05000443/LER-2009-001
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | 10-01-2009 |
|---|---|
| Report date: | 11-30-2009 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4432009001R00 - NRC Website | |
I. Description of Event
On October 1, 2009 at approximately 2241 EDT with the plant in Mode 4 at approximately 260 degrees, actuation of the reactor protection system (RPS) [JC] resulted from low water levels in steam generators (SG) [AB, SG] A and C. Inadequate monitoring and control of SG levels while performing a plant cool down resulted in SG levels decreasing below the reactor trip setpoint of 20% narrow range level, which caused an actuation of the RPS. This valid actuation of the RPS did not actuate any plant components because the reactor trip breakers [AA, 52] were already open and the emergency feedwater system [BA] was removed from service.
II. Cause of Event
The control room operator's failure to adequately monitor and control SG levels during a plant cooldown was the direct cause of this event. The root cause was attributed to the Operations Department's liberal expectations and standards for implementation of certain procedures that direct major plant evolutions, which led to the operating crew's failure to assess potential risks associated with performing a plant cooldown without placing the residual heat removal (RHR) [BP] system in service. The Operations Department's practice when implementing major plant evolution procedures was to perform procedure steps out of sequence. In this event, performing procedure steps out of sequence led the operators to make adjustments to SG levels, which otherwise would not have been required. The RPS actuation on low SG levels occurred while making the SG level adjustments.
III. Analysis of Event
At the time of the event, the plant was in mode 4 at approximately 260 degrees with both trains of the RHR system out of service. Although the plant cooldown procedure directs starting the RHR system when reactor coolant system (RCS) temperature is less than 350 degrees, the RHR system had not yet been placed in operation at 260 degrees. The delay in starting the RHR system resulted from the need to evaluate a recently identified indication of a flaw in the train-A RHR piping and to remove a gas void in the train-B RHR suction piping. As a result, the operators postponed performing the step to place the RHR system in operation. Because the RHR system was not in operation, the operators also postponed a subsequent procedure step to stop one of the remaining two operating reactor coolant pumps (RCP) [AB, P]. The plant cooldown from 350 degrees to 260 degrees continued by operating reactor coolant pumps A and C and steaming the associated SGs. As RCS temperature approached 250 degrees, the operators reduced SG levels to 35% narrow range in accordance with the plant procedure.
In preparing to shut down one RCP, the operators took action to increase SG levels to accommodate any level decrease that might accompany stopping the RCP. During the attempt to raise SG levels, the control room operator failed to adequately monitor SG levels and control feedwater flow, resulting in SG levels decreasing to less than 8% before they were recovered.
This event resulted in a valid actuation of the RPS and met the reporting criterion of 10CFR50.72(b)(3)(iv)(A). An eight-hour report (event # 45403) was made to the NRC at 0418 on October 2, 2009. This event is of regulatory significance because it resulted in the actuation of a system provided to mitigate the consequences of an accident.
This event had no adverse impact on the plant or on the health and safety of the public. No equipment was actuated following actuation of the RPS and no consequences resulted from the event. No inoperable structures, systems, or components contributed to this event. This condition did not involve a Safety System Functional Failure.
IV. Corrective Action The planned corrective actions for this event include: (1) remediation for the control room operator who failed to adequately monitor and control SG levels, (2) revising the Operations department's expectations document to address procedure compliance with major plant evolution procedures, (3) discussing in operator training procedure compliance expectations with a review of this event, and (4) revising the major plant evolution procedures so that the procedure strategy is maintained by specifically identifying steps that may be performed in parallel or out of sequence.
V. Additional Information
The Energy Industry Identification System (EllS) codes are included in this LER in the following format: [EllS system identifier, EllS component identifier].
VI. Similar Events A review of LERs for the last five years found no other occurrences of an engineered safety features system actuation as a result of inappropriate procedure implementation.