|Report date||Site||Event description|
|05000313/LER-2017-002||13 November 2017||Arkansas Nuclear One – Unit 1|
On May 27, 2017, an attempt to start the red train High Pressure Injection (HPI) pump (BJ) in accordance with normal operating procedures was initiated. Control Room operators received an annunciator, HPI PUMP TRIP, and observed no indication of the pump starting.
During investigative walk downs with the relay department, personnel discovered the HPI breaker was not fully racked up (trip pedal still in a tripped (down) condition and roller not free to roll). Operations personnel performed manual breaker operations to rack the 4160 V breaker (EB) further in the up direction. The pump was successfully started and declared operable.
The condition was the result of an inadequate risk evaluation.
The associated Operations Directive has been revised to require Operations management approval when waiving start-checks of vital 4160 VAC components following racking up of the respective breaker. The revision is expected to ensure appropriate personnel are involved when determining the risk associated with not testing components for functionality/operability following racking up evolutions of an associated breaker.
|05000313/LER-2017-001||26 June 2017||Arkansas Nuclear|
Arkansas Nuclear One – Unit 1
On April 26, 2017, Arkansas Nuclear One, Unit 1 (ANO-1), was operating normally at 100% rated thermal power.
The 500kV transmission line to the substation at Pleasant Hill, Arkansas was out of service for planned maintenance.
The area around the plant was experiencing severe weather from thunderstorms and tornado warnings had been issued from the National Weather Service for the four county area.
At approximately 1002 CST switchyard breakers for 500kV lines opened on fault current. High winds had damaged the transmission towers approximately 16 miles away from ANO and caused phase to ground faults. This resulted in a loss of all offsite power lines to the 500kV bus. The autotransformer also locked out as designed when the 500kV transmission lines faulted.
The Reactor Operator initiated a manual reactor trip about 8 seconds after the 500kV lines tripped and prior to the reactor protection system initiating an automatic trip. During this time both emergency diesel generators (EDGs) (EK) started as expected. EDG #2 re-energized one Engineered Safeguards bus. EDG #1 ran unloaded until shutdown.
The plant was stabilized in Mode 3 with Emergency Feedwater (EFW) pumps supplying the steam generators, maintaining the water level at the natural circulation setpoint.
|05000368/LER-2017-002||26 June 2017||Arkansas Nuclear One – Unit 2|
On April 26, 2017, ANO-2 was in day 28 of a refueling outage with the core completely off loaded to the spent fuel pool (SFP). Power to ANO-2 plant equipment was supplied from Start Up Transformer 2 (SU2) while SU3 was out of service for planned maintenance. 500kV and 161kV offsite power lines were in service. The area around the plant was experiencing severe weather from thunderstorms and tornado warnings had been issued from the National Weather Service for the four county area. Switchyard work was ceased.
At approximately 1002 CST switchyard breakers for 500kV lines opened on fault current. High winds had damaged the transmission towers approximately 16 miles away from ANO and caused phase to ground faults. This resulted in a loss of all offsite power lines to the 500 kV bus. The autotransformer also locked out, as designed, when the 500 kV transmission lines faulted.
When the 500kV bus tripped, the 4.16kV bus that feeds a vital 480 volt bus was subjected to a voltage transient; subsequently; the #1 emergency diesel generator (EDG) auto started. The EDG output breaker never closed due to the fact that voltage was restored to normal almost immediately. This EDG was secured due to running unloaded.
Both SFP cooling pumps were out of service after the transient. A SFP cooling pump was restarted at 1020 CST.
The temperature of the SFP did not change during this event.
|05000368/LER-2017-001||30 May 2017||Arkansas Nuclear One – Unit 2|
On April 6, 2017, as part of the closure of an Arkansas Nuclear One, Units 1 and 2 (ANO-1 & 2) Tornado Protection Study, a nonconforming condition in the plant design for a conduit that contains safety related cables for the ANO-2 #1 Emergency Diesel Generator (EDG) meter and relay cabinets, was identified. The conduit did not meet current design basis for protection against a potential tornado missile impact. This vulnerability is similar to those previously reported in LERs associated with ANO-1.
