Method of reprocessing boron carbide irradiated with neutrons from trim or shut-down elements from nuclear reactors

摘要

A method of reprocessing neutron-irradiated contaminated boron carbide, including the steps of:PPdissolving the contaminated boron carbide in a mixture of sulfuric and nitric acids at an elevated temperature, to convert the boron carbide to boric acid, and to form an exhaust gas of nitric oxide and carbon dioxide;P P introducing water or tritiated, boric acid-containing water in liquid form under the surface of the hot acid mixture of the dissolving step, to produce steam;PPsteam distilling the boric acid developed in the dissolving step with the aid of the steam generated in the introducing step, to separate the boric acid from nonvolatile radioactive and nonradioactive corrosion and irradiation products; PP condensing the boric acid-containing steam from the steam distilling s tep to yield boric acid and a condensate containing water or .sup.3 H- containing water;PPevaporating the condensate from the condensing step to dry and calcine the boric acid to form boron oxide and water vapor of .sup.3 H-containing water vapor;P P recycling, in liquid form, the water vapor or .sup.3 H-containing vapor formed in the evaporating step, after condensation, into the water in the introducing step or the mixture of acids in the dissolving step; P Pforming nitric acid by recycling at least part of the first exhaust gas developed in the dissolving step by adding air and water, and producing another exhaust gas containing carbon dioxide; andP Pconverting the boron oxide obtained in the evaporating step to boron carbide.