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NuclearPlantJournal.com Nuclear Plant Journal, March-April 2016
LTE as...
locations in containment and the auxiliary
building and input into iBWave (common
DAS design software) to produce a
coverage map. Acceptance criteria for
coverage included the cellular standard
of 95 decibel-milliwatts (dBm) or higher.
The results of the feasibility study
were positive. In the auxiliary building,
the 730MHz test yielded approximately
twice the coverage of the 2130MHz
test. This was a substantial difference
considering the robustness of the power
plant infrastructure (thick concrete walls
reinforced with rebar, complex piping
arrangements, secluded rooms, etc.)
which absorb or reflect energy released.
The tests in the auxiliary building
included a DAS with radiating “leaky”
coax cable to distribute the signal.
Testing in containment included a
DAS feeding a single source antenna
located at the upper elevation to distribute
signal. Test results indicated acceptable
coverage on all three elevations in
containment at both 730MHz and
2130MHz frequencies. In this case,
both frequencies were successful in
containment due to the open environment
and the ability for signal to propagate
without being absorbed.
Moving Forward
The feasibility testing demonstrated
that a DAS utilizing high-performance
radiating cable can substantially improve
LTE based wireless coverage within
dense concrete and steel facilities when
utilizing the low frequency bands. As a
next step, EPRI is working with another
utility to go full scale with a DAS and
test capabilities working through a
cellular carrier. If successful, future
technologies such as continuous online
monitoring of equipment could mark
the beginnings to a new era of nuclear
power plants supporting the goal of safe,
reliable and affordable electricity. EPRI
is documenting test results and lessons
learned to share with the industry in
a technical report in late 2016 when
research is completed.
Contact: Nick Camilli, EPRI,
telephone: (704) 595-2594, email:
.
Research &
Development...
degradation of concern. Reid said that all
EPRI research so far—at Calvert Cliffs
and other field sites and from lab tests—
indicates that canisters are “robust.” But
he added, “There is recognition that the
same materials in other nuclear plant
systems are prone to degradation, and
these casks will be in service a long time.
We have to make sure that they are well
managed.” Researchers will use data
now being gathered from other casks to
strengthen EPRI’s cask aging models.
High-Burnup Fuel Storage
Over time, the nuclear industry has
increased its fuel burnup to improve
reactor economics. According to the
NRC, the average fuel discharged from
reactors today has reached the high-
burnup threshold, and more of this
fuel is being stored in casks. Based on
laboratory research, NRC is concerned
that high-burnup fuel in dry storage may
have a greater potential for cracking in
the zirconium alloy rod that contains the
uranium fuel.
EPRI has been investigating how to
store high-burnup fuel safely since the
1990s. In 2002, NRC accepted EPRI-
developed technical criteria to license
cask storage of high-burnup fuel for 20
years. “Many casks with high-burnup
fuel are approaching 20 years now,”
Albert Machiels said. “Researchers have
to confirm that the existing criteria will
ensure safe storage over extended periods.”
EPRI and DOE have launched a
demonstration project to confirm the
behavior of high-burnup fuel during
extended storage. EPRI researchers are
modifying a commercial storage cask
with monitoring equipment, which Keith
Waldrop called the project’s “biggest
challenge.” By 2017, the cask will be
loaded with several types of high-burnup
fuel at Dominion’s North Anna Power
Station, and the key parameters including
temperature will be monitored for 10
years at the plant’s cask storage facility.
Rods from the cask will be tested and the
results compared to those from tests prior
to storage to identify any changes. “The
results will enhance the technical basis
for longer-term storage of high-burnup
fuel,” said Waldrop.
“We know that as spent fuel cools,
temperature and radiation decrease; there-
fore, the potential for fuel degradation is
reduced as well,” said Machiels. “There
will be a time when conditions are mild
enough that any degradation is unlikely.
We are focused on aging management to
make sure that the systems protecting the
spent fuel will perform properly over all
the time they’re needed.
Steam Generator Fouling
Using a chemical dispersant,
nuclear plant operators have reduced
the accumulation rate of iron in steam
generators by about 20%, enhancing
plant performance and reliability.
In nuclear plants, buildup of iron-
based particulates in steam generators
(fouling) can lead to corrosion and other
performance problems. Since the 1990s,
EPRI and other industry stakeholders
have developed and successfully
field-tested the dispersant polyacrylic
acid, which helps prevent particulate
deposition on component surfaces,
making them more likely to be removed
from steam generators via blowdown.
Today, operators at 21 plants inject the
chemical into their feedwater systems,
when the facility is either online or offline
for shutdowns and layups.
EPRI assessed seven plants’
experiences with polyacrylic acid from
2009 to 2014, finding iron removal rates
in online applications 7–8 times greater
than rates without dispersant. Most units
using dispersant online also improved
steam generator heat transfer efficiency,
increasing steam pressure by as much
as 0.5% (21–35 kilopas). Evaluation
of applications offline demonstrated
the effectiveness of starting injection at
high-temperature conditions just prior to
shutdown.
The above items can be found at
. Contact: email:
.
