ML23334A006

NRR E-mail Capture - South Texas Project - Request for Additional Information - Proposed Alternative to ASME BPV Code Requirements

ML23334A006
Person / Time
Site:	South Texas
Issue date:	11/29/2023
From:	Dennis Galvin NRC/NRR/DORL/LPL4
To:	Brost W South Texas
References
L 2023-LLR-0004
Download: ML23334A006 (5)

Text

From: Dennis Galvin Sent: Wednesday, November 29, 2023 7:02 PM To: Wendy Brost (webrost@stpegs.com)

Cc: Dibbern, Zachary

Subject:

South Texas Project - Request for Additional Information - Proposed Alternative to ASME BPV Code Requirements (EPID: L 2023-LLR-0004)

Attachments: STP RR-ENG-4-06 Tendon Inspection RAI Issued 2023-11-29.pdf

Dear Ms. Brost,

By letter dated February 1, 2023 (ADAMS Accession No. ML23032A484), as supplemented by letters dated March 9, 2023 and August 17, 2023 (ML23068A364 and ML23229A499, respectively), STP Nuclear Operating Company (STPNOC, the licensee) submitted a proposed alternative to the Subsection IWL of the American Society of Mechanical Engineers (ASME)

Boiler and Pressure Vessel (BPV) Code,Section XI, Rules for In-Service Inspection of Nuclear Power Plant Components, regarding the frequency of certain Containment Unbonded Post-Tensioning System Inservice Inspection at South Texas Project (STP) Units 1 and 2.

The NRC staff has determined that additional information is needed to complete its review. The requests for additional information (RAIs) were transmitted to the licensee in draft form on November 15, 2023. On November 27, 2023, the licensee indicated that a clarification call was not necessary, and subsequently the licensee agreed to provide responses to the RAls by December 27, 2023. The NRC staff agrees with this date.

Respectfully,

Dennis Galvin Project Manager U.S Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Division of Operating Reactor Licensing Licensing Project Branch 4 301-415-6256

Docket No. 50-498 and 50-499

Hearing Identifier: NRR_DRMA Email Number: 2318

Mail Envelope Properties (SA1PR09MB8111E9A5F2CE28A9B7691861FB82A)

Subject:

South Texas Project - Request for Additional Information - Proposed Alternative to ASME BPV Code Requirements (EPID L 2023-LLR-0004)

Sent Date: 11/29/2023 7:01:47 PM Received Date: 11/29/2023 7:01:00 PM From: Dennis Galvin

Created By: Dennis.Galvin@nrc.gov

Recipients:

"Dibbern, Zachary" <zedibbern@STPEGS.COM>

Tracking Status: None "Wendy Brost (webrost@stpegs.com)" <webrost@stpegs.com>

Tracking Status: None

Post Office: SA1PR09MB8111.namprd09.prod.outlook.com

Files Size Date & Time MESSAGE 1307 11/29/2023 7:01:00 PM STP RR-ENG-4-06 Tendon Inspection RAI Issued 2023-11-29.pdf 260775

Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

REQUEST FOR ADDITIONAL INFORMATION

PROPOSED ALTERNATIVE TO ASME CODE, SECTION XI REQUIREMENTS FOR

CONTAINMENT BUILDING INSPECTIONS

STP NUCLEAR OPERATING COMPANY

SOUTH TEXAS PROJECT, UNITS 1 AND 2

DOCKET NOS. 50-498 AND 50-499

By letter dated February 1, 2023 (ADAMS Accession No. ML23032A484), as supplemented by letters dated March 9, 2023 and August 17, 2023 (ML23068A364 and ML23229A499, respectively), STP Nuclear Operating Company (STPNOC, the licensee) submitted a proposed alternative to the Subsection IWL of the American Society of Mechanical Engineers (ASME)

Boiler and Pressure Vessel (BPV) Code,Section XI, Rules for In-Service Inspection of Nuclear Power Plant Components, regarding the frequency of certain Containment Unbonded Post-Tensioning System Inservice Inspection at South Texas Project (STP) Units 1 and 2. The proposed alternative designated as revised Relief Request RR-ENG-4-06, refers to the version enclosed in the supplemental letter dated August 17, 2023.

RAI 1

Regulatory Basis:

ASME Section XI, IWL-2421 states, for sites with multiple plants utilizing the same prestressing system and are essentially identical in design, the inspection dates and examination requirements may be as follows.

1) For the containment with the first Structural Integrity Test, all examinations required by IWL-2520 shall be performed at 1, 3, and 10 years and every 10 years thereafter. In addition, the examinations required by IWL-2524 and IWL-2525 shall be performed at 5 and 15 years and every 10 years thereafter.

