Apr 26, 1986 - is within this region. The total 1 3 7 Cs fallout in. Sweden during the 1960s was about 3,500 Bq m"2. The Swedish Radiation Protection Institute.
Key note address: The consequenses in Sweden of the Chernobyl accident. Karl J Johanson Department of Radioecology, Swedish University of Agricultural Sciences, box 7031, S-750 07 Uppsala, Sweden
T h e accident in unit 4 o f the Chernobyl nuclear
regions more o f the radioactive material was
power plant occurred at 1.23 a.m. on 26 A p r i l
intercepted by the coniferous trees and by the
1986. Substantial amounts o f the radioactive
dwarf shrubs, mosses and lichens.
material were released into the atmosphere, for
T h e ground deposition o f the radiocesium in
example about 10 to 12% of the core content o f
Sweden was measured by aircraft
radiocesium. D u e to the high temperature the
with 4 N a l ( T l ) crystals. T h e measurements
plume rose to high altitudes - several hundreds
were performed by the Swedish Geological
o f meters to more than 1,000 meters.
Company ( S G A B ) and they also produced a
T h e plume direction in the early phase was
map o f the
1 3 7
equipped
C s deposition expressed as B q
towards Scandinavia over the Baltic states at a
m (Figure 1). T h e deposition in Sweden is
height o f about 1,500 m. T h e plume reached
very heterogeneous. In most o f Sweden the de-
Scandinavia on 27 A p r i l but was not detected
position is below 3,000 B q nv . A l o n g the
before the morning o f 28 A p r i l when the per-
Baltic coast from Gavle up to U m e å there is a
sonnel contamination control at the Forsmark
rather high
nuclear power plant in the central part o f Swe-
there are more than 60,000 B q m . In a rather
den gave the alarm. D u r i n g the night between
large part o f Sweden from south o f U m e å to
28 and 29 o f A p r i l a heavy rainfall occurred in
the mountain region in the western part o f Swe-
some regions o f the central and northern parts
den there are
o f Sweden. M u c h o f the radioactive material in
30,000 B q m . T h e
2
2
I 3 7
C s deposition. In some areas 2
1 3 7
2
C s depositions o f more than main problems
with
the air was washed out and thus deposited on
radiocesium for reindeer husbandry in Sweden
the ground or vegetation. In the northern part
is within this region. T h e total
of the most contaminated region in Sweden
Sweden during the 1960s was about 3,500 B q
there was still snow on the ground and ice on
m" .
the lakes. In the southern part the grass had
1 3 7
C s fallout in
2
T h e Swedish Radiation Protection Institute
just started to grow. T h e interception on vege-
decided in M a y 1986 on the intervention level
tation at farmland was therefore rather small
for radiocesium. T h e primary aim was to re-
and most o f the radioactive material was depos-
strict the intake o f radiocesium by food to
ited on ground. In the woodland and mountain
people in Sweden so that the additional dose
Rangifer, Special Issue No. 3, 1990.
9
equivalent did not become higher then 1 mSv
determined to guarantee that no reindeer meat
per year. For single years 5 mSv could be
found in shops had
accepted. T h i s is in accordance with the re-
above the intervention level.
commendation o f I C R P . T h e Swedish inter-
The
1 3 7
1 3 7
C s activity concentration
C s activity concentrations in various
vention level was placed at 300 B q o f C s for
kinds o f animal material show very large varia-
all food including reindeer meat. I n spring
tions. I n reindeer,
1987 the level was changed to 1,500 B q o f
range form 100 to 40,000 B q k g , in moose
C s per k g for reindeer meat as well as for
from 20 to 3,000 B q kg" , in roe-deer form 20
B 7
1 3 7
1 3 7
C s activity concentrations -1
1
game animal meat, fish, berries and mush-
to 12,000 B q k g
rooms. A radiation dose o f 1 mSv per year
nearly zero to 200 B q kg" . These are mean
corresponded i n 1987 to an yearly intake o f
values which have been found in a relatively
about the
137
50,000 B q o f Cs/
134
1 3 7
C s calculated with
C s ratio o f 1987. D u r i n g 1986 the
1
and in cows' milk form 1
large area. H i g h e r values can be found in individual animals.
C s activity concentration in samples from
T h e main problems still existing in Sweden
nearly all reindeer slaughtered in Sweden were
as a result o f the Chernobyl fallout are associ-
1 3 7
ated with the reindeer and game animals, especially roe deer, moose and fish. F r o m the radiation protection point o f view, the remaining problem in Sweden due to the Chenobyl accident is that many people within the most contaminated regions eat large quantities o f meat form reindeer, game animals and fish. Some o f them will receive a dose equivalent o f around 5 mSv per year due to intake o f radiocaesium by foodstuffs. T h e problem will be very longlasting, in fact no decrease in the
1 3 7
C s activity
concentrations have been found i n , for example, roe deer and moose during the first 3 years after Chernobyl. K e y words: radioactivity, fallout, radiocesium
Fig. 1. The deposition of C s (kBq per m ) in Sweden. Measurement performed by the Swedish Geological Company. 137
10
2
Rangifer, Special Issue No. 3, 1990.
