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Category:Letter
MONTHYEARIR 05000237/20230042024-02-0202 February 2024 Integrated Inspection Report 05000237/2023004 and 05000249/2023004 IR 05000010/20230012024-01-17017 January 2024 NRC Inspection Report 05000010/2023001 (Drss) ML23354A2812024-01-0404 January 2024 Exemption from Select Requirements of 10 CFR Part 73 (EPID L-2023-LLE-0031 (Security Notifications, Reports, and Recordkeeping and Suspicious Activity Reporting)) ML23305A1402023-12-13013 December 2023 Units 1 & 2; Nine Mile Point, Unit 2; Peach Bottom, Units 2 & 3; and Quad Cities, Units 1 and 2 - Issuance of Amendments to Adopt Traveler TSTF-580 RS-23-121, Sixth Ten-Year Interval Inservice Testing Program2023-11-30030 November 2023 Sixth Ten-Year Interval Inservice Testing Program SVPLTR 23-0037, Core Operating Limits Report for Cycle 292023-11-29029 November 2023 Core Operating Limits Report for Cycle 29 RS-23-119, Supplemental Information Letter for Part 73 Exemption Request - Responses to Request for Confirmatory Information2023-11-10010 November 2023 Supplemental Information Letter for Part 73 Exemption Request - Responses to Request for Confirmatory Information ML23317A1192023-11-10010 November 2023 Constellation Energy Generation, LLC - 2023 Annual Report - Guarantees of Payment of Deferred Premiums RS-23-107, Relief Request I5R-22, Inservice Inspection Program Relief Request Regarding Examination Coverage for the Fifth Inservice Inspection Interval2023-11-0808 November 2023 Relief Request I5R-22, Inservice Inspection Program Relief Request Regarding Examination Coverage for the Fifth Inservice Inspection Interval RS-23-102, Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation2023-10-16016 October 2023 Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation ML23285A2342023-10-13013 October 2023 Confirmation of Initial License Examination RS-23-097, Constellation Energy Generation, LLC, Advisement of Leadership Changes and Submittal of Updated Standard Practice Procedures Plans2023-10-12012 October 2023 Constellation Energy Generation, LLC, Advisement of Leadership Changes and Submittal of Updated Standard Practice Procedures Plans ML23279A0712023-10-0606 October 2023 Response to NRC Dresden Nuclear Power Station, Units 2 and 3 - Comprehensive Engineering Team Inspection Report 05000237/2023011 and 05000249/2023011 ML23269A0662023-09-28028 September 2023 Proposed Alternative Request RV-23H Associated with the Sixth 10-Year Inservice Testing Interval ML23265A1322023-09-27027 September 2023 Proposed Alternative Request RV-03 Associated with the Sixth 10-Year Inservice Testing Interval ML23205A1362023-09-20020 September 2023 Proposed Alternative Request RV-02D Associated with the Sixth IST Interval IR 05000237/20230112023-09-0606 September 2023 Comprehensive Engineering Team Inspection Report 05000237/2023011 and 05000249/2023011 RS-23-071, Application to Adopt TSTF-564, Safety Limit MCPR2023-08-30030 August 2023 Application to Adopt TSTF-564, Safety Limit MCPR RS-23-080, Constellation Energy Generation, LLC, Application to Revise Technical Specifications to Adopt TSTF-264-A, Revision 0, 3.3.9 and 3.3.10 - Delete Flux Monitors Specific Overlap Requirement SRs2023-08-30030 August 2023 Constellation Energy Generation, LLC, Application to Revise Technical Specifications to Adopt TSTF-264-A, Revision 0, 3.3.9 and 3.3.10 - Delete Flux Monitors Specific Overlap Requirement SRs IR 05000237/20234022023-08-29029 August 2023 Security Baseline Inspection Report 05000237/2023402 and 05000249/2023402 IR 05000237/20230022023-08-0808 August 2023 Integrated Inspection Report 05000237/2023002 and 05000249/2023002 ML23212A9892023-08-0303 August 2023 Subsequent License Renewal Application Public Meeting Summary of Pre-Submittal Meeting ML23174A1502023-08-0303 August 2023 Issuance of Amendment