2CAN112105, Response to Request for Additional Information Concerning Relief Request ANO2-RR-21-002 Support the Repair of the Reactor Vessel Closure Head Penetration 46

Response to Request for Additional Information Concerning Relief Request ANO2-RR-21-002 Support the Repair of the Reactor Vessel Closure Head Penetration 46

ML21312A017
Person / Time
Site:	Arkansas Nuclear
Issue date:	11/07/2021
From:	Gaston R Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
2CAN112105
Download: ML21312A017 (7)

Text

Entergy Operations, Inc.

1340 Echelon Parkway Jackson, MS 39213 Tel 601-368-5138 Ron Gaston Director, Nuclear Licensing 10 CFR 50.55a(z)(1) 2CAN112105 November 7, 2021 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Response to Request for Additional Information Concerning Relief Request ANO2-RR-21-002 Support the Repair of the Reactor Vessel Closure Head Penetration #46 Arkansas Nuclear One, Unit 2 NRC Docket No. 50-368 Renewed Facility Operating License No. NPF-6 Entergy Operations, Inc. (Entergy) submitted Relief Request ANO2-RR-21-002 for Arkansas Nuclear One, Unit 2 (ANO-2) via Reference 1. A flaw located in the Reactor Vessel Closure Head (RVCH), Penetration #46 was determined to be unacceptable based on requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code).

In Reference 1, Entergy proposed an alternative to the ASME Code repair/replacement requirements as a repair to the ANO-2 RVCH.

The U.S. Nuclear Regulatory Commission (NRC) staff has determined that additional information is needed to complete its review (Reference 2). The requested information is provided in response to this request in the Enclosure.

There are no new regulatory commitments established in this submittal.

2CAN112105 Page 2 of 2 If there are any questions or if additional information is needed, please contact Riley Keele, Manager, Regulatory Assurance, Arkansas Nuclear One, at 479-858-7826.

Respectfully, Ronald W. Digitally signed by Ronald W. Gaston Gaston Date: 2021.11.07 17:03:49 -06'00' Ron Gaston RWG/rwc References

1. Entergy Operations, Inc. (Entergy) letter to the U. S. Nuclear Regulatory Commission (NRC), "Relief Request ANO2-RR-21-002 Half-Nozzle Repair of Reactor Vessel Closure Head Penetration #46," (2CAN112103), ML21309A007, dated November 5, 2021.

2. T. Wengert (NRC email to R. D. Keele, Jr. (Entergy), " RE: ANO-2 Draft RAI RE: Relief Request ANO2-RR-21-002 (EPD L-2021-LLR-0084)," (2CNA112101) dated November 5, 2021.

Enclosure:

Response to Request for Additional Information Related to Relief Request ANO2-RR-21-002 cc: NRC Region IV Regional Administrator NRC Senior Resident Inspector - Arkansas Nuclear One NRC Project Manager - Arkansas Nuclear One Designated Arkansas State Official

Enclosure 2CAN112105 Response to Request for Additional Information Related to Relief Request ANO2-RR-21-002

2CAN112105 Enclosure Page 1 of 4 RESPONSE TO REQUEST FOR ADDITTIONAL INFORMATION RELATED TO RELIEF REQUEST ANO2-RR-21-002 By letter dated November 5, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21309A007), Entergy Operations, Inc. (the licensee) requested approval to allow the conduct of half-nozzle repair of reactor vessel closure head (RVCH)

Nozzle #46 at Arkansas Nuclear One, Unit 2 (ANO-2). The proposed alternative is requested in accordance with Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55(z)(1) based on the licensees determination that the alternative provides the acceptable level of quality and safety. To complete its review, the U.S. Nuclear Regulatory Commission (NRC or the Commission) staff requests supplemental information as follows:

Regulatory Basis The inservice inspection (ISI) of the American Society of Mechanical Engineers Boiler and Pressure Vessel (ASME) Code,Section XI, Class 1, 2 and 3 components shall be performed in accordance with the requirements of Section XI, Rules for In-service Inspection of Nuclear Power Plant Components, of the ASME Code and applicable editions and addenda as required by 10 CFR 50.55a(g), except where specific written relief has been granted or proposed alternative authorized by the Commission. In order to assess the licensees proposed alternative, the NRC staff requires the following additional information to complete its review.

