ML112770217

Requests for Relief l4R-51 and l4R-52

ML112770217
Person / Time
Site:	Peach Bottom
Issue date:	01/24/2012
From:	Chernoff H Plant Licensing Branch 1
To:	Pacilio M Exelon Generation Co
Hughey J, NRR/DORL, 301-415-3204
References
TAC ME5392, TAC ME5393, TAC ME5394, TAC ME5395
Download: ML112770217 (18)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 January 24, 2012 Mr. Michael J. Pacilio President and Chief Nuclear Officer Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

PEACH BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3 - REQUESTS FOR RELIEF 14R-51 AND 14R-52 (TAC NOS. ME5392, ME5393, ME5394 AND ME5395)

Dear Mr. Pacilio:

By letters dated January 24, 2011,1 Exelon Generation Company, LLC (EGC or the licensee) submitted Relief Requests 14R-51 and 14R-52 for Peach Bottom Atomic Power Station (PBAPS),

Units 2 and 3. Additionally, in response to Nuclear Regulatory Commission (NRC) requests for additional information, the licensee submitted letters dated March 10,2011, and June 2,2011.2 14R-51 requests relief from reactor vessel circumferential weld examinations, as currently required by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, (ASME Code) Table IWB-2500-1, through the end of the extended license period for PBAPS, Units 2 and 3. 14R-52 requests relief from the ASME Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components." Relief Request 14R-52 proposes an alternative to the requirements contained in Table IWB-2500-1 concerning nozzle-to-vessel weld and nozzle inner radii examinations.

The NRC staff has reviewed EGC's analysis in support of its requests for relief. With respect to Relief Request 14R-51, regarding reactor vessel circumferential shell welds, the NRC staff has concluded that the licensee has demonstrated that the conditional probability of failure of the reactor pressure vessels, with no inspection of the circumferential welds, is bounded through the period of extended operation. This is in accordance with the applicable limiting conditional probability of failure from the NRC staff's final safety evaluation (SE) of BWRVIP-05.3 The NRC staff has concluded that the alternative proposed in 14R-51 provides an acceptable level of quality and safety. Therefore, in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(a}(3}(i), the proposed alternative is authorized for the entire period of extended operation, for PBAPS, Units 2 and 3. In addition, submission of this request by the licensee satisfies Appendix D, Item No. 244 of NUREG-1769, "Safety Evaluation Report Related to the License Renewal of Peach Bottom Atomic Power Station, Units 2 and 3," dated March 2003.5 Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML110250132 and ML110250147, respectively.

2 ADAMS Accession Nos ML110700146 and ML111530244, respectively.

3 ADAMS Legacy Accession No. 9808040037: NRC staff's final SE of topical report, "BWR [boiling water reactor]

Vessel and Internals Project, BWR Reactor Pressure Vessel Shell Weld Inspection Recommendations (BWRVIP-05)," dated July 28.1998.

4 NUREG-1769, Appendix D, Item 24: "Submit RPV [reactor pressure vesselJ circumferential weld examination relief request for 60 years."

5 ADAMS Accession No. ML031010136.

M. Pacilio

-2 With respect to Relief Request 14R-52, regarding nozzle-to-vessel welds and nozzle inner radii, the NRC staff has concluded that the licensee provided adequate information to satisfy the plant-specific applicability requirements from the NRC staffs final SE of the Electric Power Research Institute report, "BWRVIP-108: BWR [boiling water reactor] Vessel and Internals Project, Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Inner Radii," dated December 19,2007,6 which is the technical basis document for ASME Code Case N-702. The NRC staff has concluded that the alternative proposed in 14R-52 provides an acceptable level of quality and safety. Therefore, in accordance with 10 CFR 50.55a(a)(3)(i), the proposed alternative is authorized for the remainder of the fourth Inservice Inspection Interval for PBAPS, Units 2 and 3.

All other requirements of the ASME Code,Section XI not specifically included in the request for the alternatives 14R-51 and 14R-52, submitted by the licensee in letters dated January 24, 2011, as supplemented by letters dated March 10, 2011, and June 2, 2011, remain in effect.

The NRC staffs SE regarding relief requests 14R-51 and 14R-52 is enclosed. If you have any questions, please contact the PBAPS Project Manager, Mr. John Hughey, at 301-415-3204.

Sincerely,

~--...\\~

Meena Khanna, Chief Plant Licensing Branch 1-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-277 and 50-278

Enclosure:

As stated cc w/encr: Distribution via Listserv ADAMS Accession No. ML073600374.

6

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE RELIEF REQUESTS 14R-51 AND 14R-52 EXELON GENERATION COMPANY, LLC PEACH BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3 DOCKET NOS. 50-277 AND 50-278

1.0 INTRODUCTION

By letters dated January 24, 2011,1 Exelon Generation Company, LLC (EGC or the licensee) submitted Relief Requests 14R-51 and 14R-52 for Peach Bottom Atomic Power Station (PBAPS),

Units 2 and 3. Additionally, in response to Nuclear Regulatory Commission (NRC) requests for additional information (RAI), the licensee submitted letters dated March 10, 2011, and June 2, 2011.2 14R-51 requests relief from reactor vessel circumferential weld examinations as currently required by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), Table IWB-2500-1, through the end of the extended license period for PBAPS, Units 2 and 3. 14R-52 requests relief from the ASME Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components." Relief Request 14R-52 proposes an alternative to the requirements contained in Table IWB-2500-1 concerning nozzle-to-vessel weld and nozzle inner radii examinations.

With respect to Relief Request 14R-51, regarding reactor vessel circumferential shell welds, the proposed alternative would eliminate the requirement to inspect the circumferential welds except for the areas of intersection with the axial welds consistent with the guidance provided in Generic Letter 98-05,3 and the NRC staffs safety evaluation (SE) for BWRVIP-05.4 This request satisfies Appendix D, Item No. 245 of NUREG-1769, "Safety Evaluation Report Related to the License Renewal of Peach Bottom Atomic Power Station, Units 2 and 3," dated March 2003.6 For the nozzle-to-vessel welds and nozzle inner radii, the licensee's proposed alternative is based on ASME Code Case N-702, "Alternative Requirements for Boiling Water Reactor (BWR) 1 Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML110250132 and ML110250147, respectively.

