ENS 47210
ENS Event | |
|---|---|
01:30 Aug 28, 2011 | |
| Title | Invalid Automatic Actuation of an Emergency Diesel Generator |
| Event Description | At 2130 [EDT] on August 27, 2011, an automatic actuation of the Unit 1 Train A emergency diesel generator occurred due to an actuation signal from the load sequencer. The Train A 4160 kV emergency bus transferred to the emergency diesel generator and all Train A emergency loads required for Mode 2 started and sequenced onto the Train A 4160 KV emergency bus except the 480 volt center breaker to the bus E1A2 that did not close. The load sequencer is designed upon the receipt of a safety injection actuation and/or loss of offsite power to provide a signal to strip loads from the 4160 kV emergency bus and then, in sequence, to re-energize the associated 480 volt buses and to load engineering safety feature components onto the 4160 kV and associated 480 volt emergency buses in a predetermined sequence. Per 10 CFR 50.72(b)(3)(iv)(B), additional emergency safety features loads that actuated were the Train A reactor containment fan coolers and auxiliary feedwater system.
Unit 1 remains critical at 100 percent power. No emergency core cooling system injection occurred into the reactor coolant system. The event occurred during surveillance testing when the Train A sequencer was taken from the AUTO Test position to the local position. It is not understood why the actuation occurred. In addition, it is not understood why the 480 volt load center breaker to the bus E1A2 did not close. The 480 volt bus E1A2 was re-energized at 2308 [EDT] on August 27, 2011. The Train A 4160 kV bus was restored to the offsite power source at 0150 [EDT] on August 28, 2011 and the Train A emergency diesel generator and engineering safety features loads were restored to their normal condition at 0201 [EDT] on August 28, 2011. With the Train A sequencer non-functional, the following Train A components are inoperable: 1) High Head Safety Injection Pump 1A; 2) Low Head Safety Injection Pump 1A; 3) Containment Spray Pump 1A; 4) RCFC [Reactor Containment Fan Cooler] Fan 11A; 5) RCFC Fan 12A; 6) Component Cooling Water Pump 1A; 7) Essential Cooling Water Pump 1A; 8) Aux Feedwater Pump 11; 9) Control Room/Elect. Aux Bldg HVAC; 10) Ess [Essential] Chiller 12A; and 11) ESF Diesel Generator 11. Although these components will not automatically start on a safety injection signal or loss of offsite power, these loads can be manually actuated. Engineered Safety Features Trains B and C remain operable. The licensee notified the NRC Resident Inspector.
The licensee is updating this event report to retract the originally reported valid specified system actuation and report it instead as a 60-day invalid specified system actuation report made by telephone: This update is a 60-day telephone notification in lieu of a written licensee event report being made under 10CFR50.73(a)(2)(iv)(A) and 10CFR50.73(a)(1). This event was originally reported per 50.72(b)(3)(iv)(A) as a valid actuation of the Unit 1 Train A emergency diesel generator and sequencing of Mode II (Loss of Offsite Power) emergency loads. The actuation occurred during surveillance testing when the Train A load sequencer was taken from the AUTO test position to the local position. Subsequent investigation has determined that the actuation occurred due to a faulty integrated chip within the sequencer's load sequence auto test module, and was not due to sensed or simulated plant conditions that would require a Mode II actuation. Unit 1 was at 100% power and no loss of offsite power occurred. The Train A equipment response to this invalid actuation is described in the original notification information provided on 08/28/2011. Additionally, the 10CFR50.72 Notification originally reported under Event Number 47210 is being retracted, since the actuation has been determined to be not valid. The licensee will notify the NRC Resident Inspector. R4DO (Whitten) notified. |
| Where | |
|---|---|
South Texas  Texas (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+2.13 h0.0888 days <br />0.0127 weeks <br />0.00292 months <br />) | |
| Opened: | Robert Lane 03:38 Aug 28, 2011 |
| NRC Officer: | Vince Klco |
| Last Updated: | Oct 13, 2011 |
| 47210 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 560942022-07-28T22:05:00028 July 2022 22:05:00
[Table view]10 CFR 50.73(a)(1), Submit an LER Invalid System Actuation ENS 472102011-08-28T01:30:00028 August 2011 01:30:00 10 CFR 50.73(a)(1), Submit an LER Invalid Automatic Actuation of an Emergency Diesel Generator ENS 418032005-05-17T21:02:00017 May 2005 21:02:00 10 CFR 50.73(a)(1), Submit an LER Invalid System Actuation - Auxiliary Feedwater Pump Started During Surveillance 2022-07-28T22:05:00 | |