Which material is suitable for shielding neutron radiation?

Neutron radiation requires specific materials for effective shielding due to the uncharged nature of neutrons, which allows them to penetrate materials differently than charged particles like alpha or beta radiation. Water and concrete are particularly effective for neutron shielding because they contain a high proportion of hydrogen. Hydrogen atoms can effectively slow down (or thermalize) neutrons through elastic collisions, which reduces their energy and increases the likelihood of further interaction with the shielding material.

Water, being rich in hydrogen, is frequently used in nuclear reactors as both a coolant and a neutron moderator, making it an excellent choice for shielding. Likewise, concrete, when designed with sufficient hydrogen-rich aggregates, also serves as a good barrier against neutrons.

In contrast, lead and aluminum are more effective at shielding against gamma and beta radiation but are inadequate against neutrons as they lack sufficient hydrogen content to effectively slow down or absorb neutrons. Paper is not dense enough and lacks the necessary atomic structure to provide any significant shielding against neutron radiation. Thus, materials like concrete and water are the best choices for protection against neutron radiation.