What are some examples of applications of constructive uses of radioactive isotopes?

The applications of radiation are numerous. I have listed some below: Here's just a sampling of radioactive materials...and the many ways they improve lives. MEDICAL • Imaging - X-rays, MRI • Nuclear medicine - treatment and imaging • Treatment - Cancer • Sterilization of blood and other items INDUSTRIAL • Density Gauging - how dense ground is for roads, in fluids in pipes • Well logging - Density of ground for wells • Radiography - x-raying pipes, welds, valves for flaws, defects • Non-electrical exit signs HOUSEHOLD • TV - electron excitation of the screens phosphor • Smoke detectors • Long lasting light bulbs • Food irradiation - longer shelf life, less spoilage, longer transport time • Cheap and reliable power source - nuclear power SCIENCE • Chemical tracing in humans, animals for new drug development • Function tracing - how animals and plants work • Analysis of unknown samples by activation • Studying the basic building blocks of nature - cyclotrons and accelerators • ...  more