ML050450576

2/25/05, Byron - Request for Relief I2R-50 from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code

ML050450576
Person / Time
Site:	Byron
Issue date:	02/25/2005
From:	Suh G NRC/NRR/DLPM/LPD3
To:	Crane C Exelon Generation Co
Dick G F, NRR/DLPM, 415-3019
References
TAC MC5046
Download: ML050450576 (9)

Text

February 25, 2005 Mr. Christopher M. Crane, President and Chief Nuclear Officer Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

BYRON STATION, UNIT 1 - REQUEST FOR RELIEF I2R-50 FROM THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) BOILER AND PRESSURE VESSEL CODE (CODE) (TAC NO. MC5046)

Dear Mr. Crane:

By letter dated November 5, 2004 (ML043150451), Exelon Generation Company, LLC (Exelon) submitted for approval, inservice inspection (ISI) relief request I2R-50 for the second 10-year ISI interval at Byron Station, Unit 1 (Byron 1). Exelon's request was for approval to use an alternate flaw depth sizing tolerance when performing ultrasonic examinations of dissimilier metal welds from the inside surface of piping. Specifically, Exelon requested relief from the 0.125 inch root mean square error (RMSE) sizing error in paragraph 3.2(b), "Sizing Acceptance Criteria," of ASME Code,Section XI, 1995 Edition, 1996 Addenda, Appendix VIII, Supplement 10, "Qualification Requirements for Dissimilar Metal Pipe Welds," as modified by ISI relief request authorized in NRC letter of July 16, 2003 (ML031970111).

The U. S. Nuclear Regulatory Commission staff reviewed Exelon's request and concludes that the proposal of adding the difference between the Code-required RMSE and the demonstrated accuracy to the measurements acquired from flaw sizing of the subject welds, in addition to the use of the acceptance standards specified in IWB-3500 of the Code, provides an acceptable level of quality and safety.

M. Crane Therefore, Exelon's proposed alternative is authorized in accordance with 10 CFR 50.55a(a)(3)(I) for the remainder of the second 10-year ISI interval at Byron 1.

Sincerely,

/RA/

Gene Y. Suh, Chief, Section 2 Project Directorate III Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. STN 50-454

Enclosure:

Safety Evaluation cc w/ encl: See next page

ML050450576 OFFICE PDIII-2/PM PDIII-2/LA EMCB:SC OGC PDIII-2/SC NAME GDick PCoates TChan SZiphin GSuh DATE 02/25/05 2/16/05 2/9/05 2/25/05 2/25/05 Byron Station Units 1 and 2 cc:

Regional Administrator, Region III Chairman, Ogle County Board U.S. Nuclear Regulatory Commission Post Office Box 357 801 Warrenville Road Oregon, IL 61061 Lisle, IL 60532-4351 Mrs. Phillip B. Johnson Illinois Emergency Management 1907 Stratford Lane Agency Rockford, IL 61107 Division of Disaster Assistance &

Preparedness Attorney General 110 East Adams Street 500 S. Second Street Springfield, IL 62701-1109 Springfield, IL 62701 Document Control Desk - Licensing Byron Station Plant Manager Exelon Generation Company, LLC Exelon Generation Company, LLC 4300 Winfield Road 4450 N. German Church Road Warrenville, IL 60555 Byron, IL 61010-9794 Mr. Dwain W. Alexander, Project Manager Site Vice President - Byron Westinghouse Electric Corporation Exelon Generation Company, LLC Energy Systems Business Unit 4450 N. German Church Road Post Office Box 355 Byron, IL 61010-9794 Pittsburgh, PA 15230 Senior Vice President - Nuclear Services Joseph Gallo Exelon Generation Company, LLC Gallo & Ross 4300 Winfield Road 1025 Connecticut Ave., NW, Suite 1014 Warrenville, IL 60555 Washington, DC 20036 Vice President of Operations - Mid-West Howard A. Learner Pressurized Water Reactors Environmental Law and Policy Exelon Generation Company, LLC Center of the Midwest 4300 Winfield Road 35 East Wacker Drive Warrenville, IL 60555 Suite 1300 Chicago, IL 60601-2110 Chairman Will County Board of Supervisors U.S. Nuclear Regulatory Commission Will County Board Courthouse Byron Resident Inspectors Office Joliet, Illinois 60434 4448 North German Church Road Byron, IL 61010-9750 Ms. Lorraine Creek RR 1, Box 182 Manteno, IL 60950

