Chemist, with his prompt decisions, he mitigated the damage caused by the terrible Chernobyl nuclear accident, playing a fundamental role both in the team that managed the emergency and in the subsequent investigations into the causes of the explosion.
When the power plant broke down (26 April 1986), Legasov was the first deputy director of the Kurčatov Institute of Atomic Energy. He was appointed member of the commission to which the Soviet government gave the task of investigating the causes of the disaster and taking all necessary measures to reduce the damage. He was chosen because he was considered to be a scientist who was acquiescent in the Party's directives. Faced with the disaster, Legasov had to take charge of the situation, although with little time and even making mistakes, breaking the wall of silence and official lies.
He insisted on evacuating the population of Pripyat, saving many lives, and worked tirelessly, regardless of the radiation to which he was exposed, to try to contain the disastrous consequences of the accident: a mixture of boron containing lead, sand and clay was thrown by helicopters into the core of the reactor to absorb the radiation.
Even when he faced with a lost and confused Michail Sergeevič Gorbačëv (who many years later did not hesitate to confess that "the Chernobyl tragedy was the sign of the end of the Soviet Union"), and his fellow scientists, he did not hesitate to speak clearly and show the risks that the plant, although destroyed, still represented. For many weeks, he stayed at the Chernobyl site, exposing himself to the most dangerous radiation.
Legasov then reported to the International Atomic Energy Agency in Vienna on the human and Soviet Union's responsibilities in the disaster. His intervention calmed down the international community, but irritated his Soviet colleagues. Mikhail Gorbachev twice removed his name from the list of those who would receive the Hero of Socialist Labour decoration for the Chernobyl emergency response, saying that "other scientists do not recommend rewarding him".
After the report he was marginalized and reduced to silence: the spreading of his truthful files was prohibited. On the day of the second anniversary of the disaster, Legasov hung himself, while his body was deteriorating due to the consequences of absorbed radiation. Before he killed himself, he recorded an audio tape in which he revealed all the facts about the catastrophe that he had been prevented from disclosing. Legasov's suicide had repercussions all over the nuclear world in the Soviet Union. In particular, the government had to reconsider what had been said and admitted the structural problems that the Chernobyl plant was already suffering before the disaster. On 20 September 1996, on the occasion of the first tenth anniversary of the tragedy, Russian President Boris El'cin awarded him the late title of Hero of the Russian Federation for the courage and heroism shown in the investigation of the disaster.
Legasov, with his courage and his obstinate search for the uncomfortable truth, together with a few other scientists, saved Central Europe from a disaster that could take on even greater and lasting dimensions (by now we officially speak of 93.000 dead).