IR 05000390/2015003
| ML15310A360 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 11/06/2015 |
| From: | Alan Blamey Reactor Projects Region 2 Branch 6 |
| To: | James Shea Tennessee Valley Authority |
| References | |
| IR 2015003 | |
| Download: ML15310A360 (23) | |
Text
UNITED STATES ember 6, 2015
SUBJECT:
WATTS BAR NUCLEAR PLANT - NRC INTEGRATED INSPECTION REPORT 05000390/2015003
Dear Mr. Shea:
On September 30, 2015, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at your Watts Bar Nuclear Plant, Unit 1. On October 16, 2015, the NRC inspectors discussed the results of this inspection with Mr. Walsh and other members of the Watts Bar staff. Inspectors documented the results of this inspection in the enclosed inspection report.
The NRC inspectors did not identify any findings or violations of more than minor significance.
In accordance with Title 10 of the Code of Federal Regulations (CFR) 2.390, Public Inspections, Exemptions, Requests for Withholding, of the NRC's "Rules of Practice," a copy of this letter, its enclosure, and your response (if any) will be available electronically for public inspection in the NRC Public Document Room or from the Publicly Available Records System (PARS) component of NRC's Agencywide Documents Access and Management System (ADAMS). ADAMS is accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).
Sincerely,
/RA/
Alan Blamey, Chief Reactor Projects Branch 6 Division of Reactor Projects Docket No.: 50-390 License No.: NPF-90
Enclosure:
NRC Integrated Inspection Report 05000390/2015003 w/Attachment: Supplemental Information
REGION II==
Docket No.: 50-390 License No.: NPF-90 Report No.: 05000390/2015003 Licensee: Tennessee Valley Authority (TVA)
Facility: Watts Bar Nuclear Plant, Unit 1 Location: Spring City, TN 37381 Dates: July 1 through September 30, 2015 Inspectors: J. Nadel, Senior Resident Inspector J. Hamman, Resident Inspector C. Kontz, Senior Project Engineer Approved by: Alan Blamey, Chief Reactor Projects Branch 6 Division of Reactor Projects Enclosure
SUMMARY
IR 05000390/2015-003; July 1, 2015 - September 30, 2015; Watts Bar, Unit 1
The report covered a three-month period of inspection by the resident inspectors. No findings were identified during the inspection period. The NRCs program for overseeing the safe operation of commercial nuclear power reactors is described in NUREG-1649, Reactor Oversight Process Revision 5.
REPORT DETAILS
Summary of Plant Status
The unit started the reporting period at 100 percent rated thermal power and remained there until September 3, 2015, when coastdown for refueling outage 13 began. The unit shut down for the outage on September 20, 2015, and remained shut down through the end of the reporting period.
REACTOR SAFETY
Cornerstones: Initiating Events, Mitigating Systems, and Barrier Integrity
1R01 Adverse Weather Protection
External Flood Protection Inspection
a. Inspection Scope
The inspectors reviewed the licensees readiness to cope with external flooding.
External flooding from a probable maximum precipitation or design basis flood had the potential for internal flooding of a portion of a number of the plant structures. The inspectors reviewed the feasibility of the licensees flooding mitigation plans and design features and verified that they were consistent with the licensees design requirements and the risk analysis assumptions for coping with this type of event. Credit was taken for this sample as part of the onsite inspections for Temporary Instruction (TI) 2515/190, Inspection of Licensee's Proposed Interim Actions as a Result of the Near-Term Task Force Recommendation 2.1 Flooding Evaluation. The inspectors performed walkdowns of selected areas to observe external flooding mitigation features and strategies at the intake pumping station and diesel generator building. Additionally, the inspectors reviewed the licensees corrective action program (CAP) to ensure any nonconforming conditions related to potential flooding were properly addressed. Documents reviewed are listed in the Attachment. This activity constituted one Adverse Weather Protection inspection sample, as defined in Inspection Procedure (IP) 71111.01.
b. Findings
No findings were identified.
1R04 Equipment Alignment
.1 Partial System Walkdowns
a. Inspection Scope
The inspectors conducted the equipment alignment partial walkdowns, listed below, to evaluate the operability of selected redundant trains or backup systems with the other train or system inoperable or out of service (OOS). This also included that redundant trains were returned to service properly. The inspectors reviewed the functional system descriptions, the Updated Final Safety Analysis Report (UFSAR), system operating procedures, and Technical Specifications (TS) to determine correct system lineups for the current plant conditions. The inspectors performed walkdowns of the systems to verify that critical components were properly aligned and to identify any discrepancies which could affect operability of the redundant train or backup system. Documents reviewed are listed in the Attachment. This activity constituted three inspection samples, as defined in IP 71111.04.
