Monitoring for Radioactivity

 

Uranyl acetate (Electron Microscopy Sciences, cat # 22400) is a low level radioactive material. Its preparation and/or use is routinely monitored and documented in our laboratory. Uranyl acetate solutions are stored in the 4 degree C refrigerator in room 509C. The stock uranyl acetate powder, uranyl acetate waste containers and staining equipment are located in the cupboard below the right side fume hood in room 509C.

 

Materials: Ludlum Model 3 Survey Meter, attached Pancake GM Probe, lab coat and/or disposable plastic apron, double gloves, safety goggles, disposable plastic sleeves, lead shield, uranyl acetate stock powder and uranyl acetate in aqueous solution, record sheets, pen, waste containers for dry waste and liquid waste, paper surgical mask, bench coat paper.

 

Procedure:

 

1.         Wear the lab coat, apron, long plastic sleeves of which the cuffs can be tucked into the double gloves, mask, and safety goggles. Line the floor of the fume hood with two layers of bench coat paper. The top layer can be about 1 foot square, or just big enough to cover your exact work area in the hood.

 

2.         Place the top loading balance or the grid staining equipment (if grid staining) on this top layer of paper. If using the balance, one can also cover the balance with a small sheet of bench coat paper. Just cut out a circular opening for the balance plate. Then add a layer of Parafilm to the plate itself. Cut the Parafilm to match the round shape of the balance plate. Then place the glass draft shield on the balance.

 

3.         Place the lead shield in the fume hood, between you and the work area.

 

4.         Place the Ludlum Survey meter near the work area. Remove the red cover from the pancake probe. Position the probe to face upwards in the meter holder.

 

5.         To operate the survey meter, first, turn ON the on/off toggle located on the upper left corner of the survey meter panel.

 

6.         Turn the sensitivity dial completely clockwise to the x0.1 setting. This is the most sensitive setting possible for this survey meter. This level of sensitivity will detect radioactivity in milliRems/hour. Normal background activity will register below 0.03 milliRems/hour. Observe the middle scale for the readout of activity. See diagram:

7.      Monitor for radioactivity at the end of the work session. Start with one’s gloved hands.   Position one finger at a time about 1 cm away from the probe face for about 5 to 10 seconds in order for the probe to take a good reading of any activity. Do not allow the probe face to touch anything to avoid contaminating it! Always keep objects about 1 cm away. Next, monitor the entire hand and wrist. If one is working very carefully with any radioactive substance, then little or no contamination should be detected on one’s gloved hands. It is imperative to always wear a double layer of gloves to really protect the hands.

 

8.      If the outer pair of gloves is contaminated, then remove them, first from the wrist, turning them inside out towards the fingers. This is a safe way to remove gloves. Place them into a waste bag designated for contamination.

 

9.      Monitor the inner layer of gloves for activity. Hopefully there is no further contamination. If no contamination, then, put on another new pair of gloves. Next, remove the probe from its holder and monitor your arms, chest area, legs, feet. If clean, then go on to the next step.

 

10.  Monitor the entire work area for any activity. Note that activity readings are highest when the uranyl acetate is monitored or any object or surface contaminated with uranyl acetate. We purchase our uranyl acetate from Electron Microscopy Sciences (Fort Washington, PA, cat # 22400). This uranyl acetate is presumably produced from depleted uranium. Its activity measures 0.0068 microCuries/gram. This is low activity but uranyl acetate is categorized as radioactive.  Therefore, it must be handled with utmost care to avoid contaminating oneself and the work area.  The lead shield can only protect oneself from some types of spills.

 

11.  Place all contaminated disposable dry articles, such as weigh paper, bench coat paper, gloves, etc. into the designated waste bag. Rinse all contaminated glassware 3 to 4x with water and pour this contaminated rinse water into the appropriate liquid waste container for uranyl. Place the glassware in the waste bag.

 

12.  Wipe all surfaces clean that may have been exposed to uranyl, e.g., top loading balance, lead shield, etc.  Dispose of these wipes into waste bag. Re-monitor these objects for any residual contamination. If clean, store away. If contaminated, try washing the surfaces again with soapy water. Rinse and then dry. Then take another reading for activity. Hopefully, there will only be background level activity, i.e., less than 0.03 mR/hr.

 

13.  Document any activity or lack of activity on the proper record sheets or notebooks. Also, document how much uranyl acetate powder was taken from the stock bottle and how much remains. Each stock bottle will have its own record sheet posted in room 509C.

 

14.  If a major spill occurs, perhaps on the floor, then one can choose to clean it or not. In any event, the spill should be reported to the Radiation Safety Office, emergency telephone number.

 

15.  If one chooses to mop up the spill, you could throw a bunch of towel papers on it to soak the fluid up. Then wash the area with soapy water, and then rinse. Dispose of the towel papers in waste bag. Then take a reading of the area.  Hopefully the contamination was eliminated. Mark off the area with tape. This will warn others in the lab to avoid the area until Radiation Safety Officers judge the area safe again.

 

16.  Alternatively, get the Chemical Spill Kit provided in the hallways of laboratory buildings. Place spill control pillows and pads on the spill and allow them to absorb the spill. Each spill control pillow will absorb 250 ml of liquid.

 

17.  Dispose of saturated pillows/pads into designated waste bags. Continue to place new pads if the spill is large.  Wash area with soapy water and wipe dry. Take a reading of the area.

 

18.  If uranyl acetate is spilled over a large area of your person, then quickly go to a shower. Remove and discard contaminated clothing while showering. Wash yourself well. When possible call or ask someone to call for medical assistance.

 

19.     When finished with the survey meter, turn the sensitivity dial to OFF. Turn the on/off toggle to OFF.