At 1537
CST on February 18th, 2017, while the plant was in MODE 5 for a scheduled refueling outage, the main control room experienced a loss of Control Building chilled water and the associated ventilation systems while attempting to alternate divisions for testing. An equipment malfunction in a breaker supplying a Main Control Room air handling unit caused a loss of both divisions of Control Room and Control Building chilled water systems and associated ventilation systems until 1737
CST. During the period between 1537 and 1737, neither division of Control Building chilled water was able to perform the support function for cooling Division 1 and 2
AC and
DC power distribution systems or the support function for the Division 1 and 2 Control Room Fresh Air systems.
Shutdown Cooling remained in service throughout this event. There were no apparent effects on any plant equipment from the loss of chill water and ventilation.
The Division 1 Control Building chill water and ventilation system was returned to service at 1737 on February 18, 2017.
Actions were initiated to terminate the OPDRV [operations with potential to drain the reactor vessel] that was in progress at the time of the event by installing the reactor recirculation pump seal. As a conservative measure, actions were initiated to set containment and containment was set at 2145.
Troubleshooting and analysis is ongoing to confirm and correct the problem which caused the loss of the Control Building chill water and ventilation system.
This condition is being reported in accordance with 10 CFR 50.72(b)(3)(v)(B).
The NRC Senior Resident Inspector has been notified.
