1.1This 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.

1.2With suitable techniques, fission-neutron fluence rates above 10⁹ cm⁻²·s⁻¹ can be determined. The ⁶³Cu(n,α)⁶⁰Co reaction can be used to determine fast-neutron fluences for irradiation times up to about 15 years, provided that the analysis methods described in Practice E261 are followed. If dosimeters are analyzed after irradiation periods longer than 15 years, the information inferred about the fluence during irradiation periods more than 15 years before the end of the irradiation should not be relied upon without supporting data from dosimeters withdrawn earlier.

1.3Detailed procedures for other fast-neutron detectors are referenced in Practice E261.

1.4This 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.