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Frequently asked questions

Nuclear Safety > Nukleare Unfälle > Tschernobyl > Frequently asked questions

Frequently asked questions
  1. What happened in the chernobyl reactor?
  2. Is this likely to happen in German nuclear power plants too?
  3. Reactions of people responsible in Germany came late at the time and were contradictory. What has been done since to infomr and warn the population in due time, correctly and unambiguously?
  4. What radioactive substances were released through the Chernobyl reactor accident? What half-lives do they have?
  5. What radioactive substances can still be measured today?
  6. There are contradictory statements on deaths and diseases in the aftermath of Chernobyl. How does the BfS evaluate the situation in the vicinity of Chernobyl??
  7. Have diseases or deaths occurred in Germany or other central European countries that were caused by Chernobyl?
  8. Can certain diseases at all be traced back directly to the fallout? If not, why not?
  9. Do children from Chernobyl pass the radiation disease on?
  10. Where did the radioactive fallout come down?
  11. How strongly is Germany still contaminated?
  12. Is food still contaminated?
  13. Why are forest fruits and mushrooms higher contaminated than field crops?
  14. Are water (groundwater) and air still contaminated?

  1. What happened in the Chernobyl reactor?

    The accident occurred in unit 4 of the Chernobyl nuclear power plant – a reactor type of Soviet design. The reactor was in the phase of a slow shutdown according to schedule to carry out routine maintenance and test measures (revision). At the same time an experiment was planned for checking various safety features of the plant. Basic design failures of the plant in combination with failures and offences in operational management led to the reactor disaster. You will find more detailed information in the article “The Chernobyl Accident".


  2. Is this likely to happen in German nuclear power plants too?

    Regarding the applicability of the accident to a German plant, the Reactor Safety Commission stated in November 1986 “that a promptly critical power excursion as it occurred in Chernobyl can be ruled out due to the inherent physical features and the technical equipment in a light-water reactor of German design and that the safety concept of nuclear power plants in the Federal Republic of Germany is not called into question by the Chernobyl accident”.

    The Chernobyl accident was based on the reactor-physical properties of a water-cooled and graphite-moderated reactor. Such a sequence of events cannot occur in the light-water reactors used in Germany. However, assuming a failure of all safety devices, other accident sequences could be imagined that could lead to a core melt-down. You will find information on the sequence of events of a core melt-down at “Frequently asked questions on nuclear aspects of the events in Japan” (only available in German).

  3. Reactions of people responsible in Germany came late at the time and were contradictory. What has been done since to inform and warn the population in due time, correctly and unambiguously?

    In both the German Democratic Republic and the Federal Republic of Germany it was recognised that the provision of data to evaluate the situation needed to be systematised. The measurement network for the monitoring of environmental radioactivity has been massively extended in the following years and the decision-finding process has been structured essentially. Today the “Integrated Measurement and Information System for the Monitoring of Environmental Radioactivity” (IMIS) combines all measured values and information from the federation and the federal states and forms the basis of a targeted and transparent information policy with clear recommendations in case of an incident.

  4. What radioactive substances were released through the Chernobyl reactor accident? What half-lives do they have?

    Numerous radioactive substances with different half-lives were released into the atmosphere. You will find more details on this topic in the article “The Chernobyl Accident”.

  5. What radioactive substances can still be measured today?

    Of the radioactive substances released with the Chernobyl accident it is only the caesium isotope 137 that can be measured practically in Germany. As it is a volatile substance caesium was released in large amounts and was transported over large areas. Due to its half-life of about 30 years only up to 40 per cent of this radioisotope has decayed so far. Read more in the article “Environmental consequences” (only available in German).

  6. There are contradictory statements on deaths and diseases in the aftermath of Chernobyl. How does the BfS evaluate the situation in the vicinity of Chernobyl?

    Health effects have been observed in employees and amongst clean-up workers (so-called liquidators). Furthermore the number of thyroid cancer had clearly increased in persons who had been exposed to iodine-131 as children and adolescents under the age of 18 in the most affected regions. So far there is no reliable data about further cancers in these regions. The same applies to the affected regions outside the former Soviet Union. same applies to the affected regions outside the former Soviet Union.

  7. Have diseases or deaths occurred in Germany or other central European countries that were caused by Chernobyl?

    So far there has been no proof of adverse health effects following radiation exposure caused by the Chernobyl accident in Germany or other central or north European countries.

    You will find more information at “Health effects in Germany and Europe outside the former Soviet Union” (only available in German).

