Radioactive waste is what remains after the use or production of radioactive materials. Modern society uses a variety of products and services that depend on radioactive materials. Uses include the production of household smoke alarms, gauges and monitors used in industry to insure quality control, medicinal and pharmaceutical research, and to generate electricity.

Radioactivity consists of highly energetic subatomic particles emitted by atoms from their cores (nuclei). The handling of radioactive waste is a major challenge for modern society, because exposure to high levels of radiation can kill or cause cancer. However, scientists are unsure whether exposure to low levels of radiation has harmful effects. Everyone is exposed to low doses of radiation from the sun and naturally occurring elements in the earth. Levels to which we are exposed every day are called background levels.

Radioactivity decays (decreases) over time. The rate of decay is measured...