Zbigniew Jaworowski was chairman of the Scientific Council of the Central Laboratory for Radiological Protection in Warsaw and Chair of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). He says that Chernobyl was probably the worst possible catastrophe of a nuclear power station. The photo shows the eruption of Mt. St. Helens volcano in Washington State in 1980. It was much larger than the energy release from Chernobyl, but up to 100 times smaller than the largest volcanic eruption on Earth.