Letter Sequence Approval |
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EPID:L-2021-LLR-0019, Request for Alternative, 21-ISI-1 Alternative Repair and Examination for Mid Canopy Seal Weld Replacement (Approved, Closed) |
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Category:Letter
MONTHYEARML24032A0202024-01-31031 January 2024 NPDES Biocide/Corrosion Treatment Plan Annual Report, Cy 2023 ML23319A2452024-01-29029 January 2024 Issuance of Amendment Nos. 366 and 360; 164 and 71 Regarding the Adoption of TSTF-567, Revision 1, Add Containment Sump TS to Address GSI-191 Issues CNL-24-017, Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure and Emergency Preparedness Department Procedure Revisions2024-01-17017 January 2024 Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure and Emergency Preparedness Department Procedure Revisions ML24018A0142024-01-17017 January 2024 Engine Systems, Inc., Report No. 10CFR21-0137, Rev. 1, 56913-EN 56913 ML24011A3182024-01-11011 January 2024 Submittal of Discharge Monitoring Report (Dmr), October 2023 ML24011A3172024-01-11011 January 2024 Submittal of Discharge Monitoring Report (Dmr), September 2023 ML24011A3202024-01-11011 January 2024 Submittal of Discharge Monitoring Report (Dmr), December 2023 ML24011A3162024-01-11011 January 2024 Submittal of Discharge Monitoring Report (Dmr), August 2023 ML24011A3192024-01-11011 January 2024 Submittal of Discharge Monitoring Report (Dmr), November 2023 IR 05000327/20234422024-01-11011 January 2024 95001 Supplemental Inspection Report 05000327/2023442 and 05000328/2023442 and Follow-Up Assessment Letter ML24010A2132024-01-10010 January 2024 CFR 21.21 Final Report Regarding Siemens Medium Voltage Circuit Breakers ML24018A0952024-01-0404 January 2024 Engine Systems, Inc., 10CFR21 Reporting of Defects and Non-Compliance Report No. 10CFR21-0137, Rev. 0 ML24004A0332024-01-0303 January 2024 Interim Report of a Deviation or Failure to Comply Crompton Instruments Type 077 Ammeter ML24004A0402024-01-0303 January 2024 Response to NRCs November 8, 2023, Request for Additional Information - Related to Independent Spent Fuel Storage Installation CNL-23-068, Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation2023-12-21021 December 2023 Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation CNL-23-036, Application to Revise Function 5 of Technical Specification Table 3.3.2-1, Engineered Safety Feature Actuation System Instrumentation, for the Sequoyah Nuclear Plant and Watts Bar Nuclear Plant (SQN-TS-23-02 and WBN-TS-23-08)2023-12-18018 December 2023 Application to Revise Function 5 of Technical Specification Table 3.3.2-1, Engineered Safety Feature Actuation System Instrumentation, for the Sequoyah Nuclear Plant and Watts Bar Nuclear Plant (SQN-TS-23-02 and WBN-TS-23-08) ML23346A1222023-12-12012 December 2023 Annual Non-Radiological Environmental Operating Report - 2023 IR 05000327/20234202023-11-28028 November 2023 Security Baseline Inspection Report 05000327/2023420 and 05000328/2023420 CNL-23-067, Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2023-11-27027 November 2023 Central Emergency Control Center Emergency Plan Implementing Procedure Revisions ML23324A4362023-11-0909 November 2023 Exam Corporate Notification Letter Aka 210-day Letter ML23307A0822023-11-0808 November 2023 Request for Additional Information August 4, 2022, Exemption Request for Deviating from the Conditions of Certificate of Compliance No. 1032, Amendment No. 3, Related to Sequoyah Nuclear Plant Independent Spent Fuel Storage