ML071290011
| ML071290011 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 05/23/2007 |
| From: | Russell Gibbs NRC/NRR/ADRO/DORL/LPLIII-2 |
| To: | Crane C Exelon Generation Co |
| kuntz, Robert , NRR/DORL, 415-3733 | |
| References | |
| TAC MD5230 | |
| Download: ML071290011 (9) | |
Text
May 23, 2007 Mr. Christopher M. Crane President and Chief Nuclear Officer Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
BYRON STATION, UNIT NO. 2 - RELIEF REQUEST I3R-14 FOR THE EVALUATION OF PROPOSED ALTERNATIVES FOR INSERVICE INSPECTION EXAMINATION REQUIREMENTS (TAC NO. MD5230)
Dear Mr. Crane:
By letter dated April 13, 2007, as supplemented by letter dated April 13, 2007, Exelon Generation Company, LCC (the licencee), submitted Relief Request I3R-14, which requested relief from specific requirements in the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for the Byron Station, Unit No. 2. The licensee proposed to use an embedded flaw repair process on vessel head penetration nozzle number 68 as an alternative to the ASME Code,Section XI requirements that preclude welding over or embedding an existing flaw.
Based on the enclosed safety evaluation, the NRC staff concludes that the proposed alternative provides an acceptable level of quality and safety. Therefore, pursuant to Title 10 of the Code of Federal Regulations, Section 50.55a(a)(3)(i), the NRC staff authorizes the proposed alternative in Relief Request I3R-14 to the repair requirements of IWA-4411 of the ASME Code,Section XI at Byron Station, Unit No. 2. The relief request is authorized for the third 10-year inservice inspection interval, which is currently scheduled to end in 2016.
On April 16, 2007, the NRC staff and the licensee held a teleconference to discuss Relief Request I3R-14. During that teleconference the NRC staff verbally authorized the requested relief based on the information presented in the licensees April 13, 2007, letters. The NRC documents relief requests granted verbally and the basis, for that authorization. The enclosed is the NRC staffs evaluation of Relief Request I3R-14, and the bases for the previously granted verbal relief.
Sincerely,
/RA/
Russell Gibbs, Chief Plant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. STN 50-455
Enclosure:
Safety Evaluation cc w/encl: See next page
Mr. Christopher M. Crane May 23, 2007 President and Chief Nuclear Officer Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
BYRON STATION, UNIT NO. 2 - RELIEF REQUEST I3R-14 FOR THE EVALUATION OF PROPOSED ALTERNATIVES FOR INSERVICE INSPECTION EXAMINATION REQUIREMENTS (TAC NO. MD5230)
Dear Mr. Crane:
By letter dated April 13, 2007, as supplemented by letter dated April 13, 2007, Exelon Generation Company, LCC (the licencee), submitted Relief Request I3R-14, which requested relief from specific requirements in the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for the Byron Station, Unit No. 2. The licensee proposed to use an embedded flaw repair process on vessel head penetration nozzle number 68 as an alternative to the ASME Code,Section XI requirements that preclude welding over or embedding an existing flaw.
Based on the enclosed safety evaluation, the NRC staff concludes that the proposed alternative provides an acceptable level of quality and safety. Therefore, pursuant to Title 10 of the Code of Federal Regulations, Section 50.55a(a)(3)(i), the NRC staff authorizes the proposed alternative in Relief Request I3R-14 to the repair requirements of IWA-4411 of the ASME Code,Section XI at Byron Station, Unit No. 2. The relief request is authorized for the third 10-year inservice inspection interval, which is currently scheduled to end in 2016.
On April 16, 2007, the NRC staff and the licensee held a teleconference to discuss Relief Request I3R-14. During that teleconference the NRC staff verbally authorized the requested relief based on the information presented in the licensees April 13, 2007, letters. The NRC documents relief requests granted verbally and the basis, for that authorization. The enclosed is the NRC staffs evaluation of Relief Request I3R-14, and the bases for the previously granted verbal relief.
