ML100700034

Request for Alternative 1ISI-003, Request to Use ASME Code Case N-716 Associated with the Fourth 10-year Inservice Inspection Interval

ML100700034
Person / Time
Site:	Nine Mile Point
Issue date:	03/15/2010
From:	Richard Guzman, Nancy Salgado Plant Licensing Branch 1
To:	Belcher S Nine Mile Point
Guzman R, NRR/DORL, 415-1030
References
TAC ME0993
Download: ML100700034 (14)

Text

\.~p.1\ REG U/ _ UNITED STATES

.;:;c, "'I~

~ 0." NUCLEAR REGULATORY COMMISSION

~~ ~ WASHINGTON, D.C. 20555-0001

<{

~

~ ~

0 March 15,2010

~ ~

~I) ...0

• • • • -i' Mr. Samuel L. Belcher Vice President Nine Mile Point Nine Mile Point Nuclear Station, LLC P.O. Box 63 Lycoming, NY 13093

SUBJECT:

NINE MILE POINT NUCLEAR STATION, UNIT NO.1 - REQUEST FOR ALTERNATIVE '1ISI-003, REQUEST TO USE ASME CODE CASE N-716 ASSOCIATED WITH THE FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL (TAC NO. ME0993)

Dear Mr. Belcher:

By letter dated March 16, 2009, as supplemented by letters dated October 2, 2009 and January 28,2010, Nine Mile Point Nuclear Station, LLC (NMPNS, the licensee), submitted Relief Request (RR) 11SI-003 pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(a)(3)(i) for Nine Mile Point, Unit NO.1 (NMP1). The request for relief would implement a risk-informed, safety based (RIS_B) inservice inspection (lSI) program for piping at NMP1.

The proposed program is based, in part, on the American Society of Mechanical Engineering Boiler and Pressure Vessel Code,Section XI, Code Case N-716.

The Nuclear Regulatory Commission (NRC) staff has reviewed the subject request, and concludes 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 licensee's fourth 10-year lSI interval. The NRC staff's approval of the licensee's RIS_B program does not constitute approval of Code Case N-716. The results of the NRC staff's review are provided in the enclosed safety evaluation.

If you have any questions regarding this approval, please contact Richard Guzman, at 301-415 1030 or Richard.Guzman@nrc.gov.

