ML19269C534
| ML19269C534 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs, Dresden, Peach Bottom, Nine Mile Point, Byron, Braidwood, Limerick, Ginna, Clinton, Quad Cities, FitzPatrick, LaSalle, Crane  |
| Issue date: | 09/27/2019 |
| From: | Lisa Regner Plant Licensing Branch III |
| To: | Bryan Hanson Exelon Generation Co, Exelon Nuclear |
| Purnell B | |
| References | |
| EPID L-2019-LLR-0011 | |
| Download: ML19269C534 (10) | |
Text
September 27, 2019 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer (CNO)
Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
BRAIDWOOD STATION, UNITS 1 AND 2; BYRON STATION, UNIT NOS. 1 AND 2; CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2; CLINTON POWER STATION, UNIT NO. 1; DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3; JAMES A. FITZPATRICK NUCLEAR POWER PLANT; LASALLE COUNTY STATION, UNITS 1 AND 2; LIMERICK GENERATING STATION, UNITS 1 AND 2; NINE MILE POINT NUCLEAR STATION, UNITS 1 AND 2; PEACH BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3; QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2; AND R. E. GINNA NUCLEAR POWER PLANT - PROPOSED ALTERNATIVE TO USE ENCODED PHASED ARRAY ULTRASONIC EXAMINATION TECHNIQUES (EPID L-2019-LLR-0011)
Dear Mr. Hanson:
By letter dated February 15, 2019 (Agencywide Documents and Access Management System (ADAMS) Accession No. ML19049A001), as supplemented by letter dated June 25, 2019 (ADAMS Accession No. ML19176A343), Exelon Generation Company, LLC (the licensee) submitted a request in accordance with paragraph 50.55a(z)(1) of Title 10 of the Code of Federal Regulations (10 CFR) for a proposed alternative to the requirements of 10 CFR 50.55a and the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) at Braidwood Station, Units 1 and 2 (Braidwood); Byron Station, Unit Nos. 1 and 2 (Byron); Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (Calvert Cliffs); Clinton Power Station, Unit No. 1 (Clinton); Dresden Nuclear Power Station, Units 2 and 3 (Dresden); James A.
FitzPatrick Nuclear Power Plant (FitzPatrick); LaSalle County Station, Units 1 and 2 (LaSalle);
Limerick Generating Station, Units 1 and 2 (Limerick); Nine Mile Point Nuclear Station, Units 1 and 2 (NMP); Peach Bottom Atomic Power Station, Units 2 and 3 (Peach Bottom); Quad Cities Nuclear Power Station, Units 1 and 2 (Quad Cities); and R. E. Ginna Nuclear Power Plant (Ginna). The proposed alternative would allow the licensee to use encoded phased array ultrasonic examination techniques in lieu of radiography for ferritic steel and austenitic stainless-steel piping welds for each of these facilities.
The application also requested to use the proposed alternative at Three Mile Island Nuclear Station (TMI), Unit 1. However, the licensee withdrew the request for TMI by letter dated June 17, 2019 (ADAMS Accession No. ML19169A031).
B. Hanson The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(1). Therefore, the NRC staff authorizes the use of the proposed alternative for the remainder of the current 10-year inservice inspection intervals at Braidwood Units 1 and 2, Byron Unit Nos. 1 and 2, Calvert Cliffs Units 1 and 2, Clinton, Dresden Units 2 and 3, FitzPatrick, LaSalle Units 1 and 2, Limerick Units 1 and 2, NMP Units 1 and 2, Peach Bottom Units 2 and 3, Quad Cities Units 1 and 2, and Ginna, as specified in the licensees June 25, 2019, letter. In addition, the NRC staff authorizes the use of the proposed alternative for the duration of the fourth 10-year inservice inspection interval at Clinton and the sixth 10-year inservice inspection interval at Ginna, as specified in the licensees June 25, 2019, letter.
All other ASME Code requirements for which relief has not been specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
If you have any questions, please contact Blake Purnell at 301-415-1380 or via e-mail at Blake.Purnell@nrc.gov.
