Production of 131I, 125I, and 123I Radionuclides and their Separation from Targets

Abstract

Radionuclides can be produced by irradiation of suitable target materials using neutrons from a reactor or using charged particles such as protons (H+), deuterons(2H+) , tritons(3He2+) , helium ions(3He2+), or α particles (4He2+) . These ions are made in the ion source of a cyclotron or an accelerator. The schematics of the components of the reactor and the cyclotron are shown in Figures 6–1 and 6–2. The number of radionuclides formed by irradiation in a reactor or cyclotron depends on several factors: 1. Flux (I) or number of incident particles per unit area per second; 2. Number (n) of stable atoms per unit area in the target and the enrichment factor in a multi-is-otopic target; 3. Cross section (σ, expressed on the basis of lσ = 10−24 cm2) of the particular nuclear reaction used for making the radionuclide; 4. Decay constant of the radionuclide (λ = 0.693/ t 1/2) , in which t 1/2is the half-life of the radionuclide; 5. Time (t) of irradiation in the reactor or cyclotron; and 6. Time of decay (t 1)from the end of irradiation to the time of counting and calibrator.