The Chernobyl accident occurred at 01:23 hr on Saturday, 26 April 1986, when the two explosions destroyed the core of Unit 4 and the roof of the Chernobyl reactor building.
During the first 10 days of the accident when important releases of radioactivity occurred, meteorological conditions changed frequently, causing significant variations in release direction and dispersion parameters. Deposition patterns of radioactive particles depended highly on the dispersion parameters, the particle sizes, and the occurrence of rainfall.
The largest particles, which were primarily fuel particles, were deposited essentially by sedimentation within 100 km of the reactor. Small particles were carried by the wind to large distances and were deposited primarily with rainfall.
The radioactive plume was tracked as it moved over the European part of the Soviet Union and Europe. Initially the wind was blowing in a north-western direction and was responsible for much of the deposition in Scandinavia, the Netherlands and Belgium and Great Britain.
In Britain, the first cases of the Mad-Cow Disease can be dated back to 1986, in the same year when the Chernobyl accident occurred.
The ingestion of radionuclides in food is one of the pathways leading to internal retention and contributes to human exposure from natural and man-made sources. Excessive contamination of agricultural land, such as may occur in a severe accident, can lead to unacceptable levels of radionuclides in food.
The radionuclide contaminants of most significance in agriculture are those which are relatively highly taken up by crops, have high rates of transfer to animal products such as milk and meat, and have relatively long radiological half-lives.
However, the ecological pathways leading to crop contamination and the radioecological behaviour of the radionuclides are complex and are affected not only by the physical and chemical properties of the radionuclides but also by factors which include soil type, cropping system (including tillage),climate, season and, where relevant, biological half-life within animals.
The major radionuclides of concern in agriculture following a large reactor accident are iodine-131, caesium-137 (half-life: 30 years), caesium-134 and strontium-90 (half-life: 90 years). Direct deposition on plants is the major source of contamination of agricultural produce in temperate regions.
In the United Kingdom, restrictions were placed on the movement and slaughter of 4.25 million sheep in areas in south-west Scotland, north-east England, north Wales and northern Ireland.
This was due largely to root uptake of relatively mobile caesium from peaty soil, but the area affected and the number of sheep rejected are reducing, so that, by January 1994, some 438,000 sheep were still restricted. In north-east Scotland, where lambs grazed on contaminated pasture, their activity decreased to about 13 per cent of the initial values after 115 days; where animals consumed uncontaminated feed, it fell to about 3.5 per cent.
The Chernobyl accident occurred 15 years ago, nevertheless the caesium-137 (half-life: 30 years) radionuclides and strontium-90 (half-life: 90 years) radionuclides could be the most likely candidates for causing the Mad-Cow Disease in cows and the Creutzfeldt-Jakob Disease in humans.
The scientific community is unaware of these facts partly because they uninformed about the impacts of the Chernobyl accident partly because the British Government isnít concerned to initiate these kind of research.
This can be featured by that fact that the unknown Mad-Cow Problem and Creutzfeldt-Jakob Problem was characterized by as a DISEASE instead of POISONING.
However not a single fact shows that this problem is able to transfer itself from one animal or human to another animal or human (except by actually eating the poisoned animals).
Cseko, PHD student at the Budapest University of
Technics and Economy, Budapest, Hungary, Address: 1032
Budapest, Kiscelli utca 18. Tel: 3613880168