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Additional NRC Oversight at Arkansas Nuclear One, Units 1 and 2


On September 18 through October 6, 2017, the Nuclear Regulatory Commission (NRC) performed a supplemental inspection using Inspection Procedure 95001, "Supplemental Inspection Response to Action Matrix Column 2 Inputs." Because significant weaknesses were identified during this inspection, the White finding will remain open and continue to receive consideration as an Action Matrix input until the NRC verifies that all inspection objectives have been met. The NRC reviewed the root and contributing causes that your staff identified for the White finding and concluded that a significant weakness existed because the evaluation was not of sufficient depth to ensure that the significant performance issues were fully understood as described in Objective 1 of Inspection Procedure 95001. The NRC also determined that the extent of cause evaluation did not consider whether a lack of technical detail and vendor information existed for procedures and work orders for components without sight glasses. Therefore, the NRC concluded that inspection Objective 2, which requires proper identification of the extent of condition and extent of cause, was not met. The NRC concluded that your staff implemented appropriate corrective actions to address the root and contributing causes that were identified. However, additional corrective actions may need to be developed once the cause evaluation, the extent of condition review, and the extent of cause review are completed.

On March 23, 2017, the NRC completed the 2016 annual assessment meeting, and discussed the results of the Confirmatory Action Letter follow up inspections completed to date. During the meeting Entergy presented the status of ANO's recovery. A copy of the NRC's presentation and Entergy's presentation is available electronically. Additionally, the NRC responded to Entergy's acknowledgement of the White finding associated with the failure to ensure adequate lubrication to an emergency diesel generator bearing on Unit 2. The NRC's review determined that your letter was responsive to the information requested.

The NRC has published a Confirmatory Action Letter follow-up planning document. This document contains inspection planning considerations for reviewing Entergy's progress in improving the safety performance at Arkansas Nuclear One. The NRC will perform inspections approximately quarterly to evaluate the status of performance improvement and to independently review the effectiveness of Entergy's actions. The expected completion dates listed in the attachment reflect the planned action completion, but do not include any planned effectiveness reviews. The NRC has identified some specific CRP actions that will require a suitable period of time to elapse following completion of the associated improvement action for the NRC to be able to adequately assess whether sustained improvement is evident. These actions are identified as "sustained improvement items" in the attachment. The NRC will use the results of these inspections will provide information for future performance assessments of ANO Units 1 and 2, and will serve as the basis for the NRC to determine when ANO should transition out of Column 4 of the Agency Action Matrix, in accordance with NRC Inspection Manual Chapter 0305, "Operating Reactor Assessment Program."

The NRC issued the supplemental Inspection Procedure 95003 report on June 9, 2016.  The NRC determined that ANO is being operated safely and that Entergy understands the depth and breadth of performance concerns associated with ANO's performance decline.  The NRC concluded that effective implementation and continued enhanced oversight by Entergy leadership, should lead to substantial and sustained performance improvement.  ANO's planned corrective actions to address the significant safety performance deficiencies are contained in the Comprehensive Recovery Plan.  Specific actions needed to resolve the problems identified and improve safety performance are listed in the Confirmatory Action Letter.  The NRC plans to conduct follow-up inspections approximately quarterly to review progress toward completing the committed actions.

The NRC will be conducting the following supplemental Inspection Procedures (IP):

  • IP 95003, "Supplemental Inspection for Repetitive Degraded Cornerstones, Multiple Degraded Cornerstones, Multiple Yellow Inputs or One Red Input," as a result of Arkansas Nuclear One being moved to the Multiple/Repetitive Degraded Cornerstone (Column 4) of the NRC Action Matrix
  • IP 95002, "Supplemental Inspection for One Degraded Cornerstone or Any Three White Inputs in a Strategic Performance Area," on each unit for each of the Yellow findings (Yellow finding on each unit affecting the Initiating Events Cornerstone as a result of the Heavy Component Drop and a Yellow finding on each unit affecting the Mitigating Systems Cornerstone as a result of the Degraded Flood Protection Features) and
  • IP 95001, "Supplemental Inspection for One or Two White Inputs in a Strategic Performance Area," based on the performance indicator data for unplanned scrams for Unit 2 transitioning to White for the second and third quarters of 2014.

