POWER November 2013 - 31

Top planTs
to address the hazards associated with the
project and the scope of a major component
replacement. The plan addressed all elements
of safety-industrial, nuclear, and radiological-early
in the project. SGT collaborated
with Entergy's training staff to ensure that
incoming personnel understood all safety
aspects of the job before being released to
the field. Throughout the project, there were
numerous vendors who visited the site to provide
specialized training to the team. The replacement
would be among the largest SGT
had ever attempted, as the new 720-ton, 65foot-long
steam generators were two of the
heaviest SGT had ever worked with.
The project included extensive pre-outage
work. Marine operations consisted of levee
upgrades and offloading and transporting
the replacement steam generators from the
Mississippi River to a temporary on-site
storage location.
The outage was originally scheduled
for early 2011, but three months before
work was to begin on the plant, the project
had to be deferred 18 months because
of delays in delivering the new steam
generators. In addition to requiring a revision
of the project budget, this schedule
change posed some substantial logistical
challenges. Multiple major modifications
(among them replacement of a coolant
pump motor and radiography around the
reactor vessel) had been scheduled to occur
during the next outage after the steam
generator replacement. The delay of the
steam generator delivery meant that these
modifications now needed to occur at the
same time. Incorporating these modifications
into the steam generator replacement
schedule required extensive coordination
between SGT and Entergy personnel.
There was another challenge from the
deferment: The delays caused the outage
to occur simultaneously with several other
nuclear plant outages nationwide, including
other steam generator replacements. This
meant careful planning and coordination was
necessary to ensure sufficient staffing and resources
would be available to complete the
work on time.
An Ill Wind
Then, in the fall of 2012, just seven weeks
from the scheduled start of the outage, a
new challenge began bearing down on the
site: Hurricane Isaac. When it became clear
that the plant was in the path of the storm,
Entergy and SGT assembled an emergency
team to prepare the site. The plant itself was
shut down as the hurricane approached, and
major equipment and temporary structures
that had been built for the project were either
removed or safely secured. The emergency
team remained on the site during the storm to
ensure safety of the plant.
Though Waterford suffered only minor and
mostly superficial damage from the storm,
the evacuation, cleanup, and repairs meant
a two-week loss in the pre-outage schedule.
But rather than push the outage back again,
personnel worked additional overtime and
the project team added a second shift to re1.
A tight fit. Precise engineering and meticulous planning were necessary to move the
new steam generators-which weighed more than 700 tons each-into place. Courtesy: URS
main on track. The outage began on Oct. 17,
2012, as scheduled.
To remove the old steam generators and
install the new ones, a 34-foot by 33-foot
opening was cut in the containment building
using hydrodemolition. A temporary work
platform was built alongside the building
to support the operation. The opening had
to be cut in close proximity to the dry and
wet cooling towers, which meant very careful
crane operations were necessary to move
the 179-ton block of concrete out of the way.
The old reactor vessel closure head was
removed at this point so that the removal of
interferences around the old steam generators
could begin. Substantial elements of the
main steam tower frames had to be removed,
and a specialized rigging scheme had to be
built inside the containment building to lift
out the old generators and remove them
safely. Among other equipment, an entire
portable crane was rigged through the opening
into the containment building to support
the operation.
With the old steam generators out, the process
was then conducted in reverse to move
the new steam generators into place (Figure
1). A key challenge in installing the new
steam generators was meeting the required
fit-up tolerances of the primary coolant system
piping. The replacement steam generator
fit-up was optimized to include the secondary
side large bore piping, lower steam generator
support system, and upper steam generator
support system, which included a complex
snubber assembly.
Finally, the new reactor vessel head was installed,
and the temporary opening in the containment
building was closed. The component
replacements were completed in just under 48
days, and the entire outage, including refueling,
was completed in 93 days. Waterford 3
returned to operation on Jan. 18, 2013.
On-site project manpower, both staff
and craft, peaked at approximately 1,400.
The project sustained no OSHA recordable
or lost time accidents despite more than
500,000 man-hours worked during the replacement
work in the outage. Over the life
of the project, the team completed more than
1.3 million man-hours with only one OSHA
recordable injury. The project team received
multiple safety awards from the National
Safety Council, including the Million Hour
Award, Perfect Record Award, and Occupational
Excellence Achievements Award.
For completing such a critical operation
successfully, safely, and under budget
despite multiple setbacks and challenges,
Waterford 3 is a well-deserving POWER
Top Plant. ■
-Thomas W. Overton, JD is POWER's gas
technology editor.
November 2013 | POWER
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POWER November 2013

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