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NuclearPlantJournal.com Nuclear Plant Journal, July-August 2014
processing, including neutron radiation),
and industrial safety (heavy lifts of the
empty and loaded system, placement of
lids, working on elevated surfaces, and
operation of heavy equipment such as the
vertical cask transporter and automated
welding system). Reduction in the overall
number of loading evolutions for the
same population of fuel decreases the risk
of safety events.
Safety benefits are also realized in
long-term storage of MAGNASTOR
®
systems at the ISFSI. Increasing the
density of used fuel stored results in
improved off-site dose characteristics as
the fuel is shielded by its neighboring
assemblies. Use of the high-density
MAGNASTOR
®
system will minimize
the used fuel storage footprint at the
Catawba site. This will be particularly
beneficial after the cessation of power
operations, if no used fuel is shipped
off site, as the smaller footprint reduces
the security profile and maximizes the
amount of land that can be reclaimed for
general use. Presuming no fuel is shipped
off site over the lifetime of the station, the
ultimate size of the stand-alone ISFSI will
be minimized, allowing for the greatest
amount of land to be reclaimed for general
use and reducing the security profile of
the site. The MAGNASTOR
®
system uses
a single composite shielding/structural
closure lid for confinement, along with
a light (approximately fifty pounds)
closure ring for confinement redundancy.
Most dry storage systems require two lids
to be installed. Lid placement is a critical
lift evolution (weighing in excess of five
thousand pounds), with accompanying
safety challenges. The single lid design
constitutes a design enhancement with
major positive safety implications. The
E1000LT VDS requires only a single set
of connections to the canister for all of
its processing functions (i.e., one set of
boom lines to the vent and drain ports,
as well as thermocouple connections
to the MTC). Compared to multiple
separate pieces of equipment for each
function (e.g., hydrostatic testing,
vacuum drying, etc.), this configuration
minimizes occupancy time on top of
the loaded system, reducing personnel
exposure. Elimination of multiple
equipment manipulations also reduces
the probability of human performance
induced component events.
Cost Savings
The cost to load a MAGNASTOR
®
system (hardware, personnel, and
consumables) is essentially the same as
the lower-capacity NAC-UMS®. Overall,
an estimated cost reduction of $4,500
per fuel assembly stored can be realized
from this transition, or savings of $3.3
million between 2013 and 2020 for the
required inventory of fuel. Cost savings
will continue to grow past this timeframe
as more systems are loaded. Additional
cost savings will be realized by reducing
the total number of ISFSI storage pads
required, as well as the ultimate size of
the ISFSI at station end-of-life.
Innovation
The MAGNASTOR
®
system was
licensed by the Nuclear Regulatory
Commission in 2009. Duke Energy
supported NAC International in obtaining
initial regulatory approval. It is the first
ultra-high capacity (37 PWR or 87 Boiling
Water Reactor assemblies) storage system
available in the industry. Deployment of
the MAGNASTOR
®
system at Catawba
is a first-of-a-kind activity, requiring
contributions from multiple station and
corporate organizations. Industry and
regulatory efforts to characterize dry fuel
storage systems for extended storage
periods have identified the desire to
obtain system data during loading
Evolutions. The E1000LT VDS has
onboard data logging capabilities,
allowing for automated detailed record
of canister conditions, including: MTC
cooling system performance, drain down
flow rates, water temperature, vacuum
drying and backfill conditions, and
evolution durations. The E1000LT VDS
gathers much more key parameter data
than typical dry storage data logging
systems. These data can be made available
for use in detailed best-estimate computer
simulations of fuel conditions during
vacuum drying, thereby demonstrating
margin to safety and regulatory thermal
limits and establishing initial conditions
for analyses of fuel mechanical
performance during extended storage.
Productivity/Efficiency
Loading one canister is a two-week
evolution from preparing an empty
system to placing the loaded system
in the ISFSI. A loading evolution is
significant for an operating nuclear
facility, requiring resources and priority
from multiple station organizations
(Fuel Handling, Welding, Radiation
Protection, Chemistry, Engineering,
Operations and Security). In addition,
vital plant equipment (notably spent fuel
pool cooling) must be formally protected
during loading to preclude equipment
issues. Obviating the need for 11 loading
evolutions over seven years constitutes
22 weeks of regained productivity, not
including the time required to mobilize
and demobilize equipment from the spent
fuel buildings. Additional efficiency
gains will be realized beyond 2020 as
additional ultra-high capacity systems
are loaded. The previously-mentioned
single closure lid design decreases post-
backfill cask processing time by several
hours because the secondary confinement
boundary (a 50-pound closure ring) is far
easier to install and orient for welding
than a second complete lid. The E1000LT
VDS performs all of the following
functions:
MTC annulus cooling system
temperature monitoring.
Dry Used...
(
Continued from page 54)
MAGNASTOR
®
VCC Docked with
Vertical Cask Transporter.
