Release of oxides of nitrogen in etching Zr+1% Nb tubes in a mixture of nitric and hydrofluoric acids

Abstract

Toxic oxides of nitrogen NO/sub x/ are released on etching fuel-pin tubes made of zirconium alloys, which adversely effect the working conditions and produce air pollution. In this paper, the authors examine the effects of some technological parameters on the release of these oxides during zirconium-alloy tube etching in a mixture of nitric and hydrofluoric acids, and they also examine ways of reducing the yield of NO/sub x/ during the etching. The experiments were performed with a thermostatic teflon reactor. The region that was examined and the variation intervals are shown. The authors used experiment planning with the scheme for a 2/sup 5-1/ fractional factor experiment (FFE). A planning matrix for the 2/sup 5-1/ FFE and the measurement results are presented. It is shown that the release of the NO/sub x/ directly into the gas and the accumulation in the solution vary considerably with the etching conditions. The regression equations and the ranking diagram presented here provide scope for reducing the release of oxides of nitrogen during etching zirconium-alloy tubes.