ML20133K093
| ML20133K093 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 05/14/2020 |
| From: | Nancy Salgado NRC/NRR/DORL/LPL3 |
| To: | Bryan Hanson Exelon Generation Co, Exelon Nuclear |
| Weibe J | |
| References | |
| EPID L-2019-LLR-0081 | |
| Download: ML20133K093 (15) | |
Text
May 14, 2020 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 - RELIEF FROM THE REQUIREMENTS OF THE ASME CODE (EPID L-2019-LLR-0081)
Dear Mr. Hanson:
By letter dated August 27, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19239A156), as supplemented by letter dated January 29, 2020 (ADAMS Accession No. ML20029F011), Exelon Generation Company, LLC (Exelon, the licensee) submitted a request to the U.S. Nuclear Regulatory Commission (NRC or Commission) for relief from certain American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, requirements at Braidwood Station, Units 1 and 2.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),
the licensee requested relief for inservice inspection (ISI) items on the basis that the code requirement is impractical.
As set forth in the enclosed safety evaluation, the NRC staff has determined that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest, given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Furthermore, the NRC staff concluded that the examinations performed to the extent practical provide reasonable assurance of structural integrity of the subject components. Accordingly, the NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii). Therefore, the NRC staff grants relief from the ASME Code examination requirements for the welds included in RR I3R-18 for Braidwood, Units 1 and 2, for the third 10-year ISI interval.
All other ASME Code,Section XI, requirements for which relief was not specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
B. Hanson If you have any questions, please contact the Senior Project Manager, Joel S. Wiebe at 301-415-6606 or via e-mail at Joel.Wiebe@nrc.gov.
Sincerely, Digitally signed by Nancy Nancy L. L. Salgado Date: 2020.05.14 12:50:57 Salgado -04'00' Nancy L. Salgado, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-456 and STN 50-457
Enclosure:
Safety Evaluation cc: ListServ
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST I3R-18 REGARDING IMPRACTICAL INSPECTIONS EXELON GENERATION COMPANY, LLC BRAIDWOOD STATION UNITS 1 AND 2 DOCKET NOS. STN 50-456 AND STN 50-457
1.0 INTRODUCTION
By letter dated August 27, 2019, as supplemented by letter dated January 29, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML19239A156 and ML20029F011), Exelon Generation Company, LLC (Exelon, the licensee), submitted relief request (RR) I3R-18 to the U.S. Nuclear Regulatory Commission (NRC or Commission) for the second and third periods of the third 10-year inservice interval at Braidwood Station (Braidwood),
Units 1 and 2. With its submittal of RR I3R-18, the licensee requested relief from the examination coverage requirements of Section XI, Rules for Inservice Inspection [ISI] of Nuclear Power Plant Components, of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), applicable to certain ASME Code Class 1 and 2 component welds and examinations for the Braidwood, Units 1 and 2.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),
the licensee requested relief on the basis that achieving the ASME Code-required volumetric examination coverage for the subject welds in RR I3R-18 is impractical.
2.0 REGULATORY EVALUATION
Regulation 10 CFR 50.55a(g)(4), Inservice Inspection (ISI) Standards Requirement for Operating Plants, requires that components (including supports) that are classified as ASME Code Class 1, Class 2, and Class 3 must meet the requirements in 10 CFR50.55a throughout the service life of a boiling- or pressurized-water reactor. The exception is the design and access provisions and preservice examination requirements set forth in Section XI of editions and addenda of the ASME Code that become effective subsequent to editions specified in paragraphs (g)(2) and (3) of 10 CFR 50.55a, which are incorporated by reference in paragraph (a)(1)(ii) of 10 CFR 50.55a to the extent practical within the limitations of design, geometry, and materials of construction of the components.
Regulation 10 CFR 50.55a(g)(4)(ii), Applicable ISI Code: Successive 120-month Intervals, requires that inservice examination of components and system pressure tests conducted during successive 120-month inspection intervals must comply with the requirements of the latest edition and addenda of the ASME Code incorporated by reference in paragraph (a) of 10 CFR 50.55a 12 months before the start of the 120-month inspection interval or the optional ASME Enclosure
Code Cases listed in NRC Regulatory Guide (RG) 1.147, Inservice Inspection Code Case Acceptability (Revision 18 at ADAMS Accession No. ML16321A336), when using ASME Code,Section XI, as incorporated by reference in paragraph (a)(3)(ii) of 10 CFR 50.55a, subject to the conditions listed in paragraph (b) of 10 CFR 50.55a.