Sincerely,
/RA/
Russell Gibbs, Chief Plant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. STN 50-455
Enclosure:
Safety Evaluation cc w/encl: See next page DISTRIBUTION:
PUBLIC RidsNrrDciCpnb LPL3-2 R/F RidsOgcRp RidsNrrDorlLpl3-2 RidsAcrsAcnwMailCenter RidsNrrPMRKuntz JCollins, NRR RidsNrrLAEWhitt RidsRgn3MailCenter TBloomer, EDO Region III Accession Number:ML071290011 NRR-028 *see memo dated OFFICE LPL3-2/PM LPL3-2/LA DCI/CPNB/BC OGC LPL3-2/BC NAME RKuntz EWhitt TChan*
JBiggins RGibbs DATE 5/11/07 5/11/07 5/1/07 5/16/07 5/23/07 OFFICIAL RECORD COPY
Byron Station, Units 1 and 2 cc:
Regional Administrator, Region III U.S. Nuclear Regulatory Commission 2443 Warrenville Road, Suite 210 Lisle, IL 60532-4351 Illinois Emergency Management 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 Mr. Dwain W. Alexander, Project Manager Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, PA 15230 Howard A. Learner Environmental Law and Policy Center of the Midwest 35 East Wacker Drive Suite 1300 Chicago, IL 60601-2110 U.S. Nuclear Regulatory Commission Byron Resident Inspectors Office 4448 North German Church Road Byron, IL 61010-9750 Ms. Lorraine Creek RR 1, Box 182 Manteno, IL 60950 Chairman, Ogle County Board P.O. Box 357 Oregon, IL 61061 Mrs. Phillip B. Johnson 1907 Stratford Lane Rockford, IL 61107 Attorney General 500 S. Second Street Springfield, IL 62701 Plant Manager - Byron Station Exelon Generation Company, LLC 4450 N. German Church Road Byron, IL 61010-9794 Site Vice President - Byron Station Exelon Generation Company, LLC 4450 N. German Church Road Byron, IL 61010-9794 Senior Vice President - Operations Support Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Chairman Will County Board of Supervisors Will County Board Courthouse Joliet, IL 60434 Director - Licensing and Regulatory Affairs Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Manager Regulatory Assurance - 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 - Regulatory Affairs Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555
Byron Station, Units 1 and 2 cc:
Manager Licensing - Braidwood, Byron and LaSalle Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Senior Vice President - Midwest Operations Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Mr. Barry Quigley 3512 Louisiana Rockford, IL 61108
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO RELIEF REQUEST NO. I3R-14 THIRD 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN EXELON GENERATION COMPANY, LLC BYRON STATION, UNIT NO. 2 DOCKET NO. STN 50-455
1.0 INTRODUCTION
By letter dated April 13, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML071030180), as supplemented by letter dated April 13, 2007 (ADAMS Accession No. ML071030413), Exelon Generation Company, LCC (the licensee),
submitted Relief Request I3R-14. The licensee requested relief from specific requirements in the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for Byron Station (Byron), Unit No. 2, to use an embedded flaw repair technique to repair vessel head penetration (VHP) nozzle number 68. This technique would be used in lieu of the ASME Code,Section XI requirements that preclude welding over or embedding an existing flaw. The request is based on the use of the Westinghouse repair methodology as documented in WCAP-15987-P, Revision 2, Technical Basis for the Embedded Flaw Process for Repair of Reactor Vessel Head Penetrations, which was reviewed and approved by the NRC staff in a July 3, 2003, safety evaluation (SE) (ADAMS Accession No. ML031840237).
2.0 REGULATORY REQUIREMENTS The Inservice Inspection (ISI) of the ASME Code Class 1, 2, and 3 components is to be performed in accordance with Section XI of the ASME Code and applicable edition and addenda as required by Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(g), except where specific relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). Section 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 be conducted during the first 10-year interval and subsequent intervals. These tests must 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), 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The ISI Code of Record for Byron, Unit No. 2, third 10-year ISI interval which started in 2006 is the 2001 Edition, 2003 Addenda of Section XI of the ASME Code.
3.0 TECHNICAL EVALUATION
3.1 Inservice Inspection Program Relief Request I3R-14 3.1.1 ASME Code Components Affected Relief Request I3R-14 would allow the licensee to repair VHP nozzle number 68 and its associated J-groove weld, by using the embedded flaw repair methodology as referenced by WCAP-15987-P, Revision 2, in lieu of the applicable ASME Code requirements of Section XI.
