ML14083A631

Relief Request PRR-22 Regarding a Risk-Informed Inservice Inspection Program for Class 1 and 2 Piping Welds

ML14083A631
Person / Time
Site:	Pilgrim
Issue date:	03/27/2014
From:	Benjamin Beasley Plant Licensing Branch 1
To:	Dent J Entergy Nuclear Operations
Morgan N
References
TAC MF1428
Download: ML14083A631 (16)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 27, 2014 Mr. John Dent, Jr.

Site Vice President Entergy Nuclear Operations, Inc.

Pilgrim Nuclear Power Station 600 Rocky Hill Road Plymouth, MA 02360-5508

SUBJECT:

PILGRIM NUCLEAR POWER PLANT - RELIEF REQUEST PRR-22 REGARDING A RISK-INFORMED JNSERVICE INSPECTION PROGRAM FOR CLASS 1 AND 2 PIPING WELDS (TAC NO. MF1428)

Dear Mr. Dent:

By letter dated April 10, 2013, as supplemented by Jetter dated December 20, 2013, Entergy Nuclear Operations, Inc., the licensee, submitted Relief Request PRR-22 for authorization of a proposed alternative to the nondestructive examination requirements for Class 1 and 2 piping of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),

Section XI, Examination Categories B-F, B-J, C-F-1, and C-F-2 for Pilgrim Nuclear Power Station (Pilgrim). Specifically, the licensee proposed to use RIS_B, a risk-informed/

safety-based inservice inspection (lSI) program in the third period, of the fourth 10-year lSI interval, July 1, 2012 through June 30, 2015. Pursuant to Title 10 of the Code of Federal Regulations (CFR) Section 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 Nuclear Regulatory Commission (NRC) staff has reviewed the subject request and concluded that the proposed alternative provides an acceptable level of quality and safety.

Accordingly, the NRC staff concluded that the licensee adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(a)(3){i), and is in compliance with the ASME Code's requirements. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the licensee's proposed alternative, RIS_B program, as described in PRR-22, for the third period of the fourth 10-year lSI interval at Pilgrim.

All other ASME Code,Section XI requirements for which relief was not specifically requested and authorized in the subject proposed alternative remain applicable, including third-party review by the Authorized Nuclear lnservice Inspector.

J. Dent, Jr. If you have any questions, please contact the Pilgrim Project Manager, Nadiyah Morgan, at (301) 415-1016.

Sincerely, Benjamin G. Beasley, Chief Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-293

Enclosure:

Safety Evaluation cc w/encl: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST PRR-22 REGARDING RISK-INFORMED INSERVICE INSPECTION PROGRAM ENTERGY NUCLEAR OPERATIONS. INC PILGRIM NUCLEAR POWER STATION DOCKET NO. 50-293

1.0 INTRODUCTION

By letter dated April10, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13114A053}, as supplemented by letter dated December 20, 2013 (ADAMS Accession No. ML13361A158), Entergy Nuclear Operations, Inc., the licensee, submitted Relief Request PRR-22 for authorization of a proposed alternative to the nondestructive examination (NDE) requirements for Class 1 and 2 piping of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code},Section XI, Examination Categories B-F, B-J, C-F-1, and C-F-2 for Pilgrim Nuclear Power Station (Pilgrim).

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

the licensee requested to use RIS_B, a risk-informed (RI}/safety-based inservice inspection (lSI) program, based on the ASME Code Case N-716, "Alternative Piping Classification and Examination Requirements,Section XI Division 1" (Reference 1}, in the third period of the fourth 10-year lSI interval, July 1, 2012 through June 30, 2015 on the basis that the proposed alternative provides an acceptable level of quality and safety.

2.0 BACKGROUND

The ASME Code Case N-716 has not been approved for generic use by the Nuclear Regulatory Commission (NRC or the Commission). The licensee's PRR-22 refers to a modified version of the methodology described in ASME Code Case N-716, while developing its proposed RIS_B program. The ASME Code Case N-716 is incorporated in this safety evaluation (SE) as a source of information. The NRC staff is not endorsing the use of ASME Code Case N-716 in this SE.

3.0 REGULATORY EVALUATION

Pursuant to 10 CFR 50.55a(g), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements set forth in the ASME Code to the extent practical within the Enclosure

limitations of the design, geometry, and materials of construction of the components.

