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Category:Letter
MONTHYEARIR 05000390/20250102024-11-0404 November 2024 Notification of an NRC (FPTI) (NRC Inspection Report 05000390/2025010 0500039/ 2025010) (RFI) CNL-24-074, Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2024-10-23023 October 2024 Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure Revisions IR 05000390/20243012024-10-17017 October 2024 Operator Licensing Examination Approval 05000390/2024301 and 05000391/2024301 ML24282B0412024-10-15015 October 2024 Request for Withholding Information from Public Disclosure for Sequoyah Nuclear Plant, Units 1 and 2 and Watts Bar Nuclear Plant, Units 1 and 2 ML24260A1682024-10-0404 October 2024 Regulatory Audit Summary Related to Request to Add and Revise Notes Related to Technical Specification Table 3.3.2-1, Function 5 ML24261C0062024-10-0404 October 2024 Correction to Amendment No. 134 to Facility Operating License No. NPF-90 and Amendment No. 38 to Facility Operating License No. NPF-96 ML24284A1072024-09-26026 September 2024 Affidavit for Request for Withholding Information from Public Disclosure for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Units 1 and 2 CNL-24-060, Supplement to Request for Approval of the Tennessee Valley Authority Nuclear Quality Assurance Program Description2024-09-24024 September 2024 Supplement to Request for Approval of the Tennessee Valley Authority Nuclear Quality Assurance Program Description CNL-24-047, Decommitment of Flood Mode Mitigation Improvement Systems2024-09-24024 September 2024 Decommitment of Flood Mode Mitigation Improvement Systems ML24262A0602024-09-23023 September 2024 Summary of August 19, 2024, Meeting with Tennessee Valley Authority Regarding a Proposed Supplement to the Tennessee Valley Authority Nuclear Quality Assurance Plan CNL-24-065, Tennessee Valley Authority – Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2024-09-18018 September 2024 Tennessee Valley Authority – Central Emergency Control Center Emergency Plan Implementing Procedure Revisions 05000390/LER-2024-002, Automatic Reactor Trip Due to Main Generator Protection Relay Actuation2024-09-0505 September 2024 Automatic Reactor Trip Due to Main Generator Protection Relay Actuation IR 05000390/20240052024-08-28028 August 2024 Updated Inspection Plan and Assessment Follow-Up Letter for Watts Bar Nuclear Plant, Units 1 and 2 - Report 05000390-2024005 and 05000391-2024005 ML24218A1442024-08-27027 August 2024 Issuance of Amendment Nos. 169 and 75 Regarding Technical Specification Surveillance Requirement 3.9.5.1 to Reduce the Residual Heat Removal Flow Rate IR 05000390/20244022024-08-20020 August 2024 – Security Baseline Inspection Report 05000390-2024402 and 05000391/2024402 - Public CNL-24-061, Supplement to Application to Revise Function 5 of Technical Specification Table 3.3.2-1, ‘Engineered Safety Feature Actuation System Instrumentation,’ for the Sequoyah and Watts Bar (SQN-TS-23-02 and WBN-TS-23-08),2024-08-19019 August 2024 Supplement to Application to Revise Function 5 of Technical Specification Table 3.3.2-1, ‘Engineered Safety Feature Actuation System Instrumentation,’ for the Sequoyah and Watts Bar (SQN-TS-23-02 and WBN-TS-23-08), ML24219A0262024-08-12012 August 2024 Request for Withholding Information from Public Disclosure IR 05000390/20240022024-08-0707 August 2024 Integrated Inspection Report 05000390/2024002 and 05000391/2024002 Rev ML24204A2652024-07-25025 July 2024 Regulatory Audit Summary Related to Request to Revise Technical Specification Surveillance Requirement 3.9.5.1 to Reduce the Residual Heat Removal Flow Rate ML24199A0012024-07-22022 July 2024 