2 ADAMS Accession Nos. ML110700146 and ML111530244, respectively.

3 ADAMS Accession No. ML031430368: Generic Letter 98-05, "Boiling Water Reactor Licensee Use of the BWRVIP-05 Report to Request Relief from Augmented Examination Requirements on Reactor Pressure Vessel Circumferential Welds," dated November 10,1998.

4 ADAMS Legacy Accession No. 9808040037: NRC staffs final SE of topical report, "BWR [boiling water reactor]

Vessel and Internals Project, BWR Reactor Pressure Vessel Shell Weld Inspection Recommendations (BWRVIP-05)," dated July 28, 1998.

5 NUREG-1769, Appendix D, Item 24: "Submit RPV [reactor pressure vessel] circumferential weld examination relief request for 60 years."

6 ADAMS Accession No. ML031010136.

Enclosure

- 2 Nozzle Inner Radius and Nozzle-to-Shell Welds." The technical basis for ASME Code Case N 702 was documented in Electric Power Research Institute (EPRI) Technical Report 1003557 for the Boiling Water Reactor Vessel and Internals Project (BWRVIP), "BWR Vessel and Internals Project Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Inner Radius (BWRVIP-1 08),,,7 which was approved by the NRC in an SE dated December 19, 2007.8 This SE specified plant-specific requirements which must be met by applicants proposing to use this alternative. The licensee has provided information in its submittal intended to demonstrate that the relevant PBAPS Reactor Pressure Vessel (RPV) nozzle-to-vessel welds and its inner radii meet these plant-specific requirements so that the proposed alternative can be authorized.

2.0 REGULATORY EVALUATION

Inservice inspection (lSI) of ASME Code, Class 1, 2, and 3 components is performed in accordance with Section XI of the ASME Code and applicable addenda as required by Title 10 of the Code ofFederal Regulations (10 CFR) 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) of 10 CFR states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if: (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.

The regulation in 10 CFR 50.55a(g)(4) further states that ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except design and access provisions and preservice examination requirements, set forth in the ASME Code,Section XI to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that lSI 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) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable lSI Code of Record for the fourth 10-year lSI interval for PBAPS is the 2001 Edition through the 2003 Addenda of ASME Code,Section XI. In addition, for ultrasonic (UT) examinations,Section XI, Appendix VIII, "Performance Demonstration for Ultrasonic Examination Systems," of the 2001 Edition, is implemented as required and modified by 10 CFR SO.SSa(b)(2)(xv).

2.1 RPV Circumferential Welds For RPV circumferential welds, the NRC staffs final SE of topical report BWRVIP-05, dated July 28, 1998,9 concluded that elimination of the lSI of the RPV circumferential welds for BWRs is justified since the failure frequency for circumferential welds in BWR plants is significantly below the criterion specified in Regulatory Guide (RG) 1.154, "Format and Content of Plant SpeCific Pressurized Thermal Shock Safety Analysis Reports for Pressurized Water Reactors,"

dated January 1987.10 The NRC staff notes that RG 1.154 was withdrawn on January 14, 2011, (76 FR 2726) for general application to future licensee relief requests. However, the 7

ADAMS Accession No. ML023330203.

8 ADAMS Accession No. ML073600374.

9 Ibid No.4.

10 ADAMS Accession No. ML031470300.

- 3 acceptability of the use of BWRVIP-OS specifically for Peach Bottom Units 2 and 3 was previously affirmed by the NRC staff evaluation presented in Section 4.2.3.2 of NUREG-1769.

Exelon proposed a future inspection activity to seek relief from the NRC regarding the lSI of the RPV circumferential welds, based on the use of BWRVIP-OS, as part of the Peach Bottom License Renewal Updated Final Safety Analysis Report (UFSAR) Supplement. 11 The NRC staff included the licensee proposed action to seek relief from the inspection requirements for RPV circumferential welds, based on the use of BWRVIP-OS, as Item No. 24 in Appendix D of NUREG-1796. This proposed action (Le., commitment) was elevated to a legal obligation with the inclusion of License Condition 10(b), "Future Inspection Activities," in the Peach Bottom Renewed Operating License, as follows:

The Exelon Generation Company Updated Final Safety Analysis Report supplement submitted pursuant to 10 CFR S4.21 (d), as revised on January 31, 2003, describes certain future inspection activities to be completed before the period of extended operation.

The Exelon Generation Company shall complete these activities no later than August 8, 2013, and shall notify the NRC in writing when implementation of these activities is complete and can be verified by NRC inspection.

Generic Letter 98-0S, "Boiling Water Reactor Licensees use of the BWRVIP-OS Report to Request Relief from Augmented Examination Requirements on Reactor Pressure Vessel Circumferential Shell Welds," dated November 10, 1998,12 provided recommendations for licensee's desiring to request permanent relief from the lSI requirements of 10 CFR SO.SSa(g) for the volumetric examination of circumferential RPV welds (ASME Code Section XI, Table IWB-2S00-1, Examination Category B-A, Item 1.11, Circumferential Shell Welds). The recommendations were based on the NRC staffs final SE of topical report BWRVIP-OS and included the need for licensees to perform their required inspections of "essentially 100 percent" of all axial welds. These recommendations were only applicable to the remaining term of operation under the initial, existing license. Item No. 24 in Appendix D of NUREG-1769, however, noted the NRC staffs expectation that relief would be requested for the extended period of operation.

