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05000498/LER-2017-002 | South Texas | 22 January 2018 | Unit 1 Condition Prohibited by Technical Specifications Due to Inoperable Control Room Envelope Makeup Filtration System Heating Coil LER 17-002-00 for South Texas Project, Unit 1, Regarding Condition Prohibited by Technical Specifications Due to Inoperable Control Room Envelope Makeup Filtration System Heating Coil | On November 23, 2017, a routine surveillance on the South Texas Unit 1 Train "C" Control Room Makeup and Cleanup Filtration System failed due to the Train "C" control room makeup filtration system heater de-energizing approximately two minutes after actuation. The makeup filtration system heater de-energized due to an improperly configured jumper on a circuit board associated with the Train "C" control room makeup filtration unit outlet low flow switch. The circuit board had been installed with the improperly configured jumper on September 27, 2017. The circuit board was properly configured and returned to service on November 24, 2017. This resulted in the Train "C" Control Room Makeup and Cleanup Filtration System being inoperable for 58 days; the associated Technical Specification allowed outage time for this condition is 7 days. The cause of the event is the maintenance work instructions did not include steps to: (1) ensure that the circuit board jumper is in the correct position, and (2) conduct a post-maintenance test to ensure proper operation of the heaters. As a corrective action, the applicable maintenance work instructions will be revised to (1) ensure that the circuit board jumper is in the correct position, and (2) conduct a post-maintenance test to ensure proper operation of the heaters. |
05000254/LER-2017-003 | Quad Cities | 21 September 2017 17 November 2017 | Control Room Emergency Ventilation Air Conditioning Piping Refrigerant Leak Due to High Cycle Fatigue LER 17-003-00 for Quad Cities, Unit 1, Regarding Control Room Emergency Ventilation Air Conditioning Piping Refrigerant Leak Due to High Cycle Fatigue | On 09/21/2017 at 1550, Operations started Control Room Emergency Ventilation (CREV) Air Conditioning (AC) for Tracer Gas Testing. Per Operations instructions, Mechanical Maintenance went to inspect the Control Room Emergency Ventilation system for refrigerant leaks before Tracer Gas Testing was started. Mechanical Maintenance reported a refrigerant leak on the discharge piping of the compressor, right above the inlet to the condenser. The leak was at the expansion joint of a fitting. The safety significance of this event was minimal. The cause of the refrigerant leak on the Control Room Emergency Ventilation compressor discharge pipe fitting into the condenser was due to high cycle fatigue. The corrective action was to replace the failed Control Room Emergency Ventilation compressor discharge pipe fitting. The CREV AC system is a single train system. Given the impact on the CREV AC system, this report is submitted in accordance with the requirements of 10 CFR 50.73(a)(2)(v)(D), which requires the reporting of any event or 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. |
05000397/LER-2016-003 | Columbia | 20 November 2016 29 August 2017 | Failure of Fan to Start Results in Momentary Increase in Secondary Containment Pressure LER 16-003-01 for Columbia Regarding Failure of Fan to Start Results in Momentary Increase in Secondary Containment Pressure | On November 20, 2016 at 1402 PST, Secondary Containment (NH) (Reactor Building) became inoperable due to pressure increasing above the Technical Specification limit of -0.25 inches of water gauge (inwg). While the plant was ascending in power, the Reactor Building exhaust air fan unexpectedly failed to start in manual during post-maintenance testing. Prior to this event, Reactor Building Heating, Ventilation and Air Conditioning (VA) (HVAC) System A was running. Per station procedures, System A was stopped and System B was to start. The fan's failure to start resulted in no Reactor Building fans running, and increased Reactor Building pressure. For a time period of less than one minute, Secondary Containment pressure was not maintained less than or equal to -0.25 inwg. Immediate recovery actions by Operations personnel included manually starting Reactor Building HVAC System A, which quickly restored Secondary Containment pressure to less than or equal to -0.25 inwg at 1403 PST. While TS limits were exceeded for this short time period, the resulting pressure excursion was bounded by analytical results; and thus, there were no safety consequences for this condition. This event was reported under reporting criteria 10 CFR 50.72(b)(3)(v)(C) and 10 CFR 50.72(b)(3)(v)(D) as Event Notification #52382. The cause of the exhaust fan's failure to start was a faulty control switch for the fan. Corrective actions for this event include replacement of the control switch. There were no other event-related equipment malfunctions. |
05000397/LER-2017-003 | Columbia | 26 June 2017 24 August 2017 | Momentary loss of Secondary Containment due to Weather LER 17-003-00 for Columbia Generating Station Regarding Momentary Loss of Secondary Containment due to Weather | On June 6, 2017 at 1756 PDT hours Secondary Containment pressure exceeded the Technical Specification (TS) limit during a period of inclement weather. At 1756 PDT Secondary Containment was declared inoperable and operations personnel entered TS Action Statement 3.6.4. I .A and subsequently exited at 1800 PDT. Secondary Containment pressure was restored automatically by system response and operator action was not required. The direct cause of the momentary loss of Secondary Containment was due to slow system response to maintain a vacuum in Secondary Containment during a period of inclement weather. The interim planned corrective action is to verify proper operation and tuning of the Secondary Containment instrumentation. Additionally Columbia Generating Station is pursuing the change to TS requirements by adopting TSTF-551, Revise Secondary Containment Surveillance Requirements. This condition is being reported under 10 CFR 50.73(a)(2)(v)(C) and 10 CFR 50.73(a)(2)(v)(D) for an event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material and to mitigate the consequences of an accident. |
05000387/LER-2017-004 | Susquehanna | 9 June 2017 4 August 2017 | Secondary Containment Declared Inoperable Due to Failure of an Exhaust Fan Breaker. LER 17-004-00 for Susquehanna, Unit 1, Regarding Secondary Containment Declared Inoperable Due to Failure of an Exhaust Fan Breaker | On June 9, 2017 at approximately 0509 hours, Secondary Containment Zone 3 differential pressure was lost during a routine restoration due to the failure of the Unit 1 Zone 3 'A' Reactor Building Exhaust Fan. Technical Specification Surveillance Requirement (SR) 3.6.4.1.1 was not met. Zone 3 differential pressure was recovered to > 0.25" WG (Water Gage) by placing Unit 1 Zone 3 Filtered Exhaust to STOP and allowing Unit 2 Zone 3 to recover differential pressure. Zones 1 and 2 were not affected. This event is being reported under 10 CFR 50.73(a)(2)(v)(C) as a condition that could have prevented the fulfillment of a safety function. The cause was determined to be a broken ring terminal on the breaker which prevented the fan from starting. Maintenance replaced the ring terminal and re-terminated the wire. There were no actual consequences to the health and safety of the public as a result of this event. |