Nos. 282 and 275 Control Rod Scram Times ML23193A0052023-07-28028 July 2023 Subsequent License Renewal Application Public Meeting Summary of Pre-Submittal Meeting ML23192A6292023-07-11011 July 2023 Correction Letter - Issuance of Amendment Nos. 281 and 274 Regarding Transition to GNF3 Fuel (EPID L-2022-LLA-0121) (Non-Proprietary) ML23144A3142023-07-0606 July 2023 Issuance of Amendment Nos. 281 and 274 Transition to GNF3 Fuel (EPID L-2022-LLA-0121) - Nonproprietary ML23187A0462023-07-0606 July 2023 Notification of NRC Baseline Inspection and Request for Information; Inspection Report 05000237/2023004 ML23178A2422023-06-28028 June 2023 Reassignment of the U.S. Nuclear Regulatory Commission Branch Chief in the Division of Operating Reactor Licensing for Plant Licensing Branch III SVPLTR 23-0021, Registration of Use of Casks to Store Spent Fuel2023-06-20020 June 2023 Registration of Use of Casks to Store Spent Fuel RS-23-078, Supplement to License Amendment Request to Revise Technical Specification 3.1.4, Control Rod Scram Times2023-06-16016 June 2023 Supplement to License Amendment Request to Revise Technical Specification 3.1.4, Control Rod Scram Times RS-23-077, Response to NRC Regulatory Issue Summary 2023-01, Preparation and Scheduling of Operator Licensing Examinations2023-06-16016 June 2023 Response to NRC Regulatory Issue Summary 2023-01, Preparation and Scheduling of Operator Licensing Examinations IR 05000237/20233012023-05-30030 May 2023 NRC Initial License Examination Report 05000237/2023301; 05000249/2023301 RS-23-042, Application to Revise Technical Specifications to Adopt TSTF-580, Provide Exception from Entering Mode 4 with No Operable RHR Shutdown Cooling2023-05-25025 May 2023 Application to Revise Technical Specifications to Adopt TSTF-580, Provide Exception from Entering Mode 4 with No Operable RHR Shutdown Cooling ML23132A0932023-05-17017 May 2023 Information Meeting (Public Open House) with a Question and Answer Session to Discuss NRC 2022 End-Of-Cycle Plant Performance Assessment of Dresden Power Station, Units 2 and 3 RS-23-070, Supplement to License Amendment Request Regarding Transition to GNF3 Fuel2023-05-16016 May 2023 Supplement to License Amendment Request Regarding Transition to GNF3 Fuel SVPLTR 23-0018, Submittal of 2022 Annual Radiological Environmental Operating Report2023-05-15015 May 2023 Submittal of 2022 Annual Radiological Environmental Operating Report IR 05000237/20230012023-05-0404 May 2023 Integrated Inspection Report 05000237/2023001 and 05000249/2023001 SVPLTR 23-0019, ILT 22-1 (2023-301) Svpltr 23-0019 Post-Exam Submittal Letter (1)2023-05-0101 May 2023 ILT 22-1 (2023-301) Svpltr 23-0019 Post-Exam Submittal Letter (1) ML23118A3472023-05-0101 May 2023 County, 1 & 2; Nine Mile Point, 2; and Quad Cities, 1 & 2 - Correction of Amendment No. 193 Adoption of TSTF-306, Revision 2, Add Action to LCO 3.3.6.1 to Give Option to Isolate the Penetration EPID L-2022-LLA-0143 ML23114A2522023-04-28028 April 2023 Request to Use a Provision of a Later Edition of the ASME Boiler & Pressure Vessel Code, Section XI IR 05000237/20234012023-04-26026 April 2023 Cyber Security Inspection Report 05000237/2023401 and 05000249/2023401 ML23081A0382023-04-25025 April 2023 County, 1 & 2; Nine Mile Point, 2; and Quad Cities, 1 & 2 - Issuance of Amendments to Adopt TSTF-306, Rev. 2, Add Action to LCO 3.3.6.1 to Give Option to Isolate the Penetration IR 05000237/20235012023-04-21021 April 2023 Emergency Preparedness Biennial Exercise Inspection Report 05000237/2023501 and 05000249/2023501 ML23110A3202023-04-21021 April 2023 Information Request to Support the NRC Annual Baseline Emergency Action Level and Emergency Plan Changes Inspection RS-23-057, Supplement to License Amendment Request Regarding Transition to GNF3 Fuel2023-04-17017 April 2023 Supplement to License Amendment Request Regarding Transition to GNF3 Fuel SVPLTR 23-0014, Annual Dose Report for 20222023-04-15015 April 2023 Annual Dose Report for 2022 ML23088A2242023-04-0505 April 2023 Regulatory Audit Report Regarding License Amendment Request to Transition to GNF3 Fuel ML23087A0482023-03-28028 March 2023 Operator Licensing Examination Approval - Dresden Nuclear Power Station, April 2023 2024-02-02
