It is very important to reduce the build-up of CRUD (Chalk River Unidentified Deposit) or to separate the CRUD from the reactor coolant system because major source of ORE (Occupational Radiation Exposure) is coming from the CRUD in the nuclear power plant. Some oxides such as the $Fe_3O_4,\gamma-Fe_2O_3$, or nickel ferrite found in the nuclear power plant are known to show strong ferrimagnetisms. The most important corrosion products for the high temperature filtration of PWR coolants are magnetite and ferrites series materials containing nickel and cobalt. These substances have net magentic moments per unit volume at the low temperature.
Ferromagnetic substances including the ferrites show the property of magnetic saturation, which is very important property to the design and operation of magnetic filters. This implies a new type of magnetic filter and can be used for the separation of CRUD at high temperature and pressure. The rotational motion of the permanent magnet assembly surrounding the vessel produces the moving alternative magnetic field in the vessel. Then the CRUD can be easily separated from the coolant by the moving alternative magnetic force. Separating efficiency depends on the magnetic properties and size of CRUD, flow rates, intensity of magnetic field and temperatures. The temperature also affects especially the separation factor.
This study shows the expected magnetic filter performance to reduce the CRUD concentration and hence why the moving alternative magnetic filter can be recommended as the effective method for the reduction of radiation build-up.