Sincerely,
/RA/
Lisa M. Regner, Acting Branch Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-456, STN 50-457, STN 50-454, STN 50-455, 50-317, 50-318, 50-461, 50-237, 50-249, 50-333 50-373, 50-374, 50-352, 50-353, 50-220, 50-410, 50-277, 50-278, 50-254, 50-265, 50-244, and 50-289
Enclosure:
Safety Evaluation cc: Listserv
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE TO USE ENCODED PHASED ARRAY ULTRASONIC EXAMINATION TECHNIQUES BRAIDWOOD STATION, UNITS 1 AND 2; BYRON STATION, UNIT NOS. 1 AND 2; CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2; CLINTON POWER STATION, UNIT NO. 1; DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3; JAMES A. FITZPATRICK NUCLEAR POWER PLANT; LASALLE COUNTY STATION, UNITS 1 AND 2; LIMERICK GENERATING STATION, UNITS 1 AND 2; NINE MILE POINT NUCLEAR STATION, UNITS 1 AND 2; PEACH BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3; QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2; AND R.E. GINNA NUCLEAR POWER PLANT.
EXELON GENERATION COMPANY, LLC DOCKET NOS. STN 50-456, STN 50-457, STN 50-454, STN 50-455, 50-317, 50-318, 50-461, 50-237, 50-249, 50-333, 50-373, 50-374, 50-352, 50-353, 50-220, 50-410, 50-277, 50-278, 50-254, 50-265, AND 50-244
1.0 INTRODUCTION
By letter dated February 15, 2019 (Agencywide Documents and Access Management System (ADAMS) Accession No. ML19049A001), as supplemented by letter dated June 25, 2019 (ADAMS Accession No. ML19176A343), Exelon Generation Company, LLC (the licensee) submitted a request in accordance with paragraph 50.55a(z)(1) of Title 10 of the Code of Federal Regulations (10 CFR) for a proposed alternative to the requirements of 10 CFR 50.55a and the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) at Braidwood Station, Units 1 and 2 (Braidwood); Byron Station, Unit Nos. 1 and 2 (Byron); Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (Calvert Cliffs); Clinton Power Station, Unit No. 1 (Clinton); Dresden Nuclear Power Station, Units 2 and 3 (Dresden); James A.
FitzPatrick Nuclear Power Plant (FitzPatrick); LaSalle County Station, Units 1 and 2 (LaSalle);
Limerick Generating Station, Units 1 and 2 (Limerick); Nine Mile Point Nuclear Station, Units 1 and 2 (NMP); Peach Bottom Atomic Power Station, Units 2 and 3 (Peach Bottom); Quad Cities Nuclear Power Station, Units 1 and 2 (Quad Cities); and R. E. Ginna Nuclear Power Plant (Ginna).
For each of these facilities, the proposed alternative would allow the licensee to use encoded phased array ultrasonic testing (PAUT) in lieu of radiographic testing (RT) for volumetric examination of ferritic or austenitic piping welds during repair and replacement activities.
Specifically, pursuant to 10 CFR 50.55a(z)(1), the licensee requested to use the alternative on the basis that it will provide an acceptable level of quality and safety.
The application also requested to use the proposed alternative at Three Mile Island Nuclear Station (TMI), Unit 1. However, the licensee withdrew the request for TMI by letter dated June 17, 2019 (ADAMS Accession No. ML19169A031). Therefore, this safety evaluation is not applicable to TMI.
2.0 REGULATORY EVALUATION
The regulations in 10 CFR 50.55a(g)(4) state, in part, that ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in Section XI of the applicable editions and addenda of the ASME Code to the extent practical within the limitations of design, geometry, and materials of construction of the components.
Paragraph 10 CFR 50.55a(g)(4)(ii) requires, in part, that inservice examination of components and system pressure tests conducted during successive 10-year inservice inspection (ISI) intervals (i.e., after the initial 10-year interval) must comply with the latest edition and addenda of the ASME Code (or the optional ASME Code Cases) incorporated by reference in 10 CFR 50.55a(a) 12 months before the start of the 10-year interval subject to the conditions listed in 10 CFR 50.55a(b).
