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 Report dateSiteEvent description
05000410/LER-2017-00229 November 2017Nine Mile Point

On September 30, 2017 at 0134, Nine Mile Point Unit 2 declared Secondary Containment inoperable due to Secondary Containment vacuum decreasing below the technical specification limit. The condition is reportable under 10 CFR 50.72 (b)(3)(v)(C) and 10 CFR 50.73(a)(2)(v)(C) as any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material. The change in Secondary Containment vacuum was the result of changing wind conditions.

Secondary Containment was declared operable at 0135 when Secondary Containment vacuum was restored to greater than 0.25 inches of vacuum water gauge.

The event described in this LER is documented in the plant's corrective action program as IR# 04057558.

05000220/LER-2017-0032 November 2017Nine Mile Point

On September 6, 2017 at 1157, Nine Mile Point Unit 1 experienced an 'automatic reactor scram due to reactor vessel low water level. The automatic Reactor Protection System (RPS) actuation and reactor scram is reportable per 10 CFR 50.72 (b)(2)(iv)(B) and 10 CFR 50.73(a)(2)(iv)(A) as any event or condition that resulted in a manual or automatic actuation of any of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). Following the automatic scram all plant systems responded per design including High Pressure Coolant Injection (HPCI) System automatic initiation.

HPCI is a flow control mode of the normal feedwater systems, and is not an Emergency Core Cooling System.

The root cause of the scram was a failed power supply within the Proportional Amplifier, PAM-ID23E. This power supply failure resulted in the output from the module dropping out causing the #13 Feedwater Pump Flow Control Valve to close. The corrective action taken was the replacement of the failed Feedwater Level Control module, PAM- ID23E.

05000410/LER-2017-0014 October 2017Nine Mile PointOn August 5, 2017, at approximately 2235, the Nine Mile Point Unit 2 (NMP2) reactor scrammed on an automatic scram signal during performance of quarterly turbine stop valve surveillance testing. The automatic Reactor Protection System (RPS) actuation and reactor scram is reportable per 10 CFR 50.73(a)(2)(iv)(A). The definitive root cause of the equipment failure was not located but was bound to spurious actuation of load limit relays KL186 and KL187. The spurious action was caused by an intermittent ground and/or an induced voltage within the load limit circuit. This is a result of the non-fault tolerant original design of the Electro-hydraulic Control (EHC) system. The corrective action planned is replacement of the current single point vulnerable NMP2 Turbine EHC system with a fault tolerant Digital EHC system. Interim actions have also been developed to mitigate risk associated with testing of the current system until replacement can be accomplished during the 2018 refueling outage.
05000220/LER-2017-0018 February 2017Nine Mile Point

On December 10, 2016 at 08:48, Nine Mile Point Unit 1 performed a manual scram of the reactor due to increased vibrations on the main turbine. Following the scram, the High Pressure Coolant Injection (HPCI) System automatically initiated. This event is reportable under 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A) as any event or condition that resulted in a manual or automatic actuation of any of the systems listed in 10 CFR 50.72(b)(3)(iv)(B).

During performance of a load drop to 95% power in support of Turbine Stop Valve Testing, main turbine bearing vibrations rose on several bearings. The Unit 1 Reactor was scrammed and the main turbine was secured when main bearing #1 reached procedural limits. The root cause of the event was a steam leak from a threaded pipe/cap connection that was not seal welded when originally supplied from the manufacturer. The connection has now been seal welded.

A combination of tight tolerance in conjunction with the location of the steam leak resulted in the vibrations when power level was changed.

The event described in this LER is doCumented in the plant's corrective action program.

05000220/LER-2016-00226 September 2016Nine Mile Point

On Thursday July 28, 2016, at approximately 2357 hours with power level at approximately 100 percent, Nine Mile Point Unit 1 (NMP1) experienced a loss of Uninterruptible Power Supply (UPS), UPS 162B which resulted in loss of Reactor Protection System (RPS) Bus 11. Numerous half scram and half isolation signals were generated in addition to the isolation of both # 11 and # 12 Emergency Condensers (ECs).

EC # 12 was returned to standby on 7/29/2016 at 0041 hours and EC # 11 was returned to standby on 7/29/2016 at 0045 hours. The causes of this event were the failure of a UPS capacitor and the bypass power transfer set point being set too low for the type of transient. Corrective actions include immediate replacement of the failed capacitor, installation of new higher temperature rated capacitors and adjusting the low voltage bypass power transfer set point.

This event is reportable under 10CFR50.73(a)(2)(v)(B).

