2CAN102102, Relief Request ANO2-R&R-012: Support the Repair of the Reactor Vessel Closure Head Penetration 46

Relief Request ANO2-R&R-012: Support the Repair of the Reactor Vessel Closure Head Penetration 46

ML21283A001
Person / Time
Site:	Arkansas Nuclear
Issue date:	10/10/2021
From:	Gaston R Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML21283A000	List: 2CAN102102, Relief Request ANO2-R&R-012: Support the Repair of the Reactor Vessel Closure Head Penetration 46
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2CAN102102
Download: ML21283A001 (28)

Text

This letter contains proprietary information.

Withhold Enclosure 1 from public disclosure in accordance with 10 CFR 2.390.

Entergy Operations, Inc.

1340 Echelon Parkway Jackson, MS 39213 Tel 601-368-5138 Ron Gaston Director, Nuclear Licensing 10 CFR 50.55a(z)(1) 2CAN102102 October 10, 2021 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Relief Request ANO2-R&R-012 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 On October 4, 2021, Arkansas Nuclear One, Unit 2 (ANO-2) completed the analysis on an indication revealed on Penetration #46. ANO-2 was required to perform ultrasonic examinations of the Reactor Vessel Closure Head partial penetration welds during the current refueling outage (2R28) in compliance with 10 CFR 50.55a and the approved ANO-2's relief request ANO2-ISI-022. A flaw located in the nozzle was determined to be unacceptable based on American Society of Mechanical Engineers (ASME) code requirements. A strategy to perform a local excavation of the weld to remove the indication has been developed in order to affect a repair of this nozzle.

Defect evaluation requirements are specified in IWA-4422.1(a) and (b) of the ASME Section XI Code. One alternative is removal of the defect area and any remaining portion of the defect may be evaluated and the component accepted in accordance with the appropriate flaw evaluation design provisions of the Owners Requirements and either the Construction Code or Section.

The strategy to remove this indication that Entergy Operations, Inc. (Entergy) elected requires a proposed alternative to the requirements of ASME Section III, N-462.4(d), Figure N-462.4(d)

Attachment of Connections Using Partial Penetration Welds pursuant to 10 CFR 50.55a(z)(1).

This letter contains proprietary information.

Withhold Enclosure 1 from public disclosure in accordance with 10 CFR 2.390.

This letter contains proprietary information.

Withhold Enclosure 1 from public disclosure in accordance with 10 CFR 2.390.

2CAN102102 Page 2 of 3 In accordance with 10 CFR 50.55a(z)(1), proposed alternatives may be approved by the NRC, provided an acceptable level of quality and safety are maintained. Entergy requests approval of the proposed alternative in order to support the return of ANO-2 to service from the current refueling outage.

This relief request is required to address an emergent condition at ANO-2. Entergy requests NRC approval as soon as possible but no later than October 12, 2021, at 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br />. This schedule is subject to fluctuation. Relief is requested for one operating cycle.

Some information provided in Enclosure 1 (from LTR-SDA-21-074) is considered proprietary to Westinghouse Electric Company and is to be withheld from public disclosure in accordance with 10 CFR 2.390 of the Commissions regulations. The proprietary information is identified by text enclosed within double brackets ((Example)). The non-proprietary version is provided in .

This information is supported by an affidavit, signed by Westinghouse Electric Company, the owner of the information. The affidavit sets forth the bases by which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)(4) of 10 CFR 2.390 of the Commission's regulations. The affidavit is included in Enclosure 3.

There are new regulatory commitments established in this submittal. They are summarized in the attachment to the enclosure.

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: 2021.10.10 18:04:53 -05'00' Ron Gaston RWG/rwc

Enclosure:

1. Relief Request ANO2-R&R-012 (PROPRIETARY)

Attachment to Enclosure 1 Commitment

2. Relief Request ANO2-R&R-012 (NON-PROPRIETARY)

3. Affidavit This letter contains proprietary information.

Withhold Enclosure 1 from public disclosure in accordance with 10 CFR 2.390.

