An explosion and fire at the Chernobyl Nuclear Power Plant in Reactor 4 causes the worst nuclear disaster in history, releasing massive amounts of radioactive material into the environment.
The Soviet government publicly acknowledges the accident at Chernobyl Nuclear Power Plant and begins emergency response measures.
Efforts begin to build the concrete sarcophagus designed to contain the radioactive materials from the damaged reactor.
A 30-kilometer exclusion zone around the Chernobyl plant is established to restrict access and minimize radiation exposure.