- Essential raw cooling water (ERCW) Pump E-B and H-B while ERCW Pumps F-B and G-B were OOS for a design change implementation
- Trains A and B spent fuel cooling including A train ERCW and A Train component cooling system (CCS) while protected for spent fuel cooling
b. Findings
No findings were identified.
.2 Complete Walkdown
a. Inspection Scope
The inspectors completed a detailed walkdown/review of the auxiliary feedwater system.
The inspectors reviewed relevant portions of the UFSAR and Technical Specifications.
This detailed walkdown also verified outstanding maintenance work requests on the system and any deficiencies that could affect the ability of the system to perform its function. The condition of applicable system instrumentation and controls, pipe hangers and support installation, and associated support systems status were observed. The inspectors examined applicable System Health Reports, open Work Orders (WOs), and any previous CRs that could affect system alignment and operability. Inspectors verified that outstanding design issues, temporary modifications, operator workarounds, and items tracked by the engineering department were being managed properly. Documents reviewed are listed in the Attachment. This activity constituted one Equipment Alignment Complete Walkdown inspection sample, as defined in IP 71111.04.
b. Findings
No findings were identified.
1R05 Fire Protection
.1 Fire Protection Tours
a. Inspection Scope
The inspectors conducted tours of the areas important to reactor safety, listed below, to verify the licensees implementation of fire protection requirements as described in: the Fire Protection Program, Nuclear Power Group Standard Programs and Processes (NPG-SPP)-18.4.6, Control of Fire Protection Impairments; NPG-SPP-18.4.7, Control of Transient Combustibles; and NPG-SPP-18.4.8, Control of Ignition Sources (Hot Work).
The inspectors evaluated, as appropriate, conditions related to: 1) licensee control of transient combustibles and ignition sources; 2) the material condition, operational status, and operational lineup of fire protection systems, equipment, and features; and 3) the fire barriers used to prevent fire damage or fire propagation. Documents reviewed are listed in the Attachment. This activity constituted six inspection samples, as defined in IP 71111.05AQ.
- Auxiliary building elevation 713
- Control building elevation 708
- Unit 1 lower containment
- Turbine building elevation 755
- Auxiliary building elevation 692
- Auxiliary building elevation 757 refuel floor
b. Findings
No findings were identified.
.2 Annual Drill Observations
a. Inspection Scope
On September 15, 2015, the inspectors observed a fire drill for a fire in the 1B-B diesel generator room. The drill was observed to evaluate the readiness of the site fire brigade to fight fires. The inspectors verified that the licensee staff identified deficiencies; openly discussed them in a self-critical manner at the drill debrief, and took appropriate corrective actions. Specific attributes evaluated were: 1) specified number of individuals responding; 2) proper wearing of turnout gear; 3) self-contained breathing apparatus available and properly worn and used; 4) control room personnel followed procedures for initiation and verification of response; 5) fire brigade leader exhibited command and had a copy of the pre-fire plan; 6) fire brigade leader maintained control starting at the dress-out area; 7) fire brigade response was timely and followed the appropriate access route; 8) command/control set up near the location and communications were established; 9)proper use and layout of fire hoses; 10) fire area entered in a controlled manner; 11)sufficient firefighting equipment brought to the scene; 12) search for victims and propagation of the fire into other plant areas; 13) utilization of pre-planned strategies; 14)adherence to the pre-planned drill scenario and drill objectives acceptance criteria were met; and 15) firefighting equipment returned to a condition of readiness to respond to an actual fire. Documents reviewed are listed in the attachment. This activity constituted one fire protection annual drill inspection sample, as defined in IP 71111.05AQ.
1R11 Licensed Operator Requalification and Performance
.1 Licensed Operator Requalification Review
a. Inspection Scope
On August 13, 2015, the inspectors observed the simulator scenario 3-OT-SRE-CYCLE 1504, MFRV fails in AUTO, dropped rod, failure of turbine trip, Loss of Coolant Accident (LOCA), Site Area Emergency, CCS-A-HX-leak. Performance indicator credit was taken.
