The longest-lived isotope of curium , 247Cm , has a half-life of 15.6 million years . Therefore , any primordial curium , that is curium present on the Earth during its formation , should have decayed by now , although some of it would be detectable as an extinct radionuclide as an excess of its primordial , long-lived daughter 235U . Curium is produced artificially , in small quantities for research purposes . Furthermore , it occurs in spent nuclear fuel . Curium is present in nature in certain areas used for the atmospheric nuclear weapons tests , which were conducted between 1945 and 1980 . So the analysis of the debris at the testing site of the first U.S. hydrogen bomb , Ivy Mike , ( 1 November 1952 , Enewetak Atoll ) , beside einsteinium , fermium , plutonium and americium also revealed isotopes of berkelium , californium and curium , in particular 245Cm , 246Cm and smaller quantities of 247Cm , 248Cm and 249Cm
Ivy Mike
Ivy Mike
Curium