On April 6, 2017, Operations declared the #1 EDG inoperable, implemented Enforcement Guidance Memorandum (EGM) 15-002, “Enforcement Discretion for Tornado-Generated Missile Protection Noncompliance,” along with necessary compensatory measures, and subsequently declared the affected equipment operable but non- conforming. Interim corrections include implementation of compensatory strategies. Plant modifications and license basis changes are being evaluated to resolve outstanding issues.
The cause of this issue was unclear and changing regulatory requirements during original plant licensing that led to an inadequate understanding of the regulatory guidance with respect to tornado missile protection design requirements.
|05000313/LER-2016-004||29 November 2016||Arkansas Nuclear|
On September 29, 2016, at Arkansas Nuclear One, Unit 1 (ANO-1), during refueling outage 1R26 with both trains of Decay Heat Removal (DHR) in service, a 0.125 gpm leak was identified in the DHR system at a one-inch drain line.
This leak was on a section of cross-connect piping shared by both trains of the DHR system. The consequence of the leak was that both trains of the DHR system were declared inoperable.
The leakage was due to a fatigue crack caused by vibration of the drain line due to a pipe support that was not designed for system vibration.
Other systems and components in ANO-1 and ANO, Unit 2 (ANO-2) exposed to elevated system vibration were evaluated with respect to this condition. As a result of this evaluation, socket welds on other drains and vents in the ANO-1 DHR system were cut out and replaced, and pipe supports were modified where needed to withstand system vibration.
|05000368/LER-2016-001||15 November 2016||Arkansas Nuclear||On September 28, 2016, Arkansas Nuclear One, Unit 2, initiated a plant shutdown due to the inability to restore one of the Emergency Diesel Generators (EDGs) to an operable status prior to exceeding the Limited Condition Operation action time. It was determined the EDG was inoperable due to the lack of sufficient lubrication in the inboard generator bearing leading to bearing failure. The lack of lubrication was determined to be caused by improper bearing lube oil level indication due an inverted oil sight glass. It was further determined that the insufficient bearing oil level condition had existed since the performance of maintenance activities in June of 2016. The corrective action plan addresses the root cause, contributing cause, extent of condition, and extent of cause.|
|05000313/LER-2016-003||19 October 2016||Arkansas Nuclear|
On August 24, September 11, and September 15, 2016, during performance of an extent of condition evaluation related to the protection of Technical Specification (TS) equipment from external flood hazards, Arkansas Nuclear One, Unit 1 (ANO-1), identified non-conforming plant design conditions such that specific ANO-1 TS equipment was considered to not be adequately protected from tornado missiles. These are legacy design issues.
On August 24, 2016, at 0945, September 11, 2016, at 1504, and September 15, 2016, at 0958, Operations declared the affected components inoperable, implemented Enforcement Guidance Memorandum (EGM) 15-002, "Enforcement Discretion for Tornado-Generated Missile Protection Noncompliance", along with necessary compensatory measures, and subsequently declared the affected equipment operable but non-conforming.
The cause of this issue was unclear and changing regulatory requirements during original plant licensing that led to an inadequate understanding of the regulatory guidance with respect to tornado missile protection design requirements.
Interim corrective actions include implementation of compensatory strategies. Plant modifications and license basis changes are being evaluated to resolve outstanding issues.
|05000313/LER-2016-002||11 August 2016||Arkansas Nuclear|
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.
|05000313/LER-2016-001||18 May 2016||Arkansas Nuclear|
On March 19, 2016, two block-out penetrations separating the Arkansas Nuclear One, Unit 1 (ANO-1) Turbine Building from the Auxiliary Building were determined to be non-functional. The penetrations are located in the floor of Turbine Building elevation 354 ft. Below the penetrations is the Auxiliary Building, housing safety related equipment.
On March 17, 2016, it was identified that two penetration seals did not match approved fire penetration or approved flood seal details. Further investigation, completed on March 19, 2016, revealed that the two block-out penetrations were not grouted and represented a previously unknown vulnerability in a credited external flood barrier.
The apparent cause of this event was less than adequate project management control for the size and scope of the External Flood Mitigation Project associated with post Fukushima Dai-ichi resolutions and requirements set forth by the NRC.
