08-11-2016 | On June 13, 2016 during evaluation of protection of required equipment from the damaging effects of tornados, was not adequately protected from tornado missiles. This is a legacy design construction issue.
On June 13, 2016 at 1609 central time, Operations declared the affected equipment inoperable, implemented Enforcement Guidance Memorandum (EGM) 15-002, "Enforcement Discretion for Tornado-Generated Missile Protection Noncompliance", along with the required compensatory measures and declared the affected equipment operable but non-conforming thereafter.
The cause of this issue was a lack of clarity and changing requirements during the original licensing of the plant that led to inadequate understanding of the original regulatory guidance.
Corrective actions include implementation of compensatory strategies and extent of condition reviews for the identified conditions. |
---|
|
---|
Category:Letter
MONTHYEARIR 05000368/20253012024-09-0909 September 2024 Notification of NRC Initial Operator Licensing Examination 05000368/2025301 IR 05000313/20240112024-09-0505 September 2024 Comprehensive Engineering Team Inspection Report 05000313/2024011 and 05000368/2024011 IR 05000313/20244042024-08-29029 August 2024 Cybersecurity Inspection Report 05000313/2024404 and 05000368/2024404 ML24239A3972024-08-23023 August 2024 Rssc Wire & Cable LLC Dba Marmon - Part 21 Final Notification - 57243-EN 57243 IR 05000313/20240052024-08-21021 August 2024 Updated Inspection Plan for Arkansas Nuclear One – Units 1 and 2 (Report 05000313/2024005, 05000368/2024005) IR 05000313/20240022024-08-0606 August 2024 Integrated Inspection Report 05000313/2024002 and 05000368/2024002 ML24208A0962024-07-25025 July 2024 57243-EN 57243 - Rssc Wire & Cable LLC, Dba Marmon - Part 21 Notification ML24101A1792024-06-25025 June 2024 Issuance of Amendment No. 333 Revision to Technical Specifications to Adopt TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b ML24143A0632024-05-22022 May 2024 Notification of Inspection (NRC Inspection Report 05000368/2024003) and Request for Information ML24128A2472024-05-0808 May 2024 Project Manager Assignment IR 05000313/20240012024-05-0808 May 2024 Integrated Inspection Report 05000313/2024001 and 05000368/2024001 ML24107A0282024-04-17017 April 2024 Notification of Comprehensive Engineering Team Inspection (05000313/2024011 and 05000368/2024011) and Request for Information ML24086A5412024-04-10010 April 2024 Authorization of Request for Alternative ANO1-ISI-037 Regarding Extension of Reactor Vessel Inservice Inspection Interval IR 05000313/20244022024-04-0808 April 2024 Security Baseline Inspection Report 05000313/2024402 and 05000368/2024402 (Full Report) ML24089A2262024-03-29029 March 2024 Entergy Response to Regulatory Issue Summary 2024-01, Preparation and Scheduling of Operator Licensing Exams ML24075A1712024-03-15015 March 2024 Nuclear Onsite Property Damage Insurance (10 CFR 50.54(w)(3)) ML24074A2892024-03-14014 March 2024 Proof of Financial Protection (10 CFR 140.15) ML24031A6442024-03-14014 March 2024 Issuance of Amendment No. 282 to Modify Technical Specification 3.3.1, Reactor Pressure System (RPS) Instrumentation, Turbine Trip Function on Low Control Oil Pressure ML24102A1342024-03-12012 March 2024 AN1-2024-03 Post Exam Submittal IR 05000313/20230062024-02-28028 February 2024 Annual Assessment Letter for Arkansas Nuclear One- Units 1 and 2 Report 05000313/2023006 and 05000368/2023006 IR 05000313/20243012024-02-27027 February 2024 NRC Initial Operator Licensing Examination Approval 05000313/2024301 IR 05000313/20230042024-02-0808 February 2024 Integrated Inspection Report 05000313/2023004 and 05000368/2023004 and Independent Spent Fuel Storage Installation Inspection Report 07200013/2023002 ML23326A0392024-01-24024 January 2024 Issuance of Amendment No. 281 Revision to Technical Specifications to Adopt TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b ML24017A1582024-01-17017 January 2024 Submittal of