05000293/LER-2017-001 | Pilgrim | 16 January 2017 17 July 2017 | Reactor Building Isolation Dampers Failed to Isolate LER 17-001-01 for Pilgrim Nuclear Power Station Regarding Reactor Building Isolation Dampers Failed to Isolate | Station (PNPS) was performing surveillance testing of secondary containment isolation dampers when dampers AO-N-82 and AO-N-83, refueling floor supply isolation dampers, failed to fully close when the control switches were taken to close. The failure of dampers AO-N-82 and AO-N-83 to fully close resulted in a loss of safety function for secondary containment, causing immediate entry into Limiting Condition for Operation (LCO) Action Statement (AS) 3.7.C.2.a, at 1155 hours. This LCO AS was exited at 1206 hours when the dampers were verified closed. An 8-hour non-emergency notification was made in accordance with 10 CFR 50.72(b)(3)(v), any event or condition that at the time discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to: (C) Control the release of radioactive material; or (D) Mitigate the consequences of an accident. In addition, this notification is being conservatively made by PNPS in accordance with 10 CFR 50.73(a)(2)(i)(B), as a condition that was prohibited by Technical Specifications. The reactor building isolation dampers were cleaned, lubricated and post-work tested. PNPS has returned the dampers to operable status. Planned action to prevent recurrence is to revise the preventive maintenance strategy. There was no impact to public health and safety from this condition. |
05000387/LER-2017-003 | Susquehanna Susquehanna Steam Electric Station Unit 2 05000-387 | 5 May 2017 | Susquehanna Steam Electric Station Unit 1 05000387 LER 17-003-00 for Susquehanna, Units 1 and 2, Regarding Loss of Secondary Containment Zone 3 Due to Fan Trip | On March 8, 2017 at approximately 0239 hours, Secondary Containment Zone III (Unit 1&2 Reactor Bui ding) differential pressure lowered to less than the Technical Specification (TS) limit of 0.25 in w.g. due to due to Load Center Breaker 26240-021 (supply breaker to 2Y246) being returned to service without Motor Control Center (MCC) Breaker 26246-023 (supply breaker to 2Y246) restored. As a result, TS 3.6.4.1 Surveillance Requirement (SR) 3.6.4.1.1 was not met due to the loss of vacuum. The condition is being reported in accordance with 10 CFR 50.73(a)(2)(v)(C) as an event or condition that could have prevented fulfillment of a safety function. The cause of the event was less than adequate procedure use and adherence. Corrective actions included a communication to Operators and a revision to the Procedure and Work Instructions Use and Adherence procedure to perform a second check for non-conditional procedure steps. There were no actual consequences to the health and safety of the public as a result of this event. |
05000458/LER-2017-002 | River Bend | 18 February 2017 18 April 2017 | Loss of Safety Function of Onsite Electrical Distribution Due to Malfunction of Control Building HVAC System LER 17-002-00 for River Bend Station, Unit 1, Regarding Loss of Safety Function of Onsite Electrical Distribution Due to Malfunction of Control Building HVAC System | On February 18, 2017, at 3:37 p.m. CST, while a refueling outage was in progress, the operators were shifting subsystems of the main control building ventilation system. The Division 2 "B" chiller had been in service, and it was intended to start the Division 1 "C" chiller to facilitate the outage work schedule. After the swap, operators noted that the air flow was abnormally low, and within approximately four minutes, the "C" chiller tripped. The operators were unsuccessful in attempts to restore the Division 2 subsystem to service;and the abnormal operating procedures for the loss of control building ventilation were then implemented. The electrical distribution subsystems in the control building were declared inoperable due to the loss of the ventilation system. This condition is being reported in accordance with 10 CFR 50.73(a)(2)(v)(A). As described in the causal analysis, a circuit breaker manufacturing defect that violated the single failure requirements of 10 CFR 50 Appendix A, General Design Criteria, was discovered. This is being reported in accordance with 10 CFR 50.73(a)(2)(ii)(B) as an unanalyzed condition. During the restoration of the ventilation system, main control room temperature increased from approximately 73F to 81F as recorded in the operator's logs. No high temperature alarms from the electrical equipment rooms actuated. Thus, this event was of minimal significance to the health and safety of the public. |
05000352/LER-2017-001 | Limerick | 27 January 2017 | Condition Prohibited by TS due to Parts Quality Issue LER 17-001-00 for Limerick Generating Station, Units 1 and 2 Regarding Condition Prohibited by TS due to Parts Quality Issue | Over a period of approximately one month, the OB Main Control Room (MCR) Heating, Ventilating and Air Conditioning (HVAC) system experienced four failures. Troubleshooting was completed for each of the failures and for three of the failures the cause was determined to be an intermittent dropout or chattering of the Loss of Offsite Power (LOOP) start relay for two fans (0B-V116 MCR Supply and OB-V121 MCR Return Fans). The fourth failure was due to a contactor in the Motor Control Center (MCC) for the OB-V116 MCR Supply Fan. On 11/29/16 the second failure occurred on the LOOP start relay for the OB-V116 MCR Supply fan. The investigation identified a manufacturing defect of the Agastat/Tyco ETR Relays in the lot of relays used for the recent preventative maintenance (PM) relay replacements. The relays were determined to be unreliable since the initial PM replacement on 10/19/16 until 12/5/16, when the quality issue was identified and relays from a different lot were installed. The B train of MCR HVAC was determined to be inoperable due to the relay issue for a period of 47 days, which is greater than the allowable Limiting Condition for Operation (LCO) action window of 7 days (per TS 3.7.2.a.1) for an inoperable Control Room Emergency Fresh Air System (CREFAS) train. Therefore, this was a condition prohibited by Technical Specifications (TS). |
05000530/LER-2016-001 | Palo Verde | 24 December 2015 10 January 2017 | Control Room Essential Filtration System Air Filtration Unit Failure Resulting in a Condition Prohibited by Technical Specifications LER 16-001-01 for Palo Verde, Unit 3, Regarding Control Room Essential Filtration System Air Filtration Unit Failure Resulting in a Condition Prohibited by Technical Specifications | On July 20, 2016, PVNGS received Unit 3 "B" train (3B) control room essential air filtration unit (AFU) carbon sample test results that exceeded the acceptance criteria of the Technical Specification (TS) Ventilation Filter Testing Program. The Unit 3 control room (CR) staff declared the AFU inoperable and entered TS Limiting Condition for Operation (LCO) 3.7.11, control room essential filtration system (CREFS). The carbon filter replacement and testing was completed, and the Unit 3 CR staff declared the 3B CREFS AFU operable on July 24, 2016. The investigation determined the 3B CREFS AFU was inoperable since December 17, 2015, which exceeded the Required Action Completion Time for Conditions A and C of LCO 3.7.11 on December 24, 2015 and Condition E during movement of irradiated fuel. The direct cause of this event was exposure of the 3B CREFS AFU carbon filter to a high amount of volatile organic compounds (VOCs) during a CR renovation project. The apparent cause was a lack of knowledge and recognition by PVNGS personnel to identify and properly mitigate the effects of the project on the CREFS AFU resulting in inadequate guidance for controlling all potential sources of VOCs. Applicable change process and work control procedures have been revised to ensure flooring and furniture replacements that could impact the CREFS AFU are evaluated as potential sources of VOCs prior to performing work. No previous similar events have been reported by PVNGS in the last three years. |
05000263/LER-2016-002 | Monticello | 4 August 2016 30 September 2016 | Inadequate Appendix R Fire Barrier Impacts Safe Shutdown Capability LER 16-002-00 for Monticello Regarding Inadequate Appendix R Fire Barrier Impacts Safe Shutdown Capability | On August 4, 2016, while performing a Fire Protection/Appendix R self-assessment, it was discovered that the floor between the Cable Spreading Room (CSR) and the Plant Administration Building (PAB) basement is not an adequate Appendix R fire barrier. Because the CSR and the PAB are located in the same Fire Area (FA), a fire in the PAB could spread to the CSR requiring evacuation of the control room (CR). When the CR is evacuated, alternate shutdown activities are performed at the Alternate Shutdown System (ASDS) Panel. The travel path used to access the ASDS Panel following control room evacuation traverses the same fire area in the PAB. This unanalyzed condition resulted from the determination that because of the inadequate fire barrier, a fire in the PAB would now require use of an alternate shutdown strategy to safely shutdown the reactor. However, the alternate shutdown strategy requires that the operators traverse from the control room through the PAB Fire Area to access the alternate shutdown equipment. This path could be impacted by the PAB fire. In response to this discovery an hourly fire watch was established. |