Clarification and Correction to Exemption from Requirement of 10 CFR 37.11(c)(2) ML24170A8002024-07-15015 July 2024 Issuance of Amendment Nos. 168 and 74 Regarding Revision to Technical Specification Table 1.1-1 for Required Number of Fully Tensioned Reactor Pressure Vessel Head Closure Bolts ML24172A1342024-07-15015 July 2024 Exemptions from 10 CFR 37.11(C)(2) (EPID L-2023-LLE-0024) - Letter IR 05000390/20244402024-07-12012 July 2024 95001 Supplemental Inspection Supplemental Report 05000390-2024440 and 05000391-2024440 and Follow-Up Assessment Letter 05000391/LER-2024-003, Inoperability of Both Trains of Unit 2 Low Head Safety Injection2024-07-11011 July 2024 Inoperability of Both Trains of Unit 2 Low Head Safety Injection ML24131A0012024-07-0202 July 2024 Issuance of Amendment Nos. 167 and 73 Regarding Adoption of Technical Specification Task Force Traveler TSTF-427-A, Revision 2 CNL-24-052, Response to Request for Additional Information Regarding Application to Modify the Technical Specification Surveillance Requirement 3.9.5.1 (WBN-TS-21-14)2024-06-27027 June 2024 Response to Request for Additional Information Regarding Application to Modify the Technical Specification Surveillance Requirement 3.9.5.1 (WBN-TS-21-14) CNL-24-018, License Amendment Request for Adoption of Technical Specification Task Force Traveler TSTF-276-A, Revision 2, Regarding TS 3.8.1 AC Sources – Operating to Clarify Requirements for Diesel Generator Testing (WBN-TS2024-06-25025 June 2024 License Amendment Request for Adoption of Technical Specification Task Force Traveler TSTF-276-A, Revision 2, Regarding TS 3.8.1 AC Sources – Operating to Clarify Requirements for Diesel Generator Testing (WBN-TS ML24089A1152024-06-21021 June 2024 Transmittal Letter, Environmental Assessments and Findings of No Significant Impact Related to Exemption Requests from 10 CFR 37.11(c)(2) ML24141A0482024-05-17017 May 2024 EN 56958_1 Ametek Solidstate Controls, Inc ML24100A7642024-05-16016 May 2024 Issuance of Amendment No. 166 Regarding Revision to Technical Specification 3.8.2, AC Sources-Shutdown, to Remove Reference to C-S Diesel Generator (CNL-23-062) IR 05000390/20240012024-05-14014 May 2024 Integrated Inspection Report 05000390/2024001 and 05000391/2024001 CNL-24-040, Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2024-05-0808 May 2024 Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure Revisions 05000391/LER-2024-002, Re Automatic Reactor Trip Due to Steam Generator 3 Level LO-LO2024-05-0606 May 2024 Re Automatic Reactor Trip Due to Steam Generator 3 Level LO-LO IR 05000391/20240072024-04-30030 April 2024 Assessment Follow-up Letter for Watts Bar Nuclear Plant, Unit 2 – Report 05000391/2024007 ML24120A1182024-04-29029 April 2024 – Notification of NRC Supplemental Inspection (95001) and Request for Information CNL-24-037, Clinch River, Sequoyah, Units 1 and 2, Watts Bar, Unit 1 and 2, Nuclear Quality Assurance Plan, TVA-NQA-PLN89-A, Revision 422024-04-22022 April 2024 Clinch River, Sequoyah, Units 1 and 2, Watts Bar, Unit 1 and 2, Nuclear Quality Assurance Plan, TVA-NQA-PLN89-A, Revision 42 ML24087A1912024-04-18018 April 2024 Exemption from Select Requirements of 10 CFR Part 73, Security Notifications, Reports, and Recordkeeping and Suspicious Activity Reporting CNL-24-024, Hydrologic Engineering Center River Analysis System Project Milestone Status Update2024-04-17017 April 2024 Hydrologic Engineering Center River Analysis System Project Milestone Status Update CNL-24-010, License Amendment Request to Recapture Low-Power Testing Time (WBN-TS-23-19)2024-04-17017 April 2024 License Amendment Request to Recapture Low-Power Testing Time (WBN-TS-23-19) CNL-24-033, Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2024-04-17017 April 2024 Central Emergency Control Center Emergency Plan Implementing Procedure Revisions ML24072A0052024-04-15015 April 2024 Issuance of Amendment Nos. 165 and 72 Regarding Increase in the Maximum Number of Tritium Producing Burnable Absorber Rods and Supporting Changes, and Revision to the Updated Final Safety Analysis Report CNL-24-004, Application to Modify the Watts Bar Nuclear Plant, Unit 1 and Unit 2 Technical Specifications for Main Control Room Chiller Completion Time Extension (WBN-TS-23-13)2024-04-0404 April 2024 Application to Modify the Watts Bar Nuclear Plant, Unit 1 and Unit 2 Technical Specifications for Main Control Room Chiller Completion Time Extension (WBN-TS-23-13) IR 05000390/20244012024-04-0202 April 2024 – Security Baseline Inspection Report 05000390/2024401 and 05000391/2024401 - (Public) CNL-24-020, Clinch River, Sequoyah, Units 1 and 2, Watts Bar, Units 1 and 2, Request for Approval of Quality Assurance Program Description and Application to Revise the Technical Specifications Associated with QAPD Requirements2024-04-0101 April 2024 Clinch River, Sequoyah, Units 1 and 2, Watts Bar, Units 1 and 2, Request for Approval of Quality Assurance Program Description and Application to Revise the Technical Specifications Associated with QAPD Requirements 05000391/LER-2024-001, Automatic Reactor Trip Due to Main Generator Protection Relay Actuation2024-03-27027 March 2024 Automatic Reactor Trip Due to Main Generator Protection Relay Actuation CNL-24-007, Annual Insurance Status Report2024-03-27027 March 2024 Annual Insurance Status Report CNL-24-008, Guarantee of Payment of Deferred Premiums - 2023 Annual Report2024-03-27027 March 2024 Guarantee of Payment of Deferred Premiums - 2023 Annual Report CNL-24-025, Notice of Intent to Pursue License Renewal for Watts Bar Nuclear Plant, Unit 1 - Submittal Schedule2024-03-25025 March 2024 Notice of Intent to Pursue License Renewal for Watts Bar Nuclear Plant, Unit 1 - Submittal Schedule ML24081A0262024-03-21021 March 2024 Emergency Plan Implementing Procedure Revisions ML24079A0312024-03-19019 March 2024 Wb 2024-301, Corporate Notification Letter (210-day Ltr) 2024-09-05
[Table view] Category:Inspection Report
MONTHYEARIR 05000390/20250102024-11-0404 November 2024 Notification of an NRC (FPTI) (NRC Inspection Report 05000390/2025010 0500039/ 2025010) (RFI) IR 05000390/20243012024-10-17017 October 2024 Operator Licensing Examination Approval 05000390/2024301 and 05000391/2024301 IR 05000390/20240052024-08-28028 August 2024 Updated Inspection Plan and Assessment Follow-Up Letter for Watts Bar Nuclear Plant, Units 1 and 2 - Report 05000390-2024005 and 05000391-2024005 IR 05000390/20244022024-08-20020 August 2024 – Security Baseline Inspection Report 05000390-2024402 and 05000391/2024402 - Public IR 05000390/20240022024-08-0707 August 2024 Integrated Inspection Report 05000390/2024002 and 05000391/2024002 Rev IR 05000390/20244402024-07-12012 July 2024 95001 Supplemental Inspection Supplemental Report 05000390-2024440 and 05000391-2024440 and Follow-Up Assessment Letter IR 05000390/20240012024-05-14014 May 2024 Integrated Inspection Report 05000390/2024001 and 05000391/2024001 IR 05000391/20240072024-04-30030 April 2024 Assessment Follow-up Letter for Watts Bar Nuclear Plant, Unit 2 – Report 05000391/2024007 IR 05000390/20244012024-04-0202 April 2024 – Security Baseline Inspection Report 05000390/2024401 and 05000391/2024401 - (Public) IR 05000390/20240102024-03-0808 March 2024 Age-Related Degradation Inspection Report 05000390/2024010 and 05000391/2024010 IR 