ASTM E526-08(2013)

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.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 (τ_{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,1.1 This test method covers procedures for measuring reaction rates by the activation reactions  ⁴⁶Ti(n,p) ⁴⁶Sc + ⁴⁷Ti(n, np)⁴⁶Sc.