ML12313A153

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Safety Evaluation in Support of 10 CFR 50.55A Requests for Alternative Examination Requirements for American Society of Mechanical Engineers Class 1 Piping Welds
ML12313A153
Person / Time
Site: Perry FirstEnergy icon.png
Issue date: 11/14/2012
From: Michael Dudek
Plant Licensing Branch III
To: Kaminskas V
FirstEnergy Nuclear Operating Co
Michael Mahoney, 415-3867
References
TAC ME7564
Download: ML12313A153 (9)
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Text

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Mr. Vito A. Kaminskas Site Vice President FirstEnergy Nuclear Operating Company Mail Stop A-PY -A290 P.O. Box 97, 10 Center Road Perry,OH 44081-0097

SUBJECT:

PERRY NUCLEAR POWER PLANT, UNIT 1 - SAFETY EVALUATION IN SUPPORT OF 10 CFR 50.55A REQUESTS FOR ALTERNATIVE EXAMINATION REQUIREMENTS FOR AMERICAN SOCIETY OF MECHNICAL ENGINEERS CLASS 1 PIPING WELDS (TAC NO. ME7564)

Dear Mr. Kaminskas:

By letter to the U.S. Nuclear Regulatory Commission (NRC), dated November 14, 2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML113180450), as supplemented by letters dated August 10, 2012, and October 4, 2012 (ADAMS Accession Nos. ML12226A244 and ML12279A118, respectively), FirstEnergy Nuclear Operating Company (the licensee) requested approval for continued use of the existing Perry Nuclear Power Plant (PPNP), Unit No.1, risk-informed inservice inspection (RI-ISI) program, with updates, relative to certain non-destructive examination requirements associated with the American Society of Mechanical Engineers, Class 1, piping welds. The proposed alternative is designated by the licensee as IR-049, Revision 1. The proposed alternative will be implemented during the PNPP third 1O-year RI-ISI interval, currently scheduled to expire on l\IIay 17,2019.

Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in Title 10 of the Code of Federal Regulations (CFR), Section 5O.55a(a)(3)(i), and is in compliance with the requirements of 10 CFR 50.55a with the authorizing of this alternative contained in IR-049, Revision 1. Therefore, the NRC staff authorizes the licensee's proposed alternative contained in IR-049, Revision 1. The NRC staff's safety evaluation is enclosed.

Please contact the PNNP Project Manager, Michael Mahoney at (301) 415-3867 if you have any questions regarding this action.

Sincerely,

~ry-al Michael I. Dudek, Chief Plant licensing Branch 111-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-440

Enclosure:

Safety Evaluation cc w/encl: Distribution via Listserv

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ON THE REQUEST FOR ALTERNATIVE EXAMINATIONS REQUIREMENTS FOR ASME CLASS I PIPING WELDS FIRSTENERGY NUCLEAR OPERATING COMPANY PERRY NUCLEAR POWER PLANT, UNIT NO.1 DOCKET NUMBER: STN 50-440

1.0 INTRODUCTION

By letter to the U.S. Nuclear Regulatory Commission (NRC), dated November 14,2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML113180450), as supplemented by letters dated August 10, 2012, and October 4,2012 (ADAMS Accession Nos. ML12226A244 and ML12279A118, respectively), FirstEnergy Nuclear Operating Company (FENOC, the licensee) requested NRC authorization to extend the risk informed inservice inspection (RI-ISI) program plan for Perry Nuclear Power Plant (PNPP),

Unit No.1, to the third 10-year RI-ISI interval, currently scheduled to expire on May 17, 2019 The PNPP RI-ISI program was initially submitted to the NRC in a letter dated February 12, 2001 (ADAMS Accession No. ML010470098), and supplemented by letter dated July 9, 2001 (ADAMS Accession No. ML012050263). The PNPP RI-ISI was reviewed and approved by the NRC for use in the second 10-year RI-ISI interval by letter dated October 17, 2001 (ADAMS Accession No. ML012640496).