The inspectors specifically evaluated the following attributes related to the operating crews performance:
- Clarity and formality of communication
- Ability to take timely action to safely control the unit
- Prioritization, interpretation, and verification of alarms
- Correct use and implementation of abnormal operating instructions and emergency operating instructions
- Timely and appropriate Emergency Action Level (EAL) declarations per emergency plan implementing procedures
- Control board operation and manipulation, including high-risk operator actions
- Command and Control provided by the unit supervisor and shift manager The inspectors also attended the critique to assess the effectiveness of the licensee evaluators, and to verify that licensee-identified issues were comparable to issues identified by the inspector. Documents reviewed are listed in the Attachment. This activity constituted one Observation of Requalification Activity inspection sample, as defined in IP 71111.11.
b. Findings
No findings were identified
.2 Observation of Operator Performance
a. Inspection Scope
Inspectors observed and assessed licensed operator performance in the plant and the MCR, particularly during periods of heightened activity or risk and where the activities could affect plant safety. Inspectors reviewed various licensee policies and procedures such as procedures OPDP-1, Conduct of Operations; NPG-SPP-10.0, Plant Operations; and GO-4, Normal Power Operation.
Inspectors utilized activities such as post maintenance testing, surveillance testing and refueling, and other outage activities to focus on the following conduct of operations as appropriate. Documents reviewed are listed in the Attachment. This activity constituted one Observation of Operator Performance inspection sample, as defined in IP 71111.11.
- Operator compliance and use of procedures
- Control board manipulations
- Communication between crew members
- Use and interpretation of plant instruments, indications and alarms
- Use of human error prevention techniques
- Documentation of activities, including initials and sign-offs in procedures
- Supervision of activities, including risk and reactivity management
- Pre-job briefs
b. Findings
No findings were identified
1R12 Maintenance Effectiveness
a. Inspection Scope
The inspectors reviewed the performance-based problem listed below. A review was performed to assess the effectiveness of maintenance efforts that apply to scoped structures, systems, or components (SSCs) and to verify that the licensee was following the requirements of TI-119, Maintenance Rule Performance Indicator Monitoring, Trending, and Reporting 10 CFR 50.65, and NPG-SPP-03.4, Maintenance Rule Performance Indicator Monitoring, Trending, and Reporting 10 CFR 50.65. Reviews focused, as appropriate, on: 1) appropriate work practices; 2) identification and resolution of common cause failures; 3) scoping in accordance with 10 CFR 50.65; 4) characterizing reliability issues for performance monitoring; 5) tracking unavailability for performance monitoring; 6) balancing reliability and unavailability; 7) trending key parameters for condition monitoring; 8) system classification and reclassification in accordance with 10 CFR 50.65(a)(1) or (a)(2); 9) appropriateness of performance criteria in accordance with 10 CFR 50.65(a)(2); and 10) appropriateness and adequacy of 10 CFR 50.65 (a)(1) goals, monitoring and corrective actions. Additional documents reviewed are listed in the attachment. This activity constituted two Maintenance Effectiveness inspection samples, as defined in IP 71111.12.
- Condition Report (CR) 991105, A MCR chiller inoperable due to low condenser pressure in standby
- CR 1063890, Rainwater leaking into relay room from crack in ceiling
b. Findings
No findings were identified.
1R13 Maintenance Risk Assessments and Emergent Work Control
a. Inspection Scope
The inspectors evaluated, as appropriate, for the work activities listed below:
1) the effectiveness of the risk assessments performed before maintenance activities were conducted; 2) the management of risk; 3) that, upon identification of an unforeseen situation, necessary steps were taken to plan and control the resulting emergent work activities; and 4) that maintenance risk assessments and emergent work problems were adequately identified and resolved. The inspectors verified that the licensee was complying with the requirements of 10 CFR 50.65 (a)(4);procedures NPG-SPP-07.0, Work Control and Outage Management; NPG-SPP-07.1, On Line Work Management; and TI-124, Equipment to Plant Risk Matrix. Documents reviewed are listed in the
. This activity constituted six Maintenance Risk Assessment inspection samples, as defined in IP 71111.13.
