Nuclear reaction

No. The materials are not ionized!

There are different types of nuclear reaction. The one you are talking about is the beta decay since it consists of the releasing of electron. The electron released do not come from electric shell of the atom, It come from a neutron.

A neutral neutron will split into a positive proton and negative electron.
The electron produced will be released as the beta particle and the proton produced will make the atomic number of the nucleus increased. So the electron and proton produced is after the reaction and therefore no nucleus is ionized before the reaction.