ML092320124

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Stress Analysis Reports for Reactor Pressure Vessel (RPV) Jet Pump Instrumentation Nozzle Weld, RPV-N9A-1 Overlay Repair (Pilgrim Relief Request (PRR) -19)
ML092320124
Person / Time
Site: Pilgrim
Issue date: 08/13/2009
From: Bethay S
Entergy Nuclear Operations
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
RPV-N9A-1, TAC ME1151
Download: ML092320124 (7)
v • d • e


Text

Entergy Nuclear Operations, Inc.

Pilgrim Nuclear Power Station 600 Rocky Hill Road Plymouth, MA 02360 Stephen J. Bethay Director, Nuclear Assessment August 13, 2009 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001

SUBJECT:

Entergy Nuclear Operations, Inc.

Pilgrim Nuclear Power Station Docket No. 50-293 License No. DPR-35 Stress Analysis Reports for Reactor Pressure Vessel (RPV) Jet Pump Instrumentation Nozzle Weld, RPV-N9A-1 Overlay Repair (Pilgrim Relief Request (PRR) -19) (TAC. NO. ME1 151)

REFERENCES:

1. Entergy Letter No. 2.09.032, Pilgrim Relief Request (PRR)-19, Jet Pump Nozzle Weld, RPV-N9A-1 Repair Plan, dated May 1, 2009
2. Entergy Letter No. 2.09.037, Results of UT Examination of Jet Pump Instrumentation Nozzle RPV-N9A-1 Weld Overlay, dated May 15, 2009 LETTER NUMBER: 2.09.050

Dear Sir/Madam,

By this letter, Entergy submits to the NRC the attached Stress Analysis Summary reports demonstrating that the N9A nozzle to safe-end-weld dissimilar metal weld will perform its intended design function after weld overlay installation. This submittal and the submittal made by Reference 2 fulfill the commitments made in Reference 1.

The Stress Analysis Summary reports demonstrates that the proposed alternative presented in Pilgrim Relief Request (PRR)-19 (Reference 1) provides an acceptable level of quality and safety, within the scope of 10 CFR 50.55a(a)(3)(i).

There are no new commitments made in this submittal.

If you have any questions, please contact Pilgrim Licensing Manager, Mr. Joseph Lynch at 508 830-8403.

Sincerely, Step e .ta Director, Nuclear Safet Assurance SJ B/wgI

Entergy Nuclear Operations, Inc Letter No. 2.09.050 Pilgrim Nuclear Power Station Page 2 ATTACHMENTS:

1. Structural Integrity Associates, Inc. Letter to Entergy (Mr. Ray Pace), "Stress Analysis Summary for Weld Overlay of Jet Pump Instrumentation Nozzle N9A" , dated August 10, 2009 (3 pages)
2. Structural Integrity Associates, Inc. File No. 0900530.306, "ASME Code,Section III Evaluation of N9A Jet Pump Instrument Nozzle with Weld Overlay Repair", dated August 10, 2009 (70 pages)
3. Structural Integrity Associates, Inc. File No. 0900530.307, "Residual Stress Analysis of Jet Pump Instrument Nozzle (N9A) with Weld Overlay Repair", dated August 10, 2009 (32 pages)
4. Structural Integrity Associates, Inc. File No. 0900530.308, "Crack Growth Analysis for Jet Pump Instrument Nozzle (N9A)", dated August 10, 2009 (55 pages) cc: Regional Administrator, Region 1 Mr. James S. Kim, Project Manager U.S. Nuclear Regulatory Commission Plant Licensing Branch I-1 475 Allendale Road Division of Operator Reactor Licensing King of Prussia, PA 19406 Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission One White Flint North 0-8C2 Senior Resident Inspector 11555 Rockville Pike Pilgrim Nuclear Power Station Rockville, MD 20852

ATTACHMENT 1 To Enterqy Letter No. 2.09.050 Structural Integrity Associates, Inc. Letter to Entergy (Mr. Ray Pace),

"Stress Analysis Summary for Weld Overlay of Jet Pump Instrumentation Nozzle N9A". dated August 10, 2009 (3 pages)

StructuralIntegrity Associates, Inc.

6855 S Havana St, Suite 350 Centennial, CO 80112 Phone: 303-792-0077 Fax: 303-792-2158 www.structint.com HLGusin@structint.com August 10, 2009 SI Report 0900530.401 Revision 0 Mr. Ray Pace Entergy Nuclear Northeast Pilgrim Nuclear Power Station 600 Rocky Hill Road Plymouth, MA 02360

SUBJECT:

Stress Analysis Summary for Weld Overlay of Jet Pump Instrumentation Nozzle N9A

References:

1. SI Calculation No. 0900530.306, Rev. 0, "ASME Code,Section III Evaluation of N9A Jet Pump Instrument Nozzle with Weld Overlay Repair."
2. Combustion Engineering, Inc., Report No. CENC-1139, "Analytical Report for Pilgrim Reactor Vessel", March 1971, SI File No. PNPS-1OQ-21 1.
3. SI Calculation No. 0900530.308, Rev. 0, "Crack Growth Analysis for Jet Pump Instrumentation Nozzle (N9A)."
4. ASME Boiler & Pressure Vessel Code,Section XI, 1998 Edition, with Addenda through 2000.
5. SI Calculation No. 0900530.307, Rev. 0, "Residual Stress Analysis of Jet Pump Instrumentation Nozzle (N9A) with Weld Overlay Repair."

