What is defined as a 'radiation incident'?

A 'radiation incident' is specifically defined as any event that leads to unintended radiation exposure. This definition encompasses situations where an individual may be exposed to radiation unexpectedly, whether in a medical, industrial, or research environment. The critical aspect of this definition is the unintended nature of the exposure, which distinguishes it from planned or controlled scenarios.

In this context, the other choices do not align with the definition of a radiation incident. Planned exposures are typically controlled and monitored, thus not qualifying as incidents. A situation with no risk of exposure clearly indicates safety and lack of any incident occurring. Experiments involving radioactive materials, while they may involve radiation, do not inherently denote an incident unless they lead to unexpected exposure or accidents. Therefore, the recognition of any event that results in unintended exposure is what defines a radiation incident.