Isotope Seized in Georgia Too Small for Dirty Bomb Three men are under arrest in Georgia on charges of illegally possessing a radioactive isotope that can be used in a dirty bomb, but authorities say they didn't have enough to make one of the devices. Grigol Basilia, Georgian energy ministry's top official for security issues, measures radiation level at an apartment building in downtown Tbilisi, Georgia, on Thursday, April 4, 2013. Three men are under arrest in Georgia on charges of illegally possessing a radioactive isotope that couls be used in a dirty bomb, but authorities say they didn't have enough to make one of the devices. Grigol Basilia on Thursday declined to say how much of the isotope was seized, but "I can say it was not enough to build a so-called dirty bomb." (AP Photo/Shakh Aivazov) Close Police say the three Georgians were holding Americium-241. That is one of the substances widely seen as a possible component in explosive devices aimed at spreading radioactive particles that would kill or sicken people. Grigol Basilia, the energy ministry's top official for security issues, on Thursday declined to say how much of the isotope was seized, but said it was "not enough to build a so-called dirty bomb."