On April 26, 1986, the worst nuclear power plant accident took place at the Chernobyl Power Plant in Pripyat, Ukraine.  A steam explosion occurred in Reactor 4 causing a melt down.  The radiation was not contained and radioactive particles filled the air effecting many other countries.  
   
    At the time of the melt down, it was unaware of the real problem the radiation was going to cause.  A radioactive cloud had formed and made its way over many of the European and Asian countries.  Different areas were effected differently depending on the weather during the melt down.