Georgetown University Medical Center EH&S Newsletter
Susan Martin, DirectorSim Shanks, Radiation Safety Officer
Radiation Safety Training Schedule
This is the first in a series of articles designed to give you the answers to those things you’ve always wondered about, but never quite knew how to ask. This article is about your portable survey meter and how you can best interact with it. Let’s start at the beginning and work to a height of satisfaction that you can personally achieve with your probe.
Your portable survey instrument is divided into two parts. The probe, which you actually use to detect radioactivity, and the base, which contains the electronics and a meter face with which you are able to determine with some precision what your probe is seeing (or more accurately detecting). EH&S will describe how to interpret those detections in another article, so for now let us describe the basics in the best use of your instrument.
1. Look at the calibration sticker mounted on the base. Read the calibration date and calibration due date. All calibrations are performed yearly. If it is past the calibration due date, notify the Radiation Safety Office (RSO) before using your instrument.
2. Ensure that the probe is capable of detecting the isotope that you are using. Isotopes and efficiencies will be listed on the calibration sticker or on the probe. If you have more than one probe, match the listed serial number with the proper probe. If the isotope is not listed, contact the RSO.
3. Check for tightness of cable connections. Your instrument does not like being turned on with loose cable connections. Permanent damage to the instrument will occur!
4. Now check the battery strength. Exactly how you perform this check is dependent on the instrument manufacturer, but they all have the same basic indicating method. Most often there is a battery position located on the on/off switch. The meter face will have a scale indicating battery full strength to the right, and weak battery to the left. Bring the meter to the RSO if the batteries indicate a low reading.
If your meter has passed all the above checks and tests, you are ready to go into action. Turn the on/off knob to the lowest scale multiplication factor possible. Ensure that you are not close to any areas of radioactive storage or disposal. If you have a protective cap on the end of your probe, remove it. Turn on the audio. If you have an F/S switch, ensure it is in the "F" position.
Allow a 15-30 second warm up time. Determine the background by observing the needle movement. Watch for the highest and the lowest reading in a 10 second period. Take the average of the two and record this as your background.
If your meter has a check source, center the probe window in direct contact with the source. Increase the range multiplier setting. Depress the reset switch each time until you obtain a clear reading. This should be within ±20% of the recorded value on the calibration label. If there is a problem, contact the RSO.
Now you are ready to take your probe in hand and begin your search either on yourself, your work area, or throughout the lab and equipment. Remember: your probe is primarily unidirectional. It (the probe face) must be pointed directly at the region of interest to obtain the best results. Keep the probe face 1/2 inch distant from the surface you are scanning. Move your probe at a speed of approximately 1 inch/second. Listen to the audio and watch where you are pointing your probe. Do Not watch the needle movement! The audio will be your guide to contamination. It responds faster than the needle. Simply listen for a sustained increase of clicks that is at least twice the rate of your background.
If an accelerated rate in the clicking is heard, find the highest click rate and hold the probe at this spot and record the counts per minute. Find the center and determine the spread of the contamination. Take a wipe to determine if it is removable. Clean the area as appropriate and record the actions taken to decontaminate the area or object.
One last very important note. Never ever leave your probe exposed and unprotected when it is not in immediate use. Damage can easily occur and repair is costly. Cradle it and cover the probe face with the end cap. Protect it from hard objects. Handle it and the base with loving care.
Biosafety resource page: http://www.orcbs.msu.edu/absa/resource.html
Mad Cow Disease: http://www.hight.net/madcow/
Maryland State Parks: http://www.gacc.com/dnr/
Medscape: http://www.medscape.com/
OSHA: http://www.osha.gov/
safety humor: http://pw1.netcom.com/~aeaton/safetyhumor.htm
EH&S has goggles and protective glasses available for laboratory staff at no charge. Just drop by our office (LM12 PCS).
MSDSs can be acquired by:
· Contacting EH&S via telephone (7-4712) or in writing (LM12 PCS).
· Emailing “MSDS@macpost.odr.georgetown.edu”, and completing the electronic form.
· Accessing public internet sites on the World Wide Web. To locate these sites, go to the EH&S homepage http://macpost.odr.georgetown.edu/ehands/homepg”.
EH&S also wishes to welcome our new office assistant, Jennifer Skoros. Jennifer joined EH&S on September 16, 1997. Jennifer recently moved to the DC area from Bioloxi, Mississippi. She is currently working toward a bachelor’s degree in International Studies.
Or email a message to: thompsonp@odrge.odr.georgetown.edu