Application of φ70 mm Centrifugal Contactors in a Pilot Test of the Total Partitioning Process Using Simulated High‐Level Waste

Abstract

High‐level waste (HLW) produced from reprocessing of the spent nuclear fuel still contains actinides, 90Sr, 137Cs, etc., which presents a significant hazard to the environment. A total‐partitioning process for HLW was developed at the Institute of Nuclear and New Energy Technology (INET), Tsinghua University, China. This process includes the removal of actinides by the TRPO process, the removal of 90Sr by a crown ether strontium extractions (CESE) process, and the removal of 137Cs by ion exchange with potassium titanium hexacyanoferrate. A pilot test was carried out using simulated HLW, where 24 stages of φ70 mm centrifugal contactors were used in the stripping section of the TRPO process for the removal of actinides in the loaded 30% TRPO‐kerosene. The hydraulic tests of the cascade were carried out to determine the operational parameters including both the rotor speed and diameter of the heavy‐phase weir of every stage. A mass‐transfer test of the cascade was carried out. The test results showed that 99.9% of the Nd and 99.9% of the Zr were stripped by 5.5 mol/L HNO3 and 0.6 mol/L H2C2O4, respectively, and 99.6% of the Fe and 99.7% of the Mo were stripped in the whole stripping section. A pilot test of the total partitioning process for 72 h was also performed. In this test, U was added into the simulated HLW after the 66th hour. The test result showed that 99.9% of the Nd, 99.9% of the Zr, and 99.9% of the U were stripped, respectively. The organic phase was recycled after being stripped and scrubbed. During the 72‐h pilot test, 24‐stage φ70 mm centrifugal contactors worked in a stable manner and continuously with no stage failures or interruptions in operation, which demonstrated that these centrifugal contactors were promising for the stripping section of the TRPO process.