Installation IR 05000327/20230032023-11-0303 November 2023 Integrated Inspection Report 05000327/2023003 and 05000328/2023003 ML23306A1592023-11-0202 November 2023 Enforcement Action EA-22-129 Inspection Readiness Notification ML23292A0792023-10-19019 October 2023 Tennessee Valley Authority - Emergency Plan Implementing Procedure Revision, Includes EPIP-5, Revision 58, General Emergency IR 05000327/20230112023-10-16016 October 2023 Triennial Fire Protection Inspection Report 05000327/2023011 and 05000328/2023011 ML23285A0882023-10-12012 October 2023 Submittal of Sequoyah Nuclear Plant, Units 1 and 2, Submittal of Updated Final Safety Analysis Report Amendment 31 ML23284A4252023-10-11011 October 2023 10 CFR 50.59 and 10 CFR 72.48 Changes, Tests, and Experiments Summary Report; Commitment Summary Report; and Update to the Fire Protection Report ML23283A2792023-10-10010 October 2023 Revisions to the Sequoyah Nuclear Plant Units 1 and 2 Technical Requirements Manual ML23279A0612023-10-0505 October 2023 Paragon Energy Solutions LLC, Part 21 Final Report Re Potential Defect with Eaton Jd and Hjd Series Molded Case Circuit Breakers (Mccbs) ML23277A0462023-10-0404 October 2023 Revisions to the Sequoyah Nuclear Plant Units 1 and 2 Technical Specification Bases ML23275A0272023-09-29029 September 2023 Submittal of Discharge Monitoring Report (DMR) Quality Assurance Study 43 Final Report 2023 ML23271A1662023-09-28028 September 2023 Registration of Spent Fuel Storage Cask Pursuant to 10 CFR 72.212(b)(2) CNL-23-059, Supplement to Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Units 1 and 2, Application to Revise Technical Specifications to Adopt TSTF-567-A, Revision 1, Add Containment Sump TS to Address GSI-191 Issues (SQN-TS-23-2023-09-20020 September 2023 Supplement to Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Units 1 and 2, Application to Revise Technical Specifications to Adopt TSTF-567-A, Revision 1, Add Containment Sump TS to Address GSI-191 Issues (SQN-TS-23-03 CNL-23-061, Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure Revision2023-09-20020 September 2023 Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure Revision IR 05000327/20234032023-09-14014 September 2023 Cyber Security Inspection Report 05000327/2023403 and 05000328/2023403 (Cover Letter) ML23257A0062023-09-14014 September 2023 Enforcement Action EA-22-129 Inspection Postponement Request ML23254A2192023-09-11011 September 2023 Emergency Plan Implementing Procedure Revisions ML23254A0652023-09-0707 September 2023 Registration of Spent Fuel Storage Cask Pursuant to 10 CFR 72.212(b)(2) CNL-23-057, Central Emergency Control Center Emergency Plan Implementing Procedure Revisions. Includes CECC-EPIP-1, Revision 76 and CECC-EPIP-9, Revision 642023-09-0505 September 2023 Central Emergency Control Center Emergency Plan Implementing Procedure Revisions. Includes CECC-EPIP-1, Revision 76 and CECC-EPIP-9, Revision 64 IR 05000327/20230052023-08-29029 August 2023 Updated Inspection Plan for Sequoyah Nuclear Plant, Units 1 and 2 - Report 05000327/2023005 and 05000328/2023005 ML23233A0122023-08-17017 August 2023 Unit 1 Cycle 25 Refueling Outage - 90-Day Inservice Inspection Summary Report - Supplement ML23233A0142023-08-15015 August 2023 Discharge Monitoring Report (Dmr), July 2023 ML23215A1212023-08-0303 August 2023 301 Exam Administrative Items (2B) Normal Release ML23215A1572023-08-0303 August 2023 Enforcement Action EA-22-129 Inspection Readiness Notification CNL-23-028, Application to Revise Technical Specifications to Adopt TSTF-567-A, Revision 1, Add Containment Sump TS to Address GSI-191 Issues (SQN-TS-23-03 and WBN-TS-23-06)2023-08-0202 August 2023 Application to Revise Technical Specifications to Adopt TSTF-567-A, Revision 1, Add Containment Sump TS to Address GSI-191 Issues (SQN-TS-23-03 and WBN-TS-23-06) ML23192A4472023-07-31031 July 2023 Staff Assessment of Updated Seismic Hazards at TVA Sites Following the NRC Process for the Ongoing Assessment of Natural Hazards Information 2024-01-04