Mitigating strategies and extent of condition reviews have been implemented for the identified conditions. Permanent repair of the deficient flood barriers is complete minus cure time. Actions to correct programmatic aspects of this condition are in progress.
|05000313/LER-2015-001||12 February 2016||Arkansas Nuclear|
On December 15, 2015, at approximately 0544, Arkansas Nuclear One, Unit 1 (ANO-1), manually scrammed during a scheduled automatic down power to 35% power for planned maintenance. The Integrated Control System (ICS) (JB) was being utilized for the down power. During the down power, oscillations occurred in the Main Feedwater (MFW) (SJ) system. The ICS was placed in manual and efforts were made to dampen the MFW oscillations. The Operators manually tripped the reactor from approximately 43% power when it became evident that an automatic reactor trip was imminent, based on the observed Reactor Coolant System (RCS) (AB) pressure rise caused by the significant reduction in MFW flow.
The direct cause of the manual plant trip is currently considered a result of placing the "B" startup valve in HAND (manual) when the valve was -36% open, which resulted in a significant underfeed condition of the "B" Once-Through Steam Generator (OTSG). There are currently two root causes considered for this condition: (1) inadequate maintenance practices applied to the ICS modules, and (2) inadequate procedural guidance to address ICS malfunctions.
|05000368/LER-2015-001||21 December 2015||Arkansas Nuclear|
On October 26, 2015, the Containment Purge and Exhaust Isolation Process Monitor was discovered to be inoperable due to not having its required sample pump in operation. The Containment Building Purge Radiation Monitor Sample Pump provides flow to the Containment Purge and Exhaust Isolation Process Monitor. Technical Specification 18.104.22.168, Table 3.3-6, requires the Containment Purge and Exhaust Isolation was in Mode 6 with refueling operations in progress while the Containment Purge and Exhaust Isolation Process Monitor was inoperable.
The apparent cause of this event was a a human performance error associated with the failure to restart the Containment Building Purge Radiation Monitor Sample Pump following manual transfer to its alternate power supply.
|05000313/LER-2014-002||22 December 2014||Arkansas Nuclear|
This report is submitted pursuant to the 30 day Special Report requirement of 10 CFR 50.46(a)(3)(ii). The guidance provided in NURGEG 1022, Revision 3, allows the reporting under 10 CFR 50.73 and 10 CFR 50.46 to be combined.
On November 25, 2014, AREVA NP Inc. notified Entergy Operations, Inc. of a deficiency in the Arkansas Nuclear One, Unit 1 (ANO-1) Emergency Core Cooling System evaluation model. When the deficiency is accounted for, the Large Break Loss-of-Coolant Accident Peak Clad Temperature was estimated to exceed 2200°F and the absolute value of the deficiency is greater than the requirement of 10 CFR 50.46(a)(3)(ii).
Exceeding 2200°F resulted in ANO-1 making an 8-hour NRC notification on November 25, 2014. See Event Notification EN 50641. The purpose of this report is to provide the information required by 10 CFR 50.46(a)(3)(ii).
|05000368/LER-2014-004||23 October 2014||Arkansas Nuclear||On June 12, 2014, at 1136 Central Standard time (CST), while shutdown in Mode 3, it was determined that on June 9, 2014, at 1820 CST Arkansas Nuclear One - Unit -2 (ANO-2) made a Mode Change from Mode 4 to Mode 3 with one of the two required Emergency Feedwater Pumps (EFW) inoperable due to a human performance error. The work instructions for the normal control system calibration performed in Mode 5 was not performed as written and did not require a second verification after critical adjustments were performed. This permitted an undetected mis-adjustment of the low governor frequency null voltage to exist within the governor control circuit resulting in EFW pump 2P-7A being inoperable. The 2P-7A inoperability resulted in a violation of Technical Specification (TS) 3.0.4 which precludes entryjn a mode or other specified condition in the Applicability statement when a Limiting Condition of Operation (LCO) is not met and the Action requires a plant shutdown if the LCO is not met within a specified interval. LCO 22.214.171.124 requires two EFW pumps to be OPERABLE in Modes 1, 2, and 3. EFW pump 2P-7A has a 72-hour Allowable Outage Time with a required plant shutdown per TS 126.96.36.199 Action statement. The condition was corrected and a surveillance test assuring Operability was completed on June 11, 2014, at 0420 CST. 2P- 7A EFW pump was declared Operable on June 11, 2014, at 0523 CST. This issue resulted in minimal safety significance.|
|05000368/LER-2014-003||26 June 2014||Arkansas Nuclear|
During severe weather on April 27, 2014, both units at Arkansas Nuclear One (ANO) were informed of a system-wide grid emergency and were ordered to come off-line as soon as possible. Both units commenced a rapid plant shutdown. ANO, Unit 2 (ANO-2) was at the end of the core life. During the shutdown, the Axial Shape Index (ASI) became more negative (power rising to the upper portion of the core) during the shutdown.