The licensee evaluated relevant information since the development of the original program in consideration of updating the RI-ISI program. The November 14, 2011, submittal proposed the continuation of the Rt-ISI program during the third 1O-year RI-ISI interval, currently scheduled to expire on May 17, 2019.

2.0 REGULATORY REQUIREMENTS Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(g), the American Society of Mechanical Engineers (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 ASME 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 RI-ISI 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.

-2 The regulations also require, during the first 1O-year RI-ISI interval and during subsequent intervals, that the licensee's RI-ISI 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.

PNPP is currently in its third 10-year RI-ISI interval.

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

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 NRC staff has developed the following documents to evaluate proposed RI-ISI programs:

  • RG 1.178, "An Approach For Plant-Specific Risk-Informed Decision Making - Inservice Inspection of Piping" (ADAMS Accession No. ML032510128); and
  • 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 EVALUATION 3.1 Proposed Alternative IR-013. Revision 2, ASME Code,Section XI, Table IWC-2500 Examination Category C-G, Item C6.1 O. Pressure Retaining Welds in Pumps and Valves

-3 3.1.1 Components for which Relief is Requested ASME Code, Class 1, piping welds as listed in Table 1 of the licensees November 12, 2011, application.

3.1.2 ASME Code Requirements IW8-2500, Examination and Pressure Test Requirements Table IW8-2500-1, Examination Categories Class 1 Piping Welds Category 8-F, Pressure Retaining Dissimilar Metal Welds in Vessel Nozzles Item Nos. 85.10, 85.20, 85.30 Category 8-J, Pressure Retaining Metal Welds in Piping Items Nos. 89.11, 89.21, 89.31, 89.32, 89.40 3.1.3 Licensee's Proposed Altemative to ASME Code The licensee is proposing to continue use of the PNPP RI-ISI program plan in the third 10-year RI-ISI interval as an alternative to the current ASME Code,Section XI, 2001 Edition through the 2003 Addenda, examination requirements for Class 1 Examination Category 8-F and 8-J piping welds. The RI-ISI program approved for use in the second 1O-year inspection interval was submitted by the licensee in a letter dated February 12, 2001. The proposed alternative is sought for the PNPP third 10-year RHSI interval which is scheduled to end on May 17,2019.

The licensee's process used to develop the initial RI-ISI program was based on Electric Power Research Institute, Inc. (EPRI) Topical Report (TR)-112657, "Revised Risk-Informed Inservice Inspection Evaluation Procedure," Revision 8-A, dated December 1999. In its November 14, 2011, submittal, the licensee stated that the RI-ISI program had been updated and continued to meet EPRI TR-112657 and RG 1.174.

3.1.4 Licensee's Reason for Request On October 17, 2001, the NRC staff approved the PNPP RI-ISI Program for use during the second and third periods of the 1O-year RI-ISI interval (ADAMS Accession No. ML012640496).

In its approval, the NRC staff concluded the PNPP RI-ISI Program was consistent with EPRI TR-11267, and was an acceptable alternative to the requirements of ASME Code,Section XI, for RI-ISI of ASME Class 1 piping, examination categories 8-F and 8-J. The proposed PNPP RI-ISI Program, with updates, provides a 63-percent reduction in required examinations compared to ASME Code,Section XI.

3.1.5 Licensee's and 8asis for Use The PNPP RI-ISI Program was developed in accordance with the methodology contained in EPRI TR-112657 and was approved for use at PNPP during the second and third 10-year RI-ISI intervals. The PNPP RHSI Program has been updated, consistent with the intent of Nuclear Energy Institute (NEI) 04-05, "Living Program Guidance to Maintain Risk-Informed Inservice Inspections Programs for Nuclear Plant Piping Systems," (dated April 2004) and continues to meet EPRI TR-112657 and RG 1.174 risk acceptance criteria. The PNPP RI-ISI Program

-4 update incorporated new input information such as plant modifications and changes to the probabilistic risk assessment (PRA) model.

