ML23073A156

Relief Request 4RA-22-01, Relief from the Requirements of the ASME Code

ML23073A156
Person / Time
Site:	Seabrook
Issue date:	03/23/2023
From:	Hipolito Gonzalez NRC/NRR/DORL/LPL1
To:	Coffey B Florida Power & Light Co, NextEra Energy Seabrook
References
EPID L-2022-LLR-0074
Download: ML23073A156 (1)

Text

March 23, 2023

Mr. Bob Coffey Executive Vice President, Nuclear and Chief Nuclear Officer Florida Power & Light Company NextEra Energy Seabrook, LLC Mail Stop: EX/JB 700 Universe Blvd.

Juno Beach, FL 33408

SUBJECT:

SEABROOK STATION, UNIT NO. 1 - RELIEF REQUEST 4RA-22-01, RELIEF FROM THE REQUIREMENTS OF THE ASME CODE (EPID L-2022-LLR-0074)

Dear Mr. Coffey:

By letter dated October 26, 2022, as supplemented by letters dated January 26, 2023, and February 24, 2023, (Agencywide Documents Access and Management System (ADAMS)

Accession Nos. ML22300A025 (non-public), ML23026A063, and ML23055A289, respectively)

NextEra Energy Seabrook, LLC (the licensee) submitted relief request (RR) 4RA-22-01 to the U.S. Nuclear Regulatory Commission (NRC) to propose an alternative to the requirements of the American Society of Mechanical Engineers B oiler and Pressure Vessel Code (ASME Code),

Section XI, article IWA-4633.1(d) and article IWA-4634.1(b) at Seabrook Station, Unit No. 1 (Seabrook).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee requested relief on the basis that compliance with the specified ASME Code examination requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that complying with the specified requirements described in the licensees request referenced above would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The proposed alternative provides reasonable assurance that the use of progressive liquid dye penetrant examinations for Seabrook steam generator (SG) bowl drain modifications is a suitable alternative to volumetric inspection and provides reasonable assurance of structural integrity because sound welds are deposited. In addition, the NRC staff has determined that the methods proposed to lower and restore preheat will be sufficient to ensure the final weld will not be impacted as supported by the tests performed by Electric Power Research Institute and the approved ASME Code,Section XI Code Cases. Accordingly, the NRC staff concludes th at the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(2). In reviewing the proposed alternative, the NRC staff also concludes that, as this will be a permanent repair, the overall repair will provide for an acceptable level of quality and sa fety for the remaining life of the plant. The NRC B. Coffey

staff authorizes the use of proposed alternative 4RA-22-001 at Seabrook for the repairs of the SG bowl drain modifications for the four SGs.

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

If you have any questions, please contact the Project Manager, Justin Poole, at 301-415-2048 or by email to Justin.Poole@nrc.gov.

Sincerely,

Hipólito J. González, Chief Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Docket No. 50-443

Enclosure:

Safety Evaluation

cc: Listserv SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION

RELATED TO INSPECTION INSERVICE PROGRAM PROPOSED ALTERNATIVE 4RA-22-001

NEXTERA ENERGY SEABROOK, LLC

SEABROOK STATION, UNIT NO. 1

DOCKET NO. 50-443

1.0 INTRODUCTION

By letter dated October 26, 2022, as supplemented by letters dated January 26, 2023, and February 24, 2023, (Agencywide Documents Access and Management System (ADAMS)

Accession Nos. ML22300A025 (non-public), ML23026A063, and ML23055A289, respectively)

NextEra Energy Seabrook, LLC (the licensee) submitted 4RA-22-01 to the U.S. Nuclear Regulatory Commission (NRC) to propose an alter native to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, article IWA-4633.1(d) and article IWA-4634.1(b) at Seabrook Station, Unit No. 1 (Seabrook).

Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee submitted alternative request 4RA-22-001 reques ting NRC approval of a proposed alternative to the requirement to maintain a minimum preheat temperature of 350°F for temper bead welding per IWA-4633.1(d) and to perform a volumetric examination of the welded region per IWA-4634.1(b). The licensee has concluded that complying with the specified ASME Code requirements to perform a temper bead repair to the channel head bowl drain connection on each steam generator (SG) at Seabrook to alleviate future potential primary water stress corrosion cracking (PWSCC) concerns would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

2.0 REGULATORY EVALUATION

Adherence to Section XI of the ASME Code is mandated by 10 CFR 50.55a(g)(4), which states, in part, that ASME Code Class 1, 2, and 3 com ponents will meet the requirements, except the design and access provisions and the pre-service examination requirements, set forth in the ASME Code,Section XI.

Enclosure

Paragraph 10 CFR 50.55a(z) states, in part, that alternatives to the requirements of paragraphs (b) through (h) of 10 CFR 50.55a or portions thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation. A proposed alternative must be submitted and authorized prior to implementation. The applicant or licensee must demonstrate:

(1) The proposed alternative would provide an acceptable level of quality and safety; or

(2) Compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Based on the above, and subject to the followi ng technical evaluation, the NRC staff has determined that regulatory authority exists for the licensee to request the use of an alternative and the NRC to grant relief and the use of the proposed alternative.

3.0 TECHNICAL EVALUATION

3.1 Relief RR 4RA-22-001

3.1.1 ASME Code Components Affected

ASME Code Class 1 SGs

1-RC-E-11-A 1-RC-E-11-B 1-RC-E-11-C 1-RC-E-11-D

Size: 1 nominal pipe size drain line

Materials:

SG Bottom Channel Head Bowl - ASME SA-533, Grade B, Class 1 Coupling - As identified in a Westinghouse Proprietary Document (non-public),

Weld Metal - As identified in a Westinghouse Proprietary Document (non-public), and 3/8 Penetrating Tube - As identified in a Westinghouse Proprietary Document (non-public).

3.1.2 Applicable Code Edition and Addenda

The current code of record for Seabrook is the ASME Code,Section XI, 2013 Edition, no Addenda.

Seabrook is currently in its fourth 10-year inservice inspection (ISI) interval which began on 8/19/2020 and will end on 8/18/2030.

ASME Code,Section III, 1971 Edition through Summer 1973 Addenda.

Later editions of ASME Code,Section III, are specifically referenced in some sections, as the original code of record did not include provisions for temper bead welding.

3.1.3 Applicable Code Requirement

ASME Code,Section XI, Subsection IWA, provides requirements for repair/replacement activities including the following:

IWA-4633.1(d) specifies the following pre-heat requirements for Temper Bead Welding of Dissimilar Materials with Shielded Metal-Arc Welding (SMAW)

The area to be welded plus a band around the area of at least 1.5 times the component thickness or 5 in. (125 mm), whichever is less, shall be preheated and maintained at a minimum temperature of 350°F (175°C).

The maximum interpass temperature shall be 450°F (230°C).

IWA-4634.1(b) provides the following examination requirement for Temper Bead Welding of Dissimilar Materials

For SMAW, the weld shall be examined after the completed weld has been at ambient temperature for at least 48 hr. For GTAW [gas tungsten arc welding], the nondestructive examinations shall be performed after the completed weld has cooled to ambient temperature. The examination of the welded region shall include volumetric and surface examination.

3.1.4 Reason for Request

The licensee requests relief form the ASME Code,Section XI, Subsection IWA-4633.1(d),

requirement to maintain a minimum preheat temperature of 350°F and the Subsection IWA-4634.1(b) requirement to perform volumetric examination of the welded region, as they would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety in accordance with 10 CFR 50.55a(z)(2).

3.1.5 Proposed Alternative

As an alternative to final volumetric inspecti on per IWA-4634.1(b), the licensee is proposing to perform progressive surface exams with the Liquid Dye Penetrant Examination (PT) process.

