05000331/LER-2014-005
| Duane Arnold Energy Center | |
| Event date: | 06-30-2014 |
|---|---|
| Report date: | 08-29-2014 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation |
| Initial Reporting | |
| ENS 50246 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation |
| 3312014005R00 - NRC Website | |
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I. Description of Event:
On June 30, 2014, at 1913, while operating at 98% power, a grid disturbance resulted in an automatic start of both of the site's Emergency Diesel Generators (EDGs) (IEE Code EK). Neither EDG loaded onto its respective essential bus. The cause of the EDG starts was a momentary (approximately 13 cycles) dip in essential bus voltage to 62%. A review of the system design showed that since the EDGs started on an automatic start signal of essential bus voltage less than 65% for greater than 12 cycles, the EDGs operated as designed. Both EDGs were secured and returned to their normal standby readiness condition at 2116 on June 30, 2014.
There were no radiological releases associated with this event. There were no other structures, systems or components inoperable at the start of this event that contributed to the event.
II. Assessment of Safety Consequences:
The automatic starting of the EDGs in response to a short-duration under voltage condition had no personnel or radiological safety significance. Since the diesel generators were capable of fulfilling their safety function throughout this, there is no nuclear safety significance.
This event resulted in an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> reportable event. The Resident Inspector was notified, and Event Notification Number 50246 was made pursuant to 10 CFR 50.72(b)(3)(iv)(A) due to a valid system actuation.
This event did not result in a safety system functional failure. There were no automatically or manually initiated safety system responses.
III. Cause of Event:
An Apparent Cause Evaluation was completed. The cause of the EDG starts was a momentary (approximately 13 cycles) dip in essential bus voltage to 62%. A review of the system design showed that since the EDGs started on an automatic start signal of essential bus voltage less than 65% for greater than 12 cycles, the EDGs operated as designed.
IV. Corrective Actions:
Both EDGs were secured and returned to their normal standby readiness condition at 2116 on June 30, 2014.
Duane Arnold Energy Center 05000-331
V. Additional Information:
Previous Similar Occurrences:
A review of DAEC Licensee Event Reports from the past 5 years identified one previous similar occurrence. LER 2010-001 documented an automatic start of the "A" EDG on a valid undervoltage condition; the EDG did not load to its respective essential bus.
EIIS System and Component Codes:
EK — Emergency Onsite Power Supply System Reporting Requirements:
This event is being reported due to a valid system actuation, 10CFR50.73(a)(2)(iv).