>>12058293Bruh, the dose makes the poison. Besides, literally any fission reaction is going to necessarily involve neutron flux, which is going to produce unstable isotopes from any elements you put near or into the reactor, which means no matter what you do you're making a shitload of beta and gamma emitters.
Doesn't really matter anyway since all that stuff SHOULD never leave the reactor, except for the propellant, so as long as the elements in your propellant have a very low neutron capture cross section the exhaust should not be significantly radioactive. Hydrogen is really good because it doesn't capture neutrons very well, and if it does it becomes stable deuterium anyway. If deuterium captures a neutron it becomes tritium, which is bad, but deuterium has an extremely small neutron cross section, so it shouldn't be an issue. Oxygen has a non-negligible neutron cross section, but needs to gain several neutrons before it becomes radioactive, and if it does get activated it has a half life of just a few minutes before it decays into a stable isotope again, so not an issue. Carbon has an extremely small neutron cross section, but if it does capture a neutron it can become C-14, which has a half life of thousands of years. Ideally if we're going to use carbon compounds as propellants we'll want to use C-12, as it has the lowest chance of producing any radioactive C-14. Nitrogen has a similar story as oxygen, it'll capture neutrons but decays extremely fast.
So basically you can use hydrogen, water, methane, and ammonia (as well as nitrogen gas, I suppose) in an NTR with no real radiological concerns. Just FYI.
