Measurement of the Photonuclear (γ, n) Reaction Cross Section for ~(129)I Using Bremsstrahlung Photons

摘要

Nuclear waste contains a significant amount of long-lived non-gamma-emitting nuclei such as ~(129)I and ~(14)C. A method of nondestructive detection for monitoring long-lived waste products is proposed as an application of the (γ, n) reaction. This method is useful for surveying long-lived "difficult-to-measure" nuclides, e.g., ~(129)I. Iodine-128 produced from the reaction of ~(129)I(γ,n)~(128)I emits gamma rays that can easily be measured by a gamma-ray counter. We measured the inclusive photonuclear ~(129)I(γ, n)~(128)I reaction cross section induced by bremsstrahlung photons. The photons were produced at a Ta target bombarded by 30-MeV electrons from a linear accelerator. The intensity of the slow neutrons was considered in the reactions of ~(127)I(n, γ)~(128)I and ~(129)I(n, γ)~(130)I. The activity of ~(128)I was measured by a high-purity germanium spectrometer. The gamma-ray flux and the neutron flux were calculated using the EGS and MCNP codes, respectively. The average activation cross section of the ~(129)I(γ, n)~(128)I reaction had a 12% deviation from the evaluated International Atomic Energy Agency photonuclear data.