RS-07-055, Inservice Inspection Relief Request I3R-14: Alternative Requirements for the Repair of a Reactor Vessel Head Penetration
| ML071030180 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 04/13/2007 |
| From: | Benyak D Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, NRC/NRR/ADRO |
| References | |
| RS-07-055 | |
| Download: ML071030180 (9) | |
Text
Exek,n~.Exelon Generation Company, LLC wwwexeloncorp.com N 1 Byron Station 4450 North German Church Road*Byron, IL 61010-9794 10 CFR 50.55a RS-07-055 April 13, 2007 U.S.Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Byron Station Unit 2 Facility Operating License No.NPF-66 NRC Docket No.STN 50-455
Subject:
Byron Station Unit 2 Inservice Inspection Relief Request l3R-14: Alternative Requirements for the Repair of a Reactor Vessel Head Penetration
References:
(1)Westinghouse WCAP-1 5987, Revision 2-A,"Technical Basis for the Embedded Flaw Process for Repair of Reactor Vessel Head Penetrations,"
December 2003 (2)Letter from H.N.Berkow (U.S.NRC)to H.A.Sepp (Westinghouse Electric Company),"Acceptance for Referencing
-Topical Report WCAP-15987-P, Revision 2,'Technical Basis for the Embedded Flaw Process for Repair of Reactor Vessel Head Penetration,'(TAG NO.MB8997),"dated July 3, 2003 In accordance with 10 CFR 50.55a,"Codes and standards,"
paragraph (a)(3)(i), Exelon Generation Company, LLC (EGC)is requesting relief from the American Society of Mechanical Engineers (ASME)Boiler and Pressure Vessel Code,Section XI,"Rules for Inservice Inspection of Nuclear Power Plant Components,"
on the basis that the proposed alternatives would provide an acceptable level of quality and safety.Specifically, a relief request is being proposed to perform an alternative repair technique using the embedding methodology of Reference 1 on the reactor vessel head penetration (VHP)housing and J-groove weld of Byron Station Unit 2 penetration number 68.The embedded flaw methodology to be used has been approved generically by the NRC in the Reference 2 safety evaluation.
The details of this request are contained~n Byron Station Relief Request l3R-14 attached to this letter.During the current Byron Station Unit 2 Spring 2007 Refueling Outage, EGG performed volumetric examinations of the VHPs in accordance with First Revised Order EA-03-009,"Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactor,"(the Order).Ultrasonic examination identified an unacceptable axial indication, confirmed by dye penetrant examination, in VHP 68.
April 13, 2007 U.S.Nuclear Regulatory Commission Page 2 Although a root-cause has not been completed and the damage mechanism has not been confirmed, the repair process conservatively assumes the indication is the result of primary water stress corrosion cracking (PWSCC)and embedding the flaw within PWSCC resistant materials (i.e., Alloy 52 weld metal)will assure structural integrity of the VHP 68 connection.
Supporting the embedded flaw methodology application to the VHP5 for Byron Station Unit 2 is the analysis provided in Westinghouse WCAP-1 6401-P, Revision 0,'Technical Basis for Repair Options for Reactor Vessel Head Penetration Nozzles and Attachment Welds: Byron and Braidwood Units 1 and 2."This WCAP provides the technical basis for the use of an embedded repair involving the VHP housing and/or the VHP housing attachment weld (i.e., the J-groove weld)by evaluating the bounding loading conditions, fatigue crack growth predications, and fracture mechanics results.WCAP-16401-P will be submitted to the NRC in a separate letter, following completion of an affidavit to support withholding of proprietary information.
EGG requests that this repair alternative be verbally approved by April 17, 2007, to support the VHP repair and restoration/restart activities at Byron Station Unit 2.While EGG recognizes the burden associated with an accelerated review and approval of l3R-14, the need for a repair of a VHP at Byron Station Unit 2 as a result of the Order examinations was unexpected.
Byron Station Unit 2 is ranked as a low susceptibility plant with an Effective Degradation Year rating of 2.2 with a very low probability of PWSCC initiation and consequently, there was no expected need to prepare and submit, for NRC review, a contingency Relief Request for an alternative repair methodology in advance of the Byron Station Unit 2 refueling outage.There are no regulatory commitments contained in this submittal.