05000390/20230062024-02-28028 February 2024 Annual Assessment Letter for Watts Bar Nuclear Plant Units 1 and 2 - Report 05000390/2023006 and 05000391/2023006 IR 05000390/20230042024-02-13013 February 2024 Integrated Inspection Report 05000390/2023004 and 05000391/2023004 and Apparent Violation IR 05000390/20234412023-12-21021 December 2023 Plant–Final Significance Determination for a Security-Related Greater than Green Finding, Nov, and Assessment Follow-up, 05000390-2023441 and 05000391-2023441-Public IR 05000390/20234042023-12-14014 December 2023 – Security Baseline Inspection Report 05000390/2023404 and 05000391/2023404 IR 05000390/20230102023-11-30030 November 2023 RE-Issue Watts Bar Nuclear Plant - Biennial Problem Identification and Resolution Inspection Report 050000390/2023010 and 05000391/2023010 and Apparent Violation IR 05000390/20230032023-11-13013 November 2023 Integrated Inspection Report 05000390/2023003 and 05000391/2023003 and Apparent Violation ML23296A0242023-10-24024 October 2023 Biennial Problem Identification and Resolution Inspection Report and Preliminary Greater than Green Finding and Apparent Violation IR 05000390/20230052023-08-30030 August 2023 Updated Inspection Plan for Watts Bar Nuclear Plant, Units 1 and 2 - Report 05000390/2023005 and 05000391/2023005 IR 05000390/20230022023-08-16016 August 2023 Reissue - Watts Bar Nuclear Plant - Integrated Inspection Report 05000390/2023002 and 05000391/2023002 ML23220A1582023-08-0909 August 2023 Integrated Inspection Report 05000390/2023002 and 05000391/2023002 IR 05000390/20230112023-07-24024 July 2023 Quadrennial Focused Engineering Inspection (FEI) Commercial Grade Dedication Report 05000390 2023011 and 05000391 2023011 IR 05000390/20234032023-05-30030 May 2023 Cyber Security Inspection Report 05000390/2023403 and 05000391/2023403 IR 05000390/20220032023-05-0909 May 2023 Reissue Watts Bar Nuclear Plant - Integrated Inspection Report 05000390/2022003 and 05000391/2022003 IR 05000390/20230012023-05-0404 May 2023 Integrated Inspection Report 05000390/2023001 and 05000391/2023001 IR 05000390/20234012023-03-13013 March 2023 – Security Baseline Inspection Report 05000390 2023401 and 05000391 2023401 IR 05000390/20220062023-03-0101 March 2023 Annual Assessment Letter for Watts Bar Nuclear Plant, Units 1 and 2 - Report 05000390/2022006 and 05000391/2022006 IR 05000390/20220042023-02-10010 February 2023 – Integrated Inspection Report 05000390/2022004 and 05000391/2022004 IR 05000390/20224202022-12-0101 December 2022 Security Baseline Inspection 05000390/2022420 and 05000391/2022420 Cover Letter ML22318A0072022-11-14014 November 2022 Integrated Inspection Report 05000390/2022003 and 05000391/2022003 IR 05000390/20220102022-10-28028 October 2022 Design Basis Assurance Inspection (Teams) Inspection Report 05000390/2022010 and 05000391/2022010 ML22256A2952022-09-14014 September 2022 Operation of an Independent Spent Fuel Storage Installation Report 07201048/2022001 IR 05000390/20220052022-08-31031 August 2022 Updated Inspection Plan for Watts Bar Nuclear Plant, Units 1 and 2 - Report 05000390/2022005 and 05000391/2022005 - Final IR 05000390/20220022022-08-12012 August 2022 Integrated Inspection Report 05000390/2022002 and 05000391/2022002 and Exercise of Enforcement Discretion IR 05000390/20224012022-08-0303 August 2022 Security Baseline Inspection Report 05000390/2022401 and 05000391/2022401 ML22123A2412022-05-11011 May 2022 Review of the Fall 2021 Mid-Cycle Steam Generator Tube Inspection Report IR 05000390/20220012022-05-11011 May 2022 Integrated Inspection Report 05000390/2022001 and 05000391/2022001 IR 05000390/20210062022-03-0202 March 2022 