Originally Posted by
BoilerUP
Would not the radioactive emissions of a reactor engine be fairly straightforward to track?
A perfectly designed and functioning aircraft engine would not emit any nuclear core material at all, so no high grade contamination. It would be hard to carry much shielding so such an engine would emit some radiation but that's short range in the atmosphere, I think it would be hard to detect from a distance unless you had a space sensor staring at the object... might work for tracking, at great expense, but probably not detection.
The airflow through the engine would get massively neutron irradiated in the core, which would generate radioactive isotopes of air component atoms and any air particulates. That would be detectable after the fact, by ground monitoring or airborne sampling. But that would not be anything close to real time.