Activation of Tl,Pb and Bi by 10–160 MeV neutrons: Possible application to the analysis of Bi+

The medium energy intense neutrons (MEIN) available at the Brookhaven Chemistry Linac Irradiation Facility have an energy distribution up to ∼160 MeV an effective neutron flux of ∼1.3×10¹¹ cm⁻²s⁻¹. The present work explores the feasibility of using this facility for the analysis of Tl, Pb and Bi by activation with MEIN. The most sensitive reactions, from a practical standpoint, were found to be Tl (n, xn)²⁰⁰Tl (x=4, 6), Pb (n, xn)^204mPb (x=0, 3, 4. 5) and²⁰⁹Bi (n, 6n)²⁰⁴Bi. The absolute sensitivities attainable with these reactions are 0.1, 0.05 and 0.08 μg of Tl, Pb and Bi respectively, for 1 h irradiation at 1.3×10¹¹ n cm⁻²s⁻¹ with samples counted 2 h after the end of irradiation. The advantages of the method over thermal neutron activation analysis are that all three elements can be assayed at the sub-microgram concentration levels by γ-spectrometry with the help of a simple radiochemical purification and the analytical results can be verified by cross checking via the multiple (n, xn) reaction products. However, interference from Bi in the determination of Pb and from Pb and Bi in the determination of Tl limits its usefulness to the analysis of Bi. This research was sponsored under contract with the United States Department of Energy supported by its Office of Basic Energy Sciences (support for H.L. FINSTON is under Contract no. DE-AC02-76-ER03126).