Annual Assessment Letter for Watts Bar Nuclear Plant, Units 1 and 2 (Report No. 05000390/2021006 and 05000391/2021006) IR 05000390/20210042022-02-10010 February 2022 Integrated Inspection Report 05000390/2021004 and 05000391/2021004 IR 05000390/20223012022-01-0707 January 2022 Notification of Licensed Operator Initial Examination 05000390/2022301 and 05000391/2022301 IR 05000390/20210032021-11-10010 November 2021 Integrated Inspection Report 05000390/2021003 and 05000391/2021003 IR 05000390/20214022021-11-0202 November 2021 Security Baseline Inspection Report 05000390/2021402 and 05000391/2021402 IR 05000390/20214032021-10-26026 October 2021 Material Control and Accounting Program Inspection Report 05000390/2021403 and 05000391/2021403 (OUO Removed) ML21263A0042021-09-24024 September 2021 Review of the Fall 2020 Steam Generator Tube Inspection Report IR 05000390/20214012021-08-31031 August 2021 Security Baseline Inspection Report 05000390/2021401 and 05000391/2021401 IR 05000390/20210052021-08-24024 August 2021 Updated Inspection Plan for Watts Bar Nuclear Plant, Units 1 & 2 Report 05000390/2021005 and 05000391/2021005 IR 05000390/20210022021-08-0404 August 2021 Integrated Inspection Report 05000390/2021002 and 05000391/2021002 IR 05000390/20210122021-07-0101 July 2021 Biennial Problem Identification and Resolution Inspection Report 05000390/2021012 and 05000391/2021012 IR 05000390/20210102021-05-0606 May 2021 NRC Inspection Report 05000390/2021010 and 05000391/2021010 IR 05000390/20210012021-05-0505 May 2021 Integrated Inspection Report 05000390/2021001 and 05000391/2021001 IR 05000390/20210112021-04-13013 April 2021 Triennial Fire Protection Inspection Report 05000390/2021011 and 05000391/2021011 2024-08-07
[Table view] |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION uly 25, 2013
SUBJECT:
WATTS BAR NUCLEAR PLANT - COMPONENT DESIGN BASES INSPECTION FOLLOW UP REPORT 05000390/2013010
Dear Mr. Shea:
On July 8, 2013, the U. S. Nuclear Regulatory Commission (NRC) completed an inspection at your Watts Bar Nuclear Plant, Unit 1. The enclosed inspection report documents the inspection results, which were discussed on July 8, 2013, with Mr. Tim Cleary and other members of your staff.
The inspection examined activities conducted under your license as they relate to safety and compliance with the Commissions rules and regulations and with the conditions of your license.
The inspector reviewed selected procedures, evaluations, and records, and interviewed personnel.
One NRC identified finding of very low safety significance (Green) was identified during this inspection. This finding was determined to involve a violation of NRC requirements. The NRC is treating this violation as a non-cited violation (NCV) consistent with Section 2.3.2 of the Enforcement Policy.
If you contest the violation or significance of the NCV, you should provide a response within 30 days of the date of this inspection report, with the basis for your denial, to the Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington DC 20555-0001; with copies to the Regional Administrator Region II; the Director, Office of Enforcement, United States Nuclear Regulatory Commission, Washington, DC 20555-0001; and the NRC Resident Inspector at the Watts Bar Nuclear Plant. In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter, its enclosure, and your response (if any) will be available electronically for public inspection in the NRC Public Document Room or from the Publicly Available Records (PARS) component of NRC's Agencywide Document Access and Management System (ADAMS). ADAMS is accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).
