Phase 1 - Preparatory work while Unit 2 steam generator continues running at 100% power.
Bluegrass Core drilled (30) 4” diameter x 27” deep holes on each of the four, 3’ thick steam generator compartment roof plugs to be removed. This left as little as possible to drill once outage began.
Used slurry trap rings to keep water contained due to possible contaminants as well as recirculated cutting fluids to significantly reduce overall project volume.
Temperatures in upper containment while the unit was in operation required shift change every 90 minutes to keep work flowing.
Core drilled (14) 1” diameter holes on containment dome.
- (10) 1” holes for determining plumb locations for SCV liner to be cut.
- (4) 1” pilot holes for rigging alignment and to install water control.
Core drilled remaining 9” of all 120 holes.
Four wire saws set up on steam generator compartment (dog house) roofs to cut simultaneously.
- Two on each side
- Cut at an angle to facilitate plug removal.
- Each of the 4 plugs weighed approximately 72 tons.
Core drilled (4) 10” diameter holes on both sides of dome for rigging to remove concrete dome plug.
Bluegrass designed and fabricated angled plates for exact drilling.
Phase II - Critical path work done once outage was initiated.
Challenges and Time Management
Bluegrass worked with SGT to develop a water containment system that would use a PVC based gutter system to drain the slurry into barrels, removing the need for a global enclosure. Once captured in the barrels water was then recirculated to the wire saws, eliminating the need for continuous water.
During the process, Bluegrass was able to reduce its overall schedule by three shifts.