Three bead layers will be applied. The PT examination will be performed on 100 percent of each layers surface. PT of the third layer will be performed following the post-weld soak and 48-hour hold. All nondestructive evaluation (NDE) exams will be performed with examiners and procedures qualified in accordance with ASME Code,Section XI.

As an alternative to maintenance of a 350°F degree preheat for the entirety of the temper bead process per the requirements of IWA-4633.1(d), the licensee is proposing to allow a reduction of preheat to not less than 300°F to facilitate the progressive PT examinations. The 350°F preheat will be maintained during all temper bead welding.

3.2 NRC Staff Evaluation

The design and manufacture of Seabrooks four SGs included a drain line coupling at the center of the channel head bowl. The drain line was fabricated by filling a machined cavity with Alloy 182 weld metal and subsequently post-weld heat treated. A through-the-shell hole was subsequently drilled in the channel head and an Alloy 600 tube was hard rolled into the hole to

provide a primary water flow path and seal weld ed at the inside diameter and outside diameter of the SG. The weld buildup was then machined for installation of a stainless steel coupling, which was welded with a partial penetration weld joint and reinforcing fillet weld.

Seabrook is planning an ASME Code,Section XI, repair and replacement activity that will fully remove the Alloy 600 leak path by removing the existing Alloy 182 weld metal and replacing it with weld material as identified in Westinghouse Proprietary document contained in Enclosure 2 to the October 26, 2022, letter. The licensee stated that industry operating experience has shown that Alloy 600 base material and Alloy 82/182 weld filler material is susceptible to PWSCC as several plants with similar designs have experienced borated water leakage through this connection.

Welding of the buttering process will be applied to the surfaces of the newly machined channel head cavity with the SMAW temper bead process and in accordance with all other requirements specified in ASME Code,Section XI IWA-4633.1. The welding will be similar to ASME Code,Section XI, Figure IWA-4623.1-1, and will include a butter layer to the surfaces of the channel head bowl. The weld bead crown will then be removed, and subsequent temper layers are applied, followed by a post-weld elevated temperature soak. The remaining layers are then applied, and the weld is prepared for the coupling. The licensee stated that the temper bead technique will be in accordance with ASME Code,Section III, Paragraph NB-4622.9(d) and ASME Code,Section XI, Paragraph IWA-4630. The licensee clarified that the reference to NB-4622.9(d) applies to editions of ASME Code,Section III, that are later than the original code of record, as the original code did not include provisions for temper bead welding. The licensee referenced the ASME Code,Section III, Rules for Construction of Nuclear Facility Components Division 1, Article NB-4622.9(d), 2010 Edition, No Addenda as a typical edition that specifies the provisions for temper bead welding.

The licensee stated that there have been attempts to develop an ultrasonic examination method have been unsuccessful, largely due to the geometry of the bowl drain, and the partial fillet design. These attempts resulted in an inability to accurately detect and characterize identified indications.

In addition, the licensee also stated that the configuration of the channel head also results in an inability to obtain meaningful results with the radiographic examination method.

The licensee stated that the owners code r equirement for the SG bowl drain was ASME Code,Section III, Division 1, 1971 Edition with Addenda, up to and including Summer 1973.

Later editions of this code allow for progressive surface examination for temper bead repairs to partial penetration welds in lieu of volumetric examinations if meaningful results cannot be obtained. The licensee stated that although the bowl drain joint is not a partial penetration groove weld, it has joint complexity that prevents the ability to obtain meaningful volumetric inspection results.

The licensee stated that the minimum preheat temperature of 350°F is also the maximum allowable temperature for PT. The licensee stated that if heating machines are set to 350°F, it is highly likely that the actual metal temperature in several locations will exceed 350°F by several degrees. To avoid compromising the accuracy and integrity of the NDE process, the material temperature will be lowered to a temperature not less than 300°F.

