2  Sources  of  long-lived  radionuclides  in
the  Baltic  Sea  sediments

The  most  remarkable  event  affecting  the  quantities ­
  of  artificial  radionuclides  in  the  Baltic  Sea
sediments  was  the  accident  at  the  Chernobyl
Nuclear  Power  Plant  in  April  1986.  The  global  fallout ­
  from  atmospheric  nuclear  weapons  tests,  as
well  as  discharges  from  the  reprocessing  plants
in  Western  Europe  and  from  nuclear  facilities  in
the  Baltic  Sea  region,  have  had  markedly  smaller
consequences  for  radionuclide  concentrations  in
sediments,  especially  in  the  northern  parts  of  the
Baltic  Sea.
The  Chernobyl  accident  was  not  the  first
event  resulting  in  the  dispersion  of  artificial
radionuclides  into  the  atmosphere.  Atmospheric
nuclear  weapons  tests  giving  rise  to  radioactive
pollution  of  the  air,  and  subsequently  of  the
earth’s  surface  and  the  marine  environment,
were  conducted  beginning  in  1945.  Most  of  the
tests  were  carried  out  during  1955-1958  and
1961-1962.  One  of  the  test  sites  was  Novaya

Zemlya  in  the  former  USSR.  By  late  1962,
the  tests  were  reduced  significantly  owing  to
the  signing  of  the  Nuclear  Weapons  Test  Ban
Treaty  of  1963,  and  since  1980  no  atmospheric
testing  has  been  conducted  in  the  northern
hemisphere.  The  total  depositions  of  weapons
test  Cs-137  and  Sr-90  into  the  Baltic  Sea  have
been  estimated  at  900  TBq  and  600  TBq,
respectively  (decay  corrected  to  1991).
Chernobyl  Accident
On  26  April  1986,  a  severe  accident  occurred
at  the  nuclear  power  plant  of  Chernobyl,  in
the  former  USSR.  The  accident  resulted  in
widespread  contamination,  mainly  by  1-131,
Cs-134,  and  Cs-137.  Owing  to  its  long  half-life,
only  Cs-137  is  currently  of  interest.
Global  fallout
Beginning  with  the  use  of  nuclear  weapons
at  the  end  of  the  Second  World  War,  artificial
radionuclides  were  transported  towards  the
upper  atmosphere.  This  continued  on  a  far
greater  scale  during  the  atmospheric  testing
of  nuclear  weapons  until  the  1960s.  The
radioactive  material  released  was  distributed
worldwide  via  the  atmosphere  and  ultimately
precipitated  down  to  land  or  sea.
Reprocessing  plants
Reprocessing  plants  are  a  part  of  the  so-called
nuclear  fuel  cycle.  The  Western  European
plants  are  located  in  the  UK  (Sellafield)  and
in  France  (La  Hague).  Used  fuel  rods  from
nuclear  power  plants  are  processed  physically
and  chemically  in  order  to  recover  unused  fuel.
This  has  resulted  in  regulated  discharges  of
effluents  containing  numerous  radionuclides
into  the  marine  environment  that  peaked  in  the
1970s  and  1980s.  Currently,  such  discharges
have  decreased  considerably.
Nuclear  facilities
Nuclear  facilities  comprise  mainly  nuclear
power  plants,  fuel  reprocessing  plants,  fuel
fabrication  plants,  radioactive  waste  handling
factories,  and  certain  research  institutes  and
military  installations.  These  facilities  handle
radionuclides,  some  of  which  may  be  released
into  the  environment.

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