Radiocarbon creation mechanisms

[bbh2808]

Hello all!

I have a question about the way or ways in which C-14 can be created:

From the background research I have done, I see that high energy neutrons colliding with nitrogen atoms give rise to C-14. I also looked a little bit into beta+ decay. I was curious as to whether or not beta+ decay could also create radiocarbon?

From what I'm able to gather, nuclear testing also created C-14 from nitrogen. I was curious if the energy released by the nuclear detonation alone created the C-14 or if the presence of free neutrons in the atomic blast was necessary for C-14 creation?

 

[Nyme]

C-14 production from beta plus decay would happen from nitrogen-14, which is a stable nucleus, so C-14 won't be produced by beta + decay, at least not directly by it.

In nuclear detonations, the neutrons are necessary to induce the
n + N-14 --> C-12 + H-1
reaction. If you had a neutron-free nuclear weapon, whose energy would be released only by charged particles and medium-energy photons (primarily x-rays), C-14 would not be produced, nor any other nuclear reaction would take place outside the weapon.

 

[bbh2808]

Right on. So the presence of free, high-energy neutrons is absolutely necessary for the nuclear reaction which creates C-14 then?

I was thinking that meteor impacts such as the siberian impact in 1908 which released 15 megatons of energy could create C-14, but I guess in lieu of free neutrons in the blast, that would not occur?

 

[Nyme]

Yep, the neutrons are necessary. Meteor impacts, even when on such a large scale, release the energy in a different way and no free neutrons are emitted. In an impact event, the kinetic energy of the meteorite is converted to heat. It might look like a nuclear explosion and have same magnitude of energy release, but would not actually change any nuclei, and as such, not release any neutrons.