Polonium mean life

The chalcogen group of elements includes oxygen and sulfur, important elements for life, as well as selenium, tellurium, and polonium. The name stems the Greek word chalkos, meaning bronze or ore, and genes, which means bom. ... 

Rutherfordium (Z = 104) cannot be produced directly in " Ca-induced reactions, as it would require a polonium target. The isotopes Rf (Jin. — 160 s) and Rf Ty2 — 1.3 h) are the terminating SF activities of the decay chains derived from and Fl, produced in " Pu(" Ca,xn) reactions with x = 5 and X = 3, respectively [8, 316, 353]. Rf activities produced in hot-fusion reactions with lighter heavy ions with much higher cross sections are generally more appropriate for radiochemical experiments (see Liquid-Phase Chemistry of Superheavy Elements and Gas-Phase Chemistry of Superheavy Elements ). However, the long half-life of Rf may provide the means for previously unexplored radiochemical investigations. 

Polonium 210 has a half-life of only 210 days, meaning that the initiator had to be replaced regularly — there are references in Air Ministry files to short life initiators... (needing renewal every six months) , and the later Red Beard weapon had to be re-furbished at six-monthly intervals . ... 

The urchins functioned as designed, but they had shortcomings. Polonium-210 has a half-life of only 138 days, meaning that it had to be replaced and replenished frequently. To work properly, each urchin had to be inserted into the center of the fissile material within the nuclear bomb, an operation that was inconvenient at best. Eventually, an externally mounted neutron generator having a longer life was developed, allowing use of the urchins to be discontinued. 

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