[FiatLuxDave]

This is true. Back at Fiat Lux when we designed our D-D reactor, we intended it to sit inside a pool of water and borax. Since we didn't need to regenerate tritium, just absorbing the neutrons with boron was the cheapest solution. As far as I know, Borax is the cheapest effective neutron shielding known. We would have liked to have built our vacuum chamber out of purely Al (since Al-28 has a two-minute half-life), but we went with steel for cost reasons.

Unfortunately, we never made enough neutrons to activate anything worthwhile. Nevertheless, it is certainly possible to work around neutrons through design decisions.