The consequenses in Sweden of the Chernobyl accident. Karl J ...

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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.