This led to one channel of the Plant Protection System (PPS) to be actuated on an ASI auxiliary trip. At this time, the direction to manually trip the reactor was given, but before the action could be taken, an automatic reactor trip occurred due to the two-out-of-four PPS logic being made up for the ASI conditions.
The cause of this condition was not effectively executing the reactivity management plan by delaying insertion of Control Element Assemblies (CEAs) and not inserting CEAs deep enough to maintain ASI within the desired control band.
Training material is being modified to include details on the dynamic effects of ASI change that occurs at the end-of-cycle. Additionally, improvements to the guidance in the reactivity plans that involve rapid plant shutdowns are being made as are changes to the standards for use of CEAs during transients.
|05000368/LER-2014-002||2 June 2014||Arkansas Nuclear|
On April 3, 2014, at approximately 1300 CST, Arkansas Nuclear One Unit 2 (ANO-2) tripped from 100% power due to a fault in 161kV Russellville East Line. The fault caused a momentary degraded voltage state on the 161kV and 500kV grid at ANO and an undervoltage condition for ANO-2 Startup #3 Transformer (SU3). This under voltage condition caused SU3 undervoltage relays to initiate a fast transfer of ANO-2 4160V bus (2A-1) and 6900V bus (2H-1), to Startup Transformer #2 (SU2). Buses ANO-2 6900V (2H-2) and 4160V (2A-2) were not allowed to fast transfer to SU2 because of operational restraints per design. The removal of power to 2A-2 caused an auto start of the ANO-2 Emergency Diesel Generator (2K-4B) due to under voltage on safety bus 2A-4 which is normally fed from 2A-2.
Bus 2A-2 slow transferred back to SU3. 2K-4B did not tie to 4160V safety bus (2A-4) as voltage had recovered prior to the diesel reaching rated speed and voltage. Bus 2H-2 was de-energized causing the loss of two Reactor Coolant Pumps (RCPs) which led to a reactor trip on low RCP speed and the actuation of the Emergency Feedwater System (EFW) on low Steam Generator Level. It was determined that a lighting strike caused a three phase fault on the 161kV Russellville East Line causing the ANO-2 trip. The corrective action is for Entergy Arkansas to review the adequacy of 161kV Russellville East Transmission Line Lightning Protection System.
|05000368/LER-2014-001||15 May 2014||Arkansas Nuclear|
While performing a post-assessment of a 10 CFR 50.59 evaluation performed in 2002 for a modification to the Arkansas Nuclear One (ANO) Unit 2 switchgear room exhaust fans, ANO identified that automatic action had been replaced with credit for manual operator action. During additional evaluations of this concern, it was identified that there was one occasion within the last three years in which the room coolers and exhaust fan configuration did not support the operability of the switchgear room without reliance on operator action, which was longer than the time allowed by Technical Specification.
The apparent cause of this condition is the inappropriate credit of operator action in place of an automatic action.
As a corrective action, caution cards were promptly placed on the Control Room hand switches and local breakers associated with the exhaust fans.
