lessons learned from guy wire and anchor replacement at sequoyah nuclear plant by doyle pittman 12th...
TRANSCRIPT
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
3
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
4
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
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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
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Getting Closer!
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8
New Guy Wire and Anchor
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Success!!!
12th NUMUG Meeting - 2008