There are no free quarks and gluons, even at the very high energy experiments at LHC one measures the effects of the existence of gluons and quarks in the jets. Hadronization happens in nuclear dimensions, not measurable but extrapolated.
in an atomic fission reaction, are free quarks and gluons created, and followed by hadronization, or not? (i.e. is only the residual strong force involved in a fission reaction?)
It is only the residual strong force which is represented by meson exchanges in nuclear models that take part in fission and fusion reactions. Gluon and quark jets appear at much higher energies than the ones in fission reactions.
To understand residual forces it is instructive to understand the corresponding electromagnetic residual forces which give rise to molecules and solids. Even though the atoms are neutral, the orbitals of the electrons leave shapes in space where positive fields from the nucleus are not shielded by the negative orbitals, thus a LEGO like appearance of the atoms allows for attractions between them. In a similar way the color forces are not completely shielded , even though a nucleon is color neutral, because the quarks and gluons within the nucleon have quantum mechanical "orbitals" , and these allow for the build up of the periodic table .