Sincerely,

~~~

Nancy L. Salgado, Chief Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-220

Enclosure:

As stated cc w/encl: Distribution via Listserv

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ALTERNATIVE REQUEST 11SI-003 FOR THE USE OF A RISK-INFORMED, SAFETY BASED INSERVICE INSPECTION PROGRAM NINE MILE POINT NUCLEAR STATION, LLC NINE MILE POINT NUCLEAR STATION, UNIT NO.1 DOCKET NO. 50-220

1.0 INTRODUCTION

By letter dated March 16, 2009, Agencywide Documents Access and Management System (ADAMS) Accession No. ML090860860), as supplemented by letters dated October 2,2009 (ADAMS Accession No. ML092790156), and January 28, 2010 (ADAMS Accession No. ML100320052), Nine Mile Point Nuclear Station, LLC (NMPNS, the licensee), submitted a relief request to the Nuclear Regulatory Commission (NRC), proposing a risk-informed/safety-based inservice inspection (RIS_B) program plan for Nine Mile Point Nuclear Station, Unit NO.1 (NMP1) for the fourth 1O-year inservice inspection (lSI) interval. NMP1 proposed the use of the RIS_B process for the lSI of American Society of Mechanical Engineers Boiler and Pressure Vessel Code (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 fourth 10-year lSI interval.

NMP1 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" (N-716).

The provisions of N-716 may 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 lSI 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 N-716 requirements are expected to reduce the number of inspections required but may also define additional requirements for Class 3 piping or non-Class piping.

N-716 has not been endorsed for generic use by the NRC. NMPNS's relief request refers to the methodology described in N-716 instead of describing the details of the methodology in the relief request. NMPNS has, however, modified the methodology described in N-716 while developing its proposed RIS_B program. When the methodology used by the licensee is accurately described in N-716, this safety evaluation (SE) refers to the details found in N-716.

When the methodology used by the licensee deviates or expands upon the methodology described in N-716, this SE refers to the licensee's submittals cited above. Therefore, N-716 is incorporated in this SE only as a source for some of the detailed methodology descriptions as needed, and the NRC staff is not endorsing the generic use of Code Case N-716.

-2

2.0 REGULATORY EVALUATION

Pursuant to Title 10 of the Code of Federal Regulations (10 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 objective of the lSI program, as described in Section XI of the ASME Code and applicable addenda, is to identify conditions (Le., flaw indications) that are precursors to leaks and ruptures in the pressure boundary of these components that may impact plant safety.

The regulations also require, during the first 10-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 limitations and modifications listed therein. NMP1 is in its fourth 10-year lSI interval which started on August 23,2009.

Pursuant to 10 CFR 50.55a(g), a certain percentage of ASME Code Category B-F, B-J, C-F-1, and C-F-2 pressure retaining piping welds must receive lSI during each 10-year lSI interval.

The ASME Code requires 100 percent of all B-F welds and 25 percent of all B-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 would 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_B program for ASME Code Class 1 and Class 2 piping (Examination Categories B-F, B-J, C-F-1, and C-F-2 piping welds), as an alternative to the ASME Code,Section XI requirements. As stated in Section 1.0 of this SE, the provisions of N-716 are expected to reduce the number of required examinations, but may also define additional requirements for Class 3 piping or non-Class piping. The application states that this proposed program will be substituted for the current program in accordance with 10 CFR 50.55a(a)(3)(i) by alternatively providing an acceptable level of quality and safety.

The licensee states that N-716 is founded in large part on the risk-informed inservice inspection (RI-ISI) process as described in Electric Power Research Institute (EPRI) TR-112657 Revision B-A, "Revised Risk-Informed Inservice Inspection Evaluation Procedure," (EPRI-TR) (ADAMS Accession No. ML013470102) which was previously reviewed and approved by the NRC. The NRC staff reviewed the development of the proposed RIS_B proposed RI-ISI program using the following documents.

Regulatory Guide (RG) 1.174, "An Approach for Using Probabilistic Risk Assessment In Risk-Informed Decisions On Plant-Specific Changes to the Licensing Basis," (ADAMS Accession No. ML023240437),

-3 RG 1.178, "An Approach For Plant-Specific Risk-Informed Decisionmaking - Inservice Inspection of Piping," (ADAMS Accession No. ML032510128), and RG 1.200, Revision 1, "An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities," (ADAMS Accession No. ML032510128).

RG 1.174 provides gUidance on the use of probabilistic risk analysis (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. 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.

3.0 TECHNICAL EVALUATION