05000220/LER-2016-00112 July 2016Nine Mile PointOn Wednesday June 1, 2016, at approximately 1046, the secondary containment of the Nine Mile Point Unit 1 (NMP1) Reactor Building was momentarily breached when workers opened both airlock doors on elevation 261 simultaneously. The integrity of the airlock was re-established within 5 seconds when one of the doors was closed and latched. The cause of this event is personal accountability. With clear understanding of the expectations for using the airlock doors in conjunction with all mechanical barriers (lights, buzzers, monitors) functioning properly, the individual failed to use human performance tools to verify the airlock was not already being used by other individuals. This condition is reportable under 10 CFR 50.72(b)(3)(v)(C) and 10 CFR 50.73(a)(2)(v)(C).
05000410/LER-2016-0016 June 2016Nine Mile PointOn April 7, 2016, at approximately 1730 hours, the secondary containment of the Nine Mile Point Unit 2 (NMP2) Reactor Building was breached when workers opened both inner and outer airlock doors, SA262-2 and SA262-3, simultaneously. The integrity of the airlock was re-established within 4 to 5 seconds when one of the doors was closed and latched. This resulted in a momentary loss of Secondary Containment Operability (TS 3.4.3). Secondary containment differential pressure never exceeded the minimum Technical Specification limit of 0.25 inch of vacuum water gauge. The causal analysis identified that the existing notice providing airlock door usage instructions is not effective in preventing doors being opened simultaneously in all situations. Corrective actions taken include revising the notice signage at all airlock doors to increase wait time from 5 seconds to 10 seconds to allow personnel traversing the airlock to exit. NMP2 has submitted LER 2014-007, Revision 1 for similar conditions. I
05000410/LER-2015-00331 March 2016Nine Mile Point

On June 23, 2015, Nine Mile Point Unit 2 identified two separate instances where the isolation capability for the Reactor Vessel Low Water Level (Level 2) primary containment isolation valves on both divisions was not maintained during performance of surveillance testing. The events occurred on April 22, 2015, and May 5, 2015.

This event is reportable under 10 CFR 50.73 (a)(2)(v)(C) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material. The Surveillance testing on both dates was for valves powered by one division. To prevent an inadvertent full isolation signal from occurring, during the testing on the division, the power supply breakers for the division valves were opened while they were being tested.

The event described in this LER is documented in the station's corrective action program as 182518177. There are no similar event reports.

05000220/LER-2015-0043 November 2015Nine Mile Point

On Friday September 4th, 2015 at 09:16:04, Nine Mile Point Unit 1 automatically scrammed from approximately 100% rated power due to an inadvertent Main Steam Isolation Valve (MSIV) isolation. This event is reportable under 10 CFR 50.72 (b)(2)(iv)(B) and 10 CFR 50.73(a)(2)(iv)(A) as any event or condition that resulted in a manual or automatic actuation of any of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). During quarterly surveillance testing, the MSIV failed to stop its close stroke and reopen automatically per design, due to a failed MSIV pilot test valve. The root cause of the event was an inadequate application of the designed pilot test valve for MSIV control, resulting in the pilot test valve internals binding during the surveillance test. The failed pilot valve spool and cage assembly were replaced.

The corrective action to prevent recurrence is to replace the MSIV pilot valveS with an industry proven design.

The event described in this LER is documented in the plant's corrective action program.

05000410/LER-2014-0075 October 2015Nine Mile Point

(NMP2) Reactor Building was breached when workers opened both inner and outer airlock doors, R261-1 and R261-2, simultaneously while passing through. The integrity of the airlock was re-established within 4 to 5 seconds when one of the doors was closed and latched. A second opening of both airlock doors occurred at 1140 that same day. Secondary containment differential pressure never exceeded the minimum Technical Specification limit of 0.25 inch of vacuum water gauge. These events are significant in that the secondary containment was momentarily breached during replacement of the Reactor Recirculation Pump "B" seal, an activity which had the potential for draining the reactor vessel (OPDRV).

The causal analysis identified that workers did not use their human performance verification tools to ensure the opposing outer door of the airlock was closed prior to opening the inner door. Corrective actions taken include coaching and counseling for workers involved in the event on the importance of applying their human performance tools of self-checking and peer-checking when passing through secondary containment doors. A previous LER submitted on a similar event could not be identified.

05000220/LER-2015-0032 October 2015Nine Mile Point

On August 5, 2015 at approximately 1252 hours, the secondary containment at Nine Mile Point Nuclear Station Unit 1 (NMP1) was breached momentarily. Station personnel opened both inner and outer airlock doors on the Reactor Building (RB) 261 foot elevation simultaneously while traversing through the airlock.

The integrity of the airlock was re-established within 5 seconds when both doors were closed and latched. Secondary Containment differential pressure was unaffected by the event.

The cause of the event is the failure of an individual to comply with the posted expectations prior to opening the airlock door. Corrective actions taken included disciplinary action for the individual not adhering to the postings and station expectations.

NMP1 LERs 2014-004, 2014-005, 2014-006, 2015-001, and 2015-002 were provided for similar events that involved the simultaneous opening of both airlock doors.