Paragraph 50.55a(g) of 10 CFR 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 written relief has been granted by the NRC.

The regulations at 10 CFR 50.55a(g)(4)(i) and (ii) require, during the first 10-year lSI interval and during subsequent intervals, that the licensee's lSI program comply with the requirements in the latest edition and addenda of the ASME Code incorporated by reference into 10 CFR 50.55a(b) 12 months before the start of the 120-month inspection interval, subject to the conditions listed in 10 CFR 50.55a(b). The applicable edition of Section XI of the ASME Code for the Pilgrim fourth 10-year lSI interval is the 1998 Edition with the 2000 Addenda.

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 B-F welds and 25 percent of 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.

In accordance with 10 CFR 50.55a(a)(3), the NRC may authorize alternatives to the requirements of 10 CFR 50.55a(g), if an applicant or licensee demonstrates that the proposed alternatives would provide an acceptable level of quality and safety, or that compliance with the specified requirements of 10 CFR 50.55a 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 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 on the basis that it provides an acceptable level of quality and safety.

The NRC staff reviewed the development of the proposed RIS_B program using the following documents:

• NUREG-0800, Chapter 3.9.8, "Standard Review Plan [SRP] for the Review of [RI lSI] of Piping" dated September 2003 (ADAMS Accession No. ML032510135),

• Regulatory Guide (RG) 1.174, "An Approach for Using Probabilistic Risk Assessment

[PRA] in [RI] Decisions on Plant-Specific Changes to the Licensing Basis," Revision 1, dated November 2002 (ADAMS Accession No. ML023240437),

• RG 1.178, "An Approach for Plant-Specific [RI] Decisionmaking for lnservice Inspection of Piping," Revision 1, dated September 2003 (ADAMS Accession No. ML032510128),

and

• RG 1.200, "An Approach for Determining the Technical Adequacy of [PRA] Results for

[RI] Activities," Revision 1, dated January 2007 (ADAMS Accession No. ML070240001 ).

Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request the use of this alternative and the NRC to authorize the proposed alternative.

4.0 TECHNICAL EVALUATION

4.1 PRR-22 Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee requested authorization of a proposed alternative to the NDE requirements of the ASME Code,Section XI, 1998 Edition through the 2000 Addenda, Division 1, Tables IWB-2500-1 and IWC-2500-1, for all Class 1 and 2 piping welds (Groups A and B)- Examination Categories 8-F, 8-J, C-F-1, and C-F-2 for Pilgrim.

The proposed alternative would implement RIS_B, a Rl/safety-based lSI program. The proposed RIS_B program is based, in part, on ASME Code Case N-716. The licensee plans to implement the proposed alternative in the third period of the fourth 10-year lSI interval, July 1, 2012 through June 30, 2015 at Pilgrim.

4.2 NRC Staff Evaluation The ASME Code Case N-716 is founded, in large part, on the RI-ISI process as described in Electric Power Research Institute (EPRI) Topical Report (TR)-112657, "Revised Risk-Informed lnservice Inspection Evaluation Procedure," Revision B-A (Reference 2}, which was previously reviewed and approved by the NRC.

The RG 1.174 provides guidance on the use of PRA findings and risk insights in support of licensee's request for changes to a plant's licensing basis. The RG 1.178 describes an 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 EPRI TR-112657 provides a detailed methodology that the NRC staff has previously concluded will result in an acceptable RI-ISI program. The RIS_B program proposed by the licensee also incorporates risk insights to focus inspection on more important locations, although the methodology differs in several respects from the methodology in EPRI TR-112657. This SE describes and evaluates the differences between the endorsed methodology in EPRI TR-112657 and the proposed RIS_B methodology to reach a conclusion about the acceptability of the proposed method.

An acceptable RI-ISI program replaces the number and locations of NDE inspections based on ASME Code Section XI requirements by the number and locations of these inspection based on the RI-ISI guidelines. The proposed RIS_B program permits alternatives to the requirements of IWB-2420, IWB-2430, IWB-2500 (Examination Categories B-F and 8-J), IWC-2420, IWC-2430, and IWC-2500 (Examination Categories C-F-1 and C-F-2), or as additional requirements for Subsection IWD. Also, the proposed RIS_B program may be used for lSI and pre-service 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. Visual examinations (VT-2) are scheduled in accordance with the Pilgrim pressure and leak test program which remains unaffected by the proposed RIS_B program.

