10 
Mean radiation energy: 
Thickness of the ship’'s hull (Iron) 
The resultant shielding factor: 
0.8 MeV 
20 mm 
> 37 
A geometry correction factor of 0.25, as was ascertained from "in- 
situ"-total Gamma measurements between geometry in open water and 
from container geometry, was taken for the seaweed layer on the 
ship’'s hull. A further model for the control of the calculation of 
the radiation burden based upon the exposition path "residence on 
the sediment”; this gave about the same value. The fouling on the 
light vessel was viewed as being the radiation activity of the 
sediment. As shielding, the radiation absorption of the ship's body 
with 20 mm iron hull thickness was taken into account. 
The radiation load from the seawater amounted consequently to a 
maximum of 0.1 mSv/a (10 mrem/a), that from the seaweed growth re- 
sulting radiation burden 0.6 mSv/a (60 mrem/a). A follow-up investi- 
gation on 14.05. indicated a seaweed activity of 540 Baq/kg. Thereby, 
the radiation load up to that point in time had decreased to a 
third. As the values indicated falling tendencies and a renewed in- 
crease was not to be expected, further investigations could be 
dropped. 
The fouling on the ship’'s hull was taken to be a critical source of 
an external radiation burden for ship's personnel. In the case of 
the light vessel lying on station for two years already, the fouling 
was particularly severely pronounced. This is not the case with mo- 
ving ships. Therefore, the crews aboard light vessels can be regar- 
ded as a eritical group of the population in the case of this expo- 
sure path. 
„2 
Radiation burden on the beach 
On 15.05. in the region of the Lower-Saxony North Sea coast, and on 
21.05. on the Baltic Sea coast of Schleswig-Holstein mud, sand, and 
seaweed samples were taken from the beach area and were investigated 
in the laboratory for total Gamma-radiation, and - in part - inve- 
stigation by Gamma-spectrometry (Table 1). 
The maximum radiation burden for the residence on the beach could be 
estimated from the "Berechnungsgrundlagen” over the Gamma-dose-fac- 
tor for contaminated soil, as 0,01 uSv/h (1 Hurem/h). The peak 
value of the ground contamination of 4000 Bq/m2 near Norddeich 
(mud) served herefor. The sample taking referred to the uppermost 5 
mm, and covered an area of circa 0.25 m2,. 
For the seaweed samples, a maximum specific total Gamma-radioacti- 
vity of eirca 8000 Bq/kg was ascertained as the highest total Gamma- 
radiation activity. The Gamma-spectrometrical analysis showed that