POWER July 2015 - 59

NUCLEAR LIFECYCLE
One advantage of the phased approach is
that it allows flexibility. As the project progresses,
changes can be implemented more
easily when licensing for future phases has
not been finalized. Time is allowed for additional
information to be gathered so later
work packages can be constructed more
accurately, using up-to-date details. The
phased approach also provides structure so
that large, complex technical systems can
be methodically dismantled using a step-bystep
process.
The Stade Case
As an example, Brendebach offered details
on the Stade NPP decommissioning project.
The station is located northwest of Hamburg
on the Elbe River. It operated from 1972 to
2003 when E.ON Kernkraft GmbH-majority
owner and operator of the plant-shut it
down for economic reasons. The 630-MW
single-unit facility included a Siemens pressurized
water reactor (PWR).
The Stade decommissioning utilized a
four-phase approach for immediate dismantling.
A PWR has both a primary system,
which is exposed to radioactive contamination,
and a secondary system, which is not
exposed to contamination and is very similar
to other non-nuclear steam plants.
Once the plant was permanently taken offline,
a transition period began. That period
lasted roughly a year and a half and allowed
comprehensive preparations to be made for
the disassembly and removal of plant components
and systems, such as planning for
the removal of spent fuel rods from the site.
However, dismantlement could not begin until
government regulators granted the permit
for decommissioning.
Once authorized, phase one of the decommissioning
process included the removal
of items that ultimately created more room
for subsequent work. Reactor containment
structures may look large from the outside,
but space is tight on the inside. At Stade, the
control rod assemblies were taken out during
this phase to free up space inside the reactor
chamber. The flood tanks-previously
used to feed the primary loop during startup
and shutdown-were removed, as were the
pressurized emergency cooling tanks located
inside the containment. Some secondary
system components, such as turbine and
generator components, steam and feedwater
systems, and the emergency diesel generator,
were also removed.
Removing the steam generators and primary
coolant piping and pumps was the
main focus of the second phase of decommissioning,
which took more than two and
a half years. Phase three involved dismantlement
of some of the most contaminated
July 2015 | POWER
Ignalina: Decommissioning Chernobyl's Big Sister
The Ignalina Nuclear Power Plant (INPP)
is located in eastern Lithuania near
Visaginas-a town of more than 20,000
people founded in the mid-1970s for
workers constructing INPP and for the
purpose of supporting the plant. INPP
operated two RBMK-1500 water-cooled
graphite-moderated channel-type power
reactors, which is the same reactor type
that was installed at the Chernobyl Nuclear
Power Plant, although that plant
had four 1,000-MW reactors.
Following the Chernobyl accident in
1986, plans for additional units at INPP
were scrapped, even though Unit 3 was
estimated to be about 60% complete. The
two finished units were allowed to operate,
albeit at a reduced thermal power
output.
components, such as the reactor pressure
vessel and the fuel racks used in the spent
fuel pool. These components cannot be
decontaminated because they become radioactive
themselves after years of neutron
exposure while the plant is in operation.
Concrete shielding and slabs were also removed
during this phase.
The final phase of nuclear D&D at Stade
will involve the removal of all remaining
systems and components. Cranes, ventilation
systems, and water treatment components
will be dismantled during this stage.
The remaining buildings will be cleaned
and decontaminated so that the radiation
control area can be eliminated. At that
point, the site will be released from regulatory
control and conventional dismantling
will continue. In the end, the area will be
restored to green fields and released for
unrestricted use. The project is scheduled
to finish by 2018.
Interim storage of low- and medium-level
radioactive waste from the site has been accomplished
through the use of a temporary
storage facility built adjacent to the Stade
plant. The facility was constructed with the
expectation that the German federal government
will provide a permanent waste disposal
facility sometime within the expected
40-year service life of the structure. (For another
case study, see the sidebar.)
Cutting and Packaging
A lot of planning and consideration must
be given to radioactive waste disposal when
decommissioning and dismantling a nuclear
plant. Material that can't be decontaminated
www.powermag.com
During the process of preparing for accession
to the European Union (EU) and
North Atlantic Treaty Organization (NATO),
and at the urging of the international
community, the Lithuanian government
agreed to retire INPP. Unit 1 was permanently
shut down in December 2004, and
Unit 2 was removed from service in December
2009. As part of the agreement,
the EU is funding a portion of INPP's decommissioning.
POWER
received an update on INPP's decommissioning
plan and progress from SE
INPP Director General Darius Janulevicius.
Read details and see several photos of the
project in the supplement to this story,
" Ignalina: Decommissioning Chernobyl's
Big Sister, " associated with this issue in
the archives at powermag.com.
must be disposed of at a radioactive waste
disposal facility, so minimizing the size and
volume of material, that in many cases is
irregularly shaped, can be tricky. Many of
the components are very large, such as the
reactor vessel (RV) and reactor vessel head
(RVH), and usually can't be removed from
the facility intact.
Westinghouse Electric Co. LLC has been
engaged in a project near Madrid, Spain, at
the José Cabrera Nuclear Power Station (also
known as the Zorita plant). The unit was an
early vintage 160-MW PWR. It operated
from 1968 to 2006, when it was closed by
ministerial order.
Although Unión Fenosa operated the
plant, ownership was transferred to Empresa
Nacional de Residuos Radiactivos S.A.
(ENRESA) for decommissioning. ENRESA
contracted with Westinghouse to dismantle
and segment the RV internals in 2010. Following
successful completion of the project,
Westinghouse was selected to dismantle and
segment the RV and RVH in 2013.
To begin the RV and RVH project, Westinghouse
spent the first six months conducting
engineering studies, completing design
work, and manufacturing equipment needed
for the job. Detailed 3-D modeling was used
to design tools and determine the optimal
strategy for cutting and disposing of waste.
Radiological conditions and packaging constraints
were considered along with many
other factors.
After thorough evaluation, mechanical
cutting was the method chosen for segmentation.
This is similar to the strategy used at the
Zion plant in Illinois, which was covered in
59
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POWER July 2015

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