05000220/LER-2015-00221 April 2015Nine Mile PointOn March 3, 2015, at approximately 0837 hours, the secondary containment of the Nine Mile Point Nuclear Station Unit 1 (NMP1) Reactor Building (RB) was breached when station personnel opened both inner and outer airlock doors on RB 340 foot elevation simultaneously while traversing through the airlock. The integrity of the airlock was re-established within 5 seconds when the doors were closed and latched. Secondary containment differential pressure was unaffected by this event. The cause of the event is clear and well-advertised barriers and postings for passage through the air lock doors were not followed . Corrective action included disciplinary action for the individual not adhering to the postings and station expectations. NMP1 LERs 2014-004, 2014-005, 2014-006 and 2015-001 were provided for similar events that occurred on August 13, 2014, October 16, 2014, October 20, 2014 and February 11, 2015, respectively.
05000410/LER-2015-00220 April 2015Nine Mile Point

On February 18, 2015, at 1406, Nine Mile Point Unit 2 inserted a manual reactor scram due to rapidly rising reactor water level. This event is reportable under 10 CFR 50.72 (b)(2)(iv)(B) and 10 CFR 50.73(a)(2)(iv)(A) as any event or condition that resulted in a manual or automatic actuation of any of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). The Reactor Protection System (RPS) was manually actuated, resulting in a reactor scram.

The rapidly increasing reactor water level was due to the lifting and separating of two leads on a level recorder being replaced. The root cause of the event was the technical human performance verification tools were not adequately used during the Fix-It-Now (FIN) planning process to validate plant impact since there was a bias towards a level recorder replacement not impacting the control circuit. Corrective actions taken include replacing the failed level recorder and establishing a compensatory action to require FIN Team work packages staged by the FIN team to be peer reviewed by a same-discipline technician.

The event described in this LER is documented in the plant's corrective action program as IR2454892. NMP2

05000410/LER-2015-00112 March 2015Nine Mile Point

On January 12, 2015 at 1939, Nine Mile Point Unit 2 declared secondary containment inoperable due to secondary containment vacuum decreasing below the technical specification limit. The condition is reportable under 10 CFR 50.72 (b)(3)(v)(C) and 10 CFR 50.73(a)(2)(v)(C) as any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material. The change in secondary containment vacuum was the result of sustained high winds.

Secondary containment was declared operable at 1956 when secondary containment vacuum was restored to greater than 0.25 inches of vacuum water gauge. The apparent cause evaluation identified inadequate system balancing and failure to adjust the inlet damper after filter bag removal for seasonal readiness which allowed a volume increase that was beyond the control capability of the pressure control dampers during a high wind event.

Corrective actions taken include adjusting Reactor Building intake dampers to lower supply fan flow to bring recirculation motor operated dampers into their control range and to adjust other system lineups until the dampers begin to modulate.

The event described in this LER is documented in the plant's corrective action program as IR# 2436393. NMP2

05000410/LER-2014-00114 August 2014Nine Mile Point

On February 16, 2014 at 1216, Nine Mile Point Unit 2 (NMP2) was operating at 100 percent power when an automatic actuation of the Division I and III Emergency Diesel Generators (EDG) occurred due to a loss of a 345 kV bus owned by National Grid. The bus outage resulted in the loss of off-site power source (Line 5) owned by Exelon. Automatic actuation of the EDGs is reportable under 10 CFR 50.72(b)(3)(iv)(A) and 10 CFR 50.73(a)(2)(iv)(A). The cause of the loss of Line 5 is due to a faulted current transformer associated with 345kV Breaker R210 owned by National Grid, the transmission owner. The faulted transformer caused a voltage transient for both station service and offsite power loads. This resulted in the loss of: 1) the service water radiation monitor and radwaste/reactor building vent gaseous effluent monitoring systems 2) the 'C' and 'D' Reactor Water Cleanup (WCS) filter strings, and 3) spent fuel pool cooling. The voltage transient also caused Feed Water level control valve actuator controls to lock up and go to manual operation. The causal analysis identified the failure mechanism of the CT as an insulation breakdown internal to the CT.

The corrective actions include purchasing spare CTs and performing follow up tests and repairs on damaged equipment. NMP1 LER 2008-001 and NMP2 LER 2012-004 are similar LERs submitted previously which involve the actuation of the EDGs due to a loss of Power Line 5.

05000410/LER-2014-0088 August 2014Nine Mile Point

Nine Mile Point Unit 2 (NMP2) secondary containment was declared inoperable on June 10, 2014 from 2032 until 2036. The event occurred while the plant was restoring the Reactor Building Ventilation System to normal line up. Exhaust Fan 2HVR-FN5A tripped following planned post maintenance testing which resulted in building differential pressure (dP) exceeding the Technical Specification (TS) limit of 0.25 inch vacuum water gauge. Secondary containment dP was restored within TS limits by starting the Standby Exhaust Fan. Both the TS Action Statement and plant procedure were exited at 2036 when secondary containment was declared operable. The cause of the exhaust fan trip was a faulty flow switch.

