Antimatter reactor

[YaDinghus]

So, obviously producing antimatter in an accelerator and using this to annihilate with regular matter is beyond uneconomical if you want to produce energy. What I was thinking of was producing positron-decayers, since every electron-positron annihilation would yield two gamma-rays with 511 keV, and the positron itself coming from the nucleus has kinetic energy, too. The question is, since positron-decay happens in atoms with 'too many' protons like Oxygen-15 and Nitrogen-13, how much energy does it take to knock a neutron out of the core, and how reliable is the process? If the reliability and the energy input per atom is below 1MeV plus whatever the positron's kinetic energy is, it should be feasible to devise a power plant from this. I couldn't however find any data on the energy requirements to transform Oxygen-16 into Oxygen-15 or Nitrogen-14 into Nitrogen-13, nor how reliable the processes were. Does anyone here have an idea what those values are, or point me in the right direction?

[Sensei]

44 minutes ago, YaDinghus said:

The question is, since positron-decay happens in atoms with 'too many' protons like Oxygen-15 and Nitrogen-13, how much energy does it take to knock a neutron out of the core, and how reliable is the process?

For every isotope, it's different amount of energy..

In the case of Oxygen-16:

O-16 + 15.6635 MeV -> O-15 + n0

(alpha decay will happen at much lower energy)

 

In the case of Nitrogen-14

N-14 + 10.553 MeV -> N-13 + n0

(proton emission will happen at much lower energy)

46 minutes ago, YaDinghus said:

Does anyone here have an idea what those values are, or point me in the right direction?

Check my signature link how to calculate it..

 

[swansont]

37 minutes ago, YaDinghus said:

So, obviously producing antimatter in an accelerator and using this to annihilate with regular matter is beyond uneconomical if you want to produce energy. What I was thinking of was producing positron-decayers, since every electron-positron annihilation would yield two gamma-rays with 511 keV, and the positron itself coming from the nucleus has kinetic energy, too. The question is, since positron-decay happens in atoms with 'too many' protons like Oxygen-15 and Nitrogen-13, how much energy does it take to knock a neutron out of the core, and how reliable is the process? If the reliability and the energy input per atom is below 1MeV plus whatever the positron's kinetic energy is, it should be feasible to devise a power plant from this. I couldn't however find any data on the energy requirements to transform Oxygen-16 into Oxygen-15 or Nitrogen-14 into Nitrogen-13, nor how reliable the processes were. Does anyone here have an idea what those values are, or point me in the right direction?

Look at the mass difference between the target and the result, e.g. O-16 and O-15 + neutron. E = mc^2

That will tell you the minimum energy you must add. But anything involving an accelerator is ultimately going to be very inefficient and probably not produce net energy. You have to be able to collect the material on the cheap, as we do for fossil fuels, wind and solar (which are all, ultimately, solar), fission, or get fusion technology working.

 

[YaDinghus]

Crap, that's like a whole order of magnitude too much energy to even be theoretically useful...

[Bender]

You don't even have to look at the numbers. You need to give a nucleus enough energy to create a positron, a neutrino, upgrade a proton to a more massive neutron, and upgrade the nucleus to one with a higher mass per baryon...