Einsteinium and fermium were identified in 1952 – 1953 in the fallout from the " Ivy Mike " nuclear test ( 1 November 1952 ) , the first successful test of a hydrogen bomb . Instantaneous exposure of uranium-238 to a large neutron flux resulting from the explosion produced heavy isotopes of uranium , including uranium-253 and uranium-255 , and their β-decay yielded einsteinium-253 and fermium-255 . The discovery of the new elements and the new data on neutron capture were initially kept secret on the orders of the U.S. military until 1955 due to Cold War tensions . Nevertheless , the Berkeley team were able to prepare einsteinium and fermium by civilian means , through the neutron bombardment of plutonium-239 , and published this work in 1954 with the disclaimer that it was not the first studies that had been carried out on the elements . The " Ivy Mike " studies were declassified and published in 1955 . The first significant ( submicrograms ) amounts of einsteinium were produced in 1961 by Cunningham and colleagues , but this has not been done for fermium yet
Ivy Mike
Ivy Mike
Actinide