Isotopes of tantalum

Natural tantalum (₇₃Ta) consists of two stable isotopes: ¹⁸¹Ta (99.988%) and ^180mTa (0.012%).

There are also 35 known artificial radioisotopes, the longest-lived of which are ¹⁷⁹Ta with a half-life of 1.82 years, ¹⁸²Ta with a half-life of 114.74 days, ¹⁸³Ta with a half-life of 5.1 days, and ¹⁷⁷Ta with a half-life of 56.46 hours. All other isotopes have half-lives under a day, most under an hour. There are also numerous isomers, the most stable of which (other than ^180mTa) is ^182m2Ta with a half-life of 15.8 minutes. All isotopes and nuclear isomers of tantalum are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.

Tantalum has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material). A jacket of tantalum, irradiated by the intense high-energy neutron flux of the weapon, would be transmuted into the radioactive isotope ¹⁸²
Ta, producing about 1.12 MeV of gamma radiation per decay and significantly increasing the radioactivity of the weapon's fallout for months. Such a weapon is not known to have ever been built, tested, or used.^[4]