ML13290A172

Relief from the Requirements of the ASME Code Request Number 2lSl-011, Rev. 00, Request to Utilize an Alternative to the Requirements of 10 CFR 50.55a(g) for Implementation of a Risk-Informed, Safety-Base

ML13290A172
Person / Time
Site:	Nine Mile Point
Issue date:	10/24/2013
From:	Robert Beall Plant Licensing Branch 1
To:	Costanzo C Nine Mile Point
Vaidya B, NRR/DORL/LPL1-1
References
TAC ME9876
Download: ML13290A172 (19)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. Christopher Costanzo Vice President Nine Mile Point Nine Mile Point Nuclear Station, LLC P. 0. Box 63 Lycoming, NY 13093 October 24, 2013

SUBJECT:

NINE MILE POINT NUCLEAR STATION, UNIT NO.2-RELIEF FROM THE REQUIREMENTS OF THE ASME CODE RE: REQUEST NUMBER RR-21SI-011, REV. 00, REQUEST TO UTILIZE ANAL TERNATIVE TO THE REQUIREMENTS OF 10 CFR 50.55a(g) FOR IMPLEMENTATION OF A RISK-INFORMED, SAFETY-BASED INSERVICE INSPECTION PROGRAM BASED ON ASME CODE CASE N-716 (TAC NO. ME9876)

Dear Mr. Costanzo:

By letter dated October 25, 2012, as supplemented by letter dated September 6, 2013, Nine Mile Point Nuclear Station, LLC (the licensee) submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for the use of alternatives to certain American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (B&PVC) (ASME Code),Section XI requirements at Nine Mile Point Nuclear Station, Unit 2 (NMP2).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (1 0 CFR) 50.55a(a)(3)(i),

the licensee requested to use the proposed alternative on the basis that the alternative provides an acceptable level of quality and safety. The licensee requests an alternative to the requirements of the ASME B&PVC, 2004 Edition, No Addenda, of Section XI, Division 1, Tables IWB-2500-1 and IWC-2500-1, Examination Categories B-F, B-J, C-F-1 and C-F-2.

The NMPNS also requests an alternative to Generic Letter (GL) 88-01 staff positions, as modified by BWRVIP-75-A, on schedule, methods, personnel and sample expansion for Examination Category A welds (resistant materials) only.

The NMPNS also requests authorization to use ASME Code Case N-716, "Alternative Piping Classification and Examination Requirements,Section XI, Division 1,"for risk-informed I safety-based insights.

The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the proposed alternative provides an acceptable level of quality and safety. Therefore, the NRC staff authorizes the proposed alternative in accordance with 10 CFR 50.55a (a)(3)(i) for the remainder of the NMP2 third 1 0-year interval of inservice inspection. The NRC staffs approval of the licensee's risk-informed/safety-based inservice inspection (RIS_B) program does not constitute approval of Code Case N-716.

C. If you have any questions, please contact the Nine Mile Point Nuclear Station Project Manager, Bhalchandra Vaidya, at (301) 415-3308.

Docket Nos. 50-41 0

Enclosure:

As stated cc w/encl: Distribution via Listserv Sincerely, Robert Beall, Chief Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST NO. RR-21SI-011 I REV. 00 REGARDING THE IMPLEMENTATION OF A RISK-INFORMED.

SAFETY-BASED INSERVICE INSPECTION PROGRAM NINE MILE POINT NUCLEAR STATION, LLC NINE MILE POINT NUCLEAR STATION, UNIT 2 DOCKET NOS. 50-410

1.0 INTRODUCTION

By letter dated October 25, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12306A088), as supplemented by letter dated September 6, 2013 (ADAMS Accession No. ML13261A288), Nine Mile Point Nuclear Station, LLC (NMPNS, licensee), requested U.S. Nuclear Regulatory Commission (NRC) authorization to implement a risk-informed inservice inspection (RI-ISI) program plan for Nine Mile Point Nuclear Station, Unit 2 (NMP2) for the third 1 0-year inservice inspection (lSI) interval. The NMP2 proposed the use of the risk-informed I safety-based inservice inspection (RIS_B) process for the lSI of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (B&VPC)

(ASME Code) Class 1 and Class 2 piping, Examination Categories B-F, B-J, C-F-1, and C-F-2 piping welds. The licensee requested implementation of this alternative during the remainder of the third 1 0-year interval.

The licensee requests to implement a RIS_B program based, in part, on ASME Code Case N-716, "Alternative Piping Classification and Examination Requirements,Section XI Division 1" (Reference 1, Code Case N-716). The ASME Code developed the provisions of Code Case N-716 to be used in lieu of the requirements of IWB-2420, IWB-2430, Table IWB-2500-1 (Examination Categories B-F and B-J), IWC-2420, IWC-2430, and Table IWC-2500-1 (Examination Categories C-F-1 and C-F-2) for inservice inspection of Class 1 or 2 piping and IWB-2200 and IWC-2200 for preservice inspection of Class 1 or 2 piping, or as additional requirements for Class 3 piping or Non-Class piping, for plants issued an initial operating license prior to December 31, 2000. The Code Case N-716 requirements are expected to reduce the number of inspections required but may also define additional requirements for Class 3 or non-Class piping.

Code Case N-716 has not been endorsed for generic use by the NRC; however the NRC staff's review of the licensee's application of the Code Case, as described in this safety evaluation, indicates that relief request RR-21SI-011 fully complies with the regulatory requirements and safety goals set forth in NRC Regulatory Guides (RG) for risk-informed inservice inspection programs. The NMP2's relief request refers to the methodology described in Code Case N-716 instead of describing the details of the methodology in the relief request. The NMP2 has, however, modified the methodology described in Code Case N-716 while developing its proposed RIS_8 program. When the methodology used by the licensee is accurately described in Code Case N-716, this safety evaluation (SE) refers to the details found in Code Case N-716.

