Post on 15-Jan-2016
Lessons Learned from Guy Wire and Anchor Replacement at Sequoyah
Nuclear Plant
by Doyle Pittman
12th NUMUG Meeting - 2008
2
Background
• 91-m tower erected in 1970
• Advance 33 in. triangular, galvanized tower
• Instrumented at 3 levels
• 18, 3/8 in. guy wires
• 6 guy anchors
• 2003 and 2004 inspections:
– Replace guy wires
– Replace two guy anchors
– Install new grounding
• Work order but no $$
12th NUMUG Meeting - 2008
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Background Continued
• Guy wire tension checked every 3-years
• Self assessment in 2006 found no tolerance limit for tension
• Acceptable range = 1050 to 2250 pounds per square inch
• Six wires outside range
• Declared tower unsafe to climb March 2007
• Investigated alternative ways to reach instruments – mobile crane with basket
12th NUMUG Meeting - 2008
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Lesson 1- Need Civil Engineer Support
• Maintain tower specifications
• Perform structural analysis– replace or repair tower – wind load less than design
• Guy anchor placement– slope– clearance– ground disturbance
• Tower condition
12th NUMUG Meeting - 2008
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Lesson 2 – Need for Workplan
• Training
• Forms/approvals
– crane operation
– digging permit
– NEPA review
– job safety analysis
– rigging planning
• Pre-job brief
– weather conditions
• Contingencies
– concrete drying
12th NUMUG Meeting - 2008
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Lesson 3 – Regulatory Implications
• Degraded condition determination
• Calibration due dates– Tolerance
– Tracking
• Data recoverability
• Limiting Condition for Operation – Moved to technical requirements manual
– Any two of three wind levels
– One of three temperature differences
12th NUMUG Meeting - 2008
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Getting Closer!
12th NUMUG Meeting - 2008
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New Guy Wire and Anchor
12th NUMUG Meeting - 2008
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12th NUMUG Meeting - 2008
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Success!!!
12th NUMUG Meeting - 2008