3.1.2 Code Requirements for which Relief is Requested ASME Code,Section XI, IWA-4420(c) requires that defect removal or mitigation by welding be in accordance with IWA-4411.
ASME Code,Section XI, IWA-4411 requires that welding, brazing, and installation activities be performed in accordance with the Owners Requirements and, with certain exceptions, the Construction Code (ASME Code Section III) of the component or system.
ASME Code,Section III, NB-4131 states, in part, that in order to repair defects in base metals, the defect must be removed, repaired and examined in accordance with the requirements of NB-2500.
ASME Code,Section III, NB-2538 addresses elimination of base material surface defects and specifies defects are to be removed by grinding or machining. Defect removal must be verified by a magnetic particle or liquid penetrant examination using acceptance criteria of NB-2545 or NB-2546. If the removal process reduces the section thickness below the NB-3000 design thickness, then repair welding per NB-2539 is to be performed.
ASME Code,Section III, NB-2539.1 addresses removal of defects and requires defects be removed or reduced to an acceptable size by suitable mechanical or thermal methods.
ASME Code,Section III, NB-2539.4 provides the rules for examination of the base material repair welds and specifies that they shall be examined by magnetic particle or liquid penetrant methods in accordance with NB-2545 or NB-2546. Additionally, if the depth of the repair cavity exceeds the lesser of 3/8 inch or 10 percent of the section thickness, the repair weld shall be examined by the radiographic method in accordance with NB-5110 using the acceptance standards of NB-5320.
ASME Code,Section III, NB-4451 states that unacceptable defects in weld metal be eliminated and, when necessary, repaired in accordance with NB-4452 and NB-4453.
ASME Code,Section III, NB-4452 addresses elimination of weld metal surface defects and specifies defects are to be removed by grinding or machining. Defect removal must be verified by a magnetic particle or liquid penetrant examination using acceptance criteria of NB-5340 or NB-5350. NB-4453.4 also specifies that repairs of 3/8 inch or 10 percent, whichever is less, be verified by a magnetic particle or liquid penetrant examination. If the removal process reduces the section thickness below the NB-3000 design thickness, then repair welding per NB-4453 is to be performed.
ASME Code,Section III, NB-4453.1 addresses the removal of defects in welds and requires the defect removal to be verified with magnetic particle or liquid penetrant examinations in accordance with NB-5340 or NB-5350.
3.1.3 Licensees Proposed Alternative to Code As an alternative to the requirements discussed above, which do not allow welding over or embedding an existing flaw, the licensee stated that it would use the proposed alternative method outlined in Westinghouse Topical Report WCAP-15987-P Revision 2, to repair VHP nozzle number 68 and its associated J-groove weld.
3.1.4 Licensees Basis for Relief The licensees bases for the design, implementation of repairs, and inspections for VHP nozzle number 68 will be consistent with Westinghouse WCAP-15987, Revision 2-A, and Westinghouse WCAP-16401-P, Revision 0, Technical Basis for Repair Options for Reactor Vessel Head Penetration Nozzles and Attachment Welds: Byron and Braidwood Units 1 and 2. The proposed alternative repair methods have been previously demonstrated to be adequate to allow weld repairs of embedded axial flaws in the outside diameter surface of VHP nozzles at or below the J-groove weld and similar flaws in the J-groove weld itself.
In a letter dated July 3, 2003 (ADAMS Accession No. ML031840237), from H. N. Berkow (NRC) to H. A. Sepp (Westinghouse Electric Company), the NRC staff provided an SE, in which the staff found WCAP-15987-P, Revision 2 to be acceptable for referencing in licensing applications as an alternative to the 2001 Edition, 2003 Addenda of Section XI of the ASME Code, with the following limitations:
- 1.
Licensees must follow the NRC flaw evaluation guidelines provided in the R. J. Barrett (NRC) letter to A. Marion (Nuclear Energy Institute), Flaw Evaluation Guidelines, April 11, 2003. (ADAMS Accession No. ML030980322)
- 2.