[Table view] Category:Safety Evaluation
MONTHYEARML23319A2452024-01-29029 January 2024 Issuance of Amendment Nos. 366 and 360; 164 and 71 Regarding the Adoption of TSTF-567, Revision 1, Add Containment Sump TS to Address GSI-191 Issues ML23072A0652023-04-0505 April 2023 Units 1 and 2 Issuance of Amendment Nos. 364 and 358; 160 and 68 Regarding a Revision to Technical Specification 3.4.12 ML23048A3042023-03-0808 March 2023 Tennessee Valley Authority - Request for Relief from Requirements of ASME Boiler and Pressure Vessel Code Regarding Weld Examination Coverage (EPID L-2022-LLR-0045,-0046,-0047) ML22334A0732023-02-0606 February 2023 Issuance of Amendment Nos. 363 and 357 Regarding Modification of the Approved Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors ML22348A0052023-01-25025 January 2023 Issuance of Amendment Nos. 326, 349, and 309; 363 and 35; 159 and 67 Regarding Adoption of TSTF-554, Revise Reactor Coolant Leakage Requirements ML22349A6472023-01-20020 January 2023 Issuance of Amendment Nos. 325, 348, and 308; 362 and 356; and 158 and 66 Regarding Adoption of TSTF-529, Rev. 4, Clarify Use and Application Rules ML22271A9142022-12-0707 December 2022 Issuance of Amendment Nos. 324, 347, and 307; 360 and 354; 157 and 65 Regarding a Revision to the Emergency Action Level Scheme ML22304A1862022-12-0101 December 2022 Revised Authorization of Alternative Request RV-02 for Pressure Isolation Valve Seat Leakage ML22284A0072022-11-0707 November 2022 Authorization of Alternative Request RP-12 for Testing of Centrifugal Charging Pump 1B-B ML22276A1612022-10-24024 October 2022 Issuance of Amendment Nos. 359, 353, 155, & 63 Regarding Adoption of TSTF Traveler TSTF-577, Revised Frequencies for Steam Generator Tube Inspections ML22272A5682022-10-12012 October 2022 Authorization of Alternatives to Certain Inservice Testing Requirements in the American Society of Mechanical Engineers Operating and Maintenance Code ML22259A2042022-09-29029 September 2022 Correction to Amendment Nos. 358 and 352 Regarding Technical Specifications Task Force Traveler TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4B ML22263A3752022-09-29029 September 2022 Authorization of Alternative Request RV-02 for Pressure Isolation Valve Seat Leakage ML22210A1182022-08-24024 August 2022 Issuance of Amendment Nos. 358 and 352 Regarding Technical Specifications Task Force Traveler TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4B ML22165A1052022-07-12012 July 2022 Issuance of Amendment Nos. 357 and 351 Regarding Revision to Technical Specification Table 3.3.1-1, Reactor Trip System Instrumentation ML22084A0012022-04-0505 April 2022 Clinch River Nuclear Site; Sequoyah Nuclear Plant, Units 1 and 2; Watts Bar Nuclear Plant, Units 1 and 2, Review of Quality Assurance Plan Changes ML21298A0312021-10-27027 October 2021 Issuance of Exigent Amendment No. 350 Regarding One-Time Change to Technical Specification 3.4.12, Low Temperature Overpressure Protection System, ML21245A2672021-10-27027 October 2021 NON-PROPRIETARY - Sequoyah Nuclear Plant, Units 1 and 