Study on Improvement of Cement Curing Formula of Wet Radioactive Waste

Abstract

In original cement curing formula, curing base material adopts the cement from the specific manufacturer. This increases the difficulty and cost of material procurement and storage in different nuclear power plants, and further leads to the waste of materials. In addition, the leaching resistance of the original formula is poor, and the cumulative leaching fraction of 137Cs is close to the values specified by the national standard. In order to make the practical work more convenient and the disposal of radioactive cement waste safer, the formulation should be improved. In this work, the cement plants around nuclear power plant were investigated, and the cement was selected as the raw material based on the requirements of the nuclear power cement solidifying formula. The coagulant calcium chloride was added to the formula to improve the delay of the concentrated solution formula. Molecular sieve was added to improve the leaching resistance of the original formula. After adjusting the proportion and composition of the formula, inclusion rate of concentrate and the waste inclusion rate for the new formula increased from 51% to 56% and from 35% to 45%, separately. Meanwhile, the compressive strength of cement waste was enhanced up to 10%. The formulation cost reduced, as calculated of the wet waste generated by two megawatt units, the solidified waste disposal cost could be saved as 2.2 million RMB per year. The ability of resisting leaching radionuclides was improved. Specifically, compared with the original formula, the leaching rate and cumulative leaching fraction of 137Cs in the concentrated solution formula was reduced by 25.77% and 56.91%, respectively. In addition, compared with the original formula, the leaching rate and cumulative leaching fraction of 137Cs in the resin formula was reduced by 82.80% and 82.31%, respectively.