Neutron fluence projections are needed to support the determination that the conditional failure probability of the welds for which relief is requested remains bounded by the limiting conditional failure probability described in the NRC staffs final SE of topical report BWRVIP-OS. RG 1.190, "Calculational and DOSimetry Methods for Determining Pressure Vessel Neutron Fluence," dated March 2001,13 describes methods and assumptions acceptable to the NRC staff for determining the RPV neutron fluence with respect to the General Design Criteria (GDC) contained in Appendix A to 10 CFR Part SO. PBAPS Units 2 and 3 were designed, built, and began operation prior to the codification of the 10 CFR Appendix A. GDC, and the issuance of NUREG-0800, "Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants:

LWR [light water reactor] Edition." Thus, the GDC are not part of the original design basis of the plant. Appendix H of the Updated Final Safety Analysis Report for PBAPS Units 2 and 3 contain an evaluation of the design basis of the plant as measured against the GDC for Nuclear Power 11 ADAMS Accession No. ML030020273: Exelon Letter dated November 26, 2002, Appendix A, "Updated Final Safety Analysis Report (UFSAR) Supplement," Section A.S.1.1.3.

12 ADAMS Accession No. ML082460066.

13 ADAMS Accession No. ML010890301.

-4 Plant Construction Permits that were proposed to be added to 10 CFR Part 50 as Appendix A in July 1967. The licensee concluded that PBAPS Units 2 and 3 conformed to the intent ofthe Atomic Energy Commission (NRC) proposed GDC.

The NRC staff considered the current GDC 14,30 and 31 as evaluation criteria to establish that the neutron fluence calculation adequately supports the requested relief. In consideration of the guidance set forth in RG 1.190, GDC 14,30, and 31 are applicable. GDC 14, "Reactor Coolant Pressure Boundary," describes the design, fabrication, erection, and testing of the reactor coolant pressure boundary to have an extremely low probability of abnormal leakage, of rapidly propagating failure, and of gross rupture. GDC 30, "Quality of Reactor Coolant Pressure Boundary," describes, among other things, that components comprising the reactor coolant pressure boundary be designed, fabricated, erected, and tested to the highest quality standards practical. GDC 31, "Fracture Prevention of Reactor Coolant Pressure Boundary," pertains to the design of the reactor coolant pressure boundary. GDC 31 addresses the need for the pressure boundary design to incorporate sufficient margin when stressed under operating, maintenance, testing, and postulated accident conditions.

2.2 RPV Nozzle-to-Shell Weld and Inner Radii For all RPV nozzle-to-vessel shell welds and nozzle inner radii, the ASME Code,Section XI requires 100 percent inspection during each 10-year lSI interval. However, ASME Code Case N-702 proposes an alternative which reduces the inspection of RPV nozzle-to-vessel shell welds and nozzle inner radius areas from 100 percent to 25 percent of the nozzles for each nozzle type during each 1 O-year interval.

RG 1.193, "ASME Code Cases Not Approved for Use," Rev. 3 dated October 2010,14 Table 2, "Unacceptable Section XI Code Cases," states that the applicability of Code Case N-702 must be shown by demonstrating that the criteria in Section 5.0 of the NRC Safety Evaluation regarding BWRVIP-108 are met, and that the evaluation demonstrating the applicability of the Code Case shall be reviewed and approved by the NRC prior to the application of the Code Case. In the SE dated December 19, 2007,15 the NRC staff concluded that the BWRVIP-108 report (as supplemented) was acceptable for licensee's to reference as the technical basis for requests for alternatives under 10 CFR 50.55a(a)(3)(i) to implement the provisions of ASME Code Case N-702 on a plant-specific basis, provided that licensees demonstrate that the following criteria established in the BWRVIP-108 SE related to stresses in the nozzles are met:

(Criterion 1)

The maximum RPV heatup/cooldown rate is limited to less than 115 OF/hour For the recirculation inlet nozzles:

(Criterion 2)

(pr/t) / CRPV < 1.15, where:

p = RPV normal operating pressure, psi [pounds per square inch],

r = RPV inner radius, in [inches],

14 ADAMS Accession No. ML101800540.

15 ADAMS Accession No. ML073600374: "Safety Evaluation Of Proprietary EPRI [Electric Power Research Institute]

Report, "BWR Vessel and Internals Project, Technical Basis For The Reduction Of Inspection Requirements For the Boiling Water Reactor Nozzle-To-Vessel Shell Welds And Nozzle Inner Radius (BWRVIP-108)" transmitted via letter from Matthew A. Mitchell to Rick Libra dated December 19, 2007.

- 5 t =RPV wall thickness, in, and CRPV =19332 psi [Le., 1000 psi x 110 in/5.69 in, based on the 8WRVIP-108 recirculation inlet nozzle/RPV finite element method (FEM) model];

(Criterion 3)

[p(ro2 + rj2) I (ro2 - r?)]ICOOZZLE < 1.15, where:

p = RPV normal operating pressure, psi, ro = nozzle outer radius, in, rj =nozzle inner radius, in, and CNOZZlE =1637 psi [i.e., 1000 psi ( 13.9882+ 6.8752) 1(13.9882-6.8752).

[based on the 8WRVIP-108 recirculation inlet nozzle/RPV FEM model];

For the recirculation outlet nozzles:

(Criterion 4)

(pr/t) I CRPV < 1.15, where:

p =RPV normal operating pressure, psi, r =RPV inner radius, in, t =RPV wall thickness, in, and CRPV = 16171 psi [i.e., 1000 psi x 113.2 inch 17.0 inch, based on the 8WRVIP-108 recirculation outlet nozzle/RPV FEM model]; and C

(Criterion 5)

[p(ro2+ rj~ I (ro2 - ri~] I COOZZLE < 115, where:

p =RPV normal operating pressure, psi, ro =nozzle outer radius, in, rj =nozzle inner radius, in, and NOZZLE = 1977 psi [Le., 1000 psi (22.31 2+ 12.782) 1(22.31 2-12.782), based on the 8WRVIP-108 recirculation outlet nozzle I RPV FEM model].

3.0 TECHNICAL EVALUATION

3.1 ASME Code Requirement for which Relief is Requested 3.1.1 RPV Circumferential Welds The ASME Code,Section XI, 2001 Edition Through 2003 Addenda, Table IW8-2500-1, Examination Category B-A, Item B1.11 requires a volumetric examination of all (100%) of the circumferential shell welds each interval.