These supplemental inspections will be performed onsite from January 25, 2016, through February 5, 2016, and February 22 through 26, 2016 by a team of 28 inspectors from all four Regional offices, the Office of Nuclear Reactor Regulation, and the Office of Nuclear Regulatory Research. A public exit meeting is scheduled for April 6, 2016. The time and location are still to be determined.  In addition, this public exit meeting will also discuss the NRC's annual assessment for Arkansas Nuclear One for 2015.

As a result of the continuous performance assessment of Arkansas Nuclear One (ANO) Unit 1 and Unit 2, the U.S. Nuclear Regulatory Commission (NRC) modified its regulatory oversight of ANO, effective October 1, 2014. This was done to address several issues of substantial safety significance that were identified as a result of the events surrounding the industrial accident that occurred at the plant on March 31, 2013, which resulted in one fatality and eight injured personnel.

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The Heavy Component Drop Event

On March 31, 2013, during a Unit 1 outage, the licensee was lifting the Unit 1 main generator stator out of the turbine building when an inadequately designed temporary lifting rig failed, causing the 525 ton stator to fall approximately 30 feet into the train bay. The train bay is shared between Unit 1 and Unit 2. The impact caused substantial damage to the Unit 1 side of the turbine building and power distribution systems, and parts of the lift rig impacted the Unit 2 side of the turbine building.

Unit 1 Impacts

At the time of the event, Unit 1 was shut down in a refueling outage with the reactor vessel head off and fuel in the vessel. The accident was caused by a temporary lift rig that collapsed resulting in dropping the stator on the turbine deck. Dropping this heavy component caused the deck to partially collapse and damage non-vital electrical buses supplying offsite power to Unit 1. Damage to the electrical buses resulted in a loss of offsite power (LOOP) to Unit 1 for six days. While power was available from emergency diesel generators to power both trains of safety-related equipment in Unit 1, cable damage prevented the use of the alternate AC (AAC) (i.e., station blackout) diesel generator electrical cables from being able to supply power to either Unit 1 or Unit 2 switchgear. This resulted in a loss of power to all non-safety loads in Unit 1, complicating the event response.

Unit 2 Impacts

Unit 2 was operating at 100 percent power with no major evolutions in progress at the time of the event. When the temporary lift rig collapsed and the heavy component impacted, the vibration caused reactor coolant pump B to trip, which caused an automatic reactor shutdown. Water from a fire main that was ruptured in the turbine building flowed to several areas of the plant, causing additional damage. Offsite power to Unit 2 from startup transformer 3 was lost after water caused an electrical fault inside the Unit 2 non-safety switchgear in the turbine building, causing a loss of power to the remaining reactor coolant pumps, a running charging pump, and a loss of power to Train B safety-related equipment. Emergency diesel generator 2 automatically started and powered the Train B equipment, while Train A and non-safety equipment were automatically powered from another transformer. While most of the water from the ruptured fire main either went outside or into the turbine buildings, some of this water leaked past degraded floor plug seals and entered the Unit 1 auxiliary building. The water level on the lowest level of the auxiliary building was only 1 - 2 inches, but this was enough to allow water to leak past a floor drain valve that was partially open and enter one of the watertight safety-related pump rooms.

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Yellow Finding Associated with the Heavy Component Drop

The temporary lifting rig collapsed because there were incorrect assumptions and errors in the design such that it could not safety complete the intended lift. A test to verify the capability of the lift rig was not performed due to further errors in communication and decision making. These failures were the result of inadequate oversight of the primary contractor and a subcontractor hired to perform the operation.

As a result, there was a complete loss of offsite power to Unit 1 for six days, and Unit 2 partially lost offsite power. This increased risk to the plant because alternate means of providing electrical power to key safety-related systems was not available using installed plant equipment in the event the diesels failed. The NRC determined that this constituted a violation of substantial safety significance (Yellow).

