05000425/LER-2014-003
| Vogtle Electric Generating Plant | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4252014003R00 - NRC Website | |
Reported lessons learned are incorporated into the Icensirg process and fed back to industry.
Send comments regarding burden estimate to the FOIA, Privacy and Information Colocbons Branch (T-6 F63), U.S. Nuclear Regulatory Commission, Washington. CC 20555-0001, or by Internet email to Intociallects.Resowceeruc.gov, and to the Desk Officer, Office of Information and Regvkatory Affairs. NEOB-10202. (315041104), Office of Management and Budget Washington, DC 20503. If a means used to impose an attenuation collection does not display a currerrly valid OMB control minter, the NRC may not conduct or sponsor, and a person Is not required to respond to, the idermation collection.
A. REQUIREMENT FOR REPORT
This report is required per 10CFR 50.73(a)(2)(iv)(A) due to an unplanned manual actuation of the Reactor Protection System (RPS).
B. UNIT STATUS AT TIME OF EVENT
Mode 2, 1 percent power
C. DESCRIPTION OF EVENT
While performing Low Power Physics Testing after refueling outage 2R17, operators attempted to stabilize reactor power by inserting Control Rod Control Bank D, however Control Bank A inserted instead. When Control Bank A stepped in after confirming the rods were in manual operation, operators manually tripped Unit 2. All control rods fully inserted into the core and the plant was stabilized in Mode 3. There were no complications during the trip as all systems responded as designed and decay heat was discharged to the condenser.
Upon further investigation it was determined that the Rod Bank Overlap unit was set up incorrectly.
This caused the control rods to insert out-of-sequence. The +1 pushbutton should be used to toggle bank overlap unit to the proper setting when the control rods are set up following an outage.
Instead, the -1 pushbutton was used which caused the Rod Bank Overlap unit to insert the incorrect bank of control rods when demanded.
D. CAUSE OF THE EVENT
The cause of the event was incorrect setup of the Rod Bank Overlap unit, which resulted in the control rods inserting out of sequence. Human error in conjunction with procedural weakness was the cause of the incorrect setup of the Rod Bank Overlap unit.
E. SAFETY ASSESSMENT
When the reactor was tripped, all control rods fully inserted into the core. At the time, Reactor Coolant System heat removal via auxiliary feedwater was in operation and continued. Decay heat was discharged to the condenser and Unit 2 was stabilized in Mode 3. The plant responded as designed and there were no complications. There were no adverse effects on plant safety or the health and safety of the public. Therefore, this event is of very low safety significance.
F. CORRECTIVE ACTION
A Human Performance Review Board was conducted and crew stand downs were held to emphasize the expectation and importance of following procedures as written and the importance of maintaining proper supervisory oversight. In addition, the procedure used to control Bank Overlap unit setup is being revised to strengthen the information about the Rod Bank Overlap Unit and the -1 and +1 pushbuttons. Plant labeling will be installed to provide improved direction to the operators on the use of the pushbuttons and direct them to the procedure for additional information. This event will be included in Licensed Operator training.
G. ADDITIONAL INFORMATION
1) Failed Components:
None 2) Previous Similar Events:
None found 3) Energy Industry Identification System Code:
[JC] — Reactor Protection System