[Table view] Category:Safety Evaluation
MONTHYEARML23305A1402023-12-13013 December 2023 Units 1 & 2; Nine Mile Point, Unit 2; Peach Bottom, Units 2 & 3; and Quad Cities, Units 1 and 2 - Issuance of Amendments to Adopt Traveler TSTF-580 ML23269A0662023-09-28028 September 2023 Proposed Alternative Request RV-23H Associated with the Sixth 10-Year Inservice Testing Interval ML23265A1322023-09-27027 September 2023 Proposed Alternative Request RV-03 Associated with the Sixth 10-Year Inservice Testing Interval ML23205A1362023-09-20020 September 2023 Proposed Alternative Request RV-02D Associated with the Sixth IST Interval ML23174A1502023-08-0303 August 2023 Issuance of Amendment Nos. 282 and 275 Control Rod Scram Times ML23144A3142023-07-0606 July 2023 Issuance of Amendment Nos. 281 and 274 Transition to GNF3 Fuel (EPID L-2022-LLA-0121) - Nonproprietary ML23114A2522023-04-28028 April 2023 Request to Use a Provision of a Later Edition of the ASME Boiler & Pressure Vessel Code, Section XI ML23081A0382023-04-25025 April 2023 County, 1 & 2; Nine Mile Point, 2; and Quad Cities, 1 & 2 - Issuance of Amendments to Adopt TSTF-306, Rev. 2, Add Action to LCO 3.3.6.1 to Give Option to Isolate the Penetration ML23032A3602023-03-22022 March 2023 Issuance of Amendment Nos. 279 and 272 New Fuel Storage Vault and Spent Fuel Storage Pool Criticality Methodologies ML22335A5442022-12-20020 December 2022 Authorization and Safety Evaluation for Alternative Request I6R-01, ML22293B8052022-11-30030 November 2022 Constellation Energy Generation, Llc_Fleet - Request to Authorize Use Honeywell Mururoa V4F1 R Supplied Air Suits ML22298A2802022-11-29029 November 2022 Authorization and Safety Evaluation for Alternative Request I6R-02 ML22090A0862022-04-29029 April 2022 Amendments to Adopt TSTF-541,Rev.2,Add Exceptions to Surveillance Requirements for Valves,Dampers Locked in Actuated Position ML22094A0012022-04-15015 April 2022 Constellation Energy Generation, LLC - Proposed Alternative for Repair of Water Level Instrumentation Partial Penetration Nozzles (Epids L-2021-LLR-0057 and L-2021-LLR-0058) ML21347A0382022-01-13013 January 2022 Issuance of Amendments to Revise Reactor Coolant Leakage Requirements ML21267A3172021-12-13013 December 2021 Proposed Alternative to Eliminate Certain Documentation Requirements for Pressure Retaining Bolting (6th ISI Interval) (Epids L-2021-LLR 0029, 0030) ML21307A3422021-12-0707 December 2021 Issuance of Amendments to Adopt Reactor Pressure Vessel Water Inventory Control Enhancements (EPIDs L-2020-LLA-0253 and L-2020-LLA-0254) ML21277A2482021-11-16016 November 2021 Letter with Enclosure 4, Safety Evaluation for Transfer of Licenses and Draft Conforming License Amendments (Public Version) ML21230A2062021-09-0303 September 2021 Proposed Alternative to Use ASME OM Code Case OMN-28 ML21076A3712021-08-17017 August 2021 Approval of Certified Fuel Handler Training and Retraining Program ML21216A2202021-08-0505 August 2021 Proposed Alternative to Eliminate Certain Documentation Requirements for Pressure Retaining Bolting ML21166A1682021-06-25025 June 2021 ML21033A5302021-04-0101 April 2021 Issuance of Amendments to Adopt Technical Specifications Task Force TSTF-566, Revise Actions for Inoperable RHR Shutdown Cooling Subsystems ML21013A0052021-02-0404 February 2021 Issuance of Amendments to Adopt Technical Specifications Task Traveler TSTF-568, Revise Applicability of BWR/4 TS 3.6.2.5 and TS 3.6.3.2 ML21028A6732021-02-0303 February 2021 Request to Use