Regulation 10 CFR 50.55a(g)(5)(iii), ISI Program Update: Notification of Impractical ISI Code Requirements, requires that, if the licensee has determined that conformance with an ASME Code requirement is impractical for its facility, the licensee must notify the NRC and submit, as specified in Section 50.4, information to support the determinations. Determinations of impracticality in accordance with 10 C FR50.55a(g)(5)(iii) must be based on the demonstrated limitations experienced when attempting to comply with the ASME Code requirements during the ISI interval for which the request is being submitted. Requests for relief made in accordance with 10 CFR 50.55a(g)(5)(iii) must be submitted to the NRC no later than 12 months after the expiration of the initial or subsequent 120-month inspection interval for which relief is sought.
Regulation 10 CFR 50.55a(g)(6)(i), Impractical ISI Requirements: Granting of Relief, states that the Commission will evaluate determinations under paragraph (g)(5) of 10 CFR 50.55a that ASME Code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines are authorized by law, will not endanger life or property or the common defense and security, and are otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request and the NRC to grant the relief requested by the licensee.
3.0 TECHNICAL EVALUATION
3.1 The Licensees Relief Request (RR) [or Proposed Alternative][or Proposed Use of Later Code Editions and Addenda]
The licensees RR I3R-18 is for multiple ASME Code, Class 1 and Class 2 component welds associated with multiple ASME Code, Examination Categories, for the Braidwood, Units 1 and 2, third 10-year ISI interval. Exelon indicated that for the welds that are the subject of RR I3R-18, it was impractical to meet the ASME Code-required examination volumes. Specifically, due to original design of these components, it was not possible to effectively perform the examination to the extent required by the ASME Code. The ASME Code conformance would require extensive structural modifications to the components or surrounding structures. Exelon further stated that a significant effort would be needed to implement these modifications without a compensating increase in the level of quality and safety.
The licensee indicated that it performed the ASME Code-required examinations to the maximum extent possible or best effort. Due to physical limitation there are no viable alternative examination techniques currently available to increase the coverage. Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief on the basis that achieving the ASME Code-required volumetric examination coverage for the subject components in RR I3R-18 is impractical.
The ASME Code of Record at Braidwood, Units 1 and 2, for the third 10-year ISI interval is the 2001 Edition through the 2003 Addenda of ASME Code,Section XI. The third 10-year ISI
intervals at Braidwood, Units 1 and 2, ended on August 28, 2018, and November 4, 2018, respectively. Additionally, the licensee stated that Braidwood adopted ASME Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 Welds,Section XI, Division 1, which defines essentially 100 percent, as greater than 90 percent coverage of the examination volume or surface area, as applicable. ASME Code Case N-460 is an NRC-approved alternative that can be used by licensees as referenced in RG 1.147, Revision 18.
For clarity, the NRC staffs evaluation of RR I3R-18 is documented below according to each of the applicable ASME Code-required examination categories.
3.2 NRC Staff Evaluation 3.2 Examination Category B-D and C-A Volumetric Examinations 3.2.1 Applicable ASME Code Requirements The examination requirements for Examination Category B-D, Item Nos. B3.110 and B3.140, are provided in Table IWB-2500-1. The examination requirements for Examination Category C-A, Item No. C1.30, are provided in Table IWC-2500-1. For Item Nos. B3.110, B3.140, and C1.30, the required examination consists of essentially 100 percent volumetric examination.
The required examination volumes for B3.110 and B3.140 are delineated in ASME Code,Section XI, Figure IWB-2500-7. The required examination volume for C1.30 is delineated in ASME Code,Section XI, Figure IWC-2500-2. The tables below provide a summary of the examination results for Braidwood, Units 1 and 2, Examination Category B-D and C-A, examinations for which the licensee is seeking relief.