Byron Station Units 1 and 2 Director - Licensing and Regulatory Affairs Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Regulatory Assurance Manager - Byron Exelon Generation Company, LLC 4450 N. German Church Road Byron, IL 61010-9794 Associate General Counsel Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Vice President -

Licensing and Regulatory Affairs Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Manager Licensing - Braidwood and Byron Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO REQUEST FOR RELIEF I2R-5O SECOND 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN BYRON STATION, UNIT 1 EXELON GENERATION COMPANY, LLC DOCKET NUMBER STN 50-454

1.0 INTRODUCTION

By letter dated November 5, 2004 (ML043150451), Exelon Generation Company, LLC (the licensee) submitted for approval, inservice inspection (ISI) relief request I2R-50 for the second 10-year ISI interval at Byron Station, Unit 1 (Byron 1). The licensee's request was for approval to use an alternate flaw depth sizing tolerance when performing ultrasonic examinations of dissimiliar metal welds from the inside surface of piping. Specifically, the licensee requested relief from the 0.125 inch root mean square error (RMSE) sizing error in paragraph 3.2(b),

"Sizing Acceptance Criteria," of ASME Code,Section XI, 1995 Edition, 1996 Addenda, Appendix VIII, Supplement 10, "Qualification Requirements for Dissimilar Metal Pipe Welds," as modified by ISI relief request authorized in NRC letter of July 16, 2003 (ML031970111).

2.0 REGULATORY EVALUATION

The inservice inspection of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) Class 1, Class 2, and Class 3 components is performed in accordance with Section XI of the ASME Code and applicable edition and addenda as required by 10 CFR 50.55a(g), except where specific relief has been granted by the Commission pursuant to Section 50.55a(g)(6)(I) of Title 10 of the Code of Federal Regulations (10 CFR).

10 CFR 50.55a(a)(3) states in part that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if the licensee demonstrates that: (I) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) will meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) twelve months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The inservice inspection (ISI) Code of record for the second 10-year ISI interval at Byron 1 is the 1989 Edition. The components

(including supports) may meet the requirements set forth in subsequent editions and addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(b) subject to the limitations and modifications listed therein and subject to Commission approval.

3.0 TECHNICAL EVALUATION

3.1 Components for Which Relief is Requested Code Class 1 Pressure Retaining Dissimilar Metal Welds - Reactor Vessel Nozzle-to-Safe End Welds subject to examinations using procedures, personnel, and equipment qualified to the 1995 Edition with the 1996 Addenda fo the ASME Code,Section XI, Appendix VIII, Supplement 10, "Qualification Requirements for Dissimilar Metal Piping Welds" as identified below.

Nozzle-to-Safe End Welds Description Weld Number RPV Nozzle to Safe End Hot Leg Loop C 1RC-01-R/RPVS-A/F1 RPV Nozzle to Safe End Cold Leg Loop C 1RC-01-R/RPVS-B/F1 RPV Nozzle to Safe End Hot Leg Loop D 1RC-01-R/RPVS-C/F1 RPV Nozzle to Safe End Cold Leg Loop D 1RC-01-R/RPVS-D/F1 RPV Nozzle to Safe End Hot Leg Loop A 1RC-01-R/RPVS-E/F1 RPV Nozzle to Safe End Cold Leg Loop A 1RC-01-R/RPVS-F/F1 RPV Nozzle to Safe End Hot Leg Loop B 1RC-01-R/RPVS-G/F1 RPV Nozzle to Safe End Cold Leg Loop B 1RC-01-R/RPVS-H/F1 3.2 Applicable Code Requirements The current inservice inspection program is based on the ASME Code,Section XI, 1989 Edition with no Addenda. The ultrasonic examination of applicable Class 1 and 2 components is governed by Appendix VIII, "Performance Demonstration for Ultrasonic Examination Systems,"

of the ASME Code,Section XI, 1995 Edition with the 1996 Addenda.

