Chernobyl: Measurements of environmental radioactivity after forest fire

Estimation of soil contamination by Caesium 137, caused by the most recent forest fires in the exclusion zone around the Chernobyl nuclear power plant

At the end of last week, the Ukrainian fire brigade battled a forest fire in the exclusion zone around Chernobyl. According to information from the Ukrainian authorities, the fire has since been extinguished. An area of around 25 hectares was affected. To date, the BfS has not ascertained any increase in radioactivity in the air in Germany. There is no risk to human health or to the environment.

Using the information given, the BfS calculated how much radioactive Caesium 137 could have been released by the forest fire. With these data, a calculation was commissioned by the German Meteorological Service (DWD) to show how Caesium 137 spreads through the atmosphere for the stated duration of the fire. BfS experts analysed this calculation with the help of the decision-making modelling assistant RODOS ("Realtime Online Decision Support System"), which enabled the future environmental contamination and the expected doses to be estimated. It was found that:

• Because of the weather situation, no radioactivity can currently reach Germany.
• Even in unfavourable weather conditions and on reignition of the fire, the effects in Germany would be extremely mild (around 10 million times smaller than after the reactor accident in 1986). In that case too, there was no risk to human health or to the environment.

Forest fires around Chernobyl occurring more frequently

Due to the dryness of the season, there have been repeated forest fires and wildfires in the region around Chernobyl. These can lead to radioactive particles being stirred up into the atmosphere along with the ash. Recently in April 2015, a largescale forest fire with a dimension of around 400 hectares was reported in the region around Chernobyl. However, the sensitive measurement instruments of the BfS could not ascertain any increase in radioactivity in the air in Germany during this fire.

The Schauinsland monitoring station of the BfS with the new annexe for the RASA air sampler

The Federal Office for Radiation Protection operates one of the leading stations worldwide for the measurement of radioactivity on the Schauinsland Mountain near Freiburg. The measurement station - one of 80 radionuclide measurement stations for monitoring nuclear weapons tests and the like in central Europe – is in a position to identify even the tiniest quantities of radioactive materials in the air. Increased Caesium 137 concentrations, which were attributable to a wildfire in the exclusion zone around Chernobyl, were registered at Schauinsland for example in the summer of 1992. The measurements in the coming weeks will be tested in a targeted way for traces from the most recent forest fire.