Mr. Amano, a Japanese national and head of the IAEA since 2009, had been due to step down next March amid reports of an unspecified illness.
UN chief António Guterres paid tribute, saying he was deeply saddened to hear the news of his death.
Through his stewardship of the IAEA, "Director-General Amano worked tirelessly to ensure that nuclear energy is used only for peaceful purposes. In leading IAEA in such an exemplary fashion, he advanced human well-being through efforts spanning medicine, agriculture and other vital areas" said the Secretary-General.
"Mr. Amano confronted serious global challenges, including those related to the proliferation of nuclear weapons, with equanimity and determination. Our world is so much better for it", he continued. "I send my deepest condolences to his family and the staff of the IAEA. In mourning his tragic loss, we are also thankful for Mr. Amano’s distinguished service to his country and all humanity."
In a letter to the agency’s Board of Governors announcing his decision to resign, Mr. Amano wrote that over the past decade, IAEA had delivered “concrete results” to prevent the spread of nuclear weapons, in line with its mandate.
“I am very proud of our achievements and grateful to Member States and Agency staff,” Mr. Amano said.
Among the many tributes to Mr. Amano, UN General Assembly President, María Fernanda Espinosa, said in an online post that his achievements would stand the test of time.
I am deeply saddened to learn of the passing of @iaeaorg Director General Yukiya Amano. His remarkable contributions to the peaceful use of nuclear technology and his commitment to multilateralism will be remembered by all of us who had the privilege of knowing him.— António Guterres (@antonioguterres) July 22, 2019
“Deeply saddened by the news of the passing of Mr. Yukiya Amano, Director General of the International Atomic Energy Agency,” she tweeted. “Mr. Amano worked tirelessly to promote a safer, denuclearised world. His legacy will not be forgotten. My condolences to his family and all IAEA staff.”
Echoing that message, José Graziano da Silva, head of the UN Food and Agriculture Agency (FAO), underlined how the two agencies had worked together to tackle global food insecurity.
“I am deeply saddened by the loss of Yukiya Amano…Over the past 50 years, the @FAO/IAEA Joint Division has worked in the peaceful application of nuclear science & technology for more, better&safer food while sustaining natural resources,” Mr. da Silva tweeted.
When asked to explain the work of the IAEA and its mandate, “Atoms for Peace”, Mr. Amano said that in addition to preventing the spread of nuclear weapons by overseeing nuclear verification regimes involving Iran, for instance, the agency also helps countries use atomic science and technology for the overall good of humanity. For example, to produce more food, generate more electricity, treat cancer and respond to climate change.
The IAEA played “a much bigger role in our daily lives than most people realize”, Mr. Amano insisted, pointing out that radiation was routinely used to treat microchips and batteries in smartphones, car tyres and electrical cables used in the home.
On other practical levels, Mr. Amano noted that the IAEA’s expertise was used to track the spread of pollutants and biotoxins in the seas and oceans that pose a threat to fish and shellfish - key sources of food for millions of people.
With the help of the IAEA, countries “can take the necessary measures to protect fish stocks and consumers”, he told the Dublin Institute for Advanced Studies in May 2018. All of these are routinely treated with radiation, Mr. Amano said.
Nuclear techniques are also used in plant breeding, soil and water management, and crop nutrition, the IAEA Director General continued, helping to improve food security.
In particular, the IAEA helps countries to develop and grow new varieties – and higher yields - of crops such as rice and barley, which are also more resistant to drought and disease.
Farmers in Indonesia, Malaysia, the Philippines and Viet Nam had boosted rice production in recent years, Mr. Amano said, despite harsh conditions.
“By applying radiation in the laboratory, scientists accelerate the spontaneous mutation process that occurs in nature all the time,” Mr. Amano explained. “They can develop new varieties of crops with desirable characteristics very quickly. This does not involve genetic modification of the plants.”