River in Chernobyl Exclusion Zone. Winter landscape and frozen river in the Chernobyl Exclusion Zone around the Chernobyl nuclear power station in Ukraine. The Chernobyl disaster of 23 April 1986 occurred when one of the nuclear reactors at the power station went into meltdown, causing an explosion. Radioactive fallout affected a large area, and an exclusion zone with a radius of 30 kilometres (later extended) was established. Over 90, 000 people were evacuated from the exclusion zone. A large sarcophagus structure was built to contain the reactor and the radioactive materials. Within the exclusion zone the radiation is still dangerous. Depending on the distance and level of fallout, protective clothing and monitoring of exposure times is required. Photographed in 2011.