Yes, carbon 12 is stable. It’s the same isotope as most of the carbon in your body. You wouldn’t say a brick is unstable because you blows up when you pack it with C4 and detonate it.
Fusing a proton with Boron-11 is equivalent to detonating C4 in a brick. It’s not the breaking of the brick that causes the energy release. The energy release causes the breakage.
Energy releases when you fuse nuclei lighter than iron, or when you fission nuclei heavier than iron.
Therefore I’ll vote “fusion.”