This letter contains proprietary information.

Withhold Enclosure 1 from public disclosure in accordance with 10 CFR 2.390.

2CAN102102 Page 3 of 3 cc: NRC Region IV Regional Administrator NRC Senior Resident Inspector - Arkansas Nuclear One NRC Project Manager - Arkansas Nuclear One Designated Arkansas State Official This letter contains proprietary information.

Withhold Enclosure 1 from public disclosure in accordance with 10 CFR 2.390.

, Attachment 2CAN102102 Commitments

2CAN102102 Enclosure 1, Attachment Page 1 of 1 This table identifies actions discussed in this letter for which Entergy commits to perform. Any other actions discussed in this submittal are described for the NRCs information and are not commitments.

TYPE SCHEDULED COMMITMENT (Check one) COMPLETION DATE (If Required)

ONE-TIME CONTINUING ACTION COMPLIANCE Entergy will perform a fatigue analysis to X Prior to 2R29 (Spring address local effects at the excavation 2023) due to expansion and contraction of the head for cyclic pressure and thermal transients to support long term operation.

Entergy will submit a revised relief X To support ANO's request based on the revised fatigue return to service analysis. following 2R29.

After the final PT of the excavation, X October 14, 2021 emery cloth buffing will be performed to the ground surface to remove possible cold working. After emery cloth buffing an ultrasonic examination of the excavated area is required to demonstrate the flaw indication has been removed. If not, Entergy will continue to excavate until the limits described above are reached or a successful PT is achieved prior to reaching the limits.

Enclosure 2 2CAN102102 Relief Request ANO2-R&R-012 NON-PROPRIETARY

2CAN102102 Page 1 of 17 RELIEF REQUEST ANO2-R&R-012

1. ASME Code Component Affected:

Component: Reactor Vessel Closure Head (RVCH) Penetration #46 Code Class: 1 Exam. Cat.: ASME Code Case N-729-6 Item No.: B4.10 and B4.20 Unit: Arkansas Nuclear One, Unit 2 (ANO-2)

Interval: Fifth (5th)

2. Application Code Edition and Addenda:

ASME Section III, 1968 Edition with Addenda through Summer 1970 ASME Section III 1992 Edition ASME Section XI, 2007 Edition with the 2008 Addenda

3. Applicable Code Requirement

Defect evaluation requirements are specified in IWA-4422.1(a) and (b) of the ASME Section XI Code which states:

(c) A defect is considered removed when it has been reduced to an acceptable size. If the resulting section thickness is less than the minimum required thickness, the component shall be corrected by repair/replacement activities.

(d) Alternatively, the defect removal area and any remaining portion of the defect may be evaluated and the component accepted in accordance with the appropriate flaw evaluation provisions of Section XI, or the design provisions of the Owners Requirements and either the Construction Code or Section III.

Design requirements for partial penetration groove welds are specified in Section N-462.4(d)(1) of the ASME Section III code.

2CAN102102 Page 2 of 17 Partial penetrations attachments used to connect nozzles necks as permitted in N-457(c) shall be groove welds having a minimum depth equal to 1 1/4 times the nominal thickness nozzle neck. These welds shall be inspected progressively at the lesser of one-third of the thickness of the weld joint or each 1/2 in. of thickness by a magnetic particle method in accordance with N-626 or by a liquid penetrant method in accordance with N-627. Acceptable types are shown in Fig. N-462.4(d).

Based on Figure N-462.4(d)(3) of the Reference 1, the total weld throat shall be 1.5tn while the throat dimension of the partial penetration weld shall be 0.75tn.

