ASTM E523-21e1

5.2?Refer to Practice E261 for a general discussion of the measurement of fast neutron fluence rate with threshold detectors. The general shape of the ⁶³Cu(n,?) ⁶⁰Co cross section is also shown in Fig. 1FIG. 1 ⁶³Cu(n,?)⁶⁰Co Cross Section with EXFOR Experimental Data

5.4?The disadvantages of copper for measuring fast neutron fluence rate are the high reaction apparent threshold of 4.5 MeV, the possible interference from cobalt impurity (>1 ?g/g), the reported possible thermal component of the (n,?) reaction, and the possibly significant cross sections for thermal neutrons for ⁶³Cu and ⁶⁰Co [that is, 4.50(2) and 2.0(2) barns, respectively], 1.1?This test method covers procedures for measuring reaction rates by the activation reaction ⁶³Cu(n,?) 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 5.2711(8)2 years 1.2?With suitable techniques, fission-neutron fluence rates above 10⁹ cm^?2?s^?1 can be determined. The ⁶³Cu(n,?)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more than 15 years before the end of the irradiation should not be relied upon without supporting data from dosimeters withdrawn earlier.

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

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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5?This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.