"Polonium-210 has a half-life of 138 days, necessitating the replacement of the triggers every six months. For this reason, the suitcase nukes are far from maintenance-free. In addition, the nuclear core of these devices emit a temperature in excess of one hundred degrees Fahrenheit - - further exposing the weapons to oxidation and rust. Small wonder that al Qaeda operatives including Adnan el-Shukrijumah, who are spearheading "the American Hiroshima" have received extensive training in nuclear technology.
Polonium-beryllium triggers are packaged in foil packs about the size of a package of sugar on a restaurant table. When the twin foil packages are crushed, the elements mix and the neutrons are emitted. A courier transporting nuclear triggers could have had a mishap causing the packages to rupture and a trail of contamination to occur.
Polonium-210 is a fine powder, easily aerosolized. Litvinenko could have inhaled the powder, or had a grain or two on his fingers when he ate the sushi."