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