05000335/LER-2015-001
| St. Lucie Unit 1 | |
| Event date: | 08-09-2015 |
|---|---|
| Report date: | 10-07-2015 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3352015001R00 - NRC Website | |
Description of the Event
On August 9, 2015 with St. Lucie Unit 1 in Mode 1 at 100% reactor power, an unplanned reactor trip occurred. The trip occurred while Operators were performing a reactor protection system (RPS) logic matrix test. The logic matrix test involves opening and closing sets of reactor trip circuit breakers (TCBs). The team performing the test had worked through approximately half of the test before taking a break between test sections. It was at this point that the team progressed through a section without completing all of the steps in that section. The team did not implement acceptable placekeeping and unknowingly lost configuration control when they inadvertently left two TCBs open that should have been closed After the break when the test resumed, the test personnel did not perform a jobsite review. As they recommenced the test a reactor trip occurred when the next set of trip circuit breakers was opened.
Cause
The individuals performing the logic matrix test did not follow the test procedure, resulting in a loss of configuration control during the test.
Analysis of the Event
During the logic matrix testing, the individuals performing the role of the reader- doer did not restore two TCBs to their normal closed position, resulting in a loss of configuration control during the test. Had they maintained awareness of the configuration of the TCBs through proper verification techniques, then the two TCBs would have been closed prior to moving on to the next section of the logic matrix test procedure, and the reactor trip would not have occurred.
Safety Significance
This reactor trip event is reportable pursuant to 10 CFR 50.73(a)(2)(iv)(A) as an actuation of the RPS. This event had no significant safety consequence. All safety related systems functioned as designed. There were no safety systems actuations as a result of the trip.
With no complications and all systems responding as designed, the associated risk impact is considered very small. Given the response of the plant and the insignificant risk, the health and safety of the public were not affected by this event.
Corrective Actions
The corrective action listed below has been entered into the site corrective action program. Any changes to the action will be managed under the corrective action program.
1. To correct the problem, the procedure for performing the RPS logic matrix test is being revised to ensure configuration control of the TCBs is maintained through additional verification techniques.
Failed Component(s) None Manufacturer Combustion Engineering Inc.