Table 1 - Examination Category B-D Welds with Limited Volumetric Coverage Braidwood, Unit 1 Component Diameter/
Item Limitation/ Examination Identification and Thickness Materials No. Coverage Results System (inch) 1PZR-01-N1 Examination Nozzle N1-to- limited due to Ferritic Low No Recordable B3.110 14 / 3.1 Pressurizer Shell Obstruction, Alloy Steel Indications Weld 74.7% coverage 1PZR-01-N1-N4A Examination Nozzle N4A-to- limited due to Ferritic Low No Recordable B3.110 6 / 3.1 Pressurizer Shell Configuration Alloy Steel Indications Weld 68.7% coverage
Table 2 - Examination Category B-D and C-A Welds and Examinations with Limited Volumetric Coverage Braidwood, Unit 2 Component Diameter/
Item Limitation/Cover Examination Identification and Thickness Materials No. age Results System (inch) 2PZR-01-N4B Examination Nozzle N4B-to- limited due to Ferritic Low No Recordable B3.110 91.5 / 2.01 Pressurizer Shell Configuration Alloy Steel Indications Weld 88.5% coverage 2PZR-01-N4C Examination Nozzle N4C-to- limited due to Ferritic Low No Recordable B3.110 91.5 / 2.01 Pressurizer Shell Configuration Alloy Steel Indications Weld 88.5% coverage Examination 2PZR-01-N1 limited due to Nozzle N1-to- Ferritic Low No Recordable B3.110 Obstruction and 26.1 / 2.56 Pressurizer Shell Alloy Steel Indications Configuration, Weld 59.2% coverage 2SG-01-SGN-01A Examination Ferritic Low Primary Nozzle limited due to No Recordable B3.140 29 / 3.19 Alloy Cast Inner Radius Obstruction Indications Steel Section 85%coverage Examination 2SG-01-SGC-02 limited due to Ferritic Low No Recordable C1.30 Tubesheet-to- 11.3 / 3.31 Configuration Alloy Steel Indications Barrel Weld 88.4% coverage 3.2.2 Licensees Reason for Request Due to the original design of these components, the licensee stated that it was not possible to obtain the ASME Code-required examination coverage for volumetric examinations for the pressure vessel welds and inner radius identified in Attachment 7 of its submittal dated January 7, 2020 (ADAMS Accession No. ML20029F011). The licensee stated that the subject welds and inner radius section were examined to the maximum extent possible. However, due to physical interferences it was not possible to examine essentially 100 percent of the required examination volume. The licensee stated that there were no instances where these components could have been conditioned to obtain the required examination coverage without major modification to the components. The summary of the examination results for Braidwood, Units 1 and 2, Examination Category B-D and C-A, welds and examinations for which the licensee is seeking relief are provided in Tables 1 and 2.
Braidwood, Unit 1, welds 1PZR-01-N1 and 1PZR-01-N4A are pressurizer-to-nozzle welds.
These welds are ferritic low alloy steel with limited access and due to configuration and obstructions ultrasonic (UT) examinations did not achieve essentially 100 percent coverage.
Due to these limitations, UT examinations for welds 1PZR-01-N1 and 1PZR-01-N4A resulted in achieving 74.7 and 68.6 percent of the required examination volume respectively of each of these welds.
Braidwood, Unit 2, welds 2PZR-01-N4B, 2PZR-01-N4C, and 2PZR-01-N1, are pressurizer-to-nozzle welds. Braidwood, Unit 2, weld 2SG-01-SGC-02, is a steam generator (SG) tubesheet-to-barrel weld, and 2SG-01-SGN-01A SG primary nozzle inner radius section. These components are all ferritic low alloy steel with limited access and due to configuration and obstructions UT examinations did not achieve essentially 100 percent coverage. Due to these limitations UT examinations for welds 2PZR-01-N4B, 2PZR-01-N4C, 2PZR-01-N1, and 2SG SGC-02, and primary nozzle inner radius section 2SG-01-SGN-01A, resulted in achieving 85.5, 85.5, 59.2, 88.4 and 85 percent of the required examination volume respectively. There were no recordable indications or flaws recoded as a result of these volumetric examinations for Braidwood, Units 1 and 2.