Yellow Finding for Degraded Flood Protection Features

Following the flooding that occurred during the heavy component drop event, the licensee conducted a comprehensive inspection and identified over 100 deficient flood protection features, including unsealed electrical cable conduits, and degraded hatches and floor plug seals in the auxiliary and emergency diesel fuel storage buildings. NRC inspections subsequently identified additional problems, necessitating further reviews. Both Unit 1 and Unit 2 Safety Analysis Reports (SARs) require that the auxiliary building and safety-related pumps rooms be watertight.

The NRC concluded that the licensee had failed to design, construct, and maintain the flood protection features in both units in accordance with the approved design requirements. The finding included multiple violation examples and was determined to have substantial safety significance (Yellow). The primary contributor to the safety significance was the potential safety impact of the theoretical maximum rainfall event, which could lead to core damage due to equipment damaged from the degraded flood protection features.

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Why is ANO in Column 4 of the Reactor Oversight Process Action Matrix?

The Reactor Oversight Process includes continuous and periodic assessments to be performed to assess licensee safety performance. A variety of inputs are used in these assessments, including inspections findings and NRC Performance Indicators, which are objective measurements of plant performance. When findings and performance indicators include results with elevated safety significance, the assessment process would cause a graduated increase in regulatory oversight based on the number and significance of the issues.

ANO was placed in Column 4, Multiple/Repetitive Degraded Cornerstone, because of two findings of substantial safety significance (Yellow findings), one in the Initiating Events cornerstone, and one in the Mitigating Systems cornerstone. These findings met the criteria to be placed into Column 4 oversight, because the pattern of performance indicated that two cornerstones of safety are degraded.

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What Effect Does Placement in Column 4 Have on ANO?

The Operating Reactor Assessment Program, described in Inspection Manual Chapter (IMC) 0305, provides a graduated regulatory response for different levels of safety performance. This includes the Action Matrix, which describes the regulatory actions for each level. Because the Action Matrix is a table with different columns to distinguish the different levels of performance, it is common to refer to performance as being in a column.

The Action Matrix directs that the NRC conduct a large supplemental inspection (roughly 3,000 inspection hours using about 25 inspectors). The licensee must develop a performance improvement plan with NRC oversight. The NRC will issue a Confirmatory Action Letter to identify the actions from the performance improvement plan that will receive follow-up inspections over the next 2 years to verify that the actions were completed and achieved the appropriate results. When all of the Confirmatory Action Letter items are closed, the Confirmatory Action Letter will be closed, and the plant will be returned to Column 1. Historically, this process has taken plants at least two years.

Entergy officials met with the NRC's five-member Commission on May 21, 2015, to discuss the reasons for ANO's declining performance and to describe actions they plan to address the decline. The NRC will hold a public meeting in Russellville, AR on September 17, 2015, where officials from Entergy Operations, Inc. will discuss preparations for the comprehensive inspection to be conducted next year. Other public meetings will be used to allow public involvement.

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NRC Documents Issued Regarding Increased Oversight at ANO

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The following table lists the publicly available documents that the NRC has issued in connection with the additional oversight of ANO:

