<p>A nuclear fuel reprocessing plant for processing a spent nuclear fuel with a nitric acid soln. is provided with an electrolytic redn. appts. for reducing the valence of oxidising metal ions consisting of the nuclear fuel dissolved in the nitric acid soln. while their ionic states are kept. To prevent corrosion of a nuclear fuel reprocessing plant for processing a spent nuclear fuel with a nitric acid soln., the valence of oxidisng metal ions consisting of the nuclear fuel dissolved in the nitric acid soln. is reduced while their ionic states are kept and electrolytic reduction is carried out so as to generate NOx gas. The objects are to provide a nuclear fuel reprocessing plant having a corrosion-proofing system, which prevents the corrosion of the appts. without permitting the pptn. of corrosive metal ions in the nitric acid soln. in the form of metal, and corrosion -proofing such a plant.</p>
