Development of a magnetic filter system using permanent magnets for separating radioactive corrosion products from nuclear power plants

Abstract

Radioactive corrosion products generated through the neutron activation of general corrosion products at nuclear power plants are the major source of occupational radiation exposure. Generally, radioactive corrosion products exit in soluble and insoluble forms, and are removed by ion exchangers and purification filters. Most of the insoluble radioactive corrosion products have the characteristic of showing strong ferrimagnetism. With the development and production of permanent magnets (rare earth magnets) capable of generating a much stronger magnetic field than conventional permanent magnets, a new type of magnetic filter that can efficiently separate radioactive corrosion products and eventually reduce radiation exposure to personnel at nuclear power plants is proposed and developed. Magnetic separation by using permanent magnets has certain advantages, such as high flow purification, high pressure and temperature operation, and energy saving. The magnetic separator consists of an inner magnet assembly and an outer magnet assembly, a coolant channel, and a container surrounding the outer magnet assembly. The rotation of the inner and outer permanent magnet assemblies by a driving motor system produces moving and alternating magnetic fields in the coolant channel, which is located between the two magnet assemblies. The particulate in the radioactive corrosion products is separated from the coolant by the alternating magnetic fields as a result of the shifting arrangement of the permanent magnets. This study describes the preliminary experimental results of using different particle sizes and various materials at the different flow rates and rotation velocities of the magnet assemblies. This new magnetic filter performs well in. filtering magnetite, cobalt ferrite, and nickel ferrite from aqueous coolant simulation.