ML20227A385

Nonproprietary - Proposed Alternative RR-ENG-3-24 to ASME Code Requirements for the Repair of Essential Cooling Water System Class 3 Buried Piping

ML20227A385
Person / Time
Site:	South Texas
Issue date:	09/03/2020
From:	Dennis Galvin Plant Licensing Branch IV
To:	Gerry Powell South Texas
Galvin D
Shared Package
ML20227A391	List: ML20227A385
References
EPID L-2019-LLR-0096
Download: ML20227A385 (35)

Text

OFFICIAL USE ONLY PROPRIETARY INFORMATION September 3, 2020 Mr. G. T. Powell President and Chief Executive Officer STP Nuclear Operating Company P.O. Box 289 Wadsworth, TX 77483

SUBJECT:

SOUTH TEXAS PROJECT, UNITS 1 AND 2 - PROPOSED ALTERNATIVE RR-ENG-3-24 TO ASME CODE REQUIREMENTS FOR THE REPAIR OF ESSENTIAL COOLING WATER SYSTEM CLASS 3 BURIED PIPING (EPID L-2019-LLR-0096)

Dear Mr. Powell:

By letter dated September 26, 2019, as supplemented by letters dated November 26, 2019, March 9, 2020, July 15, 2020, and July 30, 2020, STP Nuclear Operating Company (the licensee) submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for the use of an alternative to certain American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), Section Xl, Rules for Inservice Inspection of Nuclear Power Plant Components, requirements at South Texas Project (STP) Units 1 and 2.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) paragraph 50.55a(z)(1), the licensee requested to use the proposed Alternative RR-ENG-3-24 to use a carbon fiber reinforced polymer composite system to repair the internal surface of buried essential cooling water piping as an alternative to the repair and replacement requirements of the ASME Code, Section Xl, paragraph IWA-4221, Construction Code and Owners Requirements, subparagraph (b) (i.e., to meet the original Construction Code requirements for the buried essential cooling water piping), during the third and fourth 10-year inservice inspection intervals at STP Units 1 and 2 on the basis that the proposed alternative provides an acceptable level of quality and safety.

The NRC staff has reviewed the subject requests and concludes, as set forth in the enclosed safety evaluation, that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(1) and demonstrated that the proposed alternatives provide an acceptable level of quality and safety. Therefore, the NRC staff authorizes the use of proposed Alternative RR-ENG-3-24 for the third and fourth 10-year inservice inspection interval at STP Units 1 and 2.

Enclosure 1 to this letter contains sensitive unclassified non-safeguards information. When separated from Enclosure 1, this document is DECONTROLLED.

OFFICIAL USE ONLY PROPRIETARY INFORMATION

OFFICIAL USE ONLY PROPRIETARY INFORMATION G. Powell All other requirements in ASME Code,Section XI, for which relief or an alternative was not specifically requested and approved as part of this subject request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

The NRC staff has determined that the safety evaluation provided in Enclosure 1 contains proprietary information pursuant to 10 CFR Section 2.390, Public inspections, exemptions, requests for withholding. Accordingly, the NRC staff has prepared a non-proprietary version, which is provided in Enclosure 2.

If you have any questions, please contact the Project Manager, Dennis Galvin at 301-415-6256 or via e-mail at Dennis.Galvin@nrc.gov.

Sincerely, Digitally signed by Jennifer L. Jennifer L. Dixon-Herrity Date: 2020.09.03 Dixon-Herrity 13:34:08 -04'00' Jennifer L. Dixon-Herrity, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosures:

1. Safety Evaluation (proprietary)

2. Safety Evaluation (non-proprietary) cc w/o Enclosure 1: Listserv OFFICIAL USE ONLY PROPRIETARY INFORMATION

OFFICIAL USE ONLY PROPRIETARY INFORMATION ENCLOSURE 2 (NON-PROPRIETARY)

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE RR-ENG-3-24 TO ASME CODE SECTION XI REQUIREMENTS FOR REPAIR/REPLACEMENT OF ESSENTIAL COOLING WATER PIPING STP NUCLEAR OPERATING COMPANY SOUTH TEXAS PROJECT, UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499 Proprietary information pursuant to Title 10 of Code of Federal Regulations, Section 2.390 has been redacted from this document.

Redacted information is identified by blank space enclosed within double brackets, as shown here: (( )).