Corrective actions taken or planned to prevent a recurrence include: 1) replaced Flow Switch 2HVR- FS12A, 2) revising the Preventative Maintenance (PM) strategy for Reactor Building ventilation supply and exhaust fan flow switches, and 3) revising a plant procedure to clarify fan start requirements. There were no previously submitted similar LERs identified. The reportable condition has been documented in the plant's corrective action program as CR-2014-005610.

05000220/LER-2014-0028 July 2014Nine Mile Point

On May 8, 2014, at 1645, the results of an industry operating experience (OE) extent of condition review identified that an un-fused control circuit associated with the Unit 1 Reactor Water Cleanup Isolation Valve 12 could short circuit due to a fire in the circuit cable routing. This short circuit could cause the cable to self- heat and cause secondary fires along the associated cable route. The unanalyzed secondary fires could adversely affect safe shutdown equipment and potentially cause the loss of ability to safely shutdown as required by 10 CFR 50 Appendix R. The original plant wiring design and configuration for the containment isolation valve did not include separate overcurrent protection for motive power and control wiring. The only protection for control circuit wiring is by motive circuit fuses which are not sized appropriately to protect the control wiring. As a compensatory measure, Operations has initiated a fire inspection each shift to monitor the associated Fire Areas (1 and 10) until separate fuses are installed within the control circuitry of the motor operated valve (MOV). A similar event was reported in LER 2013-002.

This condition was entered into the Nine Mile Point (NMP) corrective action program as Condition Report (CR) 2014-004630.

05000410/LER-2014-00623 May 2014Nine Mile Point

On March 24, 2014 at 0031, while shutting down in preparation for a refueling outage, Nine Mile Point Unit 2 (NMP2) experienced a loss of Reactor Building heating due to a trip of the Auxiliary Boiler system.

While responding to lowering temperatures and rising pressure in secondary containment, secondary containment pressure degraded beyond the Technical Specification limit of 0.25 inch of vacuum water gauge.

This required declaring secondary containment inoperable. Operators responded by re-aligning the Reactor Building standby gaseous treatment system (GTS) from primary containment purge mode to reactor building suction mode and isolating the normal Reactor Building ventilation system to restore operability of secondary containment. Operators also took action to restore the auxiliary boiler system in order to support restoring Reactor Building heating and ventilation to a normal lineup. The isolation of the Reactor Building ventilation system impacted the functionality of the Vent Wide Range Gaseous Monitoring System. The event causal analysis identified that management and oversight of auxiliary boiler operation and maintenance was less than adequate resulting in poor reliability due to hardware deficiencies and chemistry control which caused ground fault trips. Corrective actions planned or taken include: 1) Revising a plant procedure to ensure operating parameters are maintained within specifications during boiler operations and 2) Revising a plant procedure to require a chemistry sample be taken each shift, analyzed and reported to operations when an auxiliary boiler is in operation. A previous LER on a similar event was not identified.

05000410/LER-2014-0059 May 2014Nine Mile Point

On March 12, 2014, at 1422 Nine Mile Point Unit 2, declared the secondary containment inoperable due to the secondary containment experiencing a positive differential pressure (dP) condition. This condition is reportable under 10 CFR 50.72 (b)(3)(v)(C) and 10 CFR 50.73(a)(2)(v)(C) as any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material. The positive dP was the result of sustained high winds from the northeast associated with Winter Storm Vulcan. The reactor building was isolated at 1630 and secondary containment declared operable at 1700 when secondary containment vacuum was restored to greater than 0.25 inches of vacuum water gauge.

The causal evaluation identified that procedural guidance does not provide operators the direction to place the Standby Gas Treatment System in service and/or isolate the Reactor Building to maintain a negative pressure in the secondary containment prior to exceeding the Technical Specification (TS) limit for secondary containment dP. Corrective actions taken or planned include revising a plant procedure to provide direction to initiate the Standby Gas Treatment System and isolate the Reactor Building during high wind conditions prior to exceeding the TS limit for secondary containment dP. The event described in this LER is documented in the plant's corrective action program as CR-2014-002028. NMP2 LER 2013-005 reported similar events.

05000410/LER-2014-0047 May 2014Nine Mile Point

On Monday March 10, 2014 at 1628 hours, Nine Mile Point Unit 2 (NMP2) experienced an actuation of the Alternate Rod Insertion (ARI) system which resulted in an automatic reactor scram from 99.2% thermal power.

