253Es

Albert Einstein) Einsteinium, the seventh transuranic element of the actinide series to be discovered, was identified by Ghiorso and co-workers at Berkeley in December 1952 in debris from the first large thermonuclear explosion, which took place in the Pacific in November, 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 O.OlMg and was measured using a special magnetic-type balance. 253Es so produced was used to produce mendelevium (Element 101). 

Tracer studies using 253Es show that einsteinium has chemical properties typical of a heavy trivalent, actinide element. 

Dmitri Mendeleev) Mendelevium, the ninth transuranium element of the actinide series discovered, was first identified by Ghiorso, Harvey, Choppin, Thompson, and Seaborg in early in 1955 during the bombardment of the isotope 253Es with helium ions in the Berkeley 60-inch cyclotron. The isotope produced was 256Md, which has a half-life of 76 min. This first identification was notable in that 256Md was synthesized on a one-atom-at-a-time basis. 

Die Einsteiniumfraktion lieferte 0,289 pg Es. Weiteres 253Es konnte beim Abmelken der Californiumfraktion erhalten werden. 

Fig. 2. Alpha spectra of the mixture 241Am, 244Cm, 2S2Cf, 253Es and 2S2Fm prepared by electrodeposition (233U was used as a monitor of the yield of the electrodeposition)...

In the second experiment, performed in pure 0.01 M HF without any HN03, 90 events attributable to 253Es were observed in the strip fraction representing the solid phase and zero events in the liquid phase. This leads to... 

The process sequence now used is shown in Fig. 4. Since only about 5% of the fission products are disposed of in waste solutions from the Tramex batch extraction, that process serves primarily as a feed pretreatment for the LiCl AIX. The Tramex product contains about 98% of the transcurium elements and can be processed quickly to maximize the recovery of 253Es which has a 20-d half-life. As time permits, the "clean rework" can be processed to recover the remaining actinides. 

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