2 - Issuance of Amendment Nos. 356 and 349 Regarding the Transition to Westinghouse Robust Fuel Assembly-2 (RFA-2) Fuel ML21266A3832021-10-0101 October 2021 Authorization of Alternative Request RP-10 for the 1B-B Motor Driven Auxiliary Feedwater Pump ML21131A1632021-05-28028 May 2021 Authorization and Safety Evaluation for Alternative Request No. 21-ISI-1 ML21084A1902021-05-0404 May 2021 Issuance of Amendment Nos. 355 and 348 Regarding Revision to Technical Specification Table 3.3.3-1, Post Accident Monitoring Instrumentation ML21021A3492021-03-0303 March 2021 Issuance of Amendment Nos. 354 and 347 Regarding Revision to Technical Specification 4.2.2, Control Rod Assemblies ML20337A0372021-02-0101 February 2021 Issuance of Amendment No. 353 Regarding Steam Generator Tube Inspection Frequency ML20350B4932021-01-25025 January 2021 Issuance of Amendment Nos. 352, 346, 141, and 47 Regarding the Adoption of Technical Specification Task Force Traveler, TSTF-569, Revision 2, Revise Response Time Testing Definition ML20268A0822021-01-12012 January 2021 Issuance of Amendment Nos. 314, 337, and 297; 351 and 345; 140 and 46 Regarding Changes to the Technical Specifications ML20282A3452020-11-19019 November 2020 Issuance of Amendment Nos. 313, 336, 296, 350, 344, 138, and 44 Revise Emergency Plan On-Shift Emergency Medical Technician & Onsite Ambulance Requirements ML20262H0262020-11-12012 November 2020 Issuance of Amendment Nos. 349 and 343 Regarding Technical Specification 3.3.1, Reactor Protection System Instrumentation, Turbine Trip Function on Low Fluid Oil Pressure ML20108F0492020-04-23023 April 2020 Issuance of Amendment No. 342 Exigent Amendment to Operate One Cycle with One Control Rod Removed ML19319C8312019-11-21021 November 2019 Issuance of Exigent Amendment No. 348 to Operate One Cycle with One Control Rod Removed ML19281B5542019-11-18018 November 2019 Issuance of Amendment Nos. 347 and 341 Request to Adopt TSTF-563, Revision 0, Revise Instrument Testing Definitions to Incorporate the Surveillance Frequency Control Program ML19234A0132019-09-23023 September 2019 Alternative Request 18-ISI-1 Regarding Examination of Dissimilar Metal Welds in Reactor Vessel Head ML19179A1352019-09-18018 September 2019 Issuance of Amendment Nos. 346 and 340, Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Structures, Systems, and Components for Nuclear Power Reactors ML18277A1102019-08-27027 August 2019 Units, 1 & 2 Issuance of Amendment Nos. 309, 332, 292, 345, 339, 128, and 31 Regarding Unbalanced Voltage Protection ML19227A1102019-08-26026 August 2019 Alternative Request for the Turbine Driven Auxiliary Feedwater Pumps 10-Year Interval Inservice Testing Program ML19196A2212019-07-18018 July 2019 Issuance of Exigent Amendment Technical Specification Change - Reactor Vessel Level Instrumentation Inoperable ML19058A0292019-05-0707 May 2019 Issuance of Amendments Request to Modify Essential Raw Cooling Water Control Center Breakers and to Revise the Updated Final Safety Analysis Report (SQN-TS-17-04) ML19010A2742019-03-18018 March 2019 Final Safety Evaluation by the Office of Nuclear Reactor Regulation Topical Report- TVA Overall Basin Probable Maximum Precipitation and Local Intense Precipitation, Calculation, CDQ0000002016000041 Tennessee Valley Authority ML18197A3072018-08-30030 August 2018 Issuance of Amendments Regarding Request to Change Technical Specification 3.3.1 and Surveillance Requirement 3.2.4 ML18159A4612018-08-0606 August 2018 Issuance of Amendments Regarding Request to Change Emergency Plan