Changes

* '''[[January 28]]''' – [[NASA]]'s space shuttle "Challenger" explodes on launch during a live broadcast, killing all seven astronauts aboard. Their bodies are located on March 9.

* '''[[April 26]]''' – '''Chernobyl disaster:''' A high-power channel-type reactor at Chernobyl Nuclear Power Plant in the Ukrainian Soviet Socialist Republic reaches prompt criticality.<br> The initial emergency response, together with later decontamination of the environment, involved more than 500,000 personnel and cost an estimated 18 billion Rubles. <br> The accident occurred during a safety test: During a planned decrease of reactor power in preparation for the test, the operators accidentally dropped power output to near-zero. <br> While recovering from the power drop and stabilizing the reactor, the operators removed a number of control rods which exceeded limits set by the operating procedures. <br> Upon test completion, the operators triggered a reactor shutdown. Due to a design flaw, this action resulted in localized increases in reactivity within the reactor. <br> This resulted in rupture of fuel channels, leading to a rapid decrease in pressure which caused the coolant to flash to steam, leading to the creation of a positive feedback loop. <br> This process resulted in steam explosions and melting of the reactor core. The meltdown and explosions ruptured the reactor core and destroyed the reactor building. <br> This was immediately followed by an open-air reactor core fire. In response to the initial accident, a 10-kilometre (6.2 mi) radius exclusion zone was created 36 hours after the accident, <br> from which approximately ~49,000 people were evacuated. The exclusion zone was later increased to 30 kilometres (19 mi) and an additional ~68,000 people were evacuated.