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Diamond
Wire Saw Cuts Huge Opening in Nuclear Power Plant Containment
Building
Officials at Consumers Power Company decided they had to replace
the old steam generators at their Palisades pressurized water
nuclear plant near South Haven, Michigan. One problem: the
steam generators were larger than the equipment hatch. Therefore,
an opening adequate to accommodate the generators had to be
cut into the 3.5" thick concrete wall. To make matters
more challenging, the concrete contained 2" diameter
rebar and was lined with 1/4" thick steel plate.
In
partnership with the General Contractor, Bechtel Power Corporation
determined a high speed, diamond wire saw was the best way
to cut the opening. Diamond wire sawing is a fast and precise
method of cutting and removing large concrete masses, leaving
little debris. Concrete Cutting & Breaking, Inc. - West
Michigan - was commissioned to cut the wall.
It
was apparent to CCB that three factors were going to make
this an extremely difficult project: the steel liner, the
curve of the wall, and the fact that much of the work had
to be done 25' above grade. The sawing work actually consisted
of phased cutting of four large blocks of concrete. Two blocks
- 3' x 2'6" x 3'6" - had to be cut first; Bechtel
could then install two large I-beams into the opening. The
I-beams served as a rail for a cart to transport the large
blocks and the steam generators out of the building once the
cutting was complete.
The
next block cut was 3'6" x 17' x 3'6" thick. This
opening allowed the cart to be put in place under the largest
block, which was to be cut last. The last and largest block
cut was 28' x 26'8" x 3'6" thick.
CCB
used two, four-man crews working double shifts to meet the
cutting schedule. The actual sawing took nine days. From beginning
to end, the wall was only open 25 days as the old steam generators
were removed and the new ones installed.
This
project was the first time this method of changing steam generators
was done in the U.S. It could never have been completed in
such a short cycle if diamond wire sawing had not been employed
by such a highly skilled concrete sawing firm as Concrete
Cutting and Breaking.
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