Preparation of uranium oxide powder for nuclear fuel pellet fabrication with uranium peroxide recovered from uranium oxide scraps by using a carbonate-hydrogen peroxide solution

摘要

This work studied a way to reclaim uranium from contaminated UO _2 oxide scraps as a sinterable UO _2 powder for UO _2 fuel pellet fabrication, which included a dissolution of the uranium oxide scraps in a carbonate solution with hydrogen peroxide and a UO _4 precipitation step. Dissolution characteristics of reduced and oxidized uranium oxides were evaluated in a carbonate solution with hydrogen peroxide, and the UO _4 precipitation were confirmed by acidification of uranyl peroxo-carbonate complex solution. An agglomerated UO _4 powder obtained by the dissolution and precipitation of uranium in the carbonate solution could not be pulverized into fine UO _2 powder by the OREOX process, because of submicron-sized individual UO _4 particles forming the agglomerated UO _4 precipitate. The UO _2 powder prepared from the UO _4 precipitate could meet the UO _2 powder specifications for UO _2 fuel pellet fabrication by a series of steps such as dehydration of UO _4 precipitate, reduction, and milling. The sinterability of the reclaimed UO _2 powder for fuel pellet fabrication was improved by adding virgin UO _2 powder in the reclaimed UO _2 powder. A process to reclaim the contaminated uranium scraps as UO _2 fuel powder using a carbonate solution was finally suggested.