05000483/LER-2016-001 | Callaway | 20 April 2016 20 June 2016 | Control Room Air Conditioning Inoperability Due To Essential Service Water Pressure Transient LER 16-001-00 for Callaway, Unit 1, Regarding Control Room Air Conditioning Inoperability Due to Essential Service Water Pressure Transient | On 4/20/2016, Callaway received preliminary analysis results showing that during a Design Basis Accident (DBA) the 'B' Train Control Room Air Conditioning System (CRAGS) would experience a pressure transient in the associated cooling water system greater than what is experienced during Engineered Safety Feature Actuation Signal (ESFAS) testing. This condition could damage the NC unit's gaskets, as evidenced during ESFAS testing completed on 4/14/2016, resulting in the affected CRAGS and Control Room Emergency Ventilation System (CREVS) trains not being capable of performing their required safety function. This event is being reported as a condition prohibited by Technical Specifications, an unanalyzed condition, and a condition that could have prevented fulfillment of a safety function. The root cause of the event is that the original Essential Service Water (ESW) system design did not appropriately account for water column separation and collapse pressure transients inherent during operation. Following the 'B' train ESFAS testing on 4/14/2016, more robust gaskets were installed in affected components. A complete evaluation of the pressures and dynamic forces experienced by all ESW system subcomponents will be performed. The results will be compared to current design limits, and appropriate modifications will be performed to ensure sufficient margin exists in the plant design. |
05000387/LER-2016-009 | Susquehanna | 26 May 2016 | Valid Primary Containment Isolation Actuation during Local Leak Rate Testing due to Human Performance Error LER 16-009-00 for Susquehanna, Unit 1, Regarding Valid Primary Containment Isolation Actuation During Local Leak Rate Testing Due to Human Performance Error | On March 31, 2016 at approximately 06:03, while performing lineups for Local Leak Rate Testing (LLRT), the Control Room received a Division two (2) Primary Containment Isolation System (PCIS) alarm along with a Division two (2) Heating Ventilation Air Conditioning (HVAC) isolation, and Standby Gas Treatment (SBGT) and Control Room Emergency Outside Air Supply System (CREOASS) initiation. This was shortly followed by the Division one (1) Primary Containment Isolation System (PCIS) alarm along with a Division one (1) Heating Ventilation Air Conditioning (HVAC) isolation, and Standby Gas Treatment (SBGT) and Control Room Emergency Outside Air Supply System (CREOASS) initiation. The valid actuation signal was the result of the performance of four (4) LLRT procedures concurrently for four (4) separate drywell pressure instruments. These instruments are divisional with each powered by a different channel. Placing each in "TEST" mode, resulted in bringing both the Division one (1) and Division two (2) isolation logic. The cause of the valid actuation signal was less than adequate procedure use and adherence by Operations staff members. Corrective action included coaching and remediation of an individual involved in confirming the position of the test switch, communication to the Operations organization and revision to the LLRT procedures. There was no operational impact as a result of this this event due to the plant being in Mode 5. This event resulted in a eight (8) hour Emergency Notification System (ENS) communication pursuant to 10 CFR 50.72(b)(3)(iv)(A). This Licensee Event Report (LER) is being communicated pursuant to 10 CFR 50.73(a)(2)(iv)(A). |
05000387/LER-2016-003 | Susquehanna | 6 May 2016 | Unit 2 Zone 3 HVAC unable to maintain Zone 3 differential pressure greater than 0.25 in wg LER 16-003-00 for Susquehanna, Unit 1, Regarding Unit 2 Zone 3 HVAC Unable to Maintain Zone 3 Differential Pressure Greater Than 0.25 in wg | On March 8, 2016 at 0232 hours Secondary Containment Zone Ill ventilation differential pressure lowered to 0.16" inch of vacuum water gauge (WG) when securing Unit 1 Zone Ill ventilation for a routine preventative maintenance activity. Required differential pressure per Surveillance (SR) 3.6.4.1.1 could not be maintained in the intended alignment and Technical Specification (TS) 3.6.4.1 was entered for Unit 1 and Unit 2. Zone Ill ventilation was restored to the original alignment and Zone Ill differential pressure recovered to > 0.25" WG at 0335 hours. This event is being reported under 10 CFR 50.73(a)(2)(v)(C) and per the guidance of NUREG 1022 Rev 3 section 3.2.7 as an event or condition that could have prevented fulfillment of a safety function. There is no redundant Susquehanna Secondary Containment System. There were no actual or potential consequences to the health and safety of the public as a result of this event. An engineering evaluation concludes no safety system functional failure (SSFF) actually occurred as a result of this event. The apparent cause is less than adequate design of the outside air dampers. The corrective action for this condition is an engineering change that allows the closing of the upper and lower damper sections to be operated separately for the reactor building HVAC supply systems. |
05000461/LER-2016-002 | Clinton | 13 February 2016 13 April 2016 | Trip of Fuel Building Ventilation Exhaust Fan Due to Moisture Formation Resulting In the Loss of Secondary Containment Vacuum LER 16-002-00 for Clinton, Unit 1, Regarding Trip of Fuel Building Ventilation Exhaust Fan Due to Moisture Formation Resulting In the Loss of Secondary Containment Vacuum | On 02/13/2016 at 0206 (CST) the plant was at 99 percent reactor power when Fuel Building Exhaust Fan "A" (1VFO4CA) tripped due to indicated high Secondary Containment (SC) vacuum during routine venting of the drywell per plant procedures. Following the fan trip, SC vacuum degraded, eventually exceeding the Technical Specification (TS) limit of 0.25 inch vacuum water gauge. The TS Limiting Condition for Operation (LCO) 3.6.4.1 Required Action A.1 and an Emergency Operating Procedure were entered. Plant Operations subsequently started the Standby Gas Treatment System (VG) and restored Secondary Containment within TS limits. An investigation determined that ice formed in the sensing line causing an inaccurate Secondary Containment vacuum reading on the indication and control loop for 1VFO4CA. This caused 1VFO4CA to trip which in turn led to a loss of Secondary Containment vacuum. A cause evaluation established that prior instrument sensing line designs did not recognize the potential to trap water in the sensing line to the Secondary Containment pressure instrumentation. Corrective actions will include completing an engineering change to install an alternate Fuel Building Ventilation (VF) system sensing line design to prevent moisture accumulation line to ensure accurate indication and control of Secondary Containment pressure. This event is reportable under 10 CFR 50.73(a)(2)(v)(C). |
