Page 40 - Nuclear Plant Journal - March April 2013
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40
Nuclear Plant Journal, March-April 2013
capabilities for robotic inspection have
been proven on many major global
nuclear plant projects conducted since the
1990s. Diakont selected their RODIS-18
ILI robot model for this project, in order
to meet the specified pipe geometry and
inspection parameters. The RODIS-18
is a self-propelled robotic pipe crawler
that navigates bends and vertical piping,
and requires only a single small access
point. This tool utilizes Electromagnetic
Acoustic Transducer (EMAT) ultrasonic
NDE sensors for measuring pipe wall
thickness, and for detecting andmeasuring
any potential defects such as corrosion,
pitting, and cracks. One key advantage
EMAT has over conventional UT is
that it does not require any couplant or
extensive surface preparation; it generates
ultrasonic waves within the object pipe
material using magnets and coils.
SI was responsible for completing
a crucial pre-inspection activity –
developing the flaw evaluation and
acceptance criterion for the pipe and
fittings in accordance withASME Section
XI code requirements. Completing these
calculations in advance of the inspection,
creating a “flaw handbook”, expedited
the inspection activity so that it would
stay off the critical path outage schedule.
SI’s technical approach was based on the
premise that while the piping may have
thinned locations that violate the design
minimum thickness requirements, the
thinning may be limited to the extent that
it does not jeopardize the overall pipe
structure. Diakont worked closely with
SI to utilize inspection tool detection
thresholds and measurement accuracies
that met or exceeded these established
critical flaw sizes.
As part of the inspection project
planning, Diakont fabricated a full-
fidelity mockup of CNS’ HPCI piping
at their service center facility, exactly
replicating the size and configuration of
what would be encountered at the plant.
The purpose of the mockup was two-fold:
to validate proper tool operation, and to
provide a means for performing crew
training. The mockup was embedded
with representative defects that simulated
what might be encountered in the field,
with some being smaller and some larger
than the critical sizes. The Cooper NDE
Level III technician participated in this
live demonstration, to verify the operator
and tool performance. The mockup was a
valuable component of the overall project
success.
The Diakont/SI inspection team
mobilized to CNS in October 2012
to perform the inspection. Since the
robot launch site in the ECST room
was a radiological-controlled area,
Diakont set up a remote operations
center in a clean area in a different part
of the Control Building. This allowed
for easy communication between the
Outage Control Center and the Diakont/
SI personnel, and considerably reduced
personnel dose exposure.
Prior to inspecting the pipe with
the ILI robot, CNS pressure washed the
pipe with ~800 gallons of Deionized
Water (DI) water. A subsequent visual
inspection of the pipe revealed water in
the lower section of the pipe beyond the
second 45° elbow through the straight
portion. The excess water was vacuumed,
but a small amount (<½” deep) remained
in the bottom of the straight portion. This
amount of residual water was deemed
acceptable and would not interfere with
ILI robot EMAT sensors.
The Diakont tool was deployed into
the HPCI line and began capturing EMAT
NDE data. The analysis of this data was
performed in real-time, and compared
to the predetermined flaw acceptance
criteria. The Diakont/SI team provided
a preliminary summary of the inspection
findings to plant personnel at the end of
each shift. Integral video cameras on the
Diakont robotic tool were used throughout
the inspection to support navigation
through the piping system, and also to
ensure proper Foreign Material Exclusion
(FME) controls. Once the inspection was
complete, these video images provided
a visual record that FME controls were
maintained throughout the project, and
that the piping system remained free of
foreign material. As part of the daily
Diakont Pipe Inspection Robot.
Diakont Full-Fidelity HPCI Pipe Mockup.
Robotic Pipe...
