1.1 ,This test method covers procedures for measuring reaction rates by the activation reaction ⁶³Cu(n,α,) ⁶⁰Co. The cross section for ⁶⁰Co produced in this reaction increases rapidly with neutrons having energies greater than about 4.5 MeV. ⁶⁰Co decays with a half-life of 1925.27 days (±,0.29 days)(1)2 and emits two gamma rays having energies of 1.1732278 and 1.332492 MeV(1). The isotopic content of natural copper is 69.17 ,% ⁶³Cu and 30.83 % ⁶⁵Cu(2). The neutron reaction, ⁶³Cu(n,γ,)⁶⁴Cu, produces a radioactive product that emits gamma rays (1.34577 MeV (E1005)) which might interfere with the counting of the ⁶⁰Co gamma rays.