05000254/LER-2015-010 | Quad Cities | 7 December 2015 5 February 2016 | Loss of Control Room Emergency Ventilation System Due to Differential Pressure Switch Failure LER 15-010-00 for Quad Cities, Unit 1, Regarding Loss of Control Room Emergency Ventilation System Due to Differential Pressure Switch Failure | system train "B" in support of planned maintenance on the non-safety related train "A". The CREV train "B" did not start. Once the CREV train "B" system failed to start, the non-safety related train "A" was restarted. Proper operation of the CREV system and CREV air conditioning (NC) systems could not be ensured, so both CREV and CREV AC system were declared inoperable. As a result, Technical Specification (TS) 3.7.4, Condition A, and TS 3.7.5, Condition A were entered. The cause of the CREV train "B" system failure to start was the differential pressure switch, which is installed in a vibration susceptible location on the ductwork. This differential pressure switch makes up the interlock between the CREV train "B" system and the non-safety related Control Room HVAC train "A". The differential pressure switch's normally open contacts had temporarily welded together not allowing the starting signal to be received by the CREV train "B" system. Corrective actions included replacing the differential pressure switch. A future corrective action will relocate the differential pressure switch off of the ductwork to minimize the vibration effects. The safety significance of this event was minimal. Given the impact on the CREV system, which is common to both units, this report is submitted (for Units 1 and 2) in accordance with the requirements of 10 CFR 50.73 (a)(2)(v)(D), which requires the reporting of any event or 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. |
05000387/LER-2015-003 | Susquehanna | 26 January 2016 | Secondary Containment Inoperability Due to Failure to Meet Technical Specification Surveillance Requirement 3.6.4.1.1 LER 15-003-01 for Susquehanna, Unit 1, Regarding Secondary Containment Inoperability Due to Failure to Meet Technical Specification Surveillance Requirement 3.6.4.1.1 | On April 21, 2015, at 2258 hours, the Reactor Building ventilation system was unable to maintain a negative pressure in Zone III of Secondary Containment, resulting in entry into Limiting Condition of Operation (LCO) 3.6.4.1, Condition A, for failure to meet Surveillance Requirement (SR) 3.6.4.1.1 on Units 1 and 2. Because the cause analysis was not complete at the time the original LER was submitted, this supplement is being submitted in accordance with NUREG-1022, Rev. 3, Section 5.1.5, Supplemental Information and Revised LERs, to disclose the final cause determination and corrective actions generated. Per Technical Specification (TS) 3.6.4.1, Secondary Containment must be maintained at 0.25 inches water column (in. w.c.) vacuum. This event was caused by a unique equipment line up coupled with high winds. The apparent cause was determined to be inadequate risk assessment of the test alignment. Corrective actions included reassessing the risk of this alignment and multi-department reviews of test procedures within the Extent of Condition to ensure risk is properly assessed. There were no actual consequences to the health and safety of the public as a result of this event. An engineering evaluation determined no Safety System Functional Failure actually occurred as a result of this event. |
05000461/LER-2016-001 | Clinton | 20 January 2016 | 1 OF 4 | On January 20, 2016 at 1311, during planned clean and inspect maintenance activities on the 4160/480 Volt Unit Substation K (0AP52E), the Unit Substation K switchgear breaker OAP52E-5D for Continuous Containment Purge (CCP) exhaust fan "A" was racked out which resulted in tripping off the CCP "B" exhaust fan. This event caused Clinton Power Station (CPS) to enter one hour Required Action A.1 under Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.6.1.4, Primary Containment Pressure, due to primary to secondary containment differential pressure being greater than +0.25 psid. Operations staff took appropriate actions to rack in breaker OAP52E-5D to restart CCP "B" exhaust fan, restore primary to secondary containment differential pressure within limits at 1339. Event Notification #51669 was transmitted to the NRC on January 20, 2016 at 1731. The root cause of this event is the station did not validate assumptions resulting in an inadequate work package. Corrective actions include updating the maintenance planning checklist, performing a read and sign and presenting a case study to maintenance planning personnel on this event. This event is reportable under 10 CFR 50.73(a)(2)(ii)(B) as an unanalyzed condition and 10 CFR 50.73(a)(2)(v)(D) as a condition that could have prevented fulfillment of a safety function. |
05000397/LER-2015-007 | Columbia | 9 November 2015 7 January 2016 | REACTOR BUILDING PRESSURE GREATER THAN TECHNICAL SPECIFICATIONS REQUIREMENT LER 15-007-00 for Columbia Regarding Reactor Building Pressure Greater Than Technical Specifications Requirement | On November 9, 2015 at 20:40 PST, Secondary Containment (Reactor Building) became inoperable due to pressure increasing above the Technical Specifications (TS) limit of -0.25 inches water gauge (inwg). At the time of the event the Division 2 Reactor Building Heating, Ventilation and Air Conditioning System (HVAC) was controlling Secondary Containment differential pressure. Power supply E-E/S-299 then failed, causing Division 2 Secondary Containment Pressure controller to lose power. This resulted in the Division 2 Reactor Building Exhaust Fan flow being reduced, causing Secondary containment pressure to rise above TS limit of -0.25 inwg. Operations personnel manually started the Division 2 SGT lead fan to restore negative pressure. The lead fan operated at max flow (due to the failure of E-E/S-299) resulting in the restoration of Secondary Containment pressure to within TS limits. The Division 1 HVAC was manually started, allowing Operations personnel to manually secure the Division 2 SGT lead fan and maintain Secondary Containment pressure. The direct cause for the loss of E-E/S-299 was due to an incorrect lug size installed in the fuse block during initial construction. Current procedures are adequate to prevent a similar error. 26158 R6 NRC Form 366 (01-2014) APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/31/2017 Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by intemet e-mail to Inf000llects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. |
05000254/LER-2015-009 | Quad Cities | 27 July 2015 | Loss of Control Room Emergency Ventilation System Due to Air Filtration Unit Damper Failure | Emergency Ventilation (CREV) System, technicians noticed that the 'B' Air Filtration Unit (AFU) Booster Fan discharge damper became stuck in a partially open position following the 'B' AFU Booster Fan trip on a high ammonia input signal. Due to the uncertainty of being able to achieve rated airflow for the CREV System caused by recirculation that would result from running the 'A' AFU Booster Fan with the 'B' Booster Fan discharge damper partially stuck open, the CREV System was declared inoperable and surveillance testing was secured. As a result, Technical Specification 3.7.4, Condition A, was entered. The cause of the damper failure was due to inadequate clearance between the damper seat sealing area and the damper blade to shaft fasteners which resulted in misalignment which caused the damper shaft to bend and the damper to become stuck. Corrective actions included securing the stuck damper in the closed position and evaluating all CREV System dampers. A preventative maintenance task will be developed to stroke and inspect the dampers to identify binding; modifications will be made if necessary to other CREV System dampers to prevent binding. The safety significance of this event was minimal. Given the impact on the CREV System, which is common to both Units, this report is submitted (for Units 1 and 2) in accordance with the requirements of 10 CFR 50.73 (a)(2)(v)(D), which requires the reporting of any event or 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. |