3.1.2 RPV Nozzle-to-Shell Weld and Inner Radii The ASME Code,Section XI, 2001 Edition Through 2003 Addenda, Table IW8-2500-1, Examination Category 8-0, "Full Penetration Welded Nozzles in Vessels," for Item Number 83.90, "Nozzle-to-Vessel Welds," requires a volumetric examination of all (100%) of the welds each inspection interval. The ASME Code,Section XI, 2001 Edition Through 2003 Addenda, Table IW8-2500-1, for Item Number 83.100, "Nozzle Inside Radius Section," requires a volumetric examination of all (100%) of the nozzle inside radius sections each inspection interval. Examination Category 8-0 includes nozzles with full penetration welds to the vessel shell or head and integrally cast nozzles, but excludes manways and handholes that are either welded to or integrally cast in the vessel.

-8 3.2 Component(s) for which Relief is Requested 3.2.1 RPV Circumferential Welds Code Class:

1 Weld Numbers:

RPV-C1, RPV-C2, RPV-C3, RPV-C4, and RPV-CS Examination Category:

B-A Item Number:

B1.11

==

Description:==

Alternative to ASME Code,Section XI, Table IWB-2S00-1 (for the components described above) 3.2.2 RPV Nozzle-to-Shell Weld and Inner Radii Code Class:

1 Component Numbers:

N2, N3, NS, N8 and N8 Nozzles (detailed list of component identifications is contained in Enclosure 1 of Reference 2)

Examination Category:

B-D (Inspection Program B)

Item Numbers:

B3.90 and B3.100

==

Description:==

Alternative to ASME Code,Section XI, Table IWB-2S00-1 (for the components described above) 3.3 Licensee's Proposed Alternative to the ASME Code and Basis for Alternative 3.3.1 RPV Circumferential Welds 3.3.1.1 Proposed Alternative The proposed alternative is permanent relief from the inservice inspection requirements of 10 CFR SO.SSa(g) for the volumetric examination of circumferential RPV welds (ASME Code,Section XI, Table IWB-2S00-1, Examination Category B-A, Item B1.11, Circumferential Shell Welds) based on the probabilistic risk analysis of BWRVIP-OS combined with the continued implementation of operator procedures and training to limit the frequency of cold overpressure events in accordance with the recommendations of Gl 98-0S. The licensee will continue to perform their required inspections of "essentially 100 percent" of all axial welds.

- 7 3.3.1.2 Basis for Alternative As its technical basis for relief from inspection of the RPV circumferential welds, the licensee submitted information from Section 4.2.3 of NUREG-1769. In the license renewal application and NUREG-1769, relief from the circumferential weld examination was evaluated as a time limited aging analysis (TlAA). In response to an RAI, the licensee provided plant-specific information to demonstrate that the RPV will remain bounded by the assumptions of BWRVIP-05 for the period of extended operation. Specifically, the information that must be submitted per Section 4.2.3.2 of NUREG-1769 is: 1) a comparison of the neutron fluence, initial reference temperature (RTNDT),

chemistry factor, copper and nickel content, delta RTNDT and mean RTNDT of the limiting circumferential weld at the end of the license renewal period, conservatively defined by BWRVI P-74 and BWRVIP-05 as 64 effective full-power years (EFPy); and 2) an estimate of the conditional failure probability of the RPV at the end of the license renewal term based on a comparison of the mean RTNDT for the limiting circumferential weld and the reference case. The mean RTNDT is defined as the sum of the initial RTNDT and the mean value of the adjustment in reference temperature caused by irradiation (ARTNDT); it does not include a margin term (unlike the adjusted reference temperature defined in RG 1.99, "Radiation Embrittlement of Reactor Vessel Materials," Rev. 2, May 1988).

The values of the mean RTNDT for the limiting circumferential weld materials for PBAPS, Units 2 and 3, documented in NUREG-1769, are 12 OF and 17 OF, respectively. Based on the copper and nickel content and neutron fluence values provided by the licensee, the NRC staff confirmed the mean RTNDT values. The mean RTNDT values are bounded by the 64 EFPY mean RTNDT value of 70.6 OF used by the NRC staff for determining the conditional failure probability of circumferential girth weld in an RPV fabricated by Chicago Bridge & Iron (CB&I) (the NRC staff SE of BWRVIP-05 included several different mean RTNDT values for specific RPV fabricators). Since the mean RTNDT values for PBAPS, Units 2 and 3, are less than the 64 EFPY value as addressed in the NRC staff SE, the NRC staff concluded the PBAPS RPV conditional failure probability is also bounded by the NRC analysis.

In an RAI response dated March 10, 2011,16 the licensee provided updated information regarding the neutron fluence and chemistry of the RPV circumferential welds. The updated chemistry values are 0.058 % Cu and 0.949 % Ni for PBAPS, Unit 2 and 0.104 % Cu and 0.938% Ni for PBAPS, Unit 3. The updated neutron fluence values are 1.23 x 1018 n/cm2 (E >

1.0 MeV) for PBAPS, Unit 2 and 9.54 x 1017 n/cm2 (E>1.0 MeV) for PBAPS, Unit 3. Based on the revised neutron fluence and chemistry values, the licensee provided updated mean RTNDT values of 4.4 OF for PBAPS, Unit 2 and 6.8 OF for PBAPS, Unit 3. The licensee stated that the neutron fluence values calculated using the updated methodology are bounded by the values documented in NUREG-1769. However, the licensee indicated the neutron fluence values documented in NUREG-1769 continue to be the current licensing basis for PBAPS, Units 2 and

3.

In the supplement dated March 10, 2011, the licensee indicated the methodology used to calculate the updated neutron fluence values meets RG 1.190, in accordance with the methodology contained in NEDO-32983-A, "Licensing Topical Report: General Electric Methodology for Reactor Pressure Vessel Fast Neutron Flux Evaluations," DRF 0000-0012 4185, Revision 2, dated January 2006.17 16 ADAMS Accession No. ML110700146.