a Provision of Later Edition of the ASME Boiler and Pressure Vessel Code, Section XI (EPID L-2020-LLR-011 ML21005A0612021-01-14014 January 2021 Proposed Alternatives to Extend the Safety Relief Valve Testing Interval (EPID L-2020-LLR-0014 Through L-2020-LLR-0018) ML20287A1302020-11-0505 November 2020 Review of Quality Assurance Program Changes ML20265A2402020-10-23023 October 2020 Issuance of Amendment Nos. 272 and 265 to Increase Allowable Main Steam Isolation Valve Leakage ML20269A2002020-09-30030 September 2020 Request to Use a Provision of Later Edition of the ASME Boiler and Pressure Vessel Code, Section XI (EPID L2020-LLR-0117 ML20153A8042020-07-31031 July 2020 Co. - Issuance of Amendments Revising Emergency Action RA3 ML20141L6362020-07-10010 July 2020 Issuance of Amendments Based on TSTF-427,Allowance for Nontechnical Specification Barrier Degradation on Supported System Operability,Rev 2 ML20134H9402020-07-0808 July 2020 Issuance of Amendments Revising the High Radiation Area Administrative Controls ML20021A0702020-04-0606 April 2020 Issuance of Amendments to Delete License Conditions for Decommissioning Trusts ML19331A7252020-02-14014 February 2020 Issuance of Amendments Revising Emergency Action Levels ML20008D2762020-01-13013 January 2020 Safety Evaluation in Support of Request for Relief Associated with the Fifth Ins)Inservice Inspection Interval Relief Request I5R-04, Revision 2 ML19301A3392019-12-0404 December 2019 Issuance of Amendments to Revise Technical Specification 2.1.1, Reactor Core Safety Limits, the Minimum Critical Power Ration Safety Limits ML19269C5342019-09-27027 September 2019 Proposed Alternative to Use Encoded Phased Array Ultrasonic Examination Techniques ML19192A2442019-07-18018 July 2019 Proposed Alternative to Use ASME Code Cases N-878 and N-880 ML19098A0342019-04-30030 April 2019 Units 1 and 2; Limerick, Units 1 and 2; Peach Bottom, Units 2 and 3, and Quad Cities, Units 1 and 2 - Revision to Approved Alternative to Use BWR Vessel and Internal Proj Guidelins ML19036A5862019-03-21021 March 2019 Issuance of Amendments to Revise the Emergency Response Organization Staffing Requirements ML18304A3652019-01-16016 January 2019 2. Issuance of Amendments to Revise the Average Power Range Monitor Requirements ML18254A3672018-10-29029 October 2018 County 1 & 2; and Quad Cities 1 & 2 - Issuance of Amendments 220, 259, 252, 231, 217, 271 and 266 to Revise Technical Specification Requirements for Inoperable Snubbers ML18206A2822018-08-0202 August 2018 Issuance of Amendments to Relocate the Staff Qualification Requirements ML18137A2712018-06-29029 June 2018 Issuance of Amendments Regarding Permanent Extension of Type a and Type C Leak Rate Test Frequencies (Cac. Nos. MF9687 and MF9688; EPID L-2017-LLA-0228) (RS-17-060) ML18079A3822018-04-27027 April 2018 Safety Evaluation Regarding Implementation of Hardened Containment Vents Capable of Operation Under Severe Accident Conditions Related to Order EA-13-109 ML18060A3242018-03-0909 March 2018 Relief Request I5R-16 Approval of Alternative to Use the Performance Demonstration Initiative Program for Weld Overlay Inspection Qualifications ML18022A6162018-01-24024 January 2018 Approval of Alternatives to the ASME Code Regarding Reactor Vessel Penetration N-11B - Relief Request 15R-11, Revision 3 (CAC No. MF9286; EPID L-2017-LLR-0004) (RS-17-014) ML17272A7832018-01-0808 January 2018 Issuance of Amendments to Adopt TSTF-542 TS Changes (CAC Nos. MF9295 and MF9296; EPID L-2017-LLA-0176) ML17121A0492017-10-30030 October 2017 Safety Evaluation by the Office of Nuclear Reactor Regulation for the Proposed Alternative for the Use of Encoded Phased Array Ultrasonic Examination Techniques in Lieu of Radiography ML17163A3552017-08-31031 August 2017 Calvert Cliff, Clinton, Dresden, LaSalle, Limerick, Nine Mile Point, Peach Bottom, Quad Cities, R. E. Ginna, and Three Miles Island - Issuance of Amendments to Adopt TSTF-529, Clarify Use and Application Rules(Cac Nos. MF9470-MF9490) 2023-09-28