The regulations in 10 CFR 50.55a(z) state, in part, that alternatives to the requirements in paragraphs (b) through (h) of 10 CFR 50.55a may be authorized by the NRC if the licensee demonstrates that: (1) the proposed alternative provides an 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.
3.0 TECHNICAL EVALUATION
3.1 Licensees Relief Request 3.1.1 ASME Code Components Affected For each facility, the proposed alternative is for all ferritic and austenitic piping welds that require radiography, in accordance with ASME Code,Section XI, as part of a repair or replacement activity.
3.1.2 Applicable Code Edition and Addenda The application, as supplemented, identified the applicable ASME Code editions and addenda for each plant as shown in the table below. In addition, the table shows the associated 10-year ISI interval, including the start and end dates, for each plant.
PLANT ISI INTERVAL ASME CODE EDITION START END Braidwood Unit 1 4th 2013 Edition 8/29/2018 7/28/2028 Braidwood Unit 2 4th 2013 Edition 11/5/2018 10/16/2028 Byron Units 1 and 2 4th 2007 Edition, through 2008 Addenda 7/16/2016 7/15/2025 Calvert Cliffs 5th1 2013 Edition 7/1/2019 6/30/2029 Clinton 3rd 2004 Edition 7/1/2010 6/30/2020 4th 2013 Edition 7/1/2020 6/30/2030 Dresden Units 2 and 3 5th 2007 Edition, through 2008 Addenda 1/20/2013 1/19/2023 FitzPatrick 5th 2007 Edition, through 2008 Addenda 8/1/2017 6/15/2027 LaSalle Units 1 and 2 4th 2007 Edition, through 2008 Addenda 10/1/2017 9/30/2027 Limerick Units 1 and 2 4th 2007 Edition, through 2008 Addenda 2/1/2017 1/31/2027 NMP Unit 1 5th2 2013 Edition 8/23/2019 8/22/2029 NMP Unit 2 4th 2013 Edition 10/6/2018 8/22/2028 Peach Bottom Units 2 and 3 5th 2013 Edition 1/1/2019 12/31/2028 Quad Cities Units 1 and 2 5th 2007 Edition, through 2008 Addenda 4/2/2013 4/1/2023 Ginna 5th 2004 Edition 1/1/2010 12/31/2019 6th 2013 Edition 1/1/2020 12/31/2029 The ASME Code requirements applicable to repair and replacement activities originate in Article IWA-4000 of Section XI.Section XI, paragraph IWA-4221, of the ASME Code requires that items used for repair or replacement activities meet the owners requirements and the applicable construction code requirements.
1 The application, as supplemented, incorrectly identified this ISI interval as the 4th ISI interval.
2 In addition to the 5th ISI interval, the licensee requested to use the proposed alternative for the remainder of the 4th ISI interval at NMP Unit 1. However, the 4th ISI interval ended on August 22, 2019.
Section XI, paragraph IWA-4520, of the 2004 Edition of the ASME Code requires that welded joints made for installation of items be examined in accordance with the construction code identified in the repair and replacement plan. The 2008 Addenda to the ASME Code revised paragraph IWA-4520(b) and added paragraph IWA-4521 to allow the owner to authorize use of ultrasonic examination in place of radiographic examination if the conditions of paragraph IWA-4521 are met. However, 10 CFR 50.55a(b)(2)(xix) prohibits the use of the provisions in IWA-4520(b)(2) and IWA-4521 of the 2008 Addenda through the 2013 Edition of the ASME Code.
3.1.3 Proposed Alternative and Basis for Use The licensee proposed to use the encoded PAUT in lieu of the RT required by the ASME Code for volumetric examination of ferritic steel or austenitic stainless-steel piping welds during repair and replacement activities. Ultrasonic and radiographic testing are two volumetric examination techniques that are commonly used to inspect welds in nuclear power plants and in other industries. The two techniques use different physical mechanisms to detect and characterize discontinuities, which results in several key differences in sensitivity and discrimination capability between the two techniques.