17 ADAMS Accession No. ML072480121. (The licensee's response referenced a proprietary version of this report; the NRC staff references the non-proprietary, open-distribution copy of the same report.)

- 8 In Section 4.2.3 of NUREG-1769, the NRC staff documented that the licensee's procedures and training used to limit cold overpressure events were the same as those previously approved by the NRC staff SE issued June 15, 2000,18 related to the PBAPS request to use the BWRVIP-05 technical alternative for the current license term, submitted by letter dated February 7,2000.19 The licensee stated that the NRC staff concluded in NUREG-1769, Section 4.2.3.3 that the applicant had adequately evaluated the RPV circumferential weld examination relief TLAA, as required by 10 CFR 54.21 (c)(1). The licensee further stated that the NRC staff also concluded that the applicant had provided an adequate description of this TLAA in the Updated Final Safety Analysis Report supplement for the period of extended operation as required by 10 CFR 54.21(d).

3.3.2 RPV Nozzle-to-Shell Weld and Inner Radii 3.3.2.1 Proposed Alternative In accordance with 10 CFR 50.55a(a)(3)(i), the licensee requested relief from performing the required examinations on 100 percent of the nozzle assemblies identified in Tables 5-1 and 5-2 of the licensee's submittal. Table 1 below summarizes the information from the licensee's Tables 5-1 and 5-2. (In Enclosure 1 to their submittal, the licensee provided a detailed list of the nozzles with the component identification numbers, ASME Code,Section XI Category and Item numbers, system, and nominal pipe size). As an alternative for all welds and inner radii identified in Table 1, the licensee proposed to examine a minimum of 25 percent of the PBAPS nozzle-to-vessel welds and inner radius sections, including at least one nozzle from each system and nominal pipe size, in accordance with ASME Code Case N-702. For the nozzle assemblies for which relief is requested, this would mean that examinations would be required for three of the Recirculation Inlet (N2) nozzles and one nozzle from each of the other nozzle groups, as identified in Table 1 below, for each unit.

Table 1 - Minimum Number of Nozzles to be Examined for Each Unit Nozzle Group Nominal Pipe Size (in.)

Nozzles per Group Minimum Number to be Examined Recirculation Inlet (N2) 12 10 3

Main Steam (N3) 26 4

1 Core Spray (N5) 10 2

1 Nozzles on Top Head (N6) 6 2

1 Jet Pump Instrumentation (N8) 4 2

1 18 ADAMS Accession No. ML003724272.

19 ADAMS Accession No. ML003684207.

- 9 ASME Code Case N-702 stipulates that a VT-1 examination may be used in lieu of the volumetric examination for the inner radii required by the ASME Code,Section XI, Table IWB 2500-1, Examination Category B-D, Item No. B3.100, "Nozzle Inside Radius Section." The licensee is only requesting to perform volumetric examinations of the applicable nozzle inner radius sections. The licensee is not requesting use of the VT-1 examination provisions included in the Code Case in lieu of performing volumetric examinations.

3.3.2.2 Basis for Alternative EPRI Technical Report 100355720 provides the basis for ASME Code Case N-702. The evaluation found that failure probabilities at the nozzle blend radius region and nozzle-to-vessel shell weld due to a low temperature overpressure event are very low (Le., <1 x 10-6 for 40 years) with or without inservice inspection. The report concludes that inspection of 25 percent of each nozzle type is technically justified.

EPRI Technical Report 1003557 was approved by the NRC in an SE dated December 19, 2007.

21 Section 5.0, "Plant Specific Applicability," of the SE indicates that each licensee who plans to request relief from ASME Code,Section XI requirements for RPV nozzle to-vessel shell welds and nozzle inner radius sections may reference the BWRVIP-108 report as the technical basis for the use of ASME Code Case N-702 as an alternative. The NRC SE further states that each licensee should demonstrate the plant specific applicability criteria from the BWRVIP-108 report to its facility in the relief request by showing that all the general and nozzle-specific criteria addressed below are satisfied. The licensee provided the results of their evaluation of the five plant-specific applicability criteria (described in Section 2.1 of this SE) as follows:

(Criterion 1)

The maximum RPV heatup/cooldown rate is limited to less than 115 OF/hour PBAPS, Unit 2 and 3 Technical Specification (TS) Surveillance Requirement (SR) 3.4.9.1, associated with TS 3.4.9, "RCS Pressure and Temperature (PIT) Limits,"

provides a reactor coolant system (RCS) heatup/cooldown rate of less than or equal to 100 OF in any 1-hour period. The licensee also stated that the heatup/cooldown rate is also referenced in the PBAPS operating procedures.

For the Recirculation Inlet Nozzles:

(Criterion 2)

(pr/t) I CRPV < 1.1 5 Result for PBAPS Units 2 and 3 = 1.097 < 1.15 (Criterion 3)

[p(rO 2 + ri 2) I (rO 2 - ri 2)] I Cnozzle < 1.15 Result for PBAPS Units 2 and 3 =0.977 < 1.15 For The Recirculation Outlet Nozzles: (not part of relief request)*

(Criterion 4)

(pr/t) I CRPV < 1.15 Result for PBAPS Units 2 and 3 = 1.311 > 1.15 (does not pass)*

20 Ibid No.7.

21 Ibid No.8.

- 10 (Criterion 5)

[p(rO 2 + ri 2) I (rO 2 - ri 2)] I Cnozzle < 1.1 5 Result for PBAPS Units 2 and 3 = 0.853 < 1.15 of the licensee's submittal dated January 24, 2011, provides the calculation of the values presented above, including the plant-specific pressure, dimensions and other parameters. The licensee stated that, based on the above information, all PBAPS RPV nozzle to-vessel shell full penetration welds and nozzle inner radii sections, with the exception of the recirculation outlet nozzles, meet the general and nozzle-specific criteria in BWRVIP-108. The licensee stated that the recirculation outlet nozzles are not included in this relief request, and both nozzles will be examined during the fourth lSI interval. The licensee, therefore, concluded that the use of Code Case N-702 provides an acceptable level of quality and safety in accordance with 10 CFR 50.55a(a)(3)(i) for all the RPV nozzle-to-vessel shell full penetration welds and nozzle inner radii sections, with the exception of the recirculation outlet nozzles.

