KHUTORY, Ukraine - Petro Hurin says his health has never been the same since he was sent 40 years ago to clear the Chernobyl site in the wake of the world's worst nuclear accident.He was among hundreds of thousands of 'liquidators' brought in to clean up after the explosion at reactor four of the Chernobyl nuclear plant in Ukraine on April 26, 1986. The disaster sent clouds of radioactive material across ​much of Europe.Thirty-one plant workers and firemen died in the immediate aftermath, mostly from acute radiation sickness. Thousands more have since succumbed to ‌radiation-related illnesses ‌such as cancer, although the total death toll and long-term health effects remain a subject of intense debate.