When the methodology used by the licensee deviates or expands upon the methodology described in Code Case N-716, this SE refers to the licensee's submittals cited above.

2.0 REGULATORY REQUIREMENTS Pursuant to title 10 of the Code of Federal Regulations (1 0 CFR) 50.55a(g), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, "except design and access provisions and preservice examination requirements" set forth in the Code to the extent practical within the limitations of design, geometry, and materials of construction of the components. Paragraph 10 CFR 50.55a(g) also states that lSI 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 addenda, except where specific relief has been granted by the NRC.

The regulations also require, during the first 1 0-year lSI interval and during subsequent intervals, that the licensee's lSI program complies with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference into 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the conditions listed therein. The NMP2 is currently in its third 1 0-year lSI interval which began April 5, 2008. The ASME Section XI code of record for NMP2's third lSI interval is the 2004 Edition with no addenda.

Pursuant to 10 CFR 50.55a(g), a certain percentage of ASME Code Category 8-F, 8-J, C-F-1 and C-F-2 pressure retaining piping welds must receive lSI during each 1 0-year lSI interval. The ASME Code requires 100 percent of all 8-F welds and 25 percent of all 8-J welds greater than 1-inch nominal pipe size be selected for volumetric or surface examination, or both, on the basis of existing stress analyses. For Categories C-F-1 and C-F-2 piping welds, 7.5 percent of non-exempt welds are selected for volumetric or surface examination, or both. According to 10 CFR 50.55a(a)(3), the NRC may authorize alternatives to the requirements of 10 CFR 50.55a(g), if an applicant demonstrates that the proposed alternatives wou1d provide an acceptable level of quality and safety, or that compliance with the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The licensee has proposed to use an RIS_8 program for ASME Code Class 1 and Class 2 piping (Examination Categories 8-F, 8-J, C-F-1 and C-F-2 piping welds), as an alternative to the ASME Code,Section XI requirements on the basis that it provides an acceptable level of quality and safety.

The NRC staff finds that there is regulatory basis for the licensee to request and the NRC to authorize this alternative, pursuant to the technical evaluation that follows. The information provided by the licensee in support of the request has been evaluated by the NRC staff and the bases for disposition are documented below.

3.0 LICENSEE'S PROPOSED ALTERNATIVE 3.1 ASME Code Component Affected The ASME Code components affected by the licensee's proposed alternative are as follows:

System:

Class:

Components Affected:

Various Class 1 and 2 Systems Quality Groups A, and B (ASME Code Class 1, and 2)

All Class 1 and 2 Piping Welds-Examination Categories B-F, B-J, C-F-1, and C-F-2 3.2 ASME Code Requirements Pursuant to 10 CFR 50.55a(g), ASME Code,Section XI, 2004 Edition, No Addenda, Examination Tables IWB-2500-1 and IWC-2500-1, Examination Categories B-F, B-J, C-F-1, C-F-2 must receive inservice inspection during each successive 120-month (ten-year) interval.

The NRC Generic Letter (GL) 88-01 requires lntergranular Stress Corrosion Cracking (IGSCC)

Category A welds to be examined over the 1 0-year interval in accordance with the staff positions on schedule, methods, personnel and sample expansion.

The required examinations in each Examination Category shall be completed during each successive inspection interval in accordance with Inspection Program B, Tables IWB-2412-1 and IWC-2412-1 and GL 88-01 guidelines, as modified by BWRVIP-75-A. Table 1 below reflects these requirements.

Table 1 ASME Section XI and GL 88-01 Examination Requirements ASME Examination Types of Welds Examination Methods Percentage Code Category Requirements Class 1

B-F Dissimilar Metal Volumetric and Surface 1 00% Required Welds or Surface 1

B-J Piping Welds Volumetric and Surface 25% Required or Surface 1

GL-A Resistant Material Volumetric 25% Required 2

C-F-1 Piping Welds Volumetric and Surface 7.5% Required or Surface 2

C-F-2 Piping Welds Volumetric and Surface 7.5% Required or Surface 3.3 Duration of the Alternative Nine Mile Point Nuclear Station, LLC. requested approval of this alternative for the remainder of third ten-year interval of the NMP2 lSI program, which began on April 5, 2008 and is scheduled to end on April 4, 2018.

The NMP2 is currently in the Second Period of the Third 10-Year lSI Interval. The NMPNS plans to complete the current (Third) lSI Interval by implementing a Code Case N-716 based Risk-Informed Safety-Based Program during the Second Inspection Period of the Third Interval.

The NMP2 Third Interval began on April 5, 2008. The Second Inspection Period (of the Third Interval) began on April 5, 2011, and includes the 2012 and 2014 refueling outages (RF013 and RF014). The NMP2 has completed the First Period examinations as defined in the current lSI Program Plan including the approved Code Case N-578 alternatives satisfying ASME Section XI percentage requirements. In anticipation of implementation of the Code Case N-716 RISB program, weld exams have been rescheduled within the current Second lSI Period exam schedule (RF013 and RF014). Upon approval of this RIS_B submittal, NMPNS will remove the exams (moved from RF013 to RF014) from the RF014 schedule to make the Second Inspection Period consistent with the proposed Code Case N-716 RISB exam schedule.

