ENS 41766

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v t e ENS Event
18:10 Jun 11, 2005
Title	Minimum Switchyard Voltage Requirements Not Met
Event Description	At 1310 on June 11, 2005 Quad Cities Station was notified that the 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 356 Kv. The required minimum post-accident switchyard voltage for current conditions is 352.9 Kv for U-1 and 351 Kv for U-2, while the projected post-accident voltage which prompted this notification is 347.4 Kv. This notification is similar to the condition reported on March 24, 2005 (EN#41524), April 4, 2005 (EN#41562) and April 11, 2005 (EN#41587). Both Units entered T.S. 3.8.1 which requires verification of EDG operability (completed) and continued monitoring of line voltages with restoration of at least one offsite-line to the required minimum within 24-hours. The licensee informed the NRC Resident Inspector. * * UPDATE 1610 EDT ON 6/11/05 FROM RON RUSTICK TO S. SANDIN * * * At 1505 CDT both Units exited T.S. 3.8.1 when projected post-accident line voltage reached 353.8 kV. Notified R3DO (Lara). * * RETRACTION FROM J. COX TO W. GOTT 1906 ET 08/09/05 * * * The purpose of this report is to retract ENS#41652 (April 29, 2005), ENS 41766 (June 11, 2005), and ENS#41801 (June 27, 2005). The reports were made following notification that the switchyard predicted 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 the units, and an ENS notification was made for a condition that could have prevented the fulfillment of a safety function. Each Quad Cities unit has two sources of off-site power. For a specific unit, one source is from the switchyard through the unit's Reserve Auxiliary Transformer (RAT) and the second source is from the switchyard through the opposite unit's RAT. Following further analysis of the loading on the RATs during an accident, it was determined that only one source of offsite power to each unit should have been considered inoperable. The analysis determined that because the RAT for the non-accident unit (i.e., the offsite source supplied through the opposite unit) would be carrying a much smaller load, it would not be subject to a degraded voltage condition and resultant isolation from the grid. Therefore, an accident on one unit would not affect the operability of the source of offsite power supplied through the opposite unit's RAT. As a result, only the source of offsite power supplied through the unit's RAT was inoperable. With one source of offsite power available at all times, there was no condition present that could have prevented fulfillment of a safety function, and therefore, these events are not reportable. The licensee notified the NRC Resident Inspector. Notified R3 DO (R. Lanksbury)

ENS 41766 +/- *RETRACTED*
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:+-2.67 h-0.111 days <br />-0.0159 weeks <br />-0.00366 months <br />)
Opened:	Ron Rustick 15:30 Jun 11, 2005
NRC Officer:	Steve Sandin
Last Updated:	Aug 9, 2005
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v • d • e

v t e Emergency Notification System
Quad Cities with 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
WEEKMONTHYEAR		Oprm Count Setpoint Discrepancy 2025-09-05T06:30:00 [Table view]
[ENS list for Quad Cities]

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