Page 22 - July-August 2012
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22
Nuclear Plant Journal, July-August 2012
Research &
Development
Zinc Injection
Increased application of zinc injection
to reduce plant radiation fields has resulted
in several instances of tenacious crud
formation on fuel cladding surfaces. At
one plant, these formations have led to fuel
failures. EPRI fuel surveillance and testing
in recent years has advanced understanding
of the role of zinc in crud formation and
its impact on fuel performance. These
results have been incorporated into EPRI’s
water chemistry and fuel reliability
guidelines to provide recommendations
on how to reduce crud deposition. Nuclear
industry implementation of this guidance
has reduced the occurrence of thick
and tenacious crud, thereby lowering
challenges to fuel integrity.
The beneficial effect of zinc injection
on plant dose rates is believed to result
from two factors: (1) Zinc deposits on
stainless steel piping surfaces, reducing
the deposition of cobalt and the resulting
accumulation of gamma-emitting Co-60;
and (2) Zinc preferentially deposits on
fuel rod surfaces to create more stable fuel
deposits, which prevent activated corrosion
products from being released into the
reactor water.
Contact: Aylin Kucuk, telephone:
Predictive Methods
New predictive capabilities will help
plant personnel optimize operating and
maintenance practices and extend lifetime
after pitting damage is discovered in steam
turbine blades.
EPRI is on the threshold of
introducing the first practical methodology
for predicting and managing early stages
of corrosion-fatigue in the steam turbine
blades of nuclear and fossil power
plants. For the first time, plant personnel
will have the ability to apply inspection
and operations data to predict damage
progression, estimate remaining life, and
assess the risk of continued operations.
Preventing a single serious failure could
avoid equipment damage, personal injury,
and potentially several million dollars in
productivity losses and repair costs.
Life-limiting blade fatigue cracks,
which represent an increasing concern in
aging turbines, often initiate in corrosion
pits. According to work sponsored by
EPRI and other organizations, corrosion
begins and pitting damage accumulates
during water-steam chemistry excursions
caused by condenser leaks or by improper
layup and shutdown conditions.
An EPRI report to be published by
fall 2012 will present an updated version
of the methodology benchmarked against
inservice experience with 403/410SS
components. The report will include initial
guidance for extending the methodology to
17%Cr-4%Ni stainless steel (17-4PH) and
other materials. Laboratory experiments to
quantify the pit-to-crack transition in 17-
4PH samples are under way.
Contact: David Gandy, telephone:
Acoustic Mouse
The Phased-Array Acoustic Mouse
for hand-held ultrasonic inspection is a
manual inspection system offering real-
time 3-D imaging, improving inspection
accuracy, component reliability, and plant
safety while eliminating unnecessary
maintenance tasks.
More commonly applied manual
ultrasonic testing methods may lead to
overly conservative interventions. EPRI
is creating an advanced, hand-held system
that could revolutionize nondestructive
evaluation (NDE) programs by delivering
real-time ultrasonic images matching
or exceeding the precision provided by
automated techniques at a fraction of the
expense.
Contact: Brian Schimmoller, email:
Robotic Inspection
Robotic inspection enables condition-
based monitoring of transmission lines,
enhancing safety, reducing inspection
costs, and improving system reliability.
Overheadtransmissionlinesareamong
theutility industry’smostwidelydistributed
assets, traversing tens of thousands of
miles, often in remote locations. To expand
inspection capabilities and increase
cost-effectiveness, EPRI is developing a
transmission line inspection robot that can
be permanently installed on these lines,
and traverse 80 miles of line at least twice
a year, collecting high-fidelity information
that utilities can act on in real time. AS the
robot crawls along the transmission line,
it uses various inspection technologies to
identify high-risk vegetation and right-
of-way encroachment, and to assess
component conditions.
Contact: Brian Schimmoller, email:
Sequestration Resins
Novel resins reduce critical-path
downtime,
decreasing
occupational
exposure and minimizing radioactive
waste volumes.
During nuclear plant maintenance or
refueling outages, current ion exchange
resins may require several days to reduce
concentrations of cobalt and other
activated corrosion products to safe
levels in reactor coolant streams. This
performance limitation often delays key
maintenance activities. EPRI’s Office
of Technology Innovation is developing
novel sequestration resins expected to
provide at least a three-fold increase in
removal capacity for transition-metal
impurities in light water reactor coolants.
They also offer the potential for higher
overall removal efficiencies, which would
reduce occupational exposures and waste
management costs.
Contact: Brian Schimmoller, email:
Air-Operated Valves
Digital delivery of maintenance guide
on air-operated valves provides real-
time, in-plant access to key component
information.
An increased awareness of the
importance of air-operated valves (AOVs)
has led to progressively more sophisticated
maintenance practices in both nuclear and
fossil power plants. EPRI is developing a
knowledge transfer “app” for mobile and
tablet devices that will enable nuclear
maintenance workers to access a visually-
based, content-rich tool to support AOV
maintenance activities. Digital delivery
of the EPRI maintenance guide will
enable nuclear plants to train and evaluate
new personnel, refresh personnel on
infrequently performed activities, replace
face-to-face training workshops, and
reduce staff travel.
Contact: Brian Schimmoller, email:
