Interception, retention and translocation under greenhouse conditions of radiocaesium and radiostrontium from a simulated accidental source

The behaviour of radioactive aerosols released from a severely damaged nucl ear reactor and deposited on cereals was simulated under controlled conditi ons. Cs-137- and Sr-90-labelled aerosols were generated by volatilisation a t high temperature of an artificially spiked pellet of depleted UO2. After cooling and maturation the aerosols were allowed to deposit on spring wheat (Triticum aestivum L. var. Arbon) cultures grown on lysimeters under green house conditions. At the time of contamination the wheat plants were at dif ferent stages of development, from early vegetative growth (two leaves) unt il nearly mature (end of flowering). The estimated interception coefficient (mu) amounted to 13.1 m(2) kg(-1); such a high value may be explained by t he experimental conditions that created an over-saturated atmosphere during the contamination process and wet leaf surfaces. The first simulated rain, applied 6 days after the contamination, removed four times more Cs-137 (54 % +/- 12 of the intercepted radionuclides) than Sr-90 (15% +/- 20) from the aerial parts. At harvest approximately 2% of the Sr and less than 1% of th e Cs initially intercepted by the aerial parts is recovered for plants cont aminated during the early development stages. A significantly higher propor tion of the intercepted activity is still present for plants contaminated i n the late development stages. The translocation to grains (TLF) increases when deposit occurs closer to the mature stage of the plant. The initial de crease of TLF values that we observed for strontium contamination in the ea rliest development stages is most probably due to the contribution of root uptake. Ploughing and re-sowing after the first rain, applied as a counterm easure reduced the Cs-137 content in leaves and steins at harvest approxima tely 3 times but had no effect on the Sr-90 content in vegetative organs. I t reduced the Cs-137-contarnination level in edible parts (grain) by a fact or of 2 compared to the unploughed control, but doubled the Sr-90 content. (C) 2001 Elsevier Science B.V. All rights reserved.