From abstract: "Comparison of the activity produced by fast neutrons on lead with other activations corroborates the assignment of the 3.2 hr. activity as Pb209, and the assignment of the reaction as capture of fast neutrons. Two different measurements show that the neutrons captured have energies greater than 100 KEV. This average capture cross section for primary neutrons from 7.5 MEV deuterons on a thick target of beryllium is measured as 10[^]-27 ca[^]2."