  8. Can certain diseases at all be traced back directly to the fallout? If not, why not?

    Cancers, cardiovascular diseases or cataracts caused by radiation can only be determined with epidemiological-statistical methods in relatively large groups of persons on the basis of increased incidence or mortality. They cannot be detected in individual persons on the basis of the disease pattern. With regard to the disease pattern radiation-caused diseases do not differ from so-called spontaneous diseases.

  9. Do children from Chernobyl pass the radiation disease on?

    From the radiation protection point of view there are no concerns about hosting children from the Chernobyl area, not even for longer periods of stay. No hazardous radiation emanates from the children coming from higher contaminated regions in the vicinity of Chernobyl who come to Germany. Objects brought with them do not pose a risk either.

  10. Where did the radioactive fallout come down?

    As a result of the Chernobyl accident large amounts of radioactive substances were released into the atmosphere. They dispersed locally in Belarus, Ukraine and Russia and furthermore over the northern hemisphere, in particular over Europe. Due to the strongly changing meteorological conditions several radioactive clouds formed in different directions. The initially existing air current transported the radioactive substances via Poland to Scandinavia. A second cloud went to Germany via Slovakia, Czech Republic and Austria.

    A third cloud finally reached the countries of Rumania, Bulgaria, Greece and Turkey.  The resulting radioactive contamination in the affected areas varied considerably depending on the occurrence and amount of rainfall during the passing of the radioactive air masses.

    The south of Germany was clearly higher exposed than the north due to strong local rainfalls. Locally in the Bavarian Forest and south of the river Danube up to 100,000 becquerels caesium-137 per square metre were measured. In the North German Plain, however, the activity deposition of this radionuclide rarely amounted to more than 4,000 becquerels per square metre.

    You will find more inforamtion at "Environmental consequences" (only available in German)

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  11. How strongly is Germany still contaminated?

    After the Chernobyl reactor accident a multitude of radionuclides were deposited in Germany. Many of the mostly short-lived radionuclides have practically decayed entirely today. In terms of radiation exposure caused by the reactor accident only the long-lived caesium-137 does play a role today, only 40 per cent of which have decayed so far due to its half-life of about 30 years. Part of the caesium is bound to soil components so that it has been taken out of the biological circle. In the highest contaminated regions of south Bavaria the Cs-137 in the soil still contributes only about 5 per cent to the natural dose rate measured. In addition to Chernobyl also the radionuclides originating from the above-ground nuclear weapons tests contribute to the contamination in Germany.

    You will find more inforamtion at "Environmental consequences" (only available in German).

  12. Is food still contaminated?

    As early as in the summer of 1986 were agricultural cultures sown or planted after the Chernobyl reactor accident contaminated only with a few becquerels radio-caesium per kg. Today the content of Cs-137 in agricultural produce from domestic production is also in this order of magnitude and below. In Germany on average about 100 Bq Cs-137 per person and year are taken up through food from farm production.

    The situation in terms of food from forests is entirely different. In particular with edible mushrooms and game clearly enhanced Cs-137 activities can still be measured more than 20 years after the Chernobyl reactor accident. The caesium content of forest produce generally decreases only slowly. Higher contaminated food from forests can be expected in those parts of Germany that had been strongly affected by the Chernobyl fallout. These are especially the Bavarian Forest and the areas south of the river Danube. In other regions such as North Germany the activity levels are lower as less radio-caesium was deposited. A very high local fluctuation margin of the Cs-137 content is characteristic of wild mushrooms and game.

    People who want to keep radiation exposure as low as possible should therefore do without consuming comparatively high contaminated mushrooms and game, e.g. from the Bavarian Forest, in particular wild boar.

    You will find more inforamtion at "Environmental consequences" (only available in German).

  13. Why are forest fruits and mushrooms higher contaminated than field crops?

    Radio-caesium can be strongly bound to certain clay minerals on the mineral soils of arable land. Thus there is not much left for being taken up over the roots.

    Forests are characterised by organic layers covering the mineral soils. These layers formed through decomposing mulch. Caesium is easily available there. Soil organisms, mushrooms and plants take it up easily. Caesium remains bound to the nutrient cycling that is typical of nutrient-poor eco-systems and very effective and which therefore hardly migrates into the mineral soil layers. Similar as on agricultural soils, it can be fixed there by certain clay minerals. The caesium-137 activity of edible mushrooms and game can therefore be clearly enhanced and will only reduce slowly.

  14. Are water (groundwater) and air still contaminated?

    Neither in air nor in water can remarkable radioactivity be measured today that can be traced back to the Chernobyl accident.

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