RS-18-041, Response to Request for Additional Information Regarding Request for Relief (I4R-07) for Extension of Examination Interval for Reactor Pressure Vessel Head Penetration Nozzles with Mitigated Alloy 600/82/182 Peened ...

Response to Request for Additional Information Regarding Request for Relief (I4R-07) for Extension of Examination Interval for Reactor Pressure Vessel Head Penetration Nozzles with Mitigated Alloy 600/82/182 Peened ...

ML18102B213
Person / Time
Site:	Braidwood
Issue date:	04/12/2018
From:	Gullott D Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RS-18-041
Download: ML18102B213 (4)

Text

Exelon Generation 4300 Winfield Road Warrenville. IL 60555 www.exeloncorp.com RS-18-041 10 CFR 50.55a April 12, 2018 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Braidwood Station, Unit 2 Renewed Facility Operating License No. NPF-77 NRC Docket No. STN 50-457

Subject:

Response to Request for Additional Information Regarding Request for Relief (14R-07) for Extension of Examination Interval for Reactor Pressure Vessel Head Penetration Nozzles with Mitigated Alloy 600/82/182 Peened Surfaces in Accordance with 10 CFR 50.55a(z)(1)

References:

(1) Letter from David M. Gullatt (Exelon Generation Company, LLC) to U.S.

NRC, "Request for Relief for Extension of Examination Interval for Reactor Pressure Vessel Head Penetration Nozzles with Mitigated Alloy 600/82/182 Peened Surfaces in Accordance with 10 CFR 50.55a(z)(1)," dated December 20, 2017 (2) Electric Power Research Institute (EPRI), Materials Reliability Program:

Topical Report for Primary Water Stress Corrosion Cracking Mitigation by Surface Stress Improvement (MRP-335 Revision 3-A), EPRI Publication No. 3002009241, Final Report, dated November 2016 (3) Letter from Kevin Hsueh, (U.S. NRC) to Matthew Sunseri, (EPRI), "Final Safety Evaluation of the Electric Power Research Institute MRP-335, Revision 3, 'Materials Reliability Program.: Topical Report for Primary Water Stress Corrosion Cracking Mitigation by Surface Stress Improvement

[Peening],"' dated August 24, 2016(ML16208A485)

(4) Email from J. Wiebe (U.S. NRC) to J. A. Bauer (Exelon Generation Company, LLC), "Braidwood, Unit 1, Request for Additional Information (EPID No. L-2017-LLR-0155)," dated March 15, 2018 In Reference 1, in accordance with 10 CFR 50.55a, "Codes and standards," paragraph (z)(1),

Exelon Generation Company, LLC (EGC), requested relief from the current examination requirements of Reactor Pressure Vessel Head Penetration Nozzles (RPVHPN) performed in accordance with 10 CFR 50.55a(g)(6)(ii)(D), which specifies the use of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components," Code Case N-729-4 on the basis that the proposed alternative would provide an acceptable level of quality and safety.

U.S. Nuclear Regulatory Commission April 12, 2018 Page 2 EGC has implemented the Ultra High Pressure Cavitation Peening (UHPCP) process at Braidwood Station Unit 2; therefore, in Relief Request 14R-07 (Attachment 1 to Reference 1),

EGC requested a change to the examination interval of the follow-up inspections for peened RPVHPNs and associated welds in accordance with References 2 and 3; including relief from the Reference 3 Condition 5.4 (a) requirement for inspection in the second refueling outage after peening.

In Reference 4, the NRC notified EGC that additional information was needed to complete the NRC's evaluation of the subject relief request. The response to this request is due to the NRC on or before April 16, 2018. The requested information is provided in Attachment 1 to this letter.

As noted in Reference 1, EGC is requesting approval of the proposed alternative by December 20, 2018.

There are no regulatory commitments contained within this letter.

Should you have any questions concerning this letter, please contact Joseph A. Bauer at (630) 657-2804.

Respectfully, David M. Gullott Manager - Licensing Exelon Generation Company, LLC : Response to Request for Additional Information Regarding Request for Relief (14R-07) for Extension of Examination Interval for Reactor Pressure Vessel Head Penetration Nozzles with Mitigated Alloy 600/82/182 Peened Surfaces in Accordance with 10 CFR 50.55a(z)(1) cc: Regional Administrator - NRC Region Ill NRC Senior Resident Inspector - Braidwood Station Illinois Emergency Management Agency

ATTACHMENT 1 Response to Request for Additional Information Regarding Request for Relief (14R-07) for Extension of Examination Interval for Reactor Pressure Vessel Head Penetration Nozzles In Reference 1, in accordance with 10 CFR 50.55a, "Codes and standards," paragraph (z)(1 ),

Exelon Generation Company, LLC (EGC), requested relief from the current examination requirements of Reactor Pressure Vessel Head Penetration Nozzles (RPVHPN) performed in accordance with 10 CFR 50.55a(g)(6)(ii)(D), which specifies the use of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components," Code Case N-729-4 on the basis that the proposed alternative would provide an acceptable level of quality and safety.

