Not really answerable with a number, but here's some light reading on the process of electron probing of neutrons: https://en.wikipedia.org/wiki/Deep_inelastic_scattering Here's a discussion: https://www.quora.com/What-would-happen-if-a-neutron-and-an-electron-hit-each-other
I don't know what 'at the electron level' means to you. Fission and fusion are nuclear processes and occur in the nucleus. Processes that occur with electrons are generally called chemical.