neutrons In a nuke?

We have discovered that heavy elements need an average of more than one neutron for each proton.  But light elements need an average of only one to one.  So when a heavy element is broken into two smaller parts there are more neutrons than are required.  The excess become emitted.  THEY are not converted to energy.  Not at all.

The strength of binding of the REMAINING neutrons and protons increases and that gives off energy.  Some of that energy is used by the neutrons that are released.  Only what is left over after all of this is what is available to be emitted by the device.

Where did you hear that about 11 neutrons?

In a nuclear fission reaction, a neutron goes into a uranium or plutonium atom, making it unstable. It breaks apart into 2 or more smaller atoms. These have less total mass than the original atom plus neutron. The missing mass comes out as energy. It is from the binding energy of the nucleus.

The total number of neutrons doesn't change. Neither does the total number of protons.

This makes zero sense, sorry.

what kind of "nuke" ? most atoms have more than 11 neutrons. In a grain of dust there are trillions of trillions of neutrons.