OFFICIAL USE ONLY PROPRIETARY INFORMATION SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE RR-ENG-3-24 TO ASME CODE SECTION XI REQUIREMENTS FOR REPAIR/REPLACEMENT OF ESSENTIAL COOLING WATER PIPING STP NUCLEAR OPERATING COMPANY SOUTH TEXAS PROJECT, UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499

1.0 INTRODUCTION

By letter dated September 26, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19274C393), as supplemented by letters dated November 26, 2019, March 9, 2020, July 15, 2020, and July 30, 2020 (ADAMS Accession Nos. ML19331A202, ML20069L499, ML20197A261, and ML20212L568, respectively), STP Nuclear Operating Company (the licensee) submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for the use of an alternative to certain American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), Section Xl, Rules for Inservice Inspection of Nuclear Power Plant Components, requirements at South Texas Project (STP) Units 1 and 2.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR)

Section 50.55a(z)(1), Acceptable level of quality and safety, the licensee requested to use the proposed Alternative RR-ENG-3-24 to use a carbon fiber reinforced polymer (CFRP) composite system to repair the internal surface of buried essential cooling water (ECW) piping as an alternative to the repair and replacement requirements of the ASME Code, Section Xl, paragraph IWA-4221, Construction Code and Owners Requirements, subparagraph (b)

(i.e., to meet the original Construction Code requirements for the buried ECW piping), during the third and fourth 10-year inservice inspection (ISI) intervals at STP Units 1 and 2 on the basis that the proposed alternative provides an acceptable level of quality and safety.

2.0 REGULATORY EVALUATION

The NRC regulations in 10 CFR 50.55a(g)(4), Inservice inspection standards requirement for operating plants, state, in part, that ASME Code Class 1, 2, and 3, components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI.

The regulations in 10 CFR 50.55a(z), Alternatives to codes and standards requirements, state, in part, that alternatives to the requirements of 10 CFR 50.55a(f) may be used, when authorized by the NRC, if the licensee demonstrates (1) the proposed alternatives would provide an OFFICIAL USE ONLY PROPRIETARY INFORMATION

OFFICIAL USE ONLY PROPRIETARY INFORMATION acceptable level of quality and safety or (2) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Based on the above regulations, the NRC staff concludes that regulatory authority exists to authorize an alternative to ASME Code,Section XI, as requested by the licensee.

3.0 TECHNICAL EVALUATION

3.1 The Licensees Proposed Alternative 3.1.1 ASME Code Components Affected The affected component is the buried ASME Code Class 3 ECW piping. The piping sections that will be repaired using the proposed CFRP composite are specified in Enclosure 2 to the letter dated September 26, 2019, hereafter referred to as the alternative request. The ECW piping consists of 30-inch ECW system intake piping and fittings from the intake structure to the mechanical auxiliary building and the discharge piping from the mechanical auxiliary building to the discharge structure. The ECW piping was designed and installed in accordance with the 1974 Edition through 1975 Winter Addenda of the ASME Code,Section III, Rules for Construction of Nuclear Facility Components, Subsection ND, Class 3 Components.

The subject piping is below grade and buried, and has long straight runs with minimal bends and elbows. The exterior surface of the pipe is coated with coal-tar with an impressed current cathodic protection system to mitigate corrosion. The licensee stated that it has not identified degradation of the exterior surface of the pipe. The licensee further stated that the soil has high resistive characteristics further reducing the possibility of corrosion on the piping exterior surface. The piping is fabricated of aluminum-bronze material conforming to American Society of Testing and Materials (ASTM) International SB169, Standard Specification for Aluminum Bronze Sheet, Strip and Rolled Bar, Alloy CA-614. The subject piping has no pumps, valves, expansion joints, flange joints, or threaded connections included in the scope of work.

3.1.2 Applicable ASME Code Edition and Addenda The ASME Code of Record for the third ISI interval at STP Units 1 and 2 is the ASME Code, Section Xl, 2004 Edition with no Addenda. The ASME Code of Record for the fourth ISI interval at STP Units 1 and 2 is the ASME Code, Section Xl, 2013 Edition.

3.1.3 Applicable ASME Code Requirement ASME Code, Section Xl, Article IWA-4000, Repair/Replacement Activities, subparagraph IWA-4221(b), states that, An item to be used for repair/replacement activities shall meet the Construction Code specified in accordance with [subparagraphs IWA-4221(b)(1),

IWA-4221(b)(2), or IWA-4221(b)(3)].

