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On August 25, 2016, Engineering staff were … On August 25, 2016, Engineering staff were reviewing a proposed modification to install additional internal flooding protection for the Intake Building staircase down to the Raw Water Pump vault. Fort Calhoun Station determined that the existing Intake Building internal flooding and tornado-borne missile analyses did not sufficiently account for the potential of tornado-borne missiles striking Fire Protection piping in the Intake Building. A tornado-borne missile strike could potentially cause a double-ended rupture of Fire Protection piping in the vicinity of the stairwell down to the Raw Water Pump vault, which could cause flooding and subsequent failure of all four Raw Water Pump motors more quickly than bounded by the Engineering Analysis. The Engineering Analysis uses a postulated crack from a Moderate Energy Line Break per USNRC Branch Technical Position MEB 3-1, vice postulating a double ended pipe rupture. The resulting flow rate from this postulated crack is less than that possible from a tornado-borne missile strike. </br>This condition creates a potential loss of safety function from the Fort Calhoun Station Raw Water System (ultimate heat sink). All four Raw Water Pump motors could potentially become inoperable from flooding caused by a tornado-borne missile impacting the Fire Protection System Piping near the Raw Water vault stairwell prior to operator action to secure both Fire Pumps. </br>This condition is reportable per 10 CFR 50.72(b)(3)(ii)(B) for any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety, and per 10 CFR 50.72(b)(3)(v)(D) for any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. </br>Interim compensatory measures are to isolate the Fire Protection piping in the vicinity of the Raw Water Pump vault stairwell when severe weather is forecast.</br>The NRC Resident Inspector has been notified. NRC Resident Inspector has been notified.
20:23:00, 25 August 2016 +
52,201 +
21:11:00, 25 August 2016 +
20:23:00, 25 August 2016 +
On August 25, 2016, Engineering staff were … On August 25, 2016, Engineering staff were reviewing a proposed modification to install additional internal flooding protection for the Intake Building staircase down to the Raw Water Pump vault. Fort Calhoun Station determined that the existing Intake Building internal flooding and tornado-borne missile analyses did not sufficiently account for the potential of tornado-borne missiles striking Fire Protection piping in the Intake Building. A tornado-borne missile strike could potentially cause a double-ended rupture of Fire Protection piping in the vicinity of the stairwell down to the Raw Water Pump vault, which could cause flooding and subsequent failure of all four Raw Water Pump motors more quickly than bounded by the Engineering Analysis. The Engineering Analysis uses a postulated crack from a Moderate Energy Line Break per USNRC Branch Technical Position MEB 3-1, vice postulating a double ended pipe rupture. The resulting flow rate from this postulated crack is less than that possible from a tornado-borne missile strike. </br>This condition creates a potential loss of safety function from the Fort Calhoun Station Raw Water System (ultimate heat sink). All four Raw Water Pump motors could potentially become inoperable from flooding caused by a tornado-borne missile impacting the Fire Protection System Piping near the Raw Water vault stairwell prior to operator action to secure both Fire Pumps. </br>This condition is reportable per 10 CFR 50.72(b)(3)(ii)(B) for any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety, and per 10 CFR 50.72(b)(3)(v)(D) for any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. </br>Interim compensatory measures are to isolate the Fire Protection piping in the vicinity of the Raw Water Pump vault stairwell when severe weather is forecast.</br>The NRC Resident Inspector has been notified. NRC Resident Inspector has been notified.
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