EGC has implemented the Ultra High Pressure Cavitation Peening (UHPCP) process at Braidwood Station Unit 2; therefore, in Relief Request 14R-07 (Attachment 1 to Reference 1),

EGC requested a change to the examination interval of the follow-up inspections for peened RPVHPNs and associated welds in accordance with References 2 and 3; including relief from the Reference 3 Condition 5.4 (a) requirement for inspection in the second refueling outage after peening.

In Reference 4, the NRC notified EGC that additional information was needed to complete the NRC's evaluation of the subject relief request. The requested information is provided below.

NRC Request for Additional Information By letter dated June 15, 2017 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML17360A173), Exelon Generation Company, LLC (Exelon, the licensee), submitted a request to the U.S. Nuclear Regulatory Commission (NRG or Commission) for the use of alternatives to certain requirements of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code),Section XI, at Braidwood Station (Braidwood), Unit 2.

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

Exelon submitted relief request 14R-07 to perform alternate examinations of peened reactor pressure vessel head penetration nozzles (RPVHPNs) and associated partial penetration J-groove attachment welds on the basis that the proposed alternative provides an acceptable level of quality and safety.

Relief Request, Page 5 of 21, under the heading Pre-Peening Baseline Inspection, Exelon discusses the examinations performed prior to peening. Under the heading, Follow-up Inspection, Exelon states that Re-inspection Year (RIY) is equal to 1.62 at the time of peening or end of cycle 19. Exelon also stated that based on Code Case N-729-4, Table 1, Item B4.20, a maximum volumetric re-examination frequency should be every 8 calendar years or before RIY equals 2. 25 for Braidwood Unit 2 nozzles. Exelon concludes that, since the reactor pressure vessel RIY is less than 2. 25 (RIY = 1. 62 at the time of peening or end of Cycle 19 for Braidwood Station Unit 2), a follow-up volumetric inspection in N+4 is acceptable. Code Case N-729-4, 2410, "Inspection Program," shows that the RIY calculation begins from the time of the most recent volumetric or surface examination.

ATTACHMENT 1 Response to Request for Additional Information Regarding Request for Relief (14R-07) for Extension of Examination Interval for Reactor Pressure Vessel Head Penetration Nozzles To complete its evaluation, the NRG staff requests the following information:

Since it appears that the RIY of 1. 62 would be reset by the examinations performed prior to peening, confirm whether the projected RIY at the proposed follow-up inspection at the N + 4 refueling outage (N is the refueling outage when peening was applied) is less than 2. 25.

Response

As noted in the NRC Request for Additional Information, in Reference 1, Attachment 1, page 5 of 21, EGC stated that the RIY = 1.62 at the time of peening or end of Cycle 19 for Braidwood Station Unit 2. This RIYvalue was calculated using the equation in Code Case N-729-1 (at the time of peening) with actual data inputs for Braidwood Station Unit 2 through Cycle 19. Using this same equation beginning at the time of the most recent volumetric examination (i.e., prior to the start of Cycle 20), the projected RIY for Cycle 20 through the end of Cycle 23 (i.e., 4 cycles later) was calculated to be 1.84. This value satisfies the Code Case N-729-4, Table 1, Item B4.20 requirement (see Reference 5) which specifies a maximum volumetric re-examination frequency of "every 8 calendar years or before RIY = 2.25." Since the reactor pressure vessel RIY is less than 2.25 through the end of Cycle 23, a follow-up volumetric inspection in the N+4 refueling outage is supported.

REFERENCES

1. Letter from David M. Gullatt (Exelon Generation Company, LLC) to U.S. NRC, "Request for Relief for Extension of Examination Interval for Reactor Pressure Vessel Head Penetration Nozzles with Mitigated Alloy 600/82/182 Peened Surfaces in Accordance with 10 CFR 50.55a(z)(1)," dated December 20, 2017

2. Electric Power Research Institute (EPRI), Materials Reliability Program: Topical Report for Primary Water Stress Corrosion Cracking Mitigation by Surface Stress Improvement (MRP-335 Revision 3-A), EPRI Publication No. 3002009241, Final Report, dated November 2016

3. Letter from Kevin Hsueh, (U.S. NRC) to Matthew Sunseri, (EPRI), "Final Safety Evaluation of the Electric Power Research Institute MRP-335, Revision 3, 'Materials Reliability Program: Topical Report for Primary Water Stress Corrosion Cracking Mitigation by Surface Stress Improvement [Peening],"' dated August 24, 2016 (ML16208A485)

4. Email from J. Wiebe (U.S. NRC) to J. A. Bauer (Exelon Generation Company, LLC),

"Braidwood, Unit 1, Request for Additional Information (EPID No. L-2017-LLR-0155),"

March 15, 2018

5. ASME Code Case N-729-4, "Alternative Examination Requirements for PWR Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds,Section XI, Division 1," approved June 22, 2012.