In general, the licensee simplified the EPRI-TR method because it does not evaluate system parts that have been generically identified as high-safety-significant (HSS), and uses the plant specific flooding PRA to evaluate in detail only system parts that cannot be screened out as low safety-significant (LSS).

An acceptable RI-ISI program replaces the number and locations of nondestructive examination (NDE) inspections based on ASME Code,Section XI requirements with the number and locations of these inspections based on the RI-ISI guidelines. The proposed RIS_B program permits alternatives 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), or as additional requirements for Subsection IWD, and may be used for lSI and preservice inspection of Class 1, 2, 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 1.174 and 1.178.

Scope definition Consequence evaluation Degradation mechanism evaluation Piping segment definition Risk categorization Inspection/NDE 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 N-716 replaces a detailed evaluation of the safety significance of each pipe segment with a generic population of HSS segments, followed by a screening flooding analysis to identify any

-4 plant-specific HSS segments. The screening flooding analysis is performed in accordance with the flooding analysis described in Section 4.5.7 of ASME RA-Sb-2005, "Standard for Probabilistic Risk Assessment for Nuclear Power Plant Applications, Addendum B to ASME RA S-2002," (ASME RA-Sb-2005) dated December 30, 2005.

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.

3.1 Scope Definition The scope of the risk evaluation to support RIS_B program development includes ASME Code Class 1, 2, 3 and Non-Class piping welds. RG 1.178 addresses scope issues. The primary acceptance guideline in the RG 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 NMP1's evaluation included all 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. RG 1.178 identifies different groupings of plant piping that should 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 N-716 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 changes satisfies the RG guidelines and is acceptable.

3.2 Consequence Evaluation The methodology described in RG 1.178 and the EPRI-TR divide 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 the EPRI-TR that yield equivalent results. The consequences are used to determine the safety significance of the segments.

In contrast to the EPRI-TR methodology, N-716 does not require that the consequence of each segment failure be estimated to determine the safety-significance of piping segments. Instead, 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 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

-5 1.178 and the EPRI-TR, and, therefore, the generic results are derived from acceptable analyses.

Section 2(a)(5) in N-716 provides guidance that defines additional, plant-specific HSS segments that should be identified using a plant-specific PRA of pressure boundary failures. In its letter dated March 16, 2009, the licensee stated that its PRA has been updated and meets capability category II supporting requirements in ASME RA-Sb-2005 including consideration of NRC staff positions provided in Appendix A of RG 1.200, Revision 1. Capability category II of supporting requirement IF-C3 in ASME RA-Sb-2005 (as modified by RG 1.200) is met when the flooding analysis includes SSC failure from submergence and spray effects, and qualitatively and conservatively assess the impact of other indirect effects of pressure boundary failure. This is consistent with the guidelines for evaluating the consequences of pipe failures with PRA described in RG 1.178 and the EPRI-TR.

Therefore, 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 is, therefore, acceptable.

3.3 Degradation Mechanism Evaluation The EPRI-TR requires a determination of the susceptibility to all degradation mechanisms of every weld within the scope of the proposed program. The degradation mechanisms which should be identified are described in the EPRI-TR. This information is used to support the safety significance determination for all segments, to target inspections toward the locations with damage mechanisms in the segments that require inspections, and to provide estimates of weld failure frequencies to support the change in risk calculation. Once a segment is placed in the LSS category, the degradation mechanisms at the welds in that segment are not further used in the development of an EPRI RI-ISI program because inspections are not required in LSS segments.

N-716 identifies a generic population of HSS welds, followed by a search for plant-specific HSS welds. N-716 requires a determination of the susceptibility to all degradation mechanisms of all welds assigned to the HSS category. The degradation mechanisms to be considered in N-716 are consistent with those identified in the EPRI-TR report which the staff has previously concluded is a sufficiently comprehensive list of the applicable mechanisms.

The licensee stated that a review was conducted to verify that LSS piping was not susceptible to flow accelerated corrosion or water hammer, the two degradation mechanisms that would assign a high-failure frequency to a weld. 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.

