I notice that there is a neutron out of this reaction. It is not clear to me if the 2.47MeV refers to the energy of the neutron or the kinetic energy of the tritium, alpha and neutron, or something else altogether.
My thought was this: Since there is a neutron into this reaction, and a neutron out, could you make a chain reaction with it? For a chain reaction you need a process that produces more neutrons out than go into the reaction. There is an alpha particle coming out of this reaction. What if there was a mixture of Lithium 7 and Beryllium. A neutron goes in, splits the Li 7, makes another neutron and an alpha. If that alpha could hit a Beryllium atom, you would get a second neutron from that. (This process is used to make initiators for nukes as described in same doc. listed above).
It makes a little more sense if the arrow is where it should be instead of what looks like a minus sign.
Li-7 + n —> T + He-4 + n - 2.47 MeV
So lithium-7 reacts with a neutron to produce tritium and helium-4 and a (presumably much less energetic) neutron. If I’m not mistaken, the minus sign in front of the 2.47 MeV means this reaction is absorbing energy instead of releasing it. (I think the significance of it in a hydrogen bomb is that it produces tritium that can participate in reactions that do generate energy.)
The reaction absorbs one neutron and produces one neutron. There is no guarantee that the resulting neutron will trigger another rection of this type. So I don’t think there can be a sustained chain reaction with this process alone. Compare that to U-235 which, when struck with a single neutron, splits and produces three neutrons. If each neutron has a 33% or higher chance of splitting another U-235 atom, you can have a sustained chain reaction.
Several things are done to make it more likely that the neutrons from a fissioning Uranium or Plutonium nucleus will cause more fissions: You make the mass large (critical mass), you make it of a good shape (a sphere), you try and make it dense.
Even though the reaction I listed produces only 2 (?) neutrons instead of 3, it seems like you could do some of the same tricks with Lithium as is done with the fissionable heavy elements.
Now that I think about it, I have the title of the thread wrong, no? The remaining products are lighter than Lithium, so it is a fission.
The reaction shown has one neutron in and one out and cannot sustain a chain reaction since at least some of the neutrons will escape. Moreover the atomic mass units balance so there cannot be another neutron coming out. As shown, there are 8 AMUs on each side. But it is a fission reaction since what comes out is smaller than what goes in. Is it really exothermic? Usually, fission of things smaller than iron requires energy.
lists some fusion reactions. The lithium 7 + neutron reaction is listed as endothermic. The lithium 6 + neutron reaction is apparently exothermic, which may be the cause of the confusion.