Examinations shall be performed such that the period percentage requirements of ASME Section XI are met for the current Interval.

3.4 Licensee's Proposed Alternative (As stated in the licensee's request)

The licensee's proposed alternative is as follows:

Pursuant to 10 CFR 50.55a(a)(3)(i), NMPNS requests an alternative to the requirements of the ASME B&PVC, 2004 Edition, No Addenda, of Section XI, Division 1, Tables IWB-2500-1 and IWC-2500-1, Examination Categories B-F, B-J, C-F-1 and C-F-2.

The NMPNS also requests an alternative to GL 88-01 staff positions, as modified by BWRVIP-75-A, on schedule, methods, personnel and sample expansion for Examination Category A welds (resistant materials) only.

The NMPNS also requests authorization to use ASME Code Case N-716, "Alternative Piping Classification and Examination Requirements,Section XI, Division 1,"for risk-informed I safety-based insights.

3.5 Licensee's Basis for Alternative (As stated in the licensee's request)

The basis for this request for alternative is to document the application of ASME Code Case N-716 to Class 1 and 2 piping systems at Nine Mile Point Nuclear Station Unit 2 using RISB insights.

The objective of the lSI program is to identify service-induced degradation that might lead to pipe leaks and ruptures, thereby meeting, in part, the requirements set forth in the General Design Criteria and 10 CFR 50.55a. lSI programs are intended to address all piping locations that are subject to degradation. Incorporating risk insights into lSI programs can focus examinations on the more important locations and reduce personnel exposure, while at the same time maintaining or improving the public health and safety.

Electric Power Research Institute (EPRI) Topical Report (TR) EPRI-TR-1 12657, Revision B-A, "Revised Risk-Informed In-service Inspection Evaluation Procedure" (hereafter referred to as EPRI-TR), was submitted for NRC review by letter dated July 29,1999. The NRC review, documented in a safety evaluation dated October 28, 1999, concluded that the EPRI-TR was acceptable for referencing in licensing applications to the extent specified and under the limitations delineated in the EPRI-TR and the associated NRC safety evaluation.

In addition, the NRC staff concluded that the proposed RI-ISI program as described in the EPRI-TR is a sound technical approach and will provide an acceptable level of quality and safety pursuant to 1 0 CFR 50.55a for the proposed alternative to the piping lSI requirements with regard to the number of locations, locations of inspections, and methods of inspection.

The EPRI provided support in the development of this submittal.

As stated within the EPRI-TR, no changes to the augmented inspection programs for Flow Accelerated Corrosion (FAC) or lntergranular Stress Corrosion Cracking (IGSCC) GL 88-01 (as modified by BWRVIP-75-A) Categories B through G welds are being made in the proposed RIS_B inspection program. The proposed RISB program will supersede augmented inspection programs for IGSCC resistant Category A welds.

In addition to development of the proposed risk-informed lSI program utilizing the EPRI methodology, NMPNS will convert from implementing ASME Code Case N-578-1, "Risk-Informed Requirements for Class 1, 2, or 3 Piping, Method B,Section XI, Division 1," to the implementation of ASME Code Case N-716, which was approved by ASME on April19, 2006.

As a result of the above insights, more efficient and technically sound means for selecting and scheduling inservice examinations of piping can be achieved, which will provide an acceptable level of quality and safety as required by 10 CFR 50.55a(a)(3)(i).

4.0 NRC Staff Evaluation of Alternative Code Case N-716 is founded in large part on the RI-ISI process as described in Electric Power Research Institute TR-112657 Revision B-A, "Revised Risk-Informed lnservice Inspection Evaluation Procedure," (Reference 2, EPRI-TR) (ADAMS Accession Number ML013470102) which was previously reviewed and approved by the NRC. The staff has reviewed the development of the proposed RIS_B RI-ISI program using the following documents:

The NUREG-0800, Chapter 3.9.8, Standard Review Plan (SRP) for the Review of Risk-Informed lnservice Inspection of Piping, September 2003 (ADAMS Accession No. ML032510135),

Regulatory Guide 1.17 4, "An Approach for Using Probabilistic Risk Assessment In Risk-Informed Decisions On Plant-Specific Changes to the Licensing Basis' (ADAMS Accession Number ML023240437),

The RG 1.178, "An Approach for Plant-Specific Risk-Informed Decision-making - lnservice Inspection of Piping' (ADAMS Accession Number ML032510128), and The RG 1.200, Revision 1, An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities (ADAMS Accession Number ML070240001 ).

The RG 1.17 4 provides guidance on the use of probabilistic risk assessment (PRA) findings and risk insights in support of licensee requests for changes to a plant's licensing basis. RG 1.178 describes a RI-ISI program as one that incorporates risk insights that can focus inspections on more important locations while at the same time maintaining or improving public health and safety. The RG 1.200 describes one acceptable approach for determining whether the quality of the PRA, in total or the parts that are used to support an application, is sufficient to provide confidence in the results, such that the PRA can be used in regulatory decision-making.

As described above Code Case N-716 is founded, in large part, on the RI-ISI process as described in the EPRI-TR, which was previously reviewed and approved by the NRC. In general, the licensee simplified the EPRI-TR method by using generically identified system parts as high-safety-significant (HSS), and used the plant-specific PRA to evaluate in detail only system parts that could not be screened out as low-safety-significant (LSS).

An acceptable RI-ISI program replaces the number and locations of nondestructive examination (NDE) inspections required by ASME Code,Section XI requirements with the number and locations of these inspections based on the RI-ISI guidelines as described in RG 1.178. The proposed RIS_B program permits alternatives, in accordance with Code Case N-716, to the requirements of IWB-2420, IWB-2430, and IWB-2500 (Examination Categories B-F and B-J) and IWC-2420, IWC-2430, and IWC-2500 (Examination Categories C-F-1 and C-F-2) for inservice inspection of Class 1 and 2 piping and IWB-2200 and IWC-2200 for preservice inspection of Class 1 or 2 piping, or as additional requirements for Subsection IWD, and may require lSI and preservice inspection of Class 3, or Non-Class piping. All piping components, regardless of risk classification, will continue to receive ASME Code-required pressure and leak testing, as part of the current ASME Code,Section XI program.

The EPRI-TR RI-ISI process includes the following steps which, when successfully applied, satisfy the guidance provided in RGs 1.17 4 and 1.178.

Scope definition Consequence evaluation Degradation mechanism evaluation Piping segment definition Risk categorization I nspection/N DE selection Risk impact assessment Implementation monitoring and feedback These processes result in a program consistent with the concept that, by focusing inspections on the most safety-significant welds, the number of inspections can be reduced while at the same time maintaining protection of public health and safety. In general, the methodology in Code Case N-716 replaces a detailed evaluation of the safety significance of each pipe segment with a generic population of high safety-significant segments, followed by a screening flooding analysis to identify any plant-specific high safety-significant segments. The screening flooding analysis is performed in accordance with the flooding PRA approach that is consistent with ASME/ANS RA-Sa-2009, Standard for Levei1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications (Reference 3), as endorsed in RG 1.200. As described below, the acceptability of the licensee's proposed RIS_B program is evaluated by comparing the processes it has applied to develop its program with the steps from the EPRI-TR process.

4.1 Scope Definition The scope of evaluation to support RIS_B program development and of the proposed changes includes ASME Code Class 1, 2, 3 and Non-Class piping welds. The SRP 3.9.8 and RG 1.178 address scope issues. The primary acceptance guideline in the SRP is that the selected scope needs to support the demonstration that any proposed increase in core damage frequency (CDF) and risk are small. The scope of NMP2's evaluation included all Class 1 and 2 piping where ASME inspections could be discontinued, providing assurance that the change-in-risk estimate would, as a minimum, capture the risk increase associated with implementing the RIS_B program in lieu of the ASME program. The RG 1.178 identifies different groupings of plant piping that could be included in a RI-ISI program, and also clarifies that a "full-scope" risk-informed evaluation is acceptable. The scope of the RIS_B program as defined in Code Case N-716 and as evaluated by NMPNS for relief request 21SI-011 is consistent with the definition of full-scope in RG 1.178. Therefore, the NRC staff concludes that the "full-scope" extent of the piping included in the RIS_B program satisfies the guidelines in SRP 3.9.8 and RG 1.178 and is acceptable.

4.2 Consequence Evaluation The methodology described in RG 1.178 and EPRI-TR-112657 divides all piping within the scope of the proposed EPRI RI-ISI program into piping segments. The consequence of each segment failure must be estimated as a conditional core damage probability (CCDP) and conditional large early release probability (CLERP) or by using a set of tables in EPRI-TR-112657 that yield equivalent results. The consequences are used to determine the safety significance of the segments.

In contrast to EPRI-TR-112657 methodology, Code Case N-716 does not require that the consequence of each segment failure be estimated to determine the safety-significance of piping segments. Instead, Code Case N-716 identifies portions of systems that should be generically classified as HSS at all plants. A consequence analysis is not required for system parts generically classified as HSS because there is no higher safety significance category to which the system part can be assigned and degradation mechanisms, not consequence, are used to select inspection locations in the HSS weld population. The licensee's PRA is subsequently used to search for any additional, plant-specific HSS segments that are not included in the generic HSS population.

Sections 2(a)(1) through 2(a)(4) in Code Case N-716 provide guidance that identifies the portions of systems that should be generically classified as HSS based on a review of almost 50 RI-ISI programs. These previous RI-ISI programs were all developed by considering both direct and indirect effects of piping pressure boundary failures and the different failure modes of piping. This is consistent with the guidelines for evaluating pipe failures with PRA described in RG 1.178, the EPRI-TR-112657, and SRP 3.9.8. Therefore, the generic results are derived from acceptable analyses.

Section 2(a)(5) in Code Case N-716 provides guidance that defines additional, plant-specific HSS segments that should be identified using a plant-specific PRA of pressure boundary failures. The licensee stated that it used its PRA of pressure boundary failures (flooding analysis) to identify additional plant-specific HSS segments and that the flooding analysis considered both the direct and indirect effects of pressure boundary failures and the different failure modes of piping. This is consistent with the guidelines for evaluating pipe failures with PRAdescribed in RG 1.178, EPRI-TR-112657, and SRP 3.9.8.

Each of the licensee's consequence evaluations (the generic and the plant-specific flooding analysis) considers both direct and indirect effects of piping pressure boundary failures and the different piping failure modes to systematically use risk insights and PRA results to characterize the consequences of piping failure. This is consistent with the guidelines for evaluating pipe failures with PRA described in RG 1.178 and EPRI-TR-112657 and is, therefore, acceptable.

4.3 Degradation Mechanism Evaluation The EPRI-TR and Code Case differ in the number of pipe segments which are evaluated. The EPRI-TR requires the evaluation of each pipe segment to determine all applicable degradation mechanisms. This is then used to determine the safety significance of the segment.

