Number 48 January, 2002

Lab Surveys are Important, Easy

Preventing and finding contamination are two of the most important work practices in any radiation laboratory. Routine surveys allow you to find contamination before it spreads, protect yourself and others from harm due to accidents, and maintain compliance with the rules. ORS inspections are a check on the quality of your surveys. They don't need to be tedious and time consuming; frequent, quick checks of the work area and your hands and clothing may suffice.

Even a quick survey needs to be done correctly for it to be effective. First, check the batteries and replace them if they are low. Second, make sure your survey meter works by measuring a check source or pointing the detector at a source vial or even a radwaste container. Now you are ready to do the survey.

Set the meter to the lowest and most sensitive scale. It is helpful to know the ambient background in the lab -- the reading you get away from any source of radiation -- because it gives you a benchmark. Be patient! Move the detector slowly over the surface without actually touching it. Be alert to small deviations above background; when you notice them, pause over the spot and see if the count rate continues to rise. Don't touch the surface of the detector, and keep it away from sharp objects to avoid breaking the fragile and expensive "window." If you are surveying an area with a high background, such as next to a waste container or in a hood where a process is underway, wipe the surface with a filter paper and measure the filter in a location with a lower background.

In addition to benchtops, look for contamination on centrifuges, incubators where S-35 methionine has been used, vortex mixers, trash cans, the floor at the work area, sink surrounds, the floor or bench around waste containers, the fume hood sash (where you put your hand on it to push it up and down), the rims of stools, and chair backs.

Use the wipe test method if you use tritium; rub the surface with a filter paper and count it in liquid scintillation.

Disposal of Uranyl Acetate

Uranyl acetate is commonly used as an aqueous or mildly acidic solution. While it is radioactive, the specific activity of this off-the-shelf item is so low that it can be used safely with a few basic precautions such as wearing gloves and washing hands. Disposal is easy provided you follow these rules:

• Never mix uranyl acetate with other staining compounds such as lead citrate or other hazardous chemicals. Mixing aqueous uranyl acetate solutions with other heavy metals, solvents or other hazardous chemicals may render it impossible to dispose of legally or economically.
• Straight aqueous solutions may be poured down the drain, flushed with plenty of water.
• Dry uranyl acetate may be given to ORS for disposal as a radioactive waste.