05000259/LER-2018-003, For Browns Ferry Nuclear Plant, Units 1, 2, and 3, Unanalyzed Condition Due to an Incorrectly Wired Breaker on Emergency Equipment Cooling Water Pump
| ML18149A495 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/29/2018 |
| From: | Hughes D Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 2018-003-00 | |
| Download: ML18149A495 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 2592018003R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 May 29, 2018 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Units 1, 2, and 3 10 CFR 50.73 Renewed Facility Operating License Nos. DPR-33, DPR-52, and DPR-68 NRC Docket Nos. 50-259, 50-260, and 50-296
Subject:
Licensee Event Report 50-259/2018-003-00 The enclosed Licensee Event Report provides details of an unanalyzed condition associated with the Browns Ferry Nuclear Plant Emergency Equipment Cooling Water (EECW) System. During postulated fire events where the C3 EECW pump is credited for Control Room Abandonment scenarios, combined with a loss of offsite power, the pump could trip on undervoltage and fail to restart. This would cause a loss of the EECW system's credited function for these events. The Tennessee Valley Authority is submitting this report in accordance with 10 CFR 50. 73(a)(2)(ii)(B), as any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degraded plant safety.
There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact J. L. Paul, Nuclear Site Licensing Manager, at (256) 729-2636.
Respectfully, LL~lFOR.\\
D. L. Hughes, Site Vice President Enclosure: Licensee Event Report 50-259/2018-003 Unanalyzed Condition due to an Incorrectly Wired Breaker on Emergency Equipment Cooling Water Pump cc (w/ Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant NRC Project Manager - Browns Ferry Nuclear Plant
ENCLOSURE Browns Ferry Nuclear Plant Units 1, 2, and 3 Licensee Event Report 50-259/2018-003-00 Unanalyzed Condition due to an Incorrectly Wired Breaker on Emergency Equipment Cooling Water Pump See Enclosed
CNRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)
, the NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. Page Browns Ferry Nuclear Plant (BFN), Unit 1 05000259 1 OF 6
- 4. Title Unanalyzed Condition due to an Incorrectly Wired Breaker on Emergency Equipment Cooling Water Pump
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved I
Sequential I Rev Facility Name Docket Number Month Day Year Year Month Day Year BFN, Unit 2 05000260 Number No.
Facility Name Docket Number 03 29 2018 2018 - 003
- - 00 05 29 2018 BFN, Unit 3 05000296
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply)
D 20.2201(b)
D 20.2203(a)(3)(i)
D 50.73(a)(2)(ii)(A)
D 50. 73(a)(2)(viii)(A)
D 20.2201 (d)
D 20.2203(a)(3)(ii)
~ 50. 73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B) 1 D 20.2203(a)(1 l D 20.2203{a){4)
D 5o.73(a)(2){iii)
D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(i)
D 50.36(c)(1 )(i)(A)
D 50. 73(a)(2)(iv)(A)
D 50. 73(a)(2)(x)
- 10. Power Level D 20.2203(a)(2)(ii)
D 50.36(c)(1 )(ii)(A)
D 50. 73(a)(2)(v)(A)
D 73. 71 (a)(4)
D 20.2203(a)(2)(iii)
D 5o.36(c)(2)
D 50.73(a)(2){v)(B)
D 13.11(a)(5)
D 20.2203{a){2)(iv)
D 50.46(a)(3)(ii)
D 50. 73(a){2)(v)(C)
D 13.77(a)(1) 100 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50. 73(a)(2)(v)(D)
D 73. 77(a)(2)(i)
D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i){B)
D 50.73(a)(2)(vii)
D 73. 77(a)(2)(ii)
D 50.73(a)(2)(i)(C)
D OTHER Specify in Abstract below or in 2018 -
003
C. Dates and approximate times of occurrences
Date August 23, 2012 March 8, 2018 March 10, 2018 March 29, 2018 March 29, 2018 Time 1247 CDT 0130 CST 2042 CDT 1344 CDT 2128 CDT Event Work complete on Work Order 113567386. This was the last work performed on the C3 EECW Pump breaker prior to discovery of this condition.
Incorrect wiring discovered on C3 EECW Pump breaker during a relay functional test of the trip circuit.
Maintenance personnel completed work to correct the field wiring for the pump breaker.
A Past Operability Evaluation (POE) determined that an unanalyzed condition existed which affected the C3 EECW Pump.
Event Notification 53300 made to the NRC.
D. Manufacturer and model number of each component that failed during the event
This condition did not involve any failed components.
E. Other systems or secondary functions affected
There were no other systems or secondary functions affected by this condition.
00
F. Method of discovery of each component or system failure or procedural error
There were no component failures, system failures, or procedural errors associated with this condition.
