Po-210: A Byproduct Material?

["Erik F. Shores" <eshores@lanl.gov>]

Good morning Radsafers,

According to 10 CFR 20, byproduct material means:

Any radioactive material (except special nuclear material) yielded in, or 
made radioactive by, exposure to the radiation incident to the process of
producing or utilizing special nuclear material.

In essence, I interpret this to mean isotopes that are fission products,
activation products, or corrosion products in a reactor.

According to 10 CFR 30.71 Schedule B, Po-210 is listed as a byproduct 
material. In trying to understand why this isotope is listed, I've found
the following:

Po-210 is a daughter of Bi-210. Bi-210 is a product of Bi-209(n,gamma).
Bi-209 is a 100% abundant stable isotope. 

My question: Where does Bi-209 come from? In other words, what component
of a reactor, or reactor fuel contains Bi-209 that would ultimately lead
to the production of Po-210?

I would appreciate any assistance in answering my main question
of why Po-210 is considered a byproduct material. 

Best regards,
Erik


--
Erik F. Shores
ESH-12 Radiological Engineering
Los Alamos National Laboratory
eshores@lanl.gov