-6 NRC staff concludes that the bounding analysis for specific welds where inspections will be added or discontinued is acceptable because the process fulfills the requirements for identifying locations that should be inspected (i.e., identifying plant-specific HSS segments) and develops a bounding estimate for the change in risk.

3.4 Piping Segment Definition Previous guidance on RI-ISI including RG 1.178 and the EPRI-TR centered on defining and using piping segments. RG 1.178 states, 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 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 N-716 uses a PRA to identify plant-specific piping that might be assigned HSS. A flooding PRA consistent with ASME RA-Sb-2005 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.

An additional purpose of piping segments in the EPRI-TR 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. 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 N-716 process yields a well-defined population of HSS welds from which inspections must be selected accomplishing the same objective as accounting for each weld throughout the analysis by using segments. The code case provides additional guidelines to ensure that this fixed percentage is appropriately distributed throughout the population of welds subject to inspected, 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. A flooding PRA consistent with ASME RA-Sb-2005 utilizes lengths of piping consistent with the segment definition in RG 1.178 whenever a consequence evaluation is needed. Therefore, the 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.

-7 3.5 Risk Categorization Sections 2(a)(1) through 2(a)(4) in 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 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. N-716 requires that any segment with a total estimated CDF greater than 1E-6/year be assigned the HSS category. The licensee augmented this N-716 metric on CDF with the requirement to also assign the HSS category to any segment with a total estimated large early release frequency (LERF) greater than 1E-7/year.

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 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 RG 1.174's acceptance guidelines. 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 Sections 2(a)(1) through 2(a)(4).

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. Any evaluation that categorizes the safety significance of structures, systems, and components requires metrics and guideline values, such as the Fussel-Vessley and risk achievement worth guidelines endorsed in RG 1.201, "Guidelines for Categorizing Structures, Systems, and Components in Nuclear Power Plants According to Their Safety Significance," (ADAMS Accession No. ML061090666). Such metrics are subordinate to the change in risk metrics in RG 1.174 which are used to determine whether the increase in risk associated with a proposed change is small and consistent with the intent of the Commission's Safety Goal Policy Statement.

Satisfying the guidelines in Sections 2(a)(5) 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 compliance with the attributes of an NRC-endorsed industry PRA standard (currently ASME RA-Sb-2005) may be used to demonstrate that a PRA analysis 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. As discussed in Section 3.7 of this SE, the NRC staff concludes that NMP1 has adequately demonstrated that its PRA is technically adequate to support development of the RI-ISI program consistent with the guidelines in RG 1.200.

The NRC staff concurs 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 (Le., 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 1.174, and only add plant-specific HSS segments to the RIS_B

- 8 program, Le., they may not be used to reassign any generic HSS segment into the LSS category.

The NRC staff finds that the risk categorization performed at NMP1 provides confidence that HSS segments have been identified. Sections 2(a)(1) through 2(a)(4) in N-716 which identify generic HSS portions of systems were applied to NMP1 piping. The licensee's PRA analysis used to fulfill the guideline in Sections 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 ASME RA-Sb-2005. The licensee reviewed the results of its flooding analysis and did not identify any segments that had a CDF greater than 1E-6/year or a LERF greater than 1E-7/year.

3.6 Inspection/NDE Selection The licensee's submittal and supplemental letters 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 augmented inspection program for intergranular stress-corrosion cracking (IGSCC) in response to NRC Generic Letter (GL) 88-01, "NRC Position on IGSCC in [Boiling-Water Reactor] BWR Austenitic Stainless Steel Piping," are subsumed into the proposed alternative RIS-B program. The existing augmented program for Categories B through G welds remains unchanged.

N-716 contains no provisions for changing the FAC augmented program developed in response to NRC GL 89-08, "Erosion/Corrosion-Induced Pipe Wall Thinning." NMP1 's FAC program is relied upon to manage this damage mechanism but is not otherwise affected or changed by the RIS_B program.

