Which best defines the term 'radiological waste'?

The term 'radiological waste' is best defined as any unwanted material that contains radioactive substances. This includes a wide variety of waste types generated from medical, industrial, and research activities involving radioactive materials. Such waste can include contaminated equipment, medical isotopes that have exceeded their useful life, and residual materials from radiation therapy, among others.

Understanding the definition of radiological waste is critical for compliance with safety regulations, as different types of waste may require specific disposal methods and safety measures. Radiological waste must be managed properly to prevent exposure to radiation and to protect both human health and the environment. In contrast, the other options do not capture the essence of what constitutes radiological waste, as they focus on material properties or contexts that do not necessarily involve radioactivity.