NANTeL Radiation Worker Training Practice Test

Discrete radioactive particles are tiny solid bits that carry specific radionuclides. They come from materials that become radioactive and can shed off as particles. In nuclear settings, used nuclear fuel and components that have become activated by neutron exposure—such as corrosion products on reactor surfaces—can form and release small particles containing radionuclides. These particles are a form of contamination that can be inhaled or ingested, which is why they’re considered discrete radioactive particles. Natural background radiation, medical x-ray devices, and household smoke detectors all relate to radiation in different ways but not as discrete particles. Natural background is mainly photons (and some radon in the air), x-ray devices emit photons, and smoke detectors use sealed sources that don’t release particles under normal use. So the source that produces discrete radioactive particles is nuclear fuel and activated corrosion products.