When is an area required to be posted as a contamination area?

A contamination area must be designated when the level of detectable contamination exceeds certain thresholds established to protect workers and the environment. The correct choice indicates that an area should be marked as a contamination area if there are more than 1,000 disintegrations per minute (DPM) per 100 square centimeters for beta and gamma radiation. This criterion is in place because it reflects a level of contamination that can potentially pose a health risk to personnel who may come into contact with surfaces in that area.

The 1,000 DPM/100 cm² threshold is a recognized standard that ensures safety measures are implemented to prevent the spread of radioactive material and to protect individuals from possible exposure. Assessing contamination levels helps in maintaining safe working conditions and is a critical part of radiation safety protocols.

The other options mentioned relate to exposure rates or counts that don’t define direct contamination levels in the same manner. For example, the exposure rates and other counting measures do not reflect the presence of radioactive material on surfaces, which is the key factor for establishing a contamination area. Rather, the focus is strictly on the activity of radioactive particles on surfaces, which makes the threshold of 1,000 DPM/100 cm² a vital marker for contamination designation.