05000397/LER-2013-004
| Columbia Generating Station | |
| Event date: | |
|---|---|
| Report date: | |
| 3972013004R01 - NRC Website | |
PLANT CONDITIONS
The event was discovered June 4, 2013 when a logic system functional test (LSFT) of the Suppression Pool Remote Transfer Switch [JS] failed. The plant was in Mode 5 during refueling outage R21 with the reactor mode switch in Refuel.
EVENT DESCRIPTION
On 6/04/2013, during performance of surveillance procedure on the control power transfer switch [JS] located in the Remote Shutdown Panel, a step to verify no continuity (contacts open) for the transfer switch for the suppression pool spray valve RHR-V-27B [ISV] failed. Failure of the surveillance was attributed to a jumper [57] Installed (as-found) in 480V Motor Control Center [MCC] starter controls contained in the new bucket. The Jumper had been left in place since refueling outage R20 when the Spectrum bucket (breaker) was installed on May 16, 2011. The transfer switch was, therefore, inoperable since the Jumper was left in place, because Surveillance Requirement 3.3.3.2.4 under Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.3.3.2, The Remote Shutdown System Functions Shall Be Operable, would not have been met when in Modes 1 or 2.
IMMEDIATE CORRECTIVE ACTION
The Jumper was removed and the loosened terminals were torqued to restore bucket to design configuration.
CAUSE
The Cause Evaluation identified preliminary apparent causes of this event as follows: (1) a lack of a standard for Work Order instructions involving removal and installation of Jumpers, which requires personnel to rely on experience and skill of the craft for the proper way of executing and documenting required modifications; and (2) inadequate decision making resulting in the use of a post maintenance testing procedure after the installation of the Spectrum bucket in May 2011 that did not adequately prove operability.
FURTHER CORRECTIVE ACTION
Procedures will be revised to provide additional level of detail for work order stops involving determination and termination of wires, cables and Jumpers.
Additional corrective actions are being Investigated that may result in additional proposed corrective measures. A supplement to this Licensee Event Report will be submitted if the final corrective action plan is substantively different than that included in this form.
ASSESSMENT OF SAFETY CONSEQUENCES
The remote transfer switch Is located at the Remote Shutdown Panel. The switch transfers control of the Division 2 suppression pool spray valve from the Main Control Room to the Remote Shutdown Panel and vice versa. The suppression pool spray valve is used to provide cooling to the wetwell portion of the primary containment as a means to control containment pressure during an accident.
The jumpered terminals in the remote shutdown transfer switch did not impact the operation of the suppression pool spray valve from the Main Control Room.
With the jumper left in place the operation of the suppression pool spray valve could be impacted from the Remote Shutdown Panel because of loss of starter control power for valve RHR-V-218 under some abnormal scenarios (i.e., fire in the Main Control Room), which would require the replacement of a blown fuse prior to being able to operate the valve from the Remote ShutdOwn Panel. However, the normal position for this valve is closed and it would not normally be 26158 R5 operated from the Remote Shutdown Panel in the event of a fire in the Control Room. Therefore the safety significance of this failure is low.
SIMILAR EVENTS
There are several documented conditions with similar circumstances involving improper removal or installation of jumpers.
However, they were due to improper placement or removal of jumpers and did not Involve jumpers being left in for an extended period of time.
ENERGY INDUSTRY IDENTIFICATION SYSTEM (ells) INFORMATION CODES * * * * SUPPLEMENTAL REPORT Ucensee Event Report (LER) 2013-004.00 was originally submitted pursuant to the requirements of 10 CFR 50.73(a)(2)(1)(B) and 50.73(a)(2)(v)(D). This supplement withdraws selection of the latter reportability criterion, 50.73(a)(2)(v)(D) because it is not applicable to this event. On completion of the evaluation and further review of the Engineering assessment it has been determined that the jumper that was left In place In the breaker of the RHR-V-27B valve would not have prevented fulfillment of a safety function that Is needed to shut down the reactor and maintain It in a safe shutdown condition, or to mitigate the consequences of an accident.
Review of the Engineering assessment of this event indicates that the presence of the jumper in the breaker for the RHR- V-278 valve would not have impacted the ability to operate the valve from the Control Room. Therefore operation of RHR-V-27B for heat dissipation in the suppression pool in the event of an accident (i.e., LOCA) would not have been prevented by the jumper. Thus the operation of the RHR-V-278 valve needed to mitigate the consequences of an accident was not impacted.
An assessment of the ability to safely shutdown the reactor and maintain it in a shutdown condition and the ability to remove residual heat from the core was completed and determined that there was no impact on either of these functions.
This is based on the fact that although the installation of the jumper could have caused a loss of control power to the valve when it is transferred to the Remote Shutdown Panel, the loss of power to RHR-V-27B would not impact its safety function because the valve is normally closed and would fail as is. Additionally the Post Fire Safe Shutdown (PFSS) Analysis establishes as a basis that all plant safe shutdown equipment is functional and that there are no tests or maintenance activities going on at the time of fire Ignition. Thus It is assumed that the RHR-V-27B valve would be closed for a fire that required Main Control Room evacuation and would fail in that position If the transfer to the remote shutdown panel would have caused the fuses to blow. Therefore, the ability to make up coolant to the reactor using Division 2 RHR or to go into shutdown cooling is not impacted.
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