Alternatively, the Code Case identifies a generic population of piping segments to be assigned to the HSS category without evaluation, followed by a search for plant-specific HSS welds. The Code Case approach is at least as conservative as the EPRI-TR approach because it identifies as high safety significance each piping segment which would have been so identified by the EPRI-TR and because it may identify additional piping segments as being of high safety significance. Based on this conservatism, the NRC finds the use of the degradation mechanism evaluation aspect of the Code Case acceptable.

In lieu of conducting a degradation mechanism evaluation for all the LSS piping, all locations were conservatively assigned to the medium-failure potential for the purpose of assigning a failure frequency to be used to calculate the change in risk. This results in an equal or greater estimated increase in risk from discontinued inspections because the failure frequencies would always be equal to or less than those used in the licensee's analysis if the susceptibility of all LSS welds to all degradation mechanism was determined. The NRC finds this approach of Code Case N-716 and the licensee's alternative acceptable because the assumed degradation mechanism will always result in the assignment of a failure probability at least as high as the complete analysis required by the EPRI-TR methodology.

The relief request and the EPRI-TR differ on the number of pipe segments evaluated for FAC and water hammer. The EPRI-TR states that all pipe segments are to be evaluated for FAC and water hammer as the presence of these degradation mechanisms may affect the failure potential for the piping segment. Code Case N-716 requires evaluation of all piping segments not specified as HSS by the Code Case to determine whether water hammer is present. If water hammer is present in a piping segment then, that segment is assigned a high failure potential in accordance with Table 3 of Code Case N-716 because, as stated above, LSS segments are assumed to have a medium failure potential initially. The staff finds the licensee's use of the Code Case N-716 approach acceptable as it is consistent with the EPRI-TR for those segments considered and it is at least as conservative as the EPRI-TR for those segments not fully evaluated as these segments were assumed to be of high safety significance.

4.4 Piping Segment Definition Previous guidance on risk-informed inservice inspection including RG 1.178 and EPRI-TR-112657 centered on defining and using piping segments. It states in RG 1.178, for example, that the analysis and definition of a piping segment must be consistent and technically sound.

The primary purpose of segments is to group welds so that consequence analyses can be done for the smaller number of segments instead of for each weld. Sections 2(a)(1) to 2(a)(4) in Code Case N-716 identify system parts (segments and groups of segments) that are generically assigned HSS without requiring a plant specific consequence determination and any subdivision of these system parts is unnecessary. Section 2(a)(5) in Code Case N-716 uses a PRAto identify plant specific piping that might be assigned HSS. A flooding PRA consistent with ASME/ANS PRA Standard searches for plant-specific HSS piping by first identifying zones that may be sensitive to flooding, and then evaluating the failure potential of piping in these zones.

Lengths of piping whose failure impacts the same plant equipment within each zone are equivalent to piping segments. Therefore, piping segments are either not needed to reduce the number of consequence analyses required (for the generic HSS piping) or, when needed during the plant specific analysis, the length of pipe included in the analysis is consistent with the definition of a segment in RG 1.178 and SRP 3.9.8.

An additional purpose of piping segments in EPRI-TR-112657 is as an accounting/tracking tool.

In the EPRI methodology, all parts of all systems within the selected scope of the RI-ISI program are placed in segments and the safety significance of each segment is developed. For each safety significant classification, a fixed percentage of welds within all the segments of that class are selected. Additional selection guidelines ensure that this fixed percentage of inspections is distributed throughout the segments to ensure that all damage mechanisms are targeted and all piping systems continue to be inspected. Code Case N-716 generically defines a large population of welds as HSS. An additional population of welds may be added based on the risk-informed search for plant specific HSS segments. When complete, the Code Case N-716 process yields a well-defined population of HSS welds accomplishing the same objective as accounting for each weld throughout the analysis by using segments. Code Case N-716 provides additional guidelines to ensure that this fixed percentage is appropriately distributed throughout the population of welds subject to inspection, all damage mechanisms are targeted, and all piping systems continue to be inspected.

The NRC staff concludes that the segment identification in RG 1.178, as used as an accounting tool, is not needed within the generic population of HSS welds defined in Code Case N-716.

The Code Case N-716 risk-informed search for HSS segments based on a flooding PRA divides up piping systems into segments based on consequences, which is consistent with the segment definition in RG 1.178. Therefore, the licensee's proposed method accomplishes the same objective as the approved methods without requiring that segments be identified and defined for all piping within the scope of the RIS_B program, and accordingly is acceptable to the NRC staff.

4.5 Risk Categorization Sections 2(a)(1) through 2(a)(4) in Code Case N-716 identify the portions of systems that should be generically classified as HSS, and Section 2(a)(5) requires a search for plant-specific HSS segments. Application of the guideline in Section 2(a)(5) in Code Case N-716 identifies plant-specific piping segments that are not assigned to the generic HSS category but that are risk-significant at a particular plant. Code Case N-716 requires that any segment with a total estimated CDF greater than 1 x 1 o-6 per year be assigned to the HSS category. The licensee augmented this Code Case N-716 metric on CDF with the requirement to also assign the HSS category to any segment with a total estimated LERF greater than 1 x 1 o-7 per year. The licensee stated that these guideline values are suitably small and consistent with the decision guidelines for acceptable changes in CDF and LERF found in RG 1.17 4.

In the October 25, 2012 letter, the licensee clarified that these ancillary metrics were added as a defense-in-depth measure to provide a method of ensuring that any plant-specific locations that are important to safety are identified. All piping that has inspections added or removed per Code Case N-716 is required to be included in the change-in-risk assessment and an acceptable change-in-risk estimate is used to demonstrate compliance with the acceptance guidelines in RG 1.17 4. The ancillary metrics and guidelines on CDF and LERF are only used to add HSS segments and not, for example, to remove system parts generically assigned to the HSS in Section 2(a)(1) through 2(a)(4) of Code Case N-716.