- Risk assessment for work week 0803 with auxiliary feedwater valve stroke testing
- Risk assessment for work week 0914 with B train MCR chiller OOS for maintenance and 1B-B emergency diesel generator (EDG) fast start and load test
- Risk assessment for 09/22/15 during refueling outage with reactor coolant system (RCS) filled, capable of being pressurized, and no core alterations in progress
- Risk assessment for 09/25/15 during refueling outage with RCS partially drained, core alterations in progress, and time to core boil calculated at 30 minutes
b. Findings
No findings were identified.
1R15 Operability Evaluations
a. Inspection Scope
The inspectors reviewed the operability evaluations affecting risk-significant mitigating systems listed below, to assess, as appropriate: 1) the technical adequacy of the evaluations; 2) whether continued system operability was warranted; 3) whether the compensatory measures, if involved, were in place, would work as intended, and were appropriately controlled; 4) where continued operability was considered unjustified, the impact on TS Limiting Conditions for Operation (LCO) and the risk significance in accordance with the significant determination process (SDP). The inspectors verified that the operability evaluations were performed in accordance with NPG-SPP-03.1, Corrective Action Program. Additional documents reviewed are listed in the attachment.
This activity constituted seven Operability Evaluation inspection samples, as defined in IP 71111.15.
- CR 1044468 Component cooling water procedure missing steps
- CR 1063890, Water leaking into relay room from crack in ceiling
- CR 1049837, Lower compartment weighted average calculation incorrect
- CR 1070001, ERCW through wall pipe leak on pump B-A vent line piping
- CR 1071119, Seismic monitor red event lights lit
- CR 1077708, A Train intake pumping station sump pumps failed to operate in AUTO and MANUAL
b. Findings
No findings were identified.
1R19 Post-Maintenance Testing
a. Inspection Scope
The inspectors reviewed the post-maintenance test procedures and/or test activities, (listed below) as appropriate, for selected risk-significant mitigating systems to assess whether: 1) the effect of testing on the plant had been adequately addressed by control room and/or engineering personnel; 2) testing was adequate for the maintenance performed; 3) acceptance criteria were clear and adequately demonstrated operational readiness consistent with design and licensing basis documents; 4) test instrumentation had current calibrations, range, and accuracy consistent with the application; 5) tests were performed as written with applicable prerequisites satisfied; 6) jumpers installed or leads lifted were properly controlled; 7) test equipment was removed following testing; and 8) equipment was returned to the status required to perform its safety function. The inspectors verified that these activities were performed in accordance with NPG-SPP-06.9, Testing Programs; NPG-SPP-06.3, Pre-/Post-Maintenance Testing; and NPG-SPP-07.1, On Line Work Management. Documents reviewed are listed in the attachment. This activity constituted five Post Maintenance Testing inspection samples, as defined in IP 71111.19.
- Work Order (WO) 116870153, PMT following 1B RHR pump run following flow transmitter sensing line replacement
- WO 116567841, PMT following seal water heat exchanger outlet relief valve replacement
- WO 117101575, PMT following IPS sump pump 2A switch replacement
- WO 112798694, PMT following 1B-B ERCW strainer drum and screen inspection and packing replacement
- WO 115944299, PMT following temperature control valve replacement on the B Main Control Room Chiller
b. Findings
No findings were identified.
1R20 Refueling and Outage Activities
a. Inspection Scope
The inspectors reviewed the outage risk control plan for the Unit 1 Cycle 13 (1R13)refueling outage (RFO) to assess whether the licensee had appropriately considered risk, industry experience, and previous site-specific problems, and to also confirm that the licensee had mitigation/response strategies for losses of key safety functions.
The licensee began its 1R13 refueling outage on September 20, 2015. From that date through the end of this reporting period, the inspectors observed portions of the shutdown, cooldown, defueling, and maintenance activities to verify that the licensee maintained defense-in-depth (DID) commensurate with the outage risk plan and applicable TS.
The inspectors monitored licensee controls over the outage activities listed below. In addition, the inspectors reviewed the licensees corrective action program to ensure that the licensee was identifying equipment alignment problems and that they were properly addressed for resolution. This activity constituted a partial sample of refueling and outage activities, as defined in IP 71111.20.
- Licensee configuration management, including daily outage reports, to evaluate DID commensurate with the outage safety plan and compliance with the applicable TS when taking equipment OOS.
