RD&D-Programme 2004 - SKB

When should a deactivated nuclear power unit be decommissioned? International experience
shows a multitude of variants, ranging from immediate and complete dismantling and demolition
to variations of safe enclosure/safestore for an indefinite length of time. The reasons for
these variants are many, and the method chosen must be tailored to prevailing conditions. In
Sweden, dismantling is assumed to take place relatively soon after shutdown and removal of
the spent fuel. This is also the trend that can be discerned internationally. The reasons for such
immediate dismantling differ from country to country. It may be, for example, that there is a
need to use the site for other activities. Other reasons may be so that the expertise that exists at
the plant can be utilized, or to demonstrate that decontamination and dismantling can be carried
out safely and economically.
Dismantling is assumed to take place after a relatively thorough decontamination of the
facility’s process systems. This is done to reduce radiation to the dismantling personnel. If
the plant has low radiation levels from the start, this system decontamination may possibly
be omitted. This is a judgement that has to be made for each nuclear power unit from an
Alara standpoint. When dismantling is carried out, it is assumed in SKB’s studies that system
dismantling is done first and that this takes at least three years. Decontamination of buildings
and dismantling of contaminated building parts then follows. Finally, the conventional inactive
systems and buildings are dismantled and demolished. This is estimated to take about two years,
after which the plant site is restored to an industrial site for other activities. A total dismantling
and demolishing time of about six years after removal of the spent fuel, which takes about two
years, is judged to be the shortest possible decommissioning period.
24.2 Technology for dismantling
Quite a bit has been done here, mainly in other countries, but SKB is also pursuing its own
technology studies, and the power companies will also eventually conduct studies aimed at
planning for the decommissioning of their own facilities. The decommissioning projects that
have been and are being carried out in various countries have shown that technology exists for
decommissioning and disposal of the waste from all types of nuclear installations. What remains
to be done is optimization and adaptation of existing technology for decommissioning of the
Swedish NPPs.
The technology studies being carried out by SKB are aimed at presenting a possible scenario
for decommissioning of the Swedish NPPs based on technology that exists, and is in use, today.
With the chosen technology as a base, an estimate is also made of what times, costs and waste
quantities are associated with the decommissioning.
When a nuclear power plant has been taken out of service, the site must be restored so that it can
be used for other industrial activities without any radiological restrictions. This must be done in
such a manner that neither the personnel engaged in the decommissioning and dismantling work
nor the general public are exposed to unnecessary irradiation.
The design and licensing process for disposal of the radioactive waste from decommissioning
requires planning on the national level. This planning must be done in cooperation between the
power companies and SKB. Such planning offers advantages with regard to access to special
equipment and specially trained personnel, as well as an opportunities for experience feedback.
The point of departure for planning is that no unit is decommissioned as long as a nearby unit is
still operating. Taken together, this means that the first decommissioning will not be commenced
until some time after 2015, and probably not until a few years into the 2020s. If the operating
time of the NPPs is extended, or if the power companies decide to allow the radiation from the
reactor to decay for a period, dismantling will begin at a later time.
The power companies bear primary responsibility for planning and execution of the dismantling
work. Their responsibility also includes determining which strategy is to be applied regarding
the timing of dismantling and the technology to be used. Treatment of the radioactive waste will
be planned and carried out in cooperation with SKB.
324 RD&D-Programme 2004