Additionally, the licensee provided the results of the previous lSI examinations of the nozzles for which relief is being requested in Enclosure 3 of their submittal. All the nozzles for which relief is being requested were inspected at least once with no recordable indications, with the exception of PBAPS, Unit 3, nozzles N2B and N2G, which had recordable indications that were acceptable per ASME Code,Section XI.

3.4 Licensee Proposed Duration of Alternative 3.4.1 RPV Circumferential Welds The licensee requested use of the proposed alternative for the entire period of extended operation (PEO) for both PBAPS units. The PEO for PBAPS, Unit 2 begins August 8, 2013, and ends August 8, 2033. The PEO for PBAPS, Unit 3 begins July 2, 2014, and ends July 2, 2034.

3.4.2 RPV Nozzle-to-Shell Weld and Inner Radii The licensee requested use of the proposed alternative for PBAPS, Units 2 and 3 for the remainder of the fourth 10-year interval of the PBAPS lSI program, which began on November 5, 2008, and will conclude on November 4, 2018.

4.0 STAFF EVALUATION 4.1 RPV Circumferential Welds Section 4.2.3 of NUREG-1769 documents the NRC staff's evaluation of the RPV circumferential weld TLAA. In accordance with the requirements from the NRC staff's SE of BWRVIP-05 for plants to be granted relief from inspection of circumferential welds, the NRC staff concluded that the conditional failure probability of the PBAPS, Units 2 and 3, RPV circumferential welds would be bounded by the limiting conditional probability of failure for RPVs fabricated by CB&I for the duration of the PE~. On this basis, the NRC staff concluded relief from inspection of all circumferential welds was acceptable through the PEO for PBAPS, Units 2 and 3. The NRC staff's conclusion was based on the fact that the mean RTNDT values at 54 EFPY for the limiting circumferential welds for both PBAPS units will be bounded by the 64 EFPY mean RTNDT value of 70.6 OF used by the NRC staff for determining the conditional failure probability of a circumferential girth weld in an RPV fabricated by CB&I.

Exelon proposed a future inspection activity to seek relief from the NRC regarding the lSI of the RPV circumferential welds, based on the use of BWRVIP-05, as part of the Peach Bottom License Renewal Updated Final Safety Analysis Report (UFSAR) Supplement.22 The NRC staff included the licensee proposed action to seek relief from the inspection requirements for RPV circumferential welds, based on the use of BWRVIP-05, as item No. 24 in Appendix 0 of NUREG-1796. This proposed action was elevated to a legal obligation with the inclusion of License Condition 10(b), "Future Inspection Activities," in the Peach Bottom Renewed Operating License.

The current relief request under IR4-51 fulfills Item No. 24 from Appendix 0 of NUREG-1796.

The NRC staff requested 23 that the licensee confirm that the neutron fluence values contained in its submittal letter were calculated in a manner consistent with RG 1.190 or some other acceptable manner. If the fluence values were not calculated using GE report NEDC-32983P, "General Electric Methodology for Reactor Pressure Vessel Fast Neutron Flux Evaluation,"

Revision 2,24 then the licensee was requested to also describe the fluence calculation method that was used and provide information concerning the qualification of the method for use on the BWR/4 vessel geometry in sufficient detail to determine whether the calculations were adherent to RG 1.190 guidance or some other acceptable methodology.

The licensee's response confirmed that the neutron fluence values contained in the current licensing basis, and on which the material evaluations supporting this relief request were based, are conservative. This determination was made using a comparison of the neutron fluence values contained in the submittal to alternative neutron fluence values that were calculated using a method that adheres to RG 1.190 guidance. The confirmatory neutron fluence values were calculated in accordance with the NRC-approved method described in GE licensing topical report NEDC-32983-A, Revision 2. The NRC staff's SE approving NEDC-32983-A (included in the report) provides the NRC staff's evaluation concluding that plant-specific neutron fluence values that are calculated following this methodology would be adherent to the RG 1.190 guidance and hence acceptable. Although the neutron fluence values calculated using this methodology are not considered to be the PBAPS, Units 2 and 3, licensing basis values, the licensee's response stated that the current licensing basis neutron fluence values are higher, and because they are higher, their use is conservative. The NRC staff finds this approach acceptable because of this demonstrated conservatism.

The licensee provided revised copper and nickel values, as well as neutron fluence values in its RAI response dated March 10, 2011. However, the licensee stated that the neutron fluence values documented in NUREG-1769, which are larger and thus bounding, remain the current licensing basis for PBAPS, Units 2 and 3. The NRC staff performed a confirmatory calculation of the mean RTNDT for the limiting circumferential welds for both units using the revised neutron fluence, copper and nickel values provided in the March 10, 2011, supplement and obtained the same results as the licensee. The mean RTNDT for the new values is lower and thus, is still bounded by the limiting value from the NRC staff's SE of 70.6 of. Therefore, the mean RTNDT values based on the updated neutron fluence and chemistry values for PBAPS, Units 2 and 3, confirms that the licensing basis mean RTNDT values are conservative and therefore, remain acceptable. The NRC staff finds that the licensee has demonstrated that the conditional failure probability of the PBAPS, Units 2 and 3, RPV with no circumferential weld examinations will 22 Ibid No. 11.

23 ADAMS Accession No. ML110590063: NRC letter dated February 28, 2011.

24 ADAMS Accession Nos. ML072480116 and ML072480121.

- 12 remain bounded through the end of the PEO. This is in accordance with the limiting conditional failure probability from the NRC staff's final SE of BWRVIP-05 since the mean RTNDT values will remain bounded by the generic mean RTNDT value for an RPV fabricated by CB&1.

Therefore, the NRC staff finds the licensee's alternative to be acceptable for the duration of the PEO.

