Concentration of radiocaesium in grain following the Chernobyl accident

Radioactivity measurements and dose assessments in Hungary after the Chernobyl accident have shown that the consumption of baker's ware contributes significantly to the internal dose of man. Flour and bread have been contaminated mainly due to radiocaesium deposition onto the of cereals at the end of April and beginning of May, 1986. Because of the different seasonal and growing conditions of biomass, the interception fraction of the standing winter wheat became higher than that of the summer wheat. Therefore, the contribution of grain to the internal dose was relatively high in Hungary where near to 90 per cent of flour and bread is produced from winter wheat in comparison with other countries. The average concentration of 137Cs in winter grain harvested in summer 1986 was 32 Bq/kg with a range of 11-140 Bq/kg. The bran contained almost half of the total radiocaesium of the grain with about 20 per cent of the weight. The 40K concentration of grain was 149 Bq/kg. The 137Cs concentration in white bread commonly used in Hungary was 22 Bq/kg in average. The concentrations found in bread samples from the whole country showed a high variation due to the uneven deposition of radioactive substances. The 137Cs concentration in winter grain was 0.0075±0.0017 Bq/kg normalized to 1 Bq/m2 deposition density. The 137 Cs concentration in grain harvested in 1987 or later became less than 1 Bq/kg. It suggests that the root uptake of radiocaesium by cereals must be very small. The per caput committed effective dose equivalent due to consumption of baker's ware was estimated as 50 micro-Sv. (author)