[nexox]

Note: Lead (and dense materials in general) are not known for their abilities to absorb or slow neutrons - typically shielding is composed of materials composed of a high proportion of light hydrogen atoms, such as water, wax, or plastic.

[russell]

IIRC, trapping the neutrons in water or some similar compound is how the power is extracted from a D-T reaction. However, my ignorance exceeds my curiosity.