含铀难浸碱渣拌酸熟化强化浸出试验研究

针对某核燃料元件公司煅烧后的碱渣进行溶浸处理后，得到铀含量大于1.00%的难浸碱渣，未达到其处理预期要求。为了最大限度浸出和回收铀，对难浸碱渣采用拌硫酸熟化强化手段浸出，重点研究了熟化温度、浓硫酸用量、熟化时间、难浸碱渣粒度对铀浸出率的影响。拌浓硫酸熟化的最佳工艺条件为：难浸碱渣粒度-0.013 mm、熟化温度150 ℃、熟化时间5 h、浓硫酸用量75 mL；在此条件下铀渣计浸出率可达89.98%，难浸碱渣铀含量由1.940%降到0.33%以下。难浸碱渣中物相主要有二氧化硅和氧化铁，其中铀以三氧化铀的形式存在。拌硫酸熟化可以破坏难浸碱渣中以氧化铁为主的包裹结构，进而使包裹的铀被浸出。

Experiment Study on Intensified Leaching of Refractory Alkali Residue Containing Uranium by Acid Ripening

After leaching the alkali residue calcined by a nuclear fuel component company,the refractory alkali residue with uranium content greater than 1.00% was obtained,which did not meet the expected requirements of the treatment.In order to maximize the leaching and recovery of uranium,the refractory alkali residue was leached by means of sulfuric acid mixing and maturation intensification.The effects of maturation temperature,concentrated sulfuric acid dosage,maturation time and particle size of refractory alkali residue on uranium leaching rate were studied emphatically.The optimum conditions of maturation with concentrated sulfuric acid are as follows:the particle size of -0.013 mm for the refractory alkali residue,maturation temperature of 150 ℃,maturation time of 5 h,concentration of concentrated sulfuric acid of 75 mL.Under these conditions,the measured leaching rate of uranium in terms of slag could reach 89.98%,and the uranium content of refractory alkali residue decreases from 1.940% to less than 0.33%.The main phases of refractory alkali slag are silicon dioxide and ferric oxide,in which uranium exists in the form of uranium trioxide.Sulfuric acid mixing can destroy the coating structure of iron oxide in the refractory alkali residue and leach the coated uranium.