G. Failure mode, mechanism, and effect of each failed component This condition did not involve any failed components.
H. Operator actions
There were no operator actions taken as a result of this condition.
I.
Automatically and manually initiated safety system responses
There were no safety system responses initiated as a result of this condition.
Ill.
Cause of the Event
A. Cause of each component or system failure or personnel error Human performance tools which could have prevented this condition were not utilized.
This issue was a legacy human performance issue which could have been prevented through the use of the "Stop When Unsure" HU tool. The use of the "Stop When Unsure" HU tool has since been covered under the Procedure Adherence rollout in 2017.
IV.
Analysis of the Event
The safety objective of the EECW System is to provide cooling water to the Standby Diesel [DG]
engine [ENG] coolers [LB], the Residual Heat Removal [BO] pump seal coolers and pump room coolers, the Core Spray [BG] pump room coolers, the Unit 3 Control Bay chillers [CHU], Unit 3 Shutdown Board (SDBD) [ECBD] Room Chillers, Unit 3 Electrical Board Room Air Conditioning Units, and additional makeup for the fuel pool. There are four service water pumps dedicated to the EECW system that supply two independent headers.
The C3 EECW Pump Breaker was wired in an incorrect manner that prevented the breaker closing springs from recharging while the transfer switch was in the emergency position. The manual action of taking the transfer switch to the emergency position would occur locally at the breaker if the MCR was abandoned during an event resulting in an entry into the Fire Safe Shutdown (FSS) procedures. Because of the incorrect wiring, no wiring connection existed from the emergency DC control power to the closing spring charging motor. As a result, the breaker closing springs would be unable to be recharged with the transfer switch in the emergency position. Since power was available to the close charging spring with the transfer switch in the normal position, the closing spring would have been charged when the operators placed the transfer switch in emergency. With the spring charged when the transfer switch was taken to emergency, the breaker could be closed one time. However, there are postulated scenarios where the breaker would have to close more than once with the transfer switch in emergency.
The closing spring would not have recharged resulting in unavailability of the C3 EECW pump.
BFN FSS procedures for MCR Abandonment require that at least two EECW pumps are in service, and include steps to align the A3 and C3 EECW Pumps from Backup Control.
Assuming the C3 EECW pump had to be started once with the transfer switch in emergency, a subsequent LOOP during a MCR Abandonment scenario could have resulted in a condition where the C3 EECW Pump would trip and fail to restart, causing a loss of safety function for a required EECW pump during a fire event.
V.
Assessment of Safety Consequences
A Probabilistic Risk Assessment performed by TVA determined that the risk significance of this condition was negligible, corresponding to a maximum change in Core Damage Frequency of less than 1 E-6/yr and change in Large Early Release Frequency less than 1 E-7/yr. Therefore, there is no significant impact to the health and safety of the public from this condition.
A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event Two EECW pumps are required for aligning the EECW system from backup control.
The FSS procedure for Units 1, 2, and 3 includes steps for aligning A3 and C3 EECW pumps from backup control. While 4160V Shutdown Board C would be aligned for abandonment and the 83 EECW Pump would have been available, the FSS procedure for control room abandonment does not contain steps for starting the B3 EECW Pump from backup control.
The POE determined that even with the C3 EECW backup control function lost, the system was not operated outside the TS limitations since the 83 and D3 EECW Pumps and their backup control functions would have been restored within seven days per TS LCO 3.7.2.
B. For events that occurred when the reactor was shut down, availability of systems or components needed to shut down the reactor and maintain safe shutdown conditions, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident During the period when this condition existed there were multiple time periods when one or more 8FN reactors were shut down. However, the EECW system's Backup Control functions are only required to be Operable in Modes 1 and 2.
C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsed time from the discovery of the failure until the train was returned to service This condition did not result in the TS inoperability of any safety system. However, this condition rendered the C3 EECW Pump, which is credited for some fire scenarios, unavailable for the purposes of those scenarios.
VI.
Corrective Actions
This condition was entered into the TVA Corrective Action Program (CAP) and is being tracked under Condition Report 1394604.
2018 003
A. Immediate Corrective Actions
The immediate corrective action was to correctly rewire the circuitry for the C3 EECW Pump breaker. The circuitry was repaired on March 10, 2018.
00 B. Corrective Actions to Prevent Recurrence or to reduce probability of similar events occurring in the future Plant procedures will be revised in order to add HU tools which verify, during testing, that the breaker springs will recharge while the transfer switch is in the emergency position.
VII.
Previous Similar Events at the Same Site
A review of the BFN CAP and Licensee Event Reports for Units 1, 2, and 3 found no instances within the past five years of degraded or unanalyzed conditions on the EECW Pumps which resulted from improper wiring.
VIII.
Additional Information
There is no additional information.
IX.
Commitments
There are no new commitments. Page _6_ of _6_