- Installation and configuration of reactor coolant instruments to provide accurate indication and an accounting for instrument error
- Controls over the status and configuration of electrical systems and switchyard to ensure that TS and outage safety plan requirements were met
- Decay heat removal processes to verify proper operation and that steam generators, when relied upon, were a viable means of backup cooling
- Controls to ensure that outage work was not impacting the ability to operate the spent fuel pool cooling system during and after core offload
- Reactor water inventory controls including flow paths, configurations, and alternative means for inventory addition, and controls to prevent inventory loss
- Reactivity controls to verify compliance with TS and to verify that activities which could affect reactivity were reviewed for proper control within the outage risk plan
b. Findings
No findings were identified.
1R22 Surveillance Testing
a. Inspection Scope
The inspectors witnessed the surveillance tests and/or reviewed test data of selected risk-significant SSCs listed below, to assess, as appropriate, whether the SSCs met the requirements of the TS; the UFSAR; NPG-SPP-06.9, Testing Programs; NPG-SPP-06.9.2, Surveillance Test Program; and NPG-SPP-09.1, ASME Section XI. The inspectors also determined whether the testing effectively demonstrated that the SSCs were operationally ready and capable of performing their intended safety functions.
Documents reviewed are listed in the Attachment. This activity constituted five Surveillance Testing inspection samples; one in-service; two routine; one RCS leakage; one containment isolation valve, as defined in IP 71111.22.
In-Service Test
- WO 116153257, 1-SI-1-907, Testing of Main Steam Safety Valve 1-SFV-519 Other Surveillances
- WO 116517484, 1-SI-3-412, 92 Day Trip Actuating Device Operational Test South Valve Vault Level Switch Channel I, 1-LS-3-402
- WO 166734502, 1-SI-0-53.1-B, 18 Month Remote Shutdown Transfer Switch Verification Pre-Outage Performance - Train B RCS Leakage
- WO 117092019, 1-SI-68-32, Reactor Coolant System Water Inventory Balance Containment Isolation Valve
- WO 116153460, 1-SI-26-701, Containment Isolation Valve Local Leak Rate Test, High Pressure Fire Protection.
b. Findings
No findings were identified.
Cornerstone: Emergency Preparedness
1EP6 Drill Evaluation
a. Inspection Scope
The inspectors observed an EP REP training drill that contributed to the licensees Drill/Exercise Performance (DEP) and Emergency Response Organization (ERO)performance indicator (PI) measures on August 26, 2015. This drill was intended to identify any licensee weaknesses and deficiencies in classification, notification, dose assessment and protective action recommendation (PAR) development activities. The inspectors observed emergency response operations in the Technical Support Center, to verify that event classification and notifications were done in accordance with EPIP-1, Emergency Classification Procedure, and licensee conformance with other applicable Emergency Plan Implementing Procedures. The inspectors attended the post-drill critiques to compare any inspector-observed weaknesses with those identified by the licensee in order to verify whether the licensee was properly identifying EP related issues and entering them in to the CAP, as appropriate. Documents reviewed are listed in the attachment. This activity constituted one EP training drill inspection sample, as defined in IP 71114.06.
b. Findings
No findings were identified.
4OA2 Problem Identification and Resolution
.1 Review of Items Entered into the Corrective Action Program (CAP)
a. Inspection Scope
As required by Inspection Procedure 71152, Problem Identification and Resolution, and in order to help identify repetitive equipment failures or specific human performance issues for follow-up, the inspectors performed a daily screening of items entered into the licensees CAP. This review was accomplished by reviewing daily problem evaluation report (PER) summary reports and attending daily PER review meetings. Documents reviewed are listed in the attachment.
b. Findings
No findings were identified.
.2 Semiannual Trend Review
a. Inspection Scope
As required by Inspection Procedure 71152, the inspectors performed a review of the licensees CAP and other associated programs and documents to identify trends that could indicate the existence of a more significant safety issue. The inspectors review was focused on repetitive equipment issues, but also included licensee trending efforts and licensee human performance results. The inspectors review nominally considered the six-month period of April through September 2015, although some examples expanded beyond those dates when the scope of the trend warranted. Inspectors reviewed licensee trend reports for the period in order to determine the existence of any adverse trends that the licensee may not have previously identified. The inspectors review also included the licensees integrated trend reports. The inspectors verified that adverse or negative trends identified in the licensees PERs, periodic reports, and trending efforts were entered into the CAP. Documents reviewed are listed in the attachment. This inspection satisfied one inspection sample for Semiannual Trend Review, as defined in IP 71152.
b. Findings and Observations
No findings were identified. In general, the licensee had identified trends and appropriately addressed them in their CAP. The inspectors observed that the licensee had performed a detailed review. The licensee routinely reviewed cause codes and utilized key words and system links to identify potential trends in their data. The majority of licensee-identified trends were identified by the quality assurance organization over this time period. Inspectors had observed and commented on the same trends that the licensee was identifying, particularly the negative trends in procedure use and adherence, emergency drill performance, and timeliness of condition report initiation.
