Fuel decontaminating system

Purpose: To effectively and uniformly decontaminate the surface of fuel assemblies and fuel rods without dismantling the working and spent fuel assemblies. Method: A fuel assembly is immersed in a phosphate (Na2PO4) solution as an electrolytic solution and decontamination by electrolytic polishing is conducted to the surface of fuel rods by applying a DC voltage while using the fuel assembly as an anode and a fuel container as a cathode. About from 20 to 80 % of phosphoric acid concentration is effective. Claddings deposited to the surface of the fuel rods are dissolved into the electrolytic solution and removed through clean-up filters. In this way, claddings can be removed substantially uniformly and a decontaminating effect greater than about 70 % can be expected also for the fuel rods to the inside of the fuel assembly. As compared with a conventional jet spray or supersonic wave decontamination, the decontaminating effect is higher and the fuels at the inside of the assembly can also be decontaminated, as well as the radioactive exposure to operators in a re-processing plant can be reduced. (Kamimura, M.)