05000425/LER-2015-002
| Vogtle Electric Generating Plant - Unit 2 | |
| Event date: | 03-14-2015 |
|---|---|
| Report date: | 5-13-2015 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(B), System Actuation 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| Initial Reporting | |
| ENS 43016 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation |
| 4252015002R00 - NRC Website | |
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A. REQUIREMENT FOR REPORT
This report is required per 10CFR 50.73(a)(2)(iv)(A) due to actuation of a system listed in 10CFR 50.73(a)(2)(iv)(B) in that a valid AFW actuation signal was received.
B. UNIT STATUS AT TIME OF EVENT
Mode 3, 0 percent rated thermal power
C. DESCRIPTION OF EVENT
On March 14, 2015 at 1207 EDT, Unit 2 was being stabilized in mode 3 following an unplanned reactor trip and safety injection when a valid actuation signal was received on B-train AFW. At the time, the Operations crew was performing steps in a unit operating procedure (UOP) to disable an AFW signal for "trip of both main feed pumps." During the steps to disable the AFW actuation logic, the logic was disabled then re-enabled causing an AFW actuation to be processed for B-train AFW system. The Steam Generator Level Control (SGWL) operator immediately identified the issue and throttled the discharge valves back to their original position to maintain SG levels stable.
Prior to disabling the AFW actuation signal, the UOP directed the crew to perform a subsection of a different procedure to test the annunciator associated with AFW actuation. It was unnecessary to perform the full annunciator test procedure since it was an 18-month surveillance and only a specific subsection was required. Prior to performing the B-train annunciator test, the crew did not review a precaution in the test procedure that warned the user to ensure one main feedwater pump is reset so that no AFW actuation signals would be generated. Instead, the crew's actions were driven by an assumption the plant was already in the correct configuration to proceed.
Since both main feedwater pumps were in a tripped condition, plant conditions for performing the test were not satisfied, resulting in a re-actuation of the AFW system during performance of the test procedure. The SGWL operator responded by throttling the AFW discharge valves to their previous position with no significant impact on steam generator water levels.
D. CAUSE OF EVENT
The AFW actuation occurred as a result of human error. The apparent cause of this event is deviation from standards by the operating crew to review the precautions and limitations of the test procedure, as required. Since the unit was in a post-trip recovery condition instead of the expected conditions associated with a normal unit shutdown, the initial conditions of the test procedure were not established and not recognized by the operating crew and performance of the test procedure resulted in the B-train AFW actuation.
E. SAFETY ASSESSMENT
The AFW actuation occurred as a result of human error and was not caused by equipment malfunction. There were no actual safety consequences associated with this event. The unit was already in shutdown conditions when the actuation occurred. Decay heat removal was maintained throughout the event. This event had no consequence to the safety and health of the public and is considered to be of very low safety significance.
F. CORRECTIVE ACTION
The immediate corrective action was restoration of the AFW discharge valves to their throttled position. Additional corrective actions include shift briefings on the event, supervisor challenge to ensure standards and behaviors are the same for outage and online work, development of operating experience, and training on the event occurrence to emphasize standards and lessons learned.
G. ADDITIONAL INFORMATION
1. Failed Components:
None — No components failed as a result of actuation.
2. Previous Similar Events:
Indian Point Unit 2 (Event Number 43016) - Auxiliary Feedwater Pump Automatic Start 3. Energy Industry Identification System Code:
[PWR/4] — Westinghouse Pressurized Water Reactor [BA] — Auxiliary/Emergency Feedwater System [JE] — Engineered Safety Features Actuation System