If you have any questions about this letter, please contact Mr.David Ghrzanowski at (630)657-2816.Respectfully, Darin M.Benyak Director, Licensing and Regulatory Affairs Attachment
-Byron Station Relief Request 13R-14,"Alternative Requirements for the Repair of a Reactor Vessel Head Penetration" Attachment Byron Station Relief Request 13R-14 Alternative Requirements for the Repair of a Reactor Vessel Head Penetration IS!Program Plan Unit 2, Third Interval 10 CFR 50.55a (RELIEF REQUEST 13R-14 Revision 0 Page 1 of 6)Request for Relief Alternative Requirements for the Repair of a Reactor Vessel Head Penetration In Accordance with 10 CFR 50.55a(a)(3)(i) 1.0 ASME CODE COMPONENT AFFECTED Code Class: 1
Reference:
NRC First Revised Order EA-03-009 Identification:
Byron Unit 2 Reactor Vessel Head Penetration (VHP)68
Description:
VHP Housing to Reactor Vessel Head Partial Penetration Weld (J-Groove Weld)Drawing Numbers: 185282E Revision 0, 185283E Revision 1, and 185286E Revision 1 2.0 APPLICABLE CODE EDITION AND ADDENDA American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, 2001 Edition, through 2003 Addenda.3.0 APPLICABLE CODE REQUIREMENT ASME Section Xl, 2001 Edition, through 2003 Addenda, requires repair activities to be conducted in accordance with the requirements of IWA-4000.ASME Section Xl, IWA-441 1 requires that welding, brazing, and installation be performed in accordance with the Owner's Requirements and the original Construction Code of the item.The original Code of Construction for the reactor vessel closure head and VHP housings is ASME Section III, 1971 Edition through Summer 1973 Addenda.ASME Section XI, IWA-4421 (c)states that defect removal or mitigation by welding or brazing be performed in accordance with IWA-441 1.Base Metal Defect Repairs ASME Section Ill, NB-4131 states that defects in materials, such as the VHP penetration tube base material, may be eliminated or repaired by welding, provided the defects are removed, repaired, and examined in accordance with the requirements of NB-2500.ASME Section lii, 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 in accordance with NB-2545 or NB-2546.If the removal process reduces the section Exek,n~.Exelon Generation Company, LLC wwwexeloncorp.com N 1 Byron Station 4450 North German Church Road*Byron, IL 61010-9794 10 CFR 50.55a RS-07-055 April 13, 2007 U.S.Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Byron Station Unit 2 Facility Operating License No.NPF-66 NRC Docket No.STN 50-455
Subject:
Byron Station Unit 2 Inservice Inspection Relief Request l3R-14: Alternative Requirements for the Repair of a Reactor Vessel Head Penetration
References:
(1)Westinghouse WCAP-1 5987, Revision 2-A,"Technical Basis for the Embedded Flaw Process for Repair of Reactor Vessel Head Penetrations,"
December 2003 (2)Letter from H.N.Berkow (U.S.NRC)to H.A.Sepp (Westinghouse Electric Company),"Acceptance for Referencing
-Topical Report WCAP-15987-P, Revision 2,'Technical Basis for the Embedded Flaw Process for Repair of Reactor Vessel Head Penetration,'(TAG NO.MB8997),"dated July 3, 2003 In accordance with 10 CFR 50.55a,"Codes and standards,"
paragraph (a)(3)(i), Exelon Generation Company, LLC (EGC)is requesting relief from the American Society of Mechanical Engineers (ASME)Boiler and Pressure Vessel Code,Section XI,"Rules for Inservice Inspection of Nuclear Power Plant Components,"
on the basis that the proposed alternatives would provide an acceptable level of quality and safety.Specifically, a relief request is being proposed to perform an alternative repair technique using the embedding methodology of Reference 1 on the reactor vessel head penetration (VHP)housing and J-groove weld of Byron Station Unit 2 penetration number 68.The embedded flaw methodology to be used has been approved generically by the NRC in the Reference 2 safety evaluation.