The 1995 Edition with the 1996 Addenda of the ASME Code,Section XI, Appendix VIII, Supplement 10, Paragraph 3.2(b), states that the examination procedures, equipment, and personnel are qualified for depth sizing when the root mean square error (RMSE) of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to 0.125 inch RMSE.

3.3 Licensees Proposed Alternative and Basis for Use (As Stated)

Pursuant to 10 CFR 50.55a(a)(3)(I), relief is requested for an alternative requirement that will provide an acceptable level of quality and safety. EGC requests relief to consider examination procedures, equipment, and personnel qualified for depth sizing when the RMSE of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to 0.189 inch for the ultrasonic examination of dissimilar metal welds performed from the inside surface of the pipe at Byron Station, Unit 1. The RMSE of 0.189 inch is based on actual vendor demonstrated, in-process, field qualifications and is the optimum value that could be achieved.

The proposed procedure to address sizing of the flaws that may be detected during the examination is to add the difference between the 0.189-inch achieved sizing error and the 0.125-inch RMSE Appendix VIII, Supplement 10 acceptance criteria to the measured flaw size.

EGC considers the use of this difference (0.064 inch) as an adjustment to the measured flaw will ensure a conservative bounding depth value for dissimilar metal welds at Byron Station, Unit 1.

3.4 NRC Staffs Evaluation Supplement 10 of Appendix VIII to ASME Section XI requires that examination procedures, equipment, and personnel meet specific criteria for flaw depth sizing accuracy. The Code specifies that the maximum error of flaw depth measurements, as compared to the true flaw depths, must be less than or equal to 0.125 inch RMSE. The industry is in the process of qualifying personnel to Supplement 10 as implemented by the Performance Demonstration Initiative (PDI) program. However, for demonstrations performed from the inside surface of a pipe weldment, personnel have been unsuccessful at achieving the 0.125 inch RMSE depth sizing criterion. At this time, achieving the 0.125 inch RMSE appears to not be feasible.

Personnel have only been capable of achieving an accuracy of 0.189 inch RMSE. The vendor contracted by the licensee has proposed to use 0.189 inch RMSE to size any detected flaws during the forthcoming outage (Spring 2005). The licensee would add the difference (0.064 inch) between the Code acceptance value (0.125 inch RMSE) and the demonstrated accuracy (0.189 inch RMSE) to the measurements acquired from flaw sizing. The use of this adjustment to flaw depth measurements will ensure a conservative bounding flaw depth value.

The staff finds that compliance with the Code-required RMSE value is currently not feasible and that by adding the difference between the Code-required RMSE and the demonstrated accuracy to the measurements acquired from flaw sizing, in addition to the to the use of the acceptance standards specified in IWB-3500 of the Code, provides an acceptable level of quality and safety.

4.0 CONCLUSION

S Based on the above evaluation, the staff has determined that requiring the licensee to qualify procedures, personnel, and equipment to meet the maximum error of 0.125 inch RMSE for crack depth sizing is not feasible at the present time. The licensees proposal of adding the difference between the Code-required RMSE and the demonstrated accuracy to the measurements acquired from flaw sizing of the subject welds, in addition to the to the use of the

acceptance standards specified in IWB-3500 of the Code, provides an acceptable level of quality and safety. Therefore, the licensees alternative is authorized in accordance with 10 CFR 50.55a(a)(3)(I) for the remainder of the second 10-year ISI interval at Byron 1.

Principal contributor: A. Keim Date: February 25, 2005