Based on the PRA model, the consequence ranking changed. The PNPP RI-ISI Program update increased the consequence rankings for certain piping segments in the following systems, from a medium consequence rank to a high consequence rank: reactor pressure vessel (RPV) nozzles and connections, nuclear boiler - main steam reactor recirculation, residual heat removal (RHR), reactor core isolation cooling (RCIC), reactor water cleanup, and feedwater. The impact of this change is reflected in the additional number of inspections locations in the proposed PI\IPP RI-ISI interval compared to the previous intervals.

The PNPP PRA model was formally reviewed in 1997, and has since undergone multiple assessments. The most recent assessment, performed in 2008, used the ASME RA-Sb-2005 PRA Standard. The PRA model meets Capability Category II for all supporting requirements regarding Level 1 internal events only with the exception of internal flooding, and is compliant with RG 1.200, Revision 1. The current PNPP PRA model of record is PRA-PY1-FP-RO, and has a core damage frequency (CDF) value of 4.29E-6.

The PRA model does not include large early release frequency (LERF), internal flooding, fire, seismic, or external events. The licensee's review of the RI-ISI risk impact results identifies that even if a conditional large early release probability (CLERP) was existing, given-core damage probability of 1.0 which would bound any impact, the risk acceptance criteria in EPRI TR-112657 would still be met.

In EPRI TR-1021467, "Nondestructive Evaluation: Probabilistic Risk Assessment Technical Adequacy Guidance for Risk-Informed In-Service Inspection Programs," dated July 8, 2010 (ADAMS Accession No. ML101930535), Section 2.2, provides justification for RI-ISI programs supporting analyses based only on internal event PRA, while excluding other hazard groups.

3.1.6 NRC Staff Evaluation 3.1.6.1 Engineering Analysis The NRC staff has reviewed and evaluated the licensee's proposed RI-ISI program, including those portions related to the applicable methodology and processes, based on guidance and acceptance guidelines provided in RGs 1.174 and 1.178, Standard Review Plan (SRP) 3.9.8, and EPRI-TR-112657, Revision B-A. An acceptable RI-ISI program plan (as stated below) is expected to meet the five key principles discussed in RGs 1.174 and 1.178, SRP 3.9.8, and EPRI TR-112657:

1. The proposed change meets the current regulations unless it is explicitly related to a requested exemption or rule change.
2. The proposed change is consistent with the defense-in-depth philosophy.
3. The proposed change maintains sufficient safety margins.
4. When the proposed change results in an increase in CDF and/or LERF, the increases should be small and consistent with the intent of the Commission's Safety Goal Policy Statement, and.

-5

5. The impact of the proposed changes should be monitored by using performance measurement strategies.

The NRC staff has determined that the first principle was met in this relief request because an alternative RI-ISI program may be authorized pursuant to 10 CFR 50.55a(3)(i) and therefore, an exemption request is not required.

The second and third principles require assurance that the alternative RI-ISI program is consistent with the defense-in-depth philosophy and that sufficient safety margins are maintained, respectively. The methodology used to develop PNPP's third 10-year RHSI program interval is unchanged from the methodology approved for use for the second 10-year RI-ISI interval program. Assurance that the second and third principles are met is based on the application of the approved methodology and not on the particular inspection locations selected.

The licensee stated that the augmented inspection program for high-energy break exclusion region piping is not affected by the RI-ISI program for the third 1O-year interval. Therefore, the second and third principles have been met The fourth principle requires an estimate of the change in risk between the proposed RI-ISI program and the program the licensee would otherwise be required to implement. The topical report (EPRI TR-112657) requires that a change in risk measurement must consider the discontinuance of ASME Code required inspections, as well as any new inspections resulting from the application of its methodology. This principle is discussed further in Section 3.1.6.2 of this safety evaluation (SE).

