How is it that nuclear fusion releases more energy than nuclear fission?

Question

I’m trying to understand why there is more energy output (3-4 times) with nuclear fusion when fission of U-235 releases 200 MeV and D-T fusion only below 20 MeV (14.9 / 17.6).

In: 0

Answer 1

So, you’re right that the energy *per event* is greater in nuclear fission. That much is clear.

But what we’re really more interested in is the energy [*per unit mass*](http://www4.hcmut.edu.vn/~huynhqlinh/olympicvl/tailieu/physlink_askexpert/ae534.cfm.htm) — in this case, per nucleon (proton or neutron). Pound for pound, nuclear fusion releases about 6.2 MeV per reacting nucleon, while fission only releases 0.7 MeV. Your mass goes a lot farther with fusion, and the raw materials are relatively easier to come by.