|Report date||Site||Event description|
|05000413/LER-2016-001||23 June 2016||Catawba|
On March 28, 2016, Operators did not receive the expected results from a relay while performing the 1B train Emergency Core Cooling System (ECCS) Cold Leg Recirculation interlock test. Investigation found the breaker for the residual heat removal pump's loop suction valve incorrectly positioned open. ECCS 1B was declared inoperable. Subsequently, the breaker was closed after it was verified not to have been tripped open.
The last manipulation of this breaker was determined to have been during the coordination for pressure boundary valve testing and standby readiness alignment during the previous refueling cycle (December 2015). A past Operability Evaluation concluded the breaker being open led to a condition prohibited by Technical Specifications, and also a condition that could have prevented the fulfillment of a safety function for Unit 1 ECCS while the 1A emergency diesel generator was inoperable for greater than four hours during this time period. This event was determined to be reportable on April 26, 2016.
The cause of this event is that the test procedure for pressure boundary valve testing did not contain specific procedural guidance for establishing a suction source for the 1B train residual heat removal (RHR) pump. The test procedure required coordination with another procedure to ensure the breaker for the 1B train RHR pump loop suction valve was returned to the closed position. Corrective actions include procedural revisions to these procedures.
|05000413/LER-2014-001||6 May 2014||Catawba|
On March 7, 2014 at 0929 hours, TS 3.8.1, "AC Sources - Operating" was violated as a result of maintenance activities on DG 1A to replace a connecting rod bearing that was found to have rotated from its normal horizontal position. Catawba had previously requested a NOED on March 6, 2014 in anticipation of exceeding the applicable TS 3.8.1 Required Action Completion Time. The NOED was subsequently granted by the NRC on that same day. This event is therefore reportable under 10 CFR 50.73(a)(2)(i)(B) as an operation or condition which was prohibited by the plant's TS. The affected bearing was proactively replaced, leading to the need for the NOED. The most probable cause of the rotation of the affected bearing is inadequate procedural control of lubricating oil temperature prior to starting an engine following extended periods of maintenance. Corrective actions taken in response to this event include revisions to plant procedures governing DG maintenance and operation. It was subsequently determined that the affected DG 1A bearing would have been able to perform its specified safety function in the as-found condition. During the period that DG 1A was inoperable while the affected bearing was being replaced, DG 1B was operable.
Therefore, this event had no adverse effect upon the health and safety of the public.
|05000413/LER-2013-002||10 February 2014||Catawba||On December 16, 2013, following the completion of an engineering evaluation, it was determined that main feedwater isolation valves (MFIVs) 1CF42 and 1CF60 had been unknowingly inoperable since the completion of the last Unit 1 refueling outage in December of 2012. The MFIVs have the possibility of becoming thermally bound or pressure locked following heat up of the feedwater system. To aid in opening the valves, they are procedurally "soft seated" by reducing the nitrogen pressure in the system. After the MFIV is opened, the nitrogen system is restored to its normal pressure. Following maintenance work to "soft seat" MFIVs 1CF33, 1CF42, 1CF51 and 1CF60 near the end of refueling outage 1E0C20, the nitrogen supply to 1CF33, 1CF42 and 1CF60 remained partially isolated. This condition went undetected until subsequent maintenance activities in November 2013 identified the issue. A review for the periods of time that the partial isolation existed identified that 1CF33 remained operable; however, during the time period of 7/13/13 - 11/8/13, 1CF-42 nitrogen accumulator pressure was below the operability limit for operation with the remote accumulator isolated and from 1/19/13 - 10/25/13, 1CF-60 nitrogen accumulator pressure was below the same limit. The cause is attributed to human errors related to inadequate job preparation and procedure use and adherence. The pre job brief was deficient and steps were inappropriately marked "not applicable" in the procedure. Planned corrective actions include updating model work orders used to plan this work to include a requirement to review corrective action program documents related to this event prior to performing this work and including this issue in the 2014 training covering operating experience for the Maintenance organization. There was minimal safety significance to this event. The closed system provided an inside containment isolation and the ability to perform at least one method of main feedwater isolation was maintained, therefore, this event did not affect the health and safety of the public.|
