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On July 30, 2004, at approximately 18:45 M … On July 30, 2004, at approximately 18:45 Mountain Standard Time (MST), Palo Verde Nuclear Generating Station Units 1, 2, and 3 were operating at approximately 100% power at normal operating temperature and pressure when it was discovered that a void in the post-LOCA (Loss Of Coolant Accident) recirculation piping from the containment sump may have prevented fulfillment of the safety function to remove residual heat and mitigate the consequences of a Loss of Coolant Accident. The volume of the ECCS (Emergency Core Cooling System) piping sections between the closed containment sump isolation butterfly MOVs (SIAUV0673/0674 and SIBUV0675/0676) and the associated train sump recirculation check valves (SIAV205 and SIBV206) are void of water and occupied with air (Approx. 120 cubic feet). The concern is that during a Recirculation Actuation Signal (RAS) the trapped volume of air between the isolation valves and the downstream check valve cold potentially enter the operating SI pumps (HPSI and CS), which could potentially cause cavitations and/or air binding of the pumps or possibly a water hammer event.</br>RAS does not occur for approximately 20 minutes, or longer following a LOCA. In accordance with Generic Letter 91-18, substitution of manual action for automatic action to open the inner containment sump isolation valves following a LOCA, but prior to the RAS setpoint will allow the void to clear, with the exception of a small section between the outer containment isolation valve and the check valve. Engineering had provided reasonable assurance that the recirculation check valve void will not result in an unacceptable void fraction forming in the HPSI/Containment Spray pump suction piping and pump.</br>The Control Room Operators have been briefed on the need to perform the manual Operator action to open the inboard ECCS Sump isolation valves (SIAUV673 and SIBUV675) upon receipt of a Containment Spray Actuation System (CSAS) actuation. Each Shift Crew will be briefed accordingly until the EOPs are revised to incorporate this action (will take about 24 hours to be incorporated).</br>Engineering continues to evaluate this condition.</br>There were no RPS/ESF actuations, and none were required.</br>There were no structures, systems or components that were inoperable at the start of (the) event that contributed to the event.</br>This condition did not result in any challenges to the fission product barrier or result in any releases of radioactive materials. There were no adverse safety consequences or implications as a result of this event. This condition did not adversely affect the safe operation of the plant or health and safety of the public.</br>The NRC Resident Inspector was notified of this event by the licensee.as notified of this event by the licensee.
01:45:00, 31 July 2004 +
03:20:00, 31 July 2004 +
01:45:00, 31 July 2004 +
On July 30, 2004, at approximately 18:45 M … On July 30, 2004, at approximately 18:45 Mountain Standard Time (MST), Palo Verde Nuclear Generating Station Units 1, 2, and 3 were operating at approximately 100% power at normal operating temperature and pressure when it was discovered that a void in the post-LOCA (Loss Of Coolant Accident) recirculation piping from the containment sump may have prevented fulfillment of the safety function to remove residual heat and mitigate the consequences of a Loss of Coolant Accident. The volume of the ECCS (Emergency Core Cooling System) piping sections between the closed containment sump isolation butterfly MOVs (SIAUV0673/0674 and SIBUV0675/0676) and the associated train sump recirculation check valves (SIAV205 and SIBV206) are void of water and occupied with air (Approx. 120 cubic feet). The concern is that during a Recirculation Actuation Signal (RAS) the trapped volume of air between the isolation valves and the downstream check valve cold potentially enter the operating SI pumps (HPSI and CS), which could potentially cause cavitations and/or air binding of the pumps or possibly a water hammer event.</br>RAS does not occur for approximately 20 minutes, or longer following a LOCA. In accordance with Generic Letter 91-18, substitution of manual action for automatic action to open the inner containment sump isolation valves following a LOCA, but prior to the RAS setpoint will allow the void to clear, with the exception of a small section between the outer containment isolation valve and the check valve. Engineering had provided reasonable assurance that the recirculation check valve void will not result in an unacceptable void fraction forming in the HPSI/Containment Spray pump suction piping and pump.</br>The Control Room Operators have been briefed on the need to perform the manual Operator action to open the inboard ECCS Sump isolation valves (SIAUV673 and SIBUV675) upon receipt of a Containment Spray Actuation System (CSAS) actuation. Each Shift Crew will be briefed accordingly until the EOPs are revised to incorporate this action (will take about 24 hours to be incorporated).</br>Engineering continues to evaluate this condition.</br>There were no RPS/ESF actuations, and none were required.</br>There were no structures, systems or components that were inoperable at the start of (the) event that contributed to the event.</br>This condition did not result in any challenges to the fission product barrier or result in any releases of radioactive materials. There were no adverse safety consequences or implications as a result of this event. This condition did not adversely affect the safe operation of the plant or health and safety of the public.</br>The NRC Resident Inspector was notified of this event by the licensee.as notified of this event by the licensee.
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