[Wonder Warthog]

"There will be a small change in mass between a new one and a depleted one due to energy conversion. It still doesn't change the fact that the main source of joy in a fission explosion is electromagnetic repulsion."

Sorry, but not true. The only place where "electromagnetic repulsion" comes into play is in converting the velocity of the two fission fragment particles into heat as they collide with other atoms in the fuel rods. The SOURCE of that velocity is the mass difference between the original atom and the two new fission product atoms.

[Moonman62]

The only place where "electromagnetic repulsion" comes into play is in converting the velocity of the two fission fragment particles into heat as they collide with other atoms in the fuel rods.

Electromagnetic repulsion is the reason why the fragments have the velocity in the first place. They are moving away from each other.