3.2.3 NRC Staff Evaluation of Category B-D and C-A Volumetric Examinations Examination requirements of Examination Category B-D, Item Nos. B3.110 and B3.140, require essentially 100 percent volumetric examinations covering the examination volume delineated in ASME Code,Section XI, Figure IWB-2500-7. Examination requirements of Examination Category C-A, Item No. C1.30, require essentially 100 percent volumetric examinations covering the examination volume delineated in ASME Code,Section XI, Figure IWC-2500-2.
The volumetric examinations were performed in accordance with Mandatory Appendix I of the ASME Code,Section XI, which requires UT examination of vessel welds greater than 2 inches thick to be conducted in accordance with ASME Section V, Article 4. However, licensees volumetric examinations are restricted by component design, materials and weld configurations.
These conditions precluded the licensee from obtaining full access to these welds, resulting in limited volumetric examinations. To gain access for achieving examination coverage for the required examination volumes, the subject welds would require design modifications. This would place a burden on the licensee, therefore obtaining essentially 100 percent of ASME Code-required volumetric examinations for the subject components is considered impractical.
As shown in the sketches and technical descriptions included in the licensees submittals for Braidwood, Units 1 and 2, the subject components have access limitations which resulted in reduced volumetric examination coverage. The UT examinations for Braidwood, Unit 1, welds 2PZR-01-N4B and 2PZR-01-N4C resulted in UT examination coverage of 74.7 and 68.7 percent, respectively, with no recordable indications. The volumetric examinations of Braidwood, Unit 2, welds 2PZR-01-N4B, 2PZR-01-N4C, 2PZR-01-N1, and 2SG-01-SGC-02, resulted in achieving 85.5, 85.5, 59.2, and 85 percent of the required examination volume respectively, with no recordable indications. Additionally, the volumetric examination of inner radius section 2SG-01-SGN-01A, resulted in achieving 88.5 percent of the required volume, with no recordable indications. These volumetric examinations were performed in accordance with ASME Code,Section V, Article 4, and supplemented with the additional requirements delineated in Table I-2000-1.
Based on the aggregate coverage obtained for the subject components, the extent of the examinations, and considering the licensees performance of essentially 100 percent examination coverage for the accessible portions of these welds, it is reasonable to conclude that had significant flaws been present in these welds, some evidence of unacceptable flaws would have been detected by the licensee. Therefore, the NRC staff determined that the examinations performed provide reasonable assurance of structural integrity of the subject Braidwood, Units 1 and 2, components.
Based on its review of the subject Examination Category B-D and C-A welds and components at Braidwood, the NRC staff finds that it is impractical to meet the ASME Code-required examination coverage for the subject welds due to the original design configuration for the subject welds and components. The NRC staff also determined that the UT examinations performed, despite the limited coverage obtained by the licensee, provide reasonable assurance of the structural integrity for the subject components. Furthermore, the continued performance of the required VT-2 examinations through the system pressure tests provide additional assurance of structural integrity of the subject piping components. Hence, the staff finds that the risk associated with granting the requested relief would be very low. Therefore, the staff finds the licensees request acceptable.
3.3 Examination Category R-A, Item Nos. R1.11 and R1.20, Pressure-Retaining Welds in Piping 3.3.1 Applicable ASME Code Requirements The examination requirements for Examination Category R-A, Item Nos. R1.11 and R1.20, are derived from the licensees risk-informed (RI) ISI program and ASME Code Case N-578-1, Alternative Piping Classification and Examination Requirements,Section XI, Division 1. NRC approved the licensees RI ISI program for the third ISI interval by letter dated November 5, 2009 (ADAMS Accession No. ML093070271). For Items Nos. R1.11 and R1.20, the required examination consists of essentially 100 percent volumetric examination. The required examination volume is delineated in ASME Code,Section XI, Figure IWC-2500-7(a). For reference purposes it is noted that Item No. R1.11 is reserved for components that are subject to thermal fatigue while Item No. R1.20 components do not have a known damage mechanism.
The tables below provide a summary of the examination results for Braidwood, Units 1 and 2, Examination Category R-A, welds for which the licensee is seeking relief.
