ENS 41524
ENS Event | |
|---|---|
15:30 Mar 24, 2005 | |
| Title | Minimum Switchyard Voltage Requirements Not Met |
| Event Description | The following information was obtained from the licensee via facsimile (licensee text in quotes):
Minimum Switchyard Voltage Requirements Not Met On March 24, 2005, at 0930 hours0.0108 days <br />0.258 hours <br />0.00154 weeks <br />3.53865e-4 months <br />, Quad Cities was notified that the switchyard voltage was below that required to ensure that offsite power would remain available following a design basis accident. Both sources of off-site power were declared inoperable. The appropriate Technical Specification required actions were taken for both units. The ability of the Emergency Diesel Generators to perform their design function is not affected by this condition. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of a safety function given the predicted post-LOCA switchyard voltage. A preliminary engineering assessment indicates that one source of offsite power was available. Additional confirmatory reviews are being performed to determine if the safety function was preserved. At this time, grid/switchyard voltage has been restored. Minimum switchyard voltage required is 348.4 KV. The analyzed minimum voltage which prompted notification to the NRC was 347.5 KV. Switchyard voltage at the time of this report was ~359 KV. The licensee has notified the NRC Resident Inspector.
The purpose of this report is to retract the following ENS reports: 1) ENS # 41524 on March 24, 2005; 2) ENS # 41562 on April 4, 2005; and 3) ENS # 41587 on April 11, 2005. These reports were made following notification to Quad Cities that the switchyard voltage was below the required value necessary to ensure that offsite power would remain available following a design basis accident. For each event, both sources of offsite power were declared inoperable, the appropriate Technical Specification required actions were taken for both units, and an ENS notification was made for a condition that could have prevented fulfillment of a safety function. The events occurred when Unit 1 was in a refueling outage and Unit 2 was operating at 85% power. Subsequent Engineering analysis has determined that with a unit shutdown, and the large 4 Kv loads on that unit not running, the required minimum post-accident switchyard voltage is reduced to 339.3 kV (for the shutdown unit). Given the new minimum post-accident switchyard voltage, it was confirmed that there was a source of off-site power available to the Station. Specifically for all three events, the projected post-accident switchyard voltage (which ranged between 343 kV to 347.5 kV) was higher than the required minimum post-accident switchyard voltage (339.3 kV) for the shutdown unit. As a result, there was no condition present that could have prevented fulfillment of a safety function, and thus these events are not reportable. The licensee notified the NRC Resident Inspector. Notified R3 DO (J. Madera) |
| Where | |
|---|---|
Quad Cities  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+2.33 h0.0971 days <br />0.0139 weeks <br />0.00319 months <br />) | |
| Opened: | David Bowman 17:50 Mar 24, 2005 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Apr 13, 2005 |
| 41524 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (85 %) |
| After | Power Operation (85 %) |