The NRC staff concurs that a plant-specific analysis to identify plant-specific locations that are important to safety is a necessary element of RI-ISI program development. The results of the plant-specific risk categorization analysis provide confidence that the goal of inspecting the more risk-significant locations is met while permitting the use of generic HSS system parts to simplify and standardize the evaluation. Satisfying the guidelines in Section 2(a)(5) in N-716 requires confidence that the flooding PRA is capable of successfully identifying all, or most, of the significant flooding contributors to risk that are not included in the generic results. RG 1.200 states that meeting the attributes of an NRC-endorsed industry PRA standard may be used to demonstrate that a PRA is adequate to support a risk-informed application. RG 1.200 further states that an acceptable approach that can be used to ensure technical adequacy is to perform a peer review of the PRA.

In the October 25, 2012 letter, the licensee states that NMP2 PRA is a Level 2, at-power model that includes both internal and external events. The licensee states that a major upgrade of the internal events portion of the model (including internal flooding) was completed in July 2009. A formal BWROG-sponsored industry peer review of the upgraded internal events model was completed in August 2009. Therefore, the guidance of RG 1.200, Revision 1, that a peer review be completed has been satisfied. The peer review reported several findings. The licensee made changes to the PRA model to address most of the findings that would impact the risk-insights.

The NRC staff agrees that resolution of the remaining findings would have a minimal or conservative impact on the risk-insights for this application. The NMP2 reviewed the flooding PRAto identify any piping whose failure could cause flooding that could significantly impact safety significant components but no such piping was identified.

The NRC staff concludes that the CDF and LERF metrics proposed by the licensee are acceptable because they address the risk elements that form the basis for risk-informed applications (i.e., core damage and large early release). The NRC staff accepts the proposed guideline values because these ancillary guidelines are applied in addition to the change-in-risk acceptance guidelines in RG 1.17 4, and only add plant-specific HSS segments to the RIS_B program (i.e., they may not be used to reassign any generic HSS segment into the LSS category).

The NRC staff finds that the risk categorization performed by NMP2 provides confidence that HSS segments have been identified. Sections 2(a)(1) through 2(a)(4) in Code Case N-716, which identify generic HSS portions of systems, were applied to NMP2 piping. The licensee's PRA used to fulfill the guideline in Section 2(a)(5) was performed using a PRA of adequate technical quality based on consistency between the PRA and the applicable characteristics of the NRC-endorsed industry standard.

4.6 lnspection/NDE Selection The licensee's submittals discuss the impact of the proposed RIS_B application on the various augmented inspection programs.

Consistent with the EPRI-TR, Category A welds in the NMP2 augmented inspection program for intergranular stress corrosion cracking (IGSCC) in response to NRC GL 88-01, "NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping," are subsumed into the proposed alternative RIS_B program. The existing NMP2 augmented program for Categories D and E welds in the NMP2 augmented inspection program for IGSCC remains unchanged. The EPRI-TR and Code Case N-716 contain no provisions for changing the FAC augmented program developed in response to NRC GL 89-08, "Erosion/Corrosion-Induced Pipe Wall Thinning." The NMP2's FAC program is relied upon to manage this damage mechanism but is not otherwise affected or changed by the RIS_B program.

The original NMP2 augmented inspection programs for high-energy line breaks in Class 1 and 2 piping were revised in accordance with EPRI-TR-1006937, "Extension of the EPRI Risk Informed lSI Methodology to the Break Exclusion Region Programs," (ADAMS Accession Number ML020950600). The EPRI-TR-1006937 was reviewed and approved by the NRC in a letter dated June 27, 2002 (ADAMS Accession Number ML021790518). The results of the EPRI RI-BER application demonstrated that the volumetric examination requirement for this scope of piping could be reduced from 100 percent to approximately 12 percent. As a result, 12 percent of the BER population will continue to be examined.

The staff finds the licensee's approach to the integration of the proposed RI-ISI program with augmented inspection programs as described above acceptable because it is consistent with the EPRI-TR.

Additionally, Code Case N-716 contains requirements that inspection locations be divided among the systems under consideration and that certain percentages of inspections will be conducted in specific locations. In its relief request the licensee has addressed these issues.

The staff finds this acceptable because the information provided in the relief request is consistent with that required by the EPRI-TR which has been reviewed and approved by the NRC.

The staff reviewed the tables provided in the relief request which address degradation mechanisms, failure potential and the number of welds selected for evaluation. The staff finds that the data contained in these tables is consistent with the requirements of the EPRI-TR and is therefore acceptable.

4.7 Risk Impact Assessment The licensee uses a change-in-risk estimation process approved by the NRC staff in EPRI-TR-112657. The change-in-risk assessment in the EPRI-TR-112657 permits using each segment's CCDP and CLERP or, alternatively, placing each segment into high-, medium-, or low-consequence "bins" and using a single bounding CCDP and CLERP for all segments in each consequence bin. Code Case N-716 also includes both alternatives and the bounding values to be used in the bounding analysis are the same as those approved for use in the EPRI-TR-112657. The licensee uses the alternative of placing each segment into consequence bins and using the associated bounding values for all segments in each bin during the change-in-risk assessment.