An inadvertent Reactor Water Low-Low Level 2 signal from transmitters 2ISC*LT8A and 2ISC*LT8B initiated the Division I ARI which resulted in a Reactor Recirculation Pump trip and a full reactor scram. The event was caused by instrument perturbation while Maintenance I&C technicians were performing minor maintenance associated with changing labels on instrument drain valves in the vicinity of trip sensitive equipment. Safety related and other important equipment functioned properly during and after the scram. This event is reportable under 10 CFR 50.73(a)(2)(iv)(A). The causal analysis identified that station personnel have not adequately internalized the risk and implemented rigorous process and behavioral barriers to mitigate the vulnerabilities associated with work on or near trip sensitive equipment. Corrective actions taken or planned include:

1) Protect the trip sensitive equipment and 2) Implementing new fleet procedures/processes for work around trip sensitive equipment. A similar event was documented in NMP2 LER 2010-001.

05000410/LER-2014-0032 May 2014Nine Mile PointOn March 4, 2014, at approximately 0143, Nine Mile Point Unit 2 (NMP2) was manually scrammed because of rising reactor recirculation pump (RRP) seal and motor temperatures. Prior to the scram, a failure of the Uninterruptible Power Supply, 2VBB-UPS3B, to provide uninterruptible power occurred. The malfunction of the Uninterruptible Power Supply (UPS) resulted in the inboard Primary Containment cooling water isolation valves closing and a Reactor Protection System (RPS) half scram. The closing of the inboard isolation valves resulted in the loss of cooling flow to the RRP seals and motors. The cause of the UPS malfunction was a degraded subcomponent associated with the UPS. The causal analysis for this event identified that it resulted from inadequate vendor and industry guidance/operating experience associated with the maintenance of a UPS related subcomponent. Corrective actions planned or taken include replacing degraded UPS subcomponents, revising preventative maintenance strategy, and working with the vendor to identify a list of single point of vulnerability (SPV) components that can prohibit the UPS from transferring to its alternate source when needed. The reportable condition described in this LER is documented in the plant's corrective action program as CR-2014-001725.
05000220/LER-2014-00111 April 2014Nine Mile PointThis LER is submitted to acknowledge that Nine Mile Point (NMP) missed providing LERs for past occurrences reportable in accordance with10 CFR 50.72(b)(3)(v)(A) and 10 CFR 50.73(a)(2)(v)(A) as conditions that could have prevented the fulfillment of the safety function of a structure or system needed to shutdown the reactor and maintain it in a safe shutdown condition. This condition was discovered on February 12, 2014. The reportable conditions occurred twice within the past three years when APRMs were declared inoperable as a result of reactor recirculation pump (RRP) trips. In each occurrence, the APRM flow-biased control rod block and scram function remained available, though, non- conservative. The cause of Operations personnel not recognizing the APRM conditions as reportable was due to ineffective training of Operations personnel. Corrective actions taken or planned include briefings and detailed training on reporting requirements and revisions to procedures that clarify event reporting requirements.
05000410/LER-2013-00531 January 2014Nine Mile Point

On December 11, 2013 it was discovered that Nine Mile Point Unit 2 (NMP2) has not been reporting Secondary Containment inoperabilities to the Nuclear Regulatory Commission (NRC) in accordance with the administrative guidance in NUREG-1022 (Revision 3). This condition has occurred numerous times within the past three years when the Secondary Containment has been declared inoperable as a result of the Secondary Containment differential pressure (dP) dropping below the required Technical Specification (TS) minimum value of negative 0.25 inches water gauge. These historical events are reportable in accordance with 10 CFR 50.73(a)(2)(v)(C) as conditions that could have prevented the fulfillment of the safety function of a structure or system needed to control the release of radioactive material.

In each of these occurrences the safety function of the Secondary Containment remained available.

The apparent cause of these events is that training has not been effective in providing personnel the level of understanding required in order to consistently recognize when the failure of safety systems are reportable under 10 CFR 50.72(b)(3)(v)(C) and 50.73(a)(2)(v)(C).

Corrective actions include briefings and detailed training on 10 CFR 50.72(b)(3)(v)(C) and 50.73(a)(2)(v)(C) reporting requirements.

05000410/LER-2013-00431 January 2014Nine Mile Point

On December 2, 2013, at 0903, Nine Mile Point Unit 2 (NMP2) was lowering reactor power level to remove the main turbine from service to support maintenance. During the power reduction, the Low Frequency Motor Generators (LFMGs) did not start automatically. Attempts to manually start the recirculation system pumps in slow speed were unsuccessful and a manual reactor scram was inserted due to the sudden reduction in core flow.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as a condition that resulted in manual or automatic actuation of any of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). The Reactor Protection System is listed in 10 CFR 50.73(a)(2)(iv)(B).

The root cause of this event is a failure to identify that the switches in the auto transfer circuits for the reactor recirculation pumps to shift from high speed to low speed are single point vulnerable (SPV) components because they were exempted from the AP-913 classification process. Since the switches were not classified as SPV components, no mitigation strategies were developed.

Corrective actions include revision of the operating procedures to manually start the LFMG sets and not rely on the auto transfer circuitry.

There are no similar Licensee Event Reports for NMP2.

