per cubic foot and more preferably have a density of 250 pounds per cubic foot in another embodiment the core of the doors 12 13 preferably have a density of 313 pounds per cubic foot the core of the doors 12 13 can be formed from a high z material i e a material with a high atomic number and number of protons such as for example and without limitation lead steel and tungsten in another embodiment the core of the doors 12 13 can be formed from boron or lithium based materials which are suitable for capturing neutron particles and byproduct radiation in another embodiment the core of the doors 12 13 can be formed from a metallic aggregate material that can include high z materials such as for example and without limitation iron lead steel and tungsten high z target materials which could be used in the core of the doors 12 13 include but are not limited to copper aluminum titanium and brass the core of the doors 12 13 can include a material having high z aggregates high hydrogen content and or a high macroscopic neutron cross section to capture byproduct radiation such a material can include but is not limited to boron lithium cadmium steel and carbon the core of the doors 12 13 can include any combination of the materials described above and can include a plurality of layers of any combination of the materials described above the outer surface of the doors 12 13 are preferably constructed of carbon steel plate face panels and a minimum u00bd inch thick edge banding along the.