A model can be used to explain and predict real phenomena. A theory is a model designed to explain a number of observed facts. A theory cannot be taken seriously by scientists if it contradicts other theories developed by scientists over the past several hundred years. If even a single new fact is discovered that contradicts what we expect according to a particular theory, then the theory must be revised or discarded. A theory must make predictions that can be checked by observation or experiment.
Radiative energy is energy from nuclear power plants.
A small amount of mass can be turned into a large amount of energy. You can make mass into energy if you can accelerate the mass to the speed of light. It takes a large amount of mass to produce a small amount of energy. One kilogram of mass represents 1 joule of energy. Mass can be turned into energy, but energy cannot be turned back into mass.