Technology and Operation - Kernkraftwerk Gösgen

pool then increases the storage capacity of
the storage pool inside the reactor building,
which holds approximately 600 spent fuel
assemblies.
The pool cooling system comprises four symmetrically
arranged independent trains with
two trains being connected to a cooling tower
in each case. The heat from the spent fuel assemblies
is eliminated into the outside air via
an intermediate cooling circuit with natural
circulation. This involves the intermediate
coolant flowing through heat exchangers that
are hung inside the storage pool. The heat is
then dissipated to the outside air by natural
circulation via water/air heat exchangers.
With very high outside temperatures and a
large spent fuel inventory in the storage pool,
fans are available to boost the air circulation
in the cooling towers. The first spent fuel assemblies
were loaded into the new storage
pool in mid-May 2008.
Refuelling
Once a year the power plant is shut down for
refuelling. It takes some two to three weeks to
discharge the spent fuel assemblies, reposition
the assemblies remaining in the reactor
core, load the fresh fuel assemblies and to
carry out inspection and maintenance work.
The fuel assemblies discharged from the reactor
core are first placed in high-density
racks in the spent-fuel reactor storage pool.
There are more than 600 storage positions in
this pool, which can take not only spent fuel
assemblies but also instrumentation thimble
tubes, control elements and tools. In the
compact storage pool, the radiation and decay
heat are allowed to subside before the
fuel assemblies are conveyed in special
transport casks to the spent fuel storage
Plant design and special technical features
Fuel assemblies being replaced during the
annual maintenance outage.
building. The decay heat is eliminated via a
dedicated cooling system connected up to
the compact storage pool. The spent fuel assemblies
can remain in interim storage in
the compact storage pool for a period of several
years.
The sickle-shaped annular space between
the outer reactor building shell and the containment
serves to house and protect the
loading and transfer pool, the access shaft,
the emergency and regular cooling system,
the fresh fuel store and the waste gas delay
bed. The spent fuel assemblies are loaded
into the transport casks in the loading and
transfer pool. They are moved from the compact
storage pool to the loading and transfer
pool by a remote-controlled transfer facility to
this end. The transport casks are moved into
and out of the annular space via the access
shaft.
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