The inspectors also noted that the licensee identified an adverse trend where condition reports were transitioned directly to a work order, despite having the potential operability flag set to yes. The licensee identified 20 CRs with the operability flag set to yes that were not entered into the corrective action program (i.e., they were not identified as being a level A, B, or C level CR). The licensee entered this trend into their CAP as CR 107229. Corrective actions included a software change that checks the corrective action box when the potential operability flag is set to yes. The licensees performance improvement group will also monitor a report of CRs that are sent directly to work orders to ensure operability concerns are being correctly captured in the CAP.
The inspectors also compared the licensee trend process results with the results of the inspectors daily screening. No new adverse trends were identified this period by the inspectors that had not already been identified by the licensee.
.3 Annual Sample: PER 1044983 Related to the U1 Turbine Driven Auxiliary Feedwater
Pump DC Fan Failure
a. Inspection Scope
The inspectors performed an in-depth review of the licensees evaluation and corrective actions associated with PER 1044983 related to failure of the Unit 1 turbine-driven auxiliary feedwater pump (TDAFWP) DC room fan being discovered not running in auto when demanded. The inspectors reviewed the PER, previous failures and corrective actions, program monitoring, and failure analysis to ensure that the licensee planned and/or implemented corrective actions were commensurate with the safety significance of the issue. The basis for selecting this sample for review was based on the potential safety significance of the issue and the repetitive nature of this specific component failure. The potential safety significance of this issue was based on the necessity of the TDAFWP DC fan to maintain operability of the TDAFWP. This activity constituted one sample of Annual Follow-up of Selected Issues, as defined in IP 71152.
b. Finding and Observations No findings were identified; however, the inspector identified one observation. The inspector identified a weakness in the initiation and review of this PER associated with the identification of the potential need for a reportability review. Based on the equipment involved and the effect of the fans failure on the operability of the TDAFWP, this CR should have been flagged for a reportability review during the PSC review meeting as described in NPG-SPP-22.300. This was not completed and resulted in a potentially reportable condition going unidentified.
.4 Annual Sample: CRs 999379, 1008455, and 1022445 - Emergency Diesel Generator
Subcomponent Aging Issues
a. Inspection Scope
The inspectors performed an in-depth review of the licensees evaluation and corrective actions associated with CRs 999379, 1008455, and 1022445 related to failure of diesel generator subcomponents due to aging. The inspectors reviewed the CRs, previous failures and corrective actions, program monitoring, and failure analysis to ensure that the licensees planned and/or implemented corrective actions were commensurate with the safety significance of the issue. The basis for selecting this sample for review was based on the potential safety significance of the issue and a similar mechanism for component failure. The potential safety significance of this issue was based on the necessity of the diesel generators to provide emergency AC power. This activity constitutes one inspection sample for Annual Follow-up of Selected Issues, as defined in IP 71152.
b. Finding and Observations No findings were identified; however, the inspector observed a recent increase in issues associated with aging of commponents related to the EDG:
On March 15, 2015, during performance of 0-SI-82-18-B, the 6-month fast start surveillance for the 1B-B EDG, the normal supply valve for the ERCW failed to remain open as required for EDG operation. As a result of the loss of cooling water, the EDG was stopped until the valve was blocked open and the EDG restored to normal lineup.
Troubleshooting revealed that aging of a plastic bump guard on a hand switch caused the guard to shrink and prevent the spring return switch from returning to the open position. This left the switch in the closed position, thereby preventing the cooling valve from opening.
Corrective actions were taken to evaluate switches for the other three diesel generators for similar problems. Additional corrective actions were taken to walk down other similar hand switches in other plant systems.
