05000237/LER-2004-003-01, (Supplemental) for Dresden Nuclear Power Station, Units 2 and 3 Scram Due to Loss of Offsite Power and Subsequent Inoperability of the Standby Gas Treatment System for Units 2 and 3
| ML043140263 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 10/29/2004 |
| From: | Bost D Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| SVPLTR # 04-0071 LER 04-003-01 | |
| Download: ML043140263 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2372004003R01 - NRC Website | |
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Exeltms Exelon Generation Company, LLC www.exeloncorp.com E
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Dresden Nuclear Power Station Nuclear 6500 North Dresden Road Morris, IL 60450-9765 10 CFR 50.73 October 29, 2004 SVPLTR: #04-0071 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Units 2 and 3 Facility Operating License Nos. DRP-19 and DPR-25 NRC Docket Nos. 50-237 and 50-249
Subject:
Supplemental Licensee Event Report 2004-003-01, 'Unit 3 Scram Due to Loss of Offsite Power and Subsequent Inoperability of the Standby Gas Treatment System for Units 2 and 3" Enclosed is Supplemental Licensee Event Report 2004-003-01, 'Unit 3 Scram Due to Loss of Offsite Power and Subsequent Inoperability of the Standby Gas Treatment System for Units 2 and 3," for Dresden Nuclear Power Station. This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A), "Any event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph (a)(2)(iv)(B) of this section," and 10 CFR 50.73(a)(2)(i)(B), 'Any operation or condition which was prohibited by the plant's Technical Specifications."
Should you have any questions concerning this report, please contact Jeff Hansen, Regulatory Assurance Manager, at (815) 416-2800.
Respectfully, Danny 9Bost Site V~6e President Dresden Nuclear Power Station Enclosure cc:
Regional Administrator - NRC Region IlIl NRC Senior Resident Inspector - Dresden Nuclear Power Station
Abstract
On May 5, 2004, at 1327 hours0.0154 days <br />0.369 hours <br />0.00219 weeks <br />5.049235e-4 months <br /> (CDT), with Unit 3 at 100 percent power in Mode 1, an automatic scram occurred due to a Main Generator Load Reject when a loss of offsite power occurred. The Emergency Diesel Generators automatically started and powered their respective electrical busses. All control rods fully inserted and Group 1, 1I and IlIl isolations occurred as expected. Operations personnel manually initiated the Isolation Condenser System for reactor pressure control, the High Pressure Coolant Injection System for reactor water level control, and the Low Pressure Coolant Injection System for Torus cooling. All systems initially responded to the scram as expected except the Standby Gas Treatment System was unable to maintain the Secondary Containment at the Technical Specification Surveillance Requirement limit of greater than or equal to 0.25 inches of vacuum water gauge. An Unusual Event for the loss of offsite power was declared at 1342 hours0.0155 days <br />0.373 hours <br />0.00222 weeks <br />5.10631e-4 months <br /> (CDT) and terminated at 1601 hours0.0185 days <br />0.445 hours <br />0.00265 weeks <br />6.091805e-4 months <br /> (CDT) on May 5, 2004. Additionally, during restoration of offsite electrical power to Bus 33, the Emergency Diesel Generator 2/3 output electrical breaker tripped.
The root causes associated with the load reject and loss of offsite power and the low Secondary Containment vacuum were respectively, equipment failure in the "C" phase of the 345 kilovolt circuit breaker 8-15 and a degraded Secondary Containment boundary not detected due to an inadequate leak rate test procedure. The investigation into the apparent cause of the Emergency Diesel Generator output breaker trip was indeterminate.
(If more space Is required, use additional copies of (If more space Is required, use additional copies of (If more space Is required, use additional copies of NRC Form 366A)
E.
Corrective Actions
345 kv circuit breaker 8-15 was repaired and a vendor upgrade kit was installed. The circuit breaker upgrade kit will be installed on circuit breaker 6-7 at the next availiable opportunity.
The preventive maintenance procedure for circuit breakers 8-15 and 6-7 will be revised to incorporate appropriate vendor advisory recommendations.
DNPS procedures were revised to require the securing of the DTPE Fans upon initiation of SGT.
The DTPE filter housing in-leakage has been repaired to correct air in leakage.
The SGT initiation logic will be changed to include the tripping of the DTPE Fans for both units.
The final corrective actions to prevent reoccurrence for the Emergency Diesel Generator output breaker will be described in a supplemental report scheduled to be submitted no later than October 30, 2004.
Dresden procedure DGA 12 was revised to require that affected transformer feed breaker control switches be placed in the pull-to-lock position during the restoration of normal off-site power sources, to preclude automatic operation of the breakers.
F.
Previous Occurrences
A review of Dresden Nuclear Power Station Licensee Event Reports (LERs) and operating experience identified the following LER.
Unit 3 LER 89-001-01 described a March 25, 1989, event in which an electrical fault in the 345 kilovolt circuit breaker 8-15 phase A internal ground capacitor and slow transfer of the 4 kv Bus 32 from transformer 32 to 31 caused a LOOP for Unit 3. The corrective actions included the removal of the internal ground capacitors from 345 kilovolt circuit breaker 8-15.
G.
Component Failure Data
I.T.E. Power Circuit Breaker, Model C Type GA