths.
4. Calculate IGSCC crack growth for eighteen months (12,000 hrs) cycle based on a growth rate of 5x104inch / hot hour.
5. Calculate the crack lengths at which fatigue crack growth due to vibration initiates. This is done by calculating the stress intensity factor (AK) due to flow inductd vibration and comparing it to the threshold stress intensity (Alg) for fatigue crack growth.

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GENxcle:r E:ergy GE-NE-B13-01935-LTR. Rev. I

3. Assumptions ,
1. The calculations are based on one flaw per riser. However, synergistic effects of multiple flaws in one riser are negligible and would not affect the results of this analysis.
2. Fatigue due to thermal stresses is negligible due to minimal temperature differentials during normal or transient conditions.
3. The jet pumps a : =u=d to be in the as-designed configuration because the vibration data on which the fatigue evaluation is based was taken from a new plant in startup. To account for issues such as jet pump fouling and restrainer bracket set screw gap, a l

conservative value of AK threshold, 5.0 ksi-Vin, is used in the vibration fatigue evaluation.

4. Allowable flaw lengths are conservatively calculated assuming all welds are flux (SAW)

. welds.

4. Loading and Load Combinations 4.1 Loads I Applied loads on the jet pump assembly are described in section 4.1 of BWRVIP-
41. The following loads are not applicable or have magnitudes that are negligible j at Vermont Yankee:

i Operating Basis Earthquake Displacements OBED Safe Shutdown Earthquake Displacements SSED Safety Relief Valve SRV Annulus Pressurization AP Condensation Oscillation CO Chugging CHG Displacements during LOCA thermal effects LOCAD 3

GEN:: clear ExerEY GE-NE-Bl3-01935-LTR. Rev.1 4.2 (oad Combinations The load combinations are consistent with the Vermont Yankee FSAR and are in accordance with section 4.2 of BWRVIP-41 except

. The BWRVIP load combination (2) is enveloped by load combination (3) for normal / upset condition. )

. Load combinations (1) through (5) are not applicable for the Emergency / Faulted conditions.

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5. Structural Mechanics Evaluation The limit load methodology as described in section 5.1.1.1 of BWRVIP-41 was used in calculating the allowable flaw lengths. The results based on the application of this methodology are given as allowable flaw lengths.

5.1 Allowable Flaw Length Calculation The flow stress was taken as 3S (S,=16.9 ksi for Type 304 stainless steel at 550 F). As specified in Reference 3, safety factors of 2.77 for the normal / upset conditions and 1.39 for the emergency / faulted conditions, respectively, were used. I The calculated values of the end-of-cycle allowable flaw lengths are tabulated in the following table.

Maximum Allowable Flaw Lengths Based on Outside Diameter Weld Flaw Length (inch)

Weld 1 16.41" Weld 2 18.70" Weld 3 19.58" These allowable values do not consider the crack growth due to IGSCC, fatigue, or NDE uncertainty but are considered in the calculations of the adjusted flaw ,

sizes. l 1

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GENuclear Energy GE-NE-Bl3-01933-LTR. Rev.1 5.2 Crack Growth Evaluation The maximum required crack growth rate translates into a crack length increase per eighteen months cycle of approximately 0.60 inch at each end of an indication.

Fatigue growth due to flow induced vibration (FIV) is also calculated as per section 5.1.1.2 of BWRVIP-41. With a characterized crack, the stress intensity factor (AK) is computed and compared to the threshold stress intensity factor (AlQ. At (AK) values below AK,3, fatigue growth is neglected. For 304 stainless

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steel, Reference 3 reports a AKn i value of 5.5-6.0 ksiVin. A threshold value of 5.0 ksiVin is used here to cover vibration loading uncertainties. The allowable crack size due to FIV was based on the stress intensity calculation method described in Reference 3. The smallest calculated EOC crack size for the three locations is 5.4 inches.

5.3 Evaluation Procedures of Riser Cracks Flaw Sizes After one Cycle Location Measured IGSCC NDE Adjusted Allowable Allowable of size of Growth ") uncertainty Size Flaw Size Flaw Size Indication Indication m

[ inches] (Limit (FIV)

Load)

Weld 1 A" 1.2" 0.38" A+1.58 16.41" 5.4" Weld 2 E" 1.2" 0.38" B+1.58 18.70" 5.4" Weld 3 C" 1.2" 0.38" C+1.58 19.58" 5.4" (1) Includes crack growth for 12,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />.