In the submittal, the licensee identified different types of pipe failures that cause major plant transients such as those causing loss-of-coolant accidents (LOCAs), isolable LOCAs, and potential LOCAs. Conservative CCDP estimates were developed from the PRA for these initiating events. When the scenario was not appropriately modeled in the PRA, the licensee developed scenarios based on the PRA results and associated plant-specific equipment failures.

The NRC staff concludes that the scenarios described are reasonable because they are modeled in the PRA or include the appropriate equipment failure modes that cause each sequence to progress, and the licensee uses generally accepted values for those failure modes.

Based on these estimates, the segments were assigned into the appropriate consequence bin.

The licensee relied on its flooding analysis to identify the appropriate consequence bin for welds whose failure does not cause a major plant transient and for which a consequence estimate is required. As discussed above, the licensee performed its flooding analysis consistent with ASME/ANS RA-Sa-2009. Only segments with locations at which an inspection is being discontinued or added need to be included in the change-in-risk calculation; therefore, limiting the consequence evaluation to segments that are inspected is acceptable.

Section 5 in Code Case N-716 requires that any piping that has NDE inspections1 added or removed per Code Case N-716 be included in the change-in-risk assessment. The licensee nominally used the upper-bound estimates for CCDP and CLERP. Acceptance criteria provided in Section 5(d) of Code Case N-716 include limits of 1 X 1 o-7 per year and 1 X 1 o-B per year for 1 Code Case N-716 requires no estimated risk increase for discontinuing surface examinations at locations that are not susceptible to outside diameter attack (e.g., external chloride stress-corrosion cracking). The NRC staff determined during the review and approval of EPRI TR-112657 that surface exams do not appreciably contribute to safety and need not be included in the change in risk evaluation and, therefore, exclusion of surface exam from the change in risk evaluations is acceptable.

increase of CDF and LERF for each system, and limits of 1 x 1 o-6 per year and 1 x 1 o-7 per year for the total increase in CDF and LERF associated with replacing the ASME Code Section XI program with the RIS_B program. These guidelines and guideline values are consistent with those approved by the NRC staff in EPRI-TR-112657 and are, therefore, acceptable.

The change-in-risk evaluation approved in EPRI-TR-112657 is a final screening to ensure that a licensee replacing the Section XI program with the risk-informed alternative evaluates the potential change-in-risk resulting from change in method and implements it only upon determining, with reasonable confidence, that any increase in risk is small and acceptable. The licensee's method is consistent with the approved method in EPRI-TR-112657 with the exception that the change-in-risk calculation in Code Case N-716 includes the risk increase from discontinued inspection in LSS segments. For LSS welds, the licensee used CCDP and CLERP values of 1 x 1 o-4 and 1 x 1 o-5, respectively, except for the high pressure core spray (CSH) and reactor core isolation cooling (ICS) systems, where the CCDP for suction piping off the suppression pool had a higher CCDP.

The NMPNS conducted a review and verified that the LSS piping was not susceptible to water hammer. The LSS piping may be susceptible to FAC; however, the susceptibility evaluation and examination for FAC is governed by the FAC program. The RIS_B Program credits and relies upon this plant augmented inspection program to manage this damage mechanism. In lieu of conducting a formal degradation mechanism evaluation for all LSS piping (e.g., to determine if thermal fatigue is applicable), the licensee conservatively assigned these locations to the medium failure potential for use in the change-in-risk assessment.

The NRC staff concludes that the licensee's method described in the submittal is acceptable because the deviation from the approved method in EPRI-TR-112657 expands the scope of the calculated change-in-risk providing confidence that the less detailed analyses of LSS segments required by Code Case N-716 do not result in an unanticipated and potentially unacceptable risk increase.

The licensee provided the results of the change-in-risk calculations in the submittal and noted that results indicate a small and acceptable increase in risk and that all the estimates satisfy both the system level and the total CDF and LERF guidelines. Therefore, the NRC staff finds the change in risk acceptable for this application.

4.8 Implementation Monitoring and Feedback The program implementation process described in the EPRI-TR and RG 1.178 requires that a licensee's RI-ISI program have a schedule for inspecting all piping segments categorized as safety significant. It further states that the inspection interval will normally be that prescribed by Section XI of the Code but that certain degradation mechanisms may require the interval to be altered. The performance monitoring category requires that a licensee's RI-ISI program be updated based on: changes in plant design features, changes in plant procedures, equipment performance changes, examination results, and plant or industry operating experience.

Additionally, a licensee must update its program periodically to correspond to the requirements contained in Section XI of the Code, Inspection Program B. The corrective action category requires a corrective action program that is consistent with the requirements of Section XI of the Code for both Code class and non-Code class piping.

Information concerning this topic was obtained from the relief request itself and from Sections 6 and 7 of the Code Case. The Code Case information was used by the NRC in this review based on the licensee's statement that it would develop implementation procedures for its program in accordance with the Code Case. In its relief request the licensee states that it has a corrective action program and that it will review the RI-ISI program periodically as required by the Code or more frequently as directed by the NRC, or industry or plant specific feedback. Sections 6 and 7 of the Code Case address inspection frequency and program updates. These sections indicate that inspection frequencies should normally be in accordance with Code requirements and that updates should be made on a Code dictated schedule or more frequently in response to plant and industry events or information.

In the September 6, 2013, submittal the licensee stated that it had scheduled the examination of six additional welds based on operating experience (OE) of leakage at another plant and the fact that these welds had similar attributes. They also stated that the program will require reviews of pertinent OE and vendor communications.