|05000413/LER-2013-001||10 October 2013||Catawba||On August 13, 2013, following the completion of an Engineering evaluation, it was determined that each DG had been unknowingly inoperable during its monthly surveillance test. Prior to this determination, Catawba had always considered the DG to remain operable during its monthly surveillance test. It was determined that under certain loading conditions, SR 184.108.40.206 could not be met while the DG was being tested. SR 220.127.116.11 verifies that with the DG operating in the test mode and connected to its bus, an actual or simulated Engineered Safety Features (ESF) actuation signal overrides the test mode by returning the DG to standby operation and automatically energizing the emergency load from offsite power. The DG control circuit is to return voltage and frequency to their pre-position settings if a load sequencer actuation occurs while the DG is operating paralleled to offsite power. However, it was determined that the control circuit will not return to its pre-position frequency setting if the DG is operating at greater than a threshold load value (the threshold load value varies with each DG). Operating outside of the TS required frequency range renders the DG inoperable. With the DG unknowingly inoperable, SR 18.104.22.168 was not performed within one hour as required. There was one instance where a DG was unknowingly inoperable during testing and the opposite train DG was simultaneously inoperable. The cause of this issue is an inadequate design of the DG pre-position control circuit attributed to a legacy design error that was transported from the original manufacturer to Catawba. Following the discovery of this issue, affected DG test procedures were revised to require declaring the DG inoperable during its monthly surveillance test. The Unit 1 DG control circuit will be revised (Unit 2 is complete) such that when the DG is operating paralleled to offsite power at full load, the pre-position circuit will energize to reset voltage and frequency to their required settings following an actuation of the DG load sequencer. There was minimal safety significance to this event. The DGs were operable except for those time periods when they were being tested while operating paralleled to offsite power at greater than the threshold load value. Therefore, this event did not affect the health and safety of the public.|
|05000413/LER-2011-003||14 February 2012||Catawba|
On December 15, 2011 at 1421 hours and 1422 hours, respectively, Unit 1 and Unit 2 entered Mode 3 to complete a Technical Specification (TS) Limiting Condition for Operation (LCO) 3.0.3 required shutdown due to both trains of the Control Room Area Chilled Water System (CRACWS) being inoperable. The primary cause of this event was failure of a microprocessor for the Train "B" CRACWS Chiller. Further testing is being conducted to determine the cause and support implementation of changes to improve the reliability of the microprocessor.
Two additional causes identified include the 1) lack of procedures to replace the Train "B" microprocessor component within the allowable LCO 3.0.3 completion time and 2) insufficient maintenance procedural guidance for alignment of the chilled water pump. Corrective actions include developing a procedure to replace the microprocessor, and revising the procedure to provide additional detail for pump alignment.
Throughout this event, all other plant safety related systems were capable of performing their required safety related functions.
|05000413/LER-2011-002||22 June 2011||Catawba|
On April 23, 2011 at 0921 hours, the Auxiliary Feedwater (CA) System was automatically actuated. This resulted from Main Feedwater (CF) being inappropriately isolated with the Unit in Mode 4 during the shutdown for a refueling outage. The Loss of Steam Generator (SG) Feedwater procedure was entered, and through the addition of CA, SG level was stabilized to normal levels. At 1026 hours CF was restored to service.
This event was caused by the placement of a tagout prior to its scheduled execution time without fully recognizing its effect on plant operation. The tagout closed two CF valves which isolated all CF flow to the SGs. A root cause evaluation was performed and two root causes were determined to have resulted in this event. These root causes and the resultant corrective actions are described fully in the body of this LER.
Throughout this event, the 1A Motor Driven Pump Train of the CA System was operable and performed its required safety related function. The CF system was subsequently restored, CA was secured, and the Unit was cooled down to Mode 5 where the CA System was no longer required. Therefore, the health and safety of the public were not adversely affected by this event.
|05000413/LER-2004-004||2 February 2005||Catawba|
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|05000413/LER-2003-001||24 March 2003||Catawba|
-On February 4, 2003, at 1005 hours, Catawba Unit 1 tripped from 100% power. A Main Feedwater (MFW) System header pressure transmitter was being returned to service following replacement. As the transmitter was valved in, its hydraulic interaction with the other two nearby transmitters caused MFW header pressure indication to the MFW control system to fluctuate. In response to the transient, the MFW control system switched from automatic to manual control, as designed, at a pre- determined pressure difference between the transmitters. As control room operators attempted to control steam generator levels manually, a high- high level on steam generator B resulted in a turbine trip, which resulted in a reactor trip. The high-high level also resulted in a trip of the MFW pumps, which caused an automatic start of the motor driven Auxiliary Feedwater (AFW) System pumps. This event was caused by an inadequate understanding of the MFW control system response to a common impulse line hydraulic interaction. Corrective actions planned in response to this event include training appropriate plant personnel concerning MFW control system design and response and revising procedures associated with the calibration and maintenance of selected transmitters.