The details of this request are contained~n Byron Station Relief Request l3R-14 attached to this letter.During the current Byron Station Unit 2 Spring 2007 Refueling Outage, EGG performed volumetric examinations of the VHPs in accordance with First Revised Order EA-03-009,"Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactor,"(the Order).Ultrasonic examination identified an unacceptable axial indication, confirmed by dye penetrant examination, in VHP 68.
April 13, 2007 U.S.Nuclear Regulatory Commission Page 2 Although a root-cause has not been completed and the damage mechanism has not been confirmed, the repair process conservatively assumes the indication is the result of primary water stress corrosion cracking (PWSCC)and embedding the flaw within PWSCC resistant materials (i.e., Alloy 52 weld metal)will assure structural integrity of the VHP 68 connection.
Supporting the embedded flaw methodology application to the VHP5 for Byron Station Unit 2 is the analysis provided in Westinghouse WCAP-1 6401-P, Revision 0,'Technical Basis for Repair Options for Reactor Vessel Head Penetration Nozzles and Attachment Welds: Byron and Braidwood Units 1 and 2."This WCAP provides the technical basis for the use of an embedded repair involving the VHP housing and/or the VHP housing attachment weld (i.e., the J-groove weld)by evaluating the bounding loading conditions, fatigue crack growth predications, and fracture mechanics results.WCAP-16401-P will be submitted to the NRC in a separate letter, following completion of an affidavit to support withholding of proprietary information.
EGG requests that this repair alternative be verbally approved by April 17, 2007, to support the VHP repair and restoration/restart activities at Byron Station Unit 2.While EGG recognizes the burden associated with an accelerated review and approval of l3R-14, the need for a repair of a VHP at Byron Station Unit 2 as a result of the Order examinations was unexpected.
Byron Station Unit 2 is ranked as a low susceptibility plant with an Effective Degradation Year rating of 2.2 with a very low probability of PWSCC initiation and consequently, there was no expected need to prepare and submit, for NRC review, a contingency Relief Request for an alternative repair methodology in advance of the Byron Station Unit 2 refueling outage.There are no regulatory commitments contained in this submittal.
If you have any questions about this letter, please contact Mr.David Ghrzanowski at (630)657-2816.Respectfully, Darin M.Benyak Director, Licensing and Regulatory Affairs Attachment
-Byron Station Relief Request 13R-14,"Alternative Requirements for the Repair of a Reactor Vessel Head Penetration" Attachment Byron Station Relief Request 13R-14 Alternative Requirements for the Repair of a Reactor Vessel Head Penetration IS!Program Plan Unit 2, Third Interval 10 CFR 50.55a (RELIEF REQUEST 13R-14 Revision 0 Page 1 of 6)Request for Relief Alternative Requirements for the Repair of a Reactor Vessel Head Penetration In Accordance with 10 CFR 50.55a(a)(3)(i) 1.0 ASME CODE COMPONENT AFFECTED Code Class: 1
Reference:
NRC First Revised Order EA-03-009 Identification:
Byron Unit 2 Reactor Vessel Head Penetration (VHP)68
Description:
VHP Housing to Reactor Vessel Head Partial Penetration Weld (J-Groove Weld)Drawing Numbers: 185282E Revision 0, 185283E Revision 1, and 185286E Revision 1 2.0 APPLICABLE CODE EDITION AND ADDENDA American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, 2001 Edition, through 2003 Addenda.3.0 APPLICABLE CODE REQUIREMENT ASME Section Xl, 2001 Edition, through 2003 Addenda, requires repair activities to be conducted in accordance with the requirements of IWA-4000.ASME Section Xl, IWA-441 1 requires that welding, brazing, and installation be performed in accordance with the Owner's Requirements and the original Construction Code of the item.The original Code of Construction for the reactor vessel closure head and VHP housings is ASME Section III, 1971 Edition through Summer 1973 Addenda.ASME Section XI, IWA-4421 (c)states that defect removal or mitigation by welding or brazing be performed in accordance with IWA-441 1.Base Metal Defect Repairs ASME Section Ill, NB-4131 states that defects in materials, such as the VHP penetration tube base material, may be eliminated or repaired by welding, provided the defects are removed, repaired, and examined in accordance with the requirements of NB-2500.ASME Section lii, 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 in accordance with NB-2545 or NB-2546.If the removal process reduces the section