What defines a "radiological emergency"?

A "radiological emergency" is defined by circumstances that lead to a significant risk of radiation exposure to individuals or the environment. This definition encompasses any incident where radioactive materials are released or where there is a potential for individuals to be exposed to harmful levels of radiation. Such emergencies typically arise from events such as nuclear power plant failures, transportation accidents involving radioactive materials, or even acts of terrorism involving radiological dispersal devices.

The other options, while they may involve some aspect of safety or operational integrity, do not inherently involve radiation risks on the scale or impact of a radiological emergency. A planned power outage, for instance, is a routine measure for various reasons, including maintenance, and does not involve radiation. An accidental exposure during training could be serious but is more controlled and does not necessarily indicate an emergency scenario impacting a broader population. Lastly, a minor equipment malfunction typically does not pose a significant threat and is generally manageable without the implications of radiation exposure. Therefore, the essence of a "radiological emergency" is best captured by the risk it poses for radiation exposure.