N-716 contains no provisions for reducing the number of inspections in the inspection program for break exclusion region (BER). However, N-716 does include a provision to increase the number of BER inspections if the BER program is inspecting less than 10 percent of the welds in this region. Changes to the BER program may be made as authorized by EPRI TR-1006937, "Extension of the EPRI Risk Informed lSI Methodology to the Break Exclusion Region Programs," (ADAMS Accession No. ML021790518) or by another process found acceptable by the NRC staff.

Section 4 in N-716 requires that 10 percent of HSS welds shall be selected for examination including, at a minimum, 10 percent of all Class 1 welds. Sections 4(b)(1) through 4(b)(3) in N-716 describe how the inspection locations will be selected. The selection process includes guidance that ensures that inspection locations are distributed physically throughout the HSS piping systems and that all degradation mechanisms will be represented in the selected locations. The guidance provides some flexibility in the distribution of locations to satisfy all the guidelines but the number of inspections must be increased beyond 10 percent, if necessary, to meet the quantitative risk acceptance guidelines in Section 5(b).

In contrast to the EPRI TR which only changed the types of lSI inspections and the locations of inspections, N-716 also discontinues preservice inspection requirements for LSS welds. These preservice examinations are performed to obtain a baseline inspection using the examination

- 9 method that will be used for subsequent lSI examinations. Similar to the ASME Code which requires preservice examination of all Class 1 welds, N-716 requires preservice examination of all HSS welds. Preservice examinations are performed on ASME Code Class 2 welds that are initially selected for lSI, which is 7.5 percent of Class 2 piping welds. Any Class 2, Class 3, or non-code welds that are selected for inspection in the RIS_B program will be HSS welds.

Therefore, preservice examinations will continue to be performed on all welds selected for examination using N-716 to obtain a baseline inspection using the examination method that will be used for subsequent lSI examinations.

In addition to the preservice exams as required, repair/replacement activities involving welding or brazing areas and welded joints made for installation of items shall be examined in accordance with the Construction Code identified in the licensee's Repair/Replacement Plan.

The licensee's use of N-716 does not affect the examinations required to verify the integrity of welds associated with repair/replacement activities. Therefore, the NRC staff finds that there is no effect on the change in risk calculations associated with repair activities under the RIS_B program because the examinations required to verify the integrity of repaired or replaced welds are not affected and will continue to be performed.

3.7 Risk Impact Assessment Section 5 in Code Case N-716 requires that any piping locations that have NDE inspections 1 added or removed per Code Case N-716, be included in the change in risk assessment.

Acceptance criteria provided in Section 5(d) in N-716 include limits of 1E-7/year and 1E-8/year for increase in CDF and LERF for each system, and limits of 1E-6/year and 1E-7/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 the guideline values in the EPRI-TR.

The change in risk assessment (and the risk categorization in Section 3.5 of this SE) should be performed using a technically adequate PRA. In its letter dated March 16, 2009, the licensee stated that its PRA has been updated (completed in January 2008 according to an earlier NMPNS letter dated December 4, 2008 (ADAMS Accession No. ML083440059)) and that a peer review was conducted in February 2008. The peer review utilized the process described in the Nuclear Energy Institute's (NEI) document NEI-05-04, "Process for Performing Follow-on PRA Peer Reviews Using the ASME PRA Standard," (ADAMS Accession No. ML073551159).

All the peer review findings were also provided in the December 4,2008, letter. Peer review findings identify possible differences between the methods and analyses used in NMP1 's PRA and the methods and analyses describing a capability category II PRA.

The NRC staff provided regulatory positions on NEI-05-04 in Table B-5 of RG 1.200. The first of the two NRC staff qualifications regarding the methodology in NEI-04-05 was that the NRC staff does not agree with the assigned overall PRA grades (capability categories) for the risk informed applications listed in Section 3.2 of NEI 05-04. The licensee stated that the risk impact 1Code 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 the EPRI-TR that the surface exams do not appreciably contribute to safety and need not be included in the change in risk quantification. Therefore, the NRC staff finds that the exclusion of surface examinations from the change in risk evaluations is acceptable.

- 10 assessment performed for the RIS_B program application was based on the final post-peer reviewed PRA update which incorporated the resolution of all the previous peer review findings.

