Radioactive materials have been used by people ... exposed experienced a dose of radiation that was between 4.5 and 6 Gray (Gy). Exposure of just .7 Gy puts one at risk of acute radiation syndrome ...

(Bloomberg) -- A few miles south of the Grand Canyon, thousands of tons of uranium ore, reddish-gray, blue and radioactive, are piled up high in a clearing in the forest. They’ve been there for ...