[ RadSafe ] Disposal of Samarium

Charlie Simmons csimmons at athompsonlaw.com
Tue Jul 1 17:02:21 CDT 2008


This issue recently came up in the context of a natural samarium compound.

First, if the Sm in issue is a non-natural isotope (Sm-151, for example) then it is likely a "byproduct material" subject to regulation by US NRC or Agreement States.  

Second, if "natural" - then it is a "NORM" material. Samarium is a rare earth element that naturally occurs as a combination of five stable and three unstable (radioactive) isotopes.  The radioactive isotopes of samarium include Sm-147 at a natural abundance of 15% and which undergoes alpha decay with a very long (approximately 106 billion year) half-life. The two other radioactive isotopes, Sm-148 at a natural abundance of 11% and half-life of 8,000 trillion years and Sm-149 at an abundance of 14% and half-life of 10,000 trillion years have such exceedingly slow rates of decay that they are 100,000 times less radioactive than Sm-147, and for all practical purposes, are essentially indistinguishable from stable, non-radioactive isotopes.   

The specific activity of Sm-147 is 2.3 E-8 Ci/g (23,000 pCi/g or 851 Bq/g) and at its natural abundance in samarium of 15%, pure samarium would be expected to have a specific activity of 127 Bq/g (3450 pCi/g). 

Natural Sm is not regulated by NRC (or Agreement States) because it is not "source, byproduct or special nuclear" material.  Conceivably, natural Sm could be regulated by a State pursuant to NORM regulations, but that depends on the State and how the regulations are drafted.

The U.S. Department of Transportation regulations governing Class 7 (radioactive) hazardous materials exclude the following materials from the scope of regulation:

"Natural material and ores containing naturally occurring radionuclides which are not intended to be processed for use of these radionuclides, provided the activity concentration of the material does not exceed 10 times the values specified in § 173.436."

49 CFR 173.401(b)(4). The Table in §173.436 identifies 1.0 E1 Bq/g (10 Bq/g) as the activity concentration for exempt material for Sm-147, so natural samarium would be outside the scope of DOT regulations provided it does not exceed 10 x 10 = 100 Bq/g. Depending on the quantity of Sm in your container, and assuming it is, in fact, natural samarium, then it could be subject to DOT regulations - probably as LSA-1 Class 7 (radioactive) material when offered for transportation or transported.

I can offer no opinion on the meaning of the EU RAM symbol - however, I believe the trefoil symbol is universally adopted pursuant to IAEA's TS-R-1 transportation regulations. Please advise if this understanding is incorrect. 


Charlie Simmons  

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf Of Chuck Cooper
Sent: Tuesday, July 01, 2008 5:13 PM
To: radsafe at radlab.nl
Subject: [ RadSafe ] Disposal of Samarium

Good Afternoon,

I recently came across a container of Samarium(-40 mesh, 99% trace metals
basis). It is unopened. It has a radioactive symbol on it. Does anyone have
any information on this material. I know it is a flammable solid. Any
thoughts on disposal would also be appreciated?  Should it go out as RAM?
NORM? Hazardous?

Anybody know what EU RAM symbol means?



David J. McDonough, MS, CHMM
Hazardous Waste Manager
Chemical Hygiene Officer
Temple University
Environmental Health & Radiation Safety
3307 N. Broad Street, Room B-49
Phila. PA 19140

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