The proposed alternative includes requirements for qualification of the encoded PAUT procedures, equipment, and personnel by the performance demonstration using representative piping conditions and flaws. The licensee stated that this approach will demonstrate the ability of the encoded PAUT to detect and accurately size flaws that are both acceptable and unacceptable to the defined acceptance standards. Section 5.1 of the application, as supplemented, provides a detailed description of the licensees proposed alternative.
The licensee stated that the technical basis for the proposed alternative was developed from numerous codes and code cases, associated industry experience, research articles, and results of welds examinations by the ultrasonic and radiographic techniques. The licensee stated that encoded PAUT is equivalent or superior to RT for detecting and sizing critical (planar) flaws such as cracks and lack of fusion. Encoded PAUT provides sizing capabilities for both depth and length dimensions of the flaw; however, RT does not have the flaw depth sizing capabilities.
3.2
NRC Staff Evaluation
While both ultrasonic and radiographic testing techniques can detect a spectrum of flaws resulting from fabrication welding processes, the differences in physical and material interactions can make one technique more sensitive to certain fabrication flaw types than the other technique. An assessment of the use of ultrasonic testing (UT) in lieu of RT is described in NRC NUREG/CR-7204, Applying Ultrasonic Testing In Lieu of Radiography for Volumetric Examination of Carbon Steel Piping, published September 2015 (ADAMS Accession No. ML15253A674). This assessment concluded that encoded PAUT is as effective as RT for identifying the presence of fabrication flaws in carbon steel welds. However, the assessment also found that encoded PAUT is more effective than RT for detecting planar flaws, but slightly less effective than RT for detecting small volumetric flaws.
The Electric Power Research Institute (EPRI) published Technical Report (TR) No. 3002010297 Technical Basis for Substituting Ultrasonic Testing for Radiographic Testing for New, Repaired, and Replacement Welds for ASME Section XI, Division 1, Stainless Steel Piping, in June 2017.
The report summarizes EPRIs performance-based approach using Appendix VIII of the ASME Code,Section XI, to demonstrate the effectiveness of encoded PAUT at detecting and sizing fabrication flaws in austenitic stainless-steel piping welds. For the performance demonstration, EPRI designed and fabricated mockups containing representative welding fabrication flaws.
The flaw distribution included both rejectable and acceptable flaw sizes in accordance with the acceptance standards of paragraph IWB-3514 and flaw characterization figures in Subarticle IWA-3300 of the ASME Code,Section XI. The EPRI performance demonstration initiative generic procedures PDI-UT-2 and PDI-UT-3 were used for examination and flaw sizing. EPRI showed that its PAUT technique met the acceptance criteria for the root mean square (RMS) error of the flaw lengths and depths in Appendix VIII of the ASME Code,Section XI. EPRI demonstrated that its encoded PAUT technique is effective for detecting and sizing of fabrication flaws within austenitic stainless steel welds.
Based on the findings discussed in NUREG/CR-7204 and EPRI TR No. 3002010297, the NRC staff determined that there is a sufficient technical basis for the use of encoded PAUT in lieu of RT for the examination of ferritic steel and austenitic stainless-steel piping welds. Given that encoded PAUT can be effective at detecting flaws, the staff considered whether the proposed alternative applies UT in a way that provides reasonable assurance of finding structurally-significant flaws.
Important aspects of the licensees proposed alternative include:
The licensee will examine 100 percent of the weld volume and the weld-to-base-metal interface.
The licensee will perform ultrasonic examinations using procedures, equipment, and personnel qualified by performance demonstration.
Ultrasonic examination procedures will be qualified by using either a blind or a nonblind performance demonstration using a minimum of 30 flaws covering a range of sizes, positions, orientations, and types of fabrication flaws. The demonstration set shall include specimens to represent the minimum and maximum diameter and thickness covered by the procedure.
The demonstration specimens will include both planar and volumetric fabrication flaws (e.g., lack of fusion, crack, incomplete penetration, slag inclusions) representative of welding process. The flaws will be distributed throughout the examination volume. The flaw through-wall heights for the demonstration specimen will be based on the preservice acceptance standards for volumetric examination in accordance with Articles IWB-3000, IWC-3000, or IWD-3000, as applicable, of the ASME BPV Code,Section XI.
