Centrifuges with significant amounts of radioactive contamination have been observed during routine radiation safety inspections. While it is not uncommon for centrifuges to become contaminated, it is unusual for them to become so contaminated as to be reading in excess of 1 mRem/hour at one inch from the surface with a survey meter. The following provides guidelines to reduce exposure for researchers who use centrifuges in their procedures with radioactive material.

To minimize exposure from centrifuges contaminated with radioactive material, there are three distinct approaches:

  1. Minimize the release of radioactive material in the centrifuge during the centrifugation of tubes containing radioactive material (use tubes with locking caps),
  2. Routinely decontaminate the centrifuge to remove contamination deposited in the centrifuge during use, and
  3. Provide the appropriate shielding for the centrifuge to minimize exposure from the contamination.

The best method for minimizing exposure is to prevent the centrifuge from becoming contaminated in the first place. While it is difficult to do, you can reduce the amount of contamination by using micro-tubes with screw caps and "O" rings. The cap with the "O" ring reduces leakage from the micro-tube. An alternative to the screw cap is a micro-tube with a locking cap. 

Another approach to minimizing contamination is to obtain a centrifuge which accepts a rotor with a sealed lid. The sealed lid provides containment of the aerosols preventing contamination of the inside of the centrifuge.

Routine decontamination of the centrifuge is the second most reliable means of reducing exposure from contamination in a centrifuge. The centrifuge should be monitored with a radiation survey meter (Use a Geiger counter or Scintillation detector) on a monthly basis and decontaminated if dose rates are greater than 0.1 mRem/hour at one inch from the surface. The wipe test method should be used as well. This may involve removing the rotor to clean and soak it to remove the contamination.

If all else fails, you can shield the centrifuge to reduce exposure to researchers. In most cases simply closing the lid on the centrifuge will significantly reduce exposure from the contamination. However, when the lid is up additional shielding will be necessary. If your laboratory is working with beta emitters such as 32P you can place a Plexiglas shield in front of the centrifuge. For gamma and x-ray emitters such as 125I and 51Cr you will need to place lead shielding in front of the centrifuge.

Researchers are encouraged to use the prevention and decontamination methods over the shielding method. While shielding can be effective, it allows the problem to become worse.