During the performance of Service Water Essential header swap, SWN-6 (Supply to Turbine Building Oil Coolers) valve stem became disconnected from its gear box at 85% open and could not be operated. Therefore, the non-essential service water system was inoperable. LCO 3.0.3 was entered at 0930 (EDT) with required actions to be in Mode 3 in 7 hours, Mode 4 in 13 hours and Mode 5 in 37 hours. Repair efforts were successful at shutting SWN-6, and LCO 3.0.3 was exited at 1305 (EDT) before adding any negative reactivity in support of shutdown. ('TS Required S/D' box not checked.)
This condition constituted a loss of safety function which requires an 8 hour report (in accordance with) IAW 50.72(b)(3)(v)(B): Without the ability to close SWN-6, the non-seismic portion of the conventional Service Water System could not be isolated as required in the event of either a seismic event or as required in the EOPs. The nonessential service water system is required to support the recirculation phase post (Design Basis Accident) DBA for accident mitigation.
The licensee notified the NRC Resident Inspector and the State of New York.
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