U.S. and Russian scientists are cooperating to conduct tests of simulated "dirty bombs" In isolated areas of the Russian Ural mountains and the American West, test bombs are being set off. These bombs use non-radioactive substances that have the same shape and weight of radioactive materials that could be used in such bombs. The scientists are interested in how far the radioactive material would spread and what impact the wind and other climate factors would have. There is a lot (tons) of highly radioactive material in circulation, much of it in power form, and largely used for medical and industrial purposes. Particularly worrisome are the hundreds of Radiothermal Generators (RTGs) Russia set up in remote parts of the country during the Soviet era. The RTGs were similar to the power supplies found on some space satellites, using radioactive material to generate heat, and thus electricity, for radio beacons and signal repeaters in remote areas. The Russians aren't even sure where some of these RTGs are, and there have been cases of civilians finding them, cracking them open and being injured, or killed, from the radiation. The Russians noted that there have been many attempts to steal radioactive material in Russia, but none, so far as is known, have succeeded.