The Chernobyl disaster (Ukrainian: Чорнобильська катастрофа, Chornobylʹsʹka katastrofa, Chernobyl accident), was considered the worst nuclear disaster in history. It occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in the Ukrainian Soviet Socialist Republic, then part of the Soviet Union), now in Ukraine. The scientific consensus on the effects of the disaster has been developed by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). In peer-reviewed publications UNSCEAR has identified 49 immediate deaths from trauma, acute radiation poisoning, a helicopter crash and cases of thyroid cancer from an original group of about 6,000 cases of thyroid cancers in the affected area A United Nations study estimates the final total of premature deaths associated with the disaster will be around 4000, mostly from an estimated 3% increase in cancers which are already common causes of death in the region.
Some non-governmental organizations, many with staunch positions on the spectrum of the nuclear power debate, have claimed numbers up to a million excess deaths caused by the nuclear disaster. UN and other international agencies such as the Chernobyl Forum and the World Health Organization state that such numbers are wildly over-estimated. The Chernobyl Forum also acknowledges an increase in psychological problems amongst those exposed to radiation, which may be attributed in part to poor communication of radiation effects and disruption to their way of life, but is also likely affected by other events surrounding the breakup of the Soviet Union.