Refer to Guide E 844
Refer to Practice E 261
Note 1—The cross section appropriate for use under this standard is ENBDF/B-VI release 8 library since it contains a covariance matrix. The ENDF/B-VII library has been released, but it does not contain a covariance matrix for this reaction. For dosimetry applications, an uncertainty metric expressed as a covariance matrix is required. See Guide E 1018
The chief advantages of copper for measuring fast-neutron fluence rate are that it has good strength, is easily fabricated, has excellent corrosion resistance, has a melting temperature of 1083°C, and can be obtained pure. The half-life of 60Co is long and its decay scheme is simple and well known.
The disadvantages of copper for measuring fast neutron fluence rate are the high reaction apparent threshold of 5 MeV, the possible interference from cobalt impurity (>1 μg/g), the reported possible thermal component of the (n,α) reaction, and the possibly significant cross sections for thermal neutrons for 63Cu and 60Co (that is 4.5 and 2.0 barns, respectively),(4) which will require burnout corrections at high fluences.
FIG. 1 63Cu(n,α)60Co Cross Section
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 5 MeV. 60Co decays with a half-life of 1925.28 days (0.5 days)
1.2 With suitable techniques, fission-neutron fluence rates above 109 cm2s1 can be determined. The 63Cu(n,)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.
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.