The degree of success to be achieved by a Plowshare application may well depend on the amount of radioactivity produced by the nuclear explosion. One method of reducing the soil activation is to emplace shielding material around the explosive package. We conducted a parameter study using Monte Carlo neutronics to determine the optimum moderator-to-absorber atomic ratio and to identify an effective shielding material. With boron as the absorber, we found the most effective ratio to be about 30 ± 5 at.% boron, the remainder being moderator. Many materials containing boron were evaluated; the most effective shielding material was found to be polyethylene borated at ∼30 at.%. A sample Plowshare application was calculated for 15 cm of borated polyethylene, resulting in a reduction of soil activation by a factor of 90 over an unshielded explosive. The total radioactivity was reduced by a factor of only 80 due to tritium production in the shield itself.