Radiation shielding with Expanded Polystyrene

The light nuclei in expanded polystyrene or polyurethane scatter incoming hard radiation by Compton scattering and after a few thousand collision events their energy is shared with the plastic as slight warming and neutrons decay to hydrogen in about ten minutes and protons also pick up with an electron and form hydrogen other nuclei just settle as thermals and high energy gamma radiations settles down as heat.

I suppose 2 foot thick I suppose.