What defines a "sealed source" in radiation safety?

A "sealed source" is defined as a radioactive material that is encased to prevent the escape of radiation and contamination. This encapsulation is crucial because it ensures that the radioactive substance does not leak into the environment, thus protecting both human health and the environment from unwanted exposure to radiation.

Sealed sources are designed to contain radioactive isotopes within a robust barrier—usually made of metal or other durable materials—that can withstand physical damage and prevent the release of radioactive particles or contaminating agents. This containment is vital for applications in medical treatments, industrial radiography, calibration of instruments, and research, where controlled use of radiation is necessary without risk of dispersing radioactive materials.

The other options do not accurately capture the essential characteristic of a sealed source. While the secure storage of radioactive material is important, it does not specifically address the containment aspect inherent to the definition of a sealed source. Radiation detection instruments are not classified as sealed sources but rather as tools to measure radiation levels. Temporary storage containers for radioactive waste pertain to different safety protocols and do not embody the concept of sealing radioactive material for regulated applications.