Sincerely, RA Rebecca L. Nease, Chief Engineering Branch 1 Division of Reactor Safety Docket No. 50-390 License No. NPF-90
Enclosure:
Inspection Report 05000390/2013010, w/Attachment: Supplementary Information
REGION II==
Docket No: 050000390 License No: NPF-90 Report No: 05000390/2013010 Licensee: Tennessee Valley Authority (TVA)
Facility: Watts Bar Nuclear Plant, Unit 1 Location: Spring City, TN 37381 Dates: April 3, 2013 - July 8, 2013 Inspector: M. Riley, Reactor Inspector Approved by: Rebecca Nease, Branch Chief Engineering Branch 1 Division of Reactor Safety Enclosure
SUMMARY
IR 05000390/2013-010; 04/03/2013 - 07/08/2013; Watts Bar Nuclear Plant, Unit 1;
Component Design Bases Inspection Follow up.
This inspection was conducted by a Nuclear Regulatory Commission (NRC) inspector from Region II over a three-month period. One Green non-cited violation was identified.
The significance of inspection findings is indicated by their color (i.e., greater than Green, or Green, White, Yellow, Red) and determined using NRC Inspection Manual Chapter 0609, Significance Determination Process, dated June 2, 2011. All violations of NRC requirements are dispositioned in accordance with the NRCs Enforcement Policy dated January 28, 2013. The NRC's program for overseeing the safe operation of commercial nuclear power reactors is described in NUREG-1649, Reactor Oversight Process, Revision 4, dated December 2006.
A. NRC identified and Self-Revealing Findings
Cornerstone: Mitigating Systems
Green: The NRC identified a non-cited violation of 10 CFR Part 50, Appendix B,
Criterion XVI, Corrective Action, for the licensees failure to implement corrective actions to identify and evaluate the effects of electrical system harmonics on safety-related undervoltage relays. This was a performance deficiency. The licensee entered this issue into their corrective action program as Problem Evaluation Reports 515413 and 703444. The licensee also established a preventative maintenance program to monitor motors powered from the 6.9 kilovolt shutdown boards for harmonic distortion until further monitoring and evaluation of harmonic distortion on the 6.9 kilovolt shutdown board degraded voltage relays can be completed.
The performance deficiency was more than minor because it affected the design control attribute of the Mitigating Systems cornerstone and adversely impacted the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences.
Specifically, at the time of identification, there was reasonable doubt as to whether the degraded voltage scheme would perform as required by the Watts Bar 1 Technical Specifications during design basis conditions. The inspector determined the finding to be of very low safety significance (Green) because the finding was a deficiency affecting the design or qualification of a mitigating structure, system, or component, and the structure, system, or component maintained its operability and functionality. Because the opportunity to identify the impact of harmonics on degraded voltage relay performance occurred in 1993, the inspector determined that no cross-cutting aspect was applicable because the finding was not indicative of current licensee performance. (Section 1R21.1)
Licensee Identified Violations
No findings were identified.
REPORT DETAILS
REACTOR SAFETY
Cornerstones: Initiating Events, Mitigating Systems, Barrier Integrity
1R21 Component Design Bases Inspection
Main article: IP 71111.21
.1 (Closed) URI 05000390/2012008-04, Effect of System Harmonics on Degraded
Voltage Relay Function.(ML12165A186)
a. Inspection Scope
During the 2012 Component Design Bases Inspection, an unresolved item was identified related to the effect of electrical system harmonics on safety-related under voltage relays. In 1993, the licensee identified that harmonic distortions adversely affected the 6.9 kilovolt (kV) bus overvoltage relays by causing them to alarm unnecessarily. However, the licensee did not identify (or otherwise evaluate) the effect that harmonics could have on the ability of degraded voltage relays of similar design to perform their safety function as required by limiting condition for operation 3.3.5 of the plants technical specifications (TS). The inspector was concerned that harmonics on the 6.9kV system could cause the degraded voltage relays to fail to perform as required by TS.
