In radiological terminology, what does the term source term mean?

• A. The types and amounts of radionuclides released from a facility or material into the environment.
• B. The name of the release event
• C. The energy of radiation emitted
• D. The detectors used in measurement

Answer: (A)

Source term describes what radionuclides are released, in what quantities, and in what physical form and timing, into the environment. It’s the essential input for dose and environmental transport calculations, specifying which nuclides are released, how much activity or mass is released, the release rate and duration, and the chemical or physical form (for example, gas, aerosol, or soluble). This is why it’s the best answer: it directly defines the radioactive input that drives exposure and risk assessments. The energy of the radiation emitted is a property of the radionuclide itself, not the description of the release; the name of the release event is just an label for the occurrence, and detectors are instruments used to measure radiation, not descriptions of what is released.