(A) study on the method for improving the removal of radioactive corrosion products using permanent and electric magnets

Abstract

To comply with increasingly strict regulations for protection against radiation exposure, many nuclear power plants have continuously worked to reduce both the radiation sources within power plants and the radiation exposures of operational and maintenance personnel. Many research studies have shown that deposits of irradiated corrosion products on the surfaces of coolant systems are the main cause of occupational radiation exposure in nuclear power plants. These corrosion product deposits on the fuel clad surface are also known to be main factors in the onset of axial offset anomaly (AOA). Hence, there is a great deal of ongoing research into water chemistry and corrosion processes. In the previous study, a magnetic filter using permanent magnets was devised to remove the corrosion products in the coolant stream, by taking advantage of the magnetic properties of the corrosion particles. Experiments using permanent magnets to filter the corrosion products demonstrated a removal efficiency of over 90% for particles above 5㎛. This finding led to the construction of an electromagnetic device, in this study, that causes the metallic particulates to flocculate into larger aggregates of about 5㎛ in diameter, using a novel application of electromagnetic flocculation on radioactive corrosion products. Therefore, the cohesive device was set up before the PMF in order to increase the corrosion product removal rate. Experiments with the novel magnetic filter using permanent and electric magnets showed the highly improved removal rate for corrosion products. The removal efficiency of the PMF for very fine corrosion products was increased from under 70% to over 90%, under most concentrations.