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CHEMICAL TREATMENTS TO REDUCE THE TRANSFERT OF CAESIUM RADIOISOTOPES TO THE HUMAN FOODCHAIN AFTER A SERIOUS NUCLEAR ACCIDENT

Objective

The project includes two areas: one regarding the agrochemical aspects and the other, the zootechnic aspects.
The aim of the research was to investigate methods of reducing the transfer of radiocaesium in plants, milk and meat following radioactive deposition after a nuclear accident. Firstly the reduction of translocation of radiocaesium from aerial parts to edible products of crops and, secondly, the reduction of radiocaesium uptake in milk and meat resulting from animal feeding with contaminated fodder were studied.

3 species of plants: barley, wheat and tomato were cultivated in open field in 1989 and 1990 in several plots. At different growing stages they were contaminated through the leaves with varying levels of caesium-134 under controlled conditions to simulate contamination from radioactive fallout. To assess the effectiveness of potassic foliar fertilization in reduction of radiocaesium translocation from the leaves to the grain, contaminated barley and wheat were sprinkled with potassium chloride at varying concentrations. A surfactant was added to the treatment in some of the plots. The tomato crops were treated in a similar manner.

Potassium foliar fertilization significantly reduces radioactivity in the edible parts of tomato plants. Because of this it is possible to develop predictive curves for reduction of radiocaesium contamination. However, the treatment had no effect on the levels of contamination in the barley and wheat grains. The addition of the surfactant had no effect on the translocation factor for tomato but either increased of left unchanged the translocation of radiocaesium to the edible parts of the cereals.

Trials on sheep and dairy cows were carried out to determine the effect of the oral administration of bentonite and ammonium iron (III) hexacianoferrate (II) (AFCF) on the transfer of radiocaesium from feeds to meat or milk. In the initial trial 4 lambs were fed with hay contaminated by radiocaesium from the 28th day onwards. The animals were kept in individual metabolic cages and after a week of adaptation 2 lambs were fed AFCF. AFCF appeared to be effective against the accumulation of both caesium-134 and caesium-137 in the animals bodies. In the second trial 10 adult Sarda sheep were tested for the effectiveness of both AFCF and bentonite. The animals were divided into 5 groups. All groups were initially conditioned for 2 weeks on a diet of hay pellets supplemented with concentrates of minerals and vitamins. After that time 4 groups received radiocaesium contaminated hay pellets from the Chernobyl accident in 2 equal meals a day for 20 days. In addition 2 of these groups received AFCF pellets, 1 group received bentonite pellets and the 4th received neither AFCF or bentonite. All 10 animals were slaughtered after 20 days.

8 milking Friesian cows were divided into 4 groups of 2 animals each. All received soybean meal artificially contaminated with caesium-134 in 2 equal meals a day for 14 days. In addition 2 of the groups received AFCF pellets, 1 group received bentonite pellets and the 4th received neither AFCF or bentonite.

In all of the experiments AFCF showed the highest blocking capacity in reducing the adsorption of caesium in the digestive tract. The mean reduction (compared to the control group) was over 30 times with AFCF and 5 times with bentonite for meat and 11 times with AFCF and 1.5 times with bentonite for milk. When AFCF was administered twice a day its efficacy was almost doubled. In conclusion, in order to reduce the transfer of radiocaesium from forages to meat and milk, both AFCF and bentonite are effective but at a different degree. Immediate use is recommended for best results following pollution from a nuclear accident.
Agrochemical aspects .SP 0 When a serious nuclear accident occurs the radioactive fallout that affects the aerial parts of the vegetation is transferred to the fruits and may involve a serious risk for human health. The destruction of the crops is certainly a drastic and uneconomical remedy. Therefore it is useful to search for better remedies to reduce food contamination. In this research the possibility has been studied to reduce the radiocaesium transfer to the edible parts of some plants by means of foliar fertilization with potassic salts. Three plants species, barley, wheat and tomato are considered.

Zootechnic aspects
The general aim of the research is to study the possible ways to reduce the radiocaesium transfer to meat and milk from feeding contaminated food to livestock. In the first year trials were performed where Ammonium Iron (III) Hexacinoferrate (II), hereafter indicated as AFCF, was administered in two equal doses during morning and evening feeding at the rate of 0.33 g/head/day and 5 g/head/day respectively, to growing sheep and milking cows who received radiocaesium contaminated hay following the Chernobyl accident. The results obtained show that AFCF is an efficacious product in reducing radiocaesium transfer to meat and milk.

The second year research programme has three main scopes:
to study whether higher doses of AFCF would further reduce radiocaesium transfer to meat from feeding contaminated food;
to study the effect of AFCF administration once a day instead of twice a day on radiocaesium transfer to meat and milk from feeding contaminated food to ruminants, as one administration requires less labour particularly for grazing animals;
to find out other efficacious products that can reduce radiocaesium transfer to meat and milk from feeding contaminated materials to ruminants.

In order to attain the above mentioned objectives two trials, one with sheep and the other with milking cows were programmed.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Commissariat à l'Energie Atomique (CEA)
Address
Centre D'études De Cadarache Sere-ders
13113 Saint-paul-lez-durance
France