At least 30 percent of the flaws will be classified as acceptable planar flaws, with the smallest flaws being at least 50 percent of the maximum allowable size based on the applicable aspect ratio for the flaw.
Personnel will be qualified for detection and sizing fabrication flaws by performance demonstration using a blind test (i.e., the flaw information is not provided) with the qualified procedure.
o The demonstration specimen set will contain at least 10 flaws covering a range of sizes, positions, orientations, and types of fabrication flaws.
o To be qualified for flaw length sizing, the RMS error of the flaw lengths estimated by ultrasonic examinations, as compared with the true lengths, shall not exceed 0.25 inches for diameters nominal pipe size (NPS) 6 and smaller, and 0.75 inches for diameters larger than NPS 6 inches.
o To be qualified for flaw through-wall height sizing, the RMS error of the flaw through-wall heights estimated by ultrasonic examinations, as compared with the true through-wall heights, do not exceed 0.125 inches.
All flaws detected using angle-beam ultrasonic examinations will be treated as planar flaws and will be evaluated against the preservice acceptance standards in Articles IWB-3000, IWC-3000, and IWD-3000, as applicable, of the ASME BPV Code,Section XI.
The encoded PAUT technique will produce electronic records that permit offline analysis of images built from the data.
The NRC staff finds that the use of performance demonstration for personnel and procedure qualification and the use of encoded data provide assurance that the PAUT technique will be sufficiently rigorous to detect and size flaws in the welds. Although Articles IWB-3000, IWC-3000, and IWD-3000 of Section XI of the ASME Code allow larger flaws to remain inservice than paragraphs NB-5330, NC-5330, and ND-5330 of Section Ill of the ASME Code, the use of Section XI acceptance standards has proven to be effective for the ISI of piping welds. The NRC staff finds that the use of the Section XI acceptance standards is appropriate for the proposed alternative, as the proposed alternative is applicable to the repair and replacement activities in currently operating nuclear plants, not new plant construction.
Therefore, the NRC staff determined that the proposed alternative provides reasonable assurance that any structurally-significant fabrication defects in piping welds associated with repaired and replaced activities will be detected.
Based on the inspection and qualification requirements described in the proposed alternative, and the results of NUEG/CR-7204 and EPRI TR No. 3002010297, the NRC staff has reasonable assurance that the use of encoded PAUT, qualified as proposed by the licensee, for ferritic steel and austenitic stainless-steel piping repair and replacement welds will provide an adequate level of quality and safety.
4.0 CONCLUSION
As set forth above, the NRC staff determined that the licensees proposed alternative to use encoded PAUT in lieu of RT provides an acceptable level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(z)(1). Therefore, the NRC staff authorizes the use of the proposed alternative for the remainder of the current 10-year ISI intervals at Braidwood Units 1 and 2, Byron Unit Nos. 1 and 2, Calvert Cliffs Units 1 and 2, Clinton, Dresden Units 2 and 3, FitzPatrick, LaSalle Units 1 and 2, Limerick Units 1 and 2, NMP Units 1 and 2, Peach Bottom Units 2 and 3, Quad Cities Units 1 and 2, and Ginna, as specified in the licensees June 25, 2019, letter. In addition, the NRC staff authorizes the use of the proposed alternative for the duration of the fourth 10-year ISI interval at Clinton and the sixth 10-year ISI interval at Ginna, as specified in the licensees June 25, 2019, letter.
All other ASME Code requirements for which relief has not been specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: Ali Rezai, NRR/DMLR/MPHB Date of issuance: September 27, 2019
- by email OFFICE DORL/LPL3/PM DORL/LPL3/LA DMLR/MPHB/BC(A)*
NAME BPurnell SRohrer ABuford (JTSao for)
DATE 9/27/19 9/26/19 9/24/19 OFFICE DORL/LPL3/BC(A)
NAME LRegner DATE 9/27/19