Table 3 - Examination Category R-A Welds with Limited Volumetric Coverage Braidwood, Unit 1 Component Pipe Item Limitation/Cover Examination Identification and Size Materials No. age Results System (inch)
Single sided 1SI-39-08 Austenitic No Recordable R1.20 Elbow-to-Valve, 4 Safety Injection Stainless Steel Indications 50% coverage Single sided 1SI-39-08A Austenitic No Recordable R1.20 Valve-to-Pipe, 4 Safety Injection Stainless Steel Indications 50% coverage Single sided 1SI-39-25 Austenitic Acceptable R1.20 Elbow-to-Valve, 4 Safety Injection Stainless Steel Indications Noted 50% coverage Single sided 1SI-39-25A Austenitic No Recordable R1.20 Valve-to-Pipe, 4 Safety Injection Stainless Steel Indications 50% coverage Single sided 1SI-39-25B Austenitic No Recordable R1.20 Pipe-to-Valve, 4 Safety Injection Stainless Steel Indications 50% coverage
Table 3 - Examination Category R-A Welds with Limited Volumetric Coverage Braidwood, Unit 1 Component Pipe Item Limitation/Cover Examination Identification and Size Materials No. age Results System (inch) 1CV-22-30 Single sided (1CV109-4/FW-1) Austenitic No Recordable R1.20 Valve-to-Pipe, 4 Chemical Volume Stainless Steel Indications 50% coverage Control Table 4 - Examination Category R-A Welds with Limited Volumetric Coverage Braidwood, Unit 2 Component Pipe Item Limitation/Cover Examination Identification and Size Materials No. age Results System (inch)
Single sided 2SI-39-11 Austenitic No Recordable R1.20 Elbow-to-Valve, 4 Safety Injection Stainless Steel Indications 50% coverage Single sided 2SI-39-11A Austenitic No Recordable R1.20 Valve-to-Pipe, 4 Safety Injection Stainless Steel Indications 50% coverage Single sided Indication due to 2SI-39-28 Austenitic R1.20 Elbow-to-Valve, 4 inside surface Safety Injection Stainless Steel 50% coverage geometry Single sided 2SI-39-28A Austenitic No Recordable R1.20 Valve-to-Pipe, 4 Safety Injection Stainless Steel Indications 50% coverage Single sided 2SI-39-28B Austenitic Indication due to R1.20 Pipe-to-Valve, 4 Safety Injection Stainless Steel root geometry 50% coverage Elbow-to-SG 2FW-09-25 Low Alloy No Recordable R1.11 Nozzle Weld 6 Feedwater Ferritic Steel Indications 87% coverage Elbow-to-Flange 2AF-03-23 (FW-1) Low Alloy Indication due to R1.20 Weld 4 Auxiliary Feedwater Ferritic Steel root geometry 87% coverage Flange-to-Elbow 2AF-03-24 (FW-2) Low Alloy Indication due to R1.20 Weld 4 Auxiliary Feedwater Ferritic Steel root geometry 87% coverage Indications due to Elbow-to-Flange 2AF-04-20 (FW-3) Low Alloy root and inside R1.20 Weld 4 Auxiliary Feedwater Ferritic Steel diameter 88% coverage geometry
Table 4 - Examination Category R-A Welds with Limited Volumetric Coverage Braidwood, Unit 2 Component Pipe Item Limitation/Cover Examination Identification and Size Materials No. age Results System (inch)
Indications due to Flange-to-Elbow 2AF-04-21 (FW-4) Low Alloy root and inside R1.20 Weld 4 Auxiliary Feedwater Ferritic Steel diameter 88% coverage geometry Elbow-to-Flange 2AF-02-23 (FW-1) Low Alloy No Recordable R1.20 Weld 4 Auxiliary Feedwater Ferritic Steel Indications 90% coverage Flange-to-Elbow 2AF-02-24 (FW-2) Low Alloy Indication due to R1.20 Weld 4 Auxiliary Feedwater Ferritic Steel root geometry 90% coverage Elbow-to-Flange 2AF-01-24 (FW-3) Low Alloy Indication due to R1.20 Weld 4 Auxiliary Feedwater Ferritic Steel root geometry 90% coverage Flange-to-Elbow 2AF-01-25 (FW-4) Low Alloy Indication due to R1.20 Weld 4 Auxiliary Feedwater Ferritic Steel root geometry 89% coverage 2CV-21-58 (FW-1) Valve-to-Tee Austenitic No Recordable R1.20 Chemical Volume Weld 4 Stainless Steel Indications Control 20%
Tee-to-Pipe Weld Austenitic Indication due to R1.20 Chemical Volume 4 83% coverage Stainless Steel root geometry Control 2CV-21-56(FW-2)
