ML042360344

Relief Request, CR-27 for Third 10-Year Inservice Inspection Interval. TAC No. MC3268

ML042360344
Person / Time
Site:	Dresden
Issue date:	09/16/2004
From:	Anthony Mendiola NRC/NRR/DLPM/LPD3
To:	Crane C Exelon Generation Co
Banerjee M, NRR/ADPT, 415-2277
References
TAC MC3268
Download: ML042360344 (9)

Text

September 16, 2004 Mr. Christopher M. Crane, President and Chief Nuclear Officer Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

DRESDEN NUCLEAR POWER STATION, UNIT 2 - RELIEF REQUEST CR-27 FOR THIRD 10-YEAR INSERVICE INSPECTION INTERVAL (TAC NO. MC3268)

Dear Mr. Crane:

By letter dated May 4, 2004, (ML041320453) Exelon Generation Company, LLC (the licensee) submitted a request for relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, for Dresden Nuclear Power Station, Unit 2. The relief request, CR-27, concerns the volumetric examinations conducted on the reactor pressure vessel longitudinal shell welds performed during the third 10-year inservice inspection (ISI) interval where the inspection coverage was less than 90 percent.

The Nuclear Regulatory Commission staff has evaluated the licensees submittal and concludes that it is impractical for the licensee to comply with the ASME Code requirements for which relief was requested. The staff finds that the proposed alternative and the examination coverages of the accessible weld volumes and of the surface areas provide reasonable assurance of the structural integrity of the welds identified in the relief request. Therefore, the requested relief is granted in accordance with Sections 50.55a(a)(3)(i) and 50.55a(g)(6)(ii)(A)(5) of Title 10 of the Code of Federal Regulations (10 CFR) for the licensees third 10-year ISI interval for Dresden Nuclear Power Station, Unit 2. The staff has concluded that the alternative proposed provides an acceptable level of quality and safety, and granting relief is authorized by law. Our safety evaluation is enclosed.

Sincerely,

/RA/

Anthony J. Mendiola, Chief, Section 2 Project Directorate III Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-237

Enclosure:

Safety Evaluation cc w/encl: See next page

September 16, 2004 Mr. Christopher M. Crane, President and Chief Nuclear Officer Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

DRESDEN NUCLEAR POWER STATION, UNIT 2 - RELIEF REQUEST CR-27 FOR THIRD 10-YEAR INSERVICE INSPECTION INTERVAL (TAC NO. MC3268)

Dear Mr. Crane:

By letter dated May 4, 2004, (ML041320453) Exelon Generation Company, LLC (the licensee) submitted a request for relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, for Dresden Nuclear Power Station, Unit 2. The relief request, CR-27, concerns the volumetric examinations conducted on the reactor pressure vessel longitudinal shell welds performed during the third 10-year inservice inspection (ISI) interval where the inspection coverage was less than 90 percent.

The Nuclear Regulatory Commission staff has evaluated the licensees submittal and concludes that it is impractical for the licensee to comply with the ASME Code requirements for which relief was requested. The staff finds that the proposed alternative and the examination coverages of the accessible weld volumes and of the surface areas provide reasonable assurance of the structural integrity of the welds identified in the relief request. Therefore, the requested relief is granted in accordance with Sections 50.55a(a)(3)(i) and 50.55a(g)(6)(ii)(A)(5) of Title 10 of the Code of Federal Regulations (10 CFR) for the licensees third 10-year ISI interval for Dresden Nuclear Power Station, Unit 2. The staff has concluded that the alternative proposed provides an acceptable level of quality and safety, and granting relief is authorized by law. Our safety evaluation is enclosed.

Sincerely,

/RA/

Anthony J. Mendiola, Chief, Section 2 Project Directorate III Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-237

Enclosure:

Safety Evaluation cc w/encl: See next page DISTRIBUTION:

PUBLIC PDIII-2 R/F WRuland AMendiola PCoates MBanerjee OGC GHill (2) ACRS MMitchell ADAMS Accession Number: ML042360344 *SE dated 7/29/04 OFFICE PM:PDIII-2 LA:PDIII-2 SC:EMCB-A OGC w/nlo SC:PDIII-2 NAME MBanerjee PCoates MMitchell* RHoefling AMendiola DATE 08/27/04 08/25/04 07/29/04 09/07/04 09/16/04 OFFICIAL RECORD COPY

Dresden Nuclear Power Units 2 and 3 cc:

Site Vice President - Dresden Nuclear Power Station Senior Vice President, Nuclear Services Exelon Generation Company, LLC Exelon Generation Company, LLC 6500 N. Dresden Road 4300 Winfield Road Morris, IL 60450-9765 Warrenville, IL 60555 Dresden Nuclear Power Station Plant Manager Vice President of Operations - Mid-West Exelon Generation Company, LLC Boiling Water Reactors 6500 N. Dresden Road Exelon Generation Company, LLC Morris, IL 60450-9765 4300 Winfield Road Warrenville, IL 60555 Regulatory Assurance Manager - Dresden Exelon Generation Company, LLC Vice President - Licensing and Regulatory 6500 N. Dresden Road Affairs Morris, IL 60450-9765 Exelon Generation Company, LLC 4300 Winfield Road U.S. Nuclear Regulatory Commission Warrenville, IL 60555 Dresden Resident Inspectors Office 6500 N. Dresden Road Director - Licensing and Regulatory Affairs Morris, IL 60450-9766 Exelon Generation Company, LLC 4300 Winfield Road Chairman Warrenville, IL 60555 Grundy County Board Administration Building Associate General Counsel 1320 Union Street Exelon Generation Company, LLC Morris, IL 60450 4300 Winfield Road Warrenville, IL 60555 Regional Administrator U.S. NRC, Region III Manager Licensing - Dresden, 801 Warrenville Road Quad Cities and Clinton Lisle, IL 60532-4351 Exelon Generation Company, LLC 4300 Winfield Road Illinois Emergency Management Warrenville, IL 60555 Agency Division of Disaster Assistance &

Preparedness 110 East Adams Street Springfield, IL 62701-1109 Document Control Desk - Licensing Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION THIRD 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM REQUEST FOR RELIEF NO. CR-27 EXELON GENERATION COMPANY, LLC DRESDEN NUCLEAR POWER STATION, UNIT 2 DOCKET NO. 50-237

1.0 INTRODUCTION

By letter dated May 4, 2004, (ML041320453) Exelon Generation Company (EGC) LLC, the licensee, requested relief from certain inservice examination requirements of the 1989 Edition of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, in regard to volumetric examinations conducted on the Dresden Nuclear Power Station (DNPS), Unit 2, reactor pressure vessel (RPV) longitudinal shell welds, performed during the third 10-year inservice inspection (ISI) interval where the inspection coverage achieved was less than or equal to 90 percent. The licensee stated that the ASME Code-required examination coverage of essentially 100 percent for the welds was not feasible or practical within the limits of the current plant design. Compliance with the examination requirements of ASME Code Section XI would require modifications of plant components to remove obstructions, redesign plant systems, and replacement of components where geometry is inherent to component design. However, all components received, as a minimum, the required examination(s) applicable to the extent practical due to limited or lack of access available. The staff has evaluated the reduction in examination coverage pursuant to Section 50.55a(g)(6)(ii)(A)(5) of Title 10 of the Code of Federal Regulations (10 CFR).

2.0 REGULATORY EVALUATION

Pursuant to 10 CFR 50.55a(g)(4), components (including supports) which are classified as ASME Code, Class 1, 2, and 3 shall meet the requirements, except the design and access provisions and the pre-service 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 120-month 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.

ENCLOSURE

Pursuant to 10 CFR 50.55a(g)(5)(iii), if the licensee has determined that conformance with certain ASME Code requirements is impractical for its facility, the licensee shall notify the Commission and submit, as specified in Section 50.4, information to support the determinations. Section 10 CFR 50.55a(g)(6)(i) states that the Commission will evaluate determinations under paragraph (g)(5) of this section that ASME Code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines is authorized by law, and will not endanger life or property or the common defense and security and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result, if the requirements were imposed on the facility.

In addition, if the licensee determines that they are unable to completely satisfy the requirements for the augmented RPV shell weld examination specified in 10 CFR 50.55a(g)(6)(ii)(A), they shall propose an alternative to the examination requirements that would provide an acceptable level of quality and safety.

2.1 Regulatory Background The applicable inservice inspection ASME Code edition of record for DNPS, Unit 2, is the 1989 Edition of the ASME Code,Section XI.

The staff previously approved an alternative RPV weld examination pursuant to the provisions of 10 CFR 50.55a paragraphs (a)(3)(i) and (g)(6)(ii)(A)(5) for DNPS, Units 2 and 3 (Reference 1). The alternative allows permanent deferral of requirements to perform a volumetric examination of RPV circumferential shell weld for the remaining of the DNPS, Units 2 and 3, 40 year operating licenses. The approved alternative requires inspections of essentially 100 percent of all longitudinal shell welds, and inspection of approximately 2 to 3 percent of the circumferential shell welds at their point of intersection with the longitudinal shell welds. On September 28, 2001, the NRC approved a one cycle extension of the requirement to inspect RPV longitudinal shell welds per the provision of 10 CFR 50.55a(a)(3)(ii) (Reference 2).