[Table view] |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 June 11, 2010 Mr. Michael J. Pacilio President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555 SUB~IECT: DRESDEN NUCLEAR POWER STATION, UNITS 2 - REVIEW AND APPROVAL OF A FLAW EVALUATION (TAC NO. ME2604)
Dear Mr. Pacilio:
By letter dated November 16, 2009 (Agencywide Documents Access and Management System (ADAMS), Accession No. ML093210142), as supplemented by letter dated November 24,2009 (ADAMS Accession No. ML093290088), Exelon Generation Company, LLC (EGC or the licensee), submitted for Nuclear Regulatory Commission (NRC) staff review, a flaw evaluation report for Dresden Nuclear Power Station (DNPS), Unit 2, regarding a circumferential flaw indication in Weld PD1A-D14, which is located on the downstream side of a 28-inch recirculation pump A discharge elbow-to-pipe weld. The examination of the flaw indicated that, although the flaw length remained unchanged at 1 inch, the flaw depth has increased from its previous examination from 0.25 inch (November 2007) to 0.32 inch (November 2009). The flaw indication does not meet the acceptance standards for continued operation without repair or replacement, or flaw evaluation in accordance with the American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code (Code)Section XI, 1995 Edition through the 1996 Addenda, which is the current code of record for the fourth inservice inspection interval for DNPS, Unit 2.
The licensee requested NRC staff approval of the pipe flaw evaluation for Weld PD1A-D14 to support the start up and operation of DNPS, Unit 2, following refueling outage D2R21. The licensee proposed to leave the weld as-is without repair for the following cycle.
The NRC staff has completed its review of the submittal and supplemental information and found that the licensee's flaw evaluation meets the rules in the 1995 Edition through 1996 Addenda of Section XI of the ASME Code. On November 25, 2009, the NRC staff verbally accepted the licensee's flaw evaluation, authorizing the licensee to operate DNPS, Unit 2, for an additional cycle. The enclosed safety evaluation is a written confirmation of the verbal authorization.
Si~
Christopher Gratton, Senior Project Manager Plant Licensing Branch 111-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-237
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Safety Evaluation cc w/encls: Distribution via Listserv
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DRESDEN NUCLEAR POWER STATION, UNIT 2 RECIRCULATION PIPE WELD PD1A-D14 FLAW EVALUATION EXELON GENERATION COMPANY, LLC DOCKET NO. 50-237
1.0 INTRODUCTION
By letter dated November 16, 2009 (Agencywide Documents Access and Management System (ADAMS), Accession No. ML093210142), as supplemented by letter dated November 24,2009 (ADAMS Accession No. ML093290088), Exelon Generation Company, LLC (EGC or the licensee), submitted a flaw evaluation report to the Nuclear Regulatory Commission (NRC, or Commission) staff for Dresden Nuclear Power Station (DNPS), Unit 2, regarding a circumferential flaw indication in Weld PD1A-D14, which is located on the downstream side of a 28-inch recirculation pump A discharge elbow-to-pipe weld. The flaw indication was originally detected in 1986 and was last reexamined by ultrasonic testing (UT) on November 8, 2009, during the refueling outage D2R21, in accordance with Boiling-Water Reactor Vessel and Internals Project (BWRVIP) Report 75-A, "Technical Basis for Revisions to Generic Letter (GL) 88-01 Inspection Schedules." This reexamination indicated that, although the flaw length remained unchanged at 1 inch (in.), the flaw depth has increased from 0.25 in. (November 2007) to 0.32 in. (November 2009).