The process described in EPRI TR-112657 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

• lnspection/NDE Selection

• Risk Impact Assessment

• Implementation Monitoring and Feedback These steps 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 adequate protection of public health and safety. In general, the methodology in ASME Code Case N-716 replaces a detailed evaluation of the safety significance of each pipe segment with a generic population of high safety-significance (HSS) segments, followed by a flooding analysis to identify any plant-specific HSS segments. The flooding analysis was performed in accordance with Section 4.5.7 of ASME RA-Sb-2005, "Standard for [PRA] for Nuclear Power Plant Applications," Addendum B to ASME RA-S-2002 dated December 2005 (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 the licensee has applied to develop its program with the steps from EPRI TR-112657.

4.2.1 Scope Definition The scope of evaluation to support RIS_B program development, and of the proposed changes, in ASME Code Case N-716 and the licensee's PRR-22 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 SRP 3.9.8 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 Pilgrim'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. The change in risk estimate is used by the licensee to demonstrate that risk increases are small. The RG 1.178 clarifies that a "full-scope" Rl evaluation is acceptable, where the definition of full-scope is consistent with the scope as defined in ASME Code Case N-716.

Therefore, the NRC staff finds that the "full-scope" extent of the piping included in the RIS_B program changes satisfies the guidelines in SRP 3.9.8 and RG 1.178, and is acceptable.

4.2.2 Consequence Evaluation The methodology described in RG 1.178 and EPRI TR-112657 divides all piping within the scope of the proposed EPRI-TR 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 segments.

In contrast to the EPRI TR-112657 methodology, ASME 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, ASME 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 assigned 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 ASME 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 RI-ISI programs were 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, EPRI TR-112657, and SRP 3.9.8. Therefore, the generic results are derived from acceptable analyses.

Section 2(a)(5) in ASME 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 used its PRA of pressure boundary failures {flooding analysis) to search for additional plant-specific HSS segments. 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 PRA described 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 SRP 3.9.8 and is, therefore, acceptable.

4.2.3 Degradation Mechanism Evaluation The EPRI TR-112657 requires a determination of 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 EPRI TR-112657. This information is used to support the safety significance determination for all segments, to target inspections toward the locations with degradation mechanisms in the segments that require inspections, and to provide estimates of weld failure frequencies to support the change in risk evaluation. Once a segment is placed in the low safety-significant (LSS) category, the degradation mechanisms at the welds in that segment are not further used in the development of the EPRI TR-112657 RI-ISI program because no inspections are required in LSS segments and the discontinued inspections in LSS segments are not included in the change in risk estimate.

The ASME Code Case N-716 identifies a generic population of HSS welds, followed by a search for plant-specific HSS welds, and requires a determination of the susceptibility to all degradation mechanisms of all welds assigned generically as HSS. The degradation mechanisms considered in ASME Code Case N-716 are consistent with those identified in EPRI

TR-112657, which the NRC staff has previously concluded is a sufficiently comprehensive list of the applicable degradation mechanisms.

Pipe failure frequencies are used in the screening analysis searching for plant-specific HSS welds described in Section 3.2.2 of this SE, and then in the change in risk estimate. If welds are exposed to any degradation mechanism, aside from flow-accelerated corrosion (FAC) and water hammer, a medium failure frequency is assigned to those welds. If welds are exposed to FAC or water hammer, a high failure frequency is assigned. Finally, if there are no damage mechanisms, a low failure frequency is assigned. This is consistent with the approved methodology in EPRI TR-112657.

The licensee stated in Section 3.4.1 of its Apri110, 2013, letter that the presence of FAC was adjusted for in the quantitative analysis by excluding its impact on the failure potential rank. The exclusion of the impact of FAC was performed because the licensee manages this damage mechanism through the plant augmented inspection program for FAC per Generic Letter (GL) 89-08, "Erosion/Corrosion-Induced Pipe Wall Thinning" (Reference 4). The EPRI TR-112657 notes that the plant's existing FAC program in response to GL 89-09 would not be affected by the RI-ISI program. The NRC staff found this to be acceptable in Section 3.2.1 of Reference 6.