|05000368/LER-2013-004||5 February 2014||Arkansas Nuclear||On December 9, 2013, at approximately 0747 CST, Arkansas Nuclear One, Unit 2 (ANO-2), experienced an electrical fault on the Unit Auxiliary Transformer (2X-02) buses resulting in a fire and catastrophic failure of the transformer. This caused an automatic reactor and main turbine trip, lockout of the Switchyard Auto Transformer, lockout of (ANO-2) Startup 3 Transformer (2X-03) and loss of power to Arkansas Nuclear One, Unit 1 (ANO-1) Startup 1 Transformer (X-03) The switchyard auto transformer supplies one of the two credited offsite sources supplying both Startup 3 Transformer (2X-03) and Arkansas Nuclear One, Unit 1 (ANO-1) Startup 1 Transformer (X-03). A loss of one of the two available offsite power sources for ANO-2 resulted in an auto-start of the ANO-2 Emergency Diesel Generator (2K-48) to supply ANO-2 safety bus 2A-4 and initiation of the Emergency Feedwater (EFW) System. Investigations determined the most probable cause of the event that led to failure of the Unit Auxiliary Transformer began with a phase-to-ground fault on the 6900V 'C' phase non-segregated bus flexible link for 2X-02. Transformer 2X-02 protective relays designed to isolate the bus from an electrical fault actuated, but due to a disconnected lead, the Main Generator Lockout relays failed to actuate leading to 2X-02 failure. A root cause evaluation determined a flexible link for 2X-02 was not properly installed which led to an insulation breakdown at the bolted connection. The subsequent 2X-02 explosion and fire resulted from a non-landed wire due to a human performance error most likely occurring in 1995 that failed to connect the DC conductor to the output contacts for the protective relays.|
|05000368/LER-2013-003||21 October 2013||Arkansas Nuclear||On August 20, 2013, a switchyard walkdown by engineering revealed an undocumented wiring configuration associated with the Arkansas Nuclear One Unit 2 (ANO-2) Startup Transformer 3 (SU3) voltage regulator (VR) circuit. (SU3 is one of two offsite power source transformers designed to supply ANO-2). Subsequent investigation revealed that the wiring configuration would have prevented the SU3 VR from operating as designed. The VR has an automatic tapchanger designed to step up SU3 voltage in response to a low voltage condition after a twenty second time delay to maintain a pre-defined voltage control band. This twenty second time delay is designed to be bypassed for three minutes in the event of a Main Turbine Generator lockout, to allow immediate voltage adjustments as ANO-2 station loads are fast transferred from the Unit Auxiliary Transformer to the offsite SU3 transformer during worst case accident load sequencing. The discovered wiring configuration of the SU3 VR prevented the bypass of the twenty second time delay, resulting in SU3 being declared inoperable. The wiring configuration for the SU3 VR appears to have been introduced in the 2005-2006 time frame, during a switchyard improvement project by Entergy Arkansas Transmission and Distribution, which was responsible for ownership of the subject VR at that time. On August 21, 2013, a temporary modification was installed to remove the SU3 VR tap change controller twenty second time delay, which restored the SU3 operability.|
|05000313/LER-2013-001||22 August 2013||Arkansas Nuclear|
On March 31, 2013, at approximately 0750 CDT, during lifting and removal of the Arkansas Nuclear One Unit 1 (ANO-1) original Main Generator Stator (Stator), the temporary lift assembly collapsed due to failure of one of the structural columns, resulting in the Stator falling onto the turbine deck (386' elevation) and rolling down into the ANO-1 train bay (354' elevation) adjacent to Arkansas Nuclear One Unit 2 (ANO-2).
The event resulted in one fatality, multiple injuries, structural damage to the ANO-1 and ANO-2 turbine buildings, and damage to non-vital systems and electrical equipment. At the time of the event, ANO-1 was in MODE 6 and ANO-2 was in MODE 1 at approximately 100 percent power. The event resulted in a loss of offsite power for ANO-1, with both Emergency Diesel Generators (EDGs) starting to supply safety loads.
ANO-1 decay heat removal was lost for approximately four minutes. ANO-2 automatically tripped off-line after the vibration from the dropped Stator resulted in the actuation of relays in the ANO-2 switchgear located adjacent to the train bay, subsequently tripping a reactor coolant pump motor breaker. After the reactor trip, emergency feedwater was manually initiated by ANO-2 Control Room Operators. As debris fell into the train bay, an 8-inch firewater pipe was ruptured and the Alternate AC Diesel Generator electrical tie to ANO-1 was severed. At 0923 CDT that same day, water intrusion from the ruptured firewater piping into a 4160 volt breaker resulted in an ANO-2 Startup Transformer lockout, de-energizing a safety bus. An EDG automatically started as designed and supplied the affected safety bus. An ANO-2 Notification of Unusual Event was declared at 1033 CDT due to fire or explosion from an electrical fault in the 4160 volt switchgear with indications of bus damage. After damage assessment and repairs, ANO-2 returned to power operation on April 28, 2013. ANO-1 returned to power operation on August 7, 2013.