05000254/LER-2015-007 | Quad Cities | 27 May 2015 | Loss of Main Control Room Envelope Boundary Due to Damper Inspection | alarm. A fire damper inspection was being performed that opened a Control Room HVAC ductwork access hatch that caused the alarm. The hatch was opened and immediately shut, re-establishing the boundary of the Control Room Envelope (CRE). The Control Room Emergency Ventilation (CREV) system was declared inoperable due to opening the ventilation duct hatch without prior administrative controls in place. As a result, Technical Specification 3.7.4, Condition C, was entered and subsequently exited within approximately one minute. The cause of the inadvertent CRE breach was the design drawing contained in the work package that was reviewed during the Plant Barrier Impairment (PBI) screening did not adequately define the boundaries of the CRE. Corrective actions included reviewing all open PBI packages. Associated Control Room boundary drawings and procedures will be revised to correctly annotate the proper CRE boundary to include the MCR ventilation ductwork access hatch. The safety significance of this event was minimal. Given the impact on the MCR envelope, this report is submitted (for Units 1 and 2) in accordance with the requirements of 10 CFR 50.73 (a)(2)(v)(D), which requires the reporting of any event or 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. |
05000395/LER-2015-002 | Summer | 9 April 2015 | 1 OF 4 | A past operability review determined that HVAC System Mechanical Water Chiller (X11X0001A) had been non-functional during the month of July 2013 due to a vulnerability with component operation resulting in a low oil level condition. The event impacts the operability requirements of the Chilled Water (VU) System and the area room coolers the system supports per TS 3/4.7.9, "Area Temperature Monitoring. On September 25, 2013, XHX0001A tripped on low oil level following surveillance testing. The "Circuit 2 Low Oil Level" fault occurred due to the compressor oil level dropping below the low oil level indicator switch set point for 60 seconds which initiates shutdown of the component. The cause was low superheat, causing liquid floodback to the compressor and a low evaporator heat load that was insufficient to promote proper oil return in the evaporator. The chiller unit was intermittently operated as the only chiller on the "A" VU train in July 2013. Due to this vulnerable condition the non-functional chiller impacted the operability of the "A" train components served by the "A" train VU system. On April 9, 2015, the station determined this event was reportable and is being submitted in accordance with 10 CFR 50.73(a)(2)(i)(B). |
05000400/LER-2015-002 | Harris | 4 April 2015 | Breakers to the 'A' and 'B' Train Control Room Normal Intake Isolation Damper Motor Actuators Tripped Open | On April 4, 2015, Harris Nuclear Plant was shut down for a scheduled refueling outage in mode 5 and was performing the Remote Shutdown System Operability test. Following transfer back to the Main Control Board, the supply breakers to the normal air intake isolation dampers' motor actuators both independently tripped due to high instantaneous current from the attempted direction reversal of their respective motor actuators. These trips caused both dampers to be in the partially open position, rendering the Control Room Envelope (CRE) boundary inoperable. The apparent cause of this event is that the HMCP model breaker/starter combination installed by a Design Change is more sensitive to peak current spikes than the original EF3 model breakers. The contributing cause associated with this event was that industry operating experience (OE) was not adequately reviewed to identify existing OE on the need to raise the trip setting on HMCP model breakers. Immediate corrective action was taken to manually close the dampers and restore integrity of the CRE boundary. The corrective action taken to address the breaker sensitivity observed was that the trip settings for the impacted HMCP model breakers installed by the Design Change were revised to add margin to the trip settings. |
05000373/LER-2014-004 | Lasalle | 28 August 2014 | 1 OF 3 | On August 28, 2014, both Units 1 and 2 were in Mode 1 at 100% power. The 'B' train of Auxiliary Electric Equipment Room ventilation (VE) was inoperable due to a planned repair of an oil leak. The Main Control Room ventilation envelope consists of both the Main Control Room and the Auxiliary Electric Equipment Room. Both the Control Room HVAC (VC) and VE were required to be operable at the time of the occurrence. Technical Specification (TS) 3.7.5 Required Action (RA) A.1 had been entered to restore the control room area ventilation (VC) air conditioning subsystem to operable status within 30 days. At 1227 hours CDT, the Main Control Room received a start alarm on the Unit 1 plant process computer (PPC) for the 'A' train VE compressor. A check of the PPC computer point indicated that the 'A' train VE compressor was not running. The rounds operator responded and reported that the 'A' train VE compressor was cycling on and off. The 'A' train of VCNE was declared inoperable. With both trains of VCNE inoperable, the Station entered TS 3.7.5 RA B.1 to verify control room area temperature less than 90 degrees once per four hours, and RA B.2 to restore one control room area ventilation air conditioning subsystem to operable status within 72 hours. The cause of the event was a shorted wire on liquid line solenoid valve ORG053A that caused the solenoid valve to close, resulting in the compressor shutting down on low suction pressure. The corrective action was to repair the wiring problem and return the compressor to service. |
05000285/LER-2014-004 | Fort Calhoun | 24 April 2014 | Unqualified Limit Switches Render Safety Equipment Inoperable | On April 24, 2014, during a review of previous conditions affecting equipment qualification it was identified that the environmental qualification of Namco EA180 series limit switches were not being properly maintained per vendor requirements. This condition was not verbally reported at the time of discovery as the condition was identified and resolved while the plant was in an extended shutdown. A cause evaluation was completed and determined that technical requirements from the vendor manual for maintaining environmental qualification of the Namco EA180 series limit switches were not captured in the applicable plant procedure. The applicable plant procedure has been revised to include vendor information for maintaining environmental qualification of the limit switches. The limit switch top cover gasket and screw assemblies for all environmentally qualified Namco EA180 series limit switches were replaced and torqued in accordance with vendor requirements. |
05000387/LER-2014-003 | Susquehanna | 4 March 2014 | Loss of Secondary Containment during Technical Specification SR 3.6.4.1.5 Drawdown Testing | On March 4, 2014 at 0025 EST, during Technical Specification (TS) surveillance SR 3.6.4.1.5, drawdown testing of Secondary Containment failed to meet acceptance criteria of SR 3.6.4.1.5 due to maximum flow rate exceeding the allowable value. The testing was performed with the Unit 1 Railroad Bay aligned as Zone III to verify integrity while aligned in a previously untested alignment. The untested alignment was with the Unit 2 Reactor Building HVAC shutdown and a controlled Zone II Secondary Containment breech established. Actual in-leakage while in the untested alignment was 3301 cubic feet per minute (cfm), which is in excess of the TS SR 3.6.4.1.5 acceptance criteria of less than or equal to 2885 cfm. This event was determined to be reportable as an 8 hour ENS (# 49867) in accordance with 10 CFR 50.72(b)(3)(v)(c) for a loss of safety function. There is no redundant Susquehanna Secondary Containment system. This LER is being submitted in accordance with 10 CFR 50.73(a)(2)(v)(C), for an event or condition that at the time of discovery, could have prevented the fulfillment of the safety function of Secondary Containment to control the release of radioactive material. The direct cause of this event was due to air in-leakage into Secondary Containment past Door-101 and the Truck Bay Access Hatch Cover 2H24. The apparent cause was due to inadequate margin for the untested configuration with Unit 2 Reactor Building HVAC shutdown and a controlled Zone II Secondary Containment breach established. Completed Actions: 1) Secondary Containment ventilation was realigned to a known previously successfully tested alignment, 2) Installed shielding on the Core Spray piping adjacent to the Control Structure to gain margin in SSES's analysis for Control Room Operator dose post-accident, and 3) Revised the Unit 1 and Unit 2 Tech Spec Bases 3.6.4.1 to increase SGTS Exhaust Flow Rate. Planned Actions: 1) Repair/replace the bottom seal plate and the top and bottom seals on Door-101, 2) Caulk joints for 2H24 Hatch, and 3) Re-perform Secondary Containment drawdown tests per SE-170-011 for Zone I / Ill aligned in the untested configuration. There were no actual consequences to the health and safety of the public as a result of this event. |