ML18138A4522018-05-29029 May 2018 Bf, Units 1, 2, and 3; Sequoyah, Units 1 and 2; Watts Bar, Units 1 and 2 - Correction to an Omitted Reference for License Amendment Regarding Request to Upgrade (CAC Nos. MF9054, MF9055, MF9056, MF9057, MF9058, MF9059, and MF9060, EPID L-20 ML17289A0322017-12-22022 December 2017 Issuance of Amendments Regarding Request to Upgrade Emergency Action Level Scheme (CAC Nos. MF9054-60; EPID L2017-LLA-0160) ML17034A3602017-03-27027 March 2017 Issuance of Amendment Nos. 298, 322, 282, and 338 and 331 - Revise Technical Specification 5.3, Unit Staff Qualifications to Replace References to Rg 1.8, Rev. 2 with TVA Nuclear Quality ... ML16340A0092017-03-0909 March 2017 Safety Evaluation Regarding Implementation of Mitigation Strategies and Reliable Spent Fuel Pool Instrumentation Related to Orders EA-12-049 and EA-12-051 ML17059B7912017-03-0202 March 2017 Sequoyah Nuclear Plant, Units 1 and 2 - Relief from the Requirements of the American Society of Mechanical Engineer OM Code (CAC Nos. MF9305 and MF9306) ML16228A0962016-10-0303 October 2016 Issuance of Amendments to Change the Completion Date of Cyber Security Plan Implementation Milestone 8 ML16225A2762016-09-29029 September 2016 Issuance of Amendments to Revise Technical Specification for Essential Raw Cooling Water System Allowed Completion Time ML16225A6332016-09-0202 September 2016 Browns Ferry Nuclear Plant, Units 1, 2, and 3 - Sequoyah Nuclear Plant, Units 1 and 2; Watts Bar Nuclear Plant, Unit 1 and 2 - Relief Request for Use of Alternate Calibration Block Reflector Requirements 16-PDI-5 (TAC Nos. MF7754-MF7760) ML16123A1312016-05-12012 May 2016 Relief Requests RP-01, RP-02, RP-06, RP-08, and RV-01 Related to the Inservice Testing Program, Fourth 10-Year Interval (CAC Nos. MF7099 and MF7100) ML15329A1862015-12-0404 December 2015 Request for Relief PR-07 for Alternative Inservice Pump Testing at Reference Values ML15320A2182015-11-30030 November 2015 Issuance of Amendments to Revise Technical Specification for Containment Leakage Rate Program 2024-01-29
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May 28, 2021 Mr. James Barstow Vice President, Nuclear Regulatory Affairs and Support Services Tennessee Valley Authority 1101 Market Street, LP 4A-C Chattanooga, TN 37402-2801
SUBJECT:
SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 - PROPOSED ALTERNATIVE TO THE REQUIREMENTS OF THE ASME CODE (EPID L-2021-LLR-0019)
Dear Mr. Barstow:
By letter dated March 26, 2021, the Tennessee Valley Authority submitted a request to the Nuclear Regulatory Commission (NRC) for the use of an alternative to certain American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPV Code),Section XI requirements at Sequoyah Nuclear Plant, Units 1 and 2. Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee requested to use an alternative on the basis that complying with the specified requirement would result in hardship or unusual difficulty.
The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the Tennessee Valley Authority has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC staff authorizes the use of proposed alternative 21-ISI-1 at Sequoyah Nuclear Plant, Units 1 and 2, starting with the Spring 2021 Outage and for the duration of the fourth 10-year inservice inspection interval, currently scheduled to end on April 30, 2025. All other ASME BPV 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.
If you have any questions, please contact the Project Manager, Michael Wentzel, at 301-415-6459 or Michael.Wentzel@nrc.gov.
