Shielding plays an important role at neutron sources for both radiation safety and for minimizing background noise in neutron experiments. Shielding is regularly made from concrete, which contains hydrogen atoms that help to slow down neutrons.
A team at the ESS in Sweden, led by Phillip Bentley, wanted to see if they could improve the neutron shielding properties of a standard concrete. They added extra hydrogen into the concrete in the form of polyethylene (PE) beads and also included boron carbide, another substance known to inhibit the transmission of neutrons.
The concrete mixing was performed by the Danish Technological Institute in Denmark. They determined the best ratios that produced a homogenous distribution of polyethylene throughout the concrete and replaced some of the sand in the composition with B4C as they have similar grain sizes and density.