Einsteinium

(Albert Einstein) Einsteinium, the seventh transuranic element of the actinide seriesto be discovered, was identified by Ghiorso and co-workers at Berkeley in December 1952 indebris from the first large thermonuclear explosion, which took place in the Pacific inNovember, 1952. The 20-day 253Es isotope was produced.

In 1961, enough einsteinium was produced to separate a macroscopic amount of 253Es.This sample weighted about 0.01Mg and was measured using a special magnetic-type balance.253Es so produced was used to produce mendelevium (Element 101).

About 3Mg of einsteinium has been produced at Oak Ridge National Laboratories by

1. irridiating kilogram quantities of 239Pu in a reactor for several years to produce 242Pu,
2. fabricating the 242Pu into pellets of plutonium oxide and aluminum powder,
3. loading the pellets into target rods for an initial 1-year irradiation at the Savannah River Plant, and
4. irradiating the targets for another 4 months in a HFIR (High Flux Isotopic Reactor).

The targets were then removed for chemical separation of the einsteinium fromcalifornium.