Significance and Use
5.1 Refer to Guide E844 for the selection, irradiation, and quality control of neutron dosimeters.
5.2 Refer to Test Method E261 for a general discussion of the determination of fast-neutron fluence rate with threshold detectors.
5.3 Titanium has good physical strength, is easily fabricated, has excellent corrosion resistance, has a melting temperature of 1675°C, and can be obtained with satisfactory purity.
5.4 46Sc has a half-life of 83.79 days.3 The  46Sc decay4 emits a 0.8893 MeV gamma 99.984 % of the time and a second gamma with an energy of 1.1205 MeV 99.987 % of the time.
5.5 The isotopic content of natural titanium recommended for  46Ti is 8.25 %.3
5.6 The radioactive products of the neutron reactions   47Ti(n,p)47Sc (τ1/2 = 3.3492 d) and   48Ti(n,p)48Sc (τ1/2 = 43.67 h), might interfere with the analysis of  46Sc.
5.7 Contaminant activities (for example,   65Zn and  182Ta) might interfere with the analysis of  46Sc. See Sections 7.1.2 and 7.1.3 for more details on the  182Ta and  65Zn interference.
5.8 46Ti and  46Sc have cross sections for thermal neutrons of 0.59 and 8 barns, respectively5; therefore, when an irradiation exceeds a thermal-neutron fluence greater than about 2 × 1021 cm–2, provisions should be made to either use a thermal-neutron shield to prevent burn-up of   46Sc or measure the thermal-neutron fluence rate and calculate the burn-up.
5.9 Fig. 1 shows a plot of cross section versus neutron energy for the fast-neutron reactions of titanium which produce   46Sc [that is, NatTi(n,X)46Sc]. Included in the plot is the  46Ti(n,p) reaction6 and the   47Ti(n,np) contribution to the  46Sc production,7 normalized (at 14.7 MeV)8 per   46Ti atom. This figure is for illustrative purposes only to indicate the range of response of the  46Ti(n,p) reaction. Refer to Guide E1018 for descriptions of recommended tabulated dosimetry cross sections.
Scope
1.1 This test method covers procedures for measuring reaction rates by the activation reactions  46Ti(n,p) 46Sc + 47Ti(n, np)46Sc.
1.2 The reaction is useful for measuring neutrons with energies above approximately 4.4 MeV and for irradiation times up to about 250 days (for longer irradiations, see Practice E261).
1.3 With suitable techniques, fission-neutron fluence rates above 109 cm–2·s–1 can be determined. However, in the presence of a high thermal-neutron fluence rate, 46Sc depletion should be investigated.
1.4 Detailed procedures for other fast-neutron detectors are referenced in Practice E261.
