Bulletin 2/2010 - Siempelkamp NIS

With Siempelkamp back
to a greenfi eld
Experimental nuclear power plant of Kahl
prior to dismantling
MThe dismantling of systems and
buildings completely to a greenfi eld
is supposed to return the site to its original
condition. The proof that no more radioactivity
remains is the requirement for a
facility to be withdrawn from the ambit of
the Atomic Energy Act.
In the case of VAK the actual dismantling
of the plant began after the last fuel
elements were removed in 1989 and
the approval for the decommissioning
according to the Atomic Energy Act was
received.
Through nuclear fi ssion and after many
years of operation, certain operational
systems are exposed to radiation. Therefore,
precise and plant-specifi c planning of
the dismantling process is indispensable.
The impact on man and environment must
to be ruled out.
Only after the detailed assessment and
approval by the authorities, dismantling
measures and modifi cations may com-
mence. Reviewers assigned by the nuclear
regulatory authority monitor the compliance
with and abidance by the
regulations.
The underwater and remotely-handled
disassembly of the reactor pressure vessel
(RPV) and its internals represented the
highlight of the dismantling process. The
thick-walled steel of the RPV was cut into
pieces with a water-jet cutter and then
packed in special containers. This work
was carried out between November 1999
and Mai 2000.
Safe and effective: NIS activities
for the dismantling process of VAK
Dismantling of the fuel element
storage pool
During the operation of the reactor, the
fuel element storage pool was used to
SIEMPELKAMP | NUCLEAR TECHNOLOGY
How can a nuclear facility be dismantled all the way to a greenfi eld
without risking radiation exposure? For 15 years, NIS Ingenieurgesellschaft
has been involved in the dismantling of the experimental
nuclear power plant of Kahl (Versuchsatomkraftwerk Kahl – VAK).
With this work NIS has set a milestone in nuclear technology.
For the fi rst time, a nuclear power plant with an operation time
of almost 25 years is completely dismantled.
By Bernd Truetsch
handle and store spent fuel elements.
The pool was always fi lled with water
because water has the good characteristic
to contain radioactive radiation. Compared
to today's designs, where the
pool is lined with stainless steel, the
storage pool at the VAK was tiled. The
surface area had the dimensions of 4.10 m
x 5.00 m, the pool's height amounted to
7.82 m.
For the dismantling process the NIS team
used a conventional concrete saw. In this
way the storage pool was cut into transportable
reinforced concrete segments
with a weight of approx. 5 t.
Dismantling of the biological shield
The biological shield is a massive cylindrical
concrete structure placed around
the reactor pressure vessel (RPV). This
structure absorbs the radioactive
radiation from the RPV. With advancing
operation, the steel and concrete parts
became radioactive themselves so that