It's been 25 years since the World's worst nuclear disaster, and at Chernobyl, calls for lessons to be learned.

FOX  News Radio's Alastair Wanklyn reports from London:

Hundreds of Ukrainians gathered Tuesday morning for a Memorial Ceremony honoring those killed in the nuclear disaster in the city of Slavutich, built to relocate the people who worked and lived near the power plant.

Listen here to bells played at the service - which took place at 1:23am local time - which was the exact moment 25 years ago that the plant's number four reactor exploded:

Listen here as U.N. Secretary General Ban Ki-moon reflected on the tragedy: