Analysis of the off-gas from dissolution of nuclear oxide- and carbide fuels in nitric acid
The off-gas composition upon dissolution of different types of non-irradiated nuclear fuels in HNO(3) has been measured and the influence of dissolution parameters such as dissolution temperature, nitric acid molarity, fuel density and composition has been studied. For fast dissolutions, less off-gas (especially NO(2)) is produced than for slow ones. No CO could be measured for the carbide dissolutions and NO is the most important constituent in the off-gas. For oxides and sesquicarbides, the NO(2) is the predominant species. Carbides dissolve much faster than oxides and do not leave any residue, but the solution stays dark and a slight NO(2) and CO(2) evolution continues after the dissolution is complete. A nitric acid concentration of 6 M and temperatures of 80-90 C are the optimum conditions to dissolve fuel materials in a reasonable time with a low nitrogen oxide content in the off-gas. The activation energy calculated from the Arrhenius plot was found to be 43.5 kJ/mol for UC. For UO(2), two values for the activation energy were found: 64.1 kJ/mol if the fuel pellets are pressed from U(3)O(8) powder and 54.8 kJ/mol if the pellets are made from UO(2) powder.
Bibliographic Reference: Article: Radiochimica Acta 51 (1990) pp. 17-22
Record Number: 199110318 / Last updated on: 1994-12-02
Original language: en
Available languages: en