05000298/LER-2014-001 | Cooper | 6 January 2014 | Secondary Containment Declared Inoperable due to Rise in Differential Pressure | On January 6, 2014, the differential pressure (DP) in the reactor building rose above the requirement of -0.25 inches of water column DP, causing entry into Limiting Condition of Operation (LCO) 3.6.4.1, Condition A. Secondary containment was declared inoperable at 02:45. The DP transient occurred when a non-licensed plant operator (NLO) was hanging tags in support of maintenance work. During the process of hanging tags, the NLO inadvertently opened the wrong drain valve. When the wrong drain valve was open, the reactor recirculation motor generator (RRMG) exhaust fan discharge damper that was operating closed. The NLO felt the change in DP and closed the drain valve, which opened the RRMG exhaust fan discharge damper, restoring ventilation. DP was restored, secondary containment was declared operable at 03:02, and the LCO was exited. During this event, DP remained negative at all times. The root cause is the organization was not fully aware of the effects of the cross-over leakage between the reactor building envelope and the RRMG exhaust system. To prevent recurrence of this event, procedures will be revised to ensure adequate precautions are taken to avoid exceeding the -0.25 inches of water column DP requirement, information about the effects of cross-over leakage will be incorporated into the appropriate training materials, and a procedure to directly measure air leakage will be developed. |
05000373/LER-2013-008 | Lasalle | 22 November 2013 | Control Room HVAC Inoperable Due to Failed Fan Motor | On November 22, 2013, both Units 1 and 2 were in Mode 1 at 100% power. The 'A' train of Main Control Room ventilation (VC) was inoperable due to an emergent repair of a Freon leak. Technical Specification (TS) 3.7.5 Required Action (RA) A.1 had been entered to restore the control room area ventilation AC subsystem to operable status within 30 days. At 1920 hours CST, the Main Control Room received an Auxiliary Electrical Equipment Room (AEER) HVAC (VE) Panel Trouble Alarm. The rounds operator responded to the panel and reported that the 'B' AEER Cooler Condenser Pan trip alarm was in, and the fan (OVE03CB) was not turning. An acrid smell was detected coming from the fan motor breaker compartment. The 'B' train of VC and VE was declared inoperable. With both trains of VC/VE inoperable, the Station entered TS 3.7.5 RA B.1 to verify control room area temperature less than 90 degrees, and RA B.2 to restore one control room area ventilation AC subsystem to operable status within 72 hours. The cause of the event was a winding failure of the 'B' Auxiliary Electric Equipment Room Cooler Condenser fan motor. Corrective actions included replacing the failed fan motor, and performing a failure analysis to determine the cause of the winding failure. |
05000498/LER-2013-003 | South Texas | 31 October 2013 | Unanalyzed Condition- Direct Current Ammeter Circuits Without Overcurrent Protection. | On October 31, 2013, at approximately 1834 Central Daylight Time during review of industry operating experience, South Texas Project (STP) determined an unanalyzed condition exists related to the Control Room (CR) fire analysis. The original design of ammeter circuits which provide CR current indication for the non-Class 48 VDC battery and battery charger circuits and for the non-Class turbine lube oil emergency pump control circuit does not include overcurrent protection features to limit fault current. In the postulated event, a fire in the CR could cause a ground loop through unprotected ammeter wiring or control circuit wiring and potentially result in excessive current flow and heating to the point of causing a secondary fire outside the CR in the cable raceways. The postulated secondary fire could affect the availability of equipment needed to place the plant in a safe shutdown condition during a CR fire event. This scenario has not been analyzed in accordance with 10 CFR 50 Appendix R. Compensatory fire watch measures have been implemented and remain in place for the affected fire zones in the plant. The cause was determined to be that the original design of the affected CR circuits did not adequately address fire protection program requirements. A design change is planned to correct the latent design deficiencies by providing circuit protection on affected CR circuits. |
05000282/LER-2013-001 | Prairie Island | 9 August 2013 | Control Room Envelope Inoperable | In December 2010, Control Room Envelope (CRE) testing was conducted to satisfy Surveillance Requirements (SR) 3.7.10.5. At that time, as a prerequisite, the surveillance procedure contained a step to add water to two floor drains loop seals located in the 121 and 122 Safeguards Chiller Room that penetrated the CRE. On August 9, 2013, this practice was determined to be unacceptable preconditioning. Because the December 2010, surveillance test was the first performance of this surveillance, the unacceptable preconditioning resulted in a never performed surveillance, failure to meet the associated surveillance requirement, and an inoperable CRE. On September 13, 2013, the CRE was tested and failed due to excessive in-leakage from Control Damper CD- 34177. This condition is reportable per 10 CFR 50.73(a)(2)(v)(C), event or condition that could have prevented fulfillment of a safety function and 10 CFR 50.73(a)(2)(i)(B), operation or condition prohibited by Technical Specification. Based on engineering's past operability evaluation with the equipment history of CD-34177, the CRE was inoperable from December 10, 2010. The Technical Specification Required Action Statement for 3.7.10 Condition B was exited on September 18, 2013. |
05000269/LER-2013-002 | Oconee | 26 June 2013 | LPI and RBS Trains Inoperable When 1LP-21 Was Closed Due To Human Error | |
05000382/LER-2013-005 | Waterford | 22 May 2013 | Emergency Diesel Generator Inoperable Due To Room Exhaust Fan Failure | Waterford 3 declared Emergency Diesel Generator B (EDG-B) inoperable on May 22, 2013 due to inability to maintain room temperature within design limits. Subsequent trouble shooting revealed that the variable pitch room exhaust fan had failed due to separation of the fan hub from the hub sleeve. Examination of recent operating data showed that the first evidence of fan failure had been during a surveillance test the previous month. An apparent cause evaluation determined the probable cause of the failure to be the result of repairs made during a previous (1999) fan motor replacement. These repairs caused additional stresses on the fan hub components which eventually resulted in fan hub separation from the hub sleeve. The EDG-B room exhaust fan was repaired and EDG-B operability was restored on May 26, 2013. Safety significance for the event is characterized as low to moderate. This condition is reportable under the following criteria: 10 CFR 50.73(a)(2)(i)(B), 10 CFR 50.73(a)(2)(ii)(B), and 10 CFR 50.73(a)(2)(v)(D). |
