Answer to Question #156 Submitted to "Ask the Experts"

Q

I am a little confused as to the term by-product material. I know that it is "any material produced in a nuclear reactor." I was told that some of the more common radioisotopes may be made this way. The radioisotopes we most commonly use are ³H, ¹⁴C, ³²P, ³³P, and ³⁵S. Are those considered by-product material radioisotopes? If not, how are they produced? How can we tell which radioisotopes are by-product material? Thanks!

A

This is a very good question. Radioactive material is often
characterized as being either by-product material (basically "made" in
a nuclear reactor) or NARM, which stands for "Naturally occurring or
Accelerator-produced Radioactive Material." (Regulations contain more
detailed information, but for the purposes of this explanation, I am
using these general terms.) By-product material includes nuclides such
as ³H, ¹⁴C, ³²P, and ³⁵S. NARM includes naturally occurring nuclides, such as ⁴⁰K and ²²⁶Ra, and nuclides artificially produced in an accelerator, such as ¹¹¹In and ¹²³I.
Charts of radionuclides do not indicate whether the material is
by-product or NARM because in the practice of radiation protection, it
really doesn't matter how something became radioactive; what's
important is its radiological characteristics or properties. The
distinction between by-product and NARM is drawn for regulatory
purposes. The Nuclear Regulatory Commission (NRC), and its predecessor
agency, the Atomic Energy Commission, was established to regulate the
safe use of by-product material. The regulation of NARM has been left
to individual states. There are currently 31 "Agreement States" that
regulate NARM and also have an agreement with the NRC to regulate most
uses of by-product material. Confounding this situation is the fact
that many nuclides can be made in either a reactor or an accelerator.
In fact, a ¹⁰⁹Cd source may be made from either by-product
or NARM, or even a combination of by-product and accelerator-produced
material. The only way to definitively tell which nuclides are
by-product and which are NARM would be to ask how they were made.
Luckily, there are some nuclides, such as ⁵⁷Co, ²²Na, ¹⁸F, ¹²³I, ¹¹¹In, ²⁰¹Tl, and ⁶⁷Ga,
that are always considered to be NARM, and therefore regulated by
states. Probably the quickest way to determine if a particular nuclide
is considered NARM or by-product would be to look up the nuclide in the
NRC's rules. If it is listed, the nuclide is considered to be
by-product because the NRC does not regulate NARM. Conversely, if it is
not listed, it is most likely considered NARM (except for nuclides with
incredibly short half-lives). You could look at some of the tables in
10 CFR Part 30, such as 30.70 Schedule A "Exempt Concentrations" or
30.71 Schedule B "Exempt Quantities" to see lists of nuclides regulated
as by-product material. Another option is to contact the regulatory
agency in your area if you have a question about a particular
radionuclide.



Kathleen A. Allen