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Institute of Nuclear Power Operations 2011 Operating Experience for Feedwater and related Systems Mike Ballard – INPO ER Group © 2011 Institute of Nuclear.

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Presentation on theme: "Institute of Nuclear Power Operations 2011 Operating Experience for Feedwater and related Systems Mike Ballard – INPO ER Group © 2011 Institute of Nuclear."— Presentation transcript:

1 Institute of Nuclear Power Operations 2011 Operating Experience for Feedwater and related Systems Mike Ballard – INPO ER Group © 2011 Institute of Nuclear Power Operations

2 2011 FW OE What is improving? Fewer problems noted with: Only 9 FW related scrams! 8 PWR, 1 BWR (but still too many) Failures related to gaps in PMs Feedwater heater tube leaks Digital components and controls FWPT controls – What is improving? Fewer problems noted with: Only 9 FW related scrams! 8 PWR, 1 BWR (but still too many) Failures related to gaps in PMs Feedwater heater tube leaks Digital components and controls FWPT controls – © 2011 Institute of Nuclear Power Operations 2

3 2011 FW Scram Causes 9 FW as of 12/14/2011(compared to 15 in 2010) 2 related to SPVs 2 attributed to insufficient initial design 1 caused by a recent design change 1 caused by a leak 2 related to weaknesses in operating procedures 1 not determined yet (Palisades 12/14/2011) 9 FW as of 12/14/2011(compared to 15 in 2010) 2 related to SPVs 2 attributed to insufficient initial design 1 caused by a recent design change 1 caused by a leak 2 related to weaknesses in operating procedures 1 not determined yet (Palisades 12/14/2011) © 2011 Institute of Nuclear Power Operations 3

4 2011 FW Scrams SPVs 1/19/2011 Palo Verde, Auto Scram - FW pump tripping on low suction pressure following a FWP mini-flow valve failing open. A relay in the valve controls failed. FW flow to be diverted to the condenser. Unrecognized SPV and no PM. 6/26/2011 Wolf Creek, Manual Scram – Suring startup from a RFO, 'B' FW pump tripped. Cause of the trip was in the FWPT controls. Aging and obsolete circuit cards. Known SPV, but with a low priority for mitigation. SPVs 1/19/2011 Palo Verde, Auto Scram - FW pump tripping on low suction pressure following a FWP mini-flow valve failing open. A relay in the valve controls failed. FW flow to be diverted to the condenser. Unrecognized SPV and no PM. 6/26/2011 Wolf Creek, Manual Scram – Suring startup from a RFO, 'B' FW pump tripped. Cause of the trip was in the FWPT controls. Aging and obsolete circuit cards. Known SPV, but with a low priority for mitigation. © 2011 Institute of Nuclear Power Operations 4

5 2011 FW Scrams Original Design 8/11/2011 Nine Mile Pt 2, Manual Scram During start- up from an outage at 15 percent power; a manual scram was inserted because of a vent line pipe break on the min flow line of the FW pump. Cause of the was a cantilevered pipe and vibration induced fatigue. Recent Design 8/19/2011 Susquehanna, Auto Scram – Scram occurred during a test of RV high level trips. A field installed jumper was incorrectly terminated in the new feedwater control panel. The wiring error likely occurred during the recently completed RFO when digital integrated control system was installed. Original Design 8/11/2011 Nine Mile Pt 2, Manual Scram During start- up from an outage at 15 percent power; a manual scram was inserted because of a vent line pipe break on the min flow line of the FW pump. Cause of the was a cantilevered pipe and vibration induced fatigue. Recent Design 8/19/2011 Susquehanna, Auto Scram – Scram occurred during a test of RV high level trips. A field installed jumper was incorrectly terminated in the new feedwater control panel. The wiring error likely occurred during the recently completed RFO when digital integrated control system was installed. © 2011 Institute of Nuclear Power Operations 5

