I work for a particle accelerator, and I can confirm you that our beam dump uses polyethylene for neutron shielding: https://www.sciencedirect.com/science/artic

I work for a particle accelerator, and I can confirm you that our beam dump uses polyethylene for neutron shielding: https://www.sciencedirect.com/science/article/pii/S0920379618301029 https://www.sciencedirect.com/science/article/pii/S092037961...