05000410/LER-2013-00320 December 2013Nine Mile Point

On October 22, 2013 it was discovered that unfused ammeter indication circuits associated with the Nine Mile Point Unit 2 (NMP2) safety-related Direct Current (DC) buses could short circuit due to a fire in the circuit cable routing. This ground fault equivalent hot short could cause the cable to self-heat and lead to secondary fires. The unanalyzed secondary fires could adversely affect safe shutdown equipment and potentially cause the loss of the ability to safely shutdown as required by 10 CFR 50 Appendix R.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(ii)(B) as a condition that resulted in the nuclear plant being in an unanalyzed condition that significantly degraded plant safety, and 10 CFR 50.73(a)(2)(ix)(A) as a condition that as a result of a single cause could have prevented the fulfillment of a safety function for two or more trains or channels in different systems.

The cause of this event is that the equipment design issue was not recognized as an unacceptable configuration. The design issue is associated with an evolving industry understanding of the 10 CFR 50 Appendix R common enclosure scope.

Corrective actions include the isolation of the affected circuits at the DC bus in order to prevent the condition from occurring, and the development, issuance and installation of a plant modification to install fuses on the safety-related DC ammeters at NMP2 to ensure adequate circuit protection to prevent the propagation of fires in additional areas due to overcurrent conditions.

05000220/LER-2013-00220 December 2013Nine Mile Point

On October 22, 2013 it was discovered that unfused ammeter indication circuits associated with the Nine Mile Point Unit 1 (NMP1) safety-related Direct Current (DC) buses could short circuit due to a fire in the circuit cable routing. This ground fault equivalent hot short could cause the cable to self-heat and lead to secondary fires. The unanalyzed secondary fires could adversely affect safe shutdown equipment and potentially cause the loss of the ability to safely shutdown as required by 10 CFR 50 Appendix R.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(ii)(B) as a condition that resulted in the nuclear plant being in an unanalyzed condition that significantly degraded plant safety, and 10 CFR 50.73(a)(2)(ix)(A) as a condition that as a result of a single cause could have prevented the fulfillment of a safety function for two or more trains or channels in different systems.

The cause of this event is that the equipment design issue was not recognized as an unacceptable configuration. The design issue is associated with an evolving industry understanding of the 10 CFR 50 Appendix R common enclosure scope.

Corrective actions include the isolation of the affected circuits at the DC bus in order to prevent the condition from occurring, and the development, issuance and installation of a plant modification to install fuses on the safety-related DC ammeters at NMP I to ensure adequate circuit protection to prevent the propagation of fires in additional areas due to overcurrent conditions.

05000220/LER-2013-00112 July 2013Nine Mile Point

On May 14, 2013, at 1145 hrs, with the reactor in the startup mode and at 3 percent thermal power, channel 11 high steam flow instrumentation for Emergency Condenser (EC) System Loop 11 alarmed due to a gross failure trip. Gross failure is a design feature to monitor for off normal electronic instrument loop component output. The failure of channel 11 high steam flow instrumentation occurred concurrently with channel 12 inoperable, resulting in the loss of EC System Loop 11 isolation capability on high steam flow.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(v)(D) as a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident.

The cause of this event is leakage from the shared high pressure sensing line for transmitters DPT-36-06C and DPT-36- 06D. The apparent cause of the leakage from the sensing line is leak by on instrument blowdown valves VLV-36-374 and VLV-89-72. Corrective actions include replacement of the instrument blowdown valves during the next refueling outage, equalizing the associated transmitters and allowing steam condensation to fill the lines, and the monitoring of output signals to ensure that the sensing lines remained full.

i ... .. -. ...

05000410/LER-2013-00225 April 2013Nine Mile Point

On February 28, 2013 at 1319, Nine Mile Point Unit 2 was operating at 100 percent power when the High Pressure Core Spray (HPCS) system pressure pump failed. At the time of the failure, the HPCS system was inoperable for planned maintenance. The HPCS system pressure pump failure was due to an electrical short caused by a turn-to-turn failure in the motor.

The cause of this event was determined to be a turn-to-turn short in the motor winding, attributed to poor manufacturer quality of the original motor.

Corrective actions include replacement of the failed motor with a rewound motor and development of a new replacement strategy for these types of motors.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(v)(D), as any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. This report constitutes a 10 CFR 21 (Part 21) notification because the motor failure that initiated the event is attributed to a manufacturing deficiency.

There are no previous LERs similar to this event.

05000410/LER-2013-00125 March 2013Nine Mile Point

On January 23, 2013 at 15:16, Nine Mile Point Unit 2 was operating at 100 percent power when Reactor Building General Area temperature switch unit 2RHS*TS85A failed, resulting in the closure of primary containment isolation valves and causing the Reactor Core Isolation Cooling (RCIC) system to isolate from the reactor vessel and become inoperable. The failure of the temperature switch unit occurred concurrently with the High-Pressure Core Spray (HPCS) system inoperable for planned surveillance testing. With both the RCIC and HPCS systems inoperable, high pressure makeup capability to the reactor core was lost from these systems.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A), as an automatic actuation of containment isolation valves in more than one system. The event is also reportable in accordance with 10 CFR 50.73(a)(2)(v), as an event that could have prevented the fulfillment of the safety function of systems that are needed to: (A) shut down the reactor and maintain it in a safe shutdown condition, and (D) mitigate the consequences of an accident.