Emergency Plan Revision 50 IR 05000313/20234202024-01-10010 January 2024 Security Baseline Inspection Report 05000313/2023420 and 05000368/2023420 IR 05000313/20234022024-01-0202 January 2024 Security Baseline Inspection Report 05000313/2023402 and 05000368/2023402 ML23349A1672023-12-21021 December 2023 Request for Withholding Information from Public Disclosure ML23354A0022023-12-21021 December 2023 Request for Withholding Information from Public Disclosure ML23348A3572023-12-14014 December 2023 Application to Revise Technical Specifications to Use Online Monitoring Methodology Slides and Affidavit for Pre-Submittal Meeting ML23340A1592023-12-13013 December 2023 Entergy Operations, Inc. - Entergy Fleet Project Manager Assignment ML23352A0292023-12-13013 December 2023 Entergy - 2024 Nuclear Energy Liability Evidence of Financial Protection IR 05000313/20234052023-12-12012 December 2023 Security Baseline Inspection Report 05000313/2023405 and 05000368/2023405 ML23341A0832023-12-11011 December 2023 Material Control and Accounting Program Inspection Report 05000313/368/2023404- Cover Letter ML23305A0922023-12-0707 December 2023 Summary of Regulatory Audit Regarding License Amendment Request to Revise Technical Specifications to Adopt TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times RITSTF Initiative 4b ML23333A1362023-11-29029 November 2023 Supplement to Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation ML23275A2072023-11-28028 November 2023 Issuance of Amendment No. 280 Removal of Technical Specification Condition Allowing Two Reactor Coolant Pump Operation IR 05000313/20230032023-11-21021 November 2023 Revised - ANO Revised Integrated Inspection Report 05000313/2023003 and 05000368/2023003 and Independent Spent Fuel Storage Installation Inspection Report 07200013/ 2023001 ML23325A1412023-11-21021 November 2023 Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation ML23313A0962023-11-13013 November 2023 Integrated Inspection Report 05000313/2023003 and 05000368/2023003 and Independent Spent Fuel Storage Installation Inspection Report 07200013/2023001 ML23243B0452023-11-13013 November 2023 Request for Withholding Information from Public Disclosure ML23311A2082023-11-0909 November 2023 Reassignment of U.S. Nuclear Regulatory Commission Branch Chief in the Division of Operating Reactor Licensing for Plant Licensing Branch IV IR 05000313/20230112023-10-10010 October 2023 Commercial Grade Dedication Inspection Report 05000313/2023011 and 05000368/2023011 IR 05000313/20230052023-08-21021 August 2023 Updated Inspection Plan for Arkansas Nuclear One, Units 1 and 2 (Report 05000313/2023005 and 05000368/2023005) - Mid Cycle IR 05000313/20230022023-08-11011 August 2023 Integrated Inspection Report 05000313/2023002 and 05000368/2023002 and Notice of Violation ML23209A6022023-08-0909 August 2023 Regulatory Audit Plan in Support of License Amendment Request to Revise Technical Specifications to Adopt Risk- Informed Completion Times IR 05000416/20230022023-08-0808 August 2023 Integrated Inspection Report 05000416/2023002 and Independent Spent Fuel Storage Installation Inspection Report 07200050/2023001 ML23208A2132023-08-0303 August 2023 Regulatory Audit Summary Concerning Review of License Amendment Request to Remove Technical Specification Condition Allowing Two Reactor Coolant Pump Operation ML23208A2112023-07-27027 July 2023 Entergy Operations Inc., Application to Revise Technical Specifications to Adopt TSTF-205, Revision of Channel Calibration, Channel Functional Test, and Related Definitions ML23188A1732023-07-12012 July 2023 Request for Withholding Information from Public Disclosure ML23142A2022023-06-29029 June 2023 Issuance of Amendment Nos. 279 and 332 Emergency Plan Staffing Requirements 2024-09-09
[Table view] Category:Licensee Event Report (LER)
