Answer to Question #10411 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment/Shielding — Shielding

The following question was answered by an expert in the appropriate field:

Q

I have a 37 kilobecquerel 137Cs source that I use to calibrate/check the operation of my radiation detector. How can I store it safely when it is not in use? Can I use a lead-lined plastic container (pig)? If so, how thick should the lead be?

A
It is typical for a check source such as this to be attached in some manner to the survey meter with no additional shielding. Ludlum, for example, sells a small metal mount that holds the source to the side of the meter and has a small door that closes over the source and also provides a radiation symbol and a warning. Some facilities will mount the source on the detector in other ways (glue, tape, etc.). Having the check source mounted on the instrument assures that you have the check source available for daily constancy checks and to send out with the meter for routine calibration.

The dose rate from an exempt quantity check source such as the one you describe is low enough that it does not have to be kept in a shield when not in use. Some facilities, however, will keep their source in a lead "pig," such as those used for vials of radiopharmaceuticals.

Kennith "Duke" Lovins, MS, CHP
Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 29 August 2012. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.