|05000413/LER-2002-004||25 July 2002||Catawba||During review of a plant modification it was noted that 600 volt motor control centers (MCCs) lEMXG and 2EMXH may not have been adequately protected from potential moderate energy spray interactions in the chilled water (YC) chiller rooms. A section of fire protection system piping and demineralized water (YM) piping in both A and B train chiller rooms were identified as potential sources for moderate energy spray onto the MCC. Engineering evaluated this condition and determined that MCCs lEMXG and 2EMXH had not been adequately protected from the effects of a moderate energy pipe break associated with the YM or fire protection systems inside the Train A and B YC chiller rooms as required by the UFSAR. Temporary spray deflectors were installed to correct the issue. Follow up reviews by engineering determined that 4160 volt bus 2ETA was determined to be a water spray target from fire protection piping to the hose rack cabinet in the area. Operations was notified and declared 2ETA inoperable and applied Technical Specification 3.8.9. A spray deflector was installed and 2ETA was declared operable. This event did not affect the health and safety of the public.|
|05000413/LER-2002-005||25 July 2002||Catawba|
On June 25, 2002, with both Catawba Units operating in Mode 1 at 100% power it was determined that an Americium (Am-241) alpha source was missing. It was determined that the loss occurred on April 18, 2002 during a walkthrough associated with development of a procedure for calibration of a PCM-2 whole body monitor. An investigation determined that the cause of this event was an inadequate program for handling this sealed alpha source.
Corrective actions include training for radiation protection personnel on precautions for handling sealed sources and fabrication of an alpha source holder for use in PCM-2 calibrations.
This event had no effect on the safe operation of the plant. This source would present no danger to the health and safety of the public unless it were inhaled or ingested. Inhalation or ingestion of the source is considered unlikely due to the probable disposition and physical characteristics of the source.
|05000413/LER-2002-001||30 May 2002||Catawba|
From February 24, 2002 at 1735 hours until February 27, 2002 at 2255 hours, both trains of the Control Room Area Chilled Water System (CRACWS) were inoperable simultaneously, resulting in Units 1 and 2 being unknowingly in Technical Specification (TS) 3.0.3. At the time, CRACWS Train B was out of service for preventive maintenance. It was retroactively determined that during the early morning hours of February 21, 2002, the CRACWS Train A chiller had become inoperable due to relay leads that had loosened over time and had made intermittent contact. The leads eventually disconnected. The problem with the leads was not identified prior to taking CRACWS Train B out of service as a result of inadequate troubleshooting follow-up. This event resulted in a violation of TS 3.0.3, as well as a violation of TS 3.7.11 for the CRACWS.
Corrective actions taken in response to this event include communicating the troubleshooting aspects of this event to appropriate station personnel so that suspected problem causes are validated prior to considering equipment operable.
|05000413/LER-2001-003||10 December 2001||Catawba||On October 11,2001, Engineering review of recent past performance tests for the control room area ventilation system (CRAVS) determined that on at least two separate occasions A train of CRAVS did not meet the Technical Specification (TS) requirement for system flow. T The tests were conducted on 2/25/00 and 4/13/00. T This is not in compliance with TS requirements and resulted in A train of CRAVS being inoperable longer than allowed by TS. T During the time frame that A train of CRAVS was not in compliance with TS, B train of CRAVS was taken out of service on 33 separate occasions. T This resulted in both trains of CRAVS being inoperable at the same time which is also not in compliance with TS. T The most probable cause was that during the startup testing of the system the results from the air flow monitor devices (AFMDs) for both trains were not validated to ensure the accuracy of the installed flow instrumentation. T Pitot traverse ports were installed in the CRAVS to ensure accurate airflow readings and the CRAVS was tested, balanced and declared operable. T The airflow values reviewed did not adversely affect the dose analysis for the control room, T the CRAVS filter efficiencies, or the ability to pressurize the control room.|