|05000368/LER-2013-002||4 April 2013||Arkansas Nuclear||On February 4, 2013, at 1255 CST, Control Room Emergency Chiller 2VE-1A breaker tripped shortly after the chiller was started. 2VE-1A is one of two control room emergency chillers common to both Arkansas Nuclear One (ANO) Unit-1 and ANO Unit-2. The 2VE-1A breaker (2B-52D5) is a Siemens 480 volt, 100 amp molded case circuit breaker. An Apparent Cause Evaluation determined that the the "C" phase load side wire lug was not properly connected when the breaker was installed on November 15, 2012, resulting in a loose connection between the lug and the breaker stab. The condition was corrected and 2VE-1A was declared operable on February 6, 2013. The apparent causes of the condition were determined to be a human performance error during breaker replacement due to the inadequate use of human performance tools and an inadequate molded case circuit breaker testing procedure which did not provide a step to perform a visual inspection of the wire grip style lug after installation. Initial corrective actions included a human performance error review and a requirement for visual verification of the wire lugs for remaining breaker replacement work orders. The Apparent Cause Evaluation provided firm evidence that the condition existed since the breaker was incorrectly installed on November 15, 2012, resulting in the inoperability of 2VE-1A. The redundant 2VE-1B Chiller was considered inoperable from November 26, 2012 to December 3, 2012, resulting in the potential inoperability of both control room emergency chillers and a condition that could have prevented the fulfillment of a safety function.|
|05000368/LER-2013-001||21 February 2013||Arkansas Nuclear|
On January 02, 2013 at 1308 CST, Arkansas Nuclear One Unit-2 (ANO-2) experienced an invalid Safety Injection Actuation Signal (SIAS), Containment Isolation Actuation Signal (CIAS), and Containment Cooling Actuation Signal (CCAS) while technicians were performing Plant Protection System (PPS) matrix testing, resulting in the auto start of the Emergency Diesel Generators, High Pressure Safety Injection (HPSI) Pumps and Low Pressure Safety Injection (LPSI) Pumps in the standby mode, and the re-positioning of numerous safety related components to their actuated state. The operating crew appropriately entered the Abnormal Operating Procedures (AOP) for inadvertent SIAS and inadvertent CIAS. In accordance with the inadvertent SIAS AOP, the operating crew restored Auxiliary Cooling Water flow from the Service Water (SW) System and restored SW flow to the Component Cooling Water (CCW) System by overriding the SIAS to the respective flow path valves. HPSI and LPSI Pumps were placed in pull-to-lock to prevent pump overheating, as procedurally directed. In accordance with the inadvertent CIAS AOP, the operating crew overrode the CIAS to CCW isolation valves to restore CCW flow to the Reactor Coolant Pumps. The SIAS initially aligned boric acid injection into the Reactor Coolant System as designed, and resulted in a reactor power decrease to approximately 87%. The invalid actuation signals were reset and HPSI/LPSI pumps were restored within one hour of actuation. ANO-2 returned to full power operation the same day.
A failure modes analysis determined that the direct cause of the event was the degradation of a PPS matrix test switch, with the Root Cause determined to be failure to implement a preventative maintenance strategy for the switch during a 1986 modification.
|05000313/LER-2012-001||12 April 2012||Arkansas Nuclear||On February 15, 2012, Arkansas Nuclear One Unit-1 (ANO-1) received the NRC 4th quarter Integrated Inspection Report identifying a noncited violation of Unit 1 Technical Specification (TS) 3.8.4, "DC Sources-Operating," TS 3.8.7, "Inverters-Operating," and TS 3.8.9, "Distribution Systems-Operating," due to the licensee's failure to complete the associated required actions prior to the specified completion times while the associated emergency switchgear room chillers were out of service for planned maintenance. Specifically, on December 7, 2011, VCH-4A Switchgear Room Chiller was removed from service to perform maintenance for 27.3 hours, and on December 19, 2011, VCH-4B Switchgear Room Chiller was removed from service to perform maintenance for 15.5 hours. During both maintenance periods, ANO-1 did not enter the subject specifications above, but entered the following: (1) TS 3.7.7 Condition "A" for one loop of Service Water System (SWS) being inoperable with an associated completion time of 72 hours, (2) TS 3.8.1 Condition "B" for one Emergency Diesel Generator inoperable with a 7 day completion time, and (3) TS 3.0.6, to support the emergency switchgear room chiller being out of service for planned maintenance. The SWS specification was applied as allowed by the ANO-1 TS Bases, considering that the switchgear room chillers were supplied by the SWS, which is the ultimate cooling medium for rooms which contain the electrical equipment. In light of the aforementioned non-cited violation, ANO-1 currently complies with all applicable switchgear TS actions (the most limiting being 8 hours) when either switchgear room chiller is out of service.|