On April 2, 2015, the EDG 2B-B experienced kilowatt oscillations while loaded for approximately 15 minutes. During this time, oscillation swings up to 500 kilowatt were noted. Troubleshooting revealed that the cause was oxidation affecting the potentiometer for the 2301A governor steady state speed setting. The potentiometer was adjusted on March 29, 2015, when performing frequency adjustments for the governor to a new isochronous band of 59.9 to 60.0 Hz (WO 115155953 for design change notice [DCN] 63886).
The inspectors reviewed the licensees decision not to account for potentiometer oxidation by rotating or swiping the potentiometers. Although the licensee was aware of industry operating experience regarding oxidation buildup on potentiometers, these potentiometers were sealed, which would limit contamination of the potentiometer. In addition, there was no method to verify the potentiometer resistance as-left value if a potentiometer swipe was conducted. The licensee decided to not swipe the potentiometer, because if the potentiometer was left way out of value due to swiping, the EDG could either flash the field and not get to 850 RPM when field flash is secured, or overspeed the EDG on startup.
Corrective actions were taken to swipe potentiometers for the other three diesel generators to prevent similar problems.
On May 5, 2015, during performance of 0-SI-82-12-B, Monthly Loaded Surveillance for the Emergency Diesel Generator (EDG) 2B-B, kilowatt load oscillations were noted by the assistant unit operator in the diesel room one hour into the loaded run. The assistant unit operator informed the MCR and the EDG was stopped normally. Troubleshooting revealed that the cause of the KW oscillations was the 2301A governor card, specifically the droop circuit portion. The cause for the circuit failure was preventative maintenance that did not account for aging of all of the 2301A governor card components. The droop circuit is only used when the diesel generator is synchronized to the electric grid, and, therefore, the diesel would have been able to perform its safety-related function of powering the safety-related shutdown boards in the isochronous mode.
The inspectors reviewed the root cause and noted that the licensee conducted 10-year replacements of the electrolytic capacitors on the governor card. Based on vendor information, the majority of plants replace the whole controller card instead of just the two capacitors. Watts Bar 2301A controllers were installed in 1999 under DCN M-39767-A. Since installation, the capacitor replacement was conducted in 2006, and, therefore, the other 2301A components were over 16 years old when the oscillations were observed. To ensure all components of the 2301A card were addressed for aging, the 10-year preventative maintenance for capacitor replacement was revised by the licensee to replace the entire governor card.
The inspectors observed and reviewed samples of diesel generator monthly load tests, as well as a blackout test of the 1A-A diesel generator, since the licensee corrective actions were taken. No similar problems have occurred.
4OA5 Other Activities
Temporary Instruction 2515/190 - Inspection of the Proposed Interim Actions Associated with Near-Term Task Force Recommendation 2.1 Flooding Hazard Evaluations.
The inspectors independently verified that the licensees proposed interim actions would perform their intended function for flooding mitigation.
- Visual inspection of the flood protection feature was performed if the flood protection feature was relevant. External visual inspection for indications of degradation that would prevent its credited function from being performed was performed.
- Reasonable simulation was performed, if applicable to the site
- Flood protection feature functionality was determined using both visual observation and review of other documents.
The inspectors completed the required inspections for this Temportary Instruction and verified that issues identified were entered into the licensee's corrective action program.
4OA6 Meetings, including Exit
On October 16, 2015, the resident inspectors presented the quarterly inspection results to members of the licensee staff. The inspectors confirmed that none of the potential report input discussed was considered proprietary.
SUPPLEMENTARY INFORMATION
KEY POINTS OF CONTACT
Licensee Personnel
- L. Belvin, Quality Assurance Manager
- M. Bottorff, Operations Superintendent
- M. Casner, Director, Engineering
- S. Connors, Plant Manager
- T. Detchemende, Emergency Preparedness Manager
- S. Fisher, Senior Manager, Nuclear Site Security
- W. Hooks, Radiation Protection Manager
- J. James, Director, Maintenance
- J. ODell, Site Licensing Supervisor
- G. Pry, Director, Plant Support
- J. Reidy, Director, Operations
- P. Stephens, Senior Manager, Chemistry
- R. Stroud, Site Licensing
- M. Taggart, Director, Work Management
- K. Walsh, Site Vice President
ITEMS OPENED, CLOSED, AND DISCUSSED
Opened
None
Closed
2515/190 TI-190 Inspection of the Proposed Interim Actions Associated with Near-Term Task Force Recommendation 2.1 Flooding Hazard Evaluations.
Discussed
None