ML21123A141

COL Docs - FW: VEGP Unit 3 ASME Code Alternative for Containment Vessel Repair ALT-16 Presubmittal Meeting April 29, 2021

ML21123A141
Person / Time
Site:	Vogtle
Issue date:	05/03/2021
From:	NRC
To:	NRC/NRR/DNRL
References
Download: ML21123A141 (13)

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From: Gleaves, Billy Sent: Monday, May 3, 2021 12:08 PM To: Vogtle PEmails Cc: Gleaves, Billy

Subject:

FW: VEGP Unit 3 ASME Code Alternative for Containment Vessel Repair ALT-16 Presubmittal Meeting April 29, 2021 Attachments: NRC Pre-Submittal Presentation - ALT-16.pdf This email is being forwarded to capture the SNC email transmitting the April 29, 2021 meeting presentation slides, and the slides themselves.

Billy William (Billy) Gleaves Senior Project Manager NRR/Vogtle Project Office US Nuclear Regulatory Commission From: Chapman, Nathan B. <NBCHAPMA@SOUTHERNCO.COM>

Sent: Friday, April 30, 2021 7:11 AM To: Gleaves, Billy <Bill.Gleaves@nrc.gov>

Cc: Kellenberger, Nicholas <X2NRKELL@SOUTHERNCO.COM>

Subject:

[External_Sender] ALT-16 Presubmittal Presentation Mr. Gleaves:

Please find the attached slides presented by SNC during the Thursday (4/29) public call.

Thanks, Nathan B. Chapman Licensing Engineer Southern Nuclear / Vogtle 3&4 Site Licensing Office: 706.848.5816 / nbchapma@southernco.com

Hearing Identifier: Vogtle_COL_Docs_Public Email Number: 609 Mail Envelope Properties (DM6PR09MB48391B48F91251D725A358079F5B9)

Subject:

FW: VEGP Unit 3 ASME Code Alternative for Containment Vessel Repair ALT-16 Presubmittal Meeting April 29, 2021 Sent Date: 5/3/2021 12:07:35 PM Received Date: 5/3/2021 12:07:42 PM From: Gleaves, Billy Created By: Bill.Gleaves@nrc.gov Recipients:

"Gleaves, Billy" <Bill.Gleaves@nrc.gov>

Tracking Status: None "Vogtle PEmails" <Vogtle.PEmails@usnrc.onmicrosoft.com>

Tracking Status: None Post Office: DM6PR09MB4839.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 857 5/3/2021 12:07:42 PM NRC Pre-Submittal Presentation - ALT-16.pdf 444325 Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Remediation for Unit 3 Containment Vessel Unistrut Welding ASME Section III Code Alternative Request VEGP 3-ALT-16 April 29, 2021

Overview

• Background

• Alternative Request Overview

• Fracture Toughness Requirements

• Material Compatibility

• Summary 2

=

Background===

• The Unit 3 Containment Vessel (CV) is an ASME Section III, Class MC pressure vessel

• Subsequent to completion of design and construction of Unit 3 CV, and after the Structural Integrity Test (SIT) was successfully completed:

- 6 pieces of Unistrut were welded to the CV inside diameter across 3 locations using 4 long, 1/4 to 3/8 fillet welds

- Welding was performed by a contractor that is not an N-Certificate holder 3

Alternative Request

• The proposed alternative requests authorization to perform remediation of Unistrut welding

• Remediation would be performed by the CV N-Certificate Holder, CB&I, according to their Section III program

>> Mechanical methods will be used to cut the Unistrut from the welds

>> Weld material will be ground flush with CV shell, with trace amounts of weld material remaining for the life of the plant

>> Ultrasonic digital thickness measurements of CV shell will be taken to confirm thickness before and after removal of weld material

>> Surface exams of the CV shell will be conducted to identify any discontinuities

>> Supplemental vacuum box testing of remediated areas will be performed to verify no leak paths were created in the CV shell 4

