Please read what i said. What does * shielding materials* have to do with fuel?
A break even DT or even better a burn with DT produces a lot of neutrons, probably well over 1J worth. You need to deal with them in a way that doesn’t produce secondary gammas or activation as much as possible. Typically this is borated concrete. Boron has a large neutron cross section. Boron salts can be added to water and the hydrogen is effective at moderating the 14MeV neutrons so that they get absorbed in shorter distances. You can run the numbers and you can get most of the neutrons absorbed by the boron (or Li ). Thus mittigating activation problems.