For DNPS Unit 2, the third 10-year ISI interval began on March 1, 1992, and ended on September 30, 2003. RPV longitudinal shell weld examinations were completed during the Unit 2 refueling outage which began on October 14, 2003, and was completed on November 11, 2003.

3.0 TECHNICAL EVALUATION

3.1 ASME Code Components Affected

Code Class: Class 1 Code Edition: 1989 Edition of the ASME Code,Section XI Examination Category: B-A Item Number: B1.12 Component Numbers: Various, see Table CR-27.1

3.2 ASME Code Requirements for which Relief is Requested (as stated)

In accordance with the provisions of 10 CFR 50.55a, "Codes and Standards," paragraphs (a)(3)(i) and (g)(6)(ii)(A)(5), Exelon Generation Company, LLC (EGC) requests relief for DNPS, Unit 2 from the requirements of the augmented examinations specified in 10 CFR 50.55a(g)(6)(ii)(A)(2), which was used as a substitute for the reactor vessel shell weld examination scheduled for the third Inspection interval as allowed by 10 CFR 50.55a(g)(6)(ii)(A)(2).

Augmented RPV examinations specified in 10 CFR 50.55a(g)(6)(ii)(A)(2) are subject to the conditions specified in 10 CFR 50.55a(g)(6)(ii)(A)(4) where examination of the reactor vessel may be satisfied by an examination of essentially 100% of the reactor vessel shell welds.

3.3 Licensees Proposed Alternative to the ASME Code and Bases for Use 3.3.1 Limits of Weld Volume Examination (as stated)

DNPS Unit 2 obtained Construction Permit CPPR-18 on January 10, 1966. The RPV was designed and fabricated before the examination requirements of ASME [Code] Section XI were formalized and published. Since this plant was not specifically designed to meet the requirements of ASME [Code] Section Xl, full compliance is not feasible or practical within the limits of the current plant design.

The RPV is examined from the internal surface to the extent practical. Further examination from the inside surface is not practical without disassembly of vessel internal components. The exterior vessel surface is covered with permanent insulation located in close proximity to the RPV outside surface. The lower exterior vessel surface is also covered with a structural steel biological shield wall. Supplemental manual examinations from the outside surface are not practical due to the biological shield wall, insulation, and dose considerations.

3.3.2 Proposed Alternative (as stated)

In accordance with 10 CFR 50.55a(a)(3)(i), and (g)(6)(ii)(A)(5), EGC proposes the following alternate provisions for the subject weld examinations since the proposed alternative provides an acceptable level of quality and safety.

The examination requirements specified in 10 CFR 50.55a(g)(6)(ii)(A)(2) for the RPV longitudinal shell welds shall be performed, to the extent possible. When this examination is performed, welds are examined from inside surfaces of the RPV using an automated ultrasonic inspection system, which provides the best possible examination of the RPV longitudinal shell welds. Additionally, a VT-2 examination is performed on the RPV during the system leakage test per examination category B-P each refueling outage.

3.3.3 Bases for Alternative (as stated)

The RPV longitudinal shell welds are ultrasonically examined utilizing a Performance Demonstration Initiative (PDI) qualified automated ultrasonic inspection system meeting the requirements of ASME Section XI, Appendix VIII.

All components received examination(s) to the extent practical due to the limited, or lack of access. The examinations conducted, confirmed satisfactory results evidencing no unacceptable flaws present, even though "essentially 100%" coverage was not attained.

Based on the above, with our earlier design, the underlying objectives of the [ASME] code required volumetric examinations have been met. The examinations were completed to the extent practical and evidenced no unacceptable flaws present. Additionally, a VT-2 examination performed during the system leakage test per examination category B-P each refueling outage provides additional assurance that the structural integrity of the RPV is maintained.

4.0 STAFF EVALUATION The ASME Code,Section XI, 1989 Edition, requires volumetric examination coverage of 100 percent of the reactor vessel shell welds. However, a reduction in examination coverage due to interferences of less than 10 percent is acceptable as provided by ASME Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 Welds, which has been approved by the NRC in Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1. ASME Code Case N-460 states that when the entire examination volume or area cannot be examined, a reduction in examination coverage may be accepted provided that the reduction in coverage is less than 10 percent. Furthermore, NRC Information Notice 98-42, Implementation of 10 CFR 50.55a(g) Inservice Inspection Requirements, states that the staff has adopted the definition of essentially 100 percent to mean greater than 90 percent.

