05000352/LER-2012-006
| Limerick Generating Station, Unit 1 | |
| Event date: | 07-19-2012 |
|---|---|
| Report date: | 09-17-2012 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| Initial Reporting | |
| ENS 48121 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation |
| 3522012006R00 - NRC Website | |
Unit Conditions Prior to the Event Unit 1 was in Operational Condition (OPCON) 4 (Cold Shutdown) with reactor coolant temperature at approximately 131 degrees Fahrenheit and reactor pressure at approximately zero psig. A reactor cooldown was in progress to support an outage. The outage was caused by a failure of 124A load center transformer. There were no structures, systems or components out of service that contributed to this event.
Description of the Event
On Wednesday, July 19, 2012, Limerick Unit 1 was in an outage. The "Pre-control Rod Withdrawal Check and CRD Exercise OPCONs 3,4 With No Core Alterations" surveillance test (ST-6-047-471-1) was in progress to establish the conditions needed to support control rod exercising.
Attachment 2 of the test had been completed by the Surveillance Test Coordinator (STC) to provide the surveillance test status of the source range monitor (SRM) and intermediate range monitor (IRM) nuclear instrumentation (NI) (EIIS:IG) systems. The STC made an error when completing Attachment 2 which indicated that two required surveillance tests were in surveillance when in fact they had exceeded their due date.
At 1509 hours0.0175 days <br />0.419 hours <br />0.0025 weeks <br />5.741745e-4 months <br />, the mode switch (EIIS:HS) was placed in the "Refuel" position to support planned control rod exercising as directed by the test. A licensed operator then identified that the required surveillance tests had not been performed. At 1537 hours0.0178 days <br />0.427 hours <br />0.00254 weeks <br />5.848285e-4 months <br />, the mode switch was returned to the "Shutdown" position which resulted in a valid manual actuation of the reactor protection system (RPS) (EIIS:JC).
An 8-hour NRC ENS notification was required by 10CFR50.72(b)(3)(iv)(A) for a valid actuation of RPS. The ENS notification (#48121) was completed on Thursday July 19, 2012, at 2156 EDT. This event involved a manual actuation of RPS. Therefore, this LER is being submitted pursuant to the requirements of 10CFR50.73(a)(2)(iv)(A).
Analysis of the Event
There was no actual safety consequence associated with this event.
The potential safety consequences of this event were minimal. The reactor was in cold shutdown with all control rods inserted at the time of the event.
The STC provided an incorrect status of the NI surveillance tests needed for control rod exercising when the "Pre-control Rod Withdrawal Check and CRD Exercise OPCONs 3,4 With No Core Alterations" surveillance test Attachment 2 was completed. Tests that are verified to be in surveillance are to be circled in Attachment B. The error occurred when two expired tests were circled by the STC.
Cause of the Event
The cause of the event was a personnel error caused by a test weakness. The "Pre-control Rod Withdrawal Check and CRD Exercise OPCONs 3,4 With No Core Alterations" surveillance test does not have verification steps to ensure that the STC input is accurate.
Corrective Action Planned The "Pre-control Rod Withdrawal Check and CRD Exercise OPCONs 3,4 With No Core Alterations" surveillance test Attachment 2 will be revised to add an additional Work Management signoff for a peer check of the STC input. The notes and body of Attachment 2 will be revised to improve human factoring.
Previous Similar Occurrences There were no similar occurrences of valid manual actuation of the reactor protection system due to surveillance test status control errors in the previous three years.