The team identified an
URI associated with potential fire-induced electrical circuit failures in the charging
header flow control valve control circuit. A postulated fire in fire area FAA-070 could result in fire-induced electrical circuit faults in the control cables and control logic of the charging flow control valve causing the valve to close and shut off cooling flow to the
reactor coolant pump (
RCP) seals. This issue is unresolved pending further NRC review of whether the licensee is required to design against such a failure mode. The team reviewed cable routing information for charging
header flow control valve 1-FCV-62-093 and determined that two cables in the control logic for the valve were routed in fire area FAA-070 without appropriate separation or protection. These cables were identified as 1PM108 and 1PM110. Both cables provided a 10-50 milliamp signal for control of the charging pump discharge air operated valve (
AOV). A cable-to-cable
hot short of 50 milliamps in either cable could spuriously close the
AOV and stop all
RCP seal injection flow. The team determined that both cables were routed in trays with other signal cables of 10-50 milliamps so that a cable-to-cable
hot short of this type could potentially occur. However, because the cables were shielded twisted pairs with drain wires, it is not likely a failure of this type could occur without the cables shorting to each other or to ground. This item is unresolved pending further NRC review to determine whether the licensee is required to design against such a failure mode. This issue is identified as
URI 05000327,328/2005011-07, Potential for Fire Damage to Spuriously Close the Charging
Header Flow Control Valve.
