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24 May 2012

Answer to Question #3568 Submitted to "Ask the Experts"

Category: Instrumentation and Measurements

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

Which polymer is better between polypropylene, polyethylene-HD, and polyethylene-LD to protect against beta radiation when it's not possible to use methyl polymetacrylate (PMMA, plexiglas, Lucite, etc.)? I have to buy large plastic boxes to keep ³²P radioactive waste in the labs during the period of decay before disposal and PMMA (Perspex, Lucite) boxes are too expensive for this use. I also know that I will have to consider the thickness of any of those materials for their attenuation effect.

I'd recommend you use the plastic polymer that best meets your needs as far as the type of waste and its chemistry, that is, what might be stored, acids, organics, etc. Specifically, should something leak, is it chemically resistant?

Regarding the shielding of the 1.7 MeV (max) energy beta from ³²P, you'll need 800 milligrams per centimeter squared (800 mg cm^-2) of area density thickness to stop all the betas. If the polymer density is about 1 g cm^-3, then you'd need about 0.8 cm (~0.36 inches) thick walls.

You might try some standard-thickness wall container, even if it's just below this wall thickness, as the waste itself will provide some shielding, and the beta spectrum will have an average energy about one-third the maximum energy.

David J. Allard, CHP

Answer posted on 25 March 2004. The information and material posted on this website is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of 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 specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Website. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.