In its letters dated October 2, 2009, and January 28, 2010, the licensee clarified that several supporting requirements that the NRC staff have identified as possibly requiring a methodology equivalent to a capability category III evaluation to be consistent with the flooding analyses approved for use by the staff in previous RI-ISI methodologies, were either equivalent to a category III or were not applicable to the licensee's evaluation. Therefore, the technical adequacy of the PRA analysis used to support the RIS_B risk impact does not rely on the grades assigned in NEI 05-04 for RI-ISI applications.

The second of the two qualifications in Table B-5 of RG 1.200 is that the assigned supporting requirement grades accepted by the NRC for a specific application will include consideration of the clarifications and qualifications to the ASME PRA Standard provided in Appendix A of RG 1.200. The licensee stated in its letter dated March 16,2009, that the peer review included consideration of the NRC staff positions provided in Appendix A of RG 1.200, Revision 1.

The NRC staff concludes that NMP1 has demonstrated that its PRA methods and analyses are consistent with the guidance provided in RG 1.200 and the flooding analyses approved for use in previous RI-ISI applications. Therefore, the NMP1 PRA is adequate to support the development of the RIS_B program.

The change in risk assessment in the EPRI-TR permits using each segment's CCDP and CLERP in the change in risk estimate. Alternatively, the EPRI-TR permits placing segments into high-, medium-, or low-consequence "bins" and using a single bounding CCDP and CLERP for all segments in each consequence bin. N-716 also permits use of either estimated or bounding consequence values. The bounding values to be used in the bounding analysis are the same as those approved for use in the EPRI-TR. In its letter dated March 16, 2009, the licensee identified the different types of pipe failures that cause major plant transients such as those causing loss-of-coolant accidents (LOCAs) and unisolated LOCAs. Conservative CCDP estimates were developed from the PRA for breaks in locations that could cause these initiating events. These estimated CCDP/CLERP values were used for all high-consequence inspection locations. NMP1 uses the upper bound CCDP/CLERF for the medium consequence bin as the CCDP/CLERP for all medium- and low-consequence locations.

Using the upper-bound CCDP/CLERP will overestimate the risk increase at locations when inspections are discontinued, but will also overestimate the risk decrease at locations where inspections are added. In its letter dated October 2, 2009, the licensee reported two sensitivity studies to determine whether this could impact the proposed program. The licensee first used the "estimated" impact for all locations (including medium-consequence locations) where a CCDP/CLERP was estimated. Second, the licensee used the bounding CCDP/CLERP estimates, but set the number of increased inspections to zero in each risk category where the number of inspections has increased. The licensee reported that both studies yielded results that complied with the risk increase acceptance guidelines demonstrating that the acceptability of the change in risk does not rely on overestimating risk decrease from the new locations.

The change in risk evaluation approved in the EPRI-TR method 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 that change, and that a licensee implements it only upon

- 11 determining with reasonable confidence that any increase in risk is small and acceptable. The licensee's method is consistent with the approved EPRI-TR method with the exception that the change in risk calculation in N-716 includes the risk increase from discontinued inspection in LSS locations whereas the EPRI-TR method does not. Based on the detailed analysis of every segment required by the EPRI-TR, the NRC staff concluded in programs developed according to the ERPR-TR that there is a high confidence that the total increase in risk from all discontinued inspections in LSS segments would be negligible and does not need to be quantified. The NRC staff concludes that the licensee's method described in the submittal is acceptable because the deviation from the approved EPRI-TR method expands the scope of the calculated change in risk, thereby providing confidence that the less detailed analyses of LSS segments required by N-716 does not result in an unanticipated and potentially unacceptable risk increase.

The licensee summarized the results of the change in risk calculations in the submittal and noted that all the estimates satisfy both the system level and the total guidelines. Therefore, the NRC staff finds that any increase in risk is small and acceptable.

3.8 Implementation Monitoring and Feedback The objective of this element of RG 1.174 and RG 1.178 is to assess performance of the affected piping systems under the proposed RI-ISI program by implementing monitoring strategies that conform with the assumptions and analysis used in developing the RIS_B program. In its letter dated March 16, 2009, the licensee states that upon approval of the RIS_B program, procedures that comply with the guidelines described in N-716 will be prepared to implement and monitor the program.