6 2011 FW Scrams Leak Related Scram 3/26/2011 Diablo Canyon, Manual Scram – Following the loss of FW pump 2-1. The pump tripped because of water spray on its control console. The water spray was caused by leakage from the flange of the relief valve on a FW heater condenser dump valve line. Leak not repaired in a timely manner, flange insufficiently torqued. Leak Related Scram 3/26/2011 Diablo Canyon, Manual Scram – Following the loss of FW pump 2-1. The pump tripped because of water spray on its control console. The water spray was caused by leakage from the flange of the relief valve on a FW heater condenser dump valve line. Leak not repaired in a timely manner, flange insufficiently torqued. © 2011 Institute of Nuclear Power Operations 6

7 2011 FW Scrams AOVs 12/14/2011 Palisades The reactor was manually when both FW pumps tripped on low suction pressure due to an unplanned opening of the 'A' FW pump recirc valve. Cause? AOVs 12/14/2011 Palisades The reactor was manually when both FW pumps tripped on low suction pressure due to an unplanned opening of the 'A' FW pump recirc valve. Cause? © 2011 Institute of Nuclear Power Operations 7

8 Other Notable 2011 FW OE What types of problems should we be concerned with? –Leaks –AOVs/Positioners/Controllers – aging, manf defects, MA errors –Pump seal and bearing failures –SPV mitigation What types of problems should we be concerned with? –Leaks –AOVs/Positioners/Controllers – aging, manf defects, MA errors –Pump seal and bearing failures –SPV mitigation © 2011 Institute of Nuclear Power Operations 8

9 Extraction Steamline Bellows In July 2011, Unit 1 went into a maintenance outage to replace failed extraction steam bellows inside the main condenser. The failure mechanism was cyclic stress and fatigue. The root cause is ineffective preventive maintenance. PMs were only an external visual inspection of the expansion joint. Such inspections were not capable of identifying impending fatigue failure. The PM Basis identifies the component as non-critical and NOT run to failure; however, it was treated as run to failure and the consequences of its failure were not anticipated. © 2011 Institute of Nuclear Power Operations 9

10 Leak Events Causing Shutdowns Air, oil, water, steam ehc fluid leaks have caused station events. Sometimes leaks are tolerated and not repaired in a timely manner. OE Through Wall Leak resulted in a Near-Miss, Unit 3 Shutdown and Unplanned Pipe Replacement (Oconee) - On January 12, 2011 a leak was reported in the Unit 3 Turbine Building Basement. An operator found a leak near a FW heater control valve. The leaking piping was a carbon steel flange immediately downstream of a control valve. The through-wall leak progressed rapidly and expanded to a point where leak repair was no longer practical, resulting in a decision to shutdown the unit to effect repairs. Pilgrim - Technical Specification Required Shutdown Due To Inoperable Feedwater Check Valve - PEN On November 17, 2011, with the reactor at 50% power, the station entered a 24 hour action statement from a FW check valve leak. Air, oil, water, steam ehc fluid leaks have caused station events. Sometimes leaks are tolerated and not repaired in a timely manner. OE Through Wall Leak resulted in a Near-Miss, Unit 3 Shutdown and Unplanned Pipe Replacement (Oconee) - On January 12, 2011 a leak was reported in the Unit 3 Turbine Building Basement. An operator found a leak near a FW heater control valve. The leaking piping was a carbon steel flange immediately downstream of a control valve. The through-wall leak progressed rapidly and expanded to a point where leak repair was no longer practical, resulting in a decision to shutdown the unit to effect repairs. Pilgrim - Technical Specification Required Shutdown Due To Inoperable Feedwater Check Valve - PEN On November 17, 2011, with the reactor at 50% power, the station entered a 24 hour action statement from a FW check valve leak. © 2011 Institute of Nuclear Power Operations 10

