Shielding against high-energy radiation is heavy, no matter what you use. The tenth-thickness (ie, the thickness to attenuate the radiation flux by a factor of

Shielding against high-energy radiation is heavy, no matter what you use. The tenth-thickness (ie, the thickness to attenuate the radiation flux by a factor of 10) of lead is 2 inches. For water and other light materials, its about a foot. Commercial power reactors use lots of concrete, just because its cheaper to make, form, etc. So to go from "rare" to "almost never" you need maybe three or four tenth-thicknesses of shielding material. That's an impractical amount of mass to suspend around your datacenter (rack isles, whatever). Remember too, that you've already got ~30 feet of water equivalent in shielding (the atmosphere).