The licensee, subject to GL 88-01, "NRC Position on IGSCC [intergranular stress corrosion cracking] in BWR Austenitic Stainless Steel Piping," sought NRC approval of the flaw evaluation prior to the resumption of operation of Dresden, Unit 2. The NRC staff reviewed the licensee's application and verbally approved the flaw evaluation on November 25, 2009, allowing the restart and operation of DNPS Unit 2 for an additional operating cycle without repair of Weld PD1A-D14.
This safety evaluation provides the written documentation of the NRC staffs verbal approval of the licensee's flaw evaluation for Weld PD1A-D14.
2.0 REGULATORY EVALUATION
The inservice inspection (lSI) of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) Class 1, Class 2, and Class 3 components shall be performed in accordance with Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," of the ASME Code and applicable editions and addenda as required by Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).
Enclosure
-2 Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the pre-service examination requirements, set forth in Section XI of the ASME Code to the extent practical within the limitations of design, geometry, and materials of construction of the components.
For BWR coolant pressure boundary piping, additional inspection guidance was documented in GL 88-01. The technical bases for these NRC positions can be found in NUREG-0313, Revision 2, "Technical Report on Material Selection and Processing Guidelines for BWR Coolant Pressure Boundary Piping." The BWRVIP Report 75-A, which contained revised inspection schedules that could be used as an alternative to the GL 88-01 schedule, represents the industry's effort up to now in controlling IGSCC in BWR piping.
When flaws are detected by volumetric examinations, acceptance of the flaws by supplemental examination, repairs, replacement, or analytical evaluation shall be in accordance with ASME Code,Section XI, IWB-3130, "Inservice Volumetric and Surface Examinations." In this application, IWB-3600, "Analytical Evaluation of Flaws," specified in IWB-3132.3, "Acceptance by Analytical Evaluation," was applied by the licensee to demonstrate that the unit can be operated for an additional operating cycle without repair of the subject weld. These IWB subarticles are from the 1995 Edition through 1996 Addenda of the ASME Code,Section XI, which is the applicable ASME Code Edition for the current, fourth lSI interval at DNPS, Unit 2.
3.0 TECHNICAL EVALUATION
The circumferential flaw indication was originally discovered in 1986. The flaw indication was last reexamined during the refueling outage D2R21 by UT examination in accordance with BWRVIP Report 75-A. This reexamination indicated that although the flaw length remained unchanged at 1 in., the flaw depth has increased from 0.25 in. (November 2007) to 0.32 in.
(November 2009). The licensee's flaw sizing in 2007 and 2009 was appropriate considering that the UT results for both years were obtained using Performance Demonstration Initiative qualified personnel, equipment, and procedures.
The licensee's flaw evaluation considers both fatigue crack growth (FCG) and IGSCC and is based on the following conservative assumptions, adequate inputs, and acceptable criteria:
- 1. the flaw is conservatively assumed to extend 360 degrees circumferentially
- 2. the loads are from the revised 2004 recirculation piping stress analysis
- 3. residual stress is assumed to be 30 kilo-pounds per square inch (ksi), consistent with Section XI of the ASME Code
- 4. the cycles for the FCG calculation are conservatively assumed to be 1000
- 5. an acceptable noble metal chemical addition program is demonstrated to support use of the IGSCC growth rate of 1.1 x1 0-5 inches per hour (in/hr)
- 6. use of the ASME Code acceptance criteria As stated above, a 360-degree circumferential flaw is assumed to bound the subject flaw with a crack shape of 1 in. x 0.32 in. This assumption is conservative on the material resistance side
-3 considering that the allowable flaw depth in IWB-3600 for the subject flaw is 75 percent of the pipe thickness while the allowable flaw depth for the 360-degree circumferential flaw is only 60 percent. The flaw shape assumption is also conservative on the driving force side because the 360-degree circumferential flaw will overestimate the maximum applied stress intensity factor (Kmax) in the FCG calculation.
The licensee calculated the Kmax considering pressure. thermal. deadweight. and the residual stress and the minimum applied stress intensity factor (Kmin) considering only residual stresses.