The fifth principle of risk-informed decision-making, requires that the impact of the proposed change be monitored by using performance measurement strategies. The RI-ISI program is a living program and, as such, is subject to periodic reviews. The licensee has indicated that, to satisfy the periodic review requirements, an evaluation and update was performed in accordance with the NEI 04-05 on an ASME period-basis as required by the initial submittal. These periodic reviews have resulted in changes in consequence rankings and the addition/deletion of welds based on plant modifications. In particular, based on the PRA model, the PNPP RI-ISI program update increased the consequence ranking for certain pipe segments, which resulted in additional examinations being added for the new RI-ISI interval compared to the previous interval. Thus, the NRC staff finds that the periodic reviews of the RI-ISI program provides assurance that the fifth key principles have been met.

Based on the above discussions and the PRA-related discussion below, the NRC staff concludes that the five key principles of risk-informed decision-making have been met and, therefore, the proposed program provides reasonable assurance that PNPP's third 1O-year RI lSI interval is acceptable.

3.1.6.2 Probabilistic Risk Assessment The PNPP RI-ISI program for the examination of ASME Class I piping is in accordance with a risk-informed process that was approved by the NRC staff in a letter dated October 17, 2001 (ADAMS Accession No. ML012640496). This request for an alternative to the current requirements for the third 10-year interval for PNPP uses the same methodology previously approved for the second 1O-year interval.

-6 Several assessments of technical capability were made to the PNPP PRA model. An independent PRA peer review was conducted in 1997 under the auspices of the Boiling Water Reactor Owners Group. In 2008, a gap analysis was performed against the ASME PRA Standard and RG 1.200, Revision 1. The PNPP PRA model does not include LERF, internal flood, fire, seismic, or external events.

PNPP used the RI-ISI methodology defined in EPRI-TR-112657 to produce altemative RI-ISI requirements. Risk significance information was used during the development of the RI-ISI program to support consequence assessment, risk ranking, and delta risk evaluation.

The NRC staff recognizes that the EPRI methodology uses the quantitative results of the PRA as order-of-magnitude estimates for several risk and reliability parameters and to support the assignment of segments into three broad consequence categories. Minor errors or inappropriate assumptions could potentially affect only the consequence categorization of a few segments and would not invalidate the general results or conclusions. Therefore, the NRC staff finds: (1) the licensee has assessed the technical adequacy of its PRA using the appropriate version of RG 1.200, and (2) the quality of the PRA is sufficient to support the proposed RI-ISI program.

Based on the results of the PRA model, these systems went from a medium consequence rank to a high consequence rank: RPV nozzles and connections, nuclear boiler - main steam reactor recirculation, RHR, RCIC, reactor water cleanup, and feedwater. Seventeen segments were added to the PNPP RI-ISI program. These changes are a result of the reclassification of pipe segments based on the revised segment failure probabilities, updated test interval, and/or revised consequences using the PNPP PRA model.

The exclusion of internal fire, seismic, high winds/external floods, and other external hazards from the RI-ISI program was based on Section 2.2 of EPRI TR-102147, as approved in the NRC SE dated September 30, 2011 (ADAMS Accession No. ML11262A206). This TR provides justification for the RI-ISI program to have supporting analyses based on the internal events PRAonly.

A change in risk evaluation was performed using the updated segment categorization discussed above to compare the original Section XI program with the revised third 10-year interval RI-ISI program for PNPP. Five nuclear boiler- main steam system segments, one reactor recirculation system segment, one RHR system segment, and ten feedwater system segments (17 total segments) were added to the PNPP RI-ISI program based on the PRA model. In response to a NRC staff request for additional information, the licensee showed that the total risk, even with the bounding case of CLERP set equal to 1.0 (that is, all core damage events lead to a large early release), LERF is equal to the CDF. Ttherefore, the third 10-year interval RI-ISI program for PNPP continues to remain lower than ASME Section XI requirements with probability of detection (POD) credited and is well within the risk acceptance guidelines even without crediting POD. In a follow up phone call with FENOC, they committed to keeping the current simplified LERF approach as the methodology for the third 1O-year RI-ISI interval.

