the need to enrich the uranium in the fuel. Hazards Plutonium-239 emits alpha particles to become uranium-235. As an alpha emitter, plutonium-239 is not particularly dangerous as an external radiation source, but if it is ingested or breathed in as dust it is very dangerous and carcinogenic. It has been estimated that a pound (454 grams) of plutonium inhaled as plutonium oxide dust could give cancer to two million people. However, ingested plutonium is by far less dangerous as only a tiny fraction is absorbed in gastrointestinal tract. 800 mg would be unlikely to cause a major health risk as far as radiation is concerned. As a heavy metal, plutonium is also chemically toxic. See also Plutonium#Precautions. Weapons grade plutonium (with greater than 90% 239Pu) is used to make nuclear weapons and has many advantages over other fissile material for that purpose. Lower proportions of 239Pu would make a reliable weapon design difficult or impossible; this is due to the spontaneous fission (and thus neutron production) of the undesirable 240Pu. See also Teller-Ulam design References External links NLM Hazardous Substances Databank – Plutonium, Radioactive Table of nuclides with 239Pu data at Kaye and Laby Online Half-life of Plutonium-239 Actinides Fissile materials Isotopes of plutonium Special nuclear materials Radioactive contamination