ctive substances.

Neutrons are very penetrating but are not as common in nature. Neutrons have the capability of striking the nucleus of another atom and changing a stable atom into an unstable, and therefore, radioactive one. Neutrons emitted in nuclear reactors are contained in the reactor vessel or shielding and cause the vessel walls to become radioactive. Radioactive elements emit these radiations until they have reached a stable state. For

• some man-made radioac
• tive materials this occurs in a few seconds. For othe
• r elements a small amount can emit ra
• diation f
• or thousands of years. As they break down th
• ey turn into other el
• ements. At g
• round zero, the elements emitting gamma rays and alpha and beta particles ar
• 72-ton hydraulic press
• e Europium, Cesi
• um, Cobalt, Stront
• ium and Plutonium. S
• ources for information about radiation are the American Nuclear Society and the U.S. Nuclear Regulatory Commission.