The licensee then obtained a FCG of 0.0059 in. for the assumed 360-degree circumferential flaw for 1000 stress cycles using the crack growth law for austenitic material in the ASME Code.
The assumed 1000 cycles more than doubles the total number of startup and shutdown cycles that DNPS Unit 2 will likely experience over its lifetime and. hence. is conservative. Treating pressure and deadweight as cyclic loads contributes additional conservatism in the FCG calculation. For IGSCC. the licensee used a growth rate of 1.1 x1 0-5 in/hr and obtained an IGSCC growth of 0.193 in. over 2 years. Adding these two degradation mechanisms would give a final crack depth of 0.519 inch. or 37.7 percent of the pipe wall thickness, significantly less than the allowable flaw depth of 60 percent of the pipe wall thickness for a 360-degree circumferential flaw.
Although the examination coverage for the weld is not 100 percent (the actual coverage is 87.75 percent), the conservatism in the flaw evaluation regarding the flaw shape and the FCG calculation, and the margin between the predicted flaw depth and the allowable flaw depth, are sufficient to account for the low probability of having a very deep flaw in the uncovered area of 12.25 percent. Hence. the subject flaw will meet the ASME Code,Section XI. IWB-3640 requirements at the end of an additional operating cycle.
4.0 CONCLUSION
S The NRC staff finds that the licensee's flaw evaluation meets the requirements in the 1995 Edition through 1996 Addenda of Section XI of the ASME Code. Since the projected flaw depth.
considering 2 years of crack growth, is bounded by the allowable flaw depth. the DNPS, Unit 2.
can be restarted and operated without repair of the Weld PD1A-D14 for an additional operating cycle.
The NRC staff conclusions were verbally communicated to the licensee during a conference call on November 25,2009. prior to resumption of operations.
Principle Contributor: S. Sheng. NRR Date: June 11, 2010
ML093290088), Exelon Generation Company, LLC (EGC or the licensee), submitted for Nuclear Regulatory Commission (NRC) staff review, a flaw evaluation report for Dresden Nuclear Power Station (DNPS), Unit 2, regarding a circumferential flaw indication in Weld PD1A-D14, which is located on the downstream side of a 28-inch recirculation pump A discharge elbow-to-pipe weld. The examination of the flaw indicated that, although the flaw length remained unchanged at 1 inch, the flaw depth has increased from its previous examination from 0.25 inch (November 2007) to 0.32 inch (November 2009). The flaw indication does not meet the acceptance standards for continued operation without repair or replacement, or flaw evaluation in accordance with the American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code (Code)Section XI, 1995 Edition through the 1996 Addenda, which is the current code of record for the fourth inservice inspection interval for DNPS, Unit 2.
The licensee requested NRC staff approval of the pipe flaw evaluation for Weld PD1A-D14 to support the start up and operation of DNPS, Unit 2, following refueling outage D2R21. The licensee proposed to leave the weld as-is without repair for the following cycle.
The NRC staff has completed its review of the submittal and supplemental information and found that the licensee's flaw evaluation meets the rules in the 1995 Edition through 1996 Addenda of Section XI of the ASME Code. On November 25, 2009, the NRC staff verbally accepted the licensee's flaw evaluation, authorizing the licensee to operate DNPS, Unit 2, for an additional cycle. The enclosed safety evaluation is a written confirmation of the verbal authorization.
Sincerely, IRA!
Christopher Gratton, Senior Project Manager Plant Licensing Branch 111-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-237
Enclosure:
Safety Evaluation cc w/encls: Distribution via Listserv DISTRIBUTION:
PUBLIC LPL3-2 RlF RidsNrrDorlLpl3-2 Resource SSheng, NRR RidsNrrPMDresden Resource RidsNrrLATHarris Resource RidsAcrsAcnw_MailCTR Resource RidsOgcRp Resource RidsRgn3MailCenter Resource RidsNrrDorlDpr Resource ADAMS Accession No. ML101610188 *SE dated NRR-106 DCI/CVIB*
OFFICE LPL3-2/PM LPL3-2/LA LPL3-2/BC SCampbell NAME CGratton THarris MMitchell DATE 6/10/10 6/10/10 5/18 110 6/11/10