1B工艺单元中DMHAN作还原剂时Pu的浓缩倍数研究OA

The 1B unit is a critical separation unit in the Purex process,primarily responsible for the efficient separation of uranium(U)and plutonium(Pu).The separation principle is to use a reducing agent to reduce Pu(Ⅳ)to Pu(Ⅲ)that is not easily extracted by 30%TBP-kerosene or n-dodecane,so that Pu(Ⅲ)remains in the aqueous phase,thereby achieving the separation between uranium and plutonium.To elevate the plutonium concentration ratio in the 1B unit,simulation calculations were performed on 4-fold,5-fold,and 6-fold Pu concentration processes using dimethylhydroxylamine(DMHAN)and monomethylhydrazine(MMH)as composite reducing agents.Additionally,a 16-stage counter current stripping experiment for the 6-fold Pu concentration process was conducted at 25℃to verify the simulation results.Simulation results reveal that under the 6-fold Pu concentration condition,when 99.99%of Pu(Ⅳ)in the first-stage organic phase is reduced,the total oxidation rate of Pu(Ⅲ)by nitric acid(HNO3)and nitrous acid(HNO2)in both aqueous and organic phases remains lower than the two-phase reaction rate of trace Pu(Ⅳ)in the organic phase with DMHAN in the aqueous phase,ensuring effective reduction of Pu.Meanwhile,the recovery rates of U and Pu reach 99.999%and 99.995%respectively,with Pu/U separation factor(SFPu/U)of 2.0×104 and U/Pu separation factor(SFU/Pu)of 2.3×105.Countercurrent experimental data confirm that at 6-fold Pu concentration,the U recovery rate is 99.999%,Pu recovery rate is 99.988%,SFPu/U is 7.3×103,and SFU/Pu is 1.4×105,showing good consistency with simulation results.These findings demonstrate that adopting DMHAN-MMH as the reducing agent in the 1B unit can safely raise the Pu concentration ratio from the current 4-fold to 6-fold,providing technical support for optimizing the Purex process.