X-rays originate in the atom's electron layers. Gamma rays usually have a higher energy than X-rays. Both gamma rays and X-rays can penetrate through all body tissues. Thick materials such as lead, steel, or concrete are used for shielding gamma rays and x-rays. Lower energy gamma rays and x-rays come from uranium, thorium, and plutonium.
Neutrons are uncharged particles from the nucleus of the atom.
They may penetrate shielding such as lead. Materials with high hydrogen content, e.g., water or plastic, provide the most effective shielding for neutrons. Neutrons can be produced from a variety of nuclear reactions. Some plutonium materials spontaneously produce neutrons.