The NRC staff issued RAI-1 requesting the licensee to identify how the area that will undergo a PT will have the minimum preheat of 300°F maintained uniformly throughout the PT process. In

addition, RAI-2 was issued requesting the acceptance criteria which is to be for the PT examination in lieu of the required ultrasonic techniques examination.

By letter dated January 26, 2023, the applicant provided a response to request for information (RAI)-1 and RAI-2. In its response to RAI-1, the licensee stated that the preheat will be applied by resistance heating elements and the temperature will be controlled uniformly by thermocouples applied to the surface of the channel head. In addition, the preheat temperature of the repair area will be monitored by calibrated contact pyrometers. PT will only be conducted when the surface temperature is between 300°F and 349°F as per the procedure. Welding will only be conducted and resumed when the surface temperature of the repair area has been verified by a calibrated contact pyrometer to meet or exceed the specified minimum preheat temperature of 350°F as required by IWA-4630. In response to RAI-2, the licensee provided the acceptance criteria for the PT examination. The NRC staff reviewed the acceptance criteria and verified it met the requirements of the 1971 Edition through Summer 1973 Addenda of the ASME Code,Section III, Subsection NB-5350. The staff considers the response to the RAIs acceptable because they have provided the specifics as to how they will control and maintain the preheat during welding and PT examinations, and they have also provided the necessary acceptance criteria that is applicable to the repair.

The licensee stated that the reduction of the preheat will not occur until after the completed weld layer has cooled to 350°F, meaning the cooling rate and associated stresses will not be impacted. Similarly, the preheat will be fully restored from 300°F to 350°F and maintained for a minimum of 15 minutes soak time prior to resuming welding.

The licensee further stated that testing that was performed by EPRI concluded that SMAW temper bead welding at ambient temperature resulted in welds with acceptable heat affected zone toughness properties and did not increase susceptibility to delayed hydrogen cracking as the main pathway for diffusible hydrogen is the SMAW electrode coating, which is mitigated by using low hydrogen techniques prescribed in ASME Code,Section XI, IWA-4633. The licensee also stated that Code Case N-839, Similar and Dissimilar Metal Welding Using Ambient Temperature SMAW Temper Bead Technique,Section XI, Division 1, which is approved by Section XI, allows for ambient temperature SMAW temper bead welding. The licensee stated that Code Case N-839 is not being implemented, the basis of the code case provides assurance that a controlled reduction to 300°F followed by a controlled restoration to 350°F will not impact weld quality.

4.0 CONCLUSION

As set forth above, the NRC staff has determined that complying with the specified requirements described in the licensees request re ferenced above would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The proposed alternative provides reasonable assurance that the use of progressive PT examinations for Seabrook SG bowl drain modifica tions is a suitable alternative to volumetric inspection and provides reasonable assurance of structural integrity because sound welds are deposited. In addition, the NRC staff has determined that the methods proposed to lower and restore preheat will be sufficient to ensure the final weld will not be impacted as supported by the tests performed by EPRI and the approved ASME Code,Section XI Code Cases.

Accordingly, the NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(2). In reviewing the proposed alternative, the NRC staff also concludes that, as this will be a permanent repair, the overall repair will provide for an acceptable level of quality and safety for the remaining life of the plant. The NRC staff

authorizes the use of proposed alternative 4RA-22-001 at Seabrook for the repairs of the SG bowl drain modifications for the four SGs.

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

Principal Contributors: E. Reichelt, NRR S. Cumblidge, NRR M. Burton, NRR

Date of Issuance: March 23, 2023

ML23073A156 OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LA NRR/DNRL/NPHP/BC NAME JPoole KZeleznock (KEntz for) MMitchell DATE 03/15/2023 03/15/2023 03/02/2023 OFFICE NRR/DORL/LPL1/BC NRR/DORL/LPL1/PM NAME HGonzalez JPoole DATE 03/23/2023 03/23/2023