Fission product removing device

The present invention provides a method of removing fission products thereby capable of maintaining the purity of plutonium recovered from spent fuel rods. Namely, a spent fuel reprocessing method comprises dissolving spent fuels in molten salts, electrolyzing the same to recover uranium or plutonium. In this process, the removing of fission products is conducted by adding a phosphoric acid compound to the molten salts to convert the fission products into solids, and then separating them to reduce the concentration of the fission products. In this case, a portion of the molten salts is drawn out, fission products are removed from the drawn molten salts. Then, they are returned to the previous molten salts. Control for the amount of the drawn salts enables removal of required amount of fission products. In addition, precipitation and formation of fission products can be prevented upon next dissolution of fuels. (I.S.)