Subparagraph IWA-4221(b)(1) states that, When replacing an existing item, the new item shall meet the Construction Code to which the original item was constructed.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION 3.1.4 Reason for Request The licensee will perform ISI of the ECW piping in the fall of 2020 and is proactively requesting approval to use the proposed CFRP composite as a contingency to address any potential degradation within the ECW pipe wall. The licensee stated that the most likely internal degradation mechanism is flow induced erosion, and that buried ECW piping is not susceptible to selective leaching due to pipe material composition.

The licensee stated that the NRC approved the use of the CFRP composite system on the interior of concrete encased, buried safety-related carbon steel piping at the Surry Power Station in 2018 with the upgrade program continuing through 2024 as shown in an NRC letter to Virginia Electric and Power Company, dated December 20, 2017 (ADAMS Accession No. ML17303A068).

3.1.5 Proposed Alternative The licensee proposed to repair the internal surface of the ECW piping using the CFRP composite system as discussed in proposed Alternative RR-ENG-3-24.

3.1.6 Basis for Use 3.1.6.1 General Information

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In addition, the licensee discussed the ISIs of the CFRP-repaired ECW piping.

3.1.6.2 Design Criteria The design criteria, including objectives, approach, methodologies, applicable standards, technical criteria, loads, load combinations, applicable design factors, and effective safety factors, are discussed in Enclosure 5, Attachment A, of the alternative request. The various aspects of the design criteria are grouped into strength, reliability, durability, and design approach as discussed below.

Strength

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Reliability

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Durability

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Design Approach

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3.1.6.3 Design Loads

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Load Combinations for Design LSs

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Failure Modes and Effects Analysis

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An overview of the calculation procedure for LS1 through LS9 was discussed above, and detailed calculations are presented in Enclosure 5, Attachment C, of the alternative request.

3.1.6.4 Material Controls of the alternative request discusses material manufacturing, qualification and testing, and watertightness testing as summarized below.

Material Manufacturing

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Material Qualification and Testing

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Material Watertightness Testing

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3.1.6.5 Installation Controls of the alternative request specifies the installation controls, which include pre-installation preparation, installation, in-process inspection, in-process repair, acceptance examination, and pressure testing, as summarized below.

Pre-Installation Preparation

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Installation

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In the July 15, 2020, letter, the licensee provided additional information regarding tensile tests of the CFRP layers. ((

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In the letter dated July 15, 2020, the licensee provided additional information regarding curing of the CFRP layers. The licensee stated that:

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In-Process Inspection

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In-Process Repair

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Acceptance Examination

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Pressure Testing In the supplement dated March 9, 2020, the licensee stated that System start-up testing will be in accordance with [ASME Code, Section Xl, IWA-5244(b)(2)], which directs that the system pressure test for non-isolable buried components shall consist of a test to confirm that flow during operation is not impaired. This testing will demonstrate and document performance of flow tests on the ECW System flow paths that support the required safety functions.

3.1.6.6 Inservice Examination The licensee stated that ISI activities will include system flow testing performed in accordance with each stations system pressure test plans and ASME Code, Section Xl, subparagraph IWA-5244(b)(2), at least once each ISI interval, for the remaining life of the plant, to verify adequate flow through the ECW piping.

The licensee will also (a) determine the extent of biological fouling, sediment buildup, and corrosion, including microbiologically-induced corrosion, (b) assess the effectiveness of biofouling control mechanisms and protective coating technologies, and (c) monitor the material integrity of metallic components and protective coating, and installed expansion ring seals. The licensee stated that corrosion inspection criteria to be identified and quantified includes localized pitting, general pipe wall thinning, and microbiologically influenced corrosion. Biological inspection criteria include inspecting for typical biological growth and species including hydroid and bryozoan growth, and clams in the ECW intake structure pump bays.

In addition, the licensee stated in its alternative request that it will inspect buried ECW piping in each 10-year ISI interval, beginning with the 10-year ISI interval prior to extended operation of the renewed operating license in accordance with criteria set forth in the STP Updated Final Safety Analysis Report (UFSAR), Chapter 19A, License Renewal, Section 19A.1.18, Buried Piping and Tanks Inspection (ADAMS Accession No. ML18130A044).

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OFFICIAL USE ONLY PROPRIETARY INFORMATION 3.1.6.7 Quality Controls

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3.1.6.8 Duration of Proposed Alternative The licensee plans to install the CFRP composite on the ECW piping at STP Units 1 and 2 during the third and fourth 10-year ISI intervals of each STP unit.