This item was unresolved pending further inspection to determine if the licensees performance constituted a violation of NRC regulatory requirements.
The inspector determined that additional consultation with the Office of Nuclear Reactor Regulation (NRR) was warranted before reaching a final disposition of the unresolved item.
The inspector conducted an in-office review of the licensees maintenance and testing procedures to verify that the licensee had established compensatory measures to monitor for harmonic distortion. The inspector conducted a conference call on June 13, 2013, with the licensee to get their answers to questions that arose during the inspection. The inspector also verified that the licensee established long-term corrective action measures to identify and evaluate the effects of harmonics on the degraded voltage relays.
b. Findings
Introduction:
The NRC identified a Green non-cited violation (NCV) of 10 CFR Part 50, Appendix B, Criterion XVI, Corrective Action, for the licensees failure to implement corrective actions to identify and evaluate the effects of electrical system harmonics on safety-related undervoltage relays. This was a performance deficiency.
Description:
The Watts Bar 1 degraded voltage protection scheme features three Asea Brown Boveri (ABB) Type 27N relays for each 6.9kV Class 1E shutdown board, arranged in a two out of three tripping scheme. The vendor manual for this relay stated that,
- (1) the relay employs a peak voltage detector, and (2)harmonic distortion on the AC waveform can have a noticeable effect on the relay operating point and the measuring instruments used to calibrate the relay.
In 1993, the licensee experienced spurious actuations of the ABB type 59H overvoltage relays, and entered the condition in the corrective action program as Problem Evaluation Report (PER) 930397. These overvoltage relays are similar in design to the ABB type 27N degraded voltage relays (DVRs). The licensee performed troubleshooting tests and found that high levels of 6.9kV system harmonics accompanied the spurious actuations. The transient harmonics documented in Problem Evaluation Report (PER) 930397 were attributed to events that included the trip of the nearby Sequoyah generating station and breaker operations at the Watts Bar station. The Causal Factor section of PER 930397 stated that the relays sometimes trip on harmonic distortion although the root mean square voltages are at acceptable levels. The licensee implemented corrective actions to address this condition by replacing the type 59H overvoltage relays with a model equipped with harmonic filters.
The inspector noted that the Extent of Condition section of PER 930397 did not identify or address whether the DVRs could also be affected by the same harmonics implicated in the maloperation of the overvoltage relays. The reset function of the existing DVRs is identical to the tripping function of the ABB type 59H overvoltage relays that actuated due to transient harmonics in 1993. The DVRs design features an instantaneous reset characteristic that could allow reset of the DVR in less than two cycles in the presence of harmonics, and thereby delay the protective function beyond the 10 seconds stipulated in TS limiting condition for operation 3.3.5. The NRC issued Task Interface Agreement (TIA) 2012-14, Assessment of Watts Bar Nuclear Plant, Unit1, Evaluations that Address the Effect of AC Waveform Harmonic Distortion on DVR Function and the Applicability of 10 CFR 50, Appendix B Requirements, (ADAMS Accession No. ML13092A322) which concluded that harmonic distortion on Class 1E electrical distribution buses could result in the premature reset of the DVRs during a degraded voltage event. The TIA further concluded that reset of the DVRs (and associated timers) during the onset of such an event would: (1)prevent the relays from actuating within the time required by TS,
- (2) represent a condition adverse to the quality of relay operation, and
- (3) be subject to treatment in accordance with the requirements of 10 CFR Part 50, Appendix B, Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants.
The inspector found that the licensee missed three opportunities to identify and evaluate the potential adverse effects of harmonics on the DVRs:
- (1) the vendor manual alerted the user to the effect of harmonics on relay accuracy;
- (2) the licensee experienced adverse effects in 1993, on similar relays due to system harmonics during pre-operational testing; and
- (3) NRC Information Notice 95-05 alerted the industry regarding adverse effects of harmonics on relay accuracy.