During the third 10-year ISI interval, the RPV longitudinal shell welds identified in Table CR-27.1, in examination category B-A were ultrasonically examined resulting in volumetric coverage ranging from 35 percent to 88 percent in lieu of the ASME Code-required coverage in excess of 90 percent. The limitation in examination coverage was attributed to interferences associated with RPV internal components which restricted scanning.

The staff has determined that it is impractical to perform the ASME Code-required examination of the subject welds due to configuration or other interference that prevented complete ultrasonic scanning of the weld. In order to comply with the ASME Code requirements, a design modification of the reactor vessel and RPV internals would have to be performed which would impose a significant burden on the licensee. However, the staff believes that the examinations were conducted to the extent practical and provide reasonable assurance of structural integrity since any significant pattern of degradation should have been detected during examination of the accessible weld volume. Further, in the event that a service-induced flaw in the weld propagates, it would most likely be detected with the ASME Code-required VT-2 examination during the system leakage test.

5.0 CONCLUSION

The staff has reviewed the licensees submittal and concludes that compliance with the ASME Code requirements on examinations for the RPV welds identified in Table CR-27.1 are impractical due to configuration and/or obstructions associated with the welds. The staff has further determined that vessel internal components would have to be disassembled if the ASME Code requirements were to be imposed on the licensee. The staff finds that the proposed

alternative and the examination coverages of the accessible weld volumes and of the surface areas provide reasonable assurance of the structural integrity of the welds identified in the relief request, and hence, an acceptable level of quality and safety. Therefore, relief is granted from the ASME Code examination coverage requirements pursuant to 10 CFR 50.55a(3)(i) and 10 CFR 50.55a(g)(6)(ii)(A)(5) for the third 10-year ISI interval of Dresden, Unit 2. The relief granted provides an acceptable level of quality and safety, will not endanger life or property, and is authorized by law.

6.0 REFERENCES

1. Letter from NRC to Exelon, Dresden - Authorization for Proposed Alternative Reactor Pressure Vessel Circumferential Weld Examinations (TAC Nos. MA6228 and MA6229),

dated February 25, 2000. (ADAMS Accession # ML003685787)

2. Letter from NRC to Exelon Exemptions from the requirements of 10CFR 50.55a(g)(6)(ii)(A)(2), Inservice Examination of the Reactor Pressure Vessel, dated September 28, 2001. (ADAMS Accession #ML012320420)

Principal Contributor: V. Rodriguez, NRR/DE/EMCB Date: September 16, 2004

Table CR-27.1 Unit 2 RPV Longitudinal Shell Welds Relief Requested Weld Weld Coverage (Based on 90% Condition Limiting Coverage Identification Description Percent Coverage)

Shell Course 1 SC1A Yes Jet Pump Diffuser and Baffle Plate 88 Weld at 77 deg.

Shell Course 1 SC1B Yes Core Shroud Repair Tie Rod 35 Weld at 110 deg.

Jet Pump Diffuser, Diffuser Support Shell Course 1 SC1C Yes Pads, Recirculation Nozzle, Core 38 Weld at 197 deg.

Shroud Repair Tie Rod Shell Course 1 SC1D Yes Jet Pump Diffuser and Baffle Plate 86 Weld at 317 deg.

Jet Pump Riser Brace, Surveillance Shell Course 2 SC2A Yes Specimen Support Bracket, Core 72 Weld at 98 deg.

Shroud Repair Tie Rod Shell Course 2 Jet Pump Riser Brace, Surveillance SC2B Yes 76 Weld at 218 deg. Specimen Support Bracket Shell Course 2 Jet Pump Riser Brace, Surveillance SC2C Yes 83 Weld at 250 deg. Specimen Support Bracket Shell Course 2 SC2D No None 100 Weld at 338 deg.

Shell Course 3 Core Spray and Feedwater SC3A Yes 76 Weld at 77 deg. Spargers Shell Course 3 Core Spray and Feedwater SC3B Yes 77 Weld at 197 deg. Spargers Shell Course 3 Core Spray and Feedwater SC3C Yes 78 Weld at 296 deg. Spargers Shell Course 3 Core Spray and Feedwater SC3D Yes 83 Weld at 317 deg. Spargers Shell Course 3 Core Spray and Feedwater SC3E Yes 83 Weld at 353 deg. Spargers, Guide Rod Shell Course 4 SC4A No None 100 Weld at 99 deg.

Shell Course 4 SC4B No None 100 Weld at 150 deg.

Shell Course 4 SC4C Yes Steam Dryer Support Bracket 88 Weld at 210 deg.

Shell Course 4 SC4D No None 100 Weld at 330 deg.

Shell Course 4 SC4E No None 100 Weld at 339 deg.