5.1 Refer to Guide E844 for the selection, irradiation, and quality control of neutron dosimeters.

5.2 Refer to Practice E261 for a general discussion of the determination of fast-neutron fluence rate with threshold detectors.

5.3 Pure nickel in the form of foil or wire is readily available, and easily handled.

5.4  ⁵⁸Co has a half-life of 70.86 days³ and emits a gamma ray with an energy of 0.8107593-MeV.⁴

5.5 Competing activities ⁶⁵Ni(2.5172 h) and ⁵⁷Ni(35.60 h) are formed by the reactions ⁶⁴Ni(n,γ) ⁶⁵Ni, and ⁵⁸Ni(n,2n)⁵⁷Ni, respectively.

5.6 A second 9.04 h isomer, ^58mCo, is formed that decays to 70.86-day ⁵⁸Co. Loss of ⁵⁸Co and ^58mCo by thermal-neutron burnout will occur in environments^5,6 having thermal fluence rates of 3 × 10¹² cm⁻²·s ⁻¹ and above. Burnout correction factors, R, are plotted as a function of time for several thermal fluxes in Fig. 1. Tabulated values for a continuous irradiation time are provided in Hogg, et al.⁶

5.7 Fig. 2 shows a plot of cross section⁷ versus energy for the fast-neutron reaction ⁵⁸Ni(n,p) ⁵⁸Co. This figure is for illustrative purposes only to indicate the range of response of the ⁵⁸Ni(n,p) reaction. Refer to Guide E1018 for descriptions of recommended tabulated dosimetry cross sections.

FIG. 2 ⁵⁸Ni(n,p)⁵⁸Co Cross SectionNote 1-The data is taken from the Evaluated Nuclear Data File, ENDF/B-VI, rather than the later ENDF/B-VII. This is in accordance with E1018, section 6.1, since the later ENDF/B-VII data files do not include covariance information. For more details see Section H of reference 8.⁸