ML061440282
| ML061440282 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 05/22/2006 |
| From: | Bezilla M FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 3266, TAC MD0683 | |
| Download: ML061440282 (6) | |
Text
5501 North State Route 2 FirstEnergy Nuclear Operating Company Oak Harbor, Ohio 43449 Mark B. Bezilla 419-321-7676 Vice President - Nuclear Fax. 419-321-7582 Docket Number 50-346 License Number NPF-3 Serial Number 3266 May 22, 2006 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Davis-Besse Nuclear Power Station Supplemental Information for 10 CFR 50.55a Request Regarding Inservice Inspection Requirements for the Third Ten-Year Interval (RR-A29)
Ladies and Gentlemen:
By letter dated March 29, 2006 (Serial Number 3248), as supplemented by letter dated March 31, 2006 (Serial Number 3249), the FirstEnergy Nuclear Operating Company (FENOC) submitted a 10 CFR 50.55a request regarding American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI inservice inspection requirements for the third ten-year interval for the Davis-Besse Nuclear Power Station (DBNPS). The March 29, 2006 letter described a proposed full structural overlay repair for an axial indication found on a Reactor Coolant System (RCS) Loop 1 cold leg drain line during the Fourteenth Refueling Outage (l4RFO). The letter further noted that the repair would be conducted in accordance with ASME Code Case N-504-2, with modifications. The March 31 supplemental letter committed to providing the NRC with a summary of the analyses performed in support of the repair. Enclosure 1 provides this information.
Following completion of the repair and prior to restart from 14RFO, the NRC staff, via conference call on April 5, 2006, provided verbal authorization for the March 29 request.
As further discussed during the April 5, 2006 conference call, FENOC will evaluate the DBNPS Alloy 600 Program susceptibility ranking, inspection plan, and mitigation/repair matrix to incorporate lessons-learned from the 14RFO repair of the RCS Loop 1 cold leg drain line.
AVDLP
Docket Number 50-346 License Number NPF-3 Serial Number 3266 Page 2, Commitment List, identifies the commitments contained in this letter. If there are any questions or if additional information is required, please contact Mr. Gregory A. Dunn, Manager - FENOC Fleet Licensing, at (330) 315-7243.
Mark B. Bezilla, Vice Proldent-Nuclear MKL Enclosures cc:
Regional Administrator, NRC Region III NRC/NRR Project Manager NRC Senior Resident Inspector Utility Radiological Safety Board
Docket Number 50-346 License Number NPF-3 Serial Number 3266 Page 1
SUMMARY
OF ANALYSES IN SUPPORT OF WELD OVERLAY REPAIR DAVIS-BESSE NUCLEAR POWER STATION INTRODUCTION During the Fourteenth Refueling Outage (I 4RFO) for the FirstEnergy Nuclear Operating Company (FENOC) Davis-Besse Nuclear Power Station (DBNPS), ultrasonic examinations were performed on the Class 1 Reactor Coolant System (RCS) Loop 1 cold leg drain lines. During these examinations, an axial indication was identified in a nozzle-to-elbow weld in one of the drain lines. Specifically, the indication was found in the nozzle weld butter material of the dissimilar metal, nozzle-to-elbow weld in the Reactor Coolant Pump 1-1 inlet cold leg drain line, weld RC-40-CCA-1 8-1-FW2.
As there is no qualified manual depth sizing procedure for dissimilar metal welds (DMW), the axial indication was deemed unacceptable and required repair. Since the indication is in a material that is susceptible to primary water stress corrosion cracking (PWSCC), FENOC decided to perform a full structural overlay to restore the integrity of the pressure boundary and to mitigate any potential PWSCC.
The structural weld overlay of the cold leg drain nozzle was designed consistent with the requirements of the ASME Code,Section XI, Code Case N-504-2 and Nonmandatory Appendix Q, as supplemented by additional design considerations specific to the unique nature of the geometry and materials of the DBNPS cold leg drain nozzle-to-elbow weld. These additional considerations are documented in 10 CFR 50.55a request RR-A29 for the third ten-year interval, submitted by letter dated March 29, 2006 (Serial No. 3248), and supplemented by letter dated March 31, 2006 (Serial 3249). In the March 31 supplemental letter, FENOC committed to provide the NRC with a summary of the analyses performed for the repair.
CALCULATION
SUMMARY
The following table summarizes the calculation packages that were prepared to document the design and analysis of the DBNPS Reactor Coolant Pump 1-1 inlet cold leg drain line nozzle-to-elbow weld overlay:
Docket Number 50-346 License Number NPF-3 Serial Number 3266 Page 2 Code Case N-504-2 Governing Calculation Paragraph' Number Title and Purpose Summary of Results (f)(1)
DB-06Q-Weld Overlay SizingforRCS-1-1 Cold The minimum required
[Same as Q-301, Rev. 2 Leg Drain Nozzle thickness and length of the 3000(a), (b)]
Determine the required size (thickness overlay meets the structural and length) for a full structural integrity and inspection (standard) overlay repair based on plant requirements of Code Case specific nozzle geometry and loadings, N-504-2 and Nonmandatory and ASME Code,Section XI Code Appendix Q.
