DEVELOPMENT OF FUEL DEBRIS TREATMENT TECHNOLOGY BY THE FLUORINATION METHOD

摘要

The past severe accidents have occurred at severalnuclear power plants (TMI-2, Chernobyl, and FukushimaDaiichi), and fuel debris was generated. As fuel debriscontains many kinds of materials such as fissile,radioactive, and exothermic nuclides (or elements),criticality control, shielding, cooling and deteriorationprevention are necessary for the management of fueldebris. The accountancy of nuclear materials (Pu and U)is also important. To manage these issues, we have beendeveloping the fuel debris treatment technology usingfluorination method. This technology mainly consists ofthree processes: (1) fluorination (the separation of U andPu fluorides from non-volatile impurities), (2) recovery ofU and Pu fluorides, and (3) oxide conversion. As manyimpurities are co-existed in fuel debris, rough separationof these impurities is effective for volume reduction ofnuclear waste and precise accountancy of Pu and U.Moreover, converted oxides are stable, easy to bedissolved by nitric acid, and suitable for long termstorage, reprocessing, vitrification, and disposal. Theauthors conducted fluorination experiments using severalkinds of simulated debris to show the applicability of thistechnology to fuel debris treatment, and discussed aboutthese results in this paper.