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Type and effects of the radiation released

More than 40 different radionuclides escaped from the stricken reactor, notably in the first ten days following the accident.

For an analysis of the accident's consequences, the most significant of these are iodine (I-131), cesium (Cs-137) and strontium (particularly Sr-90). It is currently assumed that about 50 per cent of the reactor's iodine content and 30 per cent of the cesium was released into the atmosphere.

The hot gases of the burning graphite transported the radioactive substances to heights of over 1500 meters. Because of variable weather conditions in the days following the accident, radiation also spread over large parts of Scandinavia, Poland and the Baltic States, as well as southern Germany, Switzerland, northern France and England.

In Belarus, Russia and Ukraine, local showers spread the radiation very unevenly. For example, the area around Gomel in Belarus to the northeast of Chernobyl was as severely contaminated as strips of land in the immediate vicinity of the reactor. The Ukrainian city of Narodichi was split by the radioactive fallout into an uncontaminated western half and a severely contaminated eastern half. Severely contaminated "hot spots" often lie close to areas that are only mildly contaminated. Local maps showing contamination are therefore all the more important for the population. They can be studied at local authority offices.

In terms of radioactive contamination, iodine, with a half-life of 8 days, posed the greatest risk in the first few weeks. In Belarus in the week following the accident, increased iodine levels were measured almost everywhere. The human body cannot distinguish radioactive iodine from the natural, stable element, and stores it primarily in the thyroid gland.

Radioactive cesium, with a half-life of 30 years, is still the most widely dispersed isotope. Between 125 000 and 146 000 km2 are contaminated with cesium. There is also concern over long-term contamination with strontium (Sr-90), which has a half-life of 29 years, and plutonium (Pu-241) and its various decay products: some of these have a half-life of 24 000 years.

The consequences of the Chernobyl accident for the environment cannot be described in terms of spatial distribution alone. Cesium, strontium and plutonium in the soil can enter the food chain via crops and livestock. Other pathways of distribution include erosion by the wind, forest fires, cultivation of the soil, and transport by rivers.

According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR): Source and Effects of Ionizing Radiation, Annex J, S. 457 ff., UNSCEAR 2007 Report to the General Assembly, New York, 2007

Автор: 
Александр Сирота

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