Sincerely, Digitally signed by David J. David J. Wrona Date: 2021.05.28 Wrona 09:00:30 -04'00' David J. Wrona, Chief Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-327 and 50-328
Enclosure:
Safety Evaluation cc: Listserv
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE REQUEST NO. 21-ISI-1 FOR THE FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328
1.0 INTRODUCTION
By letter dated March 26, 2021, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21085A764), the Tennessee Valley Authority (the licensee) requested relief from the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPV Code) for the Sequoyah Nuclear Plant (Sequoyah), Units 1 and 2.
The licensee proposed to perform an enhanced visual examination as an alternative to the liquid penetrant examination required by the original Construction Code for the final weld. In addition, if a modified seal weld overlay is required due to an identified defect that cannot be removed, a weld buildup will be installed over the subject canopy seal weld without removal of the defect.
Pursuant to Paragraph 50.55a(z)(2) of Title 10 of the Code of Federal Regulations (10 CFR),
the licensee requested to use the proposed alternative on the basis that complying with the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
2.0 REGULATORY EVALUATION
The regulations at 10 CFR 50.55a(g), Preservice and inservice inspection requirements, require, in part, that inservice inspection (ISI) of the ASME Code Class 1, 2, and 3 components be performed in accordance with Section XI of the ASME Code and applicable addenda as a means of detecting anomaly and degradation indications so that structural integrity of these components can be maintained.
The regulations at 10 CFR 50.55a(z), Alternatives to codes and standards requirements, state, in part, that alternatives to the requirements of paragraphs (b) through (h) of 10 CFR 50.55a, or portions thereof may be used, when authorized by the Director, Office of Nuclear Reactor Regulation. A proposed alternative must be submitted and authorized prior to implementation.
The applicant or licensee must demonstrate that: (1) the proposed alternative would provide an acceptable level of quality and safety, or (2) compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Enclosure
3.0 TECHNICAL EVALUATION
3.1 Licensees Alternative Request No. 21-ISI-1 Applicable Inservice Inspection (ISI) Program Interval and Interval End Date Fourth 10-year ISI interval, currently scheduled to end on April 30, 2025.
ISI Requirement ASME BPV Code,Section XI, Article IWA-4000, Repair/Replace Activities.
Applicable Code Edition and Addenda
ASME Code,Section XI, 2007 Edition through 2008 Addenda, and ASME Code Section III, 1971 Edition through Winter 1972 Addenda.
Proposed Alternative Starting with the Spring 2021 refueling outage, the licensee is planning to periodically inspect the control rod drive mechanism (CRDM) latch assemblies and associated driveline components. If a latch assembly needs to be replaced, the mid canopy seal weld for the subject CRDM would need to be cut and rewelded after the CRDM housing is reassembled. Because of a combination of physical limitations, personnel safety, and consideration of high radiation exposure, the licensee has requested the use of contingent alternative 21-ISI-1 for the re-installation of the CRDM mid canopy seal welds at Sequoyah, Units 1 and 2. For additional details on the licensees request, please refer to the document located at the ADAMS Accession No. ML21085A764.
3.2 NRC Staff Evaluation Article IWA 4000 of the ASME Code,Section XI requires that repairs be performed in accordance with the owner's original construction code for the component or system, or later editions and addenda of the Code. The original construction code for 53 of the CRDM housings at Sequoyah, Units 1 and 2, is the ASME Code,Section III, Summer 1968 Edition. However, that edition of the Code does not have specific fabrication or examination requirements applicable to the canopy seal welds. Four CRDM housing assemblies for each of the Sequoyah units were purchased separately and are certified to the ASME Code,Section III, 1971 Edition through Winter 1972 Addenda. The ASME Code,Section III, 1971 Edition through Winter 1972 Addenda has requirements applicable to the CRDM canopy seal welds. The licensee has chosen to apply the requirements of the ASME Code,Section III, 1971 Edition through Winter 1972 Addenda to the re-installation of Sequoyah canopy seal welds. The NRC staff notes that in order to replace or repair a canopy seal weld in accordance with ASME Code,Section III, 1971 Edition through Winter 1972 Addenda, a new or repaired canopy seal weld would require surface examination and removal of indications followed by another surface examination to ensure that rejectable indications have been removed. There are currently no known degraded canopy seal welds at Sequoyah, Units 1 and 2. The licensees current request is intended as a contingency in case a CRDM latch assembly is repaired as a result of the planned internal inspections for the CRDMs at Sequoyah, Units 1 and 2.
