Key Radioactive Elements

Radioactivity is a tool when understood and a threat when ignored:

• Uranium-235 fuels nuclear reactors and weapons; the critical mass for a bomb is about 52 kg
• Plutonium-239 is produced in reactors and used in both power generation and nuclear warheads
• Carbon-14 enables radiocarbon dating of archaeological samples up to about 50,000 years old
• Iodine-131 treats thyroid cancer because the thyroid naturally absorbs iodine, concentrating the radiation exactly where it is needed
• Cobalt-60 is used in radiation therapy to destroy cancer cells and in food irradiation to kill bacteria