The licensee entered this issue into their corrective action program as PERs 515413 and 703444, and performed an immediate operability determination on the DVRs. The licensee also established a preventative maintenance program to monitor motors powered from the 6.9kV shutdown boards for harmonic distortion until further monitoring and evaluation of harmonic distortion on the 6.9kV shutdown board DVRs can be completed.
Analysis:
The licensees failure to implement corrective actions to identify and evaluate the effects of electrical system harmonics on safety-related under voltage relays was a performance deficiency. The performance deficiency was more than minor because it affected the design control attribute of the Mitigating Systems cornerstone and adversely impacted the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, at the time of identification, there was reasonable doubt as to whether the degraded voltage scheme would perform as required by TS during design basis conditions. The inspector used Inspection Manual Chapter 0609, Att. 4, Initial Characterization of Findings, issued 6/19/12, for Mitigating Systems, and Inspection Manual Chapter 0609, App. A, The Significance Determination Process (SDP) for Findings at Power, issued 6/19/12, and determined the finding to be of very low safety significance (Green) because the finding was a deficiency affecting the design or qualification of a mitigating structure, system, or component, and the structure, system, or component maintained its operability and functionality.
Because the opportunity to identify the impact of harmonics on DVR performance occurred in 1993, the inspector determined that no cross-cutting aspect was applicable because the finding was not indicative of current licensee performance.
Enforcement:
Appendix B of 10 CFR Part 50, Criterion XVI, Corrective Action, requires, in part, that measures be established to assure that conditions adverse to quality, such as failures, malfunctions, deficiencies, deviations, defective material and equipment, and non-conformances are promptly identified and corrected. Contrary to the above, since 1993 (when transient harmonics were observed to have an adverse effect on overvoltage relays), the licensee failed to implement corrective action program measures to identify and evaluate the adverse effects of electrical system harmonics on safety-related DVR function.
Transient harmonics could cause the DVRs to spuriously reset during an actual degraded voltage event and delay the protective function beyond the time (10 seconds) stipulated in TS. The licensee established a preventative maintenance program to monitor motors powered from the 6.9kV shutdown boards for harmonic distortion until further monitoring and evaluation of harmonic distortion on the 6.9kV shutdown board DVRs can be completed. This violation is being treated as an NCV, consistent with Section 2.3.2 of the Enforcement Policy. The violation was entered into the licensees corrective action program as PERs 515413 and 703444. (NCV 05000390/2013010-01, Failure to Implement Corrective Actions to Identify and Evaluate Effects of Harmonics on Degraded Voltage Relay Function)
OTHER ACTIVITIES
4OA6 Meetings, Including Exit
On July 8, 2013, the inspector presented the inspection results to Mr. Tim Cleary, Site Vice President, and other members of the licensees staff. The inspector verified that no proprietary information was retained by the inspector or documented in this report.
SUPPLEMENTARY INFORMATION
KEY POINTS OF CONTACT
Licensee personnel
- D. Guinn, Site Licensing Manager
- T. Morgan, Site Licensing
- R. Stroud, Site Licensing
NRC personnel
- R. Monk, Senior Resident Inspector, Watts Bar Unit 1 Resident Office
- K. Miller, Resident Inspector, Watts Bar Unit 1 Resident Office
- S. Shaeffer, Chief, Project Branch 6, Division of Reactor Projects, Region II
- R. Mathew, Acting Branch Chief, Office of Nuclear Reactor Regulation, Division of
Engineering
ITEMS OPENED, CLOSED, DISCUSSED, AND UPDATED
Opened and Closed
05000390/2013010-01 NCV Failure to Implement Corrective Actions to
Identify and Evaluate Effects of Harmonics
on Degraded Voltage Relay Function
(Section 1R21.1)
Closed
05000390/2012008-04 URI Effect of System Harmonics on Degraded
Voltage Relay Function (Section 1R21.1)
LIST OF DOCUMENTS REVIEWED