Measurement of inclusive photonuclear (γ,n) reaction cross section for ¹²⁹I

Abstract
Long-life non-γ emitting radioactive wastes such as ¹²⁹I and ¹⁴C are produced from nuclear waste facilities. The photonuclear reaction is supposed to be usable for measuring the quantity of such nuclides without destruction of waste drum. Photonuclear products of ¹²⁸I and ¹³C emit gamma rays and their radiation can be easily detected by a Ge detector. In this study, the inclusive photonuclear reaction cross section of ¹²⁹I(γ,n) ¹²⁸I was measured by the use of bremsstrahlung photons from 30-MeV electron LINAC. The amount of produced ¹²⁸I was measured with an HPGe gamma-ray spectrometer. Experiments were analyzed for both (γ,n) and accompanying (n,γ) reactions. Flux calculations were performed by EGS and MCNP codes. The measured average activation cross section of ¹²⁹I(γ,n) ¹²⁸I is 0.096 ± 0.005 barn on the basis of ¹⁹⁷Au(γ,n) reaction value. The measured value agrees with the evaluated (IAEA photonuclear data library) cross section within a deviation of 17%. The cross section is usable for non-destructive measurement of the amount of ¹²⁹I in radioactive waste.