Nuclear Plant Journal, March-April 2016 NuclearPlantJournal.com
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Ratko Vojvodic
Ratko Vojvodic is Technical Consultant
in the Non Destructive Examination
(NDE) Solutions business unit within the
Reactors and Services Business Group at
AREVA Inc.
Officially named
AREVA’s expert
in non destructive
examination,
Ratko is the U.S.
representative
for AREVA’s
world-wide
non-destructive
examination
technical center
located in Chalon-
sur-Saone, France.
Winner of the
several technical
awards, Ratko has
an important role
in the development
of methods and
techniques supporting non destructive
examinations especially in the domain
of the automated analysis. His work
and leadership led to the development
and implementation of single and dual
automated data analysis which improved
the examination process exceeding the
industry requirements.
Ratko holds a Bachelor of Science
degree in Electrical Engineering from
The University of Zagreb, Croatia.
However, this approach doesn’t work
on all generators. We’re also inspecting
larger steam generators with more than
15,000 tubes each. For this case, it
would be difficult to achieve the goal
of inspecting the steam generator with
one set of probes. However we have still
minimized the required intervention by
humans and thus improved the process
with respect to safety, dose and human
performance, all of which support our
pillars of operational excellence.
3.
Do you foresee minimizing the
number of technical personnel in
radiation areas as compared to sending
robots to do the job?
Smith:
The pride and passion of our
people drive everything we do at AREVA.
We complement our robotic technologies
with our skilled and reliable workforce
to provide safe and efficient solutions
for our customers. We use robotics for
reactor vessel and reactor vessel head
NDE inspections. Skilled technicians
are responsible for operating our robots,
and collecting and analyzing the data to
support the inspection.
In the case of steam generators, we
use a robot called
Ranger
.
Ranger
is a
robotic arm that we install in the steam
generators that delivers probes safely,
reliably and efficiently to any tube in
the generator. The technician operates
Ranger
, collects and analyzes the data,
and performs additional inspections
based on the information received by
Ranger
.
Vojvodic:
Steam generator inspec-
tion scopes can have more than 30,000
tubes with some tubes measuring up to 90
feet long. Eddy current inspection probes
move through the tube with the speed of
up to 100 inches per second. Enormous
quantities of data are generated in a short
amount of time and it has to be analyzed
in real time. The bobbin probe is still a
dominant technology in the steam gener-
ator tubing examination. Rotating probe,
traditionally used in the areas where addi-
tional information is needed, is being re-
placed by the multi coil transmit receive
array probe, further increasing the quan-
tity of data and reducing the time avail-
able for the data analysis.
We are now moving to combine the
best of human and computerized analy-
sis. People are best at reviewing data and
making an intelligent decision based on
the input from computers. Computers
provide the background work that is nec-
essary to get good
results. With hu-
mans and computers
combined, we are
improving reliabil-
ity and efficiency of
the overall process.
The
Electric
Power Research Insti-
tute (EPRI) guidelines
for steam generator
inspection
require
dual analysis. This is
typically completed
with the combina-
tion of manual and
automated analysis,
moving more and
more often to dual
automated. We also
have the option of a
single, integrated automated analysis that
provides redundancy through indepen-
dent systems or independent configura-
tions embedded into one process, as long
as we demonstrate and document redun-
dancy of the process. This demonstrates
to the regulator, utility and independent
oversight that the required duality is re-
tained through different detection algo-
rithms and classification logic by pro-
ducing two sets of results, each meeting
very strict performance demonstration re-
quirements. Results can be kept separate
prior to submitting them to further review
or merged, keeping the most conservative
ones or by applying the additional logic
when deciding on their relevance.
Automated analysis has been in
use for the last 25 years. The level of
automation and the performance of
the tools is increasing continuously.
However, in the last few years, the pace
of development increased exponentially.
We developed a platform that resulted
in three automated analysis tools that
are fully EPRI AAPDD (Auto Analysis
Performance Demonstration Database)
qualified – AIDA
3
, MIRA
3
and Walking
Through the Tube (WTT).
AIDA
3
and MIRA
3
are based on two
different sets of detection techniques,
assuring duality through redundancy
and diversity as required by industry
guidance. They both implement a rules
based classification process that is built
combining more than 150 components
from the “evaluators toolbox” using
Boolean logic, flow redirection and
voting system.
Today’s signal processing knowledge
offers other concepts that can be used in