MONTHYEARML20135G7222020-05-14014 May 2020 Final ASP Analysis - ANO 1 (LER 313-96-005) 05000313/LER-2017-0022017-07-26026 July 2017 High Pressure Injection Pump Inoperable for Greater Than Technical Specification Completion Time, LER 17-002-00 for Arkansas Nuclear One, Unit 1, Regarding High Pressure Injection Pump Inoperable for Greater Than Technical Specification Completion Time 05000368/LER-2017-0022017-06-26026 June 2017 Automatic Start of an Emergency Diesel Generator Due to the Momentary Loss of Offsite Power due to Severe Weather, LER 17-002-00 for Arkansas Nuclear One, Unit 2, Regarding Automatic Start of an Emergency Diesel Generator Due to the Momentary Loss of Offsite Power due to Severe Weather 05000313/LER-2017-0012017-06-26026 June 2017 Automatic Start of an Emergency Diesel Generator Due to the Loss of Offsite Power due to Severe Weather, LER 17-001-00 for Arkansas Nuclear One, Unit 1, Regarding Automatic Start of an Emergency Diesel Generator Due to the Loss of Offsite Power due to Severe Weather 05000313/LER-2016-0032017-06-0909 June 2017 Tornado Missile Vulnerabilities Resulting in Unanalyzed Condition, LER 16-003-01 for Arkansas Nuclear One, Unit 1 Regarding Tornado Missile Vulnerabilities Resulting in Unanalyzed Condition 05000368/LER-2017-0012017-05-30030 May 2017 Inadequate Protection from Tornado Missiles Identified Due to Nonconforming Design Conditions, LER 17-001-00 for Arkansas Nuclear One, Unit 2, Regarding Inadequate Protection from Tornado Missiles Identified Due to Nonconforming Design Conditions 05000313/LER-2016-0042016-11-29029 November 2016 Decay Heat Removal System Socket Weld Leak due to a Vibration-Induced Fatigue Crack, LER 16-004-00 for Arkansas Nuclear One, Unit 1, Regarding Decay Heat Removal System Socket Weld Leak Due to a Vibration-Induced Fatigue Crack 05000368/LER-2016-0012016-11-15015 November 2016 Failure of One Emergency Diesel Generator and Subsequent Required Shutdown of Arkansas Nuclear One, Unit 2, LER 16-001-00 for Arkansas Nuclear One, Unit 2, Regarding Failure of One Emergency Diesel Generator and Subsequent Required Shutdown 05000313/LER-2016-0022016-08-11011 August 2016 Tornado Missile Vulnerability Resulting in Condition Prohibited By Technical Specifications, LER 16-002-00 for Arkansas Nuclear One, Unit 1, Regarding Tornado Missile Vulnerability Resulting in Condition Prohibited By Technical Specifications 05000313/LER-2016-0012016-05-18018 May 2016 Non-Functional External Penetration Flood Seals, LER 16-001-00 for Arkansas Nuclear One, Unit 1, Regarding Non-Functional External Penetration Flood Seals 05000313/LER-2015-0012016-02-12012 February 2016 Manual Reactor Trio Due to Oscillations in the Feedwater System, LER 15-001-00 for Arkansas Nuclear One, Unit 1, Regarding Manual Reactor Trip Due to Oscillations in the Feedwater System 2CAN051405, LER 14-01-00 for Arkansas Nuclear One, Unit 2 Regarding Operation of Switchgear Rooms Ventilation Prohibited by Technical Specifications2014-05-15015 May 2014 LER 14-01-00 for Arkansas Nuclear One, Unit 2 Regarding Operation of Switchgear Rooms Ventilation Prohibited by Technical Specifications 0CAN050202, LER 02-S01-00 for Arkansas Nuclear One Units 1 and 2, Compensatory Measures Were Removed While a Security Perimeter Intrusion Detection Microwave Field Remained Disarmed2002-05-10010 May 2002 LER 02-S01-00 for Arkansas Nuclear One Units 1 and 2, Compensatory Measures Were Removed While a Security Perimeter Intrusion Detection Microwave Field Remained Disarmed 2020-05-14
[Table view] |
A. Background
Enforcement Guidance Memorandum (EGM) 15-002, "Enforcement Discretion for Tornado- Generated Missile Protection Noncompliance," provides guidance to exercise enforcement discretion when an operating power reactor licensee does not comply with a plant's current site-specific licensing basis for tornado-generated missile protection. Specifically, discretion would apply to the applicable technical specification (TS) limiting condition(s) for operation (LCO) which would require a reactor shutdown or mode change; if a licensee could not meet TS LCO required action(s) within the TS completion time.
