05000315/LER-2002-006, Switchyard Fire Results in Violation of Technical Specification 3.0.5
| ML022200452 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 08/02/2002 |
| From: | Joseph E Pollock Indiana Michigan Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 02-006-00 | |
| Download: ML022200452 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3152002006R00 - NRC Website | |
text
Indiana Michigan Power Company 500 Circle Drive Buchanan, MI 49107 1395 INDIANA MICHIGAN POWER August 2, 2002 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Operating Licenses DPR-58 Docket Nos. 50-315 Document Control Manager:
In accordancewith the criteria established by 10 CFR 50.73 entitled Licensee Event Report System, the following report is being submitted:
LER 315/2002-006-00: 'Switchyard Fire Results in Essential Service Water System being Inoperable" No new commitments are identified in this submittal.
Should you have any questions regarding this correspondence, please contact Mr. Gordon P. Arent, Manager, Regulatory Affairs, at (616) 697-5553.
Sincerely, Pollock Site Vice President I NJ/pae Attachment
C:
G. P. Arent A. C. Bakken L.
Brandon J. E. Dyer, Region III R. W. Gaston S. A.
Greenlee T. P.
Noonan R. P.
Powers M. W. Rencheck R.
Whale NRC Resident Inspector Records Center, INPO
Abstract
On June 12, 2002, at 1345 hours0.0156 days <br />0.374 hours <br />0.00222 weeks <br />5.117725e-4 months <br />, the "BC" 34.5 kilovolt (kV) circuit breaker opened and a trouble alarm for the TRI 01 CD reserve auxiliary transformer was received in the control room. This was caused by an explosion in the 345 kV switchyard and oil fire in the 'L" switchyard output feeder breaker. This resulted in the loss of the preferred offsite power source to the Unit 1 East Essential Service Water (ESW) pump. Since the Unit 2 East ESW pump was out of service for planned maintenance to replace the pump, Unit 1 entered the 2-hour action requirement of Technical Specification (TS) 3.0.5 at 1345 hours0.0156 days <br />0.374 hours <br />0.00222 weeks <br />5.117725e-4 months <br />. Subsequent protective switching by the system load dispatcher resulted in the loss of the preferred offsite power source to the Unit 2 West ESW pump and Unit 2 also entered the 2-hour action requirement of TS 3.0.5 at 1359 hours0.0157 days <br />0.378 hours <br />0.00225 weeks <br />5.170995e-4 months <br />. Donald C. Cook Nuclear Plant (CNP) requested and received enforcement discretion from the NRC to extend the 2-hour allowed action time by 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> to allow sufficient time to restore the Unit 2 East ESW pump to an operable status and exit TS 3.0.5. This Licensee Event Report (LER) is being submitted in accordance with the requirements of 10 CFR 50.73 (a)(2)(i)(B) for operation or condition prohibited by the TS.
CNP determined that compliance with TS 3.0.5 to place both Unit 1 and Unit 2 in Mode 3 within the time required by the action statement could initiate an undesirable transient. In addition, due to the degraded material condition of the switchyard at the time of the event, the risk associated with maintaining both units on line for an additional 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> was less than the risk associated with taking both Unit 1 and Unit 2 off line. Therefore, there was no net increase in risk associated with operating the plant for approximately 10 additional hours. CNP completed replacement and testing of the Unit 2 East ESW pump and exited TS 3.0.5.
NRC FORM 366 (7-2001)U.S. NUCLEAR REGULATORY COMMISSION (7-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REVISION Donald C. Cook Nuclear Plant Unit 1 05000-315 NUMBER NUMBER 2 of 3 2002 006 00
- 17. TEXT (if more space is required, use additional copies of NRC Form (366A)
Conditions Prior to Event
Unit 1 - Mode 1, 69 percent power Unit 2 - Mode 1, 100 percent power
Description of Event
On June 11, 2002, the Unit 2 East essential service water (ESW) pump was out of service for planned maintenance to replace the pump. Because the ESW crosstie valves were open between the units to support the pump maintenance, the Unit 1 West ESW pump was also inoperable in accordance with Technical Specification (TS) 3.7.4.1. The ESW crosstie valves were maintained open to preclude depressurizing the Unit 2 East ESW header and thereby rendering that train of ESW unavailable.
