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Structural Shielding: Primary and Secondary Barriers
Primary barriers take the useful beam: 1/16 inch lead, 7 feet high. Secondary barriers, including the control booth, stop scatter and leakage: 1/32 inch.
Primary and secondary
Protective barriers are lead or other material built into walls, floors and doors to protect people outside the x-ray room. A primary barrier is any surface the useful beam can strike, such as the wall behind the upright Bucky and the floor under the table. It is typically 1/16 inch (1.6 mm) of lead and extends 7 feet (2.1 m) up from the floor. A secondary barrier is reached only by scatter and leakage radiation. It is typically 1/32 inch (0.8 mm) of lead and runs from the top of the primary barrier to the ceiling, overlapping it by about 1/2 inch. Concrete, brick or gypsum board can replace lead in an equivalent thickness.