Uranium is a dangerous substance. Because Uranium is radioactive it is often seen with the hazard sign for radioactive elements, a group of three triangles with curved outer edges pointing in towards the middle (as you can see on the left). Some people believe that Uranium is light green, and glows, due to the way it is depicted in many movies. However, this is not true. Uranium is a shiny white metal, but is usually seen in its oxide form which is black. Spent or partially spent uranium fuel rods kept underwater, for example inside a nuclear reactor or in a spent fuel pool, can glow blue due to Cherenkov radiation. In addition to being radioactive, uranium is a heavy metal and is chemically toxic.