For HSS welds, the licensee stated in its December 20, 2013, response to a request for additional information that during a service history review, it identified one water hammer event in 1995 that impacted Class 1 residual heat removal (RHR) piping during system alignment and a potential water hammer event in 2011 in the RHR system. Corrective actions included enhanced operator training and a procedure enhancement to preclude water hammer events.

Given the corrective actions and that the service history review did not identify any other water hammer events, the NRC staff finds that HSS piping is not susceptible to water hammer. For LSS welds, the licensee stated in Section 3.4.1 of its December 20, 2013, letter that a review was conducted to verify that LSS piping was not susceptible to water hammer. In lieu of conducting a degradation mechanism evaluation for all LSS piping, the licensee assigned these locations to the medium failure potential for the purpose of assigning a failure frequency to calculate the change in risk. This results in conservative failure frequency estimates because these failure frequencies would always be equal or greater than those used in the analysis if the susceptibility of all LSS welds to all degradation mechanisms was determined.

The approach proposed by the licensee used failure frequency estimates that reflected applicable degradation mechanisms while searching for plant-specific HSS piping. Failure frequency estimates are further refined for use in the change in risk estimate by identifying degradation mechanisms at all HSS welds and in LSS welds with potential high failure frequency (i.e., susceptible to FAC or water hammer). Therefore, the NRC staff finds that the screening evaluation relying on a plant-specific update of generic failure frequencies, followed by a bounding analysis for specific welds where inspections will be added or discontinued, is acceptable because the licensee's methods fulfills the requirements for identifying locations that should be inspected (i.e., identifying additional plant-specific HSS segments) and developing a bounding estimate for the change in risk.

4.2.4 Piping Segment Definition Previous guidance on RI-ISI including RG 1.178, SRP 3.9.8, and both approved industry methodologies centered on defining and using piping segments. The RG 1.178 states, in part, that the analysis and definition of a piping segment must be consistent and technically sound.

The primary purpose of the piping 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 ASME Code Case N-716 identifies 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 ASME Code Case N-716 uses a PRAto identify plant-specific piping that might be assigned HSS. The process described by the licensee to search for plant-specific HSS piping first identifies zones that may be sensitive to flooding, and then evaluates 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 category, 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. The ASME Code Case N-716 generically defines a large population of welds as HSS. An additional population of welds may be added based on the Rl search for plant-specific HSS segments. When complete, the ASME Code Case N-716 process yields a well-defined population of HSS welds from which inspections must be selected. This accomplishes the same objective as accounting for each weld throughout the analysis by using segments. The ASME Code Case N-716, as applied by the licensee, 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 finds that the segment identification in RG 1.178, as used as an accounting tool, is not needed within the generic population of HSS welds. The Rl 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.

4.2.5 Risk Categorization Section 2(a)(1) through 2{a){4) in ASME Code Case N-716 identify the portions of systems that should be generically assigned 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 the ASME 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. The ASME Code Case N-716 requires that any

o-segment with a total estimated CDF greater than 1 x 1 6 per year be assigned to the HSS category. The licensee augmented this ASME Code Case N-716 metric on CDF with the requirement to also assign the HSS category to any segment with a total estimated large early o-release frequency (LERF) greater than 1 x 1 7 per year. These guideline values are suitably small and consistent with the decision guidelines for acceptable changes in CDF and LERF found in RG 1.174.

In PRR-22, 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 ASME 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 1.174. 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 ASME Code Case N-716.

The NRC staff finds 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 Fussei-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." 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 Section 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. The RG 1.200 states that compliance with the attributes of an NRC-endorsed industry PRA standard may be used to demonstrate that a PRA is adequate to support a Rl application. The 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 Appendix A of its April 10, 2013, letter, the licensee described the resolution of the findings (i.e., a subset of the facts and observations) from the peer review of the Pilgrim flooding analysis. The licensee reviewed the results of its flooding analysis and did not identify any segments that had a CDF greater than 1 X 10"6 per year or a LERF greater than 1 X 10"7 per year.

