What can effectively stop neutron radiation?

Neutron radiation can effectively be stopped by materials that contain a significant amount of hydrogen or other low atomic mass elements, which are able to slow down and scatter neutrons. Concrete, being a dense material that often includes hydrogen in the form of water or organic compounds, provides a good medium for neutron attenuation. The hydrogen atoms in concrete interact with the neutrons, absorbing their energy and thereby reducing their intensity. This interaction leads to a much higher chance of neutrons being captured or losing their energy.

In contrast, while lead is very effective at stopping gamma radiation due to its high atomic number, it is not particularly effective against neutrons. Similarly, other options such as a sheet of paper or glass do not have sufficient hydrogen content or density to significantly mitigate neutron radiation, making concrete the best choice among the options provided. Understanding the interaction of neutron radiation with different materials is critical for ensuring safety and effective shielding in environments where neutron sources are present.