People around the world hold demonstrations and remember victims on the 30th anniversary of Chernobyl nuclear disaster on Monday (April 25). The explosion of Unit 4 of the Chernobyl nuclear power plant in the early hours of April 26, 1986, is still regarded as the biggest accident in the history of nuclear power generation. An estimated 47,000 people of the city of Pripyat in northern Ukraine were evacuated after the explosion in 1986.