Fracture Toughness

• The 4 long, 1/4 to 3/8 fillet welds made on the surface of the CV are inconsequential when compared to the full penetration welds joining the 1-3/4 thick CV shell plates

• Significantly smaller HAZ than production test plate welds

• Code-Required fracture toughness 40 ft-lb at the lowest service metal temperature (LSMT) of -18.5º F Code allows material to be impact tested at a temperature lower than LSMT

• CV Shell Plates average fracture toughness 221.25 ft-lb at -58.5º F

>5 times the minimum Code-required value at a significantly lower temperature

• Production Test Plates average fracture toughness Production Test Plates were for joining 1-3/4 thick CV shell plates 237 ft-lb at -29º F E9018M Weld Filler Material average fracture toughness = 92.7 ft-lb at -30º F 5

Fracture Toughness

• Unistrut attachment welds

- Welded on 1-3/4 CV shell plates with 3/32 E7018 electrode

- Average fracture toughness of weld filler material used = 133 ft-lb at -20º F

Conclusion:

- The significantly larger welds made for the production test plates yielded fracture toughness results significantly higher than the minimum Code requirements

- Therefore, the impact of the small Unistrut attachment welds is bounded by the production test plate welds, and would also yield fracture toughness values significantly higher than the minimum Code requirements

- It is reasonable to conclude that the HAZ created by the fillet welds will be significantly smaller than that created by the production test plate welds 6

Filler Metal Material Compatibility

• SA-738 Grade B CV shell plate material

• 3/32 EXCALIBUR 7018 MR' filler metal used for Unistrut welds Falls within range, or below maximum allowed metal chemical composition of CV shell plates C Si Mn P S Cu Ni Cr Mo V Nb Material

(%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%)

SA 738 0.15- 0.90-0.20 0.025 0.025 0.35 0.60 0.30 0.30 0.07 0.04 Grade B 0.55 1.50 Excalibur 0.08 0.22 1.11 0.01 0.007 0.03 0.02 0.03 0.23 <0.01 NR 7018 MR

• The reported yield strength of the weld filler metal is 67 ksi, which is above the 60 ksi minimum for SA-738 Grade B, and

• The reported 84 ksi ultimate tensile strength nearly matches the 85 ksi minimum required for SA-738 Grade B 7

Unistrut Material Compatibility

• P-number and Group Number:

SA-738 B A1011 SS Gr 33 - Metals with same P-number have similar materials. In this case P-1 P Number 1 1 means they are both carbon steel.

Group 3 1 Number - A1011 SS Gr. 33 is listed as a P1 Group C% 0.2 0.25 1 material in ASME Section IX (QW-422) and is compatible with P1 Group 3 CE % 0.48% 0.47% material, including SA-738 B (per CBI Spec)

• Temporary Unistrut material attachments are not required to comply with NE-2000 8

Examinations

• HAZ created by the small Unistrut fillet welds made on the surface of the 1-3/4 thick CV shell plate extends only slightly below the surface

• Remediation plan includes surface exams and supplemental Vacuum box testing

- Surface examinations verify that Unistrut welding did not introduce surface indications

- Vacuum box testing verifies that no through-wall leakage paths were introduced to the CV shell

• No NDE can characterize the depth of the HAZ

• Volumetric Examinations are not expected to identify any indications that could not be identified through surface examinations 9

Summary

• Welding was performed on the CV shell by a non-Certificate Holder, after receiving the N-Certificate Stamp and after SIT had been successfully performed

• Alternative Request ALT-16 is being requested to authorize remediation plan, which includes surface examinations and supplemental Vacuum box testing

• Fracture Toughness requirements in NE-2300 are met

• Weld filler material and Unistrut material are compatible with CV shell material

• The proposed alternative along with the plan of remediation, based on evaluations performed by CB&I, provide an acceptable level of quality and safety in accordance with 10 CFR 50.55a 10

Questions Questions 11