The temperature switch failed due to age-related capacitor degradation. The apparent cause of the event is insufficient use of the corrective action program to fully implement a periodic capacitor replacement program for the Riley temperature switches. Corrective actions include replacement of the failed switch and planned refurbishment of similar units.

05000410/LER-2011-00423 December 2011Nine Mile Point

On October 23, 2011, at 09:15, Nine Mile Point Unit 2 (NMP2) was operating at 100 percent of rated thermal power when the Division I reactor water cleanup system (RWCU) differential flow - high channel was declared inoperable due to failing its channel check. A troubleshooting plan was developed to determine the cause for the failed channel check.

While performing the troubleshooting plan, at three separate times (October 24, 2011 at 01:52, 02:58, and 05:19), both the Division I and Division II RWCU differential flow timers were placed in bypass, and Technical Specification (TS) 3.3.6.1, Condition B was entered for one or more automatic functions with isolation capability not maintained. In each of the three instances, one channel of the RWCU differential flow - high function was restored to operable status within 1 hour as required by TS 3.3.6.1 Required Action B.1. In the morning of October 24, 2012 the oncoming crew recognized that bypassing both RWCU differential flow timers in this manner could have prevented the fulfillment of a safety function.

The cause of this event was human performance error. The operating crew became focused on the completion time associated with the LCO condition and never fully evaluated the Technical Specification Bases.

The crew involved in this event has been coached. An Operations department communication has been sent as a result of this event which reinforced the requirements of TS 3.0.2 Bases and the importance of an operating crew to use all available information with the Shift Manager as the single point of accountability. The RWCU system operating procedure has been revised to clarify the reportability requirements when removing both divisions of the RWCU high differential flow isolation from service. A training needs assessment has been initiated to determine if additional training is needed on TS Bases.

05000410/LER-2011-00310 October 2011Nine Mile Point

On August 10, 2011 at 2200, during power ascension from an outage with the reactor operating at approximately 15% of rated thermal power, a leak was identified on a vent pipe connected to the minimum flow line for the "A" feedwater pump. At 0016 on August 11, the reactor was manually shut down due to the unisolatable leak on the feedwater pump minimum flow line.

The leak was the result of a failed weld on the feedwater minimum flow line vent pipe due to vibration induced fatigue failure. The vibration increased due to two recent design modifications that affected the "A" feedwater pump minimum flow line. The potential for these design changes to increase vibration and adversely impact system operation had been identified, but was not anticipated to result in a failure of this type. Although the minimum flow piping had been evaluated and was being monitored, the small bore vent line had not been equally modeled or evaluated.

The vent pipe was rewelded to the minimum flow line using an improved 2:1 weld profile and a pipe-to-pipe support was installed to make the pipe more robust and less susceptible to vibration.

05000410/LER-2011-0025 October 2011Nine Mile Point

At 0152 on August 6, 2011, the containment gaseous radiation monitors went into alarm and it was identified that Reactor Coolant System (RCS) unidentified leakage was increasing. At 0205, a Technical Specifications Condition was entered for RCS unidentified leakage increase above the specified limit. The RCS unidentified leakage peaked at 11.35 gpm, which resulted in an Unusual Event being declared due to reaching an Emergency Action Level (unidentified leakage greater than 10 gpm). At 0227, commenced lowering reactor power. Reactor power was reduced to 20% and, at 0941, the Reactor Protection System was manually actuated by placing the reactor mode switch in the Shutdown position. The unidentified leakage was due to a packing leak from the "A" RCS pump discharge blocking valve. The cause of the packing leak was determined to be vibration/turbulent flow that caused packing relaxation and failure. The valve packing was replaced, torqued and the gland follower nuts were secured in place. The packing for other similar valves was re- torqued and the gland follower nuts were secured in place.

A Preventive Maintenance Surveillance Test (PMST) activity will be created to re-torque the packing for RCS pump blocking valves every two years. Additionally, a modification will be implemented to install a live loading design on the RCS pump blocking valves in an upcoming outage.

There have been two other similar LERs involving RCS valve packing leakage: Nine Mile Point Unit 1 LER-2006-001 and Nine Mile Point Unit 2 LER-2001-007.

