ENS 41728
ENS Event | |
|---|---|
17:50 May 24, 2005 | |
| Title | Unanalyzed Condition Involving Emergency Backup Power Generators |
| Event Description | Event: On 5-19-05, Oconee discovered that an electrical contactor had failed at Keowee Hydro Station. This contactor normally can provide auxiliary power from one Keowee Hydro Unit (KHU) to cooling fans on the Keowee Main Transformer, which is part of the Overhead power path (one train of emergency power to the three Oconee units). At the time, power to the cooling fans was being provided by an alternate power source. A problem report (PIP) was written and an Operability Assessment concluded that the Overhead power path was fully operable. On 5-24-05 at 1350 hours0.0156 days <br />0.375 hours <br />0.00223 weeks <br />5.13675e-4 months <br />, it was recognized that the alternate power source supplying the cooling fans was supplied from the auxiliary power bus associated with the KHU then aligned to the Underground power path (the redundant train of emergency power to the three Oconee units).
It was recognized that this alignment presented a single failure vulnerability in that loss of the auxiliary power bus for the KHU aligned to the Underground path could also result in loss of Main Transformer cooling on the Overhead power path. As a result, Operations declared entry at 1350 hours0.0156 days <br />0.375 hours <br />0.00223 weeks <br />5.13675e-4 months <br /> into Technical Specification (TS) 3.8.1 condition C for the Overhead power path being inoperable (a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed completion time). A review of available information indicates that the electrical contactor actually failed on or before 5-2-05. Therefore the period of vulnerability to this potential single failure was approximately 22 days. This condition is being reported as an unanalyzed condition per guidance in NUREG 1022 section 3.2.4. Initial Safety Significance: If the postulated single failure occurred during a design basis event, it is expected that, without credit for Operator intervention, both KHUs would fail, but the failure is not expected until a minimum of one hour after the loss of auxiliary power. During this time Operations would have been able to realign the KHU with auxiliary power to the Underground path and/or to have started and aligned a combustion turbine at Lee Steam Station. Therefore, the condition being reported is not expected to result in a loss of safety function. Corrective Action(s): The immediate corrective action was to realign the Keowee units to the opposite power paths. This aligned the KHU capable of supplying power to the Main Transformer cooling fans to the Overhead path. The KHU associated with the failed contactor was aligned to the Underground path. The TS condition was exited at 1540 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.8597e-4 months <br /> when this realignment was complete. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Oconee  South Carolina (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+2.17 h0.0904 days <br />0.0129 weeks <br />0.00297 months <br />) | |
| Opened: | Randy Todd 20:00 May 24, 2005 |
| NRC Officer: | Wesley Held |
| Last Updated: | May 24, 2005 |
| 41728 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 506402014-11-25T17:12:00025 November 2014 17:12:00
[Table view]10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Deficiency in Methodology Used for Emergency Core Cooling System Performance Requirements ENS 499682014-03-28T17:00:00028 March 2014 17:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Keowee Emergency Power System 13.8Kv Cable May Not Comply with Licensing Basis ENS 490682013-05-24T18:00:00024 May 2013 18:00:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Heating Ventilation and Air Condition System Inadequately Analyzed for Heat Load ENS 478102012-04-06T02:38:0006 April 2012 02:38:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Standby Shutdown Facility (Ssf) Not Analyzed for All Operating Conditions ENS 423182006-02-07T01:50:0007 February 2006 01:50:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - Non-Conforming Fire Barriers ENS 418502005-07-18T15:30:00018 July 2005 15:30:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Electrical Alignment Results in Single Failure Vulnerability ENS 417282005-05-24T17:50:00024 May 2005 17:50:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Involving Emergency Backup Power Generators ENS 407242004-05-04T20:55:0004 May 2004 20:55:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition and Potential Loss of Containment Safety Function ENS 401922003-09-23T08:00:00023 September 2003 08:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Potential Rcs Leakage at Oconee 1 2014-03-28T17:00:00 | |