1.1 This test method covers procedures for measuring reaction rates by the activation reaction ⁶³Cu(n,alpha)⁶⁰Co. The cross section for ⁶⁰Co produced in this reaction increases rapidly with neutrons having energies greater than about 5 MeV. ⁶⁰Co decays with a half-life of 1925.1 days (± 0.5 days) and emits two gamma rays having energies of 1.1732 and 1.3325 MeV³. The isotopic content of natural copper is 69.17 % ⁶³Cu and 30.83 % ⁶⁵Cu. The neutron reaction, ⁶³Cu(n,γ)⁶⁴Cu, produces a radioactive product that emits gamma rays which might interfere with the counting of the ⁶⁰Co gamma rays.

1.2 With suitable techniques, fission-neutron fluence rates above 10⁹ cm^-2.s^-1 can be determined. The ⁶³Cu(n,alpha)⁶⁰Co reaction can be used to determine fast-neutron fluences for irradiation times up to about 15 years (for longer irradiations, see Practice E 261).

1.3 Detailed procedures for other fast-neutron detectors are referenced in Practice E 261.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.