The NRC staff finds that the CDF and LERF metrics proposed by the licensee are acceptable because they address the risk elements that form the basis for Rl applications. The NRC staff accepts the ancillary metrics and guidelines on CDF and LERF and the change in risk acceptance guidelines in RG 1.174 that are used to add plant-specific HSS segments to the RIS_B program.

4.2.6 lnspection/NDE Selection The licensee discussed the impact of the proposed RIS_B application on the various augmented inspection programs.

• The Pilgrim augmented inspection program, BWRVIP-75-A, "BWR Vessel and Internals Project, Technical Basis for Revisions to [GL] 88-01 Inspection Schedules," for managing intergranular stress corrosion cracking for Class 1 stainless steel and nickel-based alloy remains unchanged.

• The EPRI TR-112657 and ASME 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" (Reference 4). Pilgrim's FAC program is relied upon to manage this damage mechanism, but is not otherwise affected or changed by the RIS_B program.

• The Pilgrim augmented inspection program for localized corrosion per NRC GL 89-13, "Service Water System Problems Affecting Safety-Related Equipment" (Reference 5), is relied upon to manage this damage mechanism.

The NRC staff finds the licensee's approach to the integration of the proposed RI-ISI program with augmented inspection programs, as described above, is acceptable because it is consistent with the EPRI TR-112657.

Additionally, ASME 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 PRR-22, the licensee addressed these requirements and provided a brief summary of the identified number of welds and location of required examinations. The NRC staff finds this acceptable because the information provided is consistent with that required by the EPRI TR-112657.

The NRC staff reviewed the tables addressing degradation mechanisms, failure potential, and the number of welds selected for examination. The NRC staff finds that the data contained in these tables along with the additional information provided in the licensee's December 20, 2013, letter is consistent with the requirements of the EPRI TR-112657, and therefore, is acceptable.

4.2.7 Risk Impact Assessment The licensee used a change in risk estimation process approved by the NRC staff in EPRI TR-112657. The change in risk assessment in 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. The ASME Code Case N-716 includes both alternatives and the bounding values to be used in the bounding analyses, which are the same as those approved for use in EPRI TR-112657. Pilgrim 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 first table of Section 3.4.1 of its April 10, 2013, letter, the licensee identified the different types of pipe failures that cause major plant transients, such as those causing loss-of-coolant accidents (LOCAs), isolable LOCAs, and potential LOCAs. Based on these initiating events, conservative CCDP and CLERP estimates were developed from the PRA.

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 finds that the scenarios described are reasonable because they identify the appropriate

equipment failure modes that cause a 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 major plant transients and for which a consequence estimate is required. The licensee's flooding analysis indicated that the majority of the LSS Class 2 piping did not have high-consequence segments (lower bound of CCDP and CLERP of 1 x 104 and 1 x 10*5 , respectively). Class 2 piping connected to the RHR system were high-consequence segments. The licensee placed the LSS Class 2 piping into the medium consequence bin, and the Class 2 piping connected to the RHR system into the high-consequence bin.

Section 5 of ASME Code Case N-716 requires that any piping that has NDE inspections1 added or removed be included in the change in risk evaluation. The licensee used the upper-bound values found in the first table of Section 3.4.1 of its April1 0, 2013, letter for CCDP and CLERP.

Acceptance criteria provided in Section 5(d) of ASME Code Case N-716 include limits of 1 x 10-7 o-s per year and 1 x 1 per year for increase of CDF and LERF for each system, and limits of o- o-1 x 1 6 per year and 1 x 1 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 therefore, are acceptable.

The change in risk evaluation approved in EPRI TR-112657 is a final screening to ensure that a licensee replacing the ASME Code,Section XI program with the Rl alternative evaluates the potential change in risk resulting from that change 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 ASME Code Case N-716 includes the risk increase from discontinued inspection in LSS segments. Based on the detailed analysis of every segment required by EPRI TR-112657, the NRC staff finds that there is a high confidence that the total increase in risk from all discontinued inspections in LSS segments would be negligible. The NRC staff finds that the licensee's described method 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 ASME Code Case N-716 does not result in an unanticipated and potentially unacceptable risk increase.

In the second table of Section 3.4.1 of the April 10, 2013, letter, the licensee provided the results of the change in risk calculations and noted that all the estimates satisfy both the system level and total CDF and LERF guidelines. Therefore, the NRC staff finds that any increase in risk is small, and therefore, acceptable.