In a supplemental letter, dated October 4, 2012 (ADAMS Accession No. ML12279A118), the licensee provided the following Regulatory Commitment related to the implementation of the

-7 proposed LERF model to the licensee's third 1O-year RI-ISI program interval, which is due by December 30,2012:

FENOC will add a statement to the inservice inspection program plan (ISEP) to state that the number of inspections related to the RI-ISI [risk-informed inservice inspection] alternative request cannot be reduced during the interval based on the PRA [probabilistic risk assessment] LERF [large early release frequency] results from the new model.

The above commitment ensures use of the LEF model, as stated in the proposed alternative request, for the third 10-year RI-ISI interval.

Based on the use of the approved methodology and on the reported results, the NRC staff finds that any change in risk associated with the implementation of the RI-ISI program will be small and consistent with the intent of the Commission's Policy Statement, and RG 1.178.

Based on the above discussions, the NRC staff concludes that the five key principles of risk informed decision-making have been met, and therefore the licensee's proposed third 10-year RI-ISI proposed program provides reasonable assurance that PNPP's third 1O-year RI-ISI internal is acceptable.

4,0 CONCLUSIONS As set forth above, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a, and the proposed alternative provides an acceptable level of quality and safety, Therefore, the NRC staff authorizes continued use of the RI-/SI Program at PNPP for the third 1O-year RI-ISI interval, including the licensee's commitment concerning LERF as described in Section 3,1,6.2 of this SE.

The NRC staff also concludes that the licensee has adequately addressed all of the regulatory requirements set forth in and 10 CFR 50.55a(a)(3)(i), and is in compliance with the requirements of 10 CFR 50.55a with the authorizing of the alternative contained in IR-049, Revision 1, for PNPP, Therefore, the NRC staff authorizes the licensee's proposed alternative contained in IR-049, Revision 1, for the third 10-year RI-ISI interval at PNPP, which expires on May 17, 2019.

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

Principal Contributor: J, Evans and K. Hoffman, NRR Date of issuance: November 14, 2012

Mr. Vito A. Kaminskas Site Vice President FirstEnergy Nuclear Operating Company Mail Stop A-PY -A290 P.O Box 97,10 Center Road Perry,OH 44081-0097

SUBJECT:

PERRY NUCLEAR POWER PLANT, UNIT 1 - SAFETY EVALUATION IN SUPPORT OF 10 CFR 50.55A REQUESTS FOR ALTERNATIVE EXAMINATION REQUIREMENTS FOR AMERICAN SOCIETY OF MECHNICAL ENGINEERS, CLASS 1, PIPING WELDS (TAC NO. ME7564)

By letter to the U.S. Nuclear Regulatory Commission (NRC), dated November 14,2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML113180450), as supplemented by letters dated August 10, 2012, and October 4, 2012 (ADAMS Accession Nos. ML12226A244 and ML12279A118, respectively), FirstEnergy Nuclear Operating Company (the licensee) requested approval for continued use of the existing Perry Nuclear Power Plant (PPNP), Unit No.1, risk-informed inservice inspection (RI-ISI) program, with updates, relative to certain non-destructive examination requirements associated with the American Society of Mechanical Engineers, Class 1, piping welds. The proposed alternative is designated by the licensee as IR-049, Revision 1. The proposed alternative will be implemented during the PNPP third 1O-year RI-ISI interval, currently scheduled to expire on May 17,2019.

Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in Title 10 of the Code of Federal Regulations (CFR), Section 50.55a(a)(3)(i), and is in compliance with the requirements of 10 CFR 50.55a with the authorizing of this alternative contained in IR-049, Revision 1. Therefore, the NRC staff authorizes the licensee's proposed alternative contained in IR-049, Revision 1. The NRC staff's safety evaluation is enclosed.

Please contact the PNNP Project Manager, Michael Mahoney at (301) 415-3867 if you have any questions regarding this action.

Sincerely, IRAI Michael I. Dudek, Chief Plant Licensing Branch 111-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-440

Enclosure:

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

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