Page 16 - Nuclear Plant Journal Digital Edition: January - February 2013
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16
Nuclear Plant Journal, January-February 2013
Research &
Development
Fuel Pool Liners
EPRI is collaborating with EDF to
evaluate a polymer-based repair technique
that could be deployed robotically to
repair leaks in spent fuel pool liners.
The spent fuel pools used at nuclear
power plants are an integral part of safe
nuclear plant operation, serving both to
shield the radiation and to cool the fuel
rods. These pools are lined with ¼-inch
thick stainless steel sheets that are
welded together and anchored to concrete
walls. The potential for leaks from these
weld seams is raising concerns and has
prompted the development of advanced
inspection and repair techniques. In
one effort, EPRI and EDF are jointly
developing the prototype of an innovative
robotized technique that could be used in-
situ for in-service repairs.
Fuel pool leaks from the stainless
steel liners in spent fuel pools may contain
radioactive nuclides such as tritium and
strontium-90. These substances could
affect the structural integrity of the
concrete and the steel reinforcing bars in
fuel pools, and potentially contaminate
the groundwater.
EDF has developed inspection tools
to check suspect areas for cracking or
leakage from the liner seam welds and
from the welds used to attach the liner
to the concrete. These tools rely on
Alternating Current Field Measurement
(ACFM), in which a current is injected
locally into the weld, generating an
electrical field. The depth and length of
identified defects can then be determined
through analysis of this data.
EDF also has been investigating
leak repair options and has developed
a polymer-based solution that applies
a silicone patch in-situ directly on the
weld location. This technique, however,
requires two manual dives, one to place
the tool and inject the silicone into the
mold, and a second to disassemble the
chassis.
Building on this research, EDF
is working with EPRI to develop a
robotic delivery system for a metal strip
containing a repair polymer. The metal
strip would cover the entire weld length,
thereby eliminating the need to identify
the leak location by inspection.
Contact: Greg Frederick, telephone:
Mini-Robot
The robot is being designed to
function wirelessly and without tethers,
and will have the ability to move in all
directions to access difficult locations.
Remote-operated vehicles developed
for marine applications have proven
successful for the visual inspection
of submerged components in nuclear
reactor vessels and spent fuel pools, but
commercially available technologies
have several limitations. EPRI is working
with researchers at the Massachusetts
Institute of Technology (MIT) to create
a purpose-built robot delivering a step-
change improvement in the nuclear
power industry’s underwater inspection
capabilities.
The new robot is designed to
allow safe, reliable, and non-intrusive
operation while providing high-fidelity
visual inspection across a broad range
of components, configurations, and
locations. The initial prototype built and
tested by MIT features a compact and
appendage-free design, a high degree of
maneuverability, and wireless operation.
Its ovoid formmeasures about 4 inches by
6 inches, allowing it to nestle comfortably
in the palm of a hand.
Ongoing technology development
focuses on the mini-robot’s payload
and wireless communications system.
The payload is expected to include two
cameras. The first will support real-time
navigation and visual examination by
the robot operator, and the second will
capture higher-resolution imaging data
for subsequent inspection, nondestructive
evaluation, and asset management
applications.
A next-generation prototype is under
development, and experimental testing of
its improved visual inspection capabilities
is scheduled to begin in late 2013. A fully
functional mini-robot could be available
by 2015 for in-plant demonstration.
Contact: John Lindberg, telephone:
Maintenance Guide on a
Tablet
The
first-of-a-kind
application
aggregates information from various
EPRI guidance reports in an interactive,
user-friendly tool that can be accessed via
tablets and other mobile devices.
For many years, nuclear plants have
relied on EPRI equipment guides and
reports to optimize maintenance practices
and ensure high levels of equipment
reliability. Workforce and cultural shifts,
coupledwith technological advances, have
prompted EPRI to consider information
delivery mechanisms other than the
typical hardcopy reports and PDF files.
An initial effort to develop an “app-like”
guide for air-operated valve maintenance
is proving successful.
Through the Nuclear Maintenance
Application Center (NMAC), EPRI has
developed a tool that can be deployed
via computers and mobile devices to
transfer maintenance information in its
maintenance guides using realistic and
interactive animation, video and voice-
over features. The initial prototype,
focused on air-operated valves, includes:
User interaction to improve
•
knowledge transfer and to provide
practice on upcoming maintenance
activities.
Component familiarization through
•
interactive and animated 3D cut-
away views and exploded diagrams.
An immersive task-based trainer to
•
properly disassemble, inspect, re-
assemble, and troubleshoot the air-
operated valve.
Pop-up boxes to alert users to
•
important tasks and cautionary
measures.
The product, which was developed
and tested with input from several U.S.
and non-U.S. utilities, will be available in
two versions: one for laptop/desktop use
and one for mobile tablet use.
Contact: Mike Pugh, telephone:
Source: Electric Power Research
Institute’s (EPRI) Nuclear Executive Update,
September and November, 2012.