The NRC staff reviewed the licensees basis and justification for its contingency alternative repair and subsequent examination method, as stated in proposed alternative 21-ISI-1. The NRC staff finds that the licensees assertion that compliance with the ASME Code requirements for the CRDM mid-canopy seal welds at Sequoyah, Units 1 and 2, would result in hardship or unusual difficulty is acceptable on the basis that the subject components are located such that there is limited space and high radiation levels.
In the event that a CRDM mid canopy seal weld at Sequoyah, Units 1 and 2, would require to be replaced or modified with a seal weld overlay, the licensee has proposed using a remote enhanced visual examination on the completed weld in lieu of the required ASME Code surface examinations. Additionally, as an added contingency in the event that a defect is identified in the seal weld or adjoining base metal that cannot be removed, the licensee has proposed using a modified seal weld overlay, without removal of the defect. The final weld will be examined by the proposed remote enhanced visual means. The licensee will perform a demonstration of the remote visual examination for the Authorized Nuclear Inservice Inspector to qualify the adequacy of the enhanced visual examination.
The NRC staff notes that the structural components associated with the CRDMs are assembled by threaded connections. The CRDM assemblies and their threaded joints provide the primary pressure boundary and structural support for the CRDMs. The canopy seal welds are intended for secondary pressure retention only and do not provide the primary pressure boundary or structural support. The licensee provided a drawing that demonstrates the general configuration of a CRDM with the mid canopy seal weld along with a latch assembly that may need to be replaced (Figure 1 of submittal).
The NRC staff also notes that it approved similar alternatives in 1996 and 2000 for use at Sequoyah, Unit 1, to repair and examine lower canopy seal welds (ADAMS Accession Nos. ML20107L104 and ML003749067).
In summary, the NRC staff reviewed the licensees submittal and finds that compliance with the ASME BPV Code requirements for the re-installation of mid canopy seal welds would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Additionally, the NRC staff finds that proposed alternative 21-ISI-1 will provide reasonable assurance of leak tightness and structural integrity because: 1) the proposed repair follows the welding qualification requirements of the ASME Code,Section XI, 2) the proposed repair will meet the design requirements of ASME Code,Section III, 3) alternate enhanced examination will be qualified by demonstration for the Authorized Nuclear Inservice Inspector, 4) similar alternatives were approved and used previously at Sequoyah, Unit 1, 5) structural integrity of the subject components will not be altered by the alternative, and 6) these components would be subject to the periodic system leakage testing requirements of the ASME BPV Code,Section XI.
4.0 CONCLUSION
The NRC staff has determined that complying with the specified requirements described in the licensees request referenced above would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The proposed alternative provides reasonable assurance of structural integrity and leak tightness of the subject components. Therefore, the NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(2).
The NRC staff authorizes the use of proposed alternative 21-ISI-1 at Sequoyah, Units 1 and 2, starting with the Spring 2021 Outage and for the duration of the fourth 10-year ISI interval, currently scheduled to end on April 30, 2025.
All other ASME BPV Code,Section XI requirements for which an alternative was not specifically requested and authorized remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: R. Kalikian Dated: May 28, 2021
ML21131A163 *by e-mail OFFICE NRR/DORL/LPLII-2/PM NRR/DORL/LPLII-2/LA NRR/DNRL/NPHP/BC NAME MWentzel RButler MMitchell DATE 05/27/2021 05/14/2021 05/11/2021 OFFICE NRR/DORL/LPLII-2/BC NAME DWrona DATE 05/28/2021