On June 12, 2002, at 1345 hours0.0156 days <br />0.374 hours <br />0.00222 weeks <br />5.117725e-4 months <br />, the 'BC" 34.5 kilovolt (kV) circuit breaker opened and a trouble alarm for the TR101CD reserve auxiliary transformer was received in the control room. This was caused by an explosion in the 345 kV switchyard and oil fire in the 'L" switchyard output feeder breaker. As a result, the TR4 reserve feed transformer was rendered inoperable, affecting the CD bus of reserve feed. This resulted in a loss of the preferred offsite power source to the Unit 1 East ESW pump and the unit entered the 2-hour action requirement of TS 3.0.5 at 1345 hours0.0156 days <br />0.374 hours <br />0.00222 weeks <br />5.117725e-4 months <br />. Subsequent protective switching by the system load dispatcher resulted in the TR5 reserve feed transformer being de-energized, affecting the AB bus of reserve feed. This resulted in a loss of the preferred offsite power source to the Unit 2 West ESW pump and Unit 2 also entered the 2-hour action requirement of TS 3.0.5 at 1359 hours0.0157 days <br />0.378 hours <br />0.00225 weeks <br />5.170995e-4 months <br />. In accordance with the Donald C. Cook Nuclear Plant (CNP) emergency response procedure, an Alert was declared at 1404 hours0.0163 days <br />0.39 hours <br />0.00232 weeks <br />5.34222e-4 months <br /> due to the fire/explosion in the 345 kV switchyard. The Nuclear Regulatory Commission Operations Center was notified at 1418 hours0.0164 days <br />0.394 hours <br />0.00234 weeks <br />5.39549e-4 months <br /> (see event notification 38983 for details of the switchyard event).
With both ESW trains and their power sources inoperable, the units entered the 2-hour action requirements of TS 3.0.5 to commence placing the units in cold shutdown. On June 12, 2002, at 2115 hours0.0245 days <br />0.588 hours <br />0.0035 weeks <br />8.047575e-4 months <br />, CNP received enforcement discretion from the NRC to extend the 2-hour allowed action time by 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> to allow sufficient time to restore the Unit 2 East ESW pump to an operable status and exit TS 3.0.5. This Licensee Event Report is being submitted in accordance with the requirements of 10 CFR 50.73 (a)(2)(i)(B) for operation or condition prohibited by the TS.
On June 12, 2002, at 2123 hours0.0246 days <br />0.59 hours <br />0.00351 weeks <br />8.078015e-4 months <br />, plant operators declared the Unit 1 West ESW pump operable and exited T.S. 3.0.5 when crosstie valve 2-WMO-708 was closed to allow for post-maintenance testing of the Unit 2 East ESW pump. At 2157 hours0.025 days <br />0.599 hours <br />0.00357 weeks <br />8.207385e-4 months <br />, the Unit 2 East ESW pump performed within required limits and plant operators declared the pump operable and exited TS 3.0.5.
Cause of Event
CNP determined that compliance with TS 3.0.5 to place both Unit 1 and Unit 2 in Mode 3 within the time required by the action statement could initiate an undesirable transient. A contributing cause was determined to be the explosion of the current transformer due to an internal fault.U.S. NUCLEAR REGULATORY COMMISSION (7-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REVISION Donald C. Cook Nuclear Plant Unit 1 05000-315 NUMBER NUMBER 3 of 3 2002 006 0- 0
- 17. TEXT (If more space is required, use additional copies of NRC Form (366A)
Analysis of Event
The reserve auxiliary transformers are the preferred source of off-site power when the units are tripped or shut down.
Following the switchyard event, Unit 1 and Unit 2 were stable with power being supplied by the unit main generators through the unit auxiliary transformers. The reserve source of offsite power was only available through a single transformer (TR5) and voltage output from this transformer was below the operability range, but stable. Additionally, the CNP switchyard and the local area grids were in a degraded voltage condition due to the tie-lines in the 345 kV switchyard being open. In this degraded condition, taking the units off line would change the electrical load flow patterns on the grid and would increase the probability of grid instability and the likelihood of a loss of offsite power. Additionally, in taking the units off line, unit loads would be transferred to the TR5 reserve transformer, further increasing the probability of a loss of power from this source due to its low voltage. Loss of offsite power would cause a significant plant transient, resulting in the emergency diesel generators (EDG) supplying the safety-related electrical buses, loss of forced flow through the reactor core, and a loss of the normal heat sink for the core (circulating water cooling of the main condensers).
CNP determined that compliance with TS 3.0.5 to place both Unit 1 and Unit 2 in Mode 3 within the time required by the action statement could initiate an undesirable transient. In addition, due to the current degraded material condition of the switchyard at the time of the event, the risk associated with maintaining both units on line for an additional 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> was less than the risk associated with taking both Unit 1 and Unit 2 off line. This analysis supported CNP's request for enforcement discretion that was verbally approved on June 12, 2002, at 2115 hours0.0245 days <br />0.588 hours <br />0.0035 weeks <br />8.047575e-4 months <br />. Therefore, no corresponding health and safety benefit would be gained by requiring a plant shutdown.
Corrective Actions
CNP completed replacement and testing of the Unit 2 East ESW pump and exited TS 3.0.5. Actions to address the current transformer fault will be determined as part of the root cause investigation.
Previous Similar Events
None