The crack growth rate referenced in WCAP-15987-P, Revision 2 is not applicable to Alloy 600 or Alloy 690 weld material, i.e., Alloy 52, 82, 152, and 182 filler material.
- 3.
The non-destructive examination (NDE) requirements listed in the table below must be implemented for examinations of repairs made using the embedded flaw process.
Repair Location Flaw Orientation Repair Weld Repair NDE ISI NDE of the repair, Note 2 VHP nozzle outside diameter (OD) below J-groove weld Axial or Circumferential Seal Ultrasonic Test (UT) or Surface UT or Surface J-groove weld Axial Seal UT and Surface, Note 3 UT and Surface, Note 3 J-groove weld Circumferential Seal UT and Surface, Note 3 UT and Surface, Note 3 Notes: 1.
Repairs must be reviewed and approved separately by the NRC. This note is not applicable to the Byron, Unit No. 2 repair.
- 2.
Inspect consistent with the NRC Order EA-03-009 dated February 11, 2003, and any subsequent changes.
- 3.
Inspect with personnel and procedures qualified with UT performance-based criteria. Examine the accessible portion of the repaired region. The UT coverage plus surface coverage must equal 100 percent.
In accordance with these limitations, and through a plant specific technical basis for the embedded flaw repair, the licensee confirms that the NRC flaw evaluation guidelines have been followed and the appropriate NDE will be implemented for the repairs to VHP nozzle number 68 and its associated J-groove weld at Byron, Unit No. 2. In accordance with the July 3, 2003, SE, the embedded flaw repair process is considered to be an alternative to the ASME Code requirements that provides an acceptable level of quality and safety, as required by 10 CFR 50.55a(a)(3)(i).
3.2 NRC STAFF EVALUATION The NRC staff has reviewed Westinghouse Topical Report WCAP-15987-P, Revision 2, and in a letter dated July 3, 2003, the NRC staff accepted the referencing of the topical report for use.
The licensee stated that it would use this Westinghouse topical report and would follow the conditions and limitations identified above.
The licensee provided WCAP-16401-P, Revision 0, as additional technical basis for use of the embedded flaw repair for VHP nozzle number 68 and its associated J-groove weld. NRC staff confirmed WCAP-16401-P, Revision 0, provided a bounding analysis for use of the embedded flaw repair method for VHP nozzle number 68 and its associated J-groove weld. The analysis, as documented in WCAP-16401-P, Revision 0, shows that the repair will meet the ASME Code,Section XI, requirements for allowable flaw size for the duration of the design life of the reactor vessel head and 10 years of operation for the J-groove weld, which would extended beyond the period relief has been requested (i.e. the third 10-year interval scheduled to end in 2016).
The licensee stated that future inspections of VHP nozzle number 68 and associated J-groove weld would be performed in accordance with the requirements of the First Revised NRC Order EA-03-009, dated February 20, 2004 (Order). This includes Note 3 of the Order which states, in part, For RPV [reactor pressure vessel] head penetration nozzles or J-groove welds repaired using a weld overlay, the overlay shall be examined by either ultrasonic, eddy current, or dye penetrant testing in addition to the examinations required by paragraph IV.C.(5)(a) and paragraph IV.C.(5)(b). These inspections will be performed each refueling outage as Note 3 is applicable to plants with a high susceptibility to primary water stress corrosion as defined by Section IV.B. of the Order.
Therefore, the NRC staff finds the use of the reactor vessel head penetration repair methodology as described in WCAP-15987-P, Revision 2, provides an acceptable level of quality and safety for use on VHP nozzle number 68 and associated J-groove weld at Byron, Unit No. 2, for the third 10-year ISI interval.
4.0 CONCLUSION
The NRC staff concludes that the proposed alternatives as stated in Relief Request I3R-14 provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i),
the NRC staff authorizes the proposed alternative, as described in Relief Request I3R-14, to the flaw repair requirements of IWA-4411, of ASME Code,Section XI and the related requirements listed under Section 2.2 of this SE, at Byron, Unit No. 2, for the third 10-year ISI interval.
All other requirements of the ASME Code, Sections III and XI for which relief has not been specifically requested and approved remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: J. Collins Date: May 23, 2007