1 ASME 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.

4.2.8 Implementation Monitoring and Feedback The objective of this element of RGs 1.174 and 1.178 is to assess performance of the affected piping systems under the proposed RI-ISI program by implementing monitoring strategies that conform to the assumptions and analysis used in developing the RIS_B program. In Section 3.5 of its April 10, 2013, letter, the licensee stated that upon approval of the RIS_B program, procedures that comply with the guidelines described in ASME Code Case N-716 will be prepared to implement and monitor the program.

The program implementation process described in EPRI TR-112657 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 ASME Code,Section XI, but 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: (1) changes in plant design features, (2) changes in plant procedures, (3) equipment performance changes, (4) examination results, and (5) plant or industry operating experience.

The 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 the 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 therefore, are acceptable.

4.2.9 Examination Methods Section 4 of the EPRI TR-112657 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-112657 summarizes the degradation mechanisms expected and the examination methods which are appropriate. Specific references are provided to the ASME Code concerning the manner in which the examination is conducted and the acceptance standard.

The ASME Code Case addresses degradation mechanism/inspection technique. Like Table 4.1 of the EPRI TR-112657, Table 1 of the ASME Code Case N-7161ists degradation mechanism and corresponding inspection techniques. This table also provides references to the ASME Code concerning the manner in which the examination is conduced and the acceptance standard.

In PRR-22, the licensee stated that the implementation of the RI-ISI program will conform to ASME Code Case N-716, i.e., each HSS piping segment will be assigned to the appropriate item number within Table 1 of the ASME Code Case N-716. The NRC staff finds this acceptable because ( 1) proper assignment of piping segments into Table 1 will ensure that appropriate inspections to detect the degradation mechanism under consideration are conducted and (2) it is consistent with the EPRI TR-112657, which has been reviewed and approved by the NRC, and the ASME Code Case includes additional ASME Code item numbers to assign NDE requirements to all HSS locations including those segments where no degradation mechanism has been identified.

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 Rl 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-112657 methodology, the existing ASME Code performance measurement strategies will remain in place. In addition, the ASME Code Case N-716 methodology provides for increased inspection volumes for those locations that are included in the NDE portion of the program.

A modified version of the ASME Code Case N-716, presented by the licensee in PRR-22, uses a methodology similar to the EPRI TR-112657 methodology but with some differences, which are described 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 EPRI TR-112657, is consistent with the guidance provided in RG 1.178, and therefore, satisfies the guidelines established in RG 1.174.

5.0 CONCLUSION

S As set forth above, the NRC staff has concluded 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 50.55 a, and is in compliance with the ASME Code's requirements. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the licensee's proposed alternative, RIS_8 program, as described in PRR-22, for the third period of the fourth 10-year lSI interval at Pilgrim.

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 Authorized Nuclear lnservice Inspector.

6.0 REFERENCES

1. ASME Code Case N-716, Alternative Piping Classification and Examination Requirements,Section XI Division 1, © ASME, New York, New York, April19, 2006.

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

3. ASME RA-Sb-2005, Standard for Probabilistic Risk Assessment for Nuclear Power Plant Applications, Addendum 8 to ASME RA-S-2002, © ASME, New York, New York, December 30, 2005.

4. NRC GL 89-08, Erosion/Corrosion-Induced Pipe Wall Thinning, May 2, 1989 (ADAMS Accession No. ML031200731).

5. NRC GL 89-13, Service Water System Problems Affecting Safety-Related Equipment, July 18, 1989 {ADAMS Accession No. ML031150348).

6. NRC Safety Evaluation Report Related to "Revised Risk-Informed lnservice Inspection Evaluation Procedure" (EPRI TR-112657, Rev. B, July 1999), October 28, 1999 (ADAMS Accession No. ML993190474).

Principal Contributors: K. Hoffman J. DeJesus Date: March 27, 2014

J. Dent, Jr. If you have any questions, please contact the Pilgrim Project Manager, Nadiyah Morgan, at (301) 415-1016.

Sincerely, Ira/

Benjamin G. Beasley, Chief Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-293

Enclosure:

Safety Evaluation cc w/encl: Distribution via Listserv DISTRIBUTION:

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