Immobilization of simulated medium level alpha liquid waste in alkali-slag-fly ash-calcined kaolin hydroceramics

The alkali-activated slag-fly ash-calcined kaolin hydroceramic (ASFCH) used for solidifying simulated medium level alpha liquid waste (S-MLALW) was prepared by alkaline activation and hydrothermal methods with neodymium and cerium as simulated radioactive nuclides of uranium and plutonium. The phase composition, mechanical strength, corrosion resistance and chemical stability of ASFCH waste forms were investigated. The results show that the main crystalline phase components of ASFCH waste forms are analcime and zeolite NaP1. The introduction of S-MLALW is contributed to the formation of zeolite phases in ASFCH waste form. According to the results of the compressive strength tests, the strength of ASFCH waste form still meets the requirement of cemented waste form when the waste package capacity is 40%. Moreover, the compressive strength of ASFCH waste forms decreases slightly after corrosion by sulphate solution and simulated ground water for 28 d. Also, there are no cracks and fractures appeared on the ASFCH waste forms. It is indicated that ASFCH waste form has a preferable corrosion resistance to sulphate solution and ground water. Besides, the leaching rates of neodymium and cerium are in the range of 10-8-10-6 cm/d, showing that ASFCH waste forms for solidifying S-MLALW also possesses superior chemical stability. ©, 2015, Chinese Ceramic Society. All right reserved.