Alpha decay helium produced on Earth is the result of the alpha decay of underground deposits of minerals containing uranium or thorium. The helium is brought to the surface as a by-product of natural gas production. Alpha particles were first described in the investigations of radioactivity by Ernest Rutherford in 1899, and by 1907 they were identified as He ions. By 1928, George Gamow had solved the theory of alpha decay via tunneling. The alpha particle is trapped in a potential well by the nucleus. Classically, it is forbidden to escape, but according to the (then) newly discovered principles of quantum mechanics,
British nuclear tests at Maralinga nuclear warheads containing plutonium-239. In total, "Vixen B" scattered 22.2 kg of plutonium around the Maralinga test site known as Taranaki, in particles of widely divergent size. Plutonium is not particularly dangerous externally - it emits alpha particles which are stopped by of air, or the dead layer of skin cells on the body, and is not a very intensive source of radiation, due to its long half-life of 24,000 years. It is most dangerous when it enters the body, in the worst case by breathing, and therefore tiny particles, often the result of such explosion testing, are the worst