For surfaces and other objects (e.g., lab equipment) in a radionuclide laboratory, the contamination limits are as follows:
- For removable contamination, the action level is 200 cpm/100 cm2. This level assumes that the counting efficiency of the instrument used to count the wipe is at least 10% (see INSTRUMENTATION). If the efficiency is less than 10%, the maximum acceptable contamination level is 2000 dpm/100 cm2. This maximum level may be increased by a factor of 10 for radionuclides with half-lives less than 24 hours.
- For fixed (non-removable) contamination, the following restrictions apply:
- Following extensive decontamination efforts, fixed contamination must not give rise to a radiation exposure rate greater than 2 mR/hr at 30 cm from the contaminated area. Shielding may be utilized to meet this requirement provided that such shielding is labeled and secured to prevent inadvertent removal.
- Areas of fixed contamination must be covered with a durable material (4 mil plastic sheeting, if shielding is not needed, securely taped in place) to prevent the gradual release of the contamination.
- The area must be plainly labeled as a contaminated area. This labeling should include the radionuclide, exposure rate at 30 cm, and date of exposure rate measurement.
- The RSO must be immediately notified to determine the ultimate solution for areas of fixed contamination.
- Any shielding and/or labeling must not be removed until the measured radiation levels are equivalent to background (e.g., decayed for ten half-lives and surveyed).
Contaminated lab coats, clothing, or other personal items must be decontaminated, held for radioactive decay (if practical), or disposed as radioactive waste. The RSO must be contacted if any such contamination is discovered.
If the skin of an individual is contaminated, decontamination should be initiated in accordance with the guidelines specified in #3 of this section. If the contamination is not immediately removable, the RSO should be notified.
External radiation exposure rates, which arise from radiation sources (i.e., not from contamination) and may result in whole body exposures, must generally be maintained As Low As Reasonably Achievable (ALARA). The maximum upper limit for measured radiation exposure rates are provided below. If the exposure rates cannot be reduced to these limits, the RSO should be contacted.
- For restricted areas (i.e., authorized laboratories), the exposure rates must not generally exceed 2 mR/hr at 30 cm from any source of radiation not currently in use (i.e., in storage).
- For unrestricted areas (i.e., outside of authorized laboratories), the exposure rates must generally be equivalent to background. If this level cannot be achieved, contact the RSO.