Case N-504-2.
(f)(1)
DB-06Q-Finite Element Models of the Davis Finite element models were
[Same as Q-302, Rev. 1 Besse Unit I Reactor Coolant Cold Leg developed for use in 3000(a), (b)]
Drain Nozzle with Weld Overlay calculating mechanical, Repair Using Design Dimensions thermal and residual Develop finite element models of the stresses.
overlaid drain nozzle configuration, based upon the design provided in DB-06Q-301. The models are used in subsequent calculations to calculate stresses.
(f)(1), (g)(2)
DB-06Q-Thermal and Mechanical Stress Design basis loads were
[Same as Q-303, Rev. 1 Analyses of Cold Leg Letdown Nozzle applied to the finite element 3000(b)(1),
with Weld Overlay Repair models and stresses (b)(3)]
Analyze the finite element models for calculated for those loading design bases loading conditions, and conditions.
produce stress results for use in ASME Code Section III stress and fatigue evaluations, and Section XI crack growth evaluations.
(f)(1)
DB-06Q-RCS Cold Leg Letdown Line Nozzle The required evaluations
[Same as Q-304, Rev. 1 Weld Overlay Repair ASME Code were performed and all 3000(b)(1)]
Section III Evaluation ASME Code stress and Perform an ASME Code,Section III, fatigue acceptance criteria Class 1 evaluation for the repaired were met.
configuration by comparing primary and secondary stress intensities calculated in DB-06Q-303 to appropriate Section III acceptance criteria, and perform a fatigue evaluation in accordance with Section III criteria.
Docket Number 50-346 License Number NPF-3 Serial Number 3266 Page 3 Code Case N-504-2 Governing Calculation Paragraph1 Number Title and Purpose Summary of Results (g)(3)
DB-06Q-RCS Letdown Nozzle Weld Shrinkage Piping system stresses
[Same as Q-305, Rev. 1 Analysis resulting from the measured 3000(b)(4)]
Determine maximum stresses axial shrinkage associated developed in the reactor coolant drain with the weld overlay repair and letdown piping system due to the were small compared to the effects of the observed weld shrinkage load carrying capability of associated with the weld overlay repair.
the system.
(g)(2)
DB-06Q-Residual Stress Evaluation of the Davis The weld residual stresses at 306, Rev. I Besse Unit I Reactor Coolant Cold Leg and near the inside surface Drain Nozzle with Weld Overlay of the PWSCC susceptible Repair Using Design Dimensions material were reversed from Analyze the finite element model for tensile to compressive after weld residual stresses resulting from application of the weld the initial butt weld and a postulated overlay.
repair, as well as for the application of the weld overlay.
(g)(3)
DB-06Q-Predicting Fatigue Crack Growth for Crack growth is not 307, Rev. 0 the DB Unit 1 RCP 1-1 Cold Leg Drain considered to be a Nozzle With Design Weld Overlay significant factor affecting Address the potential crack growth due the weld overlay design to both stress corrosion and fatigue based on the compressive utilizing initial (or postulated) crack stresses present in the geometry, and the stress fields nozzle weld due to the generated in DB-06Q-303 and presence of the overlay.
DB-06Q-306.
(f)(),
SIR-06-148, Weld Overlay Design and Analysis for All design requirements of (g)(2), (g)(3)
Rev. 0 Reactor Coolant Pump 1-1 Inlet Cold the ASME Code, Section
[Q-3000(a),
Leg Drain Nozzle-to-Elbow Weld at XI, Code Case 504-2 were (b)]
Davis-Besse Nuclear Power Station met by the overlay design.
Provides a summary of the technical basis and the supporting design and analyses of the cold leg drain nozzle overlay, as provided in the applicable calculation packages..
ICorresponding Nonmandatory Appendix Q paragraph indicated in brackets.
Docket Number 50-346 License Number NPF-3 Serial Number 3266 Page 1 of 1 COMMITMENT LIST The following list identifies those actions committed to by the Davis-Besse Nuclear Power Station, Unit Number 1, (DBNPS) in this document. Any other actions discussed in the submittal represent intended or planned actions by the DBNPS. They are described only for information and are not regulatory commitments. Please notify Gregory A. Dunn, Manager -
FENOC Fleet Licensing (330-315-7243) of any questions regarding this document or associated regulatory commitments.
COMMITMENTS DUE DATE FENOC will evaluate the DBNPS Alloy 600 Program In accordance with the susceptibility ranking, inspection plan, and DBNPS Corrective Action mitigation/repair matrix to incorporate lessons-learned Program from the 14RFO repair of the RCS Loop 1 cold leg drain line.