4. Reason for Request

ANO-2 is currently in a refueling outage. As part of the examination of the Reactor Vessel Closure Head (RVCH) required by ASME Code Case N-729-6, the inside diameter of Penetration #46 was examined with ultrasonic testing (UT) and eddy current testing (ET) as approved by relief request ANO2-ISI-022. The results from the current examination were compared to the previous examination results. An UT indication was identified on the outside diameter of the nozzle that exhibited growth from the previous examination.

An outside diameter surface ET was performed to confirm the presence of a surface indication. An outside diameter surface dye penetrant test (PT) in the area of the UT indication confirmed a surface breaking indication. The indication was shown to extend into the J-groove weld fillet cap on the outside surface of the nozzle.

Figures 1 and 2 are pictures of the PT indication.

A strategy to perform a local excavation of the weld to remove the indication has been developed in order to affect a repair of this nozzle.

The UT report is the basis for the determination of the allowable excavation area. Figure 3 summarizes the UT key data and critical dimensions based on ASME Code J-groove weld requirements listed in ASME Section III, N-462.4(d). The figure characterizes the dimensions and location of the indication relative to the dimensions and location of the J-groove weld. The following points are demonstrated by Figure 7:

1. The total measured weld length derived by the difference of L3 and L4 is 1.04 inch, which is only 0.041 inch larger than the minimum weld depth of 0.999 inch based on the 1.5tn requirements of Reference 1 where tn is the nominal nozzle thickness of 0.666 inch (Reference 2).

2. The top of the indication, as shown by L2 in Figure 7, is above the bottom of the weld, indicated by L3, whereby the indication extends into the weld by the difference of L2 and L3, or 0.28 inch.

2CAN102102 Page 3 of 17 These findings indicate that any excavation of the weld to remove the indication will locally reduce the weld height below the 1.5tn requirement of Reference 1. As a result, the repair excavation will not comply with Fig. N-462.4(d)(3) of the ASME Section III Code.

5. Proposed Alternative and Basis for Use

Entergy intends to repair Penetration #46 by removing the identified defect using a mechanical metal removal process (e.g., machining) in accordance with IWA-4422.1 and IWA-4462. In performing this repair, the resultant excavation in the partial penetration J-groove weld will encroach upon the 1.5tn throat dimension of Fig. N-462.4(d)(3) of Reference 1. Pursuant to 10 CFR 50.55a(z)(1), Entergy proposes to perform an engineering evaluation to demonstrate the acceptability of the J-groove weld in lieu of implementing the design evaluation provisions of IWA-4422.1.

Basis for Use:

The ANO-2 RVCH was built to ASME Section III requirements.

The first qualified RVCH CEDM nozzle tube UT examination was performed in 2R20 Entergy proposes to remove the identified defect in Penetration #46 by performing defect removal without welding in accordance with IWA-4422.2.1. However, as explained above, the excavation following defect removal will encroach into the weld region of the J-groove weld by at least 0.28 inch. This results in a reduction of the throat thickness in a small portion of the J-groove weld to less than the 1.5tn dimension of Fig. N-462.4(d)(3) of Reference 1. Entergy has determined that this loss of throat thickness in a localized region of the J-groove weld will not have any adverse impact on the structural integrity of the J-groove weld as demonstrated below.

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Part 3: Other Considerations The defect in Penetration #46 will be removed in accordance with IWA-4422.2.1. As part of this repair process, the defect removal cavity will be examined by the liquid penetrant (PT) examination method in accordance with NB-5000 of the 1992 Edition of ASME Section III.

After the final PT of the excavation, emery cloth buffing will be performed to the ground surface to aid in the removal of possible cold working. After emery cloth buffing, an ultrasonic examination of the excavated area is required to demonstrate the flaw indication has been removed.

Finally, pre-service examination of the repair in Penetration #46 will comply with ASME Code Case N-729-6 and any NRC approved alternatives to these conditions. Pre-service examinations will include both UT and PT examinations.

