Can anyone help me with an approximate answer to this or point me in the direction of avenues to get an answer to this? This has practical applications and is potentially worrying. Roughly how much (or how many atoms) of cobalt-59 exposed to the average neutron radiation at in-flight altitudes (about 11,000 meters) -- neutron radiation makes up about half of the in-flight radiation dose due to cosmic radiation -- will be transmuted into Cobalt-60 via neutron capture over a given amount of time? Alternatively, and maybe this would be easier to answer, roughly what duration or range of time would it take for such in-flight neutron radiation to transmute one atom of cobalt-59 into one atom of cobalt-60? I have a plain chrome-cobalt dental crown (composed mainly of cobalt-59) that is not covered with any porcelain or ceramic, and so I am concerned about this. Thanks in advance for any approximate answers, guesses, thoughts, pointing to other sources, etc.