Request for Additional Information (RAI)

RAI-1

The NRC staff notes that the volumetric inspection area above the weld, for both the Post-Weld UT and Inservice Inspection UT, is not consistent with the area defined by Figure 2 of ASME Code Case N-729-6, Alternative Examination Requirements for PWR [Pressurized Water Reactor] Reactor Vessel Upper Heads with Nozzles Having Pressure-Retaining Partial-Penetration Welds. The dimension a, defining examination above the weld, is based on the incident angle of the weld. The new reactor coolant pressure boundary weld has an incident angle of 0 degrees and therefore, the a dimension should be 1.5-inch.

Provide additional basis for the licensees proposed Post-Weld UT and Inservice Inspection UT areas defined by Figures 3 and 9 to address the deviation from Figure 2 of ASME Code Case N-729-6.

Entergy's Response Post-Weld Ultrasonic Testing (UT)

The basis for the Post-Weld UT examination volume is provided in Section 5.2 and shown on Figure 3 of the submittal. The Post-Weld UT is performed in accordance with ASME Section III as required by ASME Case N-638-7 as described in Section 5.2 of the submittal. Figure 3 is not

2CAN112105 Enclosure Page 2 of 4 intended to apply to the Preservice Inspection / Inservice Inspection (PSI/ISI) requirements of Code Case N-729-6.

Preliminary coverage assessments depict the weld is expected to receive 100% coverage and is evaluated against the acceptance criteria of ASME Section III, NB-5330. Additionally, approximately 0.25 inch of the low alloy steel material along the weld-to-low alloy steel fusion line is examined for lack of fusion and under bead cracking.

While not required by ASME Section III, the examination volume is expanded to include 1 inch of the Alloy 600 nozzle base material and 1 inch of the Alloy 690 nozzle base material directly adjacent to (above and below) the weld.

Therefore, ASME Section III UT examination requirements are satisfied.

PSI/ISI UT The basis for the proposed PSI/ISI UT examination is defined in Section 5.5 of the relief request and the revised Figure 9 included in this submittal to better align with the description provided in Section 5.5 of the relief request:

The examination volume also includes the rotary peened surfaces. Successive examinations required by Code Case N-729-6 will be performed on CEDM Nozzle 46 during each subsequent refueling outage.

ASME Case N-729-6 requires the examination region to extend 1.5 inch beyond partial penetration welds with an incidence angle of 0 degrees with the penetration axis. In lieu of the volumetric examination region that extends 1.5 inch above and 1.5 inch below the J-groove weld shown in Figure 2 of Case N-729-6, an alternative examination region is proposed for the repair weld. The proposed examination volume will extend up to the outer surface of the head (greater than 1.5 inch above the repair weld), including the rotary peened surfaces, and 1 inch below the repair weld as shown in revised Figure 9.

The examination coverage below the weld will be less than the 1.5 inch requirement due to geometric limitations, however the coverage will extend a minimum of 1 inch below the weld and will obtain the maximum volume practical. Examination coverage of 1 inch below the repair weld is considered sufficient due to the following:

• The replacement nozzle material (Alloy 690) is resistant to primary water stress corrosion cracking (PWSCC).

• The new pressure boundary weld (Alloy 52M) is resistant to PWSCC.

• The replacement nozzle is non-pressure boundary material

• Preliminary coverage assessments, based on the revised Figure 9, provided below, depict the examination volume is expected to receive essentially 100% examination coverage.

2CAN112105 Enclosure Page 3 of 4 Therefore, the PSI/ISI assessment, based on the revised Figure 9 includes the weld and adjacent nozzle material to the extent shown in the revised Figure 9. The volume is consistent with the technical basis for Figure 2 of Code Case N-729-6.

2CAN112105 Enclosure Page 4 of 4 Figure 9 Nozzle PSI / ISI UT Examination (Revised)

UT a-b-c-d-a UT e-c (leak path)