Determination of 129I activities and interference in low level radioactive waste by alkaline fusion coupled with ICP-MS

Isotope of iodine 129I is a fission radionuclide generated by nuclear power plants (NPPs). It is long lived (t1/2 = 15.7 × 106 years) and easily spread through the environment. Concentrations of 129I in low-level radioactive waste (LLRW) can be determined using scaling factors, liquid scintillation counting, inductively coupled plasma mass spectrometry (ICP–MS), neutron activation analysis (NAA), and accelerator mass spectrometry. This study examined three LLRW matrixes: cement solidification, radioactive liquid, and metal powder from a nuclear facility and NPP. After alkaline fusion and solvent extraction, the concentration activity of 129I was determined through ICP–MS analysis. The 129I concentrations in the liquid and metal powder samples revealed using ICP–MS were two to three orders higher than those when using NAA. This difference might be attributable to two sources of interference, molybdenum and cadmium, which form isobaric 129 during 16O collision in ICP–MS. This interference can be eliminated by performing resin purification before ICP–MS analysis. The proposed technique is an economic and reliable method of determining 129I concentration in LLRW.