4.2 RPV Nozzle-to-Shell Weld and Inner Radii 4.2.1 Criteria for Applying the BWRVIP-1 08 Report The December 19,2007, SE regarding the BWRVIP-108 report25 specified five plant-specific criteria that licensees must meet to demonstrate that the BWRVIP-108 report results apply to their plants. The five criteria are related to the driving force of the probabilistic fracture mechanics (PFM) analyses for the recirculation inlet and outlet nozzles. It was stated in the December 19, 2007, SE that the nozzle material fracture toughness-related RTNDT values used in the PFM analyses were based on data from the entire fleet of BWR RPVs. Therefore, the BWRVIP-108 report PFM analyses are bounding with respect to fracture resistance, and only the driving force of the underlying PFM analyses needs to be evaluated. It was also stated in the December 19, 2007, SE that, except for the RPV heatup/cooldown rate, the plant-specific criteria are for the recirculation inlet and outlet nozzles only because the probabilities of failure, for other nozzles are an order of magnitude lower. To evaluate the driving force, the SE required five criteria to be met, which are described in Section 2.2 of this SE.

In its submittal, the licensee provided the results of its evaluation of the five plant-specific applicability criteria established in the December 19, 2007, SE regarding the BWRVIP-108 report. The licensee's evaluation indicated that all the criteria except Criterion 4 for the recirculation outlet nozzles were satisfied. However, Criterion 4 only applies to the recirculation outlet nozzles, which are not included in the request for relief. Further, the recirculation inlet nozzles bound all the other nozzle types evaluated in BWRVIP-108; therefore, BWRVIP-108 can be considered applicable to all the nozzles included in this request for relief and proposed alternative.

The NRC staff independently verified the five criteria as follows:

(Criterion 1)

Maximum RPV heatup/cooldown rate limited to less than 115°F per hour.

The NRC staff verified that the PBAPS, Units 2 and 3, TS SR 3.4.9.1, associated with TS 3.4.9, "RCS Pressure and Temperature (PIT) Limits," provides an RCS heatup/cooldown rate of less than or equal to 100 of in any 1-hour period.

PBAPS specific values from Enclosure 2 of the licensee's submittal dated January 24, 2011, are as follows:

p =RPV normal operating pressure =1035 psi.

r =RPV inner radius =125.5 in.

t =RPV wall thickness =6.125 in.

rO =Recirculation inlet nozzle outer radius =12.5 in.

25 Ibid No. 15.

- 13 ri =Recirculation inlet nozzle inner radius =5.784 in.

rO = Recirculation outlet nozzle outer radius = 26.5 in.

ri = Recirculation outlet nozzle inner radius = 12.97 in.

BWRVIP-108 Constants are as follows:

Crpv (Recirculation Inlet Nozzles) =19332 Cnozzle (Recirculation Inlet Nozzles) = 1637 Crpv (Recirculation Outlet Nozzles) = 16171 Cnozzle (Recirculation Outlet Nozzles) = 1977 For the Recirculation Inlet Nozzles:

(Criterion 2)

(pr/t) I CRPV < 1.1 5

[(1035 x 125.5) 16.125] 119332 = 1.097 < 1.15 pass (Criterion 3)

[p(rO 2 + ri 2) I (rO 2 - ri 2)] I Cnozzle < 1.1 5

[1035 (12.52+5.7842) 1 (12.52-12.7842)]/1637 =0.977 < 1.15 pass For The Recirculation Outlet Nozzles: (not part of relief request)*

(Criterion 4)

(pr/t) 1 CRPV < 1.15

[(1035 x 125.5) 16.125] 116171 = 1.311> 1.15 (does not pass)*

(Criterion 5)

[p(rO 2 + ri 2) 1(rO 2 - ri 2)] 1Cnozzle < 1.15

[1035 (26.52+12.972) 1(26.52-12.972)] 11977 = 0.853 < 1.15 pass Therefore, the NRC staff finds that the licensee has met the plant-specific applicability criteria for BWRVIP-108, except for the recirculation outlet nozzles which are not included in this request for alternative. Therefore, the licensee may apply Code Case N-702 to all the nozzles included in this request for alternative.

4.2.2 Evaluation of the Proposed lSI For all welds and inner radii identified in Table 1, the licensee proposes to examine a minimum of 25 percent of the PBAPS nozzle-to-vessel welds and inner radius sections, including at least one nozzle from each system and nominal pipe size, in accordance with ASME Code Case N 702. For the nozzle assemblies identified in Table 1, this would mean that examinations would be required for three of the recirculation inlet (N2) nozzles and one from each of the other nozzle groups.

The licensee stated they would not use the provision of Code Case N-702 that allows a VT-1 visual examination in lieu of a volumetric examination. Code Case N-702 requires that the volumetric examinations performed on the nozzle inner radii be in accordance with Appendix VIII to the 1989 edition or later of the ASME Code,Section XI. This will ensure the volumetric examinations are of high quality. The NRC staff finds the licensee's continued use of volumetric examination of required nozzle inner radii to be consistent with current regulatory guidance.

- 14 One of the underlying assumptions of ASME Code Case N-702 and BWRVIP-108 is that there is a very low incidence of flaws in the nozzle-to-vessel welds and nozzle inner radii. In Enclosure 3 of the licensee's submittal dated January 24, 2011, the licensee provided a listing of UT examination results for the PBAPS, Units 2 and 3 nozzle-to-vessel and nozzle inner radius examinations that showed recordable indications in only two out of approximately 80 examinations. However, since all the inspection results are from the third interval or later, the NRC staff issued an RAI26 requesting that the applicant clarify if all inspection results for these nozzles for the life of the plant are included in Enclosure 3, and whether the inspections listed were all conducted in accordance with the ASME Code,Section XI, Appendix VIII. In the licensee's response dated June 2,2011,27 the licensee stated that the examinations listed in were only those examinations conducted during the third and fourth inspection intervals for both units. The licensee also provided a revision to the tables of Enclosure 3 including an additional column indicating whether the examination met the requirements of the ASME Code,Section XI. Appendix VIII. Beginning with the second period of the third inspection interval, all the examinations met the requirements of the ASME Code,Section XI, Appendix VIII, representing over 60% of the examinations listed in Enclosure 3. Examinations performed with UT techniques qualified in accordance with the ASME Code,Section XI, Appendix VIII are considered by the NRC staff to be more reliable in terms of probability of detection and sizing accuracy. Only two recordable indications were noted in 54 examinations conducted in accordance with the ASME Code,Section XI, Appendix VIII, both of which were acceptable per ASME Code, Section XL Therefore, the NRC staff finds the previous volumetric examination results conducted, using the best available inspection technology, show a very low incidence of flaws in these welds, consistent with the underlying assumptions of ASME Code Case N-702 and BWRVIP-108. The NRC staff, therefore, considers the RAI to be resolved.

