05000424/LER-2012-004
| Vogtle Electric Generating Plant - Unit 1 | |
| Event date: | 10-05-2012 |
|---|---|
| Report date: | 12-3-2012 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation |
| 4242012004R00 - NRC Website | |
A, REQUIREMENT FOR REPORT Since this actuation was not part of a pre-planned test or evolution this report is required per 10 CFR50.73(a)(2)(iv) due to automatic actuation of the Auxiliary Feedwater System to a valid actuation signal.
B. UNIT STATUS AT TIME OF EVENT
During the period of the event the unit was in Mode 5. Other than described herein, there was no other inoperable equipment that contributed to the event.
C. DESCRIPTION OF EVENT
On October 5, 2012 with Unit 1 in Mode 5 and the residual heat removal (RHR) system in service for reactor coolant system temperature control, activities were in progress in preparation for Mode 4 entry, One of the activities involved restoration of the steam generator level RPS/ESFAS instrumentation from a bypassed condition to normal alignment. During the restoration a steam generator lo-lo level actuation was received and the motor-driven AFW pumps started and two turbine-driven AFW discharge valves stroked full open. Due to the system alignment no water was injected into the steam generators.
During the unit shutdown for refueling outage 1R17, the AFW system had been properly removed from service as required by the controlling procedure. During the refueling outage safety system testing was performed necessitating re-alignment of the system to support testing, At the conclusion of the testing, the AFW system was not restored to the procedurally required configuration. Prior to restoring steam generator level instrumentation, the crew identified that actual steam generator level was below the actuation setpoint but assumed the system was in the proper alignment and did not recognize the AFW system was not in the procedurally required configuration to prevent inadvertent actuations.
D. CAUSE OF EVENT
Upon returning steam generator level instrumentation from a bypassed condition to a normal alignment the effect on the AFW system was not fully evaluated.
E. SAFETY ASSESSMENT
The automatic actuation occurred in a Mode in which the system is not required to perform a credited safety function. At the time of the event, the Residual Heat Removal System was in service providing reactor coolant system temperature control.
NRC FORM 3138A (10-2(110)
F. CORRECTIVE ACTION
An operating order was issued to maintain the AFW pumps in a disabled condition while in Mode 5 unless otherwise procedurally directed. in addition, shift supervisor permission and verification from a second SRO is required prior to restoring instrumentation from a bypassed condition to a normal alignment.
Procedural revisions are in progress to prevent recurrence and a training gap/needs analysis will be performed,
G. ADDITIONAL INFORMATION
1) Failed Components:
None 2) Previous Similar Events:
Topical Report TR 4-39, Review of Auxiliary Feedwater System Events 3) Energy Industry Identification System Code:
[BA] - Auxiliary / Emergency Feedwater System (PWR)