Long-term effects
The accident resulted from agricultural use was withdrawn about 5 million hectares around the plant created a 30-kilometer exclusion zone have been destroyed and buried (buried heavy machinery), hundreds of small settlements.
Before the accident in the reactor of the fourth unit was 180-190 tons of nuclear fuel (uranium dioxide). According to estimates, which are currently considered the most reliable in the environment was thrown from 5 to 30% of this amount. Some researchers have disputed these figures, referring to the available photographs and eyewitness observations, which show that the reactor is almost empty. However, it should take into account that the amount of 180 tons of uranium dioxide is only a fraction of the volume of reactor. The reactor was mostly filled with graphite, it is believed that he was burned in the first days after the accident. In addition, part of the contents of the reactor melted and moved through the faults at the bottom of the reactor vessel beyond.
In addition to the fuel in the reactor core at the time of the accident contained fission products and transuranic elements - various radioactive isotopes that had accumulated during the reactor operation. It is they who pose the greatest radiation hazard. Most of them stayed inside the reactor, but the most volatile components have been thrown out, including:
All the noble gases contained in the reactor;
About 55% of iodine in a mixture of vapor and particulate matter, as well as of organic compounds;
Cesium and tellurium in the form of aerosols.
The total activity of substances emitted into the environment, was, according to various estimates, up to 14 × 1018 Bq (14 EBq), including
1,8 EBq iodine-131,
0,085 EBq cesium-137,
0,01 EBq strontium-90 and
0,003 EBq isotopes of plutonium;
The share of the noble gases accounted for about half of the total activity.
Were contaminated more than 200 000 km ², roughly 70% - on the territory of Belarus, Russia and Ukraine. Radioactive materials were distributed in the form of aerosols, which are gradually deposited on the surface of the earth. Noble gases are dispersed in the atmosphere and does not contribute to pollution of surrounding stations in the region. Contamination was very uneven, it depended on the direction of the wind in the first days after the accident. The most severely affected areas in which at that time a shower of rain. Most of the strontium and plutonium fell within 100 km from the station, as they were held mainly in the larger particles. Iodine and cesium have spread to the wider area.
In terms of population exposure in the first weeks after the accident most dangerous radioactive iodine, which has a relatively low half-life (eight days), and tellurium. Currently (and in the coming decades) the greatest danger is posed by isotopes of strontium and cesium with a half life of about 30 years. The highest concentrations of cesium-137 found in the surface layer of soil, where it enters the plants and fungi. Pollution is also exposed to insects, and animals that feed on them. Radioactive isotopes of plutonium and americium persist in soil for hundreds and possibly thousands of years, but their number is small. Nevertheless, some experts believe that the problems associated with pollution transuranic elements, require further study. The beta decay of Pu-241 in the contaminated areas is the formation of americium-241. Currently, the contribution of Am-241 in total alpha activity of 50%. Increased activity of soil contaminated with transuranic isotopes, due to Am-241 will continue until 2060 and his contribution will amount to 66,8%. In particular, in 2086 the alpha activity of soil in the contaminated territories of Belarus plutonium would be 2.4 times higher than in the initial period after the accident.
In the cities the bulk of hazardous substances to accumulate on the flat surface areas: on the lawns, roads, roofs. Under the influence of wind and rain, and as a result of human activities, the degree of contamination greatly decreased and now the radiation levels in most areas returned to background values. In agricultural areas in the first months of the radioactive substances were deposited on plant leaves and grass, so the contamination were herbivores. Then the radionuclides with the rain or fallen leaves caught in the soil, and now they come in fruit crops, mainly through the root system. Levels of pollution in agricultural areas has decreased significantly, but in some regions the number of cesium in milk still exceed the permissible values. This applies, for example, the Gomel and Mogilev regions of Belarus and the Bryansk region in Russia, Zhytomyr and Rivne Oblast in Ukraine.
Been heavily polluted forest. Due to the fact that the forest ecosystem cesium constantly recycled, and not derived from it, the levels of contamination of forest products such as mushrooms, berries and game, are dangerous. The level of pollution of rivers and most lakes are now low. However, in some "closed" lakes, of which there is no runoff, the concentration of cesium in water and fish still in the decades can be dangerous.
Contamination is not confined to the 30-kilometer zone. It was the high content of cesium-137 in lichen and reindeer meat in the arctic areas of Russia, Norway, Finland and Sweden.
In 1988 the area contaminated, was created by radiation-ecological reserve. Observations showed that the number of mutations in plants and animals although it grew, but only slightly, and the nature of successfully coping with their consequences. On the other hand, the removal of human impacts positively affected the ecosystem of the reserve and the influence of this factor far exceeded the negative effects of radiation. As a result, nature has recovered rapidly, increased animal population, increased diversity of plant species.