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Hyun, Sung-Hee

Kim, Byoungkwan

Ma, Hyun-Min

Um, Wooyong

Walkley, Brant

Yeo, Tae-min

English

Engineering Conferences International

IMPACT OF CALCIUM HYDROXIDE ON PHYSICAL CHARACTERISTICS AND LEACHING STABILITY OF METAKAOLIN-BASED GEOPOLYMER WASTE FORM CONTAINING RADIOACTIVE BORATE WASTE  Byoungkwan Kim, Division of Advanced Nuclear Engineering (DANE), POSTECH, South Korea kwan928@postech.ac.kr Hyun-Min Ma, Division of Advanced Nuclear Engineering (DANE), POSTECH, South Korea Brant Walkley, Department of Chemical and Biological Engineering, The University of Sheffield, United Kingdom  Tae-min Yeo, Graduate Institute of Ferrous Technology (GIFT), POSTECH, South Korea Sung-Hee Hyun, Graduate Institute of Ferrous Technology (GIFT), POSTECH, South Korea Wooyong Um*, Division of Advanced Nuclear Engineering (DANE), POSTECH, South Korea   Keywords: radioactive waste, borate waste, waste form, geopolymer, calcium hydroxide  Immobilization of radioactive borate waste using metakaolin-based geopolymer is beneficial in terms of waste loading, physical characteristics, and leaching stability. However, boron in borate waste reacts with silicon in geopolymer resulting in the setting retardation and low compressive strength. Herein, calcium hydroxide was used to enhance the durability of geopolymer waste form containing 30 wt% borate waste. The CaO:K2O:Al2O3:SiO2:H2O molar ratio of geopolymer waste form was x:1:1:2.8:10 (x = 0, 0.25, 0.50. 0.75, and 1.0). All geopolymers containing Ca showed higher 7-day compressive strength than geopolymer without Ca (5 ± 1) and the highest compressive strength was achieved in geopolymer with Ca/Al ratio of 0.25 (14 ± 2 MPa). As a result of long-term leaching test for 100 d, the leachability index of boron increased from 7.5 to 8.6 in geopolymer with Ca/Al ratio of 0.25 and controlling leaching mechanism was diffusion. The appropriate dosage of Ca formed the calcium silicate aluminate hydrate gel together with geopolymer and accelerated the geopolymerization reaction, resulting in the enhanced compressive strength and leaching stability of geopolymer waste form. This study provides insight into the geopolymer solidification process for the borate waste and can increase the understandings of the impact of Ca on the geopolymer waste form containing borate waste.     this work was supported by the Institute for Korea Spent Nuclear Fuel (iKSNF) and Korea Foundation of Nuclear Safety(KOFONS) grant funded by the Korea government(Nuclear Safety and Security Commission, NSSC) (No. 2109092-0323-CG100).     

Impact of calcium hydroxide on physical characteristics and leaching stability of metakaolin-based geopolymer waste form containing radioactive borate waste

https://dc.engconfintl.org/cgi/viewcontent.cgi?filename=0&article=1024&context=geopolymers2023&type=additional

Impact of calcium hydroxide on physical characteristics and leaching stability of metakaolin-based geopolymer waste form containing radioactive borate waste

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Engineering Conferences International