Pa 91 Protactinium
Protactinium metal primarily is generated from the decay of the rare isotope uranium 235 (via the very unstable thorium 231). Therefore Protactinium metal only exists in small amounts, most of it is found in nuclear waste. The half-life of the most stable isotope 231Pa is 32760 years. Outside of science, no applications for protactinium metal exist.
Representative sample of Protactinium metal (Pa231), few micrograms deposited upon Al metal strip sealed in ampoule and permanently casted in resina.
