ENS 41587
ENS Event | |
|---|---|
18:40 Apr 11, 2005 | |
| Title | Minimum Switchyard Voltage Requirements Not Met |
| Event Description | At 1240 on April 11, 2005 Quad Cities Station was notified calculated post-LOCA switchyard voltage is below the minimum acceptable value required to ensure offsite power will remain available following a design basis accident. The appropriate Technical Specification Actions have been taken for both Units. The ability of the Emergency Diesel Generators to fulfill their design function is not affected by this condition. This event is being reported in accordance with 10CFR50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of a safety function given the predicted post-LOCA switchyard voltage.
Actual Switchyard voltage at the time of this notification is 361 Kv. The required minimum post-accident switchyard voltage is 348.4 Kv, while the projected post-accident voltage which prompted this notification is 346.3 Kv. This notification is similar to the condition reported on March 24, 2005 (EN#41524) and April 4, 2005 (EN#41562). 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:+-3.02 h-0.126 days <br />-0.018 weeks <br />-0.00414 months <br />) | |
| Opened: | Dave Bowman 15:39 Apr 11, 2005 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Apr 13, 2005 |
| 41587 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (85 %) |
| After | Power Operation (85 %) |