Which of the following would be considered a secondary barrier? (Select three)

A secondary barrier is designed to protect personnel from scatter radiation and is typically positioned to reduce exposure during radiographic procedures. In the provided options, the control booth and walls over 7 feet tall qualify as secondary barriers due to their purpose of providing a safety buffer between radiation sources and personnel.

The control booth is specifically designed to protect technologists from receiving radiation during imaging procedures while allowing them to control the equipment safely. Walls over 7 feet tall can also function as secondary barriers if they meet certain specifications, serving to shield individuals from scattered radiation.

A lead apron, on the other hand, serves as a personal protective device rather than a structural barrier. It provides localized protection for the individual wearing it during an examination but does not qualify as a barrier in the context of the entire facility's structural safety measures.

Thus, the combination of walls over 7 feet tall, the control booth, and enclosed barriers qualifies as a selection of secondary barriers, emphasizing their role in protecting individuals from radiation scatter.