2) For each subsequent containment constructed at the site, all examinations required by IWL-2520 shall be performed at 1, 5, and 15 years and every 10 years thereafter. In addition, the examinations required by IWL-2524 and IWL-2525 shall be performed at 3 and 10 years and every 10 years thereafter.

Background:

Section 5.1 of the revised Relief Request RR-ENG-4-06 enclosure proposes the following alternative to IWL-2421(b) examination schedules:

1) For Unit 1, all examinations required by IWL-2520 shall be performed at 1, 3, and 10 years, and every 10 years thereafter. In addition, the examinations required by IWL-2524 and IWL-2525 shall be performed at 5, 15, 25, and 40 years and every 10 years thereafter.

2) For Unit 2, all examinations required by IWL-2520 shall be performed at 1, 5, 15, 25, and 40 years, and every 10 years thereafter. In addition, the examinations required by IWL-2524 and IWL-2525 shall be performed at 3 and 10 years and every 10 years thereafter.

The revised Section 5.1 also states, This relief request will only cover through year 40.

Implementation of this plan in years 45 and beyond will require additional relief requests after the 40th year.

The revised Section 6.8 of the RR-ENG-4-06 enclosure states in parts, The Proposed Alternative Surveillance, if approved, would skip the 35 th year surveillance elements associated with IWL-2520 and perform full surveillances in both units during the 40 th... Liftoff testing is scheduled to occur again in Unit 1 in year 40. Therefore, the proposed alternative would make no change to the Unit 1 surveillance schedule for liftoff testing. Liftoff testing is scheduled to occur in Unit 2 in years 35, 45 and 55. The proposed alternative would change that to years 40 and 50*, aligned with Unit 1 liftoff testing. That would introduce a one-time surveillance interval of 15 years between liftoff tests in Unit 2 (between years 25 and 40), with 10-year intervals thereafter*.

The revised Section 6.8 of the RR-ENG-4-06 enclosure also states that, The proposed alternative surveillance extends the interval for visual anchorage inspections from 5 years to 10 years*, with the asterisk stating,

• Assuming acceptance of future relief requests for each 10-year interval; otherwise, surveillances will be continued as required.

Issues:

The proposed alternative discusses future alternatives to IWL-2421(b) for the 40 th year and beyond in addition to the alternative at the 35 th year. The future alternatives are out of our review scope and make the proposed alternative unclear. The proposed alternative adds items L2.10 and L2.20 examinations at Unit 2 for the 40 th and 50th year, but eliminates all examinations at year 45 and 55, that results in performing L2.10 and L2.20 examinations at both units at 40 th year and every 10 years thereafter. The proposed alternative plans to perform items L2.30 to L2.50 examinations at 40 th year and every 10 years thereafter for both Units.

It is the NRC staffs understanding that this relief request only seeks NRCs approval through the 40th year. However, the NRC staff does not find the proposed alternative for the 40 th year and beyond reasonable, and thus does not provide an acceptable level of quality and safety, because: 1) the proposed alternative may allow undetected degradations every 5 years to advance for up to 10 years before taking the necessary corrective actions to preserve the intended function of the unbonded post-tensioning system; 2) the NRC staff only allows for one -

time interval extension if permitted, based on its review of the plant-specific testing results and operating experience provided in the relief request; 3) the NRC staff does not find it reasonable to extend the inspection intervals for the 40 th year and beyond, without reviewing the results of the fourth IWL containment inservice inspection interval inspections, conducted prior to the initiation of the fifth CISI interval; and 4) the NRC staff has not authorized such requests beyond one 10-year interval for any plant, even though requests for authorization through end of license were made for at least three recent similar proposed alternative requests for unbonded post-tensioning system inspection intervals (i.e., Palo Verde (ML22124A241), Calvert Cliffs (ML21190A004), Braidwood and Byron (ML21134A006) and NRC staff stated that its rationale in the SEs. Therefore, the Table IWL-2500-1-(L-B) examination schedules for items L2.10 through L2.50 for both Unit 1 and Unit 2 should remain unchanged for the 40 th year and beyond to provide an acceptable level of quality and safety.

Request:

Revise the proposed alternative to provide an acceptable level of quality and safety for the 40 th year and beyond. For example, keep the Table IWL-2500-1-(L-B) examination schedules unchanged for items L2.10 through L2.50 for both Unit 1 and Unit 2 for the 40 th year and beyond and update the relief request accordingly.