The NRC finds the licensee's approach to implementing the program to be acceptable because, in accordance with RG 1.178, the licensee indicated that it inspects components on a frequency based on the Code, that it has a corrective action program, and that it updates the program periodically and in response to plant and industry events and information.

4.9 Examination Methods Section 4 of the EPRI-TR addresses the NDE techniques which must be used in a RI-ISI program. This section emphasizes the concept that the inspection technique utilized must be specific to the degradation mechanism expected. Table 4.1 of the EPRI-TR summarizes the degradation mechanisms expected and the examination methods which are appropriate.

Specific references are provided to the Code concerning the manner in which the examination is conducted and the acceptance standard.

The Code Case addresses the issue of degradation mechanism/inspection technique in Table 1.

Like Table 4.1 of the EPRI-TR, Table 1 of the Code Case lists degradation mechanism and corresponding inspection techniques. This table also provides references to the Code concerning the manner in which the examination is conduced and the acceptance standard.

In its relief request, the licensee states that the implementation of the RI-ISI program will conform to the Code Case, i.e., each HSS piping segment will be assigned to the appropriate item number within Table 1 of the Code Case. The staff finds this acceptable because proper assignment of piping segments into Table 1 will ensure that appropriate inspections to detect the degradation mechanism under consideration are conducted. The NRC finds this approach acceptable because it is consistent with the EPRI-TR which has been reviewed and approved by the NRC and the Code Case includes additional code item numbers to assign NDE requirements to all HSS locations including those segments where no degradation mechanism has been identified.

Pursuant to 10 CFR 50.55a(a)(3)(i), alternatives to the requirements of 10 CFR 50.55a(g) may be used, when authorized by the NRC, if the licensee demonstrates that the proposed alternatives will provide an acceptable level of quality and safety. In this case, the licensee has proposed to use an alternative to the risk-informed process described in NRC-approved EPRI-TR-112657.

The implementation strategy is consistent with the RG 1.178 guidelines because the number and location of inspections is a product of a systematic application of the risk-informed process.

Other aspects of the licensee's lSI program, such as system pressure tests and visual examination of piping structural elements will continue to be performed on all Class 1, 2, and 3 systems in accordance with ASME Code,Section XI. This provides a measure of continued monitoring of areas that are being eliminated from the NDE portion of the lSI program. As required by EPRI-TR-112657 methodology, the existing ASME Code performance measurement strategies will remain in place. In addition, the Code Case N-716 methodology provides for increased inspection volumes for those locations that are included in the NDE portion of the program.

The RG 1.17 4 establishes requirements for risk-informed decisions involving a change to a plant's licensing basis. The RG 1.178 establishes requirements for risk-informed decisions involving alternatives to the lSI program requirements of 10 CFR 50.55a(g), and its directive to follow the requirements of the ASME Code,Section XI. The EPRI-TR-112657 RI-ISI methodology contains details for developing an acceptable RI-ISI program. The Code Case N-716, modified as described by the licensee in its submittal, describes a methodology similar to EPRI-TR-112657 methodology but with differences as described in this SER. The NRC staff has evaluated each of the differences and determined that the licensee's proposed methodology, when applied as described, meets the intent of all the steps endorsed in EPRI-TR-112657, is consistent with the guidance provided in RG 1.178, and therefore satisfies the guidelines established in RG 1.17 4.

5.0 CONCLUSION

Based on the discussion above, the NRC staff concludes that the alternatives proposed in RR-21SI-011, Rev. 00 will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes RR-21SI-011, Rev. 00. This relief request is authorized for use during the fourth 1 0-year lSI interval for NMP1 which began on April 5, 2008, and is scheduled to end on April 4, 2018.

All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third party review by the Authorized Nuclear lnservice Inspector.

As set forth above, the NRC staff determines that the proposed alternative provides an acceptable level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a, and is in compliance with the ASME Code's requirements. Therefore, the NRC staff authorizes the use of the proposed RI-ISI RIS_B program as described in Relief Request 21SI-011 at Nine Mile Point Nuclear Power Station, Unit 2 for the remainder of the third 1 0-year lSI interval. All other ASME Code,Section XI requirements for which relief was not specifically requested and approved remain applicable, including third-party review by Authorized Nuclear lnservice Inspector.

6.0 REFERENCES

1. ASME Code Case N-716, Alternative Piping Classification and Examination equirements,Section XI Division 1, © ASME, New York, New York, April 19, 2006.

2. EPRI-TR-112657, Revision 8-A, Revised Risk-Informed lnservice Inspection Evaluation Procedure, December 1999 (ADAMS Accession No. ML013470102).

3. ASME/ANS RA-Sa-2009, Addenda to ASME/ANS RA-S-2008, Standard for Levei1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications, ASME, New York, NY, February 2, 2009 Principal Contributors: K. Hoffman M. Reisi Fard Date: October 24, 2013

C. A Costanzo If you have any questions, please contact the Nine Mile Point Nuclear Station Project Manager, Bhalchandra Vaidya, at (301) 415-3308.

Docket Nos. 50-410

Enclosure:

As stated Sincerely, Ira/

Robert Beall, Chief Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation cc w/encl: Distribution via Listserv DISTRIBUTION:

PUBLIC RidsNrrPMNineMilePoint RidsNrrDoriDpr MReisi-Fard, NRR/APLA LPL 1-1 Reading File RidsNrrLKGoldstein RidsRgn1 Mail Center S. Dinsmore, NRR/APLA RidsNrrDorllpl1-1 RidsAcrsAcnw_MaiiCTR KHoffman, NRR/EPNB ADAMS ACCESSION NO ML13290A172 (*) N S b t

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