Dry Used
Fuel
Storage
System
William Murphy, Duke Energy.
William Murphy
William Murphy is a Reactor Systems
Engineer at Duke Energy-operated
Catawba Nuclear Station. He has 10
years of experience
in used nuclear fuel
storage and was
the lead engineer
responsible for
transitioning
Catawba to the NAC-
MAGNASTOR ultra-
high capacity storage
system. Prior to dry
fuel storage work, he
served as a criticality
safety analyst and
special nuclear
material controls
and accountability
engineer. William
holds a degree in Nuclear and
Radiological Engineering from the
Georgia Institute of Technology and
a Professional Engineering license in
South Carolina.
Nuclear Energy Institute’s Top Industry
Practice (TIP) Awards highlight the
nuclear industry’s most innovative
techniques and ideas.
This innovation won the 2014 Nuclear
Fuel Process Award.
The team members who participated
included: William Murphy, Program
Manager Catawba ISFSI;
Scott Friend, System Engineer Catawba
ISFSI; Jochen Krist, Catawaba ISFSI
Technical Support/Job Sponsor; Craig
Bigham, Catawba Reactor Engineering
Manager; Bud Peeler, Project Manager.
Summary
In May 2013, Catawba Nuclear Station
successfully loaded 37 pressurized water
reactor (PWR) used fuel assemblies into
the NAC International MAGNASTOR
®
dry storage system. This was the first-
ever loading of more than 32 PWR fuel
assemblies in a welded canister dry storage
system. Duke Energy operates Catawba
Nuclear Station’s two Westinghouse PWRs
at a site near York, South Carolina. Unit 1
has been in operation since January 1985
and Unit 2 since May 1986. Each unit has
a standalone spent fuel pool (SFP) with
a licensed capacity of about 1,400 fuel
assemblies. The pools reached capacity in
the mid- 2000s, requiring implementation
of dry used fuel storage
technology. In 2007,
Catawba deployed the
NAC-UMS® dry fuel
storage
technology.
Catawba loaded 24
NAC-UMS® systems
between 2007 and
2011, each with a
capacity of 24 PWR
used fuel assemblies.
This system had been
used
extensively
in industry prior to
Catawba. Though a
proven and reliable
technology,
the
relatively low capacity of the NAC-
UMS® system presents challenges
with long-term storage of used fuel at
Catawba. Off-site disposition of the
site’s used fuel inventory will likely
not occur for many decades. Additional
renewal of the site operating license
is plausible. The Independent Spent
Fuel Storage Installation (ISFSI) land
area was designed to support used fuel
storage for a single renewal period and
cannot be expanded due to facility and
geographic limitations. As the inventory
of older, decayed used fuel is loaded
into dry cask systems, newer and hotter
fuel, beyond the capabilities of the NAC-
UMS® system to store, will need to be
loaded. In 2010, Catawba elected to
transition to the MAGNASTOR
®
dry
fuel storage technology. The new system
incorporates
multiple
evolutionary
improvements from its predecessors. In
the same concrete cask outer diameter
as NAC-UMS®, the MAGNASTOR
®
system stores thirty-seven PWR used
fuel assemblies – an increase of 54%.
Transition to the MAGNASTOR
®
system
was controlled as a station major project.
A multidisciplinary team, consisting
of personnel from various functional
areas, ensured that required station
modifications, calculation changes,
regulatory requirements and field testing
were completed prior to loading. Changes
in canister processing from NAC-UMS®
to MAGNASTOR
®
system warranted
new technologies to maximize efficiency
and minimize personnel exposure. EMS
Solutions, Inc. supplied the E1000LT
Vacuum Drying Skid (VDS), which
performs all ancillary activities from
weld hydrostatic testing to helium
backfill from a single location. Major
station modifications include:
A Vertical Concrete Cask (VCC)
construction yard exterior to the site
protected area.
Design, fabrication and installation
of MAGNASTOR Transfer Cask
(MTC) annulus flush and cooling
system, including modifications in
the spent fuel buildings to connect
the MTC to the plant spent fuel pool
cooling system.
Electrical, air and gas supply to
the E1000LT VDS, in addition to
installed piping to connect the VDS
to the canister.
After three field testing exercises
from 2012 to 2013, Catawba completed
loading of industry’s first ultra-high
capacity storage system in May 2013.
Operating experience from Catawba was
applied to subsequent MAGNASTOR
®
loadings at McGuire Nuclear Station and
Zion Nuclear Station.
Safety
The increased storage capacity
of MAGNASTOR
®
systems results
in fewer overall loading evolutions
required to maintain adequate SFP
operating margins. As a result of this
transition, 11 fewer loading evolutions
are projected to be required between
2013 and 2020 – a reduction of more
than 30 percent. Dry cask loading
evolutions present challenges in nuclear
safety (fuel handling), radiological
safety (personnel exposure during cask
(Continued on page 56)
54
NuclearPlantJournal.com Nuclear Plant Journal, July-August 2014