05000410/LER-2011-00112 August 2011Nine Mile Point

On April 1, 2011, Nine Mile Point Nuclear Station, LLC (NMPNS) determined that, based on the results of completed as-found testing, four (4) of eighteen (18) Main Steam Safety Relief Valves (SRVs) mechanically actuated at pressures that exceeded the allowable Technical Specification (TS) limit, which is the TS- specified setpoint plus or minus 3 percent. These 18 SRVs had been removed and replaced with pre-tested, certified SRVs during the 2010 Nine Mile Point Unit 2 (NMP2) refueling outage. NMP2 TS 3.4.4 requires the safety function of sixteen (16) SRVs to be operable in reactor operating modes 1, 2, and 3. Since the as- found testing determined that 4 of the 18 SRVs were inoperable for an indefinite period of time during the operating cycle that preceded the 2010 refueling outage, it is probable that NMP2 operated longer than the TS allowed Completion Time.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as any operation or condition which was prohibited by the plant's Technical Specifications.

The cause for the 4 SRVs exceeding the allowable as-found setpoint tolerance is attributed to inaccurate as- left lift pressure settings that resulted from the use of nitrogen as the test medium for SRV testing performed onsite prior to the 2010 refueling outage. Nitrogen testing of the NMP2 SRVs is no longer being performed.

The SRV testing is now being conducted at an offsite test facility using saturated steam as the test medium.

05000220/LER-2011-0021 July 2011Nine Mile Point

On May 3, 2011., Nine Mile Point Nuclear Station, LLC (NMPNS) was informed by its fuel vendor, GE Hitachi (GEH), of a change in its Emergency Core Cooling System (ECCS) evaluation model that would affect the calculation of peak cladding temperature (PCT) and maximum local oxidation (MLO) at Nine Mile Point Unit 1 (NMP1). This change was required to address three individual errors and a model change identified by GEH for the NMP1 calculation of record. On May 6, 2011, based on the information provided by GEH, NMPNS determined that correction of one of the identified errors and the model change would result in an increase in the calculated PCT and MLO above the acceptance criteria delineated in 10 CFR 50.46.

Accordingly, this event is reportable in accordance with 10 CFR 50.46(a)(3)(ii).

The causes of this event are non-conservative errors and a model change in the ECCS evaluation model.

The NMP1 evaluation model was revised prior to startup from the Spring 2011 refueling outage to address the potential errors and the model change (i.e., prior to formal GEH notification). The NMP1 Maximum Average Planar Linear Heat Generation Rate limits were adjusted through a plant monitoring system update to maintain the existing PCT and MLO margins.

05000220/LER-2011-00130 June 2011Nine Mile Point

At 2051 on May 2, 2011, Nine Mile Point Unit 1 (NMP1) experienced a turbine trip while operating at approximately 47 percent power (867 MWth). The main turbine master trip solenoid (MTS) actuated due to oil pressure fluctuations that allowed the pressure to drop below the MTS trip setpoint. These fluctuations were caused by leaking fittings on the MTS oil supply lines, binding of the secondary speed relay linkage, and main shaft oil pump discharge pressure fluctuations. The turbine trip initiated the high pressure coolant injection (HPCI) system as designed. The scram caused a drop in the reactor pressure vessel (RPV) water level that was mitigated by the HPCI injection. At 2052, RPV water level was restored above the HPCI low level actuation setpoint and the HPCI system initiation signal was reset.

The root cause of the event was inadequate implementation of management job performance standards which resulted in the development and implementation of work performance documents which lacked sufficient detail associated with turbine maintenance activities.

The immediate corrective action was to repair the turbine exciter/generator Falk coupling installation, replace the tubing and connections to the MTS supply lines, repair the secondary speed relay linkage, and repair the gears to the main shaft oil pump. Procedures will be developed to detail the disassembly, inspection, reassembly and testing of the NMP1 turbine, generator, exciter and control components.

There have been no similar LERs at NMP1.

05000220/LER-2008-0017 July 2008Nine Mile Point

On May 13, 2008, at 0806 hours, with Nine Mile Point Unit 1 (NMPI) operating at 100% steady state reactor power and one of two 115 kV offsite power lines (Line 1) out of service for planned maintenance, a loss of the second 115 kV offsite power line (Line 4) occurred. Line 4 is a shared line with the James A. Fitzpatrick Nuclear Power Plant. As a result of the loss of Line 4, both emergency diesel generators auto-started and commenced carrying emergency loads. The Loss of Offsite Power (LOOP) also resulted in tripping of one of five Reactor Recirculation pumps and tripping of the operating Spent Fuel Pool (SFP) cooling pump, as designed. Operators entered applicable Special Operating Procedures (SOPs) and took appropriate corrective actions. At 0825 hours, an Unusual Event (UE) was declared and the required notifications were made.

The cause for the loss of Line 4 was external to Nine Mile Point (NMP) and was determined to be a switchyard equipment malfunction at the James A. Fitzpatrick Nuclear Power Plant switchyard.

On May 13, 2008, at 0843 hours, Line 1 was restored to service. The UE was terminated at 1022 hours and the required notifications were made. On May 16, 2008, at 0515 hours, Line 4 was restored to service.