What defines a Very High Radiation Area, and how are they posted?

• A. An accessible area with a dose of 500 rads in 1 hour at 1 meter; Grave Danger
• B. An accessible area with a dose of 500 rem in 1 hour at 1 meter; Danger
• C. An accessible area with a dose rate of 50 rads in 1 hour at 2 meters; Warning
• D. An area with a dose rate of 200 rads in 2 hours; Grave Danger

Answer: (A)

Very High Radiation Areas are zones where the dose rate is so high that a person could receive a very large dose in a short time. In this material, the threshold is defined as 5 Gy delivered in one hour at a distance of 1 meter from the source (which equals 500 rad). This makes the area extremely hazardous, so access is strictly limited and clearly controlled. The boundary is posted with Grave Danger signage, and only authorized personnel with proper training and dosimetry should enter, following established procedures to minimize exposure. The emphasis is on the combination of an extremely high dose rate and a defined boundary that signals the highest level of warning and restricted access.