The upcoming 25th anniversary of the Chernobyl disaster is a brutal reminder of the dangers of nuclear power, proliferation and terrorism, former Soviet president Mikhail Gorbachev said on Tuesday. "The true scope of the tragedy still remains beyond comprehension and is a shocking reminder of the reality of the nuclear threat," Gorbachev said in an essay published by the Bulletin of the Atomic Scientists, a watchdog organisation on nuclear security. Nuclear Power Daily