Pipe-to-Tee Weld Austenitic No Recordable R1.20 Chemical Volume 4 83% coverage Stainless Steel Indications Control 3.3.2 Licensees Reason for Request Due to materials of fabrication and component design limitations, the licensee stated that it was not possible to obtain the ASME Code-required examination coverage for volumetric examinations for the piping welds identified in Attachment 7 of its submittal dated January 7, 2020 (ADAMS Accession No. ML20029F011), without extensive design modifications. The licensee stated that the subject welds were examined to the extent practical due to the lack or limited access. The licensee further stated that 100 percent of the accessible welds were examined. The UT examinations were performed using personnel, equipment and procedures qualified in accordance with ASME Code,Section XI, Appendix VIII, as implemented by the Performance Demonstration Initiative (PDI). The ASME Code-required volume for these welds was examined ultrasonically to the maximum extent possible. The summary of the examination results for Braidwood, Units 1 and 2, Examination Category R-A, welds for which the licensee is seeking relief are provided in Tables 3 and 4, respectively.
Braidwood, Unit 1, welds 1SI-39-08, 1SI-39-08A, 1SI-39-25, 1SI-39-25A, and 1SI-39-25B, are safety injection piping welds, and weld 1CV-22-30 (1CV109-4/FW-1) weld is a chemical volume
control piping weld. All of these welds are austenitic stainless steel piping component-to-valve welds with limited access, only a single side access was available during UT examinations.
Therefore, due to the configuration of these components, circumferential and axial scanning was performed from the pipe side only for these welds. This resulted in credited UT examination coverage of 50 percent for the six subject Braidwood, Unit 1, piping welds. There were no recordable indications for welds 1SI-39-08, 1SI-39-08A, 1SI-39-25A, 1SI-39-25B, and 1CV-22-30 (1CV109-4/FW-1). Weld 1SI-39-25 had a root geometry indication as well as an embedded flaw (subsurface) that was determined to be acceptable per ASME Code,Section XI, IWB-3514. Additionally, the weld was examined by radiography and was also deemed acceptable.
Braidwood, Unit 2, welds 2SI-39-11, 2SI-39-11A, 2SI-39-28, 2SI-39-28A, and 2SI-39-28B, are safety injection piping welds, and welds 2CV-21-58(FW-1), 2CV-21-57(FW-2), and 2CV-21-56(FW-2), are chemical volume control piping welds. All of these welds are austenitic stainless steel piping-to-valve, piping-to-fitting, or valve-to-fitting welds with limited access which resulted in reduced examination coverage. With the exception of weld 2CV-21-58(FW-1), the examination coverage obtained for these welds ranged from 50 to 83 percent of the required examination volume; no flaws were recorded during these volumetric examinations.
The configuration for weld 2CV-21-58(FW-1) resulted in more limitations which resulted in further reduction to access; therefore, the examination coverage was limited to 20 percent with no recordable indications.
The following welds make up the balance of the Examination Category R-A welds for Braidwood, Unit 2, in the licensees submittal: welds 2FW-09-25, 2F-03-23(FW-1),
2AF-03-24(FW-2), 2AF-04-20(FW-3), 2AF-04-21(FW-4), 2AF-02-23(FW-1), 2AF-02-24(FW-2),
2AF-01-24(FW-3), and 2AF-01-25(FW-4). These are low alloy ferritic steel feedwater or auxiliary feedwater piping-to-fitting or fitting-to-fitting welds for which due to geometry constraints, the license was not able to achieve the ASME Code-required examination coverage (i.e., essentially 100 percent). However, the licensee was able to achieve 87 to 90 percent of the required examination volume. Other than the acceptable geometric indications noted in Table 3, there were no recordable indications or flaws recoded as a result of these volumetric examinations.
