25 years ago today, reactor number 4 at the Chernobyl Nuclear Power Plant in the Ukrainian Republic of the Soviet Union experienced a catastrophic explosion. The resulting catastrophe proved to be the worst nuclear disaster in history. It spread radioactive contamination across much of Europe and western Russia and resulted in the resettlement of thousands of people away from the contaminated areas. Additionally, the safety of nuclear power was called into question as a result of the accident and development of new nuclear power plants slowed considerably as a result.
To find out more about the Chernobyl disaster, have a look at some of the following sources:
Credo Reference has an excellent topic page on Chernobyl. (CPCC Login may be required.)
Need to Know on PBS.org has a brief feature on the accident.
NPR has a story on life in the Chernobyl area today.