Dear Mr. Pace:

During the Spring 2009 outage, a full structural weld overlay repair was applied on the affected weld on the N9A Jet Pump Instrumentation Nozzle at Pilgrim Nuclear Power Station (PNPS). This repair was made over a previous 1984 weld overlay repair. The present repair meets all current design criteria, including requirements for inspection. The design basis of this repair was that the underlying flaw was assumed to be entirely through the original component wall, and extended entirely around the component circumference. Design was

Code Case N-504-3 includes several requirements for evaluating and validating the weld overlay design. These include:

1. N-504-3 (f)(1): "The axial length and end slope of the reinforcement shall be sufficient to provide for load redistribution from the pipe into the deposited weld metal and back into the Annapolis, MD Austin, TX Cerritos, CA Charlotte, NC Chattanooga, TN Oakville, Ontario, Canada San Jose, CA South Jordon, UT Stonington, CT Uniontown, OH 410-571-0861 512-533-9191 562-402-3076 704-597-5554 423-553-1180 905-829-9817 408-978-8200 801-676-0216 860-536-3982 330-899-9753

Mr. Ray Pace, Energy Nuclear Northeast August 10, 2009 SI Report 0900530.401 Revision 0 Page 2 of 3 pipe without violating applicable stress limits of Section III for primary local and bending stresses and secondary peak stresses."

2. N-504-3 (g)(2)): "For repaired welds the evaluation shall consider residual stresses produced by the weld overlay with other applied loads on the system... The evaluation shall demonstrate that the requirements of IWB-3640... are satisfied for the design life of the repair, considering potential flaw growth due to fatigue and the mechanism believed to have caused the flaw."
3. N-504-3 (g)(3): "The evaluation of other welds and components in the system shall consider potential increases in loading, including shrinkage effects, due to all overlays in the system, and shall identify and record the magnitude and location of the maximum shrinkage stress developed."

The purpose of this letter and the referenced calculations is to document the results of analyses that demonstrate meeting those requirements.

1. Code Reconciliation/Stress Analysis Summary Structural Integrity Associates calculation 0900530.306 [1] was prepared to address requirement 1 above. This calculation reconciles the effects of the weld overlay repair of nozzle N9A at PNPS to the nozzle's original ASME Section III Stress Report [2].

The Reference [ 1] calculation evaluates the N9A Jet Pump Instrumentation Nozzle with the weld overlay repair under operating conditions using finite element analysis. It also addresses item (f)(1) of Code Case N-504-3, which requires that the overlay be sized so that it is able to provide for load redistribution from the pipe into the deposited weld metal and back into the pipe without exceeding applicable stress limits of ASME Section III for primary local and bending stresses and secondary peak stresses.

Multiple analyses consistent with the nozzle Stress Report [2] were performed with the applied weld overlay. The resulting stresses were compared to Section III Code allowable stresses to reconcile the repair with Reference [2] stress results and calculated fatigue usage.

The evaluation considered primary and secondary stress intensities, fatigue usage and applicable Code Case N-504-3 requirements. This evaluation concludes that the impact of the overlay is minor and generally produces a more favorable stress condition. The revised stresses are within Code allowable values, and fatigue usage is not significant. Therefore, the original Stress Report

[2] which demonstrated Code compliance remains valid for the nozzle with the weld overlay repair.

2. Crack Growth Evaluation Structural Integrity Associates calculation 0900530.308 [3] was prepared to address requirement 2 above. Linear elastic fracture mechanics (LEFM) analyses were performed to calculate crack growth in the nozzle-to-safe end dissimilar metal weld (DMW) for the reactor Structural Integrity Associates, Inc.

Mr. Ray Pace, Energy Nuclear Northeast August 10, 2009 SI Report 0900530.401 Revision 0 Page 3 of 3 pressure vessel (RPV) Jet Pump Instrumentation Nozzle N9A at PNPS. Loads considered were internal pressure and weld overlay (WOL) repair residual stresses, which were calculated in Structural Integrity Associates calculation 0900530.307 [5]. Both fatigue crack growth (FCG) and Intergranular Stress Corrosion Cracking (IGSCC) are considered.

This evaluation shows that a hypothetical flaw in the PNPS N9A nozzle-to-safe end weld performed during the Spring 2009 outage will not grow to a depth which reduces the weld overlay design basis, and therefore the overlay is predicted to remain acceptable and continue to meet the requirements of ASME Code,Section XI, Appendix C and Table IWB-3641-3 [4]. The WOL residual stresses provide a significant benefit to the mitigation of crack growth, especially for IGSCC growth. Taking credit for these residual stresses produces a negative stress intensity factor, resulting in no additional crack growth at this location.

3. Weld Overlay Shrinkage Since the N9A nozzle is essentially a free end with no attached piping other than very flexible instrument lines, weld overlay shrinkage will produce no adverse affect on any other location at PNPS.

Conclusion The above referenced calculations demonstrate that the post overlay evaluation requirements of Code Case N-504-3 have been met for the as-applied weld overlay repair to the N9A nozzle-to-safe end weld at Pilgrim Nuclear Power Station.

Very truly yours, Hal L. Gustin Associate Reviewed by:

Karen Fujikawa Senior Associate cc: W. Lobo G. Mileris SI File No. 0900530.401 StructuralIntegrity Associates, Inc.

ATTACHMENT 2 To Entergy Letter No. 2.09.050 Structural Integrity Associates, Inc. File No. 0900530.306, "ASME Code,Section III Evaluation of N9A Jet Pump Instrument Nozzle with Weld Overlay Repair", dated August 10, 2009 (70 pages)

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