Interim Staff Guidance DSS
Appendix A to DSS-ISG-2016-01 provides guidance for acceptable initial and comprehensive compensatory measures for licensee use in implementing the enforcement discretion outlined in EGM 15-002. The licensee is expected to document (log) the utilization of EGM 15-002, inform the resident inspector, and enter the issue into the corrective action program. For initial compensatory measures, it is expected that the measures listed are already in place at sites that may be affected by severe weather, such as tornadoes and/or hurricane force winds. The measures provided should be verified as current and readily deployable within a very short timeframe (the shortest timeframe could, in some scenarios, be dictated by a (TS) 3.0.3 completion time of one hour).
B. Plant Status At the time the condition was discovered, ANO-1 was operating in Mode 1 at 100% power.
There were no other structures, systems, or components that were inoperable at the time that contributed to the event.
C. Event Description
ANO conducted walk downs and design verifications as extent of condition activities in response to compromised external flood boundaries which were previously identified at the station. See LER 14-001-00 dated May 5, 2014 (ML14125A483).
In June 2016, as part of the extent of condition actions, a list of potential tornado missile protection vulnerabilities was being created to determine if there were any differences between design documentation and actual plant configuration for areas that could be impacted by tornado missiles. On June 13, 2016, a tornado generated missile vulnerability was identified for Door 77 and some of the Safety Related Systems, Structures or Components (SSCs) in the Unit 1 Upper South Electrical Penetration Room. Specifically, there is a potential deficiency associated with the missile shield wall inside this room. A horizontal tornado generated missile could penetrate the hollow metal door and then penetrate the unqualified concrete masonry unit (CMU) wall before striking safety related cables.
Follow-up field inspection confirmed the block wall to be 12 inches thick with some ungrouted cells and the original design requires 18 inches of grouted block wall for missile barriers therefore the wall was not qualified to withstand all postulated missile strikes. The cabling supplying the following components that could be impacted by a tornado missile:
- Engineered Safeguards Actuation System (ESAS) Analog Channel 3: (Reactor Building (RB) Pressure signal and 'B' Loop RCS Pressure signal).
The RPS initiates a reactor trip, if necessary, to protect core fuel design limits and the RCS pressure boundary during abnormalities while the ESAS initiates necessary safety systems, based on the values of selected unit parameters to protect against violating core design limits and to mitigate accidents. The EFIC system instrumentation is designed to protect against the consequences of a simultaneous blowdown of bother steam generators. One of the signals that the EFIC instrumentation generates is MSLI.
Unit 1 TS 3.3.1 addresses the RPS system required actions and completion times. TS 3.3.5 addresses the actions and completion times associated with ESAS. Unit 1 TS 3.3.11 provides the required actions and completion times for the EFIC system. This includes the MSLI signals.
This condition was entered into the ANO corrective action program. The immediate actions were performed for these components as required by the TSs. The guidance provided in EGM 15-002 was utilized to address the prompt operability and reportability of this condition.
D. Event Causes This is a design legacy issue. The cause of this issue was a lack of clarity and changing requirements during the original licensing of the plant that led to inadequate understanding of the original regulatory guidance.
E. Corrective Actions
The following corrective actions have been completed to address this condition:
ANO directive Enforcement Discretion (COPD-038) was implemented in preparation for use of EGM 15-002. Actions were completed to comply with the requirements of EGM 15-002.
Log entries were made documenting the inoperability and subsequent transition to operable but nonconforming equipment status for the affected SSCs. The initial briefing actions were also completed and logged including NRC resident brief.
- All cells of the CMU missile shield wall located inside Door 77 in Room 144 were grouted.
The following corrective actions are being taken to further address this condition:
Prepare an Engineering Change (EC) to enhance the wall to meet design basis for tornado missile loading. In lieu of preparing this EC, a Risk Base Evaluation may be performed to address this vulnerability.
Implement the EC to enhance the wall to meet design basis tornado missile loadings.
In lieu of installing this EC, submit a Risk Based Evaluation for required regulatory approvals.
F. Safety Consequences:
Unit 1 is required to be protected from tornado generated missiles as applied within the unit's design and licensing basis. The safety-related instrumentation required to mitigate the consequences of a tornado event could have potentially been affected by this condition.
During a postulated design basis tornado, this could have resulted in the loss of one or more of the SSCs listed above under Event Description.
The regulation in 10 CFR 50.36(c)(2) outlines LCOs in the TSs. Certain TSs contain LCO statements that include action statements (required actions and their associated completion time) to provide constraints on the length of time components or systems may remain inoperable or out of service before the plant must be shut down or other compensatory measures must be taken. Such time constraints are based on the safety significance of the component or system being removed from service.