Conclusions

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The vendor has applied a similar strategy that has been successfully used in the following applications:

x 2003 / 2004 timeframe - removal of an indication via grinding at the tube to j-weld interface on an ICI penetration at San Onofre Nuclear Generating Station.

x 2005 / 2006 timeframe - removal of an indication via grinding at the tube to j-weld interface on an ICI penetration at ANO-2.

x 2016 - removal of an indication via grinding at the tube to j-weld interface on a control rod drive mechanism penetration 50 at Indian Point Energy Center, Unit 2.

x 2018 - removal of an indication via grinding at the tube to j-weld interface on control element drive mechanism penetration 49 at ANO-2.

None of the applications required a relief request to implement.

After the final PT of the excavation, emery cloth buffing will be performed to the ground surface to aid in the removal of possible cold working. After emery cloth buffing an ultrasonic examination of the excavated area is required to demonstrate the flaw indication has been removed. If not, Entergy will continue to excavate until the limits described above are reached or a successful PT is achieved prior to reaching the limits.

Entergy will continue to inspect the ANO-2 RVCH next refueling outage in accordance with 10 CFR 50.55a requirements.

6. Duration of Proposed Alternative

This proposed alternative is requested for one operating cycle.

7. Conclusion From 10 CFR 50.55a:

(z) Alternatives to codes and standards requirements. Alternatives to the requirements of paragraphs (b) through (h) of this section or portions thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation, or Director, Office of

2CAN102102 Page 10 of 17 New Reactors, as appropriate. A proposed alternative must be submitted and authorized prior to implementation. The applicant or licensee must demonstrate that:

(1) Acceptable level of quality and safety. The proposed alternative would provide an acceptable level of quality and safety; Entergy believes the proposed alternative provides an acceptable level of quality and safety by utilizing a technique, inspections and analysis of the ANO-2 Penetration #46 described in this request. Therefore, Entergy requests authorization to perform the proposed alternative pursuant to 10 CFR 50.55a(z)(1).

8. References

1. ASME Boiler and Pressure Vessel Code,Section III, Nuclear Vessels, 1968 Edition with Addenda through Summer 1970.

2. Combustion Engineering Drawing, E-234-760, Rev. 2, Closure Head Nozzle Details Arkansas Nuclear 157 I.D. P.W.R. Equipment No. 2R1.

3. Design Reports:

a. Combustion Engineering Analytical Report, CENC-1222, Rev. 000, Analytical Report for Arkansas Nuclear One - Unit 2 Reactor Vessel, August 1974.

b. ABB Combustion Engineering Design Report, A-MECH-DR-007, Rev. 00, Addendum to the Reactor Vessel Analytical Report for Entergy Operations, Inc.,

Arkansas Nuclear One-Unit 2, June 9, 1993.

4. Combustion Engineering Drawing, E-234-761, Rev. 3, Closure Head Penetrations Arkansas Nuclear 157 I.D. P.W.R. Equipment No. 2R1.

5. Westinghouse Letter, LTR-SDA-18-096, Rev. 0, ANO2 Reactor Vessel Head CEDM Penetration 49 Disposition of Grinding Option, October 10, 2018.

2CAN102102 Page 11 of 17 Figure 1 Initial PT Indication Upon Application of the Developer Reactor Head ID Surface CEDM 46 Initial PT Indication

2CAN102102 Page 12 of 17 Figure 2 Final PT Indication After Final Development Reactor Head ID Surface Final PT Indication CEDM 46

2CAN102102 Page 13 of 17 Figure 3 Design vs. WESDYNE Critical Dimensions

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2CAN102102 Page 14 of 17 Figure 4 ASME Section III Design By Rule Weld Sizing

2CAN102102 Page 15 of 17 Figure 5 Section View of Proposed Excavation

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2CAN102102 Page 16 of 17 Figure 6 Isometric View of Proposed Excavation

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2CAN102102 Page 17 of 17 Figure 7 Design vs. WESDYNE Critical Dimensions

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2CAN102102 Affidavit