Date Title/Description
June 7, 2013 NRC Augmented Inspection Team Report
March 24, 2014 NRC Augmented Inspection Team Follow-up Report
April 10, 2014 NRC Augmented Inspection Team Follow-up Report Errata
May 9, 2014 Regulatory Conference Summary – Findings Associated with the Heavy Component Drop Event
June 23, 2014 Final Significance Letter – Findings Associated with the Heavy Component Drop Event
July 3, 2014 Regulatory Conference Summary Supplement – Findings Associated with the Heavy Component Drop Event
September 9, 2014 NRC Inspection Report – Findings Associated with Degraded Flood Protection Features
November 25, 2014 Regulatory Conference Summary – Findings Associated with Degraded Flood Protection Features
January 22, 2015 Final Significance Letter– Findings Associated with Degraded Flood Protection Features
January 23, 2015 NRC Press Release
March 4, 2015 End-Of-Cycle Assessment Letter
March 6, 2015 NRC Press Release
May 13, 2015 NRC Inspection Report – Severity Level IV for White Performance Indicator for Unplanned Scrams
May 21, 2015 Public Meeting Summary – Annual Assessment Meeting
June 29, 2015 NRC Problem Identification and Resolution Inspection Report
August 20, 2015 NRC Press Release
September 1, 2015 Mid-Cycle Assessment Letter
September 24, 2015 Public Meeting Summary – NRC Oversight Activities and ANO Recovery Actions
January 19, 2016 NRC's Response to Notification of Readiness for Supplemental Inspection Procedure 95003
March 16, 2016 Public Meeting with Entergy Operations, Inc.
April 18, 2016 Summary of Meeting to Discuss Supplemental Inspection Results and Annual Assessment Meeting With Entergy Operations Inc. Regarding 2015 Performance of Arkansas Nuclear One
June 9, 2016 Arkansas Nuclear One – NRC Supplemental Inspection Report 05000313/2016007 and 05000368/2016007
June 17, 2016 Confirmatory Action Letter – Arkansas Nuclear One, Units 1 And 2
August 9, 2016 Inspection Planning Considerations for Reviewing Items Associated with the Confirmatory Action Letter for Arkansas Nuclear One, Units 1 and 2
November 9, 2016 Arkansas Nuclear One – NRC Problem Identification and Resolution Inspection and Confirmatory Action Letter (EA-16-124) Follow-Up Inspection Report 05000313/2016010 and 05000368/2016010
January 19, 2017 Arkansas Nuclear One – NRC Inspection Report 05000368/2016011 and Preliminary White Finding
February 24, 2017 Request to Modify a Prior Confirmatory Action Letter Commitment Arkansas Nuclear One – Units 1 and 2 Docket Nos. 50-313 and 50-368 License Nos. DPR-51 and NPF-6
February 27, 2017 Arkansas Nuclear One, Unit 2 – Final Significance Determination of a White Finding and Notice of Violation, NRC Inspection Report 05000368/2017014
February 28, 2017 Arkansas Nuclear One – NRC Component Design Bases Inspection and Confirmatory Action Letter Follow-Up Inspection Report 05000313/2016008 and 05000368/2016008
March 1, 2017 Annual Assessment Letter for Arkansas Nuclear One, Units 1 and 2 (Report 05000313/2016006 and 05000368/2016006)
March 8, 2017 NRC To Hold Public Meeting on Arkansas Nuclear One
March 29, 2017 Revision to Confirmatory Action Letter for Arkansas Nuclear One, Units 1 and 2
April 3, 2017 Arkansas Nuclear One, Unit 2 – Response to notice of violation (NRC Inspection Report 05000368/2017014)
April 4, 2017 Summary of Annual Assessment Meeting with Entergy Operations Inc. Regarding 2016 Performance of Arkansas Nuclear One and Confirmatory Action Letter Follow-up Inspection Results
April 27, 2017 NRC Confirmatory Action Letter (EA-16-124) Follow-Up Inspection Report 05000313/2017010 AND 05000368/2017010
June 14, 2017 NRC Confirmatory Action Letter (EA-16-124) Follow-Up Inspection Report 05000313/2017011 AND 05000368/2017011
October 6, 2017 Arkansas Nuclear One – NRC Confirmatory Action Letter (Ea-16-124) Follow-Up Inspection Report 05000313/2017012 and 05000368/2017012
November 7, 2017 Arkansas Nuclear One – NRC Supplemental Inspection Report 05000368/2017016
January 24, 2018 Arkansas Nuclear One – NRC Confirmatory Action Letter (EA-16-124) Follow-Up Inspection Report 05000313/2017013 and 05000368/2017013

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Page Last Reviewed/Updated Friday, January 26, 2018