In the last decades. most serious nuclear reactor accident created MIC gas tragedy in 

Bhopal gas tragedy occurred on $3^{rd}$ Dec. 1984 due to leakage of methyl isocyanate creating air pollution and causing death of about 2500 persons. Chernobyl disastrous tragedy occurred on April 26. 1986 due to explosion at chernobyl nuclear power station resulting huge amount of radioactive clouds in the Ucraine atmosphere.