05000382/LER-2014-001 | Waterford | 8 May 2013 | Room Cooler Breaker Inoperability Causes Past Inoperability of Containment Spray System Train | On May 8, 2013 at 19:53, a safety-related circuit breaker failed when Operations personnel attempted to start Shutdown Cooling Heat Exchanger Room B air handling unit. In accordance with Operations administrative procedure for Technical Specification and Technical Requirements Compliance, Operations personnel entered the applicable Technical Specification Limiting Condition for Operation for Containment Spray (CS) train B. A replacement breaker was installed and a successful start of the air handling unit was performed. CS Train B was declared operable at 17:30 on May 9, 2013. An evaluation of the failure determined that the air handling unit had been effectively rendered inoperable since installation of the circuit breaker on April 18, 2013. Containment Spray train B was inoperable from 03:09 on April 17, 2013, when the train was declared inoperable to perform preventative maintenance until 17:30 on May 9, 2013, a total of 22.6 days. This time period exceeds the Technical Specification allowed outage time of 7 days. Technical Specification 3.6.2.1 was not complied with, which requires that with one CS system (train) inoperable, restore the system (train) to operable status within 7 days or be in at least Hot Standby within the next six hours. During this time frame CS 'A' was inoperable for 6.65 hours. Since both trains of Containment Spray were inoperable this is considered a Safety System functional failure due to the system being unable to mitigate the consequences of an accident. |
05000483/LER-2013-004 | Callaway | 18 April 2013 | Control Building Envelope (CBE) Boundary Door Open During Movement Of Irradiated Fuel Assemblies | On 04/1 8/2013, a small fire occurred at the Unit Auxiliary Transformer which caused a loss of all non-vital power to the plant during core offload. At this point in the core offload, a fuel assembly was suspended in the spent fuel pool due to a torn grid strap. The assembly was considered to be in movement since the assembly was not in a "safe" or approved storage location. As a result of the loss of power, it was desired to restore temporary power to the 'B' train battery chargers to prevent loss (discharge) of the NK02 and/or NK04 batteries. Temporary power cables were routed through three doors in the Control Building, one of which was a Control Building Envelope (CBE) pressure boundary door. With cables running through the CBE door, mitigating actions were taken to seal the opening. Such mitigating actions are allowed in Modes 1-4 per Technical Specification (TS) 3.7.10, when Condition B applies for an inoperable CBE boundary. However, allowances for mitigating actions are not permitted for an inoperable boundary during the movement of irradiated fuel assemblies. For this situation, TS 3.7.10 Condition E applies, and its Required Actions are to immediately suspend CORE ALTERATIONS (E.l) and movement of irradiated fuel assemblies (E.2). The Control Room did not immediately recognize that Required Action E.2 was in effect; therefore, there was a delay in beginning this Action of approximately 2 hours and 24 minutes. Required Action E.2 was not met since the Action was not taken without delay. NRC FORM 356 (10.20'0) |
05000528/LER-2013-002 | Palo Verde | 8 April 2013 | Inoperable Systems Due to Defective Relays Reported under Part 21 | This LER reports the failure of components caused by a defect in ARD66OUR control relays reported by Westinghouse, pursuant to 10 CFR 21, on April 8, 2013. The defect resulted in the failure of five normally energized control relays at PVNGS in two different systems in Unit 1 and two different systems in Unit 2. The relays were used in normally energized applications which are de-energized to position associated components to support the related safety function. The relays failed to change state when de-energized during testing. The five failed relays were replaced. The cause was a change in the manufacturing process that occurred in May 2008. The defect was exhibited only on relays that failed in the manner described in the Westinghouse Part 21 report. An extensive testing program was completed to identify and replace ARD66OUR relays installed at PVNGS that exhibited the described failure mode. Westinghouse has modified the ARD66OUR relay plastic molding process to preclude this described failure mode. LER 05000529 / 2009-002-00 reported ARD66OUR relay failures that exhibited a similar failure mode. |
05000397/LER-2013-002 | Docket Number | 2 March 2013 | -spaced typewritten lines) In October 2012, it was determined that the Technical Specification (TS) surveillance procedure to verify that each control room air conditioning (AC) subsystem has the capability to remove the assumed heat load for TS Surveillance Requirement (SR) 3.7.4.1 did not satisfy the surveillance requirement. The methodology for the existing surveillance had been in use since 1998 around the time Energy Northwest converted to the Improved Technical Specifications. TS SR 3.0.3 was invoked and a new surveillance procedure was developed. On March 2, 2013, while performing the new surveillance procedure, the test results revealed that the air handler thermal performance for the "A" train did not meet the acceptance criteria. This failure to satisfy SR 3.7.4.1 in March, following entry Into SR 3.0.3, is reportable under 10 CFR 50.73(a)(2)(i)(B) - Any operation or condition which was prohibited by the plant's technical specifications. The control room AC subsystem has been cleaned, retested, and returned to operable status.
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05000269/LER-2013-001 | Oconee | 6 February 2013 | Inadequate HVAC Load Analysis and Design Impacts on Emergency Power Equipment | On 2/6/2013, with all three Oconee Units at 100 percent power, Oconee Nuclear Station (ONS) personnel concluded that emergency power equipment could be adversely impacted by a licensee identified original design issue involving inadequate analysis of electrical equipment heat loads and weaknesses in the Heating Ventilation & Air Conditioning (HVAC) system design. The investigation determined that the principle causes were associated with inadequate and incomplete inputs and methods in development of HVAC systems during original plant design and Blockhouse, and the 230kV Switchyard Relay House susceptible to single failures. Compensatory measures were put into place. Corrective actions include modifications to resolve the inadequacies with the original plant design issues. This event is reportable under the following criteria: Operations Prohibited by Technical Specifications, Unanalyzed Condition, Event that could have prevented Fulfillment of a Safety Function, and Common Cause. |
05000354/LER-2013-010 | Hope Creek | 20 January 2013 | Loss of Both Control Room Chillers | On 12/20/13 at 1303, while the B Control Room Chiller was out of service in support of maintenance, the A Control Room Chiller was manually secured due to excessive fluctuations in load. The Technical Specification action statement (TS 3.7.2.2 Action a.2) for both Control Room Air Conditioning subsystems inoperable was entered. Concurrent inoperability of both control room chillers is reportable per 50.73 (a)(2)(v)(D), an event or 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 . At 2120 on 12/20/13 the B Control Area Ventilation Train and Chiller were placed in service for post maintenance testing, returned to an operable status , and the action statement was exited. Throughout the time both chillers were inoperable, the control room temperature was maintained below the TS limit of 90 degrees F. The A Control Room Chiller excessive load fluctuations were determined to be the result of an inoperable chiller condenser pressure control valve. The valve inoperability was due to an age-related positioner component failure caused by a legacy issue with implementation of a design change. The failed positioner was replaced and the A Control Area Ventilation Train and Chiller were returned to operable status. |
05000483/LER-2013-001 | Callaway | 17 December 2012 | Violation of Technical Specification 3.0.3 Due To A Class lE Electrical Equipment NC Unit Inoperability | On 14:35 on 12/17/2012, the A Class lE electrical equipment air conditioning unit (SGKO5A) was declared inoperable due to identification of Freon leakage from the unit's low oil pressure and compressor discharge sensing lines. Following repair to address the leakage, the unit was declared operable at 11:08 on 12/18/2012. The SGKO5A unit provides a support function for the A train of Class lE electrical equipment. The Class lE electrical equipment is addressed in the plant's Technical Specifications. Since the leakage for SGKO5A had apparently existed prior to the time of discovery, it was concluded that SGKO5A and the supported Class 1E electrical equipment had been inoperable for a period of time longer than the allowed by the plant Technical Specifications. The leakage was the result of two sensing lines rubbing together. The Root Cause was determined to be an inadequate scope of previously conducted equipment reliability evaluations on the HVAC system. The leaks were repaired. In addition, preventive maintenance and monitoring of vibration-susceptible Class lE electrical equipment air-conditioners will be increased. |
05000528/LER-2012-004 | 29 August 2012 | Essential Spray Pond Pump Actuation Due to a Control Room Essential Filtration Actuation Signal | On August 29, 2012, the Unit 1 control room received a fuel building ventilation exhaust radiation monitor 1JSOBRU0145 (RU-145) high radioactivity alarm. This resulted in actuation of the train A and B fuel building essential ventilation actuation signals (FBEVAS) and control room essential filtration actuation signals (CREFAS). The CREFAS started the train A and B control room essential air filtration units, essential chilled water systems, essential cooling water systems and essential spray pond systems. Alternate sampling and radiation monitor comparisons determined the RU-145 high radioactivity alarm to be invalid. An investigation determined the RU-145 high radioactivity alarm was caused by failure of a power supply zener diode and resultant loss of the 24 VDC low voltage power supply. Loss of the 24 VDC supply activated the check source feature which raised the radiation monitor output to above the high alarm set-point value. The faulty power supply was replaced. No additional actions were determined to be necessary because existing preventive maintenance requirements replace the power supply board every 7.5 years and zener diodes are reliable in voltage regulation applications for the radiation monitoring system at PVNGS. This was the first failure of this type at PVNGS with greater than 25 years of operation. In the past three years, PVNGS has not reported a similar event to the NRC. | |
05000397/LER-2012-003 | Docket Number07 24 2012 2012 -003 -00 09 20 2012 05000 | 24 July 2012 | Secondary Containment Pressure Exceeded During Plant Maintenance | On July 24, 2012, secondary containment pressure exceeded technical specification allowable limits for a period of approximately four and a half minutes. The pressure excursion was due to an inadvertent trip of reactor building fans ROA-FN-1B and REA-FN-1B. The trip occurred during ongoing maintenance on the Standby Gas Treatment (SGT) system. While technical specification limits were exceeded, the resulting pressure excursion was bounded by analytical results, and thus there were no safety consequences for this event. The investigation concluded that there was no direct evidence that a human performance error caused this event. The cause for the event was determined to be that operations does not have guidance on swapping to redundant lineups when work is to be performed on the SGT or reactor building HVAC . Corrective actions will revise standard operating procedures and Instrument Master Data Sheets by adding a note about reactor building fan trip risk. 26158 R5
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05000388/LER-2012-001 | Docket Number | 11 May 2012 | Two Control Room Floor Cooling Systems Inoperable | On 5/11/12 at 1603 hours, while operating at 100% power, Unit 2 entered LCO 3.0.3 due to two control room floor cooling systems being inoperable. OV117A Control Room Floor Cooling Unit fan's discharge damper failed earlier during the same day at 0523 hours, rendering the associated OV117A fan inoperable. The redundant 'B' train fans and associated Control Structure Chiller automatically started as a result of a fan low flow interlock. The control switch for the 'A' train logic was left in 'Starr and the control switch for the 'B' train logic was left in 'Auto' as directed by the alarm response procedure. During application of a clearance order for repair of the failed OV117A fan damper, the 'A' control room cooling fan switch was placed in 'Stop' position. This resulted in an automatic start of the 'A' Control Structure Chiller and all the associated 'A' fans except for the control room cooling fan, and a shutdown of the 'B' train fans and chiller. This condition caused the loss of both control room cooling fans and LCO 3.7.3, "Control Room Emergency Outside Air Supply (CREOAS) System," Condition E; LCO 3.7.4, "Control Room Floor Cooling System," Condition D; LCO 3.0.3; TRO 3.7.9, "Control Structure HVAC," and TRO 3.8.6, "Emergency Switchgear Room Cooling," were entered at 1603 hours. The control room operators immediately recognized the loss of cooling and took manual action to restart the 'B' train. LCO 3.0.3 was exited at 1618 hours without a reactor power reduction. This event is reportable as a loss of entire safety function under 10CFR50.73(a)(2)(v)(D). The causes of the event included a control switch design deficiency and less than adequate clearance order preparation, review and application authorization. Immediate corrective actions were taken to modify alarm response procedures. Key corrective actions that are planned include replacing control switches to correct the design deficiency and revising the Susquehanna clearance order procedure to provide better guidance for developing clearance orders for equipment that is in an atypical configuration due to system transient. Susquehanna Unit 1 was in Mode 5 at the time of the event and therefore was unaffected because the associated Unit 1 Technical Specifications were not applicable. There were no adverse consequences to the health and safety of the public as a result of this event. |
05000445/LER-2012-001 | 1 March 2012 | UNANALYZED CONDITION DISCOVERED FOR THE NORMALLY OPEN BATTERY ROOM FIRE AND CABLE SPREAD ROOM DOORS CLOSE ON MOMENTARY LOSS OF POWER | On 3/1/2012, at 1353 hours, an issue was identified with the doors for the safety related battery rooms and their normal pOsition. Several doors to the battery rooms are held open via electromagnetic door devices. At the time, it was thought that there was no uninterruptible power to the door mechanisms, and that all the doors are expected to close in the event of a loss of offsite power (LOOP). Inadvertent closure of the doors following a momentary loss of power prevents their design function of venting hydrogen from the battery rooms and providing tornado venting pathways in the building. Compensatory measures were taken to secure the doors open to maintain the hydrogen purging and tornado venting functions. A roving fire watch was implemented to comply with the fire protection function of the doors. As an extent of condition on 3/12/12, the cable spread room (CSR) doors were also identified to utilize the same design and electrical supply configuration as the battery room doors. The CSR is located above the battery rooms in the Electric and Control (E&C) Building. Contingency actions were put in place to secure the CSR doors open and implement a fire impairment in the event of a tornado risk. On 4/11/12, it was discovered that the battery room and CSR doors have small battery backup units which could sustain the doors with adequate power to maintain their position for 45 seconds sufficient to allow AC power to be restored through the Emergency Diesel Generators (EDG5) during a tornado. However, the backup units were found to be in a state of degradation, challenging the ability of the backup batteries to maintain their power supply to the door hold-open devices during a tornado event. No recent preventive maintenance work orders exist for the inspection or replacement of these units. There were no actual safety consequences impacting the plant or public safety as a result of these events. The cause was a design process legacy issue, and current design processes are significantly different from those in place during early operation of CPNPP. The specific conditions have been addressed in the corrective action program and, along with current programs and practices, are adequate to prevent future occurrences. All times in this report are approximate and Central Time unless noted otherwise. |