3.3.3 NRC Staff Evaluation of Examination Category R-A Welds Examination requirements of ASME Code Case N-578-1, Examination Category R-A, Items Nos. R1.11 and R1.20, require essentially 100 percent volumetric examinations covering the examination volume delineated in ASME Code,Section XI, Figure IWC-2500-7(a). However, licensees volumetric examinations are restricted by component design, materials and weld configurations. These conditions precluded the licensee from obtaining full access from both sides of these welds, resulting in limited volumetric examinations. To gain access for achieving examination coverage for the required examination volumes, the subject welds would require design modifications. This would place a burden on the licensee, therefore, obtaining essentially 100 percent of ASME Code-required volumetric examinations for the subject welds is considered impractical.
As shown in the sketches and technical descriptions included in the licensees submittals for Braidwood, Unit 1, the subject welds are all austenitic stainless steel piping welds with geometric limitations that restricted performing ultrasonic scanning from both sides of the welds.
However, volumetric examinations on the subject welds were conducted with equipment,
procedures and personnel that were qualified to a performance demonstration process outlined in the ASME Code,Section XI, Appendix VIII. These techniques have been qualified through the industrys PDI, which meets the intent of the ASME Code,Section XI, Appendix VIII, requirements for flaws located on the near-side of the welds; far-side detection of flaws is considered to be a best effort. The NRC staff finds that the licensees achieved examination coverage constitutes a best effort, and is considered justified.
For Braidwood, Unit 1, welds 1SI-39-08, 1SI-39-08A, 1SI-39-25A, 1 SI-39-25B, and 1CV-22-30 (1CV109-4/FW-1), the licensee obtained 50 percent coverage with no recordable indications.
The UT techniques employed for these welds met the ASME Code,Section XI, Appendix VIII, requirements for austenitic stainless steel welds. As stated earlier, they have been qualified for flaws located on the near-side, not the far-side of the welds. The far-side detection of flaws is considered to be a best effort. However, the NRC staff expects that had significant flaws been present on the far side they would have been detected by the licensee.
For weld 1SI-39-25, the licensee did detect an embedded weld flaw which was found to be acceptable by ASME Code,Section XI, IWB-3514, examination acceptance evaluation. The flaw was detected by the 45 and 60 degrees shear wave examination but was not detectable by 60 degree and zero degree longitudinal examinations. The weld was also radiographed; however, the flaw was not detectable by radiography. The licensees use of longitudinal-waves, which have been shown to provide enhanced detection on the far-side of austenitic stainless steel welds, confirmed that the flaw was limited in size. Therefore, while the licensee took credit only for the near side of the weld (i.e., limited volumetric coverage), the NRC staff expects that the techniques employed by the licensee would have provided some coverage beyond the near-side into the far-side of this weld.
The NRC staff finds that for the Braidwood, Unit 1, welds 1SI-39-08, 1SI-39-08A, 1SI-39-25, 1SI-39-25A, 1 SI-39-25B, and 1CV-22-30 (1CV109-4/FW-1), the licensee has demonstrated that due to geometric limitations it was impractical to meet the ASME Code-required essentially 100 percent volumetric examination coverage for the subject piping welds during its third 10-year ISI Interval. Although the ASME Code-required coverage could not be obtained, the UT techniques employed provided nearly full volumetric coverage from the near side of the welds, which also provides some limited volumetric coverage for the weld materials on the opposite (far) side of these welds. Based on the aggregate coverage obtained for the subject welds, the extent of the examinations, and considering the licensees performance of essentially 100 percent examination coverage for the accessible portions of these welds, it is reasonable to conclude that had significant flaws been present in these welds, some evidence of unacceptable flaws would have been detected by the licensee. Furthermore, the NRC staff determined that the examinations performed provide reasonable assurance of structural integrity of the subject Braidwood, Unit 1, welds 1SI-39-08, 1SI-39-08A, 1SI-39-25, 1SI-39-25A, 1 SI-39-25B, and 1CV-22-30 (1CV109-4/FW-1).