5.0 CONCLUSION

5.1 RPV Circumferential Welds The NRC staff finds the information submitted by the licensee related to the RPV circumferential welds supports the determination that the conditional probability of failure at the end of the PEO is bounded by the limiting conditional probability of failure for a CB&I-fabricated RPV. This finding is based on the projected mean RTNDT of the limiting circumferential weld materials for PBAPS, Units 2 and 3, which is a function of the chemistry and projected neutron fluence for these materials. The projected mean RTNDT values for both PBAPS units are less than the mean RTNDT value associated with the limiting conditional failure probability for a CB&I RPV from the NRC staff's final SE of BWRVIP-05. Additionally, the licensee will continue to implement operator training and procedures to limit the frequency of cold overpressure events to the amount specified in the NRC staffs SE for the BWRVIP-05 report issued on July 28,1998.28 Therefore, the licensee has met the two plant-specific conditions required to obtain relief from inspection of circumferential RPV welds. On this basis, the NRC staff concludes that relief from inspection of RPV circumferential welds and proposed alternative provides an acceptable level of quality and safety.

Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the request for proposed alternative, 14R-51, from the requirements of the ASME Code,Section XI, Table IWB-2500-1 (Inspection Program B),

26 ADAMS Accession No. ML111390152: NRC letter dated May 23, 2011.

27 ADAMS Accession No. ML111530244.

26 Ibid No.4.

- 15 Examination Category B-A, Item B1.11-pertaining to RPV circumferential shell welds, is granted for PBAPS, Units 2 and 3, for the duration of the PEO as defined in Section 3.4.1 of this SE.

All other requirements of the ASME Code,Section XI not specifically included in the request for the alternative 14R-51, submitted by the licensee in letter dated January 24, 2011, as supplemented by letter dated March 10,2011, remain in effect.

5.2 RPV Nozzle-to-Shell Weld and Inner Radii The staff has reviewed the submittal and finds that the PBAPS RPV meets the applicable plant specific criteria specified in the December 19, 2007, SE on the BWRVIP-108 report,29 which provides the technical bases for use of ASME Code Case N-702. Meeting the technical basis for the use of ASME Code Case N-702 ensures that the proposed alternative provides an adequate level of quality and safety.

Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the request for a proposed alternative, 14R-52, from the requirements of the ASME Code,Section XI, Table IWB-2500-1 (Inspection Program B), Examination Category B-D, Items B3.90 and B3.100 pertaining to inspection of the RPV nozzle-to-vessel shell welds and inner radii for the nozzles specified in Enclosure 1 of the licensee's submittal is authorized through the end of the fourth 10-year lSI interval. The number of nozzle-to-vessel welds and nozzle inner radii examined for each nozzle type per interval shall be in accordance with Tables 5-1 and 5-2 of the licensee's submittal.

All other requirements of the ASME Code,Section XI not specifically included in the request for the alternative 14R-52, submitted by the licensee in letter dated January 24, 2011, as supplemented by letter dated June 2, 2011, remain in effect.

Principal Contributors: Jeffrey Poehler Ben Parks Date: January 24, 2012 29 Ibid NO.8.

M. Pacilio

-2 With respect to Relief Request 14R-52, regarding nozzle-to-vessel welds and nozzle inner radii, the NRC staff has concluded that the licensee provided adequate information to satisfy the plant-specific applicability requirements from the NRC staff's final SE of the Electric Power Research Institute report, "BWRVIP-108: BWR [boiling water reactor] Vessel and Internals Project, Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Inner Radii," dated December 19, 2007; which is the technical basis document for ASME Code Case N-702. The NRC staff has concluded that the alternative proposed in 14R-52 provides an acceptable level of quality and safety. Therefore, in accordance with 10 CFR 50.55a(a)(3)(i), the propmed alternative is authorized for the remainder of the fourth Inservice Inspection Intervalfor PBAPS, Units 2 and 3.

All other requirements of the ASME Code,Section XI not specifically included in the request for the alternatives 14R-51 and 14R-52, submitted by the licensee in letters dated January 24, 2011, as supplemented by letters dated March 10, 2011, and June 2, 2011, remain in effect.

The NRC staff's SE regarding relief requests 14R-51 and 14R-52 is enclosed. If you have any questions, please contact the PBAPS Project Manager, Mr. John Hughey, at 301-415-3204.

Sincerely, IRAJ Meena Khanna, Chief Plant Licensing Branch 1-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-277 and 50-278

Enclosure:

As stated cc w/encl: Distribution via Listserv DISTRIBUTION:

PUBLIC RidsOgcRP Resource RidsNrrLAABaxter Resource RidsNRRDor1Lp11-2 Resource RidsNrrPMPeachBottom Resource LPLI-2 RtF RidsAcrsAcnw_MailCTR Resource RidsRgn1 MailCenter Resource RidsNRRDssSrxb Resource RidsNRRDeEvib Resource LChang OEDO, Region 1 d t d ADAMS A ccesslon Nurnber: ML112770217

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TUlses MMitchel MKhanna JHughey DATE 01/24/2012 01/19/2012 01/1712012 08/18/2011 01/24/2012 01/24/2012 OFFICIAL RECORD COpy ADAMS Accession No. ML073600374.

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