This list of possible changes includes all changes at the facility or in the PRA that could affect the evaluation used to develop the RIS_B program and performing the reevaluation every lSI period coincides with the inspection periods in the inspection program requirements contained in ASME Code,Section XI. The NRC staff finds that the proposed procedures are consistent with the performance monitoring guidelines described in RG 1.178 and are, therefore, acceptable.

3.9 Examination Methods In accordance with N-716, LSS welds will be exempt from the volumetric, surface, VT-1 and VT 3 visual examination requirements of Section XI. Ten percent of the HSS welds will be selected for examination as addressed in Section 3.6 of this SE. Section 4 of N-716 directs users to Table 1 for the examination requirements of the welds selected for examination. The examination method is based on the postulated degradation for the selected weld. In addition, the N-716 methodology provides for increased inspection volumes for those locations that are included in the NDE portion of the program. Table 1 of N-716 is consistent with the traditional RI-ISI approach for examination methods as approved in EPRI TR-112657. The examination methods are based on an inspection-for-cause philosophy, so that when there is a potential for a certain degradation mechanism, the examination method selected would be one that would be able to detect that type of degradation. This is consistent with the guidelines for inspection strategies described in the Standard Review Plan, Section 3.9.8 and is, therefore, acceptable.

- 12

4.0 CONCLUSION

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 proposed to use an alternative to the risk-informed process described in Code Case N-716 which is based, in large part, on NRC-approved EPRI-TR-112657. The implementation strategy is consistent with the EPRI-TR 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 the EPRI-TR methodology, the existing ASME Code performance measurement strategies will remain in place.

The NRC-approved EPRI-TR methodology contains details for developing an acceptable RI-ISI program. Code Case N-716, modified as described by the licensee in its submittals, describes a methodology similar to the EPRI-TR methodology but with several differences as described above in this SE. 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 the EPRI-TR, is consistent with the guidance provided in RG 1.178, and satisfies the guidelines established in RG 1.174.

The NRC staff concludes that the licensee's proposed RIS_B program will provide an acceptable level of quality and safety pursuant to 10 CFR 50.55a(a)(3)(i) for the proposed alternative to the piping lSI requirements with regard to (1) the number of locations, (2) the locations of inspections, and (3) the methods of inspection. Therefore, the proposed RI-ISI program is authorized for the remainder of the fourth 10-year lSI interval pursuant to 10 CFR 50.55a(a)(3)(i) on the basis that this alternative will provide an acceptable level of quality and safety.

Principal Contributors: A. EI-Bassioni, NRR K. Hoffman, I\IRR Date: March 15, 2010

Mr. Samuel L. Belcher Vice President Nine Mile Point Nine Mile Point Nuclear Station, LLC P.O. Box 63 Lycoming, NY 13093

SUBJECT:

NINE MILE POINT NUCLEAR STATION, UNIT NO.1 - REQUEST FOR ALTERNATIVE 1ISI-003, REQUEST TO USE ASME CODE CASE N-716 ASSOCIATED WITH THE FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL (TAC NO. ME0993)

Dear Mr. Belcher:

By letter dated March 16, 2009, as supplemented by letters dated October 2, 2009 and January 28,2010, Nine Mile Point Nuclear Station, LLC (NMPNS, the licensee), submitted Relief Request (RR) 11SI-003 pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(a)(3)(i) for Nine Mile Point, Unit NO.1 (NMP1). The request for relief would implement a risk-informed, safety based (RIS_B) inservice inspection (lSI) program for piping at NMP1.

The proposed program is based, in part, on the American Society of Mechanical Engineering Boiler and Pressure Vessel Code,Section XI, Code Case N-716.

The Nuclear Regulatory Commission (NRC) staff has reviewed the subject request, and concludes 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 licensee's fourth 10-year lSI interval. The NRC staff's approval of the licensee's RIS_B program does not constitute approval of Code Case N-716. The results of the NRC staff's review are provided in the enclosed safety evaluation.

If you have any questions regarding this approval, please contact Richard Guzman, at 301-415 1030 or Richard.Guzman@nrc.gov.

Sincerely, IRA!

Nancy L. Salgado, Chief Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-220

Enclosure:

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

PUBLIC RidsNrrPMRGuzman RidsNrrLASLittie RidsNrrDraApla LPLI-1 R/F RidsOGCRp RidsRgn1 MailCenter RidsNrrDciCpnb K. Hoffman, NRR A. EI-Bassioni, NRR S. Dinsmore, NRR RidsNrrAcrsAcnw&mMailCenter Accession Number: ML100700034 'concurrence via e-mal., "SE' npu pravi'd edbJV memo No su bstantla

. I chanqes ma d e.

OFFICE LPL 1-1/PM LPL 1-1/LA APLAlBC CPNB/BC LPL1-1/BC NAME RGuzman SLittle* DHarrison** TLuphold** NSalgado DATE 03/11/10 03/11/10 03/09/10 03/09/10 03/15/10 OFFICIAL RECORD COPY