Braidwood, Unit 2, welds 2SI-39-11, 2SI-39-11A, 2SI-39-28, 2SI-39-28A, 2SI-39-28B, 2CV-21-57 (FW-2), and 2CV-21-569(FW-2), are all austenitic stainless steel with access limitations which resulted in reduced examination coverage. For these welds the licensee was able to achieve examination coverage which ranged from 50 to 83 percent of the ASME Code-required examination volume. Service induced flaws or fabrication defects were not detected for these welds. Although the ASME Code-required coverage could not be obtained, the UT techniques employed by the licensee provided nearly full volumetric coverage from the near-side of the welds. NRC staff expects, based on the limited volumetric coverage for the weld materials on the opposite (far) side of these welds, had significant flaws been present, the
licensee would have been able to detect them. Based on the aggregate coverage obtained for the subject austenitic stainless steel welds, the extent of the examinations, and considering the licensees performance of essentially 100 percent examination coverage for the accessible portions of these welds, it is reasonable to conclude that had significant flaws been present in these welds, they would have been detected by the licensee. Therefore, the NRC staff determined that the examinations performed provide reasonable assurance of structural integrity of the subject Braidwood, Unit 2, welds 2SI-39-11, 2SI-39-11A, 2SI-39-28, 2SI-39-28A, 2SI-39-28B, 2CV-21-57 (FW-2), and 2CV-21-56(FW-2).
Braidwood, Unit 2, weld 2FW-09-25 is a 6 inch low alloy ferritic steel elbow-to-SG feedwater nozzle weld. The licensee performed this volumetric examination using 45, 60, and 70 degrees shear wave examinations with no recordable indications. However, due to limited access it was able to achieve 87 percent of the ASME Code-required volumetric examination coverage.
Braidwood, Unit 2, welds 2F-03-23(FW-1), 2AF-03-24(FW-2), 2AF-04-20(FW-3), 2AF 21(FW-4), 2AF-02-23(FW-1), 2AF-02-24(FW-2), 2AF-01-24(FW-3), and 2AF-01-25(FW-4), are all 4 inch low alloy ferritic steel welds in the auxiliary feedwater piping system. The licensee performed these volumetric examinations using 45, 60, and 70 degrees shear wave examinations, no recordable indications were noted during these examinations, other than weld root geometry. However due to access limitations, the licensee was able to volumetrically examine 87 to 90 percent of the ASME Code-required examination volume for these welds.
The NRC staff finds that it was impractical to meet the ASME Code-required examination volume for these ferritic low alloy welds due to access limitations. However, based on the significant volume of coverage obtained (over 87 percent), if significant or unacceptable flaws were present in these welds, they would have been detected by the examinations performed by the licensee. Additionally, the staff determined that the examinations performed provide a reasonable assurance of structural integrity of the subject welds.
Based on its review of the subject Examination Category R-A welds at Braidwood, the NRC staff finds that it is impractical to meet the ASME Code-required examination coverage for the subject welds due to the design configuration and materials of construction of the welds. The NRC staff also determined that the UT examinations performed, despite the limited coverage obtained by the licensee, provide reasonable assurance of the structural integrity for the subject Examination Category R-A welds. Furthermore, the continued performance of the required VT-2 examinations through the system pressure tests provide additional assurance of structural integrity of the subject piping components. Hence, the staff finds that the risk associated with granting the requested relief would be very low. Therefore, the NRC staff finds the licensees request acceptable.
4.0 CONCLUSION
As set forth above, the NRC staff has determined that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest, given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Furthermore, the NRC staff concluded that the examinations performed to the extent practical provide reasonable assurance of structural integrity of the subject components. Accordingly, the NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii). Therefore, the NRC staff grants relief from the ASME Code examination requirements for the welds included in RR I3R-18 for Braidwood, Units 1 and 2, for the third 10-year ISI interval.
All other ASME Code,Section XI, requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributors: G. Cheruvenki R. Kalikian Date: May 14, 2020
ML20133K093 *email OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA DNRL/NPHP/BC NRR/DORL/LPL3/BC NAME JWiebe* SRohrer MMitchell* NSalgado DATE 05/12/2020 05/13/2020 c/ 04/20/2020 05/14/2020