Today we mark the thirtieth anniversary of the accident at the Chernobyl nuclear power plant on 26 April 1986 – one of the most serious nuclear accidents in history.
The disaster had grave humanitarian, environmental, social and economic consequences. It cast a radioactive plume across a swathe of northeastern Europe, and its effects are still being felt in the region and around the world. 
I will never forget visiting the site of the accident five years ago. The reactor encased in concrete, the empty houses and villages and the sense of lives ruptured by sudden tragedy made a deep impression on me.
This anniversary offers an opportunity to take stock of lessons learned, reflect on the recovery process, and to appreciate once again the heroic efforts of the first responders who rushed to the damaged reactor on 26 April 1986 and sacrificed their health, and in many cases their lives, to save others.
The tragedy of Chernobyl will always be linked with nuclear safety. The accident led to a new awareness of safety issues and to major improvements in the regulation of nuclear plants around the world. 
The Chernobyl disaster also brought the international community together to support the enormous efforts of local, regional and national authorities.  I particularly commend the Governments of Belarus, the Russian Federation, and Ukraine for their joint work.
The most visible sign of current international cooperation efforts may be the New Safe Confinement structure, which is now nearing completion, and should make the reactor complex stable and environmentally safe for the next 100 years.  We owe our gratitude to the Governments and international institutions that contributed to the costs of this record-breaking structure. 
Since 1986, the United Nations has helped to address the needs of people in the areas surrounding Chernobyl, first through emergency and humanitarian aid, and then by supporting recovery and social and economic development, which still continues.
The United Nations has also helped to provide essential information on the continuing impact of radiation on local communities.
I commend the success of the development approach adopted ten years ago and led by UNDP. Communities that were affected by the accident are now more self-reliant and self-sufficient, and lessons have been learned for the future.
Knowledge gained from the tragedy at Chernobyl is helping other people and communities around the world to protect themselves and to recover from trauma, including during the Fukushima Daiichi nuclear emergency of 2011.  
There is a growing risk of disasters in which natural events combine with chemical, biological, radiological and nuclear crises. At the World Humanitarian Summit that I am convening in Istanbul on 23rd and 24th May, I will ask leaders to consider multidisciplinary strategies that include prevention, preparedness and response.
Looking ahead, long-term recovery efforts around Chernobyl must be linked to the 2030 Sustainable Development Goals.
The 2030 Agenda’s promise to leave no one behind applies above all to those caught up in crises around the world; those who have struggled for years to overcome trauma and fears about their health and livelihoods; and those who continue to demonstrate their resilience as they walk the road to recovery and development.
Their loss and pain will never be forgotten.