|05000313/LER-2011-001||11 April 2011||Arkansas Nuclear||During the period beginning January 22, 2008 until January 4, 2011, Arkansas Nuclear One Unit 1 (ANO-1) periodically implemented compensatory measures during maintenance or failure of Emergency Switchgear Chillers (VCH-4A, VCH-4B), Battery Room Unit Coolers (VUC-14A, VUC-14C), or Switchgear Room Unit Coolers (VUC-2B, VUC-2D). During some of these instances, compliance with Technical Specification (TS) 3.8.4, "DC Sources - Operating" and TS 3.8.9, "Distribution Systems - Operating" was not met. ANO-1 1 did not enter or remain in the appropriate TS for an inoperable system, subsystem, train or component when all the necessary attendant non-technical specification support equipment that are required for the system, subsystem, train, component or device to perform its specified safety function are also capable of performing their support function. VCH-4A or B individually have not been shown to be capable of supporting 100% of the room cooling requirements of both trains of vital switchgear when one of the chillers is out of service without implementing additional compensatory actions. Therefore, reliance on the opposite train chiller alone is not sufficient to maintain all cooling requirements of the affected train's vital switchgear. A misapplication of industry guidance resulted in the use of non-safety related unit coolers and additional compensatory measures as an acceptable alternative. Currently, TS LCO compliance is maintained when the switchgear room cooling is removed from service.|
|05000368/LER-2010-002||21 October 2010||Arkansas Nuclear|
|05000313/LER-2010-004||22 June 2010||Arkansas Nuclear|
|05000313/LER-2010-003||9 June 2010||Arkansas Nuclear|
|05000368/LER-2010-001||25 March 2010||Arkansas Nuclear|
|05000368/LER-2009-005||2 February 2010||Arkansas Nuclear|
|05000313/LER-2009-003||17 December 2009||Arkansas Nuclear|
|05000368/LER-2009-004||19 November 2009||Arkansas Nuclear|
|05000368/LER-2009-002||6 November 2009||Arkansas Nuclear|
|05000368/LER-2009-003||5 November 2009||Arkansas Nuclear|
|05000368/LER-2008-002||6 June 2008||Arkansas Nuclear|
On April 7, 2008, at approximately 1345 CST, with the plant shutdown in Mode 3, and with all Control Element Assemblies (CEAs) withdrawn two steps in preparation for CEA drop time testing, the Control Room was informed that the software verification for the Control Element Assembly Calculators (CEACs) had not been verified and that the CEACS should be considered inoperable. The Shift Manager (SM) was told by Reactor Engineering (RE) personnel that the raw CEA inputs to the CEACs could not be used to verify CEA position.
Although the CEACs were not required to be operable in Mode 3, at least one position indicator is required to be operable for each CEA not fully inserted. At 1350, the Shift Manager directed that the reactor trip breakers be opened to comply with the associated technical specifications action statement. The cause of this event was inadequate communication between the SM and RE personnel which led to the incorrect conclusion that the CEA position indicators were inoperable. A "Lessons Learned" document regarding this event was prepared by the involved SM and was distributed to the SMs of both ANO units.
|05000368/LER-2008-001||8 May 2008||Arkansas Nuclear||On March 18, 2008, with the plant shutdown in Mode 5, the outside containment isolation valve for the chill water system did not fully close during "as-found" stroke time testing. Investigation by Operations personnel revealed that a scaffold pole was interfering with the close stroke of the valve, resulting in it remaining approximately 30 to 40 percent open. The scaffold was constructed on March 13, 2008, while the plant was in Mode 1 at 100 percent power. Since the plant was shutdown for Refueling Outage 2R19 on March 16, 2008, the valve was inoperable for a period of time longer than allowed by the Technical Specifications. The obstruction was removed, and the valve was successfully stroke tested. The cause of this event was human error in that the walkdown conducted before the scaffold was installed did not identify the subject valve as a work site interference issue. Due to the unique design of the valve associated with this event, it was determined to be an isolated occurrence. However, a "lessons learned" discussion will be conducted with the Operations staff of both ANO units regarding this event to stress the importance of walkdowns with scaffolding personnel in identifying all potential interference issues.|