(2) Includes NDE uncertainty per EPRI qualification data.

If the adjusted flaw length is less than the allowable flaw size (FIV) then the flaw found is acceptable for continued operation without any modification for one cycle.

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c GEN: clear Exergy GE-NE-B13-01935 LTR. Rev.1 l 6. References l [1] BWRVIP-41, "BWR Jet Pump Assembly Inspection and Flaw Evaluation l Guidelines," EPRI Report TR-108728, October 1997.

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[2] SAP 4G07V Users Manual, NEDO 10909, Addenda 1, Revision 1,1996.

[3] Barsom, J.M., Rolfe, S.T., Fracture and Fatigue Control in Structures, Second l Edition, Prentice-Hall,Inc.

-[4] Attached Drawing and Document Reference Sheets.

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List cf the d:cuments us:d in the Verm:nt Yenkee Jet Pamp Riser Ftr.w Evtluiti:n l

Handbook Drawings:

Vessel e Reactor Vessel # 919D294 Rev. 8 e Reactor Thermal Cycles # 761E708 Rev. 0 & 729E762 Rev. O f

e Reactor Assembly # 104R940 Rev.10 Jet Pump

  • Assembly and Parts List # 730E438 G7,G8 Rev. 9 e Jet Pump Outline # 719El13 P5,P6 Rev.3
  • Riser and Parts List # 730E770 G3,G4 Rev. 3 e Riser Throat and Parts List # 919D959 G3,G4 Rev. 8 e Bracket Ring # 112C2186 P1,P2 Rev. 0
  • Riser Pipe # 117C1645P3 Rev. 5
  • Riser Brace and Parts List # 117C4614G1 Rev. 0
  • Riser Brace Yoke # 117C4612 P1 Rev. 0

. Riser Brace Leaf # 117C4613 P1 Rev. 0 a Transition Piece and Parts List # 729E619 P2 Rev.1

  • Riser Elbow,90 # 117Cl475 P1 Rev. 2 i e Diffuser and Parts List # 920D281 G5,6 Rev. 4 e Diffuser Shdi # 117C2820 P1 Rev. 2 e Coliar Casting # 730E767 P1 Rev. 2 e Inlet Mixer and Parts List # 920D278 G1 Rev. 5 e Inlet Mixer Barrel # ll7C2270 P1 Rev. 2

. Inlet Mixer Flange # 117C1609 P3 Rev. 5 .

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. Inlet Mixer Flare # 117C1477 P2 Rev. 2

  • Inlet Mixer Adapter # 921D780 G1 Rev. 0 e Nozzle-Throat & Parts List # 161F256 G3,4 Rev. 6

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  • Elbow Casting # 729E282 P1 Rev. 3
  • Nozzle Casting # 730E771 P1 Rev. 4 Modifications
  • Recirculation Inlet Safe End # 769E990 Rev.1 l

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VY1 Flaw Handbook References 04/24/98 2:52 PM c_____-___-______ _ _ _ _ _ _ _ _

List of the d:cuments used in the Verm:nt Yankee Jet Pump Ris:r Fliw Evcluztirn Handbook 1

Documents: I e BWRVIP-41,"BWR Jet Pump Assembly Inspection and Flaw Evaluation Guidelines", EPRI Report TR-108728, October 1997.

. Vermont Yankee FSAR Rev.14, November 1997.

  • Recire. Inlet Safe End Design Specification,23A4290 Rev.1 (Referenced from Reactor Vessel - Recirculation Inlet Safe End Nozzle Stress Report 23A4292 Rev. 4 forjet pump model properties and geometry).

NOTES:

1 Reference DRF# B13-01805 contained the Seismic response spectra that was used for seismic evaluation of core Spray piping subject to reactor core shroud repair, DRF# GE-NE-B13-01750.

2 No critical plant specific information was taken from the Reactor Thermal Cycle references, only plant characteristics that wew similar to Vermont Yankee. j I

VY1 Flaw Handbook References 04/24/98 2:52 PM

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