EGM 15-002, in providing the basis for granting the enforcement discretion states that, in general, tornado missile scenarios that may lead to core damage are very low probability events because safety-related SSCs are typically designed to withstand the effects of tornados. For a tornado missile induced scenario to occur, a tornado would have to impact the site and result in the generation of missiles that would contact and fail vulnerable, unprotected safety related equipment and/or unprotected safety related subcomponents in a manner that is not immediately repairable or recoverable. In addition, because plants are designed with redundancy and diversity, the tornado missiles would have to affect multiple trains of safety systems and/or means of achieving safe shutdown.
EMG 15-002 states that the NRC completed a generic risk analysis of potential tornado missile protection non compliances to examine the risk significance of these scenarios. The generic nature of this analysis did not afford the staff the capability to assess plant-specific tornado missile protections which likely exist at many reactors that would result in lower risk determinations, and it did not consider the plant-specific nature of the non-compliances or the redundancies of SSCs. The generic analysis assumed that core damage would occur if a tornado hit a plant located in the most active tornado region in the country and that it caused a tornado-generated missile to fail all emergency core cooling equipment at the plant with no ability to recover.
Further, the study did not account for a number of conservatisms. For example, whereas the study assumed the failure of redundant systems due to tornado generated missiles, actual spatial configurations of redundant systems at a plant could lower the probability of complete system failures as a result of tornado generated missiles. Additionally, some tornado generated missiles may not cause system failures at all or may cause failures that are repairable or recoverable within a reasonable time frame.
In summary, EGM 15-002 stated that the generic bounding risk analysis performed by the NRC concluded that this issue is of low risk significance. Therefore, enforcement discretion until June 10, 2018, will not impose significant additional risk to public health and safety.
This condition had no actual safety consequences impacting plant or public safety since ANO has not experience a tornado missile event.
G. Basis for Reportability:
This event is reported pursuant to the following criteria:
10 CFR 50.73(a)(2)(i)(B): Any operation or condition which was prohibited by the plant's Technical Specifications.
The guidance provided in NUREG 1022 states:
An LER is required if a condition existed for a time longer than permitted by the TS (i.e., greater than the total allowable restoration and shutdown outage time (or completion time in the STS)), even if the condition was not discovered until after the allowable time had elapsed and the condition was rectified immediately upon discovery.
H. Additional Information:
10 CFR 50.73(b)(5) states that this report shall contain reference to "any previous similar events at the same plant that are known to the licensee." NUREG-1022 reporting guidance states that term "previous occurrences" should include previous events or conditions that involved the same underlying concern or reason as this event, such as the same root cause, failure, or sequence of events.
A review of the ANO corrective action program and Licensee Event Reports for the previous three years was performed. No previous similar events were identified.
Energy Industry Identification System (El IS) codes and component codes are identified in the text of this report as [XX].
|
---|
|
|
| | Reporting criterion |
---|
05000368/LER-2016-001 | Failure of One Emergency Diesel Generator and Subsequent Required Shutdown of Arkansas Nuclear One, Unit 2 LER 16-001-00 for Arkansas Nuclear One, Unit 2, Regarding Failure of One Emergency Diesel Generator and Subsequent Required Shutdown | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown | 05000313/LER-2016-001 | Non-Functional External Penetration Flood Seals LER 16-001-00 for Arkansas Nuclear One, Unit 1, Regarding Non-Functional External Penetration Flood Seals | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(ii) | 05000313/LER-2016-002 | Tornado Missile Vulnerability Resulting in Condition Prohibited By Technical Specifications LER 16-002-00 for Arkansas Nuclear One, Unit 1, Regarding Tornado Missile Vulnerability Resulting in Condition Prohibited By Technical Specifications | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | 05000313/LER-2016-003 | Tornado Missile Vulnerabilities Resulting in Unanalyzed Condition LER 16-003-01 for Arkansas Nuclear One, Unit 1 Regarding Tornado Missile Vulnerabilities Resulting in Unanalyzed Condition | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | 05000313/LER-2016-004 | Decay Heat Removal System Socket Weld Leak due to a Vibration-Induced Fatigue Crack LER 16-004-00 for Arkansas Nuclear One, Unit 1, Regarding Decay Heat Removal System Socket Weld Leak Due to a Vibration-Induced Fatigue Crack | 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
|