This translates into one major accident, being defined according to the International Nuclear Event Scale (INES), every 3,625 years.

The total number of operating hours is 14,500 years, the number of reactor meltdowns comes to four-one in Chernobyl and three in Fukushima. They divided the operating hours of all civilian nuclear reactors in the world, from the commissioning of the first up to the present, by the number of reactor meltdowns that have actually occurred. To determine the likelihood of a nuclear meltdown, the researchers applied a simple calculation. Currently, there are 440 nuclear reactors in operation, and 60 more are planned.

It appears that the global risk of such a catastrophe is higher than previously thought, a result of a study carried out by a research team led by Jos Lelieveld, Director of the Max Planck Institute for Chemistry in Mainz: 'After Fukushima, the prospect of such an incident occurring again came into question, and whether we can actually calculate the radioactive fallout using our atmospheric models.' According to the results of the study, a nuclear meltdown in one of the reactors in operation worldwide is likely to occur once in 10 to 20 years. The reactor accident in Fukushima has fuelled the discussion about nuclear energy and triggered Germany's exit from their nuclear power program. In view of their findings, the researchers call for an in-depth analysis and reassessment of the risks associated with nuclear power plants. According to the International Atomic Energy Agency, an area is defined as being contaminated with radiation from this amount onwards. Their results show that Western Europe is likely to be contaminated about once in 50 years by more than 40 kilobecquerel of caesium-137 per square meter. The researchers also determined that, in the event of such a major accident, half of the radioactive caesium-137 would be spread over an area of more than 1,000 kilometres away from the nuclear reactor. Based on the operating hours of all civil nuclear reactors and the number of nuclear meltdowns that have occurred, scientists at the Max Planck Institute for Chemistry in Mainz have calculated that such events may occur once every 10 to 20 years (based on the current number of reactors) - some 200 times more often than estimated in the past. Catastrophic nuclear accidents such as the core meltdowns in Chernobyl and Fukushima are more likely to happen than previously assumed.

Nuclear reactor meltdown up close