For STP Unit 1, the third 10-year ISI interval began on September 25, 2010, and ends on September 24, 2020, and the fourth 10-year ISI interval begins on September 25, 2020, and ends on September 24, 2030. For STP Unit 2, the third ISI interval began on October 19, 2010, and ends on September 24, 2020, and the fourth 10-year ISI interval begins on September 25, 2020, and ends on September 24, 2030.

The licensee stated in its alternative request that the CFRP composite will remain in place for the life of plant and the repaired piping is to remain in service for the life of the repair. The licensee further stated that any repair/replacement and/or inspections of the repaired piping will be conducted in accordance with the applicable edition of the ASME Code,Section XI, or alternative thereto, at the time of the repair/replacement or inspection.

3.2 NRC STAFF EVALUATION The NRC staff evaluated the proposed CFRP system in the areas of design, material, installation, examination, and quality control.

3.2.1 Design The NRC staff reviewed the licensees plant-specific stress calculation summaries for repairs proposed in the alternative request provided by the licensee. ((

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The NRC staff notes that the licensees calculations have considered the appropriate load combinations in analyzing the repaired pipes of 30-inch diameter. The NRC staff also notes that the licensee used results from Water Research Foundations research program primarily developed for nonsafety-related applications. These included full-scale field experiments of prestressed concrete cylinder pipe (PCCP) subjected to the combined effects of internal pressure and external loads to study modes and loads at failure; laboratory scale experiments to determine shear bond strength; and development of simplified and reliable design formulas.

The research program also included investigation using finite element analysis of CFRP-lined buried PCCP to analyze the combined effects of gravity loads and pressures to validate the accuracy and conservatism of simplified design formulas for LSs including pressure, bending, and stability (buckling). In such analyses, stresses in the CFRP system and its buckling load resulting from interaction of the CFRP system, host pipe, and surrounding soil were calculated as the host pipe continues to degrade during its service life.

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The NRC staff concludes that the licensee has performed an acceptable failure modes and effects analysis, because the licensee has considered significant potential failure modes and demonstrated that the CFRP system is designed to mitigate or prevent the potential failures.

The NRC staff notes that CFRP has been used in aerospace, automotive, marine, and sports industries because of its advantage of high strength combined with low weight. The NRC staff also notes that the NRC regulations do not address the AWWA guidance. The NRC staff evaluated the proposed alternative based on the merits of its technical basis in lieu of the AWWA guidance or proposed ASME Code Case under development. The NRC staff notes that research results, in and of themselves, do provide reasonable assurance of the performance of the proposed CFRP system.

Terminations

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Allowable Stress Design Methodology in ASME Code, Subsection NC/ND Classes 2 and 3

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The following table is a summary of the calculated ASD methodology values:

ASD Methodology Summary:

Computed / Allowable 1 or Allowable/Computed 1 Codes Prior to 1999 Codes After 1999 With FS = 4 With FS = 3.5 With FS = 10 Values up to 1981 (Ductile) (Ductile) (Brittle)

Longitudinal (Rows 3-7) Effective FSeff FSeff FSeff Normal (Level-A) k=1 4 3.5 10 Upset (Level-B) k=1.2 3.33 2.92 8.33 OFFICIAL USE ONLY PROPRIETARY INFORMATION

OFFICIAL USE ONLY PROPRIETARY INFORMATION Codes Prior to 1999 Codes After 1999 With FS = 4 With FS = 3.5 With FS = 10 Values up to 1981 (Ductile) (Ductile) (Brittle)

Emergency (Level-C) k=1.8 2.22 1.94 5.56 Faulted (Level-D) k=2.4 1.67 1.46 4.17 Thermal stresses (if 7000 2.67 2.33 6.67 cycles) 1.5 Sh approx.

((1.25Sc+0.25Sh)

Hoop Direction 4 3.5 10 With FS = 4 With FS = 3.5 With FS = 10 Values after 1981 (Ductile) (Ductile) (Brittle)

Longitudinal (Rows 3-7) FSeff FSeff FSeff Normal (Level-A) k=1.5 2.67 2.33 6.67 Upset (Level-B) k=1.8 2.22 1.94 5.56 Emergency (Level-C) k=2.25 1.78 1.56 4.44 Faulted (Level-D) k=3 1.33 1.17 3.33 Thermal stresses (if 7000 2.67 2.33 6.67 cycles) 1.5 Sh a Hoop Direction 4 3.5 10

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Results of Effective FSs for End Use and Their Acceptability For degraded Aluminum-Bronze piping, the ECW system safety-related Class 3 buried 30-inch diameter piping at STP Units 1 and 2 will be repaired using CFRP composite. The following tables summarize the results of FSeff. ((

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Based on the NRC staff review and evaluation as described above, it is concluded that CFRP repair is structurally adequate as the evaluations for the various LSs demonstrated that the effective FSs meet the minimum acceptable values providing reasonable assurance regarding the structural integrity of the proposed repair.

The NRC staffs review of licensees calculations as described above indicates that the CFRP system design provided in the alternative request satisfies the acceptance criteria for the applicable LSs. Therefore, the NRC staff finds that there is reasonable assurance that the OFFICIAL USE ONLY PROPRIETARY INFORMATION

OFFICIAL USE ONLY PROPRIETARY INFORMATION proposed repair of degraded ECW system using CFRP composite including the terminations overlapping with the host Aluminum-Bronze piping will maintain structural integrity. The NRC staff concludes that the CFRP design used for the repair of degraded piping at STP Units 1 and 2 is acceptable.

Failure Modes and Effects Analysis The NRC staff concludes that the licensee has performed an adequate failure modes and effects analysis because the licensee has considered potential, credible failure modes of the installed CFRP layers, discussed the basis of why the failure mode is not possible, and provided solutions to either prevent or minimize the failure modes. Therefore, the NRC staff finds that the licensees failure modes and effect analysis is acceptable.

The NRC staff finds that the proposed CFRP composite satisfies the design criteria of the subject piping such that the CFRP layers will be able to support the existing pipe loads without considering the host pipe base metal except at the terminations. The CFRP terminations act as interface to transfer loads from the repaired sections with intact host pipe. The NRC staff concludes that the terminations are adequately designed to maintain their structural integrity.

3.2.2 Material

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3.2.3 Installation

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The NRC staff finds acceptable that the licensee will provide training to the installers and inspectors on the knowledge, skills, and abilities needed to perform the assigned duties. The installers will be trained by installing the actual CFRP system on a mockup, and the inspectors will be trained by examining the mockup with CFRP layers installed. The NRC staff finds that the licensee has provided adequate and necessary requirements and procedures for the installation of the CFRP systems.

3.2.4 Examinations

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For the ISI, the NRC staff determined that the licensee will perform system flow testing in accordance with the ASME Code, Section Xl, paragraph IWA-5244(b)(2), at least once each ISI interval for the remaining life of the plant to verify adequate flow through the ECW piping.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION The NRC staff notes that the licensee will inspect buried ECW piping in each 10-year ISI interval, beginning with the 10-year ISI interval prior to extended operation of the renewed operating license in accordance with criteria set forth in the STP UFSAR, Chapter 19A, Section 19A.1.18.

The NRC staff concludes that the proposed acceptance examination and ISIs will ensure structural integrity of the repaired subject piping with the CFRP system and are, therefore, acceptable.

3.2.5 Quality Control The NRC staff finds that the design controls, material controls, installation, and QA and QC of the proposed CFRP composite system satisfy the requirements of 10 CFR Part 50, Appendix B, and are, therefore, acceptable.

4.0 CONCLUSION

As set forth above, the NRC staff finds that Proposed Alternative RR-ENG-3-24 described in the letter dated September 26, 2019, as supplemented by letters dated November 26, 2019, March 9, 2020, July 15, 2020, and July 30, 2020, for use of a CFRP composite system to repair the internal surface of buried ECW piping is acceptable on the basis that the proposed alternative provides an acceptable level of quality and safety. The NRC staff finds that the proposed alternative will provide reasonable assurance of the structural integrity and leaktightness of the buried ECW piping. Accordingly, the NRC staff concludes that the licensee has adequately addressed the regulatory requirements in 10 CFR 50.55a(z)(1). Therefore, the NRC staff authorizes the use of Alternative RR-ENG-3-24 for the third and fourth 10-year lSI interval at STP Units 1 and 2.

All other requirements in ASME Code,Section XI, for which relief or an alternative was not specifically requested and approved as part of this subject request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

Principal Contributors: Chakrapani Basavaraju John Tsao Date September 3, 2020 OFFICIAL USE ONLY PROPRIETARY INFORMATION