Significance and Use
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 days and emits a gamma ray with an energy of 0.8107593-MeV.
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, 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.
5.7 Fig. 2 shows a plot of cross section 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 Section
—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.
1.1 This test method covers procedures for measuring reaction rates by the activation reaction 58Ni(n,p)58Co.
—The burnup corrections were computed using effective burn-up cross sections of 1650 b for 58Co(n,γ) and 1.4E5 b for 58mCo(n,γ).
FIG. 1 R Correction Values as a Function of Irradiation Time and Neutron Flux
1.2 This activation reaction is useful for measuring neutrons with energies above approximately 2.1 MeV and for irradiation times up to about 200 days in the absence of high thermal neutron fluence rates (for longer irradiations, see Practice E261).
1.3 With suitable techniques fission-neutron fluence rates densities above 107 cm−2·s −1 can be determined.
1.4 Detailed procedures for other fast-neutron detectors are referenced in Practice E261.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
E170 Terminology Relating to Radiation Measurements and Dosimetry
E181 Test Methods for Detector Calibration and Analysis of Radionuclides
E261 Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques
E844 Guide for Sensor Set Design and Irradiation for Reactor Surveillance, E 706 (IIC)
E944 Guide for Application of Neutron Spectrum Adjustment Methods in Reactor Surveillance, E 706 (IIA)
E1005 Test Method for Application and Analysis of Radiometric Monitors for Reactor Vessel Surveillance, E 706 (IIIA)
E1018 Guide for Application of ASTM Evaluated Cross Section Data File, Matrix E706 (IIB)
activation; activation reaction; cross section; dosimetry; fast-neutron monitor; neutron metrology; nickel; pressure vessel surveillance; reaction rate;
ICS Number Code 17.240 (Radiation measurements); 27.120.30 (Fissile materials and nuclear fuel technology)
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