11 Leak Events Causing Downpowers OE Smoke Emitted from Feedwater Pump Due to Oil Contaminated Insulation (Nine Mile Pt 2 ) - On March 6, 2011, a Unit 2 FW pump began to emit smoke from the inboard side which resulted in a rapid power reduction to remove the pump from service. OE Reactor Feedpump Turbine (RFPT) Taken Out of Service Due to a Control Valve Actuator Leak (Peach Bottom) - On October 26, 2011 Operations identified no oil level in the 3B RFPT Hydraulic Power Unit (HPU) tank site glass. Inspection of the area identified a 60 dpm leak at the CV actuator supply fitting, which required the 3B RFPT to be taken out of service. The ½ inch stainless steel tubing was misaligned, installed and tightened under tension. OE Smoke Emitted from Feedwater Pump Due to Oil Contaminated Insulation (Nine Mile Pt 2 ) - On March 6, 2011, a Unit 2 FW pump began to emit smoke from the inboard side which resulted in a rapid power reduction to remove the pump from service. OE Reactor Feedpump Turbine (RFPT) Taken Out of Service Due to a Control Valve Actuator Leak (Peach Bottom) - On October 26, 2011 Operations identified no oil level in the 3B RFPT Hydraulic Power Unit (HPU) tank site glass. Inspection of the area identified a 60 dpm leak at the CV actuator supply fitting, which required the 3B RFPT to be taken out of service. The ½ inch stainless steel tubing was misaligned, installed and tightened under tension. © 2011 Institute of Nuclear Power Operations 11

12 AOVs/Controllers/Positioners At least 8 substantial unplanned downpowers OE34299 – FW Reg Valve Positioner Failure Causes an Unexpected Reduction in RV Level (Vt Yankee) - On August 10, 2011 while at 100% power, RV level lowered 8 inches unexpectedly. The Siemens PS2 positioner failed, causing the valve to move in the closed direction - reducing FW flow. OE Plant Runback Due to Newly Identified Failure Mode for Valve Controller (Watts Bar) - On May 25, 2011, an intermediate pressure heater string isolated requiring a manual turbine runback from 85% to 75% power. Plastic tubing inside the bypass level control valve's controller split open causing the valve to close. With all level control valves now closed, heater level rose quickly to the HI-HI level setpoint which initiates a heater string isolation. At least 8 substantial unplanned downpowers OE34299 – FW Reg Valve Positioner Failure Causes an Unexpected Reduction in RV Level (Vt Yankee) - On August 10, 2011 while at 100% power, RV level lowered 8 inches unexpectedly. The Siemens PS2 positioner failed, causing the valve to move in the closed direction - reducing FW flow. OE Plant Runback Due to Newly Identified Failure Mode for Valve Controller (Watts Bar) - On May 25, 2011, an intermediate pressure heater string isolated requiring a manual turbine runback from 85% to 75% power. Plastic tubing inside the bypass level control valve's controller split open causing the valve to close. With all level control valves now closed, heater level rose quickly to the HI-HI level setpoint which initiates a heater string isolation. © 2011 Institute of Nuclear Power Operations 12

13 Pumps Eight downpowers or outage delays attributed to problems with bearings and seals OE Excessive Vibration of Feedwater Pump Inboard and Outboard Radial Bearings Resulted in Plant Down Power (Waterford) OE B Reactor Feed Pump Removed from Service (Hatch) - An investigation revealed three likely causes of the bearing failure: Electrical Pitting, Foreign Material in the Oil Supply, and Internal Component misalignment. OE Water Intrusion into Reactor Feed Pump Lube Oil System Due to Worn Labyrinth Seals. (Monticello) Eight downpowers or outage delays attributed to problems with bearings and seals OE Excessive Vibration of Feedwater Pump Inboard and Outboard Radial Bearings Resulted in Plant Down Power (Waterford) OE B Reactor Feed Pump Removed from Service (Hatch) - An investigation revealed three likely causes of the bearing failure: Electrical Pitting, Foreign Material in the Oil Supply, and Internal Component misalignment. OE Water Intrusion into Reactor Feed Pump Lube Oil